{"id":1869,"date":"2026-10-08T18:13:12","date_gmt":"2026-10-08T09:13:12","guid":{"rendered":"https:\/\/www.nibb.ac.jp\/plantdic\/blog\/?p=1869"},"modified":"2026-10-09T18:00:02","modified_gmt":"2026-10-09T09:00:02","slug":"%e3%82%a6%e3%82%ad%e3%82%af%e3%82%b5%e4%ba%9c%e7%a7%91-%e3%82%b5%e3%83%88%e3%82%a4%e3%83%a2%e7%a7%91%e3%80%81%e3%82%aa%e3%83%a2%e3%83%80%e3%82%ab%e7%9b%ae-lemnoideae-araceae-alismatales","status":"publish","type":"post","link":"http:\/\/www.nibb.ac.jp\/plantdic\/blog\/?p=1869","title":{"rendered":"\u30a6\u30ad\u30af\u30b5\u4e9c\u79d1 (\u30b5\u30c8\u30a4\u30e2\u79d1\u3001\u30aa\u30e2\u30c0\u30ab\u76ee) Lemnoideae (Araceae, Alismatales)<\/strong>"},"content":{"rendered":"\n

\u30a6\u30ad\u30af\u30b5\u4e9c\u79d1<\/strong><\/p>\n\n\n\n

\u30a6\u30ad\u30af\u30b5\u4e9c\u79d1\u306e\u690d\u7269\u306f\u3001\u4ed6\u306e\u307b\u3068\u3093\u3069\u306e\u9678\u4e0a\u690d\u7269\u3068\u306f\u7570\u306a\u308b\u30dc\u30c7\u30a3\u30fc\u30d7\u30e9\u30f3\u3092\u3082\u3061\u3001\u830e\u3068\u8449\u306e\u4e2d\u9593\u7684\u306a\u6027\u8cea\u3092\u3082\u3064\u30d5\u30ed\u30f3\u30c9\u3068\u547c\u3070\u308c\u308b\u8449\u72b6\u4f53\u3092\u5f62\u6210\u3059\u308b\u3053\u3068\u3084\u3001\u5074\u6839\u3084\u6839\u6bdb\u3092\u5f62\u6210\u3057\u306a\u3044\u3053\u3068\u306a\u3069\u304b\u3089\u3001\u30b5\u30c8\u30a4\u30e2\u79d1\u306e\u307f\u306a\u3089\u305a\u88ab\u5b50\u690d\u7269\u5168\u4f53\u306e\u4e2d\u3067\u3082\u7279\u7570\u3067\u3042\u308b\u3002Armstrong (2021) \u306e\u30a6\u30a7\u30d6\u30b5\u30a4\u30c8 (https:\/\/www.waynesword.net\/1wayindx.htm<\/a>) \u306b\u306f\u3001\u8a73\u7d30\u3067\u308f\u304b\u308a\u3084\u3059\u3044\u56f3\u89e3\u304c\u63b2\u8f09\u3055\u308c\u3066\u304a\u308a\u3001\u7406\u89e3\u306e\u52a9\u3051\u3068\u306a\u308b\u3002<\/p>\n\n\n\n

\u30b2\u30ce\u30e0\u89e3\u6790\u304b\u3089\u306f\u3001\u8010\u75c5\u6027\u95a2\u9023\u907a\u4f1d\u5b50\u306e\u5897\u52a0\u3001\u6982\u65e5\u30ea\u30ba\u30e0\u95a2\u9023\u907a\u4f1d\u5b50\u304a\u3088\u3073\u767a\u751f\u95a2\u9023\u907a\u4f1d\u5b50\u306e\u6e1b\u5c11\u304c\u5831\u544a\u3055\u308c\u3066\u3044\u308b (An et al. 2019\u3001Michael et al. 2021\u3001Park et al. 2021\u3001Fang et al. 2025)\u3002\u307e\u305f\u3001\u30df\u30b8\u30f3\u30b3\u30a6\u30ad\u30af\u30b5\u5c5e\u306e Wolffia australiana<\/em> \u3067\u306f\u3001\u30b2\u30ce\u30e0\u306e\u5b8c\u5168\u6027\u3092\u8a55\u4fa1\u3059\u308b\u6307\u6a19\u3067\u3042\u308bBUSCO (\u5e83\u7bc4\u306a\u751f\u7269\u7fa4\u3067\u4fdd\u5b58\u3055\u308c\u305f\u5358\u4e00\u30b3\u30d4\u30fc\u907a\u4f1d\u5b50\u7fa4\u3092\u7528\u3044\u305f\u8a55\u4fa1) \u306b\u304a\u3044\u3066\u3001\u5b8c\u5168\u9577\u3068\u3057\u3066\u691c\u51fa\u3055\u308c\u305f\u907a\u4f1d\u5b50\u306e\u5272\u5408\u304c\u7d0470%\u3067\u3042\u3063\u305f\u3053\u3068\u304c\u5831\u544a\u3055\u308c\u3066\u3044\u308b (Michael et al. 2021)\u3002<\/p>\n\n\n\n

\"\"<\/a>
\u30b5\u30c8\u30a4\u30e2\u79d1\u306e\u7cfb\u7d71\u95a2\u4fc2\u3068\u30a6\u30ad\u30af\u30b5\u4e9c\u79d1\u306e\u7cfb\u7d71\u7684\u4f4d\u7f6e  <\/strong>
Phylogenetic relationships within Araceae and the placement of Lemnoideae<\/strong><\/figcaption><\/figure>\n\n\n\n
\"\"<\/a>
\u30a4\u30dc\u30a6\u30ad\u30af\u30b5 Lemna gibba<\/em>_1: Lemna gibba<\/em>_20150313_1, CC BY-NC. Wolffia microscopica<\/em>_1: Wolffia microscopica<\/em>_20150917_1, CC BY-NC. \u30a6\u30ad\u30af\u30b5 Spirodela polyrhiza<\/em>_1: Spirodela polyrhiza<\/em>_20261006_1. CC BY-NC. \u30a6\u30ad\u30af\u30b5 Spirodela polyrhiza<\/em>_2: Spirodela polyrhiza<\/em>_20260716_1. CC BY-NC.
<\/figcaption><\/figure>\n\n\n\n

Lemnoideae<\/strong><\/p>\n\n\n\n

Plants in the subfamily Lemnoideae have a body plan distinct from that of most other land plants. They are unusual not only within Araceae but also among angiosperms as a whole in forming a thallus, known as a frond, with characteristics intermediate between those of stems and leaves, and in lacking lateral roots and root hairs. Armstrong\u2019s (2021) website (https:\/\/www.waynesword.net\/1wayindx.htm<\/a>) provides detailed, clear illustrations that aid understanding of their morphology.<\/p>\n\n\n\n

Genome analyses have revealed an increase in the number of disease resistance-related genes and reductions in the numbers of genes associated with circadian rhythms and development (An et al. 2019; Michael et al. 2021; Park et al. 2021; Fang et al. 2025). In Wolffia australiana<\/em>, approximately 70% of the genes assessed using BUSCO, a measure of genome completeness based on sets of widely conserved single-copy orthologs, were detected as complete in the genome assemblies (Michael et al. 2021).<\/p>\n\n\n\n

\u6804\u990a\u7e41\u6b96\u80fd\u529b\u304c\u9ad8\u304f\u3001\u30df\u30b8\u30f3\u30b3\u30a6\u30ad\u30af\u30b5\u5c5e\u306e8\u7a2e\u3067\u306f\u3001\u6804\u990a\u5206\u3068\u4e8c\u9178\u5316\u70ad\u7d20\u304c\u5341\u5206\u306b\u4f9b\u7d66\u3055\u308c\u308b\u6761\u4ef6\u4e0b\u3067\u3001\u304a\u304a\u3080\u306d2\u65e5\u4ee5\u5185\u306b\u65b0\u500b\u4f53\u3092\u5f62\u6210\u3067\u304d\u308b (Sree et al. 2015b)\u3002\u3053\u306e\u5897\u6b96\u901f\u5ea6\u304c\u7dad\u6301\u3055\u308c\u308b\u3068\u4eee\u5b9a\u3059\u308b\u3068\u3001\u8a08\u7b97\u4e0a\u306f4\u304b\u6708\u3067\u5730\u7403\u3068\u540c\u3058\u4f53\u7a4d\u306b\u9054\u3059\u308b\u307b\u3069\u306e\u5897\u6b96\u80fd\u529b\u3092\u3082\u3064 (Lam and Michael 2022)\u3002<\/p>\n\n\n\n

\u65fa\u76db\u306a\u5897\u6b96\u306b\u4f34\u3063\u3066\u6c34\u4e2d\u306e\u7a92\u7d20\u3084\u30ea\u30f3\u3092\u591a\u91cf\u306b\u5438\u53ce\u3059\u308b\u305f\u3081 (Fujita et al. 1999)\u3001\u6c34\u8cea\u6d44\u5316\u3078\u306e\u5229\u7528\u3084\u3001\u5897\u6b96\u3057\u305f\u690d\u7269\u4f53\u306e\u30d0\u30a4\u30aa\u71c3\u6599\u539f\u6599\u3068\u3057\u3066\u306e\u5229\u7528\u304c\u671f\u5f85\u3055\u308c\u3066\u3044\u308b (Lam and Michael 2022)\u3002\u307e\u305f\u3001\u3055\u307e\u3056\u307e\u306a\u52d5\u7269\u306e\u990c\u3068\u306a\u308b\u307b\u304b (Landolt 1998)\u3001\u30d2\u30c8\u306e\u98df\u6599\u3068\u3057\u3066\u3082\u5229\u7528\u3055\u308c\u3066\u3044\u308b (Bhanthumnavin and McGarry 1971)\u3002\u305d\u306e\u5358\u7d14\u306a\u4f53\u5236\u3084\u7279\u7570\u306a\u6027\u8cea\u306b\u7740\u76ee\u3057\u305f\u7814\u7a76\u3082\u5e45\u5e83\u304f\u884c\u308f\u308c\u3066\u3044\u308b (Acosta et al. 2021)\u3002<\/p>\n\n\n\n

\u30b5\u30c8\u30a4\u30e2\u79d1\u306e\u4ed6\u306e\u7a2e\u3068\u6bd4\u8f03\u3057\u3066\u3001\u59c9\u59b9\u7fa4\u304b\u3089\u5206\u5c90\u3057\u305f\u5f8c\u306e\u5206\u5b50\u9032\u5316\u901f\u5ea6\u304c\u901f\u3044\u3053\u3068\u304c\u5831\u544a\u3055\u308c\u3066\u3044\u308b\u304c (Nauheimer et al. 2012)\u3001\u305d\u306e\u7406\u7531\u306f\u660e\u3089\u304b\u306b\u306a\u3063\u3066\u3044\u306a\u3044\u3002<\/p>\n\n\n\n

\"\"<\/a>
Wolffia arrhiza<\/em>_1: Cropped a photo by ileye SOL, https:\/\/www.inaturalist.org\/photos\/695775700, CC BY-NC. Wolffia arrhiza<\/em>_2: Cropped a photo by Sergey Basalaev, https:\/\/www.inaturalist.org\/photos\/714938636, CC BY.<\/figcaption><\/figure>\n\n\n\n

Duckweeds have a high capacity for vegetative reproduction. Eight species of Wolffia<\/em> can produce new individuals within approximately two days when nutrients and carbon dioxide are sufficiently available (Sree et al. 2015b). Assuming that this rate of multiplication is maintained, their total volume could theoretically equal that of the Earth within four months (Lam and Michael 2022).<\/p>\n\n\n\n

Their rapid growth is accompanied by substantial uptake of nitrogen and phosphorus from the water (Fujita et al. 1999), making them promising candidates for water purification and for biomass production as a feedstock for biofuels (Lam and Michael 2022). They also serve as food for various animals (Landolt 1998) and are consumed by humans (Bhanthumnavin and McGarry 1971). Their simple body plan and distinctive traits have attracted a wide range of research interest (Acosta et al. 2021).<\/p>\n\n\n\n

Duckweeds have been reported to exhibit higher rates of molecular evolution following divergence from their sister group than other members of Araceae (Nauheimer et al. 2012), but the reasons for this remain unclear.<\/p>\n\n\n\n

\u30a6\u30ad\u30af\u30b5\u4e9c\u79d1 (Lemnoideae) \u306e\u5c5e\u9593\u306e\u7cfb\u7d71\u95a2\u4fc2\u3068\u5206\u5c90\u5e74\u4ee3<\/strong><\/p>\n\n\n\n

\u30a6\u30ad\u30af\u30b5\u4e9c\u79d1\u306e\u7956\u5148\u7cfb\u7d71\u306f\u3001\u7d041\u51041,000\u4e07\u5e74\u524d\u306b\u30b5\u30c8\u30a4\u30e2\u79d1\u306e\u4ed6\u306e\u4e9c\u79d1\u306b\u3064\u306a\u304c\u308b\u7cfb\u7d71\u304b\u3089\u5206\u5c90\u3057\u3001\u30a6\u30ad\u30af\u30b5\u5c5e Spirodela<\/em> \u3068\u6b8b\u308a\u306e\u5c5e\u306e\u5171\u901a\u7956\u5148\u304c\u5206\u5c90\u3057\u305f\u7d047,300\u4e07\u5e74\u524d\u306b\u306f\u3001\u3059\u3067\u306b\u73fe\u5728\u306e\u3088\u3046\u306a\u6c34\u9762\u306b\u6d6e\u904a\u3059\u308b\u751f\u6d3b\u69d8\u5f0f\u3092\u7372\u5f97\u3057\u3066\u3044\u305f\u3068\u63a8\u5b9a\u3055\u308c\u308b\u3002\u305d\u306e\u5f8c\u3001\u767d\u4e9c\u7d00\u2013\u53e4\u7b2c\u4e09\u7d00 (K\u2013Pg) \u5883\u754c\u306e\u5927\u91cf\u7d76\u6ec5 (\u7d046,600\u4e07\u5e74\u524d) \u3092\u751f\u304d\u5ef6\u3073\u3001\u7d045,500\u4e07\u5e74\u524d\u4ee5\u964d\u306b\u6b8b\u308a\u306e4\u5c5e\u304c\u5206\u5c90\u3057\u305f\u3002<\/p>\n\n\n\n

\"\"<\/a>
\u30a6\u30ad\u30af\u30b5\u4e9c\u79d1 (Lemnoideae) \u306e\u5c5e\u9593\u306e\u7cfb\u7d71\u95a2\u4fc2\u3068\u5206\u5c90\u5e74\u4ee3<\/strong>
\u7cfb\u7d71\u95a2\u4fc2\u306fNauheimer et al. (2012)\u3001Ding et al. (2017) \u304a\u3088\u3073Zhao et al. (2022) \u306b\u3001\u5206\u5c90\u5e74\u4ee3\u306fNauheimer et al. (2012) \u306b\u57fa\u3065\u304f\u3002
Phylogenetic relationships and divergence times among genera of Lemnoideae<\/strong>
Phylogenetic relationships are based on Nauheimer et al. (2012), Ding et al. (2017), and Zhao et al. (2022), and divergence times on Nauheimer et al. (2012).<\/figcaption><\/figure>\n\n\n\n

Phylogenetic relationships and divergence times among genera of Lemnoideae<\/strong><\/p>\n\n\n\n

The ancestral lineage of Lemnoideae diverged from the lineage leading to other subfamilies of Araceae approximately 110 million years ago. By approximately 73 million years ago, when Spirodela<\/em> diverged from the common ancestor of the remaining genera, duckweeds are inferred to have already acquired a free-floating aquatic lifestyle similar to that of their present-day descendants. They subsequently survived the mass extinction at the Cretaceous\u2013Paleogene (K\u2013Pg) boundary approximately 66 million years ago, and the remaining four genera diverged from approximately 55 million years ago onward.<\/p>\n\n\n\n

\u30a6\u30ad\u30af\u30b5\u4e9c\u79d1\u5404\u5c5e\u306e\u5206\u5e03<\/strong><\/p>\n\n\n\n

\u30df\u30b8\u30f3\u30b3\u30a6\u30ad\u30af\u30b5\u5c5e\u3001\u30a2\u30aa\u30a6\u30ad\u30af\u30b5\u5c5e\u3001\u30a6\u30ad\u30af\u30b5\u5c5e\u306f\u307b\u307c\u5168\u4e16\u754c\u306b\u5206\u5e03\u3059\u308b\u304c\u3001\u30a6\u30a9\u30eb\u30d5\u30a3\u30a8\u30e9\u5c5e\u3068\u30d2\u30e1\u30a6\u30ad\u30af\u30b5\u5c5e\u306e\u5206\u5e03\u57df\u306f\u3088\u308a\u9650\u3089\u308c\u3066\u3044\u308b\u3002\u5c0f\u578b\u306e\u30d5\u30ed\u30f3\u30c9\u3084\u7c98\u7740\u6027\u306e\u3042\u308b\u6839\u306f\u3001\u9ce5\u306a\u3069\u306e\u52d5\u7269\u306b\u3088\u308b\u6563\u5e03\u3092\u901a\u3058\u3066\u3001\u5206\u5e03\u306e\u62e1\u5927\u306b\u5bc4\u4e0e\u3057\u3066\u3044\u308b\u3068\u8003\u3048\u3089\u308c\u3066\u3044\u308b (Landolt 1986\u3001Landolt 1998\u3001An et al. 2019)\u3002<\/p>\n\n\n\n

\"\"<\/a>
\u30a6\u30ad\u30af\u30b5\u4e9c\u79d1\u5404\u5c5e\u306e\u5206\u5e03<\/strong>
\u7dd1\u8272\u306f\u81ea\u751f\u5206\u5e03\u57df\u3001\u7d2b\u8272\u306f\u79fb\u5165\u5206\u5e03\u57df\u3092\u793a\u3059\u3002
Distribution of the genera of Lemnoideae<\/strong>
Green indicates native ranges, and purple indicates introduced ranges.
Source: POWO (2026). Plants of the World Online<\/em>. Facilitated by the Royal Botanic Gardens, Kew. Published on the Internet: https:\/\/powo.science.kew.org\/<\/a>. Accessed 16 September 2026. Distribution data from Kew Backbone Distributions (WCVP). \u00a9 World Checklist of Vascular Plants, licensed under CC BY 3.0.<\/figcaption><\/figure>\n\n\n\n

Distribution of the genera of Lemnoideae<\/strong><\/p>\n\n\n\n

Wolffia<\/em>, Lemna<\/em>, and Spirodela<\/em> have nearly worldwide distributions, whereas Wolffiella<\/em> and Landoltia<\/em> have more restricted ranges. Small fronds and adhesive roots are thought to facilitate dispersal by birds and other animals, thereby contributing to range expansion (Landolt 1986, 1998; An et al. 2019).<\/p>\n\n\n\n

\u30a6\u30ad\u30af\u30b5\u4e9c\u79d1\u306e\u7279\u5fb4<\/strong><\/p>\n\n\n\n

\u30a6\u30ad\u30af\u30b5\u4e9c\u79d1\u306f\u4ee5\u4e0b\u306e\u7279\u5fb4\u3092\u3082\u3064\uff1a(1) \u81ea\u7531\u6d6e\u904a\u6027\u306e\u6c34\u751f\u690d\u7269\u3067\u3042\u308b\u3001(2) \u30d5\u30ed\u30f3\u30c9 (\u5909\u5f62\u3057\u305f\u30b7\u30e5\u30fc\u30c8) \u3092\u5f62\u6210\u3057\u3001\u305d\u306e\u57fa\u90e8\u304c\u4ed6\u306e\u88ab\u5b50\u690d\u7269\u306e\u830e\u9802\u5206\u88c2\u7d44\u7e54\u3068\u540c\u69d8\u306b\u50cd\u304d\u3001\u65b0\u305f\u306a\u30d5\u30ed\u30f3\u30c9\u3092\u5f62\u6210\u3059\u308b\u3001(3) \u82b1\u306f\u5c0f\u3055\u304f\u30011\u82b1\u3042\u305f\u308a\u306e\u96c4\u305a\u3044\u306f1\uff5e2\u672c\u3067\u3042\u308b\u3001(4) \u30df\u30b8\u30f3\u30b3\u30a6\u30ad\u30af\u30b5\u5c5e\u3068\u30a6\u30a9\u30eb\u30d5\u30a3\u30a8\u30e9\u5c5e\u306f\u6839\u3092\u5f62\u6210\u3057\u306a\u3044\u304c\u3001\u4ed6\u306e3\u5c5e\u3067\u306f\u3001\u6839\u306e\u4f38\u9577\u521d\u671f\u306b\u5468\u56f2\u306e\u30d5\u30ed\u30f3\u30c9\u7d44\u7e54\u3082\u540c\u6642\u306b\u4f38\u9577\u3057\u3066\u6839\u3092\u8986\u3044\u3001\u305d\u306e\u5f8c\u306e\u6839\u306e\u4f38\u9577\u306b\u4f34\u3063\u3066\u3001\u6839\u306e\u5148\u7aef\u90e8\u306b\u306f\u6839\u9798\u3068\u3057\u3066\u3001\u57fa\u90e8\u306b\u306f\u9798\u72b6\u7d44\u7e54\u3068\u3057\u3066\u6b8b\u308b\u3001(5) \u30d5\u30ed\u30f3\u30c9\u306b\u30b7\u30e5\u30a6\u9178\u30ab\u30eb\u30b7\u30a6\u30e0\u306e\u7d50\u6676\u3092\u542b\u3080\u7d30\u80de\u3084\u8272\u7d20\u7d30\u80de\u3092\u5f62\u6210\u3059\u308b\u3001(6) \u30d5\u30ed\u30f3\u30c9\u306b\u6c17\u5ba4 (air spaces) \u3092\u5f62\u6210\u3059\u308b\u3002<\/p>\n\n\n\n

\u30a6\u30ad\u30af\u30b5\u4e9c\u79d1\u306e\u7279\u5fb4 (1) \u81ea\u7531\u6d6e\u904a\u6027\u306e\u6c34\u751f\u690d\u7269<\/strong><\/p>\n\n\n\n

\u30a6\u30ad\u30af\u30b5\u4e9c\u79d1\u3068\u540c\u69d8\u306e\u81ea\u7531\u6d6e\u904a\u6027\u306e\u6c34\u751f\u690d\u7269\u3068\u3057\u3066\u306f\u3001\u540c\u3058\u30b5\u30c8\u30a4\u30e2\u79d1\u306e\u30dc\u30bf\u30f3\u30a6\u30ad\u30af\u30b5\u5c5e\u3001\u30df\u30ba\u30a2\u30aa\u30a4\u79d1\u306e\u30db\u30c6\u30a4\u30a2\u30aa\u30a4\u3001\u8584\u56a2\u30b7\u30c0\u985e\u306e\u30b5\u30f3\u30b7\u30e7\u30a6\u30e2\u5c5e\u304a\u3088\u3073\u30a2\u30ab\u30a6\u30ad\u30af\u30b5\u5c5e\u3001\u30bf\u30a4\u985e\u306e\u30a6\u30ad\u30b4\u30b1 Riccia fluitans<\/em> \u306a\u3069\u304c\u77e5\u3089\u308c\u3066\u3044\u308b\u3002\u3053\u308c\u3089\u306e\u690d\u7269\u306e\u81ea\u7531\u6d6e\u904a\u6027\u306e\u751f\u6d3b\u69d8\u5f0f\u306f\u3001\u9678\u4e0a\u751f\u6d3b\u3092\u3057\u3066\u3044\u305f\u305d\u308c\u305e\u308c\u306e\u7956\u5148\u304b\u3089\u72ec\u7acb\u306b\u9032\u5316\u3057\u305f\u3002<\/p>\n\n\n\n

