The short clip above shows what happens to an injured plant when a nibbling insect attacks the leaves of a plant: the entire plant is alerted to begin anticipatory defense responses.

Working in the model plant Arabidopsis, researchers recently showed that a systemic signal begins with the release of glutamate, which is perceived by glutamate receptor–like ion channels upon injury to a leaf. The ion channels then set off a cascade of changes in calcium ion concentration that propagate through the phloem vasculature and through intercellular channels called plasmodesmata. This glutamate-based long-distance signaling is rapid; within minutes, an undamaged leaf can respond to the fate of a distant leaf.

If plants react to injury more similarly to ...