Rapeseed is one of the ten most important agricultural crops worldwide. In spring, the rapeseed fields with their bright yellow flowers are widely visible: this year winter rapeseed is being cultivated on 1.46 million hectares in Germany; at least 2.2 million tons of rapeseed oil can be expected. Beekeepers set up their beehives in the vicinity of rapeseed fields, so that the worker bees can gather nectar This ensures that the rapeseed flowers are pollinated and a high crop yield will be obtained. During her studies, a scientist from the Max Planck Institute for Chemical Ecology has discovered that the plant hormone jasmonic acid – known as a signalling molecule after herbivory – not only regulates flower development in the bud stage, but also triggers nectar production.
Jasmonic acid and related molecules are constituents of molecular signal transduction chains in plant tissues. These compounds – generally referred to as jasmonates – are synthesized when caterpillars feed on plants; they are signaling substances and belong to the group of plant hormones. By producing jasmonates the plant regulates its defense against herbivores e.g. by stimulating the synthesis of toxins. Moreover, previous studies have shown that jasmonates regulate the production of "extrafloral nectar". This particular nectar, which is produced by special glands called "extrafloral nectaries", has nothing to do with pollination, but attracts ants to the herbivore-attacked plants as defenders against their pests. The sugars in the nectar reward the ants for defending the plant. The same principle applies to floral nectar: nectar production in the flowers attracts and rewards pollinators which in turn contribute substantially to the seed yield. However, up to now, it has not been clear how nectar production is regulated in the flowers.