苜蓿叶片及根系对水分亏缺的生理生化响应

利用PEG-6000模拟研究水分胁迫(ψ_s=-0.2 MPa)48 h,后复水48 h,阿尔冈金和陇东苜蓿(Medicago sativa L.)品种幼苗根系与叶片的渗透调节作用及抗氧化酶活性的变化。结果表明:叶片的渗透调节能力及抗氧化酶活性均强于根系;受到水分胁迫后,叶片与根系水势、渗透势及饱和渗透势明显下降并随着时间的延长而逐渐降低;但抗氧化酶(SOD、POD和CAT)活性显著增强并随着胁迫的延续而保持高活性;细胞膜相对透性在胁迫中后期逐渐增大,MDA开始累积;叶片脯氨酸、可溶性糖、K⁺和可溶性蛋白含量随着胁迫时间的延长亦逐渐累积,根系可溶性糖含量逐渐显著升高,脯氨酸含量没有明显变化,而可溶性蛋白和K⁺含量呈现下降趋势;复水后产生一定的恢复补偿效应,但叶片生理代谢未能恢复到正常水平;陇东与阿尔冈金苜蓿抗氧化酶活性间存在差异,且二者对水分胁迫的适应能力亦略有差别。

Physiological and Biochemical Responses of Leaves and Roots of Alfalfa (Medicago sativa L. ) to Water Stress

The changes of osmotic adjustment and anti-oxidative enzyme activities in seedling leaves and roots of two cultivars of alfalfa(Medicago sativa L.cv.Longdong and M.sativa L.cv.Algonquin) was studied under water stress mimicked by PEG-6000 solution(ψ_s=-0.2 MPa,stress period 48 h,then rehydration 48 h).The results show that the osmotic adjustment capability and anti-oxidative enzymes activity were stronger in leaves than those in roots.Water potential,osmotic potential,and saturated osmotic potential in roots and leaves were significantly decreased along with the progress of water stress.However,the activities of anti-oxidative enzymes(SOD,POD,and CAT) in both leaves and roots significantly increased under water stress and maintained high activity during period of water stress,the membrane permeability and MDA increased obviously since middle period of water stress.Simultaneously,the contents of free proline,soluble sugar,K⁺,and soluble protein in leaves accumulated gradually with the progress of water stress.Soluble sugar content in roots was increased gradually under water stress and the contents of K⁺ and soluble protein were declined gradually,while no significant changes for free proline content.After rehydration,physiological metabolism in leaves did not recover to the control level although the repair and compensation mechanism was induced.In addition,there were differences in anti-oxidative enzyme activities and enduring capability to water stress between two tested alfalfa cultivars.