\"\"<\/a>
\u30a6\u30ad\u30af\u30b5\u4e9c\u79d1\u306e\u7279\u5fb4 (1)\u81ea\u7531\u6d6e\u904a\u6027\u306e\u6c34\u751f\u690d\u7269<\/strong>
Characteristics of Lemnoideae (1): Free-floating aquatic plants<\/strong>
\u30d2\u30e1\u30a6\u30ad\u30af\u30b5 Landoltia punctata<\/em>_1: Landoltia punctata<\/em>_1_20140417_1, CC BY-NC.<\/figcaption><\/figure>\n\n\n\n

Characteristics of Lemnoideae<\/strong><\/p>\n\n\n\n

Members of Lemnoideae have the following characteristics: (1) they are free-floating aquatic plants; (2) they form fronds (modified shoots), whose basal regions function similarly to the shoot apical meristems of other angiosperms, producing new fronds; (3) their flowers are small, with only one or two stamens per flower; (4) Wolffia<\/em> and Wolffiella<\/em> lack roots, whereas in the other three genera, the surrounding frond tissue elongates along with the root during its early development, enclosing it, and subsequently persists as a root sheath at the tip and as sheath-like tissue at the base as the root continues to elongate; (5) their fronds contain cells bearing calcium oxalate crystals and pigment cells; and (6) their fronds develop air spaces.<\/p>\n\n\n\n

Characteristics of Lemnoideae (1): Free-floating aquatic plants<\/strong><\/p>\n\n\n\n

Other free-floating aquatic plants include Pistia<\/em>, which also belongs to Araceae; water hyacinth in Pontederiaceae; the leptosporangiate ferns Salvinia<\/em> and Azolla<\/em>; and the liverwort Riccia fluitans<\/em>. The free-floating lifestyle evolved independently in these lineages from their respective terrestrial ancestors.<\/p>\n\n\n\n

\u30a6\u30ad\u30af\u30b5\u4e9c\u79d1\u306e\u7279\u5fb4<\/strong><\/p>\n\n\n\n

(2) \u30d5\u30ed\u30f3\u30c9 (\u5909\u5f62\u3057\u305f\u30b7\u30e5\u30fc\u30c8) \u3092\u5f62\u6210\u3057\u3001\u305d\u306e\u57fa\u90e8\u304c\u4ed6\u306e\u88ab\u5b50\u690d\u7269\u306e\u830e\u9802\u5206\u88c2\u7d44\u7e54\u3068\u540c\u69d8\u306b\u50cd\u304d\u3001\u65b0\u305f\u306a\u30d5\u30ed\u30f3\u30c9\u3092\u5f62\u6210\u3059\u308b (Landolt 1988)<\/strong><\/p>\n\n\n\n

\u30a6\u30ad\u30af\u30b5\u306e\u4e38\u3044\u8449\u72b6\u306e\u5668\u5b98\u306f\u5909\u5f62\u3057\u305f\u30b7\u30e5\u30fc\u30c8\u3067\u3042\u308a\u3001\u30d5\u30ed\u30f3\u30c9 frond\u3001\u8449\u7684\u5668\u5b98\u3001\u307e\u305f\u306f\u30d5\u30a3\u30ed\u30fc\u30e0 phyllome \u3068\u547c\u3070\u308c\u308b (Lemon and Posluszny 2000)\u3002\u5404\u30d5\u30ed\u30f3\u30c9\u306f\u3001\u57fa\u90e8\u306e\u4e21\u5074\u306b\u305d\u308c\u305e\u308c\u8907\u6570\u306e\u5b50\u30d5\u30ed\u30f3\u30c9\u3092\u5f62\u6210\u3067\u304d\u308b\u3002
\u4e0b\u56f3\u3067\u306f\u3001\u89aa\u30d5\u30ed\u30f3\u30c9\u306e\u53f3\u4e0b\u306b\u5f62\u6210\u3055\u308c\u305f\u5b50\u30d5\u30ed\u30f3\u30c9\u306f\u3001\u67c4 stipe \u306e\u4f38\u9577\u306b\u3088\u3063\u3066\u89aa\u30d5\u30ed\u30f3\u30c9\u304b\u3089\u96e2\u308c\u3066\u3044\u308b (\u9ed2\u8272\u77e2\u5370)\u3002\u3053\u306e\u5b50\u30d5\u30ed\u30f3\u30c9\u306f\u3001\u53f3\u5074\u306b2\u3064 (\u6c34\u8272\u77e2\u5370)\u3001\u5de6\u5074\u306b1\u3064 (\u8d64\u8272\u77e2\u5370) \u306e\u65b0\u305f\u306a\u30d5\u30ed\u30f3\u30c9\u3092\u5f62\u6210\u3057\u3066\u3044\u308b\u3002\u53f3\u5074\u3067\u6700\u521d\u306b\u5f62\u6210\u3055\u308c\u305f\u30d5\u30ed\u30f3\u30c9 (\u661f\u53701\u3064) \u306f\u3001\u67c4\u306e\u4f38\u9577\u306b\u3088\u3063\u3066\u5b50\u30d5\u30ed\u30f3\u30c9\u304b\u3089\u96e2\u308c\u3066\u3044\u308b\u3002\u3053\u306e\u67c4\u306f\u3001\u5199\u771f\u3067\u306f2\u756a\u76ee\u306e\u30d5\u30ed\u30f3\u30c9 (\u661f\u53702\u3064) \u306e\u4e0b\u306b\u96a0\u308c\u3066\u898b\u3048\u306a\u3044\u3002\u4e00\u65b9\u30012\u756a\u76ee\u306e\u30d5\u30ed\u30f3\u30c9\u306e\u67c4\u306f\u4f38\u9577\u3057\u3066\u304a\u3089\u305a\u3001\u3053\u306e\u30d5\u30ed\u30f3\u30c9\u306f\u5b50\u30d5\u30ed\u30f3\u30c9\u306b\u63a5\u3057\u3066\u3044\u308b\u3002\u3055\u3089\u306b\u3001\u53f3\u5074\u3067\u6700\u521d\u306b\u5f62\u6210\u3055\u308c\u305f\u30d5\u30ed\u30f3\u30c9 (\u661f\u53701\u3064) \u306e\u5de6\u5074\u306b\u306f\u3001\u65b0\u305f\u306a\u30d5\u30ed\u30f3\u30c9 (\u9ec4\u7dd1\u8272\u77e2\u5370) \u304c\u5f62\u6210\u3055\u308c\u3066\u3044\u308b\u3002\u30d5\u30ed\u30f3\u30c9\u306e\u5bff\u547d\u306f\u6570\u9031\u9593\u3068\u77ed\u3044 (Ashby et al. 1951)\u3002<\/p>\n\n\n\n

\"\"<\/a>
\u30a6\u30ad\u30af\u30b5\u4e9c\u79d1\u306e\u7279\u5fb4<\/strong>
(2) \u30d5\u30ed\u30f3\u30c9 (\u5909\u5f62\u3057\u305f\u30b7\u30e5\u30fc\u30c8) \u3092\u5f62\u6210\u3057\u3001\u305d\u306e\u57fa\u90e8\u304c\u4ed6\u306e\u88ab\u5b50\u690d\u7269\u306e\u830e\u9802\u5206\u88c2\u7d44\u7e54\u3068\u540c\u69d8\u306b\u50cd\u304d\u3001\u65b0\u305f\u306a\u30d5\u30ed\u30f3\u30c9\u3092\u5f62\u6210\u3059\u308b (Landolt 1988)<\/strong>
Characteristics of Lemnoideae<\/strong>
(2) Fronds (modified shoots) whose basal regions function similarly to the shoot apical meristems of other angiosperms, producing new fronds (Landolt 1988)<\/strong>
\u30a6\u30ad\u30af\u30b5 Spirodela polyrhiza<\/em>_3: Spirodela polyrhiza<\/em>_20260911_1, CC BY-NC.<\/figcaption><\/figure>\n\n\n\n

Characteristics of Lemnoideae<\/strong><\/p>\n\n\n\n

(2) Fronds (modified shoots) whose basal regions function similarly to the shoot apical meristems of other angiosperms, producing new fronds (Landolt 1988)<\/strong><\/p>\n\n\n\n

The rounded, leaf-like organ of Spirodela<\/em> is a modified shoot referred to as a frond, a leaf-like organ, or a phyllome (Lemon and Posluszny 2000). Each frond can produce multiple daughter fronds on either side of its base.<\/p>\n\n\n\n

In the image below, the daughter frond formed at the lower right of the parent frond has moved away from it through elongation of the stipe (black arrow). This daughter frond has produced two new fronds on its right side (light blue arrows) and one on its left (red arrow). The first frond formed on the right (one asterisk) has moved away from the daughter frond through stipe elongation. This stipe is hidden beneath the second frond (two asterisks) in the photograph. In contrast, the stipe of the second frond has not elongated, and this frond remains in contact with the daughter frond. A further frond (yellow-green arrow) has formed on the left side of the first frond on the right (one asterisk). Fronds have a short lifespan of only a few weeks (Ashby et al. 1951).<\/p>\n\n\n\n

\u30a6\u30ad\u30af\u30b5\u4e9c\u79d1\u306e\u30d5\u30ed\u30f3\u30c9\u3092\u5358\u4f4d\u3068\u3059\u308b\u6210\u9577\u69d8\u5f0f\u306f\u3001\u3069\u306e\u3088\u3046\u306b\u751f\u3058\u308b\u306e\u3060\u308d\u3046\u304b\u3002\u30a2\u30aa\u30a6\u30ad\u30af\u30b5\u5c5e Lemna perpusilla<\/em> \u3067\u306f\u3001\u53d7\u7cbe\u5375\u304b\u3089\u306e\u767a\u751f\u904e\u7a0b\u304c\u5831\u544a\u3055\u308c\u3066\u3044\u308b (Blodgett 1923\u3001Maheshwari and Kapil 1963)\u3002
\u53d7\u7cbe\u5375\u306f\u5206\u88c2\u3057\u3066\u68cd\u68d2\u72b6\u306e\u80da\u3092\u5f62\u6210\u3059\u308b\u3002\u80da\u3067\u306f\u7d30\u80de\u5206\u88c2\u304c\u7d9a\u304f\u304c\u3001\u6839\u7aef\u5206\u88c2\u7d44\u7e54\u3084\u830e\u9802\u5206\u88c2\u7d44\u7e54\u306f\u5f62\u6210\u3055\u308c\u305a\u3001\u5074\u65b9\u306b\u7b2c1\u30d5\u30ed\u30f3\u30c9\u306e\u539f\u57fa\u304c\u4f38\u9577\u3059\u308b\u3002\u305d\u306e\u5f8c\u3001\u7b2c1\u30d5\u30ed\u30f3\u30c9\u539f\u57fa\u306e\u57fa\u90e8\u304b\u3089\u5b50\u8449\u9798\u304c\u4f38\u9577\u3057\u3001\u3053\u306e\u539f\u57fa\u3092\u8986\u3046\u3002\u7d9a\u3044\u3066\u3001\u7b2c1\u30d5\u30ed\u30f3\u30c9\u539f\u57fa\u306e\u57fa\u90e8\u5074\u306b\u3001\u5b50\u30d5\u30ed\u30f3\u30c9 (\u7b2c2\u30d5\u30ed\u30f3\u30c9) \u306e\u539f\u57fa\u304c\u9686\u8d77\u3059\u308b\u3002<\/p>\n\n\n\n

\u6210\u719f\u3057\u305f\u30d5\u30ed\u30f3\u30c9\u306f\u57fa\u90e8\u306e\u5de6\u53f3\u4e21\u5074\u306b\u5b50\u30d5\u30ed\u30f3\u30c9\u3092\u5f62\u6210\u3059\u308b\u304c\u3001\u4f55\u4e16\u4ee3\u76ee\u306e\u30d5\u30ed\u30f3\u30c9\u304b\u3089\u4e21\u5074\u306b\u5f62\u6210\u3059\u308b\u3088\u3046\u306b\u306a\u308b\u306e\u304b\u306f\u660e\u3089\u304b\u3067\u306a\u304f\u3001\u7b2c1\u30d5\u30ed\u30f3\u30c9\u306e\u5de6\u53f3\u306b\u7b2c2\u30d5\u30ed\u30f3\u30c9\u304c1\u3064\u305a\u3064\u5f62\u6210\u3055\u308c\u308b\u304b\u3069\u3046\u304b\u3082\u8abf\u3079\u3089\u308c\u3066\u3044\u306a\u3044\u3002\u30a6\u30ad\u30af\u30b5\u4e9c\u79d1\u306e\u3046\u3061\u3001\u30a6\u30a9\u30eb\u30d5\u30a3\u30a8\u30e9\u5c5e\u3068\u30df\u30b8\u30f3\u30b3\u30a6\u30ad\u30af\u30b5\u5c5e\u306f\u3001\u30d5\u30ed\u30f3\u30c9\u57fa\u90e8\u306e1\u304b\u6240\u304b\u3089\u5b50\u30d5\u30ed\u30f3\u30c9\u3092\u5f62\u6210\u3059\u308b\u3002\u305d\u306e\u305f\u3081\u3001\u4ed6\u306e3\u5c5e\u3067\u307f\u3089\u308c\u308b\u57fa\u90e8\u306e\u5de6\u53f32\u304b\u6240\u304b\u3089\u5b50\u30d5\u30ed\u30f3\u30c9\u3092\u5f62\u6210\u3059\u308b\u4ed5\u7d44\u307f\u304c\u3001\u767a\u751f\u904e\u7a0b\u306e\u3069\u306e\u6bb5\u968e\u3067\u6210\u7acb\u3059\u308b\u306e\u304b\u306f\u3001\u9032\u5316\u3068\u767a\u751f\u306e\u95a2\u4fc2\u3092\u8003\u3048\u308b\u4e0a\u3067\u8208\u5473\u6df1\u3044\u3002<\/p>\n\n\n\n

\u30a6\u30ad\u30af\u30b5\u5c5e\u3068\u30d2\u30e1\u30a6\u30ad\u30af\u30b5\u5c5e\u3067\u306f\u3001\u6804\u990a\u6210\u9577\u6642\u306b\u30d5\u30ed\u30f3\u30c9\u57fa\u90e8\u306b\u819c\u72b6\u306e\u524d\u51fa\u8449 prophyll \u304c\u5f62\u6210\u3055\u308c\u308b (Les and Crawford 1999\u3001Cusimano et al. 2011)\u3002\u3057\u304b\u3057\u3001\u3053\u308c\u3089\u306e\u5c5e\u306e\u80da\u767a\u751f\u904e\u7a0b\u3067\u3001\u7b2c1\u30d5\u30ed\u30f3\u30c9\u3084\u7b2c2\u30d5\u30ed\u30f3\u30c9\u306e\u5f62\u6210\u6642\u306b\u3082\u524d\u51fa\u8449\u304c\u5f62\u6210\u3055\u308c\u308b\u304b\u3069\u3046\u304b\u3092\u8abf\u3079\u305f\u6587\u732e\u306f\u898b\u3064\u304b\u3089\u306a\u304b\u3063\u305f\u3002\u7b2c1\u30d5\u30ed\u30f3\u30c9\u306e\u5f62\u6210\u6642\u306b\u524d\u51fa\u8449\u304c\u5f62\u6210\u3055\u308c\u306a\u3044\u306e\u3067\u3042\u308c\u3070\u3001\u5b50\u8449\u9798\u304c\u524d\u51fa\u8449\u306b\u76f8\u5f53\u3059\u308b\u5668\u5b98\u3067\u3042\u308b\u53ef\u80fd\u6027\u3082\u8003\u3048\u3089\u308c\u308b\u3002\u3053\u306e\u53ef\u80fd\u6027\u3092\u691c\u8a3c\u3059\u308b\u306b\u306f\u3001\u4e21\u8005\u306e\u767a\u751f\u4f4d\u7f6e\u3084\u5f62\u6210\u904e\u7a0b\u3092\u6bd4\u8f03\u3059\u308b\u5fc5\u8981\u304c\u3042\u308b\u3002<\/p>\n\n\n\n

\"\"<\/a>
Lemna perpusilla<\/em>_1: Reproduced from Blodgett (1923), Public Domain.<\/figcaption><\/figure>\n\n\n\n

How does the growth pattern based on successive fronds arise during development in Lemnoideae? Development from the zygote has been described in Lemna perpusilla<\/em> (Blodgett 1923; Maheshwari and Kapil 1963).<\/p>\n\n\n\n

The zygote divides to form a club-shaped embryo. Cell division continues, but neither a root apical meristem nor a shoot apical meristem forms; instead, the first frond primordium grows laterally. The cotyledonary sheath then extends from the base of the first frond primordium and encloses it. Subsequently, a daughter frond primordium (the second frond) emerges near the base of the first frond primordium.<\/p>\n\n\n\n

Mature fronds produce daughter fronds on both sides of their bases, but it remains unclear at which frond generation this bilateral pattern first appears. Whether the first frond produces a second-generation frond on each side has not been investigated. Within Lemnoideae, Wolffiella<\/em> and Wolffia<\/em> produce daughter fronds from a single site at the frond base. Determining when during development the formation of daughter fronds at two sites, one on either side of the base, becomes established in the other three genera is therefore of interest for understanding the relationship between evolution and development.<\/p>\n\n\n\n

In Spirodela<\/em> and Landoltia<\/em>, a membranous prophyll forms at the frond base during vegetative growth (Les and Crawford 1999; Cusimano et al. 2011). However, I found no studies examining whether a prophyll also forms during the development of the first or second frond in embryogenesis in these genera. If no prophyll forms during the development of the first frond, the cotyledonary sheath may represent an organ homologous to the prophyll. Testing this possibility requires a comparison of their developmental positions and ontogeny.<\/p>\n\n\n\n

\u7b2c2\u30d5\u30ed\u30f3\u30c9\u539f\u57fa\u306e\u6210\u9577\u306b\u4f34\u3044\u3001\u305d\u306e\u8868\u5074\u3068\u88cf\u5074\u306e\u57fa\u90e8\u7d44\u7e54\u304c\u4f38\u9577\u3057\u3001\u30d5\u30e9\u30c3\u30d7 flap \u3068\u547c\u3070\u308c\u308b\u8584\u3044\u534a\u6955\u5186\u72b6\u306e\u69cb\u9020\u3068\u306a\u3063\u3066\u539f\u57fa\u3092\u8986\u3046\u3002\u3053\u3046\u3057\u3066\u5f62\u6210\u3055\u308c\u308b\u69cb\u9020\u306f\u3001\u30dd\u30b1\u30c3\u30c8 pocket \u307e\u305f\u306f\u30dd\u30fc\u30c1 pouch \u3068\u547c\u3070\u308c\u308b\u3002\u7b2c2\u30d5\u30ed\u30f3\u30c9\u306f\u3001\u6210\u9577\u3059\u308b\u306b\u3064\u308c\u3066\u30dd\u30b1\u30c3\u30c8\u306e\u5916\u3078\u4f38\u3073\u51fa\u3059\u3002\u305d\u306e\u5f8c\u306f\u5148\u8ff0\u306e\u3088\u3046\u306b\u3001\u30d5\u30ed\u30f3\u30c9\u57fa\u90e8\u306e\u7247\u5074\u307e\u305f\u306f\u4e21\u5074\u306b\u5b50\u30d5\u30ed\u30f3\u30c9\u539f\u57fa daughter frond primordium \u304c\u5f62\u6210\u3055\u308c\u3001\u305d\u306e\u5468\u56f2\u3092\u30d5\u30e9\u30c3\u30d7\u304c\u8986\u3044\u3001\u3084\u304c\u3066\u5b50\u30d5\u30ed\u30f3\u30c9\u304c\u5916\u3078\u4f38\u3073\u51fa\u3059\u3068\u3044\u3046\u6210\u9577\u30d1\u30bf\u30fc\u30f3\u304c\u7e70\u308a\u8fd4\u3055\u308c\u308b (Lemon and Posluszny 2000)\u30021\u3064\u306e\u30dd\u30b1\u30c3\u30c8\u304b\u3089\u306f1\u3064\u307e\u305f\u306f\u8907\u6570\u306e\u5b50\u30d5\u30ed\u30f3\u30c9\u304c\u5f62\u6210\u3055\u308c\u3001\u5b50\u30d5\u30ed\u30f3\u30c9\u306e\u4ee3\u308f\u308a\u306b\u82b1\u304c\u5f62\u6210\u3055\u308c\u308b\u3053\u3068\u3082\u3042\u308b\u3002<\/p>\n\n\n\n

\u7d44\u7e54\u5b66\u7684\u7814\u7a76 (Lemon and Posluszny 2000\u3001Sree et al. 2015a) \u306b\u3088\u308b\u3068\u3001\u767a\u751f\u521d\u671f\u306e\u30d5\u30ed\u30f3\u30c9\u539f\u57fa\u306f\u3001\u6db2\u80de\u304c\u5c0f\u3055\u304f\u7d30\u80de\u8cea\u304c\u5927\u90e8\u5206\u3092\u5360\u3081\u308b\u5c0f\u578b\u306e\u7d30\u80de\u304b\u3089\u306a\u308a\u3001\u830e\u9802\u5206\u88c2\u7d44\u7e54\u306b\u4f3c\u305f\u7279\u5fb4\u3092\u793a\u3059\u3002\u305d\u306e\u5f8c\u3001\u7d30\u80de\u5206\u88c2\u3068\u7d30\u80de\u4f38\u9577\u3092\u7d4c\u3066\u3001\u8449\u72b6\u306e\u5668\u5b98\u3078\u3068\u767a\u9054\u3059\u308b\u3002\u3053\u306e\u767a\u751f\u69d8\u5f0f\u306f\u3001\u30ab\u30ef\u30b4\u30b1\u30bd\u30a6\u79d1\u306e\u30ab\u30ef\u30b4\u30b1\u30bd\u30a6\u3084\u30ab\u30ef\u30b4\u30ed\u30e2\u306b\u4f3c\u3066\u3044\u308b\u3002\u3053\u308c\u3089\u306e\u690d\u7269\u3067\u306f\u3001\u8449\u72b6\u5668\u5b98\u306e\u521d\u671f\u539f\u57fa\u3067\u3001\u830e\u9802\u5206\u88c2\u7d44\u7e54\u3067\u50cd\u304f\u907a\u4f1d\u5b50 STM<\/em> \u3084 WUS<\/em> \u306e\u767a\u73fe\u304c\u691c\u51fa\u3055\u308c\u3001\u539f\u57fa\u304c\u5927\u304d\u304f\u306a\u308b\u3068\u3001\u8449\u539f\u57fa\u3067\u50cd\u304f ARP<\/em> \u306e\u767a\u73fe\u304c\u691c\u51fa\u3055\u308c\u308b (Katayama et al. 2010)\u3002\u30a6\u30ad\u30af\u30b5\u4e9c\u79d1\u3067\u3082\u3001\u3053\u308c\u3089\u306e\u907a\u4f1d\u5b50\u306e\u767a\u73fe\u3084\u3001\u830e\u9802\u5206\u88c2\u7d44\u7e54\u3068\u8449\u539f\u57fa\u306e\u5206\u5316\u306b\u95a2\u308f\u308b\u30aa\u30fc\u30ad\u30b7\u30f3\u52d5\u614b\u3092\u89e3\u6790\u3059\u308b\u3053\u3068\u3067\u3001\u30d5\u30ed\u30f3\u30c9\u3068\u4ed6\u306e\u690d\u7269\u306e\u830e\u3084\u8449\u3068\u306e\u76f8\u540c\u6027\u3092\u7406\u89e3\u3059\u308b\u624b\u304c\u304b\u308a\u304c\u5f97\u3089\u308c\u308b\u306e\u3067\u306f\u306a\u3044\u3060\u308d\u3046\u304b\u3002 \u30a6\u30ad\u30af\u30b5\u4e9c\u79d1\u3068\u30ab\u30ef\u30b4\u30b1\u30bd\u30a6\u79d1\u306e\u3053\u308c\u3089\u306e\u690d\u7269\u306f\u3001\u4e92\u3044\u306b\u4f3c\u305f\u30dc\u30c7\u30a3\u30fc\u30d7\u30e9\u30f3\u3092\u3082\u3064\u4e00\u65b9\u3067\u3001\u4ed6\u306e\u591a\u304f\u306e\u88ab\u5b50\u690d\u7269\u3068\u306f\u5927\u304d\u304f\u7570\u306a\u308b\u3002\u3053\u306e\u3088\u3046\u306a\u30dc\u30c7\u30a3\u30fc\u30d7\u30e9\u30f3\u304c\u72ec\u7acb\u306b\u9032\u5316\u3057\u305f\u3053\u3068\u306f\u3001\u6bd4\u8f03\u7684\u5c11\u6570\u306e\u907a\u4f1d\u7684\u5909\u5316\u306b\u3088\u3063\u3066\u30dc\u30c7\u30a3\u30fc\u30d7\u30e9\u30f3\u304c\u5927\u304d\u304f\u5909\u308f\u308a\u3046\u308b\u3053\u3068\u3084\u3001\u305d\u306e\u5909\u5316\u3092\u3082\u305f\u3089\u3059\u767a\u751f\u904e\u7a0b\u306e\u6539\u5909\u306e\u3042\u308a\u65b9\u304c\u9650\u3089\u308c\u3066\u3044\u308b\u53ef\u80fd\u6027\u3092\u793a\u5506\u3059\u308b\u306e\u304b\u3082\u3057\u308c\u306a\u3044\u3002<\/p>\n\n\n\n

