EFFECTS OF WATER STRESS ON PHOTOSYNTHESIS OF WHEAT LEAVES AND THEIR RELATION TO DROUGHT RESISTANCE
(?)hangguan Zhou-ping and Chen Pei-yuen (Northwest Institute of Soft and Water Conservation, Academia Sinta and the Ministry of Water conservancy, Yangting, Shaanxi 712100)
Two cultivars of wheat(Drought resistant Feng kang No. 13 and Drought sensitive Zheng yin No. 1) seedings were used to determine the effect of water stress on photosynthesis. The results are as folloas: under mild water stress, net photosynthetic rate (Pn), stomatal couductance (Gs) and intercellutar CO_2 concentration (Ci) deoreased, but stomatal limiation (Ls) inc eased, which shows the decrease in Pn is mainly due to stomatal factors, However, under medium and serious warer stress,Pn,Gs,Ls, O_2-evolution rate of leaf discs, Hill reaction, chlorophyll fluorescence, and apparent quautum yield, but Ci increased. These results suggest that the decline of Pn is due mainly to non-stomatal factors. When subjected to water stress, the shift from stomatal factor to non-stomatal factor oceurred eariler in Zheng yin No. 1 than Feng kang No.13.