Research proved that plants sense--and react to--the presence of hungry, leaf-eating worms. Their response, as studied, was to emit an odour. This alerted other plants to the presence of a predator. But it also served to call in what modern military planners would term air support. Wasps, the natural enemies of worms, were drawn by the odour to the plant where they either devoured the worm or injected it with eggs that later killed it.

　　The study raised the interesting question: at the start of the process described, did the plants actually experience something that could be termed fear? A debate over this began in 1966 when a lie detector expert, Cleve Backster, connected a plant to a polygraph (lie detector). He said the machine registered changes as soon as he began to think about burning the plant's leaves.

predator：掠食者
wasp：黄蜂
polygraph：测谎仪