高温胁迫后小白菜的补偿生长能力及防御机制

以小白菜品种“上海青”为研究对象，进行高温胁迫实验，设高温组（昼/夜温度为37℃/30℃）与对照组（25℃/18℃），对小白菜高温胁迫3d、6d和9d后在25℃/18℃下的生长及恢复情况进行研究。结果表明：高温下小白菜生长受到显著抑制，胁迫3、6、9d后干物质相对增长率分别比对照下降32.68%、82.86%、100.00%。高温引起叶片净光合速率（Pn）、气孔导度（Gs）、蒸腾速率（Tr）下降，胞间CO2浓度（Ci）升高，丙二醛（MDA）含量升高，同时小白菜启动高温防御应答机制，保护酶活性上升，可溶性蛋白积累，叶绿素含量提高。胁迫解除后，3d及6d胁迫组Pn、Gs、Tr升高，Ci下降，MDA含量、可溶性蛋白与酶活性下降，处理组与对照差异逐渐减小。3d胁迫处理小白菜在恢复期的6～9d呈现超补偿生长，补偿指数为1.10。6d处理则一直呈现低补偿，9d胁迫处理小白菜均在恢复过程中死亡。因此，超过3d的高温胁迫将引起小白菜的不可逆损伤。灰色关联分析表明，Pn、Gs、可溶性蛋白、MDA、叶绿素含量对小白菜的补偿生长起到关键作用，是小白菜实现补偿生长的内在驱动机制。

Compensatory Ability and Defense Mechanism of Chinese Cabbage under High Temperature Stress

Chinese cabbage was taken as experimental material, which were cultured in a climate chamber with 12h/12h photoperiod under 37℃/30℃ for 3d, 6d, and 9d respectively before transferred to normal conditions (25℃/18℃). The samples were then cultured for 9d for recovery. Chinese cabbage cultured constantly under 25℃/18℃ was set as the control. The results showed that the growth of Chinese cabbage was hindered significantly by high temperature. The growth rate was 32.68%, 82.86%, and 100.00% lower than the control after stressed for 3, 6, and 9 days, respectively. The net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr) decreased with increased treatment time of high temperature, while malondialdehyde (MDA) and intercellular CO2 concentration (Ci) increased. However, chlorophyll content, soluble protein, and antioxidant enzyme activities increased, which means defense mechanism of Chinese cabbage was motivated. During the recovery phase, the samples treated for 3 days and 6 days both increased in Pn, Gs, and Tr, while decreased in Ci, MDA content, soluble protein, and enzyme activities. The Chinese cabbage cultured under 37℃/30℃ for 3 days exhibited over- compensation during the 6th -9th day of recovery phase, the compensation index was 1.10. Chinese cabbage cultured under 37℃/30℃ for 6 days exhibited under-compensation, while which cultured for 9 days died during the recovery phase. The results indicated that high temperature treatment for more than 3 days can cause irreversible damage to Chinese cabbage. Grey correlation analysis revealed that the Pn, Gs, soluble protein, MDA, and chlorophyll content play key roles in the compensatory growth of Chinese cabbage, which were major driving factors for the compensatory growth of Chinese cabbage.