\"\"<\/a>
Lemna minor<\/em>_2: Reproduced from Hegelmaier (1868), Public Domain.
Lemna aequinoctialis<\/em>_1: Reproduced from Hegelmaier (1868), Public Domain.<\/figcaption><\/figure>\n\n\n\n

As the second frond primordium grows, the basal tissues on its adaxial and abaxial sides extend to form thin, semi-elliptical structures called flaps, which enclose the primordium. The resulting structure is known as a pocket or pouch. As the second frond grows, it extends out of the pocket. Subsequent growth repeats the pattern described above: daughter frond primordia form on one or both sides of the frond base, become enclosed by flaps, and eventually grow outward from the pockets (Lemon and Posluszny 2000). Each pocket produces one or more daughter fronds, and flowers may form in place of daughter fronds.<\/p>\n\n\n\n

Histological studies (Lemon and Posluszny 2000; Sree et al. 2015a) show that early frond primordia resemble shoot apical meristems, consisting of small cells with small vacuoles and cytoplasm occupying most of the cell volume. They subsequently develop into leaf-like organs through cell division and elongation. This developmental pattern resembles that of Cladopus doianus<\/em> and Hydrobryum japonicum<\/em> in Podostemaceae. In these plants, STM<\/em> and WUS<\/em>, genes that function in the shoot apical meristem, are expressed in early primordia of leaf-like organs, whereas expression of ARP<\/em>, which functions in leaf primordia, is detected as the primordia enlarge (Katayama et al. 2010). Analyses of the expression of these genes, together with auxin dynamics associated with the differentiation of shoot apical meristems and leaf primordia, in Lemnoideae may provide insights into the homology of fronds with stems and leaves in other plants. Lemnoideae and these members of Podostemaceae share similar body plans that differ markedly from those of most other angiosperms. The independent evolution of such body plans may suggest that relatively few genetic changes can bring about substantial changes in body plan, and that the range of developmental modifications capable of producing such changes may be limited.<\/p>\n\n\n\n

\u30a6\u30ad\u30af\u30b5\u3092\u4e0b\u9762 (\u6c34\u4e2d\u5074) \u304b\u3089\u64ae\u5f71\u3057\u305f\u5199\u771f\u3002\u30d5\u30ed\u30f3\u30c9\u306e\u4e0b\u9762\u304b\u3089\u6839\u304c\u4f38\u3073\u3066\u3044\u308b\u3002\u5074\u6839\u306f\u5f62\u6210\u3055\u308c\u306a\u3044\u3002<\/p>\n\n\n\n

\"\"<\/a>
\u30a6\u30ad\u30af\u30b5 Spirodela polyrhiza<\/em>_4: Spirodela polyrhiza<\/em>_20260911_2, CC BY-NC.<\/figcaption><\/figure>\n\n\n\n

Photograph of Spirodela<\/em> viewed from below (the submerged side). Roots extend from the underside of the frond. No lateral roots are formed.<\/p>\n\n\n\n

\u6839\u3092\u53d6\u308a\u9664\u3044\u305f\u30a6\u30ad\u30af\u30b5\u3002\u67c4\u306e\u4f38\u9577\u306b\u4f34\u3044\u3001\u53f3\u5074\u306e\u5b50\u30d5\u30ed\u30f3\u30c9\u304c\u89aa\u30d5\u30ed\u30f3\u30c9\u304b\u3089\u96e2\u308c\u3064\u3064\u3042\u308b\u3002<\/p>\n\n\n\n

\"\"<\/a>
\u30a6\u30ad\u30af\u30b5 Spirodela polyrhiza<\/em>_5: Spirodela polyrhiza<\/em>_20260911_3, CC BY-NC.<\/figcaption><\/figure>\n\n\n\n

Spirodela<\/em> polyrhiza <\/em>with its roots removed. The daughter frond on the right is moving away from the parent frond as the stipe elongates.<\/p>\n\n\n\n

\u767d\u8272\u306e\u70b9\u7dda\u306f\u3001\u30dd\u30b1\u30c3\u30c8\u3092\u5f62\u6210\u3059\u308b\u30d5\u30e9\u30c3\u30d7\u306e\u8fba\u7e01\u3092\u793a\u3059\u3002\u5de6\u4e0b\u306e\u5199\u771f\u3067\u306f\u3001\u88cf\u5074\u306e\u6955\u5186\u72b6\u306e\u8584\u3044\u7d44\u7e54\u3092\u9280\u8272\u306e\u91dd\u3067\u5de6\u65b9\u5411\u306b\u6301\u3061\u4e0a\u3052\u3001\u5b50\u30d5\u30ed\u30f3\u30c9 (\u767d\u8272\u661f\u5370) \u304c\u898b\u3048\u308b\u3088\u3046\u306b\u3057\u3066\u3044\u308b\u3002\u6a59\u8272\u306e\u661f\u5370\u306f\u524d\u51fa\u8449 prophyll \u3092\u793a\u3059\u3002<\/p>\n\n\n\n

\"\"<\/a>
\u30a6\u30ad\u30af\u30b5 Spirodela polyrhiza<\/em>_6: Spirodela polyrhiza<\/em>_20260911_4, CC BY-NC.<\/figcaption><\/figure>\n\n\n\n

White dotted lines indicate the margins of the flaps forming the pocket. In the lower-left photograph, the thin, elliptical tissue on the underside is lifted toward the left with a silver needle to reveal the daughter frond (white asterisk). The orange asterisk indicates the prophyll.<\/p>\n\n\n\n

\u30a6\u30ad\u30af\u30b5\u5c5e\u3068\u30d2\u30e1\u30a6\u30ad\u30af\u30b5\u5c5e\u3067\u306f\u3001\u30dd\u30b1\u30c3\u30c8\u5185\u3067\u65b0\u305f\u306a\u30d5\u30ed\u30f3\u30c9\u304c\u5f62\u6210\u3055\u308c\u308b\u969b\u3001\u9686\u8d77\u3057\u305f\u539f\u57fa\u306e\u4e2d\u592e\u90e8\u304c\u30d5\u30ed\u30f3\u30c9\u539f\u57fa\u3068\u306a\u308a\u3001\u5468\u7e01\u90e8\u304c\u305d\u308c\u3092\u8986\u3046\u3088\u3046\u306b\u4f38\u9577\u3059\u308b\u3002\u9686\u8d77\u3057\u305f\u539f\u57fa\u3092\u30b7\u30e5\u30fc\u30c8\u539f\u57fa\u3068\u307f\u306a\u3059\u3068\u3001\u3053\u306e\u88ab\u8986\u69cb\u9020\u306f\u30b7\u30e5\u30fc\u30c8\u306e\u6700\u57fa\u90e8\u304b\u3089\u4f38\u9577\u3059\u308b\u8449\u7684\u69cb\u9020\u306b\u76f8\u5f53\u3059\u308b\u305f\u3081\u3001\u524d\u51fa\u8449 prophyll \u3068\u89e3\u91c8\u3055\u308c\u3066\u3044\u308b\u3002\u3053\u308c\u30892\u5c5e\u4ee5\u5916\u3067\u306f\u3001\u30d5\u30ed\u30f3\u30c9\u5f62\u6210\u6642\u306b\u524d\u51fa\u8449\u306f\u5f62\u6210\u3055\u308c\u306a\u3044\u3002<\/p>\n\n\n\n

\"\"<\/a>
\u30a6\u30ad\u30af\u30b5 Spirodela polyrhiza<\/em>_7: Spirodela polyrhiza<\/em>_20260911_5, CC BY-NC.
\u30a6\u30ad\u30af\u30b5 Spirodela polyrhiza<\/em>_8: Spirodela polyrhiza<\/em>_20260911_6, CC BY-NC.<\/figcaption><\/figure>\n\n\n\n

In Spirodela<\/em> and Landoltia<\/em>, when a new frond develops within a pocket, the central region of the emerging primordium becomes the frond primordium, while its peripheral region extends to enclose it. If the emerging primordium is regarded as a shoot primordium, this enclosing structure represents a leaf-like structure growing from the very base of the shoot and is therefore interpreted as a prophyll. In the other three genera, no prophyll forms during frond development.<\/p>\n\n\n\n

\u30a6\u30ad\u30af\u30b5\u5c5e\u3001\u30d2\u30e1\u30a6\u30ad\u30af\u30b5\u5c5e\u3001\u30a2\u30aa\u30a6\u30ad\u30af\u30b5\u5c5e\u3067\u306f\u3001\u30d5\u30ed\u30f3\u30c9\u57fa\u90e8\u306e\u4e21\u5074\u306b\u30dd\u30b1\u30c3\u30c8\u3092\u5f62\u6210\u3059\u308b\u3053\u3068\u304c\u591a\u3044\u304c\u3001\u30df\u30b8\u30f3\u30b3\u30a6\u30ad\u30af\u30b5\u5c5e\u3068\u30a6\u30a9\u30eb\u30d5\u30a3\u30a8\u30e9\u5c5e\u3067\u306f\u3001\u57fa\u90e8\u306b1\u3064\u306e\u30dd\u30b1\u30c3\u30c8\u3092\u5f62\u6210\u3059\u308b\u3002<\/p>\n\n\n\n

\u89aa\u30d5\u30ed\u30f3\u30c9\u304b\u3089\u5b50\u30d5\u30ed\u30f3\u30c9\u3001\u5b50\u30d5\u30ed\u30f3\u30c9\u304b\u3089\u5b6b\u30d5\u30ed\u30f3\u30c9\u304c\u5f62\u6210\u3055\u308c\u308b\u30d1\u30bf\u30fc\u30f3\u306f\u3001\u30b7\u30e5\u30fc\u30c8\u304b\u3089\u9806\u6b21\u5074\u679d\u304c\u5f62\u6210\u3055\u308c\u308b\u30d1\u30bf\u30fc\u30f3\u306b\u4f3c\u3066\u3044\u308b\u3002\u307e\u305f\u30011\u3064\u306e\u30dd\u30b1\u30c3\u30c8\u304b\u3089\u8907\u6570\u306e\u30d5\u30ed\u30f3\u30c9\u304c\u5f62\u6210\u3055\u308c\u308b\u3053\u3068\u3082\u3042\u308a\u3001\u3053\u308c\u306f1\u3064\u306e\u8449\u814b\u306b\u8907\u6570\u306e\u82bd\u304c\u5f62\u6210\u3055\u308c\u308b\u8907\u82bd\u306b\u4f3c\u3066\u3044\u308b\u3002\u3057\u304b\u3057\u3001\u30d5\u30ed\u30f3\u30c9\u304c\u4ed6\u306e\u690d\u7269\u306e\u3069\u306e\u5668\u5b98\u3068\u76f8\u540c\u3067\u3042\u308b\u304b\u306b\u3064\u3044\u3066\u306f\u3001(1) \u8449 (Hoffmann 1840)\u3001(2) \u30b7\u30e5\u30fc\u30c8 (Hegelmaier 1868\u3001Brunaud 1974)\u3001(3) \u57fa\u90e8\u306f\u30b7\u30e5\u30fc\u30c8\u3001\u5148\u7aef\u90e8\u306f\u8449\u7684\u5668\u5b98 (Engler 1877\u3001Hegelmaier 1895\u3001Caldwell 1899\u3001Arber 1919\u3001Meusel 1951\u3001Kandeler 1979) \u3068\u3059\u308b\u4eee\u8aac\u304c\u63d0\u5531\u3055\u308c\u3066\u3044\u308b (Landolt 1998)\u3002\u767a\u751f\u904e\u7a0b\u306b\u304a\u3051\u308b\u30aa\u30fc\u30ad\u30b7\u30f3\u5206\u5e03\u306e\u5909\u5316\u3084\u3001\u30b7\u30ed\u30a4\u30cc\u30ca\u30ba\u30ca\u306e\u830e\u9802\u5206\u88c2\u7d44\u7e54\u3084\u8449\u539f\u57fa\u3067\u767a\u73fe\u3059\u308b\u907a\u4f1d\u5b50\u306e\u76f8\u540c\u907a\u4f1d\u5b50\u306e\u767a\u73fe\u30d1\u30bf\u30fc\u30f3\u306a\u3069\u3092\u89e3\u6790\u3059\u308b\u3053\u3068\u3067\u3001\u3053\u308c\u3089\u306e\u4eee\u8aac\u306e\u59a5\u5f53\u6027\u3092\u691c\u8a3c\u3067\u304d\u308b\u3060\u308d\u3046\u3002<\/p>\n\n\n\n

\u30a6\u30ad\u30af\u30b5\u4e9c\u79d1\u306e\u3044\u304f\u3064\u304b\u306e\u7a2e\u3067\u306f\u30011\u3064\u306e\u89aa\u30d5\u30ed\u30f3\u30c9\u304c\u751f\u6daf\u306b\u5f62\u6210\u3059\u308b\u5b50\u30d5\u30ed\u30f3\u30c9\u306e\u6570\u304c\u8abf\u3079\u3089\u308c\u3066\u304a\u308a\u3001\u304a\u304a\u3080\u306d10\u301c15\u500b\u3001\u591a\u3044\u500b\u4f53\u3067\u306f\u7d0425\u500b\u306b\u9054\u3059\u308b\uff08Hillman and Culley 1978, Mejbel and Simons 2018, Ishizawa et al. 2021, Senayai et al. 2026\uff09\u3002\u5b50\u30d5\u30ed\u30f3\u30c9\u304c\u5074\u679d\u3068\u76f8\u540c\u3067\u3042\u308a\u30011\u3064\u306e\u30dd\u30b1\u30c3\u30c8\u304b\u3089\u306e\u5b50\u30d5\u30ed\u30f3\u30c9\u5f62\u6210\u30921\u3064\u306e\u8449\u814b\u304b\u3089\u306e\u5074\u679d\u5f62\u6210\u306b\u5bfe\u5fdc\u3065\u3051\u3089\u308c\u308b\u3068\u3059\u308c\u3070\u3001\u540c\u3058\u5834\u6240\u304b\u3089\u5074\u751f\u5668\u5b98\u304c\u7e70\u308a\u8fd4\u3057\u5f62\u6210\u3055\u308c\u308b\u70b9\u3067\u8208\u5473\u6df1\u3044\u3002\u88ab\u5b50\u690d\u7269\u3067\u306f\u30011\u3064\u306e\u8449\u814b\u304b\u3089\u4f38\u9577\u3059\u308b\u814b\u82bd\u306f\u901a\u5e381\u500b\u304b\u3089\u6570\u500b\u3067\u3042\u308b\u3002\u4e00\u65b9\u3001\u30a8\u30f3\u30c9\u30a6\u3067\u306f\u3001\u6458\u5fc3\u5f8c\u306b\u4f38\u9577\u3057\u59cb\u3081\u305f\u814b\u82bd\u3092\u9806\u6b21\u9664\u53bb\u3059\u308b\u3068\u3001\u65e2\u5b58\u306e4\u500b\u306e\u82bd\u306b\u52a0\u3048\u3066\u5c11\u306a\u304f\u3068\u30826\u500b\u306e\u82bd\u304c\u65b0\u305f\u306b\u5f62\u6210\u3055\u308c\u305f\u3068\u3044\u3046\u5b9f\u9a13\u4f8b\u304c\u3042\u308b\uff08Stafstrom and Sarup 2000\uff09\u3002\u30a6\u30ad\u30af\u30b5\u985e\u3067\u3082\u3001\u5b50\u30d5\u30ed\u30f3\u30c9\u304c\u89aa\u304b\u3089\u5206\u96e2\u3057\u3066\u72ec\u7acb\u3059\u308b\u3053\u3068\u3067\u3001\u5f8c\u7d9a\u306e\u5b50\u30d5\u30ed\u30f3\u30c9\u306e\u5f62\u6210\u3084\u6210\u9577\u304c\u4fc3\u3055\u308c\u3066\u3044\u308b\u306e\u304b\u3082\u3057\u308c\u306a\u3044\u3002<\/p>\n\n\n\n

\"\"<\/a>
Wolffia microscopica<\/em>_2: Wolffia microscopica_<\/em>20150917_2. CC BY-NC.
Wolffia arrhiza<\/em>_3: Reproduced from Hegelmaier (1868).<\/figcaption><\/figure>\n\n\n\n

In Spirodela<\/em>, Landoltia<\/em>, and Lemna<\/em>, pockets commonly form on both sides of the frond base, whereas in Wolffia<\/em> and Wolffiella<\/em>, a single pocket forms at the base.<\/p>\n\n\n\n

The successive formation of daughter fronds from mother fronds and granddaughter fronds from daughter fronds resembles the sequential formation of lateral branches on a shoot. Multiple fronds may also arise from a single pocket, resembling the formation of accessory buds in a single leaf axil. However, several hypotheses have been proposed regarding the homology of fronds with organs in other plants: (1) a leaf (Hoffmann 1840); (2) a shoot (Hegelmaier 1868; Brunaud 1974); and (3) a structure consisting of a basal shoot region and a distal leaf-like region (Engler 1877; Hegelmaier 1895; Caldwell 1899; Arber 1919; Meusel 1951; Kandeler 1979) (Landolt 1998). These hypotheses could be tested by examining changes in auxin distribution during development and the expression patterns of homologs of genes expressed in the shoot apical meristem or leaf primordia of Arabidopsis thaliana<\/em>.<\/p>\n\n\n\n

The number of offspring fronds produced by a single parent frond over its lifetime has been examined in several species of Lemnoideae and is generally around 10\u201315, reaching approximately 25 in some individuals (Hillman and Culley 1978, Mejbel and Simons 2018, Ishizawa et al. 2021, Senayai et al. 2026). If offspring fronds are homologous to lateral branches, and their formation within a single pocket can be compared with lateral branch formation in a single leaf axil, the repeated production of lateral organs at the same site is noteworthy. In angiosperms, usually only one to a few axillary buds grow out from a single leaf axil. In pea, however, an experiment showed that decapitation followed by successive removal of axillary buds as they began to grow induced the formation of at least six additional buds beyond the four preformed buds (Stafstrom and Sarup 2000). Similarly, in duckweeds, the detachment and subsequent independence of offspring fronds may promote the formation or growth of subsequent offspring fronds.<\/p>\n\n\n\n

\u30a6\u30ad\u30af\u30b5\u4e9c\u79d1\u306e\u7279\u5fb4<\/strong><\/p>\n\n\n\n

(3) \u82b1\u306f\u5c0f\u3055\u304f\u30011\u82b1\u3042\u305f\u308a\u306e\u96c4\u305a\u3044\u306f1\uff5e2\u672c\u3067\u3042\u308b\u3002<\/strong><\/p>\n\n\n\n

\u30a6\u30ad\u30af\u30b5\u5c5e\u3001\u30d2\u30e1\u30a6\u30ad\u30af\u30b5\u5c5e\u3001\u30a2\u30aa\u30a6\u30ad\u30af\u30b5\u5c5e\u3067\u306f\u3001\u82b1\u539f\u57fa\u306f\u30d5\u30ed\u30f3\u30c9\u539f\u57fa\u3068\u540c\u69d8\u306b\u30dd\u30b1\u30c3\u30c8\u5185\u306b\u5f62\u6210\u3055\u308c\u308b\u3002\u4e00\u65b9\u3001\u30a6\u30a9\u30eb\u30d5\u30a3\u30a8\u30e9\u5c5e\u3068\u30df\u30b8\u30f3\u30b3\u30a6\u30ad\u30af\u30b5\u5c5e\u3067\u306f\u3001\u30dd\u30b1\u30c3\u30c8\u5185\u3067\u306f\u306a\u304f\u3001\u30d5\u30ed\u30f3\u30c9\u306e\u4e0a\u9762\u306b\u5f62\u6210\u3055\u308c\u308b\u3002<\/p>\n\n\n\n

\u96c4\u305a\u3044\u306f1\uff5e2\u672c\u3001\u96cc\u305a\u3044\u306f1\u672c\u5f62\u6210\u3055\u308c\u308b (Landolt 1998)\u3002\u30a6\u30ad\u30af\u30b5\u5c5e\u3001\u30d2\u30e1\u30a6\u30ad\u30af\u30b5\u5c5e\u3001\u30a2\u30aa\u30a6\u30ad\u30af\u30b5\u5c5e\u3067\u306f\u3001\u3053\u308c\u3089\u306e\u82b1\u5668\u5b98\u5168\u4f53\u304c\u524d\u51fa\u8449 prophyll \u306b\u8986\u308f\u308c\u3066\u3044\u308b (Les and Crawford 1999\u3001Cusimano et al. 2011)\u3002\u30a2\u30aa\u30a6\u30ad\u30af\u30b5\u5c5e\u3067\u306f\u3001\u30d5\u30ed\u30f3\u30c9\u5f62\u6210\u6642\u306b\u306f\u524d\u51fa\u8449\u304c\u5f62\u6210\u3055\u308c\u306a\u3044\u304c\u3001\u82b1\u5668\u5b98\u306e\u5f62\u6210\u6642\u306b\u306f\u5f62\u6210\u3055\u308c\u308b\u3002\u3053\u306e\u524d\u51fa\u8449\u306f\u3001\u4ed6\u306e\u690d\u7269\u306e\u5c0f\u82de\u8449\u3068\u76f8\u540c\u3067\u3042\u308b\u3068\u8003\u3048\u3089\u308c\u308b\u3002\u4e00\u65b9\u3001\u82b1\u5e8f\u304c1\u3064\u306e\u82b1\u306b\u307e\u3067\u9000\u7e2e\u3057\u305f\u3082\u306e\u3068\u89e3\u91c8\u3059\u308b\u306a\u3089\u3070\u3001\u82b1\u5e8f\u82de\u8449 (\u30b5\u30c8\u30a4\u30e2\u79d1\u3067\u306f\u4ecf\u708e\u82de\u3068\u547c\u3070\u308c\u308b) \u3068\u76f8\u540c\u3067\u3042\u308b\u3068\u8003\u3048\u3089\u308c\u308b\u3002<\/p>\n\n\n\n

