Through photosynthesis, solar energy is converted into biological energy. It is often thought that photosynthesis becomes stronger as light becomes stronger, but actually photosynthesis may run out of control if subjected to an overabundance of light, causing reactive oxygen species which break the photosynthetic apparatus. To avoid this, when exposed to intense light plants have a mechanism called "qE quenching" to prevent runaway photosynthesis by converting the excess energy to heat and discarding it. An international team including researchers in France and Japan, using the green alga Chlamydomonas as a model, found a switch that triggers the suppression mechanism to prevent runaway photosynthesis. The switch is a blue light photoreceptor protein called phototropin. The research has been published in the September 22 issue of Nature.