Temperature-Induced Water Stress in Chilling-Sensitive Plants

Abstract

Cotton (Gossypium hirsutum) and bean (Phaseolus vulgaris) seedlings wilted when entire plants or roots alone were chilled in the light. The water relations and gas exchange characteristics of these chilling-sensitive species have been compared with a chilling-resistant species, collard (Brassica oleracea), following exposure to a chilling temperature at 5°C.

Chilling either whole seedlings or roots alone had little or no effect on leaf water potentials or gas exchange of collard seedlings but induced a rapid response in cotton and bean. Leaf water potentials were reduced below - 1.5 MPa within 1-2 h; however, this response was reduced when seedlings were chilled in the dark or when leaves or roots of bean were pretreated with abscisic acid. Chilling also caused a rapid reduction in photosynthesis but a more gradual decline in transpiration over the first 2-4 h due to the slow closure of stomata.

These results suggest that water deficits in chilling-sensitive seedlings when exposed to low temperature in the light are caused by a reduction in the hydraulic conductivity of the root membranes and by the loss of stomatal control in the leaves. The reduced flow of water into the plant through the roots and continued transpiration, because of the slow closure of stomata, bring about a rapid decline in leaf water potential and wilting of primary leaves.