Measurement of Stomatal Conductance and Transpiration in Maize (Zea mays L.) Fields

Measurement of stomatal conductance and transpiration in maize fields was conducted during the summers of 2002 and 2003. The diurnal variation of stomatal conductance and transpiration were investigated. The responses of stomatal conductance to environmental factors were discussed. It was observed that the responses of relative stomatal conductance to relative environmental variables are more sensitive in the morning than in the afternoon, this indicated the occurrence of a hysteresis phenomenon. A combination model was used to model the response of stomatal conductance to photosynthetic photon flux density, saturation deficit and leaf temperature. The root mean square error RMSE and relative root mean square error RRMSE are 0.06 and 14.32%, respectively. Moreover, the comparison between measured and estimated transpiration showed that there is a linear correlation between them. Finally, the development of canopy transpiration during some periods in relation to potential evapotranspiration, which was calculated by using the Penman equation with some meteorological variables and in relation to precipitation, also discussed in this paper.