{"id":1232,"date":"2024-10-11T17:50:07","date_gmt":"2024-10-11T08:50:07","guid":{"rendered":"https:\/\/www.nibb.ac.jp\/plantdic\/blog\/?p=1232"},"modified":"2024-10-11T17:52:20","modified_gmt":"2024-10-11T08:52:20","slug":"%e3%83%8f%e3%82%a8%e3%83%88%e3%83%aa%e3%82%bd%e3%82%a6%e3%81%ae%e8%a8%98%e6%86%b6%e3%80%80memory-of-the-venus-flytrap","status":"publish","type":"post","link":"http:\/\/www.nibb.ac.jp\/plantdic\/blog\/?p=1232","title":{"rendered":"\u30cf\u30a8\u30c8\u30ea\u30bd\u30a6\u306e\u8a18\u61b6\u3000Memory of the Venus flytrap"},"content":{"rendered":"\n
\"\"<\/a>
\u30b3\u30aa\u30ed\u30ae\u3092\u6355\u3089\u3048\u305f\u30cf\u30a8\u30c8\u30ea\u30bd\u30a6
the Venus flytrap Dionaea muscipula<\/em> eating a cricket in the locality<\/figcaption><\/figure>\n\n\n\n

\u30cf\u30a8\u30c8\u30ea\u30bd\u30a6\u5c5e\u306f\u3001\u8449\u8eab\u304c\u5909\u5316\u3057\u305f\u6355\u866b\u5668\u3067\u5c0f\u52d5\u7269\u3092\u6355\u3089\u3048\u3066\u6804\u990a\u3068\u3059\u308b\u3053\u3068\u3067\u3001\u8ca7\u6804\u990a\u5730\u3067\u3082\u751f\u80b2\u3067\u304d\u308b\u3002\u4e0a\u306e\u5199\u771f\u306f\u81ea\u751f\u5730\u3067\u64ae\u5f71\u3057\u305f\u3082\u306e\u3060\u304c\u3001\u9589\u3058\u305f\u8449\u3092\u958b\u3051\u308b\u3068\u30b3\u30aa\u30ed\u30ae\u304c\u5165\u3063\u3066\u3044\u305f\u3002\u540c\u3058\u98df\u866b\u690d\u7269\u3067\u3042\u308b\u30e2\u30a6\u30bb\u30f3\u30b4\u30b1\u5c5e\u306e\u59c9\u59b9\u5c5e\u3067\u3001\u30cf\u30a8\u30c8\u30ea\u30bd\u30a6Dionaea muscipula<\/em>\uff11\u7a2e\u304b\u3089\u306a\u308b\u5358\u578b\u5c5e\u3067\u3042\u308b\u3002<\/p>\n\n\n\n

The Venus flytrap genus, Dionaea<\/em>, captures small animals using modified leaves that act as a trap, obtaining nutrients to thrive in nutrient-poor environments. It is a sister genus to the sundew genus, which is also a carnivorous plant, and consists of a single species, Dionaea muscipula<\/em>, making it a monotypic genus.<\/p>\n\n\n\n

\"\"<\/a>
\u7c73\u56fd\u30ce\u30fc\u30b9\u30ab\u30ed\u30e9\u30a4\u30ca\u5dde\u306e\u30cf\u30a8\u30c8\u30ea\u30bd\u30a6\u306e\u81ea\u751f\u5730
Locality of the Venus flytrap Dionaea muscipula<\/em> near Wilmington, North Carolina, USA <\/figcaption><\/figure>\n\n\n\n

\u30cf\u30a8\u30c8\u30ea\u30bd\u30a6\u306f\u7c73\u56fd\u306e\u30ce\u30fc\u30b9\u30ab\u30ed\u30e9\u30a4\u30ca\u5dde\u3068\u30b5\u30a6\u30b9\u30ab\u30ed\u30e9\u30a4\u30ca\u5dde\u306e\u6d77\u5cb8\u7dda\u306e\u6cbf\u3063\u305f\u7d04340 km\u306e\u7bc4\u56f2\u306b\u5206\u5e03\u3057\u3066\u3044\u305f\u304c\u3001\u571f\u5730\u958b\u767a\u3084\u63a1\u96c6\u306b\u3088\u3063\u3066\u73fe\u5728\u3067\u306f\u9650\u3089\u308c\u305f\u56fd\u7acb\u516c\u5712\u3084\u79c1\u6709\u5730\u306a\u3069\u3067\u898b\u3089\u308c\u308b\u3060\u3051\u3067\u3042\u308b\uff08Bailey and McPherson 2012, Juniper et al. 1989, Roberts and Oosting 1958\uff09\u3002\u5730\u56f3\u306f\u6b21\u306e\u30b5\u30a4\u30c8\u3088\u308a\u5f15\u7528\uff1ahttps:\/\/www.freemap.jp\/free.html<\/p>\n\n\n\n

The Venus flytrap was distributed along a roughly 340 km stretch of the coastal region of North Carolina and South Carolina in the United States, but due to land development and poaching, it can now only be found in limited areas such as national parks and private lands (Bailey and McPherson 2012, Juniper et al. 1989, Roberts and Oosting 1958). The map was sited from https:\/\/www.freemap.jp\/free.html<\/p>\n\n\n\n

\"\"<\/a>
\u7c73\u56fd\u30ce\u30fc\u30b9\u30ab\u30ed\u30e9\u30a4\u30ca\u5dde\u306e\u30cf\u30a8\u30c8\u30ea\u30bd\u30a6\u306e\u81ea\u751f\u5730
Locality of the Venus flytrap Dionaea muscipula<\/em> near Wilmington, North Carolina, USA <\/figcaption><\/figure>\n\n\n\n

\u30cf\u30a8\u30c8\u30ea\u30bd\u30a6\u306f\u3001\u5c71\u706b\u4e8b\u304c\u6570\u5e74\u304a\u304d\u306b\u304a\u3053\u308b\u5834\u6240\u306b\u751f\u80b2\u3059\u308b\u3002\u5730\u4e0b\u306e\u9c57\u830e\u306f\u8868\u9762\u3092\u713c\u304f\u7a0b\u5ea6\u306e\u5c71\u706b\u4e8b\u306b\u306f\u8010\u6027\u304c\u3042\u308a\u3001\u4e0a\u90e8\u3092\u8986\u3063\u3066\u3044\u305f\u8349\u304c\u713c\u304d\u6255\u308f\u308c\u308b\u3068\u5143\u6c17\u306b\u751f\u80b2\u3059\u308b\u3002\u5c71\u706b\u4e8b\u306e\u5f8c\u306b\u306f\u7d0410%\u958b\u82b1\u500b\u4f53\u304c\u5897\u3048\u308b\u304c\u3001\u6570\u5e74\u3057\u3066\u5468\u308a\u3092\u30a4\u30cd\u79d1\u3001\u30ab\u30e4\u30c4\u30ea\u30b0\u30b5\u79d1\u3001\u30a4\u30b0\u30b5\u79d1\u306e\u8349\u672c\u304c\u8986\u3046\u3088\u3046\u306b\u306a\u308b\u3068\u958b\u82b1\u6570\u304c\u6e1b\u308b\uff08Bailey and McPherson 2012, Roberts and oosting 1958)\u3002<\/p>\n\n\n\n

The Venus flytrap grows in areas where wildfires occur every few years. The underground bulb is resistant to wildfires that burn only the surface, and it thrives once the grasses covering the top are burned away. After a wildfire, the number of flowering individuals increases by about 10%, but as grasses from the Poaceae, Cyperaceae, and Juncaceae families cover the area over the years, the number of flowering plants decreases (Bailey and McPherson 2012, Roberts and Oosting 1958).<\/p>\n\n\n\n

\"\"<\/a>
\u30cf\u30a8\u30c8\u30ea\u30bd\u30a6\u306e\u5f62\u614b
Morphology of the Venus flytrap Dionaea muscipula<\/em><\/figcaption><\/figure>\n\n\n\n

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The leaves of the Venus flytrap have their leaf blades modified into traps, while the petioles grow broadly and take on the appearance of ordinary leaf blades (A). The stem runs horizontally near the surface of soil, and because the internodes between the leaves are short, the leaves form a rosette. The base of the petioles thickens with soft tissue, and the underground part becomes bulbous. (C) is an image of a cross-section of (B), cut along the white dotted line, taken from the shoot apex side of the stem. You can see that the petioles and roots emerge from the thin stem (enclosed in the black dotted line).<\/p>\n\n\n\n

\"\"<\/a>
\u30cf\u30a8\u30c8\u30ea\u30bd\u30a6\u306e\u6355\u866b\u5668\u306e\u5f62\u614b
Trap morphology of the Venus flytrap Dionaea muscipula<\/em><\/figcaption><\/figure>\n\n\n\n

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Spines form along the edges (the leaf margin) of the trap (A), and typically six sensory hairs (white arrows in [A]) develop on its surface. When the sensory hairs receive two successive touch stimuli, the trap closes, capturing the prey ([B] and Movie). After the trap closes, if the prey struggles and further stimulates the sensory hairs, the leaf blade bends backward, pressing the prey, and the area just inside the leaf margin seals tightly. The stimulation of the sensory hairs induces the secretion of digestive fluids, and the inner side of the tightly sealed leaf becomes filled with the digestive fluid (the white arrow in [C] indicates where the leaked digestive fluid is visible).<\/p>\n\n\n\n

\u30cf\u30a8\u30c8\u30ea\u30bd\u30a6\u306e\u6355\u866b\u5668\u306f\u611f\u899a\u6bdb\u3092\uff12\u56de\u523a\u6fc0\u3059\u308b\u3068\u9589\u3058\u308b\uff08\u9808\u7530\u5553\u64ae\u5f71\uff09
The trap of the Venus flytrap Dionaea muscipula <\/em>close with two touch stimuli by Dr. Hiraku Suda<\/figcaption><\/figure>\n\n\n\n

\u30cf\u30a8\u30c8\u30ea\u30bd\u30a6\u3092\u4f7f\u3063\u305f\u8a18\u61b6\u306b\u95a2\u3059\u308b\u7814\u7a76\u3092\u7d39\u4ecb\u3057\u305f\u3044\uff08\u9577\u8c37\u90e82023\u3088\u308a\u4e00\u90e8\u6539\u5909\u3057\u3066\u5f15\u7528\uff09\u3002\u690d\u7269\u306b\u8a18\u61b6\u3068\u306f\u306a\u3093\u305e\u3084\u3068\u601d\u308f\u308c\u308b\u304b\u3082\u3057\u308c\u306a\u3044\u3002\u6211\u3005\u306e\u8a18\u61b6\u306f\u8133\u306b\u3088\u3063\u3066\u53f8\u3089\u308c\u308b\u3002\u3067\u306f\u3001\u8133\u306e\u7121\u3044\u690d\u7269\u306f\u8a18\u61b6\u3067\u304d\u306a\u3044\u306e\u3060\u308d\u3046\u304b\u3002<\/p>\n\n\n\n

Macfarlane(1902)\u306f\u3001\u30cf\u30a8\u30c8\u30ea\u30bd\u30a6\u306e\u611f\u899a\u6bdb\u3092\uff11\u56de\u3060\u3051\u523a\u6fc0\u3057\u3066\u3082\u8449\u304c\u9589\u3058\u306a\u3044\u3051\u308c\u3069\u300120\u79d2\u9593\u9694\u3067\uff12\u56de\u523a\u6fc0\u3059\u308b\u3068\u9589\u3058\u308b\u3053\u3068\u3092\u767a\u898b\u3057\u305f\u3002\u3053\u306e\u3053\u3068\u306f\u3001\u30cf\u30a8\u30c8\u30ea\u30bd\u30a6\u304c\uff11\u56de\u76ee\u306e\u523a\u6fc0\u3092\u8a18\u61b6\u3057\u3066\u3044\u308b\u3053\u3068\u3092\u610f\u5473\u3057\u3066\u3044\u308b\u3002\u3055\u3089\u306b\u3001\uff11\u56de\u76ee\u3068\uff12\u56de\u76ee\u306e\u523a\u6fc0\u306e\u9593\u9694\u309230\u79d2\u306b\u5ef6\u3070\u3059\u3068\u8449\u304c\u9589\u3058\u306a\u3044\u3053\u3068\u304b\u3089\u3001\u8a18\u61b6\u306f30\u79d2\u307b\u3069\u3057\u304b\u3082\u305f\u306a\u3044\u3053\u3068\u306b\u3082\u6c17\u3065\u3044\u305f\u3002\u305d\u3057\u3066\u3001Brown\u3068Sharp\u306f\u8a18\u61b6\u6642\u9593\u304c\u6e29\u5ea6\u306b\u4f9d\u5b58\u3059\u308b\u3053\u3068\u306b\u6c17\u3065\u3044\u305f(Brown and Sharp, 1910)\u3002\u3053\u306e\u3053\u3068\u306f\u3001\u8a18\u61b6\u304c\u5316\u5b66\u53cd\u5fdc\u306b\u3088\u3063\u3066\u3044\u308b\u3053\u3068\u3092\u793a\u5506\u3057\u3066\u3044\u308b\u3002Brown (1916)\u306f\u3088\u308a\u5b9a\u91cf\u7684\u306a\u5b9f\u9a13\u3092\u884c\u3044\u300110\u679a\u306e\u8449\u306b33\u79d2\u9593\u9694\u3067\uff12\u56de\u306e\u523a\u6fc0\u3092\u4e0e\u3048\u308b\u3068\u3001\u307b\u307c\u5168\u3066\u306e\u8449\u304c\u9589\u3058\u308b\u304c\u300167\u79d2\u9593\u9694\u3060\u3068\u5e73\u57472.75\u56de\u306e\u523a\u6fc0\u304c\u5fc5\u8981\u3067\u3042\u308b\u3068\u5831\u544a\u3057\u3001\u3053\u306e\u5b9f\u9a13\u306b\u57fa\u3065\u304d\u3001\u30cf\u30a8\u30c8\u30ea\u30bd\u30a6\u306f\u7d0430\u79d2\u306e\u8a18\u61b6\u304c\u3042\u308b\u3068\u8a18\u8f09\u3055\u308c\u308b\u3053\u3068\u304c\u591a\u3044\u3002\u307e\u305f\u3001\u8449\u304c\uff12\u56de\u306e\u523a\u6fc0\u3067\u9589\u3058\u308b\u4ed5\u7d44\u307f\u306f\u3001\u843d\u3061\u8449\u3001\u5c0f\u77f3\u3001\u96e8\u306a\u3069\u306e\u7372\u7269\u4ee5\u5916\u306e\u7269\u304c\u5076\u7136\u3042\u305f\u3063\u3066\u3082\u8449\u3092\u9589\u3058\u306a\u3044\u70b9\u3067\u9069\u5fdc\u7684\u3060\u3068\u8003\u3048\u3089\u308c\u3066\u3044\u308b(Poppinga et al., 2018)\u3002\u7279\u306b\u3001\u96e8\u306f\u6570\u65e5\u304a\u304d\u306b\u964d\u308b\u306e\u3067\u3001\u96e8\u7c92\u306b\u3042\u305f\u3063\u3066\u8449\u304c\u9589\u3058\u306a\u3044\u3088\u3046\u306b\u3059\u308b\u3053\u3068\u306f\u3001\u30a8\u30cd\u30eb\u30ae\u30fc\u306e\u640d\u5931\u3092\u9632\u3050\u4e0a\u3067\u91cd\u8981\u3060\u3068\u8003\u3048\u3089\u308c\u308b\u3002\u683d\u57f9\u3057\u3066\u3044\u308b\u30cf\u30a8\u30c8\u30ea\u30bd\u30a6\u306b\u30b8\u30e7\u30a6\u30ed\u3067\u6c34\u3092\u304b\u3051\u3066\u3082\u8449\u304c\u9589\u3058\u306a\u3044\u3002\u3088\u304f\u898b\u308b\u3068\u3001\uff11\u7c92\u76ee\u306e\u96e8\u7c92\u304c\u3042\u305f\u308b\u3068\u3001\u8868\u9762\u5f35\u529b\u306b\u3088\u3063\u3066\u3001\u6c34\u304c\u611f\u899a\u6bdb\u306e\u5468\u308a\u3092\u8986\u3063\u3066\u3057\u307e\u3046\u3002\u306a\u306e\u3067\u3001\uff12\u7c92\u76ee\u4ee5\u964d\u306e\u96e8\u7c92\u304c\u3042\u305f\u3063\u3066\u3082\u523a\u6fc0\u304c\u5f31\u304f\u306a\u3063\u3066\u3044\u308b\u3088\u3046\u3067\u3042\u308b\u3002<\/p>\n\n\n\n

\u3000\u690d\u7269\u306f\u3001\u5916\u754c\u304b\u3089\u306e\u3055\u307e\u3056\u307e\u306a\u523a\u6fc0\u3092\u8a18\u61b6\u3059\u308b\u3053\u3068\u304c\u77e5\u3089\u308c\u3066\u3044\u308b(Taiz et al. 2022)\u3002\u4f8b\u3048\u3070\u3001\u4e7e\u71e5\u3084\u9ad8\u6e29\u306a\u3069\u3078\u306e\u9806\u5fdc\u3001\u75c5\u6c17\u306b\u304b\u304b\u308b\u3068\u75c5\u5bb3\u62b5\u6297\u6027\u304c\u5f37\u304f\u306a\u308b\u690d\u7269\u514d\u75ab\u3001\u51ac\u3092\u8a18\u61b6\u3057\u3066\u6625\u306b\u82b1\u304c\u54b2\u304f\u6625\u5316\u306a\u3069\u3067\u3042\u308b\u3002\u3053\u308c\u3089\u306e\u6570\u65e5\u4ee5\u4e0a\u306e\u9577\u671f\u9593\u306e\u8a18\u61b6\u306b\u5bfe\u3057\u3001\u30cf\u30a8\u30c8\u30ea\u30bd\u30a6\u304c\u6301\u3064\u77ed\u671f\u8a18\u61b6\u306f\u3001\u690d\u7269\u306b\u306f\u7a00\u3067\u3042\u308b\u3053\u3068\u304b\u3089\u8208\u5473\u3092\u6301\u305f\u308c\u3001\u591a\u304f\u306e\u7814\u7a76\u304c\u884c\u308f\u308c\u3066\u304d\u305f\u3002<\/p>\n\n\n\n

Here I introduce research on memory using the Venus flytrap (partially modified and cited from Hasebe 2023 [in Japanese]). You might wonder, “What does memory mean in plants?”. Our memory is governed by the brain. So, does this mean that plants, which lack a brain, cannot have memory? In 1902, Macfarlane discovered that while stimulating the sensory hairs of the Venus flytrap once does not cause the trap to close, two stimuli given 20 seconds apart will. This suggests that the Venus flytrap “remembers” the first stimulus. Furthermore, when the interval between the first and second stimulus is extended to 30 seconds, the trap does not close, indicating that this memory only lasts for about 30 seconds. Brown and Sharp later found that the duration of memory depends on temperature (Brown and Sharp, 1910), which implies that the memory is governed by chemical reactions. In 1916, Brown conducted more quantitative experiments, reporting that nearly all of 10 traps closed when stimulated twice at 33-second intervals, but at 67-second intervals, an average of 2.75 stimuli were needed. Based on this experiment, it is often stated that the Venus flytrap has a memory of around 30 seconds. Additionally, the mechanism by which the trap closes after two stimuli is considered adaptive because it prevents the trap from closing accidentally due to non-prey objects like leaves, pebbles, or rain (Poppinga et al., 2018). Rain, in particular, falls only every few days, so preventing the trap from closing in response to raindrops is important for conserving energy. If you water a cultivated Venus flytrap with a watering can, the trap does not close. On closer inspection, when the first raindrop hits, surface tension causes water to cover the area around the sensory hairs. Therefore, subsequent raindrops appear to provide a weaker stimulus.<\/p>\n\n\n\n

It is known that plants can \u201cmemorize” various environmental stimuli (Taiz et al., 2022). Examples include acclimation to drought or high temperatures, plant immunity that strengthens after exposure to disease, and vernalization, where plants memorize winter and bloom in spring. While these examples are forms of long-term memory, lasting days or more, the short-term memory of the Venus flytrap is rare in plants and has thus attracted much research attention.<\/p>\n\n\n\n

\"\"<\/a>
\u30cf\u30a8\u30c8\u30ea\u30bd\u30a6\u306e\u8a18\u61b6\u306e\u4ed5\u7d44\u307f\u306b\u3064\u3044\u3066\u306eHodick\u3068Sievers (1988)\u306e\u4eee\u8aac
Hypothesis of trap movement of the Venus flytrap Dionaea muscipula<\/em> by Hodick and Sievers (1988)<\/figcaption><\/figure>\n\n\n\n

\u3000\u611f\u899a\u6bdb\u3092\u523a\u6fc0\u3059\u308b\u3068\u3001\u795e\u7d4c\u7d30\u80de\u306e\u3088\u3046\u306b\u3001\u6d3b\u52d5\u96fb\u4f4d\u3068\u547c\u3070\u308c\u308b\u4e00\u904e\u6027\u306e\u96fb\u4f4d\u5909\u5316\u304c\u304a\u3053\u308b(Burdon-Sanderson, 1873)\u3002\u6d3b\u52d5\u96fb\u4f4d\u306f\u8449\u304c\u9589\u3058\u308b\u524d\u306b\u4f1d\u642c\u3057(DiPalma et al., 1961)\u3001\u611f\u899a\u6bdb\u306b\u523a\u6fc0\u3092\u4e0e\u3048\u308b\u3068\u3001\u611f\u899a\u6bdb\u304b\u3089\u8449\u5168\u4f53\u306b\u540c\u5fc3\u5186\u72b6\u306b\u6d3b\u52d5\u96fb\u4f4d\u304c\u4f1d\u642c\u3059\u308b(Sibaoka, 1966)\u3002\u3053\u308c\u3089\u306e\u3053\u3068\u304b\u3089\u3001\u611f\u899a\u6bdb\u304b\u3089\u8449\u306b\u5e83\u304c\u308b\u6d3b\u52d5\u96fb\u4f4d\u304c\u523a\u6fc0\u3068\u306a\u308a\u3001\u306a\u3093\u3089\u304b\u306e\u4ed5\u7d44\u307f\u3092\u99c6\u52d5\u3057\u3001\u904b\u52d5\u304c\u5f15\u304d\u8d77\u3053\u3055\u308c\u308b\u3068\u8003\u3048\u3089\u308c\u308b\u3088\u3046\u306b\u306a\u3063\u305f\u3002<\/p>\n\n\n\n

\u52d5\u7269\u7d30\u80de\u3067\u306f\u3001\u6d3b\u52d5\u96fb\u4f4d\u304c\u7d30\u80de\u819c\u306b\u3042\u308b\u30ab\u30eb\u30b7\u30a6\u30e0\u30c1\u30e3\u30cd\u30eb\uff08\u7279\u5b9a\u306e\u6761\u4ef6\u306b\u3088\u3063\u3066\u30ab\u30eb\u30b7\u30a6\u30e0\u30a4\u30aa\u30f3\u3092\u901a\u3059\u30bf\u30f3\u30d1\u30af\u8cea\uff09\u3092\u5236\u5fa1\u3059\u308b\u3053\u3068\u3067\u3001\u7d30\u80de\u8cea\u306e\u30ab\u30eb\u30b7\u30a6\u30e0\u30a4\u30aa\u30f3\u6fc3\u5ea6\u304c\u5909\u5316\u3059\u308b\u3002\u30ab\u30eb\u30b7\u30a6\u30e0\u30a4\u30aa\u30f3\u306f\u4e8c\u6b21\u60c5\u5831\u4f1d\u9054\u7269\u8cea\u3068\u3057\u3066\u6a5f\u80fd\u3057\u3001\u30ea\u30f3\u9178\u5316\u306a\u3069\u3092\u4ecb\u3057\u3066\u4ed6\u306e\u30bf\u30f3\u30d1\u30af\u8cea\u306e\u6a5f\u80fd\u3092\u5236\u5fa1\u3059\u308b\u3053\u3068\u3067\u3001\u7d30\u80de\u306b\u5909\u5316\u3092\u5f15\u304d\u8d77\u3053\u3059\u3002\u690d\u7269\u3067\u3082\u3001\u5de8\u5927\u7d30\u80de\u3092\u6301\u3064\u30db\u30b7\u30c4\u30ea\u30e2\u3092\u7528\u3044\u305f\u7814\u7a76\u304b\u3089\u3001\u6d3b\u52d5\u96fb\u4f4d\u306b\u3088\u3063\u3066\u30ab\u30eb\u30b7\u30a6\u30e0\u30c1\u30e3\u30cd\u30eb\u304c\u6d3b\u6027\u5316\u3055\u308c\u3001\u7d30\u80de\u5916\u304b\u3089\u7d30\u80de\u5185\u3078\u30ab\u30eb\u30b7\u30a6\u30e0\u30a4\u30aa\u30f3\u304c\u6d41\u5165\u3059\u308b(Shiina and Tazawa, 1987)\u3002\u3053\u306e\u3053\u3068\u304b\u3089\u3001\u690d\u7269\u7d30\u80de\u306b\u304a\u3044\u3066\u3082\u3001\u52d5\u7269\u7d30\u80de\u540c\u69d8\u306b\u3001\u30ab\u30eb\u30b7\u30a6\u30e0\u304c\u4e8c\u6b21\u60c5\u5831\u4f1d\u9054\u7269\u8cea\u3068\u3057\u3066\u6a5f\u80fd\u3059\u308b\u3068\u8003\u3048\u3089\u308c\u308b\u3088\u3046\u306b\u306a\u308a\u3001\u5b9f\u969b\u3001\u30df\u30eb\u30d5\u30e9\u30b9\u30b3\u30e2\u3068\u30df\u30ca\u30df\u30b7\u30e3\u30b8\u30af\u30e2\u306b\u304a\u3044\u3066\u3001\u6d3b\u52d5\u96fb\u4f4d\u306b\u3088\u3063\u3066\u7d30\u80de\u8cea\u306e\u30ab\u30eb\u30b7\u30a6\u30e0\u30a4\u30aa\u30f3\u6fc3\u5ea6\u304c\u4e0a\u6607\u3057\u3001\u539f\u5f62\u8cea\u6d41\u52d5\u304c\u505c\u6b62\u3059\u308b\u3053\u3068\u304c\u793a\u3055\u308c\u305f(Hayama et al., 1979)\u3002<\/p>\n\n\n\n

Hodick\u3068Sievers (1988)\u306f\u3001\u3053\u306e\u3088\u3046\u306a\u7814\u7a76\u7d50\u679c\u3068\u3001\u81ea\u3089\u306b\u3088\u308b\u30cf\u30a8\u30c8\u30ea\u30bd\u30a6\u306e\u6d3b\u52d5\u96fb\u4f4d\u306e\u767a\u751f\u6a5f\u69cb\u306e\u7814\u7a76\u304b\u3089\u3001\u30ab\u30eb\u30b7\u30a6\u30e0\u30a4\u30aa\u30f3\u6fc3\u5ea6\u5909\u5316\u306b\u3088\u3063\u3066\u8a18\u61b6\u73fe\u8c61\u304c\u8aac\u660e\u3067\u304d\u308b\u306e\u3067\u306f\u306a\u3044\u304b\u3068\u3044\u3046\u4eee\u8aac\u3092\u63d0\u5531\u3057\u305f\uff08\u4e0a\u56f3\uff09\u3002\u3053\u306e\u4eee\u8aac\u306f\u30011\uff09\u611f\u899a\u6bdb\u3092\u523a\u6fc0\u3059\u308b\u3068\u6d3b\u52d5\u96fb\u4f4d\u304c\u767a\u751f\u3057\u3001\u6d3b\u52d5\u96fb\u4f4d\u306b\u3088\u3063\u3066\u7d30\u80de\u5185\u306e\u30ab\u30eb\u30b7\u30a6\u30e0\u30a4\u30aa\u30f3\u6fc3\u5ea6\u304c\u4e0a\u6607\u3059\u308b\u30012\uff09\u30ab\u30eb\u30b7\u30a6\u30e0\u30a4\u30aa\u30f3\u3042\u308b\u3044\u306f\u305d\u308c\u306b\u3088\u3063\u3066\u5236\u5fa1\u3055\u308c\u308b\u5206\u5b50\u304c\u95be\u5024\uff08\u9650\u754c\u5024\uff09\u3092\u8d85\u3048\u305f\u91cf\u84c4\u7a4d\u3059\u308b\u3068\u8449\u304c\u9589\u3058\u308b\u30013\uff091\u56de\u306e\u523a\u6fc0\u3067\u306f\u30ab\u30eb\u30b7\u30a6\u30e0\u30a4\u30aa\u30f3\u306e\u4e0a\u6607\u306f\u95be\u5024\u3092\u8d85\u3048\u308b\u3053\u3068\u304c\u3067\u304d\u305a\u3001\u95be\u5024\u3092\u8d85\u3048\u308b\u306b\u306f\u3001\u5c11\u306a\u304f\u3068\u30822\u56de\u306e\u523a\u6fc0\u304c\u5fc5\u8981\u3067\u3042\u308b\u30014\uff09\u30ab\u30eb\u30b7\u30a6\u30e0\u30a4\u30aa\u30f3\u6fc3\u5ea6\u306f1\u56de\u76ee\u306e\u523a\u6fc0\u3067\u4e0a\u6607\u3057\u305f\u5f8c\u3001\u5f90\u3005\u306b\u6e1b\u5c11\u3057\u300130\u79d2\u4ee5\u4e0a\u305f\u3064\u3068\u3001\uff12\u56de\u76ee\u306e\u523a\u6fc0\u3092\u4e0e\u3048\u3066\u3082\u30ab\u30eb\u30b7\u30a6\u30e0\u30a4\u30aa\u30f3\u6fc3\u5ea6\u304c\u95be\u5024\u3092\u8d85\u3048\u308b\u3053\u3068\u304c\u3067\u304d\u306a\u3044\u3001\u3068\u3044\u3046\u3082\u306e\u3067\u3042\u308b\u3002\u3057\u304b\u3057\u3001Hodick\u3068Sievers\u306e\u4eee\u8aac\u3092\u691c\u8a3c\u3059\u308b\u306b\u306f\u3001\u7d30\u80de\u5185\u306e\u30ab\u30eb\u30b7\u30a6\u30e0\u30a4\u30aa\u30f3\u6fc3\u5ea6\u304c\u3069\u306e\u3088\u3046\u306b\u5909\u5316\u3059\u308b\u304b\u3092\u89b3\u5bdf\u3059\u308b\u3053\u3068\u304c\u5fc5\u8981\u3067\u3042\u308b\u3002\u3057\u304b\u3057\u3001\u30cf\u30a8\u30c8\u30ea\u30bd\u30a6\u306b\u304a\u3044\u3066\u7d30\u80de\u5185\u30ab\u30eb\u30b7\u30a6\u30e0\u30a4\u30aa\u30f3\u6fc3\u5ea6\u3092\u691c\u51fa\u3059\u308b\u65b9\u6cd5\u304c\u7121\u304f\u3001\u63d0\u5531\u304b\u308930\u5e74\u4ee5\u4e0a\u306b\u4e98\u3063\u3066\u3001\u4eee\u8aac\u306e\u691c\u8a3c\u304c\u3067\u304d\u305a\u306b\u3044\u305f\u3002<\/p>\n\n\n\n

When the sensory hairs are stimulated, a transient change in electrical potential called an action potential occurs, similar to what happens in nerve cells (Burdon-Sanderson, 1873). The action potential propagates before the trap closes (DiPalma et al., 1961). When the sensory hairs are stimulated, the action potential spreads concentrically from the hairs throughout the entire leaf (Sibaoka, 1966). From these findings, it became understood that the action potential spreading from the sensory hairs to the leaf serves as a stimulus that triggers some mechanism, causing the movement.<\/p>\n\n\n\n

In animal cells, action potentials regulate calcium channels (proteins that allow calcium ions to pass under certain conditions) located in the cell (plasma) membrane, changing the concentration of calcium ions in the cytoplasm. Calcium ions function as secondary messengers, regulating the function of other proteins through processes like phosphorylation, thereby inducing changes in the cell. Similarly, in plants, studies using Nitella<\/em> <\/em>flexilis<\/em>, a giant-celled green algae, have shown that action potentials activate calcium channels, allowing calcium ions to flow from outside the cell into the cell (Shiina and Tazawa, 1987). This led to the understanding that calcium functions as a secondary messenger in plant cells, just as it does in animal cells. Indeed, in Chara <\/em>corallina<\/em> and Nitellopsis<\/em> <\/em>obtusa<\/em>, it was shown that action potentials increase cytoplasmic calcium ion concentrations, which in turn stop cytoplasmic streaming (Hayama et al., 1979).<\/p>\n\n\n\n

Hodick and Sievers (1988) proposed a hypothesis that changes in calcium ion concentrations might explain the memory phenomenon, based on these studies and their own research into the mechanism behind action potentials in the Venus flytrap (see figure above). Their hypothesis includes the following points: 1) Stimulation of the sensory hairs generates an action potential, which raises the intracellular calcium ion concentration. 2) When calcium ions or molecules regulated by calcium accumulate beyond a threshold, the trap closes. 3) A single stimulus does not raise the calcium ion concentration above the threshold; at least two stimuli are required. 4) After the calcium ion concentration rises with the first stimulus, it gradually decreases, and after more than 30 seconds, a second stimulus cannot raise the calcium ion concentration above the threshold.<\/p>\n\n\n\n

However, in order to test Hodick and Sievers\u2019 hypothesis, it is necessary to observe how the intracellular calcium ion concentration changes. Unfortunately, no method for detecting calcium ion concentrations inside Venus flytrap cells existed, and for over 30 years after the hypothesis was proposed, it remained untested.<\/p>\n\n\n\n

\"\"<\/a>
\u30cf\u30a8\u30c8\u30ea\u30bd\u30a6\u306e\u8449\u306e\u30ab\u30eb\u30b7\u30a6\u30e0\u30a4\u30aa\u30f3\u6fc3\u5ea6\u5909\u5316\u3092\u53ef\u8996\u5316\u3057\u305f\u5199\u771f\u3002\u30ab\u30eb\u30b7\u30a6\u30e0\u6fc3\u5ea6\u304c\u4e0a\u304c\u308b\u3068\u8d64\u8272\u304c\u6fc3\u304f\u306a\u308a\u3001\u3055\u3089\u306b\u6fc3\u304f\u306a\u308b\u3068\u9ec4\u8272\u306b\u306a\u308b (Suda et al. 2020)\u3002A photo visualizing the changes in calcium ion concentration in the Venus flytrap Dionaea muscipula<\/em> leaf. As the calcium concentration increases, the red color becomes deeper, and when it increases further, it turns yellow (Suda et al. 2020).Di<\/figcaption><\/figure>\n\n\n\n

\u7d30\u80de\u5185\u306e\u30ab\u30eb\u30b7\u30a6\u30e0\u30a4\u30aa\u30f3\u6fc3\u5ea6\u3092\u691c\u51fa\u3059\u308b\u306b\u306f\u3001\u30ab\u30eb\u30b7\u30a6\u30e0\u30a4\u30aa\u30f3\u3068\u7d50\u5408\u3059\u308b\u3068\u5149\u3092\u767a\u3059\u308b\u3088\u3046\u306a\u30bb\u30f3\u30b5\u30fc\u30bf\u30f3\u30d1\u30af\u8cea\u3092\u30cf\u30a8\u30c8\u30ea\u30bd\u30a6\u3067\u50cd\u304b\u305b\u308b\u3053\u3068\u304c\u5fc5\u8981\u3067\u3042\u308b\u3002\u305d\u306e\u305f\u3081\u306b\u306f\u3001\u30bb\u30f3\u30b5\u30fc\u30bf\u30f3\u30d1\u30af\u8cea\u306e\u907a\u4f1d\u5b50\u3092\u30cf\u30a8\u30c8\u30ea\u30bd\u30a6\u306b\u5c0e\u5165\u3059\u308b\u3053\u3068\u304c\u5fc5\u8981\u3067\u3042\u308b\u3002 \u305d\u3053\u3067\u6211\u3005\u306e\u7814\u7a76\u30b0\u30eb\u30fc\u30d7\u306e\u9808\u7530\u5553\u306f\u3001\u30cf\u30a8\u30c8\u30ea\u30bd\u30a6\u306b\u30ab\u30eb\u30b7\u30a6\u30e0\u30a4\u30aa\u30f3\u3068\u7d50\u5408\u3059\u308b\u3068\u7dd1\u8272\u86cd\u5149\u3092\u51fa\u3059GCaMP6f\u30bf\u30f3\u30d1\u30af\u8cea\u3092\u30b3\u30fc\u30c9\u3059\u308b\u907a\u4f1d\u5b50\u3092\u5c0e\u5165\u3057\u3001\u907a\u4f1d\u5b50\u7d44\u63db\u3048\u30cf\u30a8\u30c8\u30ea\u30bd\u30a6\u3092\u4f5c\u51fa\u3057\u305f\u3002\u305d\u3057\u3066\u3001\u611f\u899a\u6bdb\u3092\uff11\u56de\u523a\u6fc0\u3059\u308b\u3068\u3001\u611f\u899a\u6bdb\u304b\u3089\u8449\u5168\u4f53\u306b\u540c\u5fc3\u5186\u72b6\u306b\u7dd1\u8272\u306e\u86cd\u5149\u304c\u5e83\u304c\u308b\u3053\u3068\u3092\u767a\u898b\u3057\u305f\uff08\u4e0a\u56f3\u4e0a\u6bb5\uff09\u3002\u305d\u3057\u3066\u3001\u5e83\u304c\u3063\u305f\u5f8c\u3001\u86cd\u5149\u306f\u6642\u9593\u304c\u305f\u3064\u306b\u3064\u308c\u3001\u5f90\u3005\u306b\u6e1b\u5c11\u3057\u305f\uff08\u4e0a\u56f3\u4e2d\u6bb5\uff09\u3002\uff12\u56de\u76ee\u306e\u523a\u6fc0\u3092\u4e0e\u3048\u308b\u3068\u3001\uff11\u56de\u76ee\u3088\u308a\u3082\u5f37\u3044\u86cd\u5149\u304c\u5e83\u304c\u308a\u3001\u8449\u306f\u9589\u3058\u305f\uff08\u4e0a\u56f3\u4e0b\u6bb5\uff09(Suda et al., 2020)\u3002<\/p>\n\n\n\n

To detect intracellular calcium ion concentrations, it is necessary to use a sensor protein that emits light when it binds to calcium ions. This requires introducing the gene encoding the sensor protein into the Venus flytrap. Therefore, Dr. Hiraku Suda from our research group introduced a gene encoding the GCaMP6f protein, which emits green fluorescence when it binds to calcium ions, into the Venus flytrap, creating a genetically modified Venus flytrap, after mostly three years\u2018 efforts.<\/p>\n\n\n\n

Upon stimulating the sensory hairs once, Suda discovered that fluorescence spreads concentrically from the sensory hairs across the entire leaf (imagens in the top row). After spreading, the fluorescence gradually decreased over time (images in the middle row). When a second stimulus was applied, a stronger fluorescence than after the first stimulus was observed, and the leaf closed (images in the bottom row) (Suda et al., 2020).<\/p>\n\n\n\n

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