How we all laughed when Prince Charles revealed years ago that he spoke to plants. "They respond I find," he said in one of his most infamous exchanges with reporters. Well it seems the future King of England may have been on to something. A new study has presented the strongest evidence yet that grasses and flowers can actually communicate, if not with humans then at least with each other.
At the heart of the study, conducted by Justin Runyon and colleagues at Pennsylvania State University and reported in today's Science , is an unremarkable looking weed called dodder. Dodder is a parasite which makes up for its inability to photosynthesise very well by wrapping itself around the stems of other plants and sucking out their nutrients. The yellow weed is bad news for farmers in particular, hence dodder's nickname strangle-weed or witches' shoelaces. The study looked at the way the pesky parasite finds its victims and ran an experiment in which dodder plants were given a choice of plants to wrap themselves around. It turned out the weed favoured some plants over others. While tomato plants, for instance, were popular targets others, such as wheat, were not. Looking deeper the scientists found an explanation for this: wheat emits an airborne chemical (or volatile) that somehow repels the dodder. In effect, it shouts "stay away from me". They think the tomato plants may have been sending the opposite signal out, releasing volatiles that say "come and get me". Previous studies have suggested that plants under siege from herbivorous insects send messages to other plants telling them to boost their chemical defences before they too are infested, but this is the clearest evidence yet that plant-to-plant chatter really does exist. "The results go a long way toward convincing people that plant-plant interaction via volatiles is a real phenomenon," says Eran Pichersky, an evolutionary biologist at the University of Michigan, Ann Arbor.