Effect of Heat Stress on Photosynthesis of Pepper Cultivars at Seedling Stage

Three pepper(Capsicum annuum L.) cultivars with different adaptability to heat stress were used to study the effect of heat stress((40 ℃)) on photosynthetic characteristics.Results showed that net photosynthetic rate(P_n) of all cultivars considerably were inhibited under high temperature for 0-(12 h),total chlorophyll increased earlier and decreased later,but the range of heat-tolerant variety Xiangyan 5 was less than that of heat-sensitive variety Sujiao 5.P_n and total chlorophyll could be used to evaluate the heat tolerance ability of pepper.In addition,Stomatal conductance(G_s) and transpiration rate(T_r) decreased while intercellular CO_2 concentration(C_i) increased at first stage,then G_s and T_r had the tendency to go up while C_i almost unchanged after(12 h),which showed that the effect of non-stomata was mainly occupied to decrease P_n in this experiment.