酸雨和UV-B对玉米幼苗光合速率和抗氧化酶活性的影响

以玉米( Zea mays L.)的两个品种渝糯7号和苏玉糯为研究材料, 研究酸雨与UV-B辐射单一因子和复合处理对植物光合作用及抗氧化酶活性的影响机理, 模拟酸雨[pH6.5(A0), 4.5(A1)和3.5(A2)]和增强UV-B辐射[0(B0), 2.88(B1)和5 76(B2)kJ·m-2·d-1]及其复合作用下, 玉米叶片光合速率, 膜脂过氧化程度, 抗氧化酶活性的变化.结果表明, 与对照相比, 酸雨或增强UV-B辐射单因素处理下两个品种的玉米幼苗所测生理指标有相似的变化, 基本表现为: 净光合速率和过氧化氢酶(CAT)活性降低, 质膜透性与丙二醛(MDA)含量增加, 过氧化物酶(POD)活性亦增加, 超氧化物歧化酶(SOD)活性随处理时间延长先升高后降低.复合处理下, 两个品种的玉米幼苗所测生理指标与对照相比也与单因素处理表现相似, 且随处理组合的不同, 复合胁迫下各指标的效果可能表现为协同效应, 但更多地表现为拮抗作用.以上结果说明, 模拟UV-B辐射升高和酸雨pH值降低促进了玉米叶片活性氧的代谢速率, 导致了抗氧化酶系统的紊乱, 抑制了光合作用.在复合处理下, 两个因子对不同指标在不同处理时间和复合水平下, 表现出一定的协同或拮抗效应可能与作物对环境变化产生一定的抗逆性和适应性有关.在不同时期两玉米品种对紫外辐射与酸雨敏感性不同.与苏玉糯相比, 渝糯7号对外界环境变化的抗性更大.

Effects of UV-B irradiation and acid rain on photosynthetic rate and antioxidant enzyme activities of maize seedlings

In order to reveal effects of acid rain (AR) and UV-B radiation (UV-B) singly and in combination on plant photosynthesis and anti|oxidant enzyme activities, the net photosynthetic rate, relative membrane permeability, malondialdehyde (MDA) content, and anti|oxidative enzyme activities in maize ( Zea mays L. ) leaves were studied under simulated acid rain ( pH=6.5(A0), 3.5(A1), 4.5(A2) ) and enhanced UV-B radiation ( 0(B0), 2.88(B1), 5.76(B2) kJ?m-2?d-1), both singly and in combination treatment in the green|house. The results indicated that the physiological traits in the maize breeds Yu Nuo 7 and Su YuNuo experienced similar changes under single AR and UV-B treatment. The treatments resulted in reduction of net photosynthetic rate and catalase (CAT) activity, increase of the relative membrane permeability, MDA content and peroxidase (POD) activity, while superoxide dismutase (SOD) activity increased first but decreased afterwards during the treatment. Under the combined stresses, compared with the control treatment (A0B0), the changes of physiological traits in both breeds of maize were similar to those under single factor treatment. For some traits, combined stress displayed a synergistic effect, with significantly stronger effects than those under single factor stress, whereas for most traits it displayed antagonistic effects. The results showed that both enhanced UV-B radiation and decreased pH of simulated acid rain accelerated ROS metabolism rates, which damaged the anti|oxidative enzyme system and reduction of photosynthesis. Taken together, the dynamic changes of physiological and biochemical indices under the dual stresses (AR+UV-B) were not identical, and none of them showed a simple linear variation, but displayed additive, synergistic or antagonistic effects depending on the different treatment periods and/or degree of stresses, indicating that plants had different mechanisms of resistance and adaptability under different stresses. The two different breeds of maize had different sensitivity to AR and UV-B treatment at different stages. Yu Nuo 7 was in general more tolerant to stresses than Su YuNuo.