Red light regulates nectar secretion
Flowering plants produce nectar to attract insect pollinators. Some plant species, such as the Lima bean, not only secrete nectar from their flowers but also from so-called extrafloral nectaries to attract ants which in turn fend off herbivores. Scientists at the Max Planck Institute for Chemical Ecology in Jena, Germany, have discovered that the production of extrafloral nectar is light dependent. Using a special photoreceptor, the phytochrome, scientists have shown that the plants are able not only to distinguish between day and night, but also to adapt their nectar secretion to current light conditions. The phytochrome probably influences the regulation of a special enzyme that binds the plant hormone jasmonic acid to the amino acid isoleucine. The emerging molecule affects the secretion of extrafloral nectar in such a way that the plant's defence against herbivores is most effective whenever herbivory is most likely - or, more precisely, during the day...