\"\"<\/a>
\u30a6\u30ad\u30af\u30b5\u4e9c\u79d1\u306e\u7279\u5fb4<\/strong>
(3) \u82b1\u306f\u5c0f\u3055\u304f\u30011\u82b1\u3042\u305f\u308a\u306e\u96c4\u305a\u3044\u306f1\uff5e2\u672c\u3067\u3042\u308b\u3002<\/strong>
Characteristics of Lemnoideae<\/strong>
(3) Flowers are small, with one or two stamens per flower.<\/strong>
Lemna minor<\/em>_3: Reproduced from Caldwell (1899), Public Domain. \u30a4\u30dc\u30a6\u30ad\u30af\u30b5 Lemna gibba<\/em>_2: Lemna gibba<\/em>_20150224_1. CC BY-NC. Wolffia microscopica<\/em>_3: Wolffia microscopica<\/em>_20151001_1, CC BY-NC.<\/figcaption><\/figure>\n\n\n\n

Characteristics of Lemnoideae<\/strong><\/p>\n\n\n\n

(3) Flowers are small, with one or two stamens per flower.<\/strong><\/p>\n\n\n\n

In Spirodela<\/em>, Landoltia<\/em>, and Lemna<\/em>, floral primordia form within the pockets, as do frond primordia. In Wolffiella<\/em> and Wolffia<\/em>, however, floral primordia form on the upper surface of the frond rather than within a pocket. One or two stamens and a single pistil are formed (Landolt 1998). In Spirodela<\/em>, Landoltia<\/em>, and Lemna<\/em>, these floral organs are collectively enclosed by a prophyll (Les and Crawford 1999; Cusimano et al. 2011). In Lemna<\/em>, a prophyll is absent during frond development but forms during floral development. This prophyll is considered homologous to a bracteole in other plants. Alternatively, if the reproductive structure is interpreted as an inflorescence reduced to a single flower, the prophyll would be homologous to an inflorescence bract, termed a spathe in Araceae.<\/p>\n\n\n\n

\u958b\u82b1\u524d\u306e\u30a2\u30aa\u30a6\u30ad\u30af\u30b5\u5c5e\u30a4\u30dc\u30a6\u30ad\u30af\u30b5\u306e\u82b1\u30022\u672c\u306e\u96c4\u305a\u3044\u30681\u672c\u306e\u96cc\u305a\u3044\u304c\u3001\u524d\u51fa\u8449\u3068\u30d5\u30e9\u30c3\u30d7\u306b\u8986\u308f\u308c\u3066\u3044\u308b\u3002<\/p>\n\n\n\n

\"\"<\/a>
\u30a4\u30dc\u30a6\u30ad\u30af\u30b5 Lemna gibba<\/em>_3: Lemna gibba<\/em>_20150224_2, CC BY-NC. \u30a4\u30dc\u30a6\u30ad\u30af\u30b5 Lemna gibba<\/em>_4: Lemna gibba<\/em>_20150224_3, CC BY-NC. \u30a4\u30dc\u30a6\u30ad\u30af\u30b5 Lemna gibba<\/em>_5: Lemna gibba<\/em>_20150224_4, CC BY-NC.<\/figcaption><\/figure>\n\n\n\n

A flower of Lemna gibba<\/em> before anthesis. Two stamens and a single pistil are enclosed by the prophyll and flaps.<\/p>\n\n\n\n

\u958b\u82b1\u4e2d\u306e\u30a2\u30aa\u30a6\u30ad\u30af\u30b5\u5c5e\u30a4\u30dc\u30a6\u30ad\u30af\u30b5\u306e\u82b1\u30022\u672c\u306e\u96c4\u305a\u3044\u30681\u672c\u306e\u96cc\u305a\u3044\u304c\u3001\u30d5\u30e9\u30c3\u30d7\u306e\u5916\u5074\u306b\u7a81\u51fa\u3057\u3066\u3044\u308b\u3002<\/p>\n\n\n\n

\"\"<\/a>
\u30a4\u30dc\u30a6\u30ad\u30af\u30b5 Lemna gibba<\/em>_6: Lemna gibba<\/em>_20150224_5, CC BY-NC. \u30a4\u30dc\u30a6\u30ad\u30af\u30b5 Lemna gibba<\/em>_7: Lemna gibba<\/em>_20150224_6, CC BY-NC.<\/figcaption><\/figure>\n\n\n\n

A flower of Lemna gibba<\/em> at anthesis. Two stamens and a single pistil protrude beyond the flaps.<\/p>\n\n\n\n

\u958b\u82b1\u4e2d\u306e\u30df\u30b8\u30f3\u30b3\u30a6\u30ad\u30af\u30b5\u5c5e\u306e\u82b1\u3002\u30df\u30b8\u30f3\u30b3\u30a6\u30ad\u30af\u30b5\u5c5e\u306f\u30011\u672c\u306e\u96c4\u305a\u3044\u30681\u672c\u306e\u96cc\u305a\u3044\u3092\u5f62\u6210\u3059\u308b\u3002\u96c4\u305a\u3044\u306e\u9577\u3055\u306f\u7d04200 \u00b5m\u3001\u96cc\u305a\u3044\u306e\u9577\u3055\u306f\u7d04100 \u00b5m\u3067\u3042\u308b\u3002\u30d5\u30ed\u30f3\u30c9\u304b\u3089\u307e\u305a\u96cc\u305a\u3044\u304c\u7a81\u51fa\u3057\u3001\u7d9a\u3044\u3066\u96c4\u305a\u3044\u304c\u7a81\u51fa\u3059\u308b\u3002\u96c4\u305a\u3044\u306e\u57fa\u90e8\u306b\u306f\u3001\u5148\u306b\u7a81\u51fa\u3057\u305f\u96cc\u305a\u3044\u304c\u6b8b\u3063\u3066\u3044\u308b\u3002\u6f0f\u6597\u72b6\u306e\u67f1\u982d\u306b\u306f\u5206\u6ccc\u6db2\u306e\u6ef4\u304c\u5f62\u6210\u3055\u308c\u3001\u53d7\u7c89\u306b\u5bc4\u4e0e\u3059\u308b\u3002<\/p>\n\n\n\n

\"\"<\/a>
Wolffia microscopica<\/em>_3\u301c7: Wolffia microscopica<\/em>_20151001_1\u301c5, CC BY-NC.<\/figcaption><\/figure>\n\n\n\n

A flower of Wolffia<\/em> at anthesis. Wolffia<\/em> produces a single stamen and a single pistil, approximately 200 \u00b5m and 100 \u00b5m long, respectively. The pistil protrudes from the frond first, followed by the stamen. The previously emerged pistil remains at the base of the stamen. A droplet of secretion forms on the funnel-shaped stigma and facilitates pollination.<\/p>\n\n\n\n

\u30b3\u30a6\u30ad\u30af\u30b5 Lemna minor<\/em> \u306e\u96c6\u56e3\u907a\u4f1d\u69cb\u9020\u3092\u8abf\u3079\u305f\u7814\u7a76\u3067\u306f\u3001\u540c\u3058\u6c60\u306e\u96c6\u56e3\u5185\u3067\u306f\u907a\u4f1d\u7684\u591a\u69d8\u6027\u304c\u4f4e\u3044\u4e00\u65b9\u3001\u7570\u306a\u308b\u6c60\u306e\u96c6\u56e3\u9593\u3067\u306f\u907a\u4f1d\u7684\u5206\u5316\u304c\u5927\u304d\u3044\u3053\u3068\u304c\u5831\u544a\u3055\u308c\u3066\u3044\u308b (Schmid et al. 2024\uff09\u3002\u4e00\u65b9\u3001\u540c\u3058\u7814\u7a76\u3067\u3001\u30e0\u30e9\u30b5\u30ad\u30b3\u30a6\u30ad\u30af\u30b5 L. japonica<\/em> \u3067\u306f\u7570\u306a\u308b\u6c60\u306e\u96c6\u56e3\u9593\u3067\u3082\u907a\u4f1d\u7684\u306a\u9055\u3044\u304c\u5c0f\u3055\u3044\u3053\u3068\u304c\u793a\u3055\u308c\u3066\u3044\u308b\u3002\u3053\u306e\u9055\u3044\u306f\u3001\u7a2e\u306e\u7279\u6027\u3084\u96c6\u56e3\u5f62\u6210\u306e\u6b74\u53f2\u3092\u53cd\u6620\u3057\u3066\u3044\u308b\u306e\u304b\u3082\u3057\u308c\u306a\u3044\u3002<\/p>\n\n\n\n

\u30a6\u30ad\u30af\u30b5\u4e9c\u79d1\u306e\u690d\u7269\u306f\u6804\u990a\u751f\u6b96\u304c\u512a\u52e2\u3067\u3042\u308b\u304c\u3001\u6709\u6027\u751f\u6b96\u3082\u884c\u3046\u3002\u500b\u4f53\u304c\u5bc6\u96c6\u3057\u3001\u98a8\u3084\u6c34\u6d41\u3001\u5c0f\u52d5\u7269\u306e\u52d5\u304d\u306b\u3088\u3063\u3066\u4e92\u3044\u306e\u4f4d\u7f6e\u304c\u7d76\u3048\u305a\u5909\u5316\u3059\u308b\u305f\u3081\u3001\u96c4\u305a\u3044\u304c\u5225\u306e\u500b\u4f53\u306e\u67f1\u982d\u306b\u76f4\u63a5\u63a5\u89e6\u3059\u308b\u6a5f\u4f1a\u304c\u591a\u3044\u3068\u8003\u3048\u3089\u308c\u3066\u3044\u308b (den Hartog 1964\u3001Schmid et al. 2024)\u3002\u3057\u304b\u3057\u3001\u91ce\u5916\u3067\u679c\u5b9f\u304c\u89b3\u5bdf\u3055\u308c\u308b\u3053\u3068\u306f\u5c11\u306a\u304f\u3001\u591a\u6570\u306e\u679c\u5b9f\u3092\u3064\u3051\u308b\u7a2e\u306f\u81ea\u6b96\u6027\u3067\u3042\u308b\u3068\u5831\u544a\u3055\u308c\u3066\u3044\u308b (Landolt 1998)\u3002<\/p>\n\n\n\n

\"\"<\/a>
\u30b3\u30a6\u30ad\u30af\u30b5 Lemna minor<\/em>_1: Cropped a photo by lterrill, https:\/\/www.inaturalist.org\/photos\/734860137, CC BY-NC.<\/figcaption><\/figure>\n\n\n\n

A study of population genetic structure in Lemna minor<\/em> reported low genetic diversity within populations in individual ponds but substantial genetic differentiation among populations from different ponds (Schmid et al. 2024). In contrast, the same study found little genetic differentiation among populations of L. japonica<\/em>, even across different ponds. This difference may reflect species-specific traits or the history of population establishment. <\/p>\n\n\n\n

Although vegetative reproduction predominates in Lemnoideae, sexual reproduction also occurs. Because individuals grow densely together and their relative positions are continually altered by wind, water currents, and the movements of small animals, stamens are thought to frequently come into direct contact with the stigmas of other individuals (den Hartog 1964; Schmid et al. 2024). However, fruits are rarely observed in the wild, and species that produce numerous fruits have been reported to be self-pollinating (Landolt 1998).<\/p>\n\n\n\n

\u30a6\u30ad\u30af\u30b5\u4e9c\u79d1<\/strong>\u306e\u7279\u5fb4<\/strong><\/p>\n\n\n\n

4. <\/strong>\u30df\u30b8\u30f3\u30b3\u30a6\u30ad\u30af\u30b5\u5c5e\u3068\u30a6\u30a9\u30eb\u30d5\u30a3\u30a8\u30e9\u5c5e\u306f\u6839\u3092\u5f62\u6210\u3057\u306a\u3044\u304c\u3001\u4ed6\u306e3\u5c5e\u3067\u306f\u3001\u6839\u306e\u4f38\u9577\u521d\u671f\u306b\u5468\u56f2\u306e\u30d5\u30ed\u30f3\u30c9\u7d44\u7e54\u3082\u540c\u6642\u306b\u4f38\u9577\u3057\u3066\u6839\u3092\u8986\u3044\u3001\u305d\u306e\u5f8c\u306e\u6839\u306e\u4f38\u9577\u306b\u4f34\u3063\u3066\u3001\u5148\u7aef\u90e8\u306b\u306f\u6839\u9798\u3068\u3057\u3066\u3001\u57fa\u90e8\u306b\u306f\u9798\u72b6\u7d44\u7e54\u3068\u3057\u3066\u6b8b\u308b\u3002<\/strong><\/p>\n\n\n\n

\u6839\u304c\u30d5\u30ed\u30f3\u30c9\u304b\u3089\u4f38\u3073\u51fa\u3059\u969b\u306b\u306f\u3001\u30d5\u30ed\u30f3\u30c9\u306e\u8868\u76ae\u7d30\u80de\u306b\u7531\u6765\u3059\u308b\u6839\u9798 root sheath \u306b\u8986\u308f\u308c\u3066\u3044\u308b\u3002<\/p>\n\n\n\n

\"\"<\/a>
\u30a6\u30ad\u30af\u30b5\u4e9c\u79d1\u306e\u7279\u5fb4<\/strong>
4. \u30df\u30b8\u30f3\u30b3\u30a6\u30ad\u30af\u30b5\u5c5e\u3068\u30a6\u30a9\u30eb\u30d5\u30a3\u30a8\u30e9\u5c5e\u306f\u6839\u3092\u5f62\u6210\u3057\u306a\u3044\u304c\u3001\u4ed6\u306e3\u5c5e\u3067\u306f\u3001\u6839\u306e\u4f38\u9577\u521d\u671f\u306b\u5468\u56f2\u306e\u30d5\u30ed\u30f3\u30c9\u7d44\u7e54\u3082\u540c\u6642\u306b\u4f38\u9577\u3057\u3066\u6839\u3092\u8986\u3044\u3001\u305d\u306e\u5f8c\u306e\u6839\u306e\u4f38\u9577\u306b\u4f34\u3063\u3066\u3001\u5148\u7aef\u90e8\u306b\u306f\u6839\u9798\u3068\u3057\u3066\u3001\u57fa\u90e8\u306b\u306f\u9798\u72b6\u7d44\u7e54\u3068\u3057\u3066\u6b8b\u308b\u3002<\/strong>
Characteristics of Lemnoideae<\/strong>
4. Wolffia<\/em> and Wolffiella<\/em> lack roots. In the other three genera, the surrounding frond tissue elongates along with the root during its early growth, enclosing it. As the root continues to elongate, this tissue persists as a root sheath at the tip and as sheath-like tissue at the base.<\/strong>
\u30b3\u30a6\u30ad\u30af\u30b5 Lemna minor<\/em>_4\u301c6: Reproduced from Caldwell (1899), Public Domain.<\/figcaption><\/figure>\n\n\n\n

Characteristics of Lemnoideae<\/strong><\/p>\n\n\n\n

4. Wolffia<\/em> and Wolffiella<\/em> lack roots. In the other three genera, the surrounding frond tissue elongates along with the root during its early growth, enclosing it. As the root continues to elongate, this tissue persists as a root sheath at the tip and as sheath-like tissue at the base.<\/strong> <\/p>\n\n\n\n

As the root emerges from the frond, it is enclosed by a root sheath derived from the epidermal cells of the frond.<\/p>\n\n\n\n

\u30d5\u30ed\u30f3\u30c9\u304b\u3089\u4f38\u3073\u3060\u3057\u305f\u6839\u306f\u6839\u9798 root sheath\u306b\u8986\u308f\u308c\u3066\u3044\u308b\u304c (Caldwell 1899)\u3001 \u6839\u306e\u4f38\u9577\u306b\u4f34\u3063\u3066\u6839\u9798\u306f\u5206\u65ad\u3055\u308c\u308b\u3002\u305d\u306e\u5148\u7aef\u5074\u306e\u90e8\u5206\u306f\u3001\u6839\u306e\u4f38\u9577\u4e2d\u3082\u5148\u7aef\u90e8\u306b\u4ed8\u7740\u3057\u305f\u307e\u307e\u3001\u6839\u7aef\u3092\u4fdd\u8b77\u3059\u308b (Hegelmaier 1868)\u3002<\/p>\n\n\n\n

\"\"<\/a>
\u30d2\u30ca\u30a6\u30ad\u30af\u30b5 Lemna minuta<\/em>_1: Lemna minuta<\/em>_20260920_1, CC BY-NC. \u30d2\u30ca\u30a6\u30ad\u30af\u30b5 Lemna minuta<\/em>_2: Lemna minuta<\/em>_20260920_2, CC BY-NC.<\/figcaption><\/figure>\n\n\n\n

The root emerging from the frond is enclosed by a root sheath (Caldwell 1899), which ruptures as the root elongates. Its distal portion remains attached to the root tip during elongation, protecting the root apex (Hegelmaier 1868).<\/p>\n\n\n\n

\u30a6\u30ad\u30af\u30b5\u5c5e\u3001\u30d2\u30e1\u30a6\u30ad\u30af\u30b5\u5c5e\u3001\u30a2\u30aa\u30a6\u30ad\u30af\u30b5\u5c5e\u306f\u6839\u3092\u5f62\u6210\u3059\u308b\u304c\u3001\u30a6\u30a9\u30eb\u30d5\u30a3\u30a8\u30e9\u5c5e\u3001\u30df\u30b8\u30f3\u30b3\u30a6\u30ad\u30af\u30b5\u5c5e\u306f\u6839\u3092\u5f62\u6210\u3057\u306a\u3044\u3002\u305f\u3060\u3057\u3001\u30a4\u30f3\u30c9\u7523\u306e Wolffia microscopica<\/em> \u306f\u507d\u6839\u3092\u5f62\u6210\u3059\u308b (Sree et al. 2015a)\u3002\u30d5\u30ed\u30f3\u30c9\u306e\u4e0b\u9762 (\u6c34\u4e2d\u5074) \u306e\u4e2d\u592e\u90e8\u3067\u7d30\u80de\u5206\u88c2\u6d3b\u6027\u304c\u9ad8\u307e\u308a\u3001\u6839\u72b6\u306e\u7a81\u8d77\u304c\u751f\u3058\u308b\u3002\u3053\u306e\u7a81\u8d77\u306f\u6839\u51a0\u3084\u7dad\u7ba1\u675f\u3092\u6b20\u304f\u305f\u3081\u3001\u6839\u3068\u306f\u307f\u306a\u3055\u308c\u306a\u3044\u3002\u507d\u6839\u306e\u6700\u5916\u5c64\u306f\u30d5\u30ed\u30f3\u30c9\u306e\u8868\u76ae\u3068\u9023\u7d9a\u3059\u308b1\u5c64\u306e\u7d30\u80de\u304b\u3089\u306a\u308a\u3001\u3053\u308c\u3089\u306e\u7d30\u80de\u306f\u5185\u90e8\u306e\u67d4\u7d44\u7e54\u7d30\u80de\u3088\u308a\u3082\u5c0f\u3055\u3044\u3002\u30d5\u30ed\u30f3\u30c9\u306e\u4e0b\u9762\u306e\u7279\u5b9a\u306e\u4f4d\u7f6e\u3067\u7d30\u80de\u5206\u88c2\u6d3b\u6027\u304c\u9ad8\u307e\u308a\u3001\u3055\u3089\u306b\u7a81\u8d77\u304c\u4f38\u9577\u3059\u308b\u4ed5\u7d44\u307f\u306f\u660e\u3089\u304b\u306b\u306a\u3063\u3066\u3044\u306a\u3044\u3002<\/p>\n\n\n\n

\u30df\u30b8\u30f3\u30b3\u30a6\u30ad\u30af\u30b5\u5c5e\u306e W. australiana<\/em> \u3067\u306f\u3001\u30b2\u30ce\u30e0\u89e3\u6790\u306b\u3088\u3063\u3066\u3001\u88ab\u5b50\u690d\u7269\u306e\u6839\u5f62\u6210\u306b\u95a2\u308f\u308b\u4e00\u90e8\u306e\u907a\u4f1d\u5b50\u306e\u6b20\u5931\u304c\u5831\u544a\u3055\u308c\u3066\u3044\u308b (Michael et al. 2021)\u3002W. microscopica<\/em> \u3067\u3082\u540c\u69d8\u306e\u6b20\u5931\u304c\u78ba\u8a8d\u3055\u308c\u308c\u3070\u3001\u507d\u6839\u304c\u901a\u5e38\u306e\u6839\u3068\u306f\u7570\u306a\u308b\u767a\u751f\u6a5f\u69cb\u306b\u3088\u3063\u3066\u5f62\u6210\u3055\u308c\u308b\u53ef\u80fd\u6027\u3092\u691c\u8a0e\u3059\u308b\u624b\u304c\u304b\u308a\u3068\u306a\u308b\u3002<\/p>\n\n\n\n

\"\"<\/a>
Wolffia microscopica<\/em>_8\u301c12: Wolffia microscopica_<\/em>20150917_3\u301c7, CC BY-NC.<\/figcaption><\/figure>\n\n\n\n

Spirodela<\/em>, Landoltia<\/em>, and Lemna<\/em> form roots, whereas Wolffiella<\/em> and Wolffia<\/em> do not. However, Wolffia microscopica<\/em>, native to India, forms a pseudoroot (Sree et al. 2015a). Increased cell division activity in the central region of the underside (the submerged side) of the frond gives rise to a root-like projection. This projection lacks a root cap and vascular tissue and is therefore not regarded as a root. The outermost layer of the pseudoroot consists of a single layer of cells continuous with the frond epidermis; these cells are smaller than the internal parenchyma cells. The mechanisms that locally enhance cell division at a specific site on the underside of the frond and subsequently promote elongation of the projection remain unknown.<\/p>\n\n\n\n

Genome analysis of W. australiana<\/em> has revealed the loss of some genes involved in root formation in angiosperms (Michael et al. 2021). If similar gene losses are confirmed in W. microscopica<\/em>, they could provide clues for investigating whether pseudoroots form through developmental mechanisms distinct from those of typical roots.<\/p>\n\n\n\n

\u30a6\u30ad\u30af\u30b5\u4e9c\u79d1\u306e\u7279\u5fb4<\/strong><\/p>\n\n\n\n

5. \u30d5\u30ed\u30f3\u30c9\u306b\u30b7\u30e5\u30a6\u9178\u30ab\u30eb\u30b7\u30a6\u30e0\u306e\u7d50\u6676\u3092\u542b\u3080\u7d30\u80de\u3084\u8272\u7d20\u7d30\u80de\u304c\u5f62\u6210\u3055\u308c\u308b\u3002<\/strong><\/p>\n\n\n\n

