水杨酸对盐胁迫下沙冬青幼苗抗氧化酶活性及PSⅡ光化学效率的影响

濒危植物沙冬青Ammopiptanthus mongolicus为亚洲中部荒漠地区唯一的常绿阔叶灌木,具有较高的保护和园林绿化价值.为了解水杨酸对沙冬青在盐胁迫下的缓解作用,使用水培方法培养沙冬青幼苗,测定其在w=1.3%NaCl胁迫下经不同浓度水杨酸处理后的抗氧化酶活性、PSⅡ光化学效率及其他与植物抗性有关的生理指标的变化.结果表明,0.5 mmol.L-1水杨酸处理下,根和茎叶鲜质量比盐胁迫组分别提高了100%和85%,总叶绿素含量达到盐胁迫组的1.3倍;而1 mmol.L-1水杨酸可使根和茎叶鲜质量均提高90%,总叶绿素含量达到盐胁迫组的1.7倍.这2种浓度的水杨酸均可使叶绿素荧光参数恢复到正常对照水平.水杨酸可以显著增强超氧化物歧化酶(SOD)和过氧化物酶(POD)活性,其中1.0 mmol.L-1水杨酸处理下叶片与根部SOD酶活性分别比盐胁迫组升高了54%和68%;POD酶活性则分别提高了80%和117%,均显著高于对照组与盐胁迫组.同时,水杨酸还抑制了过氧化氢酶(CAT)的活性,减少丙二醛积累,从而缓解NaCl对沙冬青的胁迫.但是水杨酸浓度过高(达到2.0 mmol.L-1),沙冬青幼苗生长即受到抑制,各项生理指标均低于单纯盐胁迫下的幼苗.综合各项生理指标,水杨酸1 mmol.L-1的施用效果优于0.5 mmol.L-1.

Effect of Salicylic Acid on Antioxidant Enzyme Activities and Photochemical Efficiency of Ammopiptanthus mongolicus Seedlings Under Salt Stress

Ammopiptanthus mongolicus, an endangered evergreen leguminous shrub, endemic to the semi-arid desert region of central Asia, has higher protection and landscaping value.In order to understand the mitigative effect of salicylic acid on salt stress of A. mongolicus seedlings, the seedlings were treated with w=1.3% NaCl and different concentrations of salicylic acid (SA) under water culture.Antioxidant enzyme activities, photochemical efficiency of PSⅡ and other related physiological indexes were measured and analyzed.The results showed that 0.5 and 1.0 mmol·L~(-1)SA increased the fresh mass, the chlorophyll content and the Chl a/Chl b ratio, recovered fluorescent parameters (F_v/F_0,F_v/F_m and F_0) to normal level, enhanced SOD and POD activity obviously, inhibited CAT activity, and decreased MDA content.When the concentration reached 2.0 mmol·L~(-1), the seedlings growth were inhibited, every physiological indexes of the group were obviously lower than w=1.3% NaCl groups.The application effect of 1 mmol·L~(-1)SA was better than 0.5 mmol·L~(-1).