柠条锦鸡儿和沙拐枣主根暴露后的生理响应及抗逆机理

Physiological response and stress tolerance mechanisms of Caragana korshinskii and Calligonum mongolicum suffering from taproot exposure

风蚀是固沙植物根系暴露的主导因素。在宁夏白芨滩国家级自然保护区对8年生的柠条锦鸡儿(Caragana korshinskii)和沙拐枣(Calligonum mongolicum)成株进行3个深度(10、20、30 cm)的主根暴露处理,并揭示其生理过程及适应机理。结果表明:(1)柠条锦鸡儿主根暴露10 cm的各项生理指标在21 d内与对照间均无显著差异,暴露至30 cm深度其MDA含量、Pro含量、叶绿素含量、Chl(a/b)、CAT活性在第7天均与对照间存在显著差异,至第21天又恢复至对照组水平,可溶性糖和SOD与对照间始终无显著差异,由此判断主根暴露10 cm对柠条锦鸡儿未产生逆境胁迫,暴露30 cm深度后的7 d内通过启动以游离脯氨酸为主的渗透调节系统以及增强CAT活性清除H_(2)O_(2),使其逐渐恢复至生理稳态;(2)沙拐枣根系暴露10 cm的第7天通过可溶性糖的积累和Chl(a/b)的升高调节生理稳态,暴露20、30 cm深度的第14天和第21天,SOD、CAT、叶绿素含量较对照均显著下降(P<0.05),即其抗氧化酶系统开始紊乱,光合作用下降。综上,主根暴露30 cm深度仅在暴露早期对开花期的柠条锦鸡儿生理有影响,而展叶期的沙拐枣在根系暴露20 cm深度以上,即表现出中重度干旱胁迫响应。

Wind erosion is the dominant factor of root exposure of sand-fixing plants.Eight years old plants of Caragana korshinskii and Calligonum mongolicum from Baijitan Nature Reserve of Ningxia were used as the experimental materials in this study.The taproots were exposed by three depths of 10 cm,20 cm,and 30 cm,and their physiological processes and adaptation mechanisms were analyzed.The results showed that:(1)there was not any significant difference between the physiological parameters of Caragana korshinskii and those of the control within 21 days after the taproot was exposed by 10 cm.Caragana korshinskii showed significant differences in malondialdehyde content,Pro content,chlorophyll content,Chl(a/b),and catalase on the 7 th day with the taproot being exposed by 30 cm compared to the control.These physiological parameters returned to the control level on the 21 st day.Both soluble sugar and superoxide dismutase values were not significantly different compared to the control from the beginning to the end.Therefore,10 cm exposure of the taproot did not cause stress to Caragana korshinskii.Within seven days after the exposure by a depth of 30 cm,H_(2)O_(2) was removed by activating an osmotic adjustment system mainly driven by free proline and enhancing CAT activity,so that the plant gradually returned to a physiologically stable state.(2)Calligonum mongolicum regulated the physiological homeostasis by an accumulation of soluble sugars and an increase of Chl(a/b)on the 7 th day after the taproot being exposed by 10 cm.The SOD,CAT,and chlorophyll contents were significantly lower than those of the control(P<0.05)on both 14 th and 21 st days with the taproot being exposed by a depth of 20 cm and 30 cm,that is,the antioxidant enzyme system began to be in a state of disorder and the photosynthesis decreased.In summary,the exposure of the taproot by the depth of 30 cm affected the physiology of Caragana korshinskii at the flowering stage only at the beginning of the treatment.In contrast,Calligonum mongolicum at the leaf expansion stage showed a response of moderate to severe drought stress with taproot exposure of more than 20 cm.