Stressed plants ‘cry’ — and some animals can probably hear them

Thirsty or stressed plants produce ultrasonic clicks that, when processed to make them audible to humans, sound like popping popcorn. Tobacco (Nicotiana tabacum) and tomato (Solanum lycopersicum) plants that needed water, or that had recently had their stems cut, produced up to roughly 35 clicks per hour. Well-hydrated and uncut plants made only about one sound per hour. The noises possibly come from air bubbles forming or breaking in the plants’ xylem, the tubes that transport water and nutrients from the roots to the stems and leaves. The sounds could be used to monitor plants in farming and horticulture.