RESPONSES OF WATER POTENTIAL, TRANSPIRATION RATE AND STOMATAL RESISTANCE OF LEAVES IN MAIZE, SORGHUM, SESAME AND COWPEA GROWN IN THE FIELD TO ENVIRONMENTAL FACTORS
Jing Jia-hai and Ma Shu-shang (Northwestern Agriculture University, Yangling, Shaanxi 712100)
Relations between environmental factors and diurnal variations of leaf water potential (Ψ_(WL)) , stomatal resistance (rs) and leaf transpiration rate (TR) of maize, sorghum, sesame and cowpea grown in the field under various soil water were studied. The results from the experiments showed that Stomatal opening and closing of four kinds of crops were strongly correlated with light intensity, rs was high when stomat closed in darkness, and rs was low when stomat opened in the light, Ψ_(WL) and TR were closely related to environmental factors such as light intensity,air temperature,relative humidity (RH), water potential of water vapor in the air (Ψ_(WL)), and so on. The correlation coefficients between Ψ_(WL),TR and air temperature, RH, Ψ_(WV), light intensity were significant at 0.05 or 0.01 level. Ψ_(WL) of four kinds of crops described a sinusoidal curve with time, with minimum around 1300-1500 h and maximum before dawn. The lower Ψ_(WV) at noon and soil water content yere, the lower Ψ_(WL) were. TR of four kinds of crops continually increased with time in the morning; it got to maximum value at 1300-1500 h; and then it decreased slowly before dusk; minimum value of TR in a day was in the night. Ψ_(WL) and TR for drying treatment were lower than for irrigation treatmeat, but rs for drying treatment higher than for irrigation treatment.