石漠化树种圆叶乌桕对干旱胁迫的生理响应

Physiological responses of the limestone endemic plant Triadica rotundifolia seedlings to drought stress

【目的】探讨圆叶乌桕Triadica rotundifolia幼苗对干旱胁迫的生理响应机制,为深入研究圆叶乌桕的抗旱性能提供基础依据,并为石漠化地区植被恢复及造林树种选择提供理论支持。【方法】以2年生圆叶乌桕幼苗为试材,通过盆栽试验连续监测其在干旱胁迫下叶片各项生理指标的动态变化。【结果】随着干旱胁迫的加剧,圆叶乌桕幼苗叶片相对电导率和游离脯氨酸含量显著上升,干旱末期分别达到峰值37.42%和197.18μg·g-1;超氧化物歧化酶(SOD)总活性、丙二醛含量和可溶性蛋白含量均呈现先升后降的趋势,分别在干旱第18、21和21天达到峰值159.19 U、31.89 nmol·g-1和2.31 mg·g-1。【结论】在不同干旱胁迫时期圆叶乌桕的生理响应机制不同,在轻度与中度干旱时期,体内抗氧化防御系统的积极防御与渗透调节能力的提高协同作用,以增强抗旱能力,在重度干旱时期,主要以渗透调节为主。总体而言,圆叶乌桕幼苗具有一定的耐旱潜能,是石漠化地区生态恢复的理想树种。

[ Objective ] To study physiological response mechanisms of Triadica rotundifolia when subjec- ted to drought stress, thus providing a fundamental evidence for further exploring its drought resistance and a theoretical support for afforestation tree species selection and vegetation restoration in limestone are- as. [ Method ] Pot experiment using 2-year-old T. rotundifolia seedlings was set up for observing the dy- namic changes of the leaf physiological indexes of T. rotundifolia seedlings under drought stress. [ Re- sult ] With the development of drought stress, electrolyte leakage rate and proline content increased signif- icantly, and peaked at the end of stress （32 days）, with the values of 37.42% and 197.18μg·g^-1 re- spectively. SOD activity, MDA and soluble protein contents first increased and then decreased, and peaked at the 18th, 21th and 21th days with the values of 159. 19 U, 31.89 nmol ·g^-1 and 2.31 -1 mg ·g^-1 respectively. [ Conclusion] The physiological response mechanisms of T. rotundifolia are differ- ent at different drought stress periods. Specifically in the light and moderate stress periods, drought re- sistance is enhanced by increasing the activities of protective enzymes combined with osmotic adjustment, but mainly by osmotic adjustment under severe stress. In general, 7： rotundifolia has certain ability of drought tolerance, thus it is one of the suitable species for ecological restoration in limestone areas.