Stomatal Behaviour of Kenaf and Sorghum in a Semiarid Tropical Environment. I. During the Night

Abstract

The extent of night-time stomatal opening in field-grown kenaf (Hibiscus cannabinus L.), a C₃ dicotyledon, and sorghum [Sorghum bicolor (L.) Moench], a C₄ grass, and the factors controlling the opening were studied at high and low soil water status. Since saturation deficit (δe) and temperature varied together in the field, the response of stomatal conductance (g_s) to these individual factors was determined under controlled environment conditions in a leaf chamber apparatus.

At both high and low soil water status, the stomata of sorghum were closed from sunset to sunrise, whereas with kenaf partial stomatal opening was observed throughout the night. Initiation of night opening occurred in response to decreasing temperature, but the degree of opening was determined by plant water status. The importance of night-time stomatal opening on the water relations of the crop is discussed.