紫外线B对水稻叶组织中活性氧代谢及膜系统的影响

Effects of Ultraviolet-B Radiation on Active Oxygen Metabolism and Membrane System of Rice Leaves

增强ＵＶ－Ｂ处理下，水稻叶片的Ｏ净产生速率、Ｈ２Ｏ２和ＭＤＡ含量以及膜透性都显著增加，敏感性弱的品种Ｏ２净产生速率和膜伤害程度较低。在ＵＶ－Ｂ处理初期活性氧清除系统的水平增高，但随着处理时间的延长，ＳＯＤ、ＣＡＴ和ＡＰ活性以及ＡＳＡ含量降低，其中ＡＰ和ＳＯＤ活性的下降最为明显，而敏感性弱的品种ＳＯＤ活性始终高于敏感性强的品种。处理１４ｄ后去掉ＵＶ－Ｂ，再经则１４ｄ上述各指标均恢复到与对照相近的水平。根据这些结果推测，水稻的ＵＶ－Ｂ伤害可能主要是由于ＳＯＤ活性的降低而导致Ｏ增生和膜脂过氧化。

The changes in membrane permeability and active oxygen metabolism inrice leaves exposed to enhanced ultraviolet-B were investigated. Two rice cultivars (IR74 and Dular) were grown ina greenhouse for ten days and thentreated with four levels of UV-B (0.0,6.0, 13.0, 19.1 kJ m-2 d-1) for 28days in a glasshouse. UV-B radiationcaused significant increased in electrolyte leakage, malindialdehyed(MDA) content and the net rate of O generation (Figs. 2,3). These increases were greater in the sensitive cultivarDular than in the less-sensitive cultivarIR74 under high radiation (13.0 and19.1 kJ m-2 d-1 ) and long UV-B exposure (28 days) (Fig. 1 ). The extentsof the changes in O and MDA contentwere greater than those of electrolyteleakage and H2O2 content. AscorbatePeroxidase activity was significantly reduced and other antioxidants (superoxide dismutase, catalase, ascorbic acidand glutathione) were enhanced duringshort exposure to UV-B radiation (14days ). SOD activity, however, wasreduced after 14 day treatment (Figs.5, 6 ). The less-sensitive cultivar retained a higher SOD activity than thesensitive one under high radiations. Theparameters described above returned tolevels similar to those of the control(0.0) after UV-B radiation (13.0 )had been stopped for 14 days. Based onthese results, it is deduced that UV-Bin jury to membrane may be correlatedto excessive production of O2 which induces an increase in lipid peroxidation,while O2 accumulation may be causedby the inhibition of SOD. The varietaldifference in UV-B sensitivity of ricecultivars may involve the difference inSOD level, which affects the rate ofbreakdown of O .