Plants respond to future enemies

It is not yet understood how the information is carried to the reproductive organs. Mustard plants produce seed faster when butterflies lay their eggs on the plant. This is the plant’s way of safeguarding its reproduction when the caterpillars hatch out. This remarkable conclusion was drawn by Wageningen entomologists, who explain it in an article in Functional Ecology this week. PhD student Dani Lucas Barbosa studied the mustard plant’s response to caterpillars from the moment the butterflies lay their eggs on the plants until the point at which the caterpillars bring their period of devouring leaves and flowers to a close. To her surprise the mustard seed speeds up its seed production before the larvae have left the eggs. By the time the larvae are devouring the flowers, the seed has already been formed. Like this, the plants prevent a serious reduction in their reproduction because the caterpillars eat the flowers but not the seeds of the mustard plant. ‘We have found a new strategy used by plants to defend themselves from their predators,’ says supervisor Joop van Loon. It is not yet understood how the information is carried from the leaves covered in butterfly eggs to the reproductive organs in the plant. Swiss plant scientists had already established that Arabidopsis thaliana, a close relative of the mustard plant, displays higher activity in genes involved in plant defence when it comes in contact with butterfly eggs. ‘Perhaps the information route goes through the plant’s vascular system, or else through volatile substances,’ says Van Loon.