PEG诱导水分胁迫下喜旱莲子草的生理适应性

采用PEG-6000模拟水分胁迫处理外来入侵种喜旱莲子草(Alternanthera Philoxeroides)(Mart.)Griseb.)无性繁殖体,测定了5 d中叶片Chl、膜透性、可溶性蛋白含量、MDA含量及几种抗氧化酶活性,旨在探讨喜旱莲子草对不同强度胁迫的生理适应性机制.结果表明:-0.15 MPa PEG胁迫下Chl、膜透性、MDA含量变化很小;-0.30 MPa PEG胁迫下膜透性和MDA含量均小幅升高,Chl含量先升后降,-0.50 MPa PEG胁迫下,Chl含量呈下降趋势,膜透性和MDA含量在第5日达到峰值.可溶性蛋白含量在3种处理中均先升后降,但基本都维持在处理前水平之上.SOD、POD、CAT等抗氧化酶活性在-0.15 MPa PEG胁迫下维持不变或略有上升,在-0.30 MPa和-0.50 MPa PEG胁迫下呈先升后降的变化趋势,但活性峰值出现在不同的处理时期,且降低后的各酶活性仍维持在一定水平上.实验表明,在低水分胁迫下,喜旱莲子草通过其体内活性氧清除系统活性的维持或升高来解除活性氧毒害,以保证活性氧的产生和猝灭处于动态平衡.即使是高渗透胁迫,喜旱莲子草通过抗氧化酶之间的相互协调在一定时期仍能维持活性氧代谢平衡,并阻止或减弱膜脂过氧化的伤害.但随着较高强度胁迫处理时间的增加,抗氧化酶活性降低,膜脂过氧化增加.

Physiological adaptation of Alternanthera philoxeroides under water stress condition induced by polyethylene glycol

Water stress may induce active oxygen species generation and cause injuries to plant. The objective of this study was to examine the mechanism of physiological adaptation of Alternanthera philoxeroides (Mart.) Griseb, an alien invasive species, under three water stress conditions. A. philoxeroides plants grown in 1/2 Hogland nutrient solution were treated with polyethylene glycol 6000 corresponding to water potential of -0.15 MPa, -0.30 MPa and -0.50 MPa. Chlorophyll content, membrane electrolyte leakage, soluble protein, MDA and activities of several antioxidant enzymes were measured. Chlorophyll content, membrane electrolyte leakage and MDA content of plant tissue did not change markedly under -0.15 MPa water potential, but increased slightly when the water stress was induced by -0.30 MPa PEG, whereas the -0.50 MPa PEG stress led to decrease in chlorophyll content and appearance of the peak values of membrane electrolyte leakage and MDA content on the 5 th day. However, soluble protein content initially increased and then decreased under all of the three different water stress conditions, so that a level higher than that of the control resulted. Activities of antioxidant enzymes (SOD, POD and CAT) remained unchanged or increased slightly under condition of -0.15 MPa PEG stress, but showed an initial increase followed by decrease under both -0.30 MPa and (-0.50 MPa) PEG stress, although the peak values occurred at different time periods under different degrees of water stress. The enzyme activities remained at normal level on the 5 th day. Furthermore, as water stress was aggravated, antioxidant enzyme activities decreased while lipid peroxidation increased. The experiment suggested that A. philoxeroides were capable of surviving low water stress, and its ability of adaptation to water stress was related to the maintenance of or increased capacity to the elimination superoxided radicals by the action of antioxidant enzymes.