\u30df\u30b8\u30f3\u30b3\u30a6\u30ad\u30af\u30b5\u5c5e\u3068\u30a6\u30a9\u30eb\u30d5\u30a3\u30a8\u30e9\u5c5e\u3092\u9664\u304f3\u5c5e\u3067\u306f\u3001\u30d5\u30ed\u30f3\u30c9\u306b\u7d50\u6676\u3092\u542b\u3080\u7d30\u80de\u304c\u5f62\u6210\u3055\u308c\u308b\u3002\u30e9\u30d5\u30a3\u30c9\u7d30\u80de raphide cell \u3067\u306f\u3001\u6db2\u80de\u5185\u306b\u30b7\u30e5\u30a6\u9178\u30ab\u30eb\u30b7\u30a6\u30e0\u306e\u7d30\u9577\u3044\u91dd\u72b6\u7d50\u6676\u304c\u675f\u72b6\u306b\u5f62\u6210\u3055\u308c\u308b\u3002\u4e00\u65b9\u3001\u30c9\u30eb\u30fc\u30b9\u7d30\u80de druse cell \u3067\u306f\u3001\u6db2\u80de\u5185\u306b\u30b7\u30e5\u30a6\u9178\u30ab\u30eb\u30b7\u30a6\u30e0\u306e\u7d50\u6676\u304c\u653e\u5c04\u72b6\u306b\u96c6\u307e\u3063\u305f\u661f\u72b6\u306e\u7d50\u6676\u96c6\u5408\u4f53\u304c\u5f62\u6210\u3055\u308c\u308b (Franceschi and Horner 1980)\u3002\u30b7\u30e5\u30a6\u9178\u30ab\u30eb\u30b7\u30a6\u30e0\u7d50\u6676\u306e\u5f62\u6210\u306f\u3001\u7d44\u7e54\u5185\u306e\u30ab\u30eb\u30b7\u30a6\u30e0\u6fc3\u5ea6\u306e\u8abf\u7bc0\u3001\u690d\u98df\u8005\u306b\u5bfe\u3059\u308b\u9632\u5fa1\u3001\u91d1\u5c5e\u306e\u89e3\u6bd2\u306a\u3069\u306b\u95a2\u4e0e\u3059\u308b\u3068\u8003\u3048\u3089\u308c\u3066\u3044\u308b (Nakata 2003)\u3002<\/p>\n\n\n\n

Spirodela oligorhiza<\/em> \u3084 Wolffia punctata<\/em> \u3067\u306f\u3001\u7570\u578b\u7d30\u80de idioblast \u306e\u6db2\u80de\u5185\u306b\u7121\u8272\u306e\u30d5\u30e9\u30d0\u30f3 flavan \u304c\u84c4\u7a4d\u3057\u3001\u7d2b\u5916\u7dda\u3092\u53d7\u3051\u308b\u3068\u8d64\u8910\u8272\u306e\u30d5\u30a7\u30ce\u30fc\u30eb\u6027\u7269\u8cea\u3078\u3068\u5909\u5316\u3059\u308b\u3053\u3068\u3067\u3001\u8272\u7d20\u7d30\u80de\u3068\u306a\u308b (Witztum 1974)\u3002\u30d5\u30a7\u30ce\u30fc\u30eb\u5316\u5408\u7269\u306f\u7d2b\u5916\u7dda\u3092\u906e\u853d\u3057\u3001\u5149\u5408\u6210\u7d44\u7e54\u3084\u305d\u306e\u4ed6\u306e\u611f\u53d7\u6027\u306e\u9ad8\u3044\u7d44\u7e54\u3092\u640d\u50b7\u304b\u3089\u4fdd\u8b77\u3059\u308b\u3068\u8003\u3048\u3089\u308c\u3066\u3044\u308b (Gitz et al. 2004)\u3002\u3057\u304b\u3057\u3001\u306a\u305c\u3059\u3079\u3066\u306e\u7d30\u80de\u3067\u306f\u306a\u304f\u3001\u5c11\u6570\u306e\u8272\u7d20\u7d30\u80de\u306b\u9650\u3063\u3066\u30d5\u30a7\u30ce\u30fc\u30eb\u5316\u5408\u7269\u304c\u84c4\u7a4d\u3059\u308b\u306e\u304b\u306f\u660e\u3089\u304b\u306b\u306a\u3063\u3066\u3044\u306a\u3044\u3002<\/p>\n\n\n\n

\"\"<\/a>
\u30a6\u30ad\u30af\u30b5\u4e9c\u79d1\u306e\u7279\u5fb4<\/strong>
5. \u30d5\u30ed\u30f3\u30c9\u306b\u30b7\u30e5\u30a6\u9178\u30ab\u30eb\u30b7\u30a6\u30e0\u306e\u7d50\u6676\u304c\u3067\u304d\u308b\u7d30\u80de\u3084\u8272\u7d20\u7d30\u80de\u304c\u5f62\u6210\u3055\u308c\u308b\u3002<\/strong>
Characteristics of Lemnoideae<\/strong>
5. Cells containing calcium oxalate crystals and pigment cells develop in the fronds.<\/strong>
Spirodela oligorrhiza<\/em>_1: Reproduced from Hegelmaier (1868), Public Domain.
\u30a6\u30ad\u30af\u30b5 Spirodela polyrhiza<\/em>_9: Spirodela polyrhiza<\/em>_20260911_7, CC BY-NC.<\/figcaption><\/figure>\n\n\n\n

Characteristics of Lemnoideae<\/strong><\/p>\n\n\n\n

5. Cells containing calcium oxalate crystals and pigment cells develop in the fronds.<\/strong><\/p>\n\n\n\n

In the three genera other than Wolffia<\/em> and Wolffiella<\/em>, crystal-containing cells develop in the fronds. In raphide cells, slender, needle-shaped calcium oxalate crystals form bundles within the vacuole. In druse cells, calcium oxalate crystals form radiating, star-shaped aggregates within the vacuole (Franceschi and Horner 1980). Calcium oxalate crystal formation is thought to contribute to the regulation of calcium concentrations in tissues, defense against herbivores, and metal detoxification (Nakata 2003). <\/p>\n\n\n\n

In Spirodela oligorhiza<\/em> and Wolffia punctata<\/em>, colorless flavans accumulate in the vacuoles of idioblasts. Upon exposure to ultraviolet radiation, these compounds are converted into reddish-brown phenolic substances, turning the idioblasts into pigment cells (Witztum 1974). Phenolic compounds are thought to screen ultraviolet radiation, protecting photosynthetic tissues and other sensitive tissues from damage (Gitz et al. 2004). However, why these compounds accumulate in only a small number of pigment cells rather than in all cells remains unclear.<\/p>\n\n\n\n

\u30a6\u30ad\u30af\u30b5\u4e9c\u79d1\u306e\u7279\u5fb4<\/strong><\/p>\n\n\n\n

6. \u30d5\u30ed\u30f3\u30c9\u306b\u6c17\u5ba4 air spaces \u3092\u5f62\u6210\u3059\u308b\u3002<\/strong><\/p>\n\n\n\n

\u30df\u30b8\u30f3\u30b3\u30a6\u30ad\u30af\u30b5\u5c5e Wolffia<\/em> \u3092\u9664\u304f\u30a6\u30ad\u30af\u30b5\u4e9c\u79d1\u306e\u5404\u5c5e\u306f\u3001\u30d5\u30ed\u30f3\u30c9\u5185\u306b\u6c17\u5ba4 air spaces \u3092\u5f62\u6210\u3059\u308b\u3002\u6c17\u5ba4\u306f\u3001\u5f62\u6210\u90e8\u4f4d\u306e\u7d30\u80de\u6b7b\u3068\u5468\u8fba\u7d30\u80de\u306e\u5206\u88c2\u304a\u3088\u3073\u4f38\u9577\u306b\u3088\u3063\u3066\u751f\u3058\u308b (Kim et al. 2024)\u3002\u5404\u6c17\u5ba4\u306f\u4e92\u3044\u306b\u3064\u306a\u304c\u308a\u3001\u5c11\u306a\u304f\u3068\u3082\u4e00\u90e8\u306f\u6c17\u5b54\u4e0b\u8154 stomatal cavity \u306b\u901a\u3058\u3066\u3044\u308b (Kim et al. 2024)\u3002\u30d5\u30ed\u30f3\u30c9\u306e\u4e0a\u9762\u306b\u306e\u307f\u5f62\u6210\u3055\u308c\u308b\u6c17\u5b54\u306f\u9589\u9396\u305b\u305a (McLaren and Smith 1976)\u3001\u5916\u6c17\u3068\u5185\u90e8\u306e\u7a7a\u9699\u3092\u5e38\u6642\u3064\u306a\u3050\u901a\u8def\u3068\u306a\u308b\u3002\u3053\u306e\u3088\u3046\u306a\u6c17\u5b54\u3068\u6c17\u5ba4\u306e\u69cb\u9020\u306f\u3001\u30ac\u30b9\u4ea4\u63db\u3084\u690d\u7269\u4f53\u306e\u6d6e\u529b\u306e\u7dad\u6301\u306b\u5bc4\u4e0e\u3059\u308b\u3068\u8003\u3048\u3089\u308c\u3066\u3044\u308b (Klich et al. 1985\u3001Kim et al. 2024)\u3002\u6c17\u5b54\u4e0b\u8154\u306f\u4ed6\u306e\u690d\u7269\u306b\u3082\u307f\u3089\u308c\u308b\u7956\u5148\u7684\u306a\u5f62\u8cea\u3068\u8003\u3048\u3089\u308c\u308b\u305f\u3081\u3001\u305d\u306e\u5f62\u6210\u6a5f\u69cb\u306e\u8ee2\u7528\u306b\u3088\u3063\u3066\u6c17\u5ba4\u304c\u9032\u5316\u3057\u3001\u6d6e\u904a\u751f\u6d3b\u3078\u306e\u9069\u5fdc\u306b\u5bc4\u4e0e\u3057\u305f\u53ef\u80fd\u6027\u304c\u3042\u308b\u3002<\/p>\n\n\n\n

\u30df\u30b8\u30f3\u30b3\u30a6\u30ad\u30af\u30b5\u5c5e Wolffia<\/em> \u306f\u3001\u690d\u7269\u306e\u5c0f\u578b\u5316\u306e\u9032\u5316\u3092\u7814\u7a76\u3059\u308b\u4e0a\u3067\u6709\u7528\u306a\u30e2\u30c7\u30eb\u3067\u3042\u308b (Yang et al. 2021)\u3002\u690d\u7269\u4f53\u306e\u5c0f\u578b\u5316\u306b\u4f34\u3063\u3066\u6839\u3084\u6c17\u5ba4\u3092\u5931\u3063\u3066\u3044\u308b\u4e00\u65b9\u3001\u6c17\u5b54\u4e0b\u8154\u306f\u5f62\u6210\u3055\u308c\u3001\u7d30\u80de\u9593\u9699\u306b\u3082\u7a7a\u6c17\u304c\u542b\u307e\u308c\u3066\u3044\u308b\u3002\u3053\u308c\u3089\u306e\u7a7a\u9699\u304c\u3001\u5c0f\u578b\u306e\u690d\u7269\u4f53\u3092\u6d6e\u304b\u305b\u308b\u306e\u306b\u5341\u5206\u306a\u6d6e\u529b\u3092\u751f\u307f\u51fa\u3057\u3066\u3044\u308b\u53ef\u80fd\u6027\u304c\u3042\u308b (Yang et al. 2021)\u3002\u307e\u305f\u3001\u690d\u7269\u4f53\u304c\u5c0f\u3055\u3044\u305f\u3081\u3001\u8868\u9762\u5f35\u529b\u3082\u6c34\u9762\u3067\u306e\u6d6e\u904a\u306b\u5bc4\u4e0e\u3059\u308b\u3068\u8003\u3048\u3089\u308c\u3066\u3044\u308b (White and Wise 1998)\u3002<\/p>\n\n\n\n

\"\"<\/a>
\u30a6\u30ad\u30af\u30b5\u4e9c\u79d1\u306e\u7279\u5fb4<\/strong>
6.\u30d5\u30ed\u30f3\u30c9\u306b\u6c17\u5ba4 air space\u3092\u5f62\u6210\u3059\u308b\u3002<\/strong>
Characteristics of Lemnoideae<\/strong>
6. Air spaces form within the fronds.<\/strong>
\u30a6\u30ad\u30af\u30b5 Spirodela polyrhiza<\/em>_10: Spirodela polyrhiza<\/em>_20261002_1, CC BY-NC. \u30a6\u30ad\u30af\u30b5 Spirodela polyrhiza<\/em>_11: Spirodela polyrhiza<\/em>_20261005_1, CC BY-NC. \u30a6\u30ad\u30af\u30b5 Spirodela polyrhiza<\/em>_12: Spirodela polyrhiza<\/em>_20261005_2, CC BY-NC. Wolffia brasiliensis<\/em>_1: Cropped a photo by Brendan O’Loughlin, https:\/\/www.inaturalist.org\/photos\/672353359, CC BY. Wolffia brasiliensis<\/em>_2: Cropped a photo by Grant Fessler, https:\/\/www.inaturalist.org\/photos\/724388074, CC BY-NC. Wolffia brasiliensis<\/em>_3: Reproduced from Hegelmaier (1868), Public Domain.<\/figcaption><\/figure>\n\n\n\n

Characteristics of Lemnoideae<\/strong><\/p>\n\n\n\n

6. Air spaces form within the fronds.<\/strong><\/p>\n\n\n\n

All genera of Lemnoideae except Wolffia<\/em> form air spaces within their fronds. These spaces develop through cell death at the sites of their formation, together with division and elongation of the surrounding cells (Kim et al. 2024). The air spaces are interconnected, and at least some communicate with substomatal cavities (Kim et al. 2024). Stomata, which occur only on the upper surface of the frond, do not close (McLaren and Smith 1976), providing continuously open passages between the atmosphere and the internal air spaces. This arrangement of stomata and air spaces is thought to facilitate gas exchange and help maintain plant buoyancy (Klich et al. 1985; Kim et al. 2024). Because substomatal cavities also occur in other plants and are considered an ancestral trait, air spaces may have evolved through the co-option of the developmental mechanisms underlying substomatal cavity formation, contributing to adaptation to a free-floating lifestyle.<\/p>\n\n\n\n

Wolffia<\/em> is a useful model for studying the evolution of plant miniaturization (Yang et al. 2021). Although roots and air spaces have been lost during miniaturization, substomatal cavities still form, and air is also present in the intercellular spaces. These spaces may provide sufficient buoyancy to support the small plant body (Yang et al. 2021). Given the small size of the plants, surface tension is also thought to contribute to flotation (White and Wise 1998).<\/p>\n\n\n\n

\u30a6\u30ad\u30af\u30b5\u79d1\u306e\u5c5e\u3078\u306e\u691c\u7d22\u8868 (Landolt, 1998\u3001Les and Crawford 1999\u3092\u53c2\u8003\u306b\u3057\u305f)<\/strong><\/p>\n\n\n\n

\uff11\uff0e\u6839\u3092\u5f62\u6210\u3059\u308b\u3002\u30d5\u30ed\u30f3\u30c9\u306b\u8449\u8108\u304c\u3067\u304d\u308b\u3002\u5b50\u30d5\u30ed\u30f3\u30c9\u3068\u82b1\u306f\u3001\u30d5\u30ed\u30f3\u30c9\u57fa\u90e8\u306e\u5de6\u53f32\u3064\u306e\u30dd\u30b1\u30c3\u30c8\u5185\u306b\u5f62\u6210\u3055\u308c\u308b\u3002\u96c4\u305a\u3044\u3068\u96cc\u305a\u3044\u306f\u819c\u8cea\u306e\u524d\u51fa\u8449\u306b\u8986\u308f\u308c\u308b\u3002\u96c4\u305a\u3044\u306f\uff12\u672c\u3067\u30014\u80de\u5b50\u56a2\u6027\u3002\u7d50\u6676\u7d30\u80de\u304c\u3042\u308b\u3002\u7a2e\u5b50\u306b\u306f\u7e26\u65b9\u5411\u306e\u808b\u304c\u3042\u308b\u3002—– 2<\/p>\n\n\n\n

\uff11\uff0e\u6839\u3092\u5f62\u6210\u3057\u306a\u3044\u3002\u30d5\u30ed\u30f3\u30c9\u306b\u8449\u8108\u304c\u3067\u304d\u306a\u3044\u3002\u5b50\u30d5\u30ed\u30f3\u30c9\u306f1\u3064\u306e\u57fa\u90e8\u30dd\u30b1\u30c3\u30c8\u307e\u305f\u306f\u7aaa\u307f\u304b\u3089\u5f62\u6210\u3055\u308c\u308b\u3002\u82b1\u306f\u30d5\u30ed\u30f3\u30c9\u4e0a\u9762\u306e\u7aaa\u307f\u306b\u5f62\u6210\u3055\u308c\u308b\u3002\u524d\u51fa\u8449\u306f\u7121\u3044\u3002\u96c4\u305a\u3044\u306f1\u672c\u306e\u307f\u3067\u30012\u80de\u5b50\u56a2\u6027\u3002\u7d50\u6676\u7d30\u80de\u3092\u6b20\u304f\u3002\u7a2e\u5b50\u306f\u307b\u307c\u5e73\u6ed1\u3067\u3042\u308b\u3002 —– 4<\/p>\n\n\n\n

2. \u6839\u306f1\u30d5\u30ed\u30f3\u30c9\u3042\u305f\u308a2\u672c\u4ee5\u4e0a\u3002\u30c9\u30eb\u30fc\u30b9\u7d30\u80de\u304c\u3042\u308b\u3002 —– 3<\/p>\n\n\n\n

2. \u6839\u306f\u5404\u30d5\u30ed\u30f3\u30c9\u306b1\u672c\u3002\u30c9\u30eb\u30fc\u30b9\u7d30\u80de\u3092\u6b20\u304f\u3002 —– Lemna<\/em><\/p>\n\n\n\n

3. \u5927\u304d\u306a\u30d5\u30ed\u30f3\u30c9\u3067\u6839\u306f2 \u2013 7\u672c(\u5e0c\u306b12\u672c)\u3002\u30d5\u30ed\u30f3\u30c9\u306f\u9577\u6955\u5186\u5f62\u307e\u305f\u306f\u72ed\u5012\u5375\u5f62\u3002—– \u30d2\u30e1\u30a6\u30ad\u30af\u30b5\u5c5e Landoltia<\/em><\/p>\n\n\n\n

3. \u5927\u304d\u306a\u30d5\u30ed\u30f3\u30c9\u3067\u6839\u306f7 \u2013 21\u672c\u3002\u30d5\u30ed\u30f3\u30c9\u306f\u5e83\u5375\u5f62\u3002—– \u30a6\u30ad\u30af\u30b5\u5c5e Spirodela<\/em><\/p>\n\n\n\n

4. \u30d5\u30ed\u30f3\u30c9\u306f\u6241\u5e73\u3002 —– Wolffiella<\/em><\/p>\n\n\n\n

4. \u30d5\u30ed\u30f3\u30c9\u306f\u7403\u5f62\u304b\u3089\u5375\u5f62\u3001\u307e\u305f\u306f\u821f\u5f62\u3002—– Wolffia<\/em><\/p>\n\n\n\n

Key to the genera of Lemnaceae<\/strong>
Based on Landolt (1998) and Les and Crawford (1999).<\/p>\n\n\n\n

1. Roots present. Fronds with veins. Daughter fronds and flowers develop within two lateral pockets at the frond base. Stamens and pistil enclosed by a membranous prophyll. Stamens two, with tetrasporangiate anthers. Crystal-containing cells present. Seeds longitudinally ribbed. \u2192 2

1 . Roots absent. Fronds without veins. Daughter fronds develop from a single basal pocket or cavity. Flowers develop in a cavity on the upper surface of the frond. Prophyll absent. Stamen solitary, with a bisporangiate anther. Crystal-containing cells absent. Seeds nearly smooth. \u2192 4<\/p>\n\n\n\n

2. Two or more roots per frond. Druse cells present. \u2192 3
2. One root per frond. Druse cells absent. \u2192 Lemna<\/em><\/p>\n\n\n\n

3. Fronds large, oblong or narrowly obovate, with 2\u20137 (rarely 12) roots. \u2192 Landoltia<\/em>
3. Fronds large, broadly ovate, with 7\u201321 roots. \u2192 Spirodela<\/em><\/p>\n\n\n\n

4. Fronds flattened. \u2192 Wolffiella<\/em>
4. Fronds globose to ovoid or boat-shaped. \u2192 Wolffia<\/em><\/p>\n\n\n\n

\u30a6\u30ad\u30af\u30b5\u4e9c\u79d1\u306e\u5c5e\u306e\u9032\u5316\u306b\u4f34\u3046\u5f62\u614b\u5f62\u8cea\u306e\u5909\u5316<\/strong><\/p>\n\n\n\n

A: \u30d5\u30ed\u30f3\u30c9\u306e\u5f62\u6210\uff1b\u30d5\u30ed\u30f3\u30c9\u306b\u7d50\u6676\u7d30\u80de\u3092\u3082\u3064\uff1b\u6839\u9798\u3092\u3082\u3064\u6839\u306e\u5f62\u6210\uff1b\u30d5\u30ed\u30f3\u30c9\u57fa\u90e8\u306e\u4e21\u5074\u306b\u5b50\u30d5\u30ed\u30f3\u30c9\u307e\u305f\u306f\u82b1\u3001\u3042\u308b\u3044\u306f\u4e21\u65b9\u3092\u5f62\u6210\uff1b\u5b50\u30d5\u30ed\u30f3\u30c9\u53ca\u3073\u82b1\u306f\u524d\u51fa\u8449\u306b\u8986\u308f\u308c\u308b\uff1b\u96c4\u305a\u3044\u306f2\u672c\u3067\u3001\u846f\u306f4\u80de\u5b50\u56a2\u6027\uff1b\u7a2e\u5b50\u306b\u7e26\u65b9\u5411\u306e\u808b\u3092\u3082\u3064<\/p>\n\n\n\n

B: \u30d5\u30ed\u30f3\u30c9\u306e\u7d50\u6676\u7d30\u80de\u306e\u6d88\u5931\uff1b\u6839\u306e\u6d88\u5931\uff1b\u30d5\u30ed\u30f3\u30c9\u57fa\u90e8\u306e1\u304b\u6240\u306b\u5b50\u30d5\u30ed\u30f3\u30c9\u3092\u5f62\u6210\uff1b\u30d5\u30ed\u30f3\u30c9\u4e0a\u9762\u306b\u82b1\u3092\u5f62\u6210\uff1b\u5b50\u30d5\u30ed\u30f3\u30c9\u3082\u82b1\u3082\u524d\u51fa\u8449\u3092\u4f34\u308f\u306a\u3044\uff1b\u96c4\u305a\u3044\u306f1\u672c\u3067\u3001\u846f\u306f2\u80de\u5b50\u56a2\u6027\uff1b\u7a2e\u5b50\u306f\u307b\u307c\u5e73\u6ed1<\/p>\n\n\n\n

\"\"<\/a>
\u30a6\u30ad\u30af\u30b5\u4e9c\u79d1\u306e\u5c5e\u306e\u9032\u5316\u306b\u4f34\u3046\u5f62\u614b\u5f62\u8cea\u306e\u5909\u5316<\/strong>
\u7cfb\u7d71\u95a2\u4fc2\u306fNauheimer et al. (2012)\u3001Ding et al. (2017)\u3001Zhao et al. (2022) \u3001\u5206\u5c90\u5e74\u4ee3\u306fNauheimer et al. (2012) \u306b\u57fa\u3065\u3044\u305f\u3002
Morphological changes during the evolution of the genera of Lemnoideae<\/strong>
Phylogenetic relationships are based on Nauheimer et al. (2012), Ding et al. (2017), and Zhao et al. (2022), and divergence times on Nauheimer et al. (2012).<\/figcaption><\/figure>\n\n\n\n

