Responses of Stomatal Conductance in Field-grown Maize Leaves to Certain Environmental Factors over a Long Term.

Abstract

Using measurements made under varying environmental conditions for a long period (1992-1994) in a maize field, we examined the characteristics of stomatal response to environmental variables. We found that, the characteristics could not be specified by a single relationship between the stomatal conductance and environmental variables. If the nature of the response was examined by dividing into a long-term variation and a diurnal variation, and by separating into two processes of both stomata opening and closing, the characteristics in each process could be clarified.The response functions and the relative importance of each environmental factor to the stomatal conductance were different for long-term and diurnal periods. For any particular day, the stomatal conductance was influenced by both the potential stomatal conductance (PSC) and the relative degree of stomatal opening (RDO), in which PSC was determined by the mean of environmental variables and RDO depended on the relative variation of environmental factors in daytime.In the processes of stomatal opening and closing, the curves of stomatal response to photosynthetic photon flux density and to leaf water potential showed an identical tendency, but stomatal response to saturation deficit and to leaf temperature in the two processes differed remarkably and showed a hysteresis phenomenon.