Get touchy feely with plants: Gently rubbing them with your fingers can make them less susceptible to disease

Forget talking to plants to help them grow, gently rubbing them with your fingers can make them less susceptible to disease, a paper in the open access journal BMC Plant Biology reveals.

Gently rubbing the leaves of thale cress plants (Arabidsopsis thaliana) between thumb and forefinger activates an innate defense mechanism, Floriane L'Haridon and colleagues report. Within minutes, biochemical changes occur, causing the plant to become more resistant to Botrytis cinerea, the fungus that causes grey mould.

Rubbing the leaves is a form of mechanical stress. Plants frequently have to deal with mechanical stress, be it caused by rain, wind, animals or even other plants. Trees growing on windy shorelines, for example, sometimes respond by developing shorter, thicker trunks.

But plants also respond to more delicate forms of mechanical stress, such as touch. Some responses are obvious -- the snapping shut of a Venus fly trap, the folding leaflets of a touched touch-me-not plant (Mimosa pudica) -- whilst some are more discrete. Plants also launch an arsenal of 'invisible' responses to mechanical stress, including changes at the molecular and biochemical level.