水杨酸对干旱胁迫下桔梗幼苗生理生化指标及相关基因表达的影响

为探讨桔梗对干旱胁迫的应答机制及水杨酸对桔梗抗旱性的影响，以桔梗幼苗为材料，研究外源添加不同浓度水杨酸处理下桔梗幼苗的抗旱性，对桔梗幼苗根和叶片中叶绿素、渗透调节物质、丙二醛含量及抗氧化酶活性进行测定，同时以actin为内参基因，采用实时荧光定量PCR方法检测叶绿素酸酯a氧化酶基因（CAO）、叶绿素合酶基因（CHLG）、过氧化物酶基因（POD）和吡咯啉-5-羧酸还原酶基因（P5CR）表达量的变化。结果表明，适宜浓度水杨酸处理可增加桔梗幼苗叶片中叶绿素、可溶性糖、可溶性蛋白和脯氨酸的含量，提高超氧化物歧化酶、过氧化物酶、过氧化氢酶活性，降低丙二醛含量；叶片中CAO、CHLG、POD、P5CR基因表达量与相应酶活性检测结果相一致。由此可见，外源添加水杨酸可提高桔梗幼苗叶片中CHLG、POD等基因的表达量，提高抗氧化酶活性，促进渗透调节物质的累积，有效提高桔梗的抗旱能力，为阐明桔梗对干旱胁迫的应答机制奠定基础。

Effects of Exogenous Salicylic Acid on Physiological and Biochemical Indexes and Related Gene Expression in Platycodongrandiflorus Under Drought Stress

In order to explore the response mechanism of Platycodongrandiflorum to drought stress and the effects of exogenous salicylic acid （SA） on drought resistance， the seedling of Platycodongrandiflorum was dealt with different concentrations of SA under different concentrations of PFG. The contents of chlorophyll （Chl）， malondialdehyde （MDA）， soluble sugar （SS）， soluble protein （SP）， proline （Pro） and activities of superoxide dismutase （SOD）， peroxidase （POD）， catalase （CAT） were determined. And the relative expression levels of chlorophyllide a oxygenase （CAO） and chlorophyll synthase （CHLG）， peroxidase （POD） genes related to Chlorophyll synthesis and pyrroline-5-carboxylate reductase gene （P5CR） related to proline biosynthesis were analyzed by the real-time fluorescence quantitative PCR. The results showed that exogenous salicylic acid in proper concentration could increase contents of Chl， SS， SP and Pro， improve activities of SOD， POD and CAT， reduce MDA content. And the relative expression levels of CAO， CHLG， POD and P5CR genes in leaves were consistent with the results of contents. In conclusion， exogenous salicylic acid could effectively improve drought resistance of Platycodongrandiflorus by increasing the contents of SS， SP， Pro and the activities of SOD， POD， CAT， which laid a foundation for dissecting the response mechanism of Platycodongrandiflorum to drought stress.