干旱胁迫下桑树叶片中超氧阴离子的变化规律

摘要

该研究以6个四川桑树品种为对象,对供试桑树品种进行连续的人工干旱处理,利用生理方法明确保护酶系(SOD)的变化规律,并采用硝基四氮唑蓝(NBT)还原试验进行超氧阴离子O-2·组织化学的可视化检测.结果表明:随着干旱胁迫的加剧,SOD的含量明显高于对照组,其中SOD活性呈先升后降的变化趋势,而超氧阴离子一直呈加重的趋势.6个桑树品种的SOD含量从正常到中度胁迫都呈现不同程度的上升趋势,上升趋势明显的品种是九龙拐和湖桑32,上幅分别为62.7%和60.1%,其次是云桑1号和荷叶白一号上幅,分别为52.2%、58.2%,油桑和充桑的上幅为50.8%和47.4%,说明SOD正发挥着积极的作用.在中度胁迫之后SOD的含量与活性氧的水平表现出相反的趋势,原因可能是随着干旱胁迫的加剧,O-2·达到最大值且超出一定域值,从而导致SOD活性的降低.通过电镜观察发现,超氧阴离子由叶脉向周围扩散,同时面积逐渐增大.其中,抗旱性强的品种湖桑32叶片表面茸毛比较长,且基部膨大,端部有明显的刺状突起,而抗旱性弱的品种荷叶白1号叶片表面茸毛比较细短且端部的刺状突起不明显,因此推测叶片表面茸毛的特性与抗旱性存在一定关系.%We used six mulberry varieties in Sichuan Province as the research object, by using physiological method and used NBT test to determine the activities of SOD and to study the changes of super oxygen anion ( O-2·) in the leaf blade tissues under different drought conditions. The results showed that the SOD content of six mulberry varieties were signifi-cantly higher than those of the controls. The change trend of SOD activity was raised and then fell later, and super oxide anion grew steadily. Possible reasons were that reactive oxygen beyond a certain threshold, which led to SOD activity de-creased. Under different drought conditions, from normal stress treatment to middle stress, the SOD content of six mul-berry varieties also demonstrated rapid growth. Jiulonggui and Husang 32 showed a rising trend and increased by 62.7%and 60.1% obviously;followed by Yunsang 1 and Heyebai 1 raised to 52.2%and 58.2%;Yousang and Chongsang were increased to 50.8% and 47.4%, respectively. This showed that the SOD played an active and effective role to reduce O-2·. After moderate stress level of SOD and active oxygen showed the opposite trend, which showed significant degrada-tion effect, and had a mechanism of active oxygen injury. Super oxide anion spread around the veins, area of super oxide anion gradually increased, which were observed by transmission electron microscope. It is obeserved that Husang 32 has its ability to eliminate the superoxide free radical, and its drought resistance abilities and leaf blade surface hairs were higher than that of Heyebai 1. Hence, it can be inferred that the length of leaf blade surface hairs has a certain relation-ship with drought resistance.