Dry Plants Warn Away Moths
Drought-stressed plants let out ultrasonic distress cries that moths use to avoid plants that canât support their offspring. In ideal circumstances, a plant is constantly pulling water up from the soil, through its roots, and out its leaves through transpiration. This creates a strong negative pressure â varying from 2 to 17 atmospheresâ worth â inside the plantâs xylem. If thereâs not enough water to keep the plantâs inner flow going, cavitation occurs â essentially a tiny vacuum bubble opens in the xylem. That cavitation isnât silent; it creates a click at ultrasonic frequencies above human hearing. But just because we donât hear it doesnât mean that sound goes unheard.
In fact, recent research suggests that, not only do moths hear the plantâs cavitation cries, female moths will avoid laying eggs on a healthy plant that sounds like itâs cavitating. Evolutionarily, this makes sense. Hatchlings rely on their birth plant for food and habitat; if an adult moth picks a dying, drought-stressed plant, its offspring wonât survive. It pays to be sensitive to the plantâs signs of distress. (Image credit: Khalil; research credit: R. Seltzer et al.; via NYTimes)
#acoustics #biology #cavitation #fluidDynamics #moths #physics #plants #science #transpiration