模拟酸雨对水稻叶片抗氧化系统影响的时间效应

Time effect of the simulated acid rain on the antioxidant system in growing rice leaves

采取有效措施减轻酸雨对植物的伤害必须建立在明晰植物对酸雨适应机制的基础上。为探究植物的抗氧化系统及质膜上重要功能蛋白对酸雨胁迫的适应机制,采用模拟试验方法,以pH=7.0为对照(CK),分析pH=4.0和2.5酸雨对水稻叶片内丙二醛(MDA)、过氧化氢(H_2O_2)、超氧化物自由基(O-2·)含量及抗氧化系统(超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、抗坏血酸(ASA))和质膜H+-ATPsae活性影响的时间效应。结果表明,与对照(CK)相比,pH=4.0、2.5酸雨在胁迫1~5 d时引起水稻叶片MDA、H_2O_2、O-2·含量,SOD、CAT活性,ASA质量比和质膜H+-ATPsae活性上升,仅pH=4.0组SOD活性在第5 d出现峰值,其他指标出现"时滞";在胁迫解除后,pH=4.0组各指标在第6~10 d逐渐恢复至CK水平,而pH=2.5组各指标(除质膜H+-ATPase活性低于CK外)仍显著高于CK。这表明在pH=4.0酸雨胁迫下水稻幼苗叶片中SOD和CAT活性与ASA质量比上升有效降低了H_2O_2和O-2·积累、MDA含量、质膜过氧化程度,因而,质膜H+-ATPsae活性恢复至CK并保持稳定;pH=2.5酸雨引起H_2O_2、O-2·过量积累,不仅超出抗氧化酶的清除能力且致使酶钝化,导致MDA含量持续增加,氧化伤害加剧,造成质膜上功能蛋白H+-ATPase活性受抑,其调节胞内pH值功能受阻。水稻抗氧化系统对酸雨胁迫的响应呈明显时间效应,且响应的敏感性从强到弱依次为SOD、CAT、ASA。水稻抗氧化系统恢复程度与恢复进程的快慢受胁迫强度制约。

The paper is to make an exploration of the dynamic effects of the acid rain on the accumulation of the reactive oxygen species（ H2O2,O-2·） in the antioxidant system and plasma membrane H＋-ATPsae activity in the rice leaves during the stress and recovery periods,so as to identify and determine the adaptation mechanism of the rice plants to acid rain stress and find effective ways to reduce the damage on the rice plants caused by the acid rain coerce. The results of our study show that,as compared with the control sample（ pH 7. 0）,during five days,the acid rain at pH 4. 0 and 2. 5 may also lead to the increase of Malondialdehyde（ MDA）, H2O2, O-2· content, Superoxide Dismutase（ SOD）,Catalase（ CAT） activity,Ascorbic Acid（ ASA） content and plasma membrane H＋-ATPsae activity in rice leaves. The peak of the curve SOD activity in leaves treated with acid rain at pH 4. 0 appeared on the fifth day. Other indicators happened＂delay＂. When the stress is relieved,all the indices in the leaves treated with acid rain at pH 4. 0 would begin to decrease bit by bit to the control level from the 6th days to the 10 th days. For the group treated with acid rain at pH 2. 5,all the indices may still remain significantly higher than those of the control group except that the plasma membrane H＋-ATPase would be made lower than that of the control level. The above results indicate that the increasing activities of CