Too much sunlight can damage plants, but researchers from Wageningen
University & Research and Lithuania have discovered how the internal
protection system works to help plants prevent damage from these overdoses.
Green plants are effective in capturing and processing sunlight. They divert
the absorbed photons (light particles) to the reaction center - where a
series of chemical reactions convert the energy into electrons and protons
needed to produce molecules such as sugar. In bright sunlight, however, the
reaction center is unable to do this. To prevent the next absorbed light
particle from being sent to the reaction center before the previous one has
been completely processed, plants deploy various protection mechanisms that
convert some of the absorbed light into harmless heat.
To activate the protection system, the plant triggers various enzymes. This
effect lasts some tens of seconds to several minutes. In fluctuating light,
for example when leaves are blown by the wind, it can result in costly
energy losses. The research team discovered that an important part of the
activation process is much faster than expected. Although the activation
process initially lasts tens of seconds, once the protection has been
activated the system can respond to the state of the reaction center almost
instantaneously. If the reaction center is still processing the previous
bundle of energy, a new incoming bundle is converted into heat; but if the
reaction center is available, then a much smaller fraction is converted into
heat and so the energy losses are limited.