Morphological changes during the evolution of the genera of Lemnoideae<\/strong><\/p>\n\n\n\n

A: Formation of fronds; presence of crystal-containing cells in fronds; formation of roots with root sheaths; formation of daughter fronds, flowers, or both on either side of the frond base; daughter fronds and flowers enclosed by prophylls; two stamens with tetrasporangiate anthers; longitudinally ribbed seeds <\/p>\n\n\n\n

B: Loss of crystal-containing cells in fronds; loss of roots; formation of daughter fronds at a single site at the frond base; formation of flowers on the upper surface of the frond; absence of prophylls in both daughter fronds and flowers; a single stamen with a bisporangiate anther; nearly smooth seeds<\/p>\n\n\n\n

\u30a6\u30ad\u30af\u30b5\u4e9c\u79d1\u306e\u7a2e\u306e\u8b58\u5225\u306b\u7528\u3044\u3089\u308c\u308b\u5f62\u614b\u5f62\u8cea<\/strong><\/p>\n\n\n\n

\u30a6\u30ad\u30af\u30b5\u4e9c\u79d1\u306e\u540c\u5c5e\u5185\u306e\u7a2e\u306f\u3001(1) \u30d5\u30ed\u30f3\u30c9\u306e\u5f62\u3001\u5927\u304d\u3055\u3001\u8272\u3001\u539a\u3055\u3001\u4e0a\u9762\u306e\u5fae\u5c0f\u7a81\u8d77\u306e\u6709\u7121\u3001(2) \u6839\u9798\u5148\u7aef\u304c\u920d\u982d\u304b\u92ed\u982d\u304b\u3001(3) \u30d5\u30ed\u30f3\u30c9\u5074\u306b\u6b8b\u308b\u6839\u9798\u57fa\u90e8\u306e\u7ffc\u306e\u6709\u7121\u3001(4) \u4f11\u7720\u82bd turion \u3092\u5f62\u6210\u3057\u3066\u8d8a\u51ac\u3059\u308b\u304b\u3069\u3046\u304b\u3001\u306a\u3069\u306e\u5f62\u8cea\u306b\u3088\u3063\u3066\u8b58\u5225\u3055\u308c\u308b\u3002\u4f11\u7720\u82bd\u306f\u901a\u5e38\u306e\u30d5\u30ed\u30f3\u30c9\u3068\u6bd4\u3079\u3066\u5c0f\u578b\u3067\u3001\u6839\u304c\u4f38\u9577\u305b\u305a\u3001\u5927\u304d\u306a\u30c7\u30f3\u30d7\u30f3\u7c92\u3092\u84c4\u7a4d\u3057\u3001\u89aa\u30d5\u30ed\u30f3\u30c9\u304b\u3089\u96e2\u308c\u308b\u3068\u6c34\u4e2d\u306b\u6c88\u3080\u306a\u3069\u306e\u7279\u5fb4\u3092\u3082\u3064 (Hegelmaier 1868)\u3002<\/p>\n\n\n\n

\"\"<\/a>
\u30a6\u30ad\u30af\u30b5\u4e9c\u79d1\u306e\u7a2e\u306e\u8b58\u5225\u306b\u7528\u3044\u3089\u308c\u308b\u5f62\u614b\u5f62\u8cea<\/strong>
Morphological characters used to distinguish species of Lemnoideae<\/strong>
\u30a6\u30ad\u30af\u30b5 Spirodela polyrhiza<\/em>_10: Spirodela polyrhiza<\/em>_20261002_1, CC BY-NC. Spirodela intermedia<\/em>_1: Cropped a photo by Horacio Sirolli, https:\/\/www.inaturalist.org\/photos\/239311827, CC BY-NC. \u30d2\u30ca\u30a6\u30ad\u30af\u30b5 Lemna minuta<\/em>_3: Lemna minuta<\/em>_20260920_3, CC BY-NC. \u30a6\u30ad\u30af\u30b5 Spirodela polyrhiza<\/em>_12: Cropped a photo by Stefan.lefnaer, Spirodela polyrhiza sl8.jpg in Wikimedia Commons, CC BY-SA 4.0. \u30a6\u30ad\u30af\u30b5 Spirodela polyrhiza<\/em>_13: Cropped a photo by Stefan.lefnaer, Spirodela polyrhiza sl10.jpg in Wikimedia Commons, CC BY-SA 4.0. The roots were drawn based on illustrations in Hegelmaier (1868).<\/figcaption><\/figure>\n\n\n\n

Morphological characters used to distinguish species of Lemnoideae<\/strong><\/p>\n\n\n\n

Species within each genus of Lemnoideae are distinguished by such characters as (1) frond shape, size, color, thickness, and the presence or absence of minute projections on the upper surface; (2) whether the root sheath apex is obtuse or acute; (3) the presence or absence of wings on the basal portion of the root sheath remaining attached to the frond; and (4) whether turions are formed for overwintering. Compared with ordinary fronds, turions are smaller, lack elongating roots, accumulate large starch granules, and sink after detaching from the parent frond (Hegelmaier 1868).<\/p>\n\n\n\n

\u30a6\u30ad\u30af\u30b5\u5c5e<\/strong> <\/strong>Spirodela<\/em><\/strong><\/p>\n\n\n\n

\u30a6\u30ad\u30af\u30b5\u5c5e\u306f\u3001\u6975\u5730\u3084\u4e7e\u71e5\u5730\u3092\u9664\u304f\u307b\u307c\u5168\u4e16\u754c\u306b\u5206\u5e03\u3057\u30014\u7a2e\u304c\u77e5\u3089\u308c\u3066\u3044\u308b (POWO 2026)\u3002<\/p>\n\n\n\n

\"\"<\/a>
\u30a6\u30ad\u30af\u30b5\u5c5e Spirodela<\/em><\/strong>
A: \u30d5\u30ed\u30f3\u30c9\u306e\u5f62\u6210\uff1b\u30d5\u30ed\u30f3\u30c9\u306b\u7d50\u6676\u7d30\u80de\u3092\u3082\u3064\uff1b\u6839\u9798\u3092\u3082\u3064\u6839\u306e\u5f62\u6210\uff1b\u30d5\u30ed\u30f3\u30c9\u57fa\u90e8\u306e\u4e21\u5074\u306b\u5b50\u30d5\u30ed\u30f3\u30c9\u307e\u305f\u306f\u82b1\u3001\u3042\u308b\u3044\u306f\u4e21\u65b9\u3092\u5f62\u6210\uff1b\u5b50\u30d5\u30ed\u30f3\u30c9\u53ca\u3073\u82b1\u306f\u524d\u51fa\u8449\u306b\u8986\u308f\u308c\u308b\uff1b\u96c4\u305a\u3044\u306f2\u672c\u3067\u3001\u846f\u306f4\u80de\u5b50\u56a2\u6027\uff1b\u7a2e\u5b50\u306b\u7e26\u65b9\u5411\u306e\u808b\u3092\u3082\u3064
B: \u30d5\u30ed\u30f3\u30c9\u306e\u7d50\u6676\u7d30\u80de\u306e\u6d88\u5931\uff1b\u6839\u306e\u6d88\u5931\uff1b\u30d5\u30ed\u30f3\u30c9\u57fa\u90e8\u306e1\u304b\u6240\u306b\u5b50\u30d5\u30ed\u30f3\u30c9\u3092\u5f62\u6210\uff1b\u30d5\u30ed\u30f3\u30c9\u4e0a\u9762\u306b\u82b1\u3092\u5f62\u6210\uff1b\u5b50\u30d5\u30ed\u30f3\u30c9\u3082\u82b1\u3082\u524d\u51fa\u8449\u3092\u4f34\u308f\u306a\u3044\uff1b\u96c4\u305a\u3044\u306f1\u672c\u3067\u3001\u846f\u306f2\u80de\u5b50\u56a2\u6027\uff1b\u7a2e\u5b50\u306f\u307b\u307c\u5e73\u6ed1
\u7cfb\u7d71\u95a2\u4fc2\u306fNauheimer et al. (2012)\u3001Ding et al. (2017)\u3001Zhao et al. (2022) \u3001\u5206\u5c90\u5e74\u4ee3\u306fNauheimer et al. (2012) \u306b\u57fa\u3065\u3044\u305f\u3002
The genus Spirodela<\/em><\/strong>
A: Formation of fronds; presence of crystal-containing cells in fronds; formation of roots with root sheaths; formation of daughter fronds, flowers, or both on either side of the frond base; daughter fronds and flowers enclosed by prophylls; two stamens with tetrasporangiate anthers; longitudinally ribbed seeds
B: Loss of crystal-containing cells in fronds; loss of roots; formation of daughter fronds at a single site at the frond base; formation of flowers on the upper surface of the frond; absence of prophylls in both daughter fronds and flowers; a single stamen with a bisporangiate anther; nearly smooth seeds
Phylogenetic relationships are based on Nauheimer et al. (2012), Ding et al. (2017), and Zhao et al. (2022), and divergence times on Nauheimer et al. (2012).
Green indicates native areas, and purple indicates introduced areas. Source: POWO (2026). Plants of the World Online<\/em>. Facilitated by the Royal Botanic Gardens, Kew. Published on the Internet; https:\/\/powo.science.kew.org\/. Retrieved 16 Sept 2026. Distribution data from Kew Backbone Distributions (WCVP). \u00a9 World Checklist of Vascular Plants, licensed under CC BY 3.0.<\/figcaption><\/figure>\n\n\n\n

The genus <\/strong>Spirodela<\/em><\/strong><\/p>\n\n\n\n

Spirodela<\/em> has a nearly worldwide distribution, excluding polar and arid regions, and comprises four recognized species (POWO 2026).<\/p>\n\n\n\n

\u5f62\u614b (Landolt 1998)<\/strong>
\u6839<\/strong>\uff1a7\uff5e21\u672c\u3002
\u30d5\u30ed\u30f3\u30c9<\/strong>\uff1a\u5e83\u5375\u5f62\u3067\u3001\u8449\u8108\u3092\u3082\u3064\u3002\u8272\u7d20\u7d30\u80de\u3001\u30e9\u30d5\u30a3\u30c9\u7d30\u80de\u3001\u30c9\u30eb\u30fc\u30b9\u7d30\u80de\u3092\u3082\u3064\u3002\u5b50\u30d5\u30ed\u30f3\u30c9\u306e\u5f62\u6210\u6642\u306b\u524d\u51fa\u8449\u304c\u5f62\u6210\u3055\u308c\u308b\u3002
\u82b1<\/strong>\uff1a\u30d5\u30ed\u30f3\u30c9\u57fa\u90e8\u306b\u5f62\u6210\u3055\u308c\u3001\u524d\u51fa\u8449\u306b\u8986\u308f\u308c\u308b\u3002\u96c4\u305a\u3044\u306f2\u672c\u3067\u3001\u846f\u306f4\u80de\u5b50\u56a2\u6027\u3002\u96cc\u305a\u3044\u306f1\u672c\u3002
\u7a2e\u5b50<\/strong>\uff1a\u7e26\u65b9\u5411\u306e\u808b\u3092\u3082\u3064\u3002<\/p>\n\n\n\n

Spirodela intermedia<\/em> \u306f\u3001\u30a6\u30ad\u30af\u30b5 Spirodela polyrhiza<\/em> \u306b\u6bd4\u3079\u3066\u30d5\u30ed\u30f3\u30c9\u304c\u539a\u3044\u3002<\/p>\n\n\n\n

\"\"<\/a>
\u30a6\u30ad\u30af\u30b5 Spirodela polyrhiza<\/em>_10: Spirodela polyrhiza<\/em>_20261002_1, CC BY-NC. \u30a6\u30ad\u30af\u30b5 Spirodela polyrhiza<\/em>_13\u301c15: Spirodela polyrhiza<\/em>_20260911_8\u301c10, CC BY-NC. Spirodela intermedia<\/em>_1: Cropped a photo by Horacio Sirolli, https:\/\/www.inaturalist.org\/photos\/239311827, CC BY-NC. Spirodela intermedia<\/em>_2: Cropped a photo by adrianbarboza, https:\/\/www.inaturalist.org\/photos\/734081729, CC BY-NC.<\/figcaption><\/figure>\n\n\n\n

Morphology (Landolt 1998)<\/strong>
Roots<\/strong>: 7\u201321 per frond.
Fronds<\/strong>: Broadly ovate, with veins. Pigment cells, raphide cells, and druse cells present. A prophyll forms during daughter frond development.
Flowers<\/strong>: Formed at the frond base and enclosed by a prophyll. Two stamens with tetrasporangiate anthers and a single pistil.
Seeds<\/strong>: Longitudinally ribbed.<\/p>\n\n\n\n

Spirodela intermedia<\/em> has thicker fronds than Spirodela polyrhiza<\/em>.<\/p>\n\n\n\n

\u30d2\u30e1\u30a6\u30ad\u30af\u30b5\u5c5e<\/strong> <\/strong>Landoltia<\/em><\/strong><\/p>\n\n\n\n

Les and Crawford (1999) \u306f\u3001\u5f62\u614b\u3001\u30a2\u30ed\u30b6\u30a4\u30e0\u3001\u8449\u7dd1\u4f53DNA\u306e\u89e3\u6790\u306b\u57fa\u3065\u304d\u3001\u5f93\u6765 Spirodela punctata<\/em> \u3068\u3055\u308c\u3066\u3044\u305f\u7a2e\u3092\u30a6\u30ad\u30af\u30b5\u5c5e Spirodela<\/em> \u304b\u3089\u5206\u96e2\u3057\u3001\u3053\u306e1\u7a2e\u306e\u307f\u3092\u542b\u3080\u30d2\u30e1\u30a6\u30ad\u30af\u30b5\u5c5e Landoltia<\/em> \u3092\u65b0\u8a2d\u3057\u3066\u3001\u65b0\u7d44\u5408\u305b Landoltia punctata<\/em> \u3092\u767a\u8868\u3057\u305f\u3002\u305d\u306e\u5f8c\u3001\u89e3\u6790\u5bfe\u8c61\u306e\u907a\u4f1d\u5b50\u3084\u7a2e\u3092\u5897\u3084\u3057\u305f\u7814\u7a76\u3067\u3082\u3001\u30d2\u30e1\u30a6\u30ad\u30af\u30b5\u5c5e\u306f\u30a6\u30ad\u30af\u30b5\u5c5e\u306b\u3082\u30a2\u30aa\u30a6\u30ad\u30af\u30b5\u5c5e Lemna<\/em> \u306b\u3082\u542b\u307e\u308c\u306a\u3044\u72ec\u7acb\u3057\u305f\u7cfb\u7d71\u3067\u3042\u308b\u3053\u3068\u304c\u652f\u6301\u3055\u308c\u305f (Les et al. 2002\u3001Ding et al. 2017)\u3002<\/p>\n\n\n\n

\u4e00\u65b9\u3001\u3053\u306e\u690d\u7269\u306b\u9069\u7528\u3059\u308b\u5b66\u540d\u306b\u3064\u3044\u3066\u306f\u3001\u30bf\u30a4\u30d7\u6307\u5b9a\u3092\u3081\u3050\u308b\u8b70\u8ad6\u304c\u3042\u308b\u3002Ward (2011) \u306f\u3001Landoltia punctata<\/em> \u306e\u57fa\u790e\u7570\u540d basionym \u3067\u3042\u308b Lemna punctata<\/em> \u306e\u5f93\u6765\u306e\u30bf\u30a4\u30d7\u6307\u5b9a\u3092\u898b\u76f4\u3057\u3001\u30d2\u30e1\u30a6\u30ad\u30af\u30b5\u306b\u306f Spirodela oligorrhiza<\/em> \u3092\u7528\u3044\u308b\u3079\u304d\u3067\u3042\u308b\u3068\u3057\u305f\u3002\u3053\u308c\u306b\u5bfe\u3057\u3001Wiersema (2015) \u306f\u3001\u3053\u306e\u518d\u30bf\u30a4\u30d7\u6307\u5b9a\u3092\u8a8d\u3081\u308b\u3079\u304d\u3067\u306f\u306a\u3044\u3068\u8ad6\u3058\u3001\u5f93\u6765\u3069\u304a\u308a\u306e\u610f\u5473\u3067 Landoltia punctata<\/em> \u3092\u4f7f\u7528\u3059\u308b\u3053\u3068\u3092\u652f\u6301\u3057\u305f\u3002<\/p>\n\n\n\n

\u73fe\u5728\u306ePOWO\u3067\u306f\u3001\u30d2\u30e1\u30a6\u30ad\u30af\u30b5\u306b\u76f8\u5f53\u3059\u308b\u690d\u7269\u306f Spirodela oligorrhiza<\/em> \u3068\u3057\u3066\u6271\u308f\u308c\u3066\u3044\u308b\u3002\u3053\u306e\u690d\u7269\u306f\u3001\u30a2\u30b8\u30a2\u306e\u71b1\u5e2f\u304a\u3088\u3073\u4e9c\u71b1\u5e2f\u304b\u3089\u5357\u897f\u592a\u5e73\u6d0b\u57df\u3001\u30a2\u30d5\u30ea\u30ab\u5357\u90e8\u306e\u71b1\u5e2f\u57df\u304b\u3089\u5357\u90e8\u30a2\u30d5\u30ea\u30ab\u3001\u304a\u3088\u3073\u30de\u30c0\u30ac\u30b9\u30ab\u30eb\u306a\u3069\u306e\u897f\u30a4\u30f3\u30c9\u6d0b\u57df\u306b\u81ea\u751f\u3057\u3001\u5357\u5317\u30a2\u30e1\u30ea\u30ab\u3084\u30e8\u30fc\u30ed\u30c3\u30d1\u306a\u3069\u306b\u79fb\u5165\u3055\u308c\u3066\u3044\u308b (POWO)\u3002<\/p>\n\n\n\n

\"\"<\/a>
\u30d2\u30e1\u30a6\u30ad\u30af\u30b5\u5c5e Landoltia<\/em><\/strong>
A: \u30d5\u30ed\u30f3\u30c9\u306e\u5f62\u6210\uff1b\u30d5\u30ed\u30f3\u30c9\u306b\u7d50\u6676\u7d30\u80de\u3092\u3082\u3064\uff1b\u6839\u9798\u3092\u3082\u3064\u6839\u306e\u5f62\u6210\uff1b\u30d5\u30ed\u30f3\u30c9\u57fa\u90e8\u306e\u4e21\u5074\u306b\u5b50\u30d5\u30ed\u30f3\u30c9\u307e\u305f\u306f\u82b1\u3001\u3042\u308b\u3044\u306f\u4e21\u65b9\u3092\u5f62\u6210\uff1b\u5b50\u30d5\u30ed\u30f3\u30c9\u53ca\u3073\u82b1\u306f\u524d\u51fa\u8449\u306b\u8986\u308f\u308c\u308b\uff1b\u96c4\u305a\u3044\u306f2\u672c\u3067\u3001\u846f\u306f4\u80de\u5b50\u56a2\u6027\uff1b\u7a2e\u5b50\u306b\u7e26\u65b9\u5411\u306e\u808b\u3092\u3082\u3064
B: \u30d5\u30ed\u30f3\u30c9\u306e\u7d50\u6676\u7d30\u80de\u306e\u6d88\u5931\uff1b\u6839\u306e\u6d88\u5931\uff1b\u30d5\u30ed\u30f3\u30c9\u57fa\u90e8\u306e1\u304b\u6240\u306b\u5b50\u30d5\u30ed\u30f3\u30c9\u3092\u5f62\u6210\uff1b\u30d5\u30ed\u30f3\u30c9\u4e0a\u9762\u306b\u82b1\u3092\u5f62\u6210\uff1b\u5b50\u30d5\u30ed\u30f3\u30c9\u3082\u82b1\u3082\u524d\u51fa\u8449\u3092\u4f34\u308f\u306a\u3044\uff1b\u96c4\u305a\u3044\u306f1\u672c\u3067\u3001\u846f\u306f2\u80de\u5b50\u56a2\u6027\uff1b\u7a2e\u5b50\u306f\u307b\u307c\u5e73\u6ed1
\u7cfb\u7d71\u95a2\u4fc2\u306fNauheimer et al. (2012)\u3001Ding et al. (2017)\u3001Zhao et al. (2022) \u3001\u5206\u5c90\u5e74\u4ee3\u306fNauheimer et al. (2012) \u306b\u57fa\u3065\u3044\u305f\u3002
The genus Landoltia<\/em><\/strong>
A: Formation of fronds; presence of crystal-containing cells in fronds; formation of roots with root sheaths; formation of daughter fronds, flowers, or both on either side of the frond base; daughter fronds and flowers enclosed by prophylls; two stamens with tetrasporangiate anthers; longitudinally ribbed seeds
B: Loss of crystal-containing cells in fronds; loss of roots; formation of daughter fronds at a single site at the frond base; formation of flowers on the upper surface of the frond; absence of prophylls in both daughter fronds and flowers; a single stamen with a bisporangiate anther; nearly smooth seeds
Green indicates native areas, and purple indicates introduced areas. Source: POWO (2026). Plants of the World Online<\/em>. Facilitated by the Royal Botanic Gardens, Kew. Published on the Internet; https:\/\/powo.science.kew.org\/. Retrieved 16 Sept 2026. Distribution data from Kew Backbone Distributions (WCVP). \u00a9 World Checklist of Vascular Plants, licensed under CC BY 3.0.<\/figcaption><\/figure>\n\n\n\n

The genus <\/strong>Landoltia<\/em><\/strong><\/p>\n\n\n\n

Based on analyses of morphology, allozymes, and chloroplast DNA, Les and Crawford (1999) segregated the species previously known as Spirodela punctata<\/em> from Spirodela<\/em>, established the monotypic genus Landoltia<\/em>, and published the new combination Landoltia punctata<\/em>. Subsequent studies with broader gene and taxon sampling also supported Landoltia<\/em> as a distinct lineage outside both Spirodela<\/em> and Lemna<\/em> (Les et al. 2002; Ding et al. 2017).<\/p>\n\n\n\n

However, the scientific name applicable to this plant has been debated because of differing interpretations of its typification. Ward (2011) reconsidered the previous typification of Lemna punctata<\/em>, the basionym of Landoltia punctata<\/em>, and argued that Spirodela oligorrhiza<\/em> should be used for this plant. In contrast, Wiersema (2015) argued against accepting this retypification and supported the continued use of Landoltia punctata<\/em> in its established sense.<\/p>\n\n\n\n

POWO currently treats this plant as Spirodela oligorrhiza<\/em>. It is native to tropical and subtropical Asia through the southwestern Pacific, southern tropical Africa through southern Africa, and the western Indian Ocean region, including Madagascar. It has been introduced to North and South America, Europe, and other regions (POWO).<\/p>\n\n\n\n

