Chill‐induced wilting and hydraulic recovery in mung bean plants

The hydraulic conductance of roots of chilling‐sensitive mung bean plants is reduced markedly at low temperatures. When roots are chilled suddenly under high irradiance, or when plants with roots chilled in the dark are exposed to a natural dawn, the stomata remain open for several hours. During this period the plants may wilt severely if the evaporative demand is sufficiently large. Under lower evaporative demand and less severe wilting, the plants may subsequently rehydrate. Following root chilling there is a rapid (> 30 min) initial change in root conductivity (3. 2‐ fold). Within hours the hydraulic conductivity of the pathway from stem xylem to leaf tissue decreases dramatically. Within 1 d, the hydraulic conductivity of the roots decreases further (4. 5‐fold). Over 5 d these large resistances disappear and conductivity recovers to a value greater than at the start of chilling. This response and stomatal closure allow the plant to rehydrate to a condition similar to that of controls. There is no simple relation between this hydraulic recovery and the accumulation of abscisic acid in the roots.