干旱胁迫对桑树叶片氧化损伤及超微结构的影响

Effects of Drought Stress on the Oxidative Damage and Ultrastructure of Leaf Cells in Mulberry

目的:进一步探索干旱条件下桑树的植物学特性、生理生化及细胞学响应特征,旨在为桑树抗旱育种及品种的筛选提供理论依据。方法:以四川桑品种湖桑32、德果1号作为研究对象,对供试桑品种进行连续的人工干旱处理,研究生理指标、叶片超微结构、活性氧(ROS)的变化规律特征。结果:随着干旱胁迫加剧,德果1号的水分饱和亏缺(WSD)和丙二醛(MDA)分别增加了192.24%、103.81%,显著高于湖桑32。脯氨酸(Pro)和脱落酸(ABA)变化规律呈上升趋势,在重度胁迫时湖桑32的ABA、Pro含量分别为250.66μg·g^-1、1.39 mg·g^-1,显著高于德果1号。湖桑32和德果1号的超氧化物歧化酶(SOD)、过氧化物酶(POD)酶活力呈现出先升后降的变化趋势,且在重度干旱胁迫下德果1号的ROS含量显著高于湖桑32,表明湖桑32具有较好的ROS清除能力。结论:随着干旱胁迫加剧,桑树体内防御系统崩溃、ROS清除机制功能异常,多种来源的ROS过度积累导致ROS爆发。过量的ROS严重损伤植物细胞,包括细胞膜、叶绿体、线粒体、细胞核等结构被破坏。

Objective:The study aimed at enriching the study of the botanical characteristics,physiological and biochemical and cellular mechanisms of mulberry adaptation to drought stress,and provide a theoretical basis for the selection of drought-resistant cultivars in returning farmland to mulberry in southwestern Sichuan.Methods:Mulberry variety of Deguo No.1 and Husang 32 in Sichuan Province were used as the research object.The physiological method and transmission electron microscope were used to explore the mechanism of physiological,biochemical and cellular differences caused by water stress.Results:Under drought stress,the water saturation deficit and malondialdehyde(MAD)increased by 192.24%、103.81%in Deguo No.1 and was significantly higher than in Husang 32.Further,the proline(Pro)and abscisic(ABA)in Husang 32 were 250.66μg·g^-1、1.39 mg·g^-1,respectively,which is higher than they were in Deguo No.1.Superoxide dismutase(SOD)and peroxidase(POD)are antioxidant enzyme that played a major role in the plant defense system against oxidative stress.The results showed that the activities of SOD and POD of Husang 32 were increased first and then decreased,and the activities of SOD and POD of Husang 32 were higher than that of Deguo No.1.The content of reactive oxygen species(ROS)in Deguo No.1 was higher than that in Husang 32,which was consistent with the phenotypic result.Conclusion:When these defense mechanisms failed to protect plants from reactive oxygen species,the cells died.As a result of over accumulation of ROS from various sources,the defense system broke down,resulting in ROS outbreak,destruction of other cells around,and serious damage to the cellular structure.The damage included changes in cell structure,destruction of chloroplasts,swelling of mitochondria and condensation of chromatin.