Modeling stomatal conductance of durum wheat(Triticum durum)in drylands by field experiments

摘要

Stomata play a very important role in preventing leaf surface from reaching excessive temperatures through the control of plant transpiration and its associated cooling effect.They thus have important function in adaptation of plants to drought-prone environments.This research aimed at 1)studying the variability and responsiveness of durum wheat(Tricticum durum)stomatal conductance(gs)to change in the environmental factors and time,and 2)modeling gs of durum wheat applying Jarvis model.An experiment was conducted in northern Syria,which has arid and semi-arid environment,involving four irrigation treatments(rainfed-0％,full irrigation-100％,and two intermediate levels of 33％and 66％of full irrigation).The gs was significantly affected by soil water content,and even the crop in full irrigation treatment experienced water stress before irrigation.In the rainfed treatment,gs values were very small compared with other treatments.The performance of the model was evaluated by the nonlinear least squares method,and the simulated results were in good agreement with observations.Also sensitivity analysis was performed on parameters used in the model by running the model with different scenarios where the parameters were varied by ±20％from the optimum value.The analysis showed that the model was mostly sensitive to the variations in soil water potential.On the other hand,the model was insensitive to variations in vapour pressure deficit(VPD)because of small range of VPD values in the study.These results suggest that identifying the parameter in the equation about soil water potential and measuring gs in the wide range of VPD would improve the model.