\u5f62\u614b (Landolt 1998)<\/strong>
\u6839<\/strong>\uff1a1\uff5e7\u672c (\u307e\u308c\u306b12\u672c)\u3002
\u30d5\u30ed\u30f3\u30c9<\/strong>\uff1a\u9577\u6955\u5186\u5f62\u307e\u305f\u306f\u72ed\u5012\u5375\u5f62\u3067\u3001\u8449\u8108\u3092\u3082\u3064\u3002\u8272\u7d20\u7d30\u80de\u3001\u30e9\u30d5\u30a3\u30c9\u7d30\u80de\u3001\u30c9\u30eb\u30fc\u30b9\u7d30\u80de\u3092\u3082\u3064\u3002\u5b50\u30d5\u30ed\u30f3\u30c9\u306e\u5f62\u6210\u6642\u306b\u524d\u51fa\u8449\u304c\u5f62\u6210\u3055\u308c\u308b\u3002
\u82b1<\/strong>\uff1a\u30d5\u30ed\u30f3\u30c9\u57fa\u90e8\u306b\u5f62\u6210\u3055\u308c\u3001\u524d\u51fa\u8449\u306b\u8986\u308f\u308c\u308b\u3002\u96c4\u305a\u3044\u306f2\u672c\u3067\u3001\u846f\u306f4\u80de\u5b50\u56a2\u6027\u3002\u96cc\u305a\u3044\u306f1\u672c\u3002
\u7a2e\u5b50<\/strong>\uff1a\u7e26\u65b9\u5411\u306e\u808b\u3092\u3082\u3064\u3002<\/p>\n\n\n\n

\u30d2\u30e1\u30a6\u30ad\u30af\u30b5\u5c5e Landoltia<\/em> \u306f\u3001\u5206\u5b50\u7cfb\u7d71\u89e3\u6790\u306b\u3088\u308a\u3001\u30a6\u30ad\u30af\u30b5\u5c5e\u3068\u5408\u308f\u305b\u3066\u3082\u5358\u7cfb\u7d71\u7fa4\u3092\u5f62\u6210\u3057\u306a\u3044\u3053\u3068\u304c\u793a\u3055\u308c\u3066\u3044\u308b\u3002\u5f62\u614b\u7684\u306b\u306f\u3001\u30d5\u30ed\u30f3\u30c9\u306e\u5f62\u3084\u3001\u5927\u304d\u306a\u30d5\u30ed\u30f3\u30c9\u3067\u3082\u30a6\u30ad\u30af\u30b5\u5c5e\u3088\u308a\u6839\u306e\u6570\u304c\u5c11\u306a\u3044\u3053\u3068\u306b\u3088\u3063\u3066\u533a\u5225\u3055\u308c\u308b (Les and Crawford 1999)\u3002\u5199\u771f\u3067\u306f\u3001\u6839\u306e\u57fa\u90e8\u306b\u6b8b\u308b\u6839\u9798\u306e\u4e00\u90e8\u304c\u898b\u3048\u308b\u3002<\/p>\n\n\n\n

\"\"<\/a>
\u30d2\u30e1\u30a6\u30ad\u30af\u30b5 Landoltia punctata<\/em>_2: Landoltia punctata<\/em>_20140425_2, CC BY-NC.
\u30d2\u30e1\u30a6\u30ad\u30af\u30b5 Landoltia punctata<\/em>_3: Landoltia punctata<\/em>_20140425_3, CC BY-NC.<\/figcaption><\/figure>\n\n\n\n

Morphology (Landolt 1998)<\/strong>
Roots<\/strong>: 1\u20137 (rarely 12) per frond.
Fronds<\/strong>: Oblong or narrowly obovate, with veins. Pigment cells, raphide cells, and druse cells present. A prophyll forms during daughter frond development.
Flowers<\/strong>: Formed at the frond base and enclosed by a prophyll. Two stamens with tetrasporangiate anthers and a single pistil.
Seeds<\/strong>: Longitudinally ribbed.<\/p>\n\n\n\n

Molecular phylogenetic analyses have shown that Landoltia<\/em> and Spirodela<\/em> together do not form a monophyletic group. Morphologically, Landoltia<\/em> is distinguished from Spirodela<\/em> by its frond shape and fewer roots, even on large fronds (Les and Crawford 1999). In the photograph, remnants of the root sheaths are visible at the root bases.<\/p>\n\n\n\n

\u30a2\u30aa\u30a6\u30ad\u30af\u30b5\u5c5e Lemna<\/em><\/strong> <\/p>\n\n\n\n

\u30a2\u30aa\u30a6\u30ad\u30af\u30b5\u5c5e\u306f\u3001\u6975\u5730\u3084\u4e7e\u71e5\u5730\u3092\u9664\u304f\u307b\u307c\u5168\u4e16\u754c\u306b\u5206\u5e03\u3057\u300113\u7a2e\u304c\u77e5\u3089\u308c\u3066\u3044\u308b (POWO)\u3002<\/p>\n\n\n\n

\"\"<\/a>
\u30a2\u30aa\u30a6\u30ad\u30af\u30b5\u5c5e Lemna<\/em><\/strong>
A: \u30d5\u30ed\u30f3\u30c9\u306e\u5f62\u6210\uff1b\u30d5\u30ed\u30f3\u30c9\u306b\u7d50\u6676\u7d30\u80de\u3092\u3082\u3064\uff1b\u6839\u9798\u3092\u3082\u3064\u6839\u306e\u5f62\u6210\uff1b\u30d5\u30ed\u30f3\u30c9\u57fa\u90e8\u306e\u4e21\u5074\u306b\u5b50\u30d5\u30ed\u30f3\u30c9\u307e\u305f\u306f\u82b1\u3001\u3042\u308b\u3044\u306f\u4e21\u65b9\u3092\u5f62\u6210\uff1b\u5b50\u30d5\u30ed\u30f3\u30c9\u53ca\u3073\u82b1\u306f\u524d\u51fa\u8449\u306b\u8986\u308f\u308c\u308b\uff1b\u96c4\u305a\u3044\u306f2\u672c\u3067\u3001\u846f\u306f4\u80de\u5b50\u56a2\u6027\uff1b\u7a2e\u5b50\u306b\u7e26\u65b9\u5411\u306e\u808b\u3092\u3082\u3064
B: \u30d5\u30ed\u30f3\u30c9\u306e\u7d50\u6676\u7d30\u80de\u306e\u6d88\u5931\uff1b\u6839\u306e\u6d88\u5931\uff1b\u30d5\u30ed\u30f3\u30c9\u57fa\u90e8\u306e1\u304b\u6240\u306b\u5b50\u30d5\u30ed\u30f3\u30c9\u3092\u5f62\u6210\uff1b\u30d5\u30ed\u30f3\u30c9\u4e0a\u9762\u306b\u82b1\u3092\u5f62\u6210\uff1b\u5b50\u30d5\u30ed\u30f3\u30c9\u3082\u82b1\u3082\u524d\u51fa\u8449\u3092\u4f34\u308f\u306a\u3044\uff1b\u96c4\u305a\u3044\u306f1\u672c\u3067\u3001\u846f\u306f2\u80de\u5b50\u56a2\u6027\uff1b\u7a2e\u5b50\u306f\u307b\u307c\u5e73\u6ed1
\u7cfb\u7d71\u95a2\u4fc2\u306fNauheimer et al. (2012)\u3001Ding et al. (2017)\u3001Zhao et al. (2022) \u3001\u5206\u5c90\u5e74\u4ee3\u306fNauheimer et al. (2012) \u306b\u57fa\u3065\u3044\u305f\u3002
The genus Lemna<\/em><\/strong>
A: Formation of fronds; presence of crystal-containing cells in fronds; formation of roots with root sheaths; formation of daughter fronds, flowers, or both on either side of the frond base; daughter fronds and flowers enclosed by prophylls; two stamens with tetrasporangiate anthers; longitudinally ribbed seeds
B: Loss of crystal-containing cells in fronds; loss of roots; formation of daughter fronds at a single site at the frond base; formation of flowers on the upper surface of the frond; absence of prophylls in both daughter fronds and flowers; a single stamen with a bisporangiate anther; nearly smooth seeds
Phylogenetic relationships are based on Nauheimer et al. (2012), Ding et al. (2017), and Zhao et al. (2022), and divergence times on Nauheimer et al. (2012).
Green indicates native areas, and purple indicates introduced areas. Source: POWO (2026). Plants of the World Online<\/em>. Facilitated by the Royal Botanic Gardens, Kew. Published on the Internet; https:\/\/powo.science.kew.org\/. Retrieved 16 Sept 2026. Distribution data from Kew Backbone Distributions (WCVP). \u00a9 World Checklist of Vascular Plants, licensed under CC BY 3.0.<\/figcaption><\/figure>\n\n\n\n

The genus Lemna<\/em><\/strong><\/p>\n\n\n\n

Lemna<\/em> has a nearly worldwide distribution, excluding polar and arid regions, and comprises 13 recognized species (POWO).<\/p>\n\n\n\n

\u5f62\u614b (Landolt 1998)<\/strong>
\u6839<\/strong>\uff1a1\u672c\u3002
\u30d5\u30ed\u30f3\u30c9<\/strong>\uff1a\u9577\u6955\u5186\u5f62\u307e\u305f\u306f\u72ed\u5012\u5375\u5f62\u3067\u3001\u8449\u8108\u3092\u3082\u3064\u3002\u8272\u7d20\u7d30\u80de\u3068\u30c9\u30eb\u30fc\u30b9\u7d30\u80de\u3092\u6b20\u304f\u304c\u3001\u30e9\u30d5\u30a3\u30c9\u7d30\u80de\u3092\u3082\u3064\u3002\u5b50\u30d5\u30ed\u30f3\u30c9\u306e\u5f62\u6210\u6642\u306b\u524d\u51fa\u8449\u306f\u5f62\u6210\u3055\u308c\u306a\u3044\u3002
\u82b1<\/strong>\uff1a\u30d5\u30ed\u30f3\u30c9\u57fa\u90e8\u306b\u5f62\u6210\u3055\u308c\u3001\u524d\u51fa\u8449\u306b\u8986\u308f\u308c\u308b\u3002\u96c4\u305a\u3044\u306f2\u672c\u3067\u3001\u846f\u306f4\u80de\u5b50\u56a2\u6027\u3002\u96cc\u305a\u3044\u306f1\u672c\u3002
\u7a2e\u5b50<\/strong>\uff1a\u7e26\u65b9\u5411\u306e\u808b\u3092\u3082\u3064\u3002<\/p>\n\n\n\n

\"\"<\/a>
\u5de6\u306e\u5199\u771f\u3067\u306f\u3001\u5927\u304d\u306a\u30d5\u30ed\u30f3\u30c9\u306f\u30a6\u30ad\u30af\u30b5 Spirodela polyrhiza<\/em>\u3001\u5c0f\u3055\u306a\u30d5\u30ed\u30f3\u30c9\u306f\u30d2\u30ca\u30a6\u30ad\u30af\u30b5 Lemna minuta <\/em>\u3067\u3042\u308b\u3002
In the photograph on the left, the large fronds are Spirodela polyrhiza<\/em>, and the small fronds are Lemna minuta<\/em>.
\u30d2\u30ca\u30a6\u30ad\u30af\u30b5 Lemna minuta<\/em>_4: Lemna minuta<\/em>_20260920_4, CC BY-NC.
\u30d2\u30ca\u30a6\u30ad\u30af\u30b5 Lemna minuta<\/em>_5: Lemna minuta<\/em>_20260920_5, CC BY-NC.<\/figcaption><\/figure>\n\n\n\n

Morphology (Landolt 1998)<\/strong>
Roots<\/strong>: One per frond.
Fronds<\/strong>: Oblong or narrowly obovate, with veins. Pigment cells and druse cells absent; raphide cells present. No prophyll forms during daughter frond development.
Flowers<\/strong>: Formed at the frond base and enclosed by a prophyll. Two stamens with tetrasporangiate anthers and a single pistil.
Seeds<\/strong>: Longitudinally ribbed.<\/p>\n\n\n\n

\u30d2\u30f3\u30b8\u30e2\u306f\u3001\u30a6\u30ad\u30af\u30b5\u4e9c\u79d1\u306e\u4ed6\u306e\u7a2e\u3068\u540c\u69d8\u306b\u3001\u89aa\u30d5\u30ed\u30f3\u30c9\u306e\u57fa\u90e8\u304b\u3089\u5b50\u30d5\u30ed\u30f3\u30c9\u3092\u5f62\u6210\u3059\u308b\u3002\u3057\u304b\u3057\u3001\u4e21\u8005\u3092\u3064\u306a\u3050\u67c4 stipe \u304c\u30d5\u30ed\u30f3\u30c9\u3088\u308a\u3082\u9577\u304f\u4f38\u9577\u3057\u3001\u5bbf\u5b58\u3057\u3066\u30d5\u30ed\u30f3\u30c9\u540c\u58eb\u3092\u3064\u306a\u304e\u7d9a\u3051\u308b\u3053\u3068\u3084\u3001\u6c34\u4e2d\u306b\u6c88\u3093\u3067\u751f\u80b2\u3059\u308b\u70b9\u3067\u7279\u7570\u3067\u3042\u308b\u3002\u82b1\u3092\u3064\u3051\u308b\u30d5\u30ed\u30f3\u30c9\u306f\u6c34\u9762\u306b\u6d6e\u4e0a\u3059\u308b\u3002\u679c\u76ae\u306f\u8584\u304f\u3001\u7a2e\u5b50\u306e\u7e26\u65b9\u5411\u306e\u808b\u304c\u900f\u3051\u3066\u898b\u3048\u308b\u3002<\/p>\n\n\n\n

\"\"<\/a>
\u30d2\u30f3\u30b8\u30e2 Lemna trisulca<\/em>_1: Lemna trisulca<\/em>_260429_1, CC BY-NC. \u30d2\u30f3\u30b8\u30e2 Lemna trisulca<\/em>_2: Cropped a photo by Peter Ownbey, https:\/\/www.inaturalist.org\/photos\/737395508, CC BY-NC. \u30d2\u30f3\u30b8\u30e2 Lemna trisulca<\/em>_3: Reproduced from den Hartog (1964), CC BY 4.0.<\/figcaption><\/figure>\n\n\n\n

Like other members of Lemnoideae, Lemna trisulca<\/em> produces daughter fronds at the base of the parent frond. It is distinctive, however, in having connecting stipes that grow longer than the fronds and persist, keeping successive fronds attached, and in growing submerged. Flower-bearing fronds rise to the water surface. The pericarp is thin, allowing the longitudinal ribs of the seed to be seen through it.<\/p>\n\n\n\n

\u30a6\u30a9\u30eb\u30d5\u30a3\u30a8\u30e9\u5c5e <\/strong>Wolffiella<\/em><\/strong><\/p>\n\n\n\n

\u30a6\u30a9\u30eb\u30d5\u30a3\u30a8\u30e9\u5c5e\u306b\u306f10\u7a2e\u304c\u77e5\u3089\u308c\u3066\u304a\u308a\u30011\u7a2e\u306f\u5317\u30a2\u30e1\u30ea\u30ab\u306e\u307f\u30012\u7a2e\u306f\u5357\u30a2\u30e1\u30ea\u30ab\u306e\u307f\u30012\u7a2e\u306f\u5357\u5317\u30a2\u30e1\u30ea\u30ab\u30011\u7a2e\u306f\u5357\u5317\u30a2\u30e1\u30ea\u30ab\u3068\u30a2\u30d5\u30ea\u30ab\u306b\u5206\u5e03\u3059\u308b\u3002\u6b8b\u308b4\u7a2e\u306f\u30a2\u30d5\u30ea\u30ab\u306b\u5206\u5e03\u3057\u3001\u305d\u306e\u3046\u30611\u7a2e\u306e W. hyalina<\/em> \u306f\u30a2\u30e9\u30d3\u30a2\u534a\u5cf6\u306b\u3082\u5206\u5e03\u3059\u308b\u307b\u304b\u3001\u30a4\u30f3\u30c9\u306b\u79fb\u5165\u3055\u308c\u3066\u3044\u308b (POWO 2026)\u3002<\/p>\n\n\n\n

\"\"<\/a>
\u30a6\u30a9\u30eb\u30d5\u30a3\u30a8\u30e9\u5c5e Wolffiella<\/em><\/strong>
A: \u30d5\u30ed\u30f3\u30c9\u306e\u5f62\u6210\uff1b\u30d5\u30ed\u30f3\u30c9\u306b\u7d50\u6676\u7d30\u80de\u3092\u3082\u3064\uff1b\u6839\u9798\u3092\u3082\u3064\u6839\u306e\u5f62\u6210\uff1b\u30d5\u30ed\u30f3\u30c9\u57fa\u90e8\u306e\u4e21\u5074\u306b\u5b50\u30d5\u30ed\u30f3\u30c9\u307e\u305f\u306f\u82b1\u3001\u3042\u308b\u3044\u306f\u4e21\u65b9\u3092\u5f62\u6210\uff1b\u5b50\u30d5\u30ed\u30f3\u30c9\u53ca\u3073\u82b1\u306f\u524d\u51fa\u8449\u306b\u8986\u308f\u308c\u308b\uff1b\u96c4\u305a\u3044\u306f2\u672c\u3067\u3001\u846f\u306f4\u80de\u5b50\u56a2\u6027\uff1b\u7a2e\u5b50\u306b\u7e26\u65b9\u5411\u306e\u808b\u3092\u3082\u3064
B: \u30d5\u30ed\u30f3\u30c9\u306e\u7d50\u6676\u7d30\u80de\u306e\u6d88\u5931\uff1b\u6839\u306e\u6d88\u5931\uff1b\u30d5\u30ed\u30f3\u30c9\u57fa\u90e8\u306e1\u304b\u6240\u306b\u5b50\u30d5\u30ed\u30f3\u30c9\u3092\u5f62\u6210\uff1b\u30d5\u30ed\u30f3\u30c9\u4e0a\u9762\u306b\u82b1\u3092\u5f62\u6210\uff1b\u5b50\u30d5\u30ed\u30f3\u30c9\u3082\u82b1\u3082\u524d\u51fa\u8449\u3092\u4f34\u308f\u306a\u3044\uff1b\u96c4\u305a\u3044\u306f1\u672c\u3067\u3001\u846f\u306f2\u80de\u5b50\u56a2\u6027\uff1b\u7a2e\u5b50\u306f\u307b\u307c\u5e73\u6ed1
\u7cfb\u7d71\u95a2\u4fc2\u306fNauheimer et al. (2012)\u3001Ding et al. (2017)\u3001Zhao et al. (2022) \u3001\u5206\u5c90\u5e74\u4ee3\u306fNauheimer et al. (2012) \u306b\u57fa\u3065\u3044\u305f\u3002
The genus Wolffiella<\/em><\/strong>
A: Formation of fronds; presence of crystal-containing cells in fronds; formation of roots with root sheaths; formation of daughter fronds, flowers, or both on either side of the frond base; daughter fronds and flowers enclosed by prophylls; two stamens with tetrasporangiate anthers; longitudinally ribbed seeds
B: Loss of crystal-containing cells in fronds; loss of roots; formation of daughter fronds at a single site at the frond base; formation of flowers on the upper surface of the frond; absence of prophylls in both daughter fronds and flowers; a single stamen with a bisporangiate anther; nearly smooth seeds
Green indicates native areas, and purple indicates introduced areas. Source: POWO (2026). Plants of the World Online<\/em>. Facilitated by the Royal Botanic Gardens, Kew. Published on the Internet; https:\/\/powo.science.kew.org\/. Retrieved 16 Sept 2026. Distribution data from Kew Backbone Distributions (WCVP). \u00a9 World Checklist of Vascular Plants, licensed under CC BY 3.0.<\/figcaption><\/figure>\n\n\n\n

The genus <\/strong>Wolffiella<\/em><\/strong><\/p>\n\n\n\n

Wolffiella<\/em> comprises 10 recognized species: one occurs only in North America, two only in South America, two in both North and South America, and one in North and South America and Africa. The remaining four species occur in Africa; one of these, W. hyalina<\/em>, also occurs in the Arabian Peninsula and has been introduced to India (POWO 2026). The spelling of the scientific name has been corrected from W. hyaline<\/em> to W. hyalina<\/em>.<\/p>\n\n\n\n

\u5f62\u614b (Landolt 1998)<\/strong>
\u6839<\/strong>\uff1a\u306a\u3057\u3002
\u30d5\u30ed\u30f3\u30c9<\/strong>\uff1a\u8584\u304f\u3001\u5186\u5f62\u3001\u9577\u6955\u5186\u5f62\u3001\u7dda\u5f62\u3001\u307e\u305f\u306f\u938c\u5f62\u3002
\u82b1<\/strong>\uff1a\u30d5\u30ed\u30f3\u30c9\u4e0a\u9762\u306b\u5f62\u6210\u3055\u308c\u308b\u3002\u96c4\u305a\u3044\u306f1\u672c\u3067\u3001\u846f\u306f2\u80de\u5b50\u56a2\u6027\u3002\u96cc\u305a\u3044\u306f1\u672c\u3002
\u7a2e\u5b50<\/strong>\uff1a\u8868\u9762\u306f\u307b\u307c\u5e73\u6ed1\u3002<\/p>\n\n\n\n

\"\"<\/a>
Wolffiella welwitschii<\/em>_1: Cropped a photo by Guillaume L\u00e9otard, https:\/\/www.inaturalist.org\/photos\/630136109, CC BY-NC. Wolffiella welwitschii<\/em>_2: Cropped a photo by Robert Taylor, https:\/\/www.inaturalist.org\/photos\/94584291, CC BY. Wolffiella welwitschii<\/em>_3: Reproduced from Hegelmaier (1868), Public Domain. Wolffiella lingulata<\/em>_1: Cropped a photo by vinicius_s_domingues, https:\/\/www.inaturalist.org\/photos\/223378026, CC BY. Wolffiella gladiata<\/em>_1: Cropped a photo by Keith Bradley, https:\/\/www.inaturalist.org\/photos\/501132316, CC BY-NC. Wolffiella lingulata<\/em>_2: Reproduced from Mason (1938), CC BY-NC 3.0.<\/figcaption><\/figure>\n\n\n\n

Morphology (Landolt 1998)<\/strong>
Roots<\/strong>: Absent.
Fronds<\/strong>: Thin; circular, oblong, linear, or falcate.
Flowers<\/strong>: Formed on the upper surface of the frond. A single stamen with a bisporangiate anther and a single pistil.
Seeds<\/strong>: Surface nearly smooth.<\/p>\n\n\n\n

Wolffiella gladiata<\/em> \u3084 W. lingulata<\/em> \u3067\u306f\u3001\u30d5\u30ed\u30f3\u30c9\u304c\u53e2\u751f\u72b6\u306b\u306a\u308b\u3053\u3068\u304c\u3042\u308b\u3002\u89aa\u30d5\u30ed\u30f3\u30c9\u3068\u5b50\u30d5\u30ed\u30f3\u30c9\u306f\u77ed\u3044\u67c4\u3067\u3064\u306a\u304c\u3063\u3066\u304a\u308a\u3001\u67c4\u304c\u5207\u308c\u308b\u524d\u306b\u89aa\u30d5\u30ed\u30f3\u30c9\u304c2\u756a\u76ee\u306e\u5b50\u30d5\u30ed\u30f3\u30c9\u3092\u5f62\u6210\u3057\u3001\u5148\u306b\u5f62\u6210\u3055\u308c\u305f\u5b50\u30d5\u30ed\u30f3\u30c9\u3082\u6b21\u4e16\u4ee3\u306e\u30d5\u30ed\u30f3\u30c9\u3092\u5f62\u6210\u3059\u308b (Wolffiella lingulata<\/em>_6\u306e\u56f3\u53c2\u7167)\u3002\u3053\u306e\u904e\u7a0b\u304c\u7e70\u308a\u8fd4\u3055\u308c\u308b\u3053\u3068\u3067\u3001\u591a\u6570\u306e\u30d5\u30ed\u30f3\u30c9\u304c\u3064\u306a\u304c\u3063\u305f\u53e2\u751f\u72b6\u306e\u5f62\u614b\u3068\u306a\u308b\u3002<\/p>\n\n\n\n

\"\"<\/a>
Wolffiella gladiata<\/em>_2: Cropped a photo by Tom\u00e1s Curtis, https:\/\/www.inaturalist.org\/photos\/140600912, CC BY-NC. Wolffiella lingulata<\/em>_3: Cropped a photo by Thomaz Ricardo Favreto Sinani, https:\/\/www.inaturalist.org\/photos\/463819443, CC BY. Wolffiella lingulata<\/em>_4: Cropped a photo by James K. Wetterer, https:\/\/www.inaturalist.org\/photos\/616533942, CC BY-NC. Wolffiella lingulata<\/em>_5\u301c8: Reproduced from Mason (1938), CC BY-NC 3.0.<\/figcaption><\/figure>\n\n\n\n

In Wolffiella gladiata<\/em> and W. lingulata<\/em>, fronds sometimes form dense clusters. Parent and daughter fronds are connected by short stipes. Before these connections break, the parent frond produces a second daughter frond, while the first daughter frond also produces a frond of the next generation (see figure Wolffiella lingulata<\/em>_6). Repetition of this process results in a dense cluster of interconnected fronds.<\/p>\n\n\n\n

\u30df\u30b8\u30f3\u30b3\u30a6\u30ad\u30af\u30b5\u5c5e <\/strong>Wolffia<\/em><\/strong><\/p>\n\n\n\n

\u30df\u30b8\u30f3\u30b3\u30a6\u30ad\u30af\u30b5\u5c5e\u306b\u306f11\u7a2e\u304c\u77e5\u3089\u308c\u3066\u304a\u308a\u3001\u305d\u306e\u3046\u30613\u7a2e\u306f\u8907\u6570\u306e\u5927\u9678\u306b\u5206\u5e03\u3059\u308b (POWO 2026)\u3002<\/p>\n\n\n\n

\"\"<\/a>
\u30df\u30b8\u30f3\u30b3\u30a6\u30ad\u30af\u30b5\u5c5e Wolffia<\/em><\/strong>
A: \u30d5\u30ed\u30f3\u30c9\u306e\u5f62\u6210\uff1b\u30d5\u30ed\u30f3\u30c9\u306b\u7d50\u6676\u7d30\u80de\u3092\u3082\u3064\uff1b\u6839\u9798\u3092\u3082\u3064\u6839\u306e\u5f62\u6210\uff1b\u30d5\u30ed\u30f3\u30c9\u57fa\u90e8\u306e\u4e21\u5074\u306b\u5b50\u30d5\u30ed\u30f3\u30c9\u307e\u305f\u306f\u82b1\u3001\u3042\u308b\u3044\u306f\u4e21\u65b9\u3092\u5f62\u6210\uff1b\u5b50\u30d5\u30ed\u30f3\u30c9\u53ca\u3073\u82b1\u306f\u524d\u51fa\u8449\u306b\u8986\u308f\u308c\u308b\uff1b\u96c4\u305a\u3044\u306f2\u672c\u3067\u3001\u846f\u306f4\u80de\u5b50\u56a2\u6027\uff1b\u7a2e\u5b50\u306b\u7e26\u65b9\u5411\u306e\u808b\u3092\u3082\u3064
B: \u30d5\u30ed\u30f3\u30c9\u306e\u7d50\u6676\u7d30\u80de\u306e\u6d88\u5931\uff1b\u6839\u306e\u6d88\u5931\uff1b\u30d5\u30ed\u30f3\u30c9\u57fa\u90e8\u306e1\u304b\u6240\u306b\u5b50\u30d5\u30ed\u30f3\u30c9\u3092\u5f62\u6210\uff1b\u30d5\u30ed\u30f3\u30c9\u4e0a\u9762\u306b\u82b1\u3092\u5f62\u6210\uff1b\u5b50\u30d5\u30ed\u30f3\u30c9\u3082\u82b1\u3082\u524d\u51fa\u8449\u3092\u4f34\u308f\u306a\u3044\uff1b\u96c4\u305a\u3044\u306f1\u672c\u3067\u3001\u846f\u306f2\u80de\u5b50\u56a2\u6027\uff1b\u7a2e\u5b50\u306f\u307b\u307c\u5e73\u6ed1
\u7cfb\u7d71\u95a2\u4fc2\u306fNauheimer et al. (2012)\u3001Ding et al. (2017)\u3001Zhao et al. (2022) \u3001\u5206\u5c90\u5e74\u4ee3\u306fNauheimer et al. (2012) \u306b\u57fa\u3065\u3044\u305f\u3002
The genus Wolffia<\/em><\/strong>
A: Formation of fronds; presence of crystal-containing cells in fronds; formation of roots with root sheaths; formation of daughter fronds, flowers, or both on either side of the frond base; daughter fronds and flowers enclosed by prophylls; two stamens with tetrasporangiate anthers; longitudinally ribbed seeds
B: Loss of crystal-containing cells in fronds; loss of roots; formation of daughter fronds at a single site at the frond base; formation of flowers on the upper surface of the frond; absence of prophylls in both daughter fronds and flowers; a single stamen with a bisporangiate anther; nearly smooth seeds
Green indicates native areas, and purple indicates introduced areas. Source: POWO (2026). Plants of the World Online<\/em>. Facilitated by the Royal Botanic Gardens, Kew. Published on the Internet; https:\/\/powo.science.kew.org\/. Retrieved 16 Sept 2026. Distribution data from Kew Backbone Distributions (WCVP). \u00a9 World Checklist of Vascular Plants, licensed under CC BY 3.0.<\/figcaption><\/figure>\n\n\n\n

The genus <\/strong>Wolffia<\/em><\/strong><\/p>\n\n\n\n

Wolffia<\/em> comprises 11 recognized species, three of which occur on multiple continents (POWO 2026).<\/p>\n\n\n\n

\u5f62\u614b (Landolt 1998)<\/strong>
\u6839<\/strong>\uff1a\u306a\u3057\u3002W. microscopica<\/em> \u306f\u507d\u6839\u3092\u5f62\u6210\u3059\u308b\u3002
\u30d5\u30ed\u30f3\u30c9<\/strong>\uff1a\u539a\u304f\u3001\u7403\u5f62\u3001\u5375\u5f62\u3001\u5186\u67f1\u5f62\u3001\u5186\u9310\u5f62\u3001\u307e\u305f\u306f\u821f\u5f62\u3002
\u82b1<\/strong>\uff1a\u30d5\u30ed\u30f3\u30c9\u4e0a\u9762\u306b\u5f62\u6210\u3055\u308c\u308b\u3002\u96c4\u305a\u3044\u306f1\u672c\u3067\u3001\u846f\u306f2\u80de\u5b50\u56a2\u6027\u3002\u96cc\u305a\u3044\u306f1\u672c\u3002
\u7a2e\u5b50<\/strong>\uff1a\u8868\u9762\u306f\u307b\u307c\u5e73\u6ed1\u3002 <\/p>\n\n\n\n

\u30df\u30b8\u30f3\u30b3\u30a6\u30ad\u30af\u30b5\u5c5e\u306b\u306f\u3001\u30df\u30b8\u30f3\u30b3\u30a6\u30ad\u30af\u30b5 Wolffia globosa<\/em> \u306e\u3088\u3046\u306b\u9577\u30550.5 mm\u3001\u5e450.4 mm\u307b\u3069\u306e\u500b\u4f53\u3092\u3082\u3064\u7a2e\u304c\u3042\u308a\u3001\u4e16\u754c\u6700\u5c0f\u306e\u88ab\u5b50\u690d\u7269\u3068\u3057\u3066\u77e5\u3089\u308c\u3066\u3044\u308b (Lansdown et al. 2022)\u3002\u5c5e\u5185\u306e\u7a2e\u306f\u3001\u30d5\u30ed\u30f3\u30c9\u306e\u5f62\u306b\u52a0\u3048\u3001\u4e0a\u9762\u304b\u3089\u898b\u305f\u3068\u304d\u306b W. arrhiza<\/em> \u306e\u3088\u3046\u306b\u8fba\u7e01\u304c\u767d\u304f\u898b\u3048\u308b\u304b\u3001W. angusta<\/em> \u306e\u3088\u3046\u306b\u4e2d\u592e\u90e8\u304c\u767d\u304f\u898b\u3048\u308b\u304b\u306a\u3069\u306e\u7279\u5fb4\u306b\u3088\u3063\u3066\u8b58\u5225\u3055\u308c\u308b (Bog et al. 2020)\u3002Wolffia microscopica <\/em>\u306f\u507d\u6839\u3092\u5f62\u6210\u3059\u308b\u3002<\/p>\n\n\n\n

\"\"<\/a>
\u30df\u30b8\u30f3\u30b3\u30a6\u30ad\u30af\u30b5 Wolffia globosa<\/em>_1: Cropped a photo by anuraknin, https:\/\/www.inaturalist.org\/photos\/575777536, CC BY-NC. Wolffia arrhiza<\/em>_1: Cropped a photo by \u0418\u0432\u0430\u043d \u041c\u0430\u0442\u0435\u0440\u0448\u0435\u0432, https:\/\/www.inaturalist.org\/photos\/728528977, CC BY-NC. Wolffia angusta<\/em>_1: Cropped a photo by Greg Tasney, https:\/\/www.inaturalist.org\/photos\/607665668, CC BY-SA. Wolffia angusta<\/em>_2: Cropped a photo by Greg Tasney, https:\/\/www.inaturalist.org\/photos\/607665636, CC BY-SA. Wolffia microscopica<\/em>_13 and 14: Wolffia microscopica<\/em>_20150917_8 and 9, CC BY-NC.<\/figcaption><\/figure>\n\n\n\n

Morphology (Landolt 1998)<\/strong>
Roots<\/strong>: Absent. W. microscopica<\/em> forms a pseudoroot.
Fronds<\/strong>: Thick; globose, ovoid, cylindrical, conical, or boat-shaped.
Flowers<\/strong>: Formed on the upper surface of the frond. A single stamen with a bisporangiate anther and a single pistil.
Seeds<\/strong>: Surface nearly smooth.<\/p>\n\n\n\n

Wolffia<\/em> includes species such as W. globosa<\/em>, with individuals as small as approximately 0.5 mm long and 0.4 mm wide, and is known for comprising the world\u2019s smallest angiosperms (Lansdown et al. 2022). Species within the genus are distinguished by frond shape and other features, including whether, when viewed from above, the margins appear white, as in W. arrhiza<\/em>, or the central region appears white, as in W. angusta<\/em> (Bog et al. 2020). Wolffia microscopica<\/em> forms a pseudoroot.<\/p>\n\n\n\n

\u5f15\u7528\u6587\u732e  References<\/strong><\/p>\n\n\n\n

Abley, K., Locke, J.C.W., and Leyser, H.M.O. (2016). Developmental mechanisms underlying variable, invariant and plastic phenotypes. Ann. Bot. 117<\/em>, 733\u2013748. https:\/\/doi.org\/10.1093\/AOB\/MCW016.<\/p>\n\n\n\n

An, D., Zhou, Y., Li, C., Xiao, Q., Wang, T., Zhang, Y., Wu, Y., Li, Y., Chao, D.Y., Messing, J., et al. (2019). Plant evolution and environmental adaptation unveiled by long-read whole-genome sequencing of Spirodela. Proc. Natl. Acad. Sci. U. S. A. 116<\/em>, 18893\u201318899. https:\/\/doi.org\/10.1073\/PNAS.1910401116;WGROUP:STRING:PUBLICATION.<\/p>\n\n\n\n

Arber, A. (1919). On the vegetative morphology of Pistia<\/em> and the Lemnaceae. Proc. R. Soc. Lond. B<\/em> 91: 96\u2013103.<\/p>\n\n\n\n

Bhanthumnavin, K., and Mcgarry, M.G. (1971). Wolffia arrhiza as a possible source of inexpensive protein. Nature 232<\/em>, 495. https:\/\/doi.org\/10.1038\/232495A0.<\/p>\n\n\n\n

Bradshaw, A.D. (1965). Evolutionary Significance of Phenotypic Plasticity in Plants. Adv. Genet. 13<\/em>, 115\u2013155. https:\/\/doi.org\/10.1016\/S0065-2660(08)60048-6.<\/p>\n\n\n\n

Brunaud, A. (1974). Organisation de la pousse v\u00e9g\u00e9tative d\u2019une Lemnac\u00e9e: Spirodela polyrhiza<\/em> (L.) Schleid. C. R. Acad. Sci. Paris<\/em>, S\u00e9rie D, 278: 1183\u20131186.<\/p>\n\n\n\n

Caldwell, O.W. (1899). On the Life-History of Lemna minor. Botanical Gazette 27<\/em>, 37\u201366. https:\/\/doi.org\/10.1086\/327786.<\/p>\n\n\n\n

den Hartog, C. (1964). Over de oecologie van bloeiende Lemna trisulca. Gorteria 2<\/em>, 68\u201372.<\/p>\n\n\n\n

Ding, Y., Fang, Y., Guo, L., Li, Z., He, K., Zhao, Y., and Zhao, H. (2017). Phylogenic study of Lemnoideae (duckweeds) through complete chloroplast genomes for eight accessions. PeerJ 2017<\/em>, e4186. https:\/\/doi.org\/10.7717\/PEERJ.4186\/SUPP-8.<\/p>\n\n\n\n

Engler, A. (1877). Vergleichende Untersuchungen \u00fcber die morphologischen Verh\u00e4ltnisse der Araceae. Nova Acta K. Leop.-Carol. Dtsch. Acad. Naturf.<\/em> 39: 135\u2013224.<\/p>\n\n\n\n

Fang, Y., Tian, X., Jin, Y., Du A., Ding, Y., Liao, Z., He, K., Zhao, Y., Guo, L., Xiao, Y., et al. (2025). Duckweed Evolution: from Land back to Water. Genomics Proteomics Bioinformatics 23<\/em>, qzaf074. https:\/\/doi.org\/10.1093\/GPBJNL\/QZAF074.<\/p>\n\n\n\n

Franceschi, V.R., and Horner, H.T. (1980). Calcium oxalate crystals in plants. The Botanical Review 46<\/em>, 361\u2013427. https:\/\/doi.org\/10.1007\/BF02860532.<\/p>\n\n\n\n

Fujita, M., Mori, K., and Kodera, T. (1999). Nutrient removal and starch production through cultivation of Wolffia arrhiza. J. Biosci. Bioeng. 87<\/em>, 194\u2013198. https:\/\/doi.org\/10.1016\/S1389-1723(99)89012-4.<\/p>\n\n\n\n

Gitz, D.C., Liu-Gitz, L., McClure, J.W., and Huerta, A.J. (2004). Effects of a PAL inhibitor on phenolic accumulation and UV\u2010B tolerance in Spirodela intermedia<\/em> (Koch.). J. Exp. Bot. 55<\/em>, 919\u2013927. https:\/\/doi.org\/10.1093\/JXB\/ERH092.<\/p>\n\n\n\n

Hegelmaier, F. (1868). Die Lemnaceen. Eine monographische Untersuchung<\/em>. Leipzig: Wilhelm Engelmann.<\/p>\n\n\n\n

Hegelmaier, F. (1895). Systematische \u00dcbersicht der Lemnaceen. Bot. Jahrb.<\/em> 21: 268\u2013305.<\/p>\n\n\n\n

Herrera, C.M., Medrano, M., and Bazaga, P. (2014). Variation in DNA methylation transmissibility, genetic heterogeneity and fecundity-related traits in natural populations of the perennial herb Helleborus foetidus. Mol. Ecol.<\/em> 23<\/em>, 1085\u20131095. https:\/\/doi.org\/10.1111\/MEC.12679.<\/p>\n\n\n\n

Hillman, W. S., Culley, D. D. (1978). The use of duckweed. American Scientist<\/em>, 66<\/em>, 442\u2013451.<\/p>\n\n\n\n

Hoffmann, J. F. (1840). Beitr\u00e4ge zur n\u00e4heren Kenntnis von Lemna arrhiza<\/em>, nebst einigen Bemerkungen \u00fcber L. polyrhiza<\/em>, L. gibba<\/em>, L. minor<\/em> und L. trisulca<\/em>. Arch. Naturgesch.<\/em> 6: 138\u2013163.<\/p>\n\n\n\n

Ishizawa, H., Onoda, Y., Kitajima, K., Kuroda, M., Inoue, D., and Ike, M. (2021). Coordination of leaf economics traits within the family of the world\u2019s fastest growing plants (Lemnaceae). Journal of Ecology 109<\/em>, 2950\u20132962. https:\/\/doi.org\/10.1111\/1365-2745.13710.<\/p>\n\n\n\n

Kandeler, R. (1979). Lemnaceae. In: Hegi, G. (ed.), Illustrierte Flora von Mitteleuropa<\/em>, 2(1), 3rd ed. Berlin: Parey, pp. 335\u2013346.<\/p>\n\n\n\n

Katayama, N., Koi, S., and Kato, M. (2010). Expression of SHOOT MERISTEMLESS<\/em>, WUSCHEL<\/em>, and ASYMMETRIC LEAVES1<\/em> Homologs in the Shoots of Podostemaceae: Implications for the Evolution of Novel Shoot Organogenesis. Plant Cell<\/em> 22: 2131-2140.<\/p>\n\n\n\n

Kim, I.S. (2007). Development of the root system inSpirodela polyrhiza (L.) schleiden (Lemnaceae). Journal of Plant Biology 2007 50:5 50<\/em>, 540\u2013547. https:\/\/doi.org\/10.1007\/BF03030707.<\/p>\n\n\n\n

Lam, E., and Michael, T.P. (2022). Wolffia, a minimalist plant and synthetic biology chassis. Trends Plant Sci. 27<\/em>, 430\u2013439. https:\/\/doi.org\/10.1016\/J.TPLANTS.2021.11.014.<\/p>\n\n\n\n

Landolt, E. 1986. The Family of Lemnaceae: A Monographic Study<\/em>, vol. 1, Ver\u00f6ff. <\/em>Geobot. Inst. ETH Stiftung R\u00fcbel<\/em> <\/em>71<\/strong>.<\/p>\n\n\n\n

Landolt, E. 1998. Lemanceae. In K. Kubitzki ed. The Families and Genera of Vascular Plants. IV. Pp. 264-270.<\/p>\n\n\n\n

Lemon, G.D. and Posluszny, U. 2000. Comparative Shoot Development and Evolution in the Lemnaceae. Int. J. Plant Sci. 161: 733-748.<\/p>\n\n\n\n

Les, D.H. and D. J. CRAWFORD. 1999. Landoltia (Lemnaceae), a new genus of duckweeds. Novon 9: 530-533. <\/p>\n\n\n\n

Les, D. H., Crawford, D. J., Landolt, E., Gabel, J. D. & Kimball, R. T. (2002).
Phylogeny and systematics of Lemnaceae, the duckweed family.
Systematic Botany<\/em> 27<\/strong>: 221\u2013240.<\/p>\n\n\n\n

Meusel, H. (1951). Die Bedeutung der Wuchsform f\u00fcr die Entwicklung des nat\u00fcrlichen Systems der Pflanzen. Feddes Repert.<\/em> 54: 137\u2013172.<\/p>\n\n\n\n

Mejbel, H.S., and Simons, A.M. (2018). Aberrant clones: Birth order generates life history diversity in Greater Duckweed, Spirodela polyrhiza<\/em>. Ecol. Evol. 8<\/em>, 2021\u20132031. https:\/\/doi.org\/10.1002\/ECE3.3822;ISSUE:ISSUE:DOI.<\/p>\n\n\n\n

Michael, T.P., Ernst, E., Hartwick, N., Chu, P., Bryant, D., Gilbert, S., Ortleb, S., Baggs, E.L., Sree, K.S., Appenroth, K.J., et al. (2021). Genome and time-of-day transcriptome of Wolffia australiana link morphological minimization with gene loss and less growth control. Genome Res. 31<\/em>, 225\u2013238. https:\/\/doi.org\/10.1101\/GR.266429.120\/-\/DC1.<\/p>\n\n\n\n

Nakata, P.A. (2003). Advances in our understanding of calcium oxalate crystal formation and function in plants. Plant Science 164<\/em>, 901\u2013909. https:\/\/doi.org\/10.1016\/S0168-9452(03)00120-1.<\/p>\n\n\n\n

Senayai, A., Chmilar, S.L., Abeyrama, D., Burg, T.M., Laird, R.A., and Kraichak, E. (2026). Demographic senescence and lifespan extension by caloric restriction in two duckweed species (Wolffia brasiliensis and Lemna aequinoctialis). Aquat. Bot. 204<\/em>, 103991. https:\/\/doi.org\/10.1016\/J.AQUABOT.2026.103991.<\/p>\n\n\n\n

Stafstrom, J.P., and Sarup, V.B. (2000). Development of supernumerary buds from the axillary meristem of pea, Pisum sativum (Fabaceae). Aust. J. Bot. 48<\/em>, 271\u2013278. https:\/\/doi.org\/10.1071\/BT98077.<\/p>\n\n\n\n

Sree, K.S., Maheshwari, S.C., Boka, K., Khurana, J.P., Keresztes, A., and Appenroth, K.-J. 2015_1. The duckweek Wolffia microscopica<\/em>: a unique aquatic monocot. Flora 210: 31-39.<\/p>\n\n\n\n

Sree, K.S., Sudakaran, S., and Appenroth, K.J. (2015_2). How fast can angiosperms grow? Species and clonal diversity of growth rates in the genus Wolffia (Lemnaceae). Acta Physiologiae Plantarum 2015 37:10 37<\/em>, 204-. https:\/\/doi.org\/10.1007\/S11738-015-1951-3.<\/p>\n\n\n\n

POWO (2026). Plants of the World Online<\/em>. Facilitated by the Royal Botanic Gardens, Kew. Published on the Internet; https:\/\/powo.science.kew.org\/<\/a>. Retrieved 12 Sept. 2026.<\/p>\n\n\n\n

Schmid, M.W., Moradi, A., Leigh, D.M., Schuman, M.C., and van Moorsel, S.J. (2024). Covering the bases: Population genomic structure of Lemna minor and the cryptic species L.\u2009japonica in Switzerland. Ecol. Evol. 14<\/em>, e11599. https:\/\/doi.org\/10.1002\/ECE3.11599.<\/p>\n\n\n\n

Ward, D.B. (2011). Spirodela oligorrhiza (Lemnaceae) is the correct name for the lesser greater duckweed. J. Bot. Res. Inst. Texas 5<\/em>, 197\u2013203.<\/p>\n\n\n\n

Witztum, A. (1974). Ultraviolet irradiation and pigment cell idioblasts in Spirodela oligorhiza <\/em>(Lemnaceae). Am. J. Bot. 61<\/em>, 713\u2013716. https:\/\/doi.org\/10.1002\/J.1537-2197.1974.TB12292.X.<\/p>\n\n\n\n

Zhao, L., Yang, Y.Y., Qu, X.J., Ma, H., Hu, Y., Li, H.T., Yi, T.S., and Li, D.Z. (2022). Phylotranscriptomic analyses reveal multiple whole-genome duplication events, the history of diversification and adaptations in the Araceae. Ann. Bot. 131<\/em>, 199. https:\/\/doi.org\/10.1093\/AOB\/MCAC062.<\/p>\n","protected":false},"excerpt":{"rendered":"

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