外源水杨酸预处理对高温胁迫下白菜耐热性和光合特性的影响

采用叶片喷施水杨酸（SA）的方法，研究高温胁迫下外源SA预处理对‘夏帝’和‘苏州青’2个白菜品种耐热性和光合特性的影响。结果表明：SA预处理降低了高温胁迫下白菜叶片的电解质渗透率、MDA和脯氨酸含量以及净光合速率（R），从而缓解高温对质膜的过氧化伤害，并且通过提高可溶性糖和可溶性蛋白含量、SOD和POD活性来适应高温环境；然而SA预处理对气孔导度（GS）和蒸腾速率（功的影响在2个品种中变化相反，而对胞间CO2浓度（G）的影响差异不大。与耐热性较强的白菜品种‘夏帝’相比，耐热性较弱的品种‘苏州青’经SA预处理对缓解高温胁迫的影响效果更为明显。

Effects of Exogenous SA Pretreatment on Thermotolerance and Photosynthesis in Pakchoi under High Temperature Stress

To study the effects of exogenous salicylic acid pretreatment on thermotolerance and photosynthesis, two pakchoi varieties, ＇Xia-di＇ and ＇Suzhou-qing＇, were sprayed with salicylic acid （SA） and then subjected to high temperature stress. The results showed that SA pretreatment prevented lipid peroxidation on pakchoi leaves under high temperature stress by reducing the electrolyte leakage, MDA content, proline content and net photosynthetic rate （P.）. Meanwhile, the soluble sugar content, soluble protein content, SOD activity and POD activity increased to make the pakchoi adapt to high temperature. However, two pakchoi varieties showed the opposite trend beween stomatal conductance （Gs） and transpiration rate （Tr） after spraying SA, with no significant alteration on intercellular CO2 concentration （Ci）. As compared with heat tolerant cultivar ＇Xia-di＇, the effects of SA pretreatment on heat susceptible cultivar ＇Suzhou-qing＇ were more significant under high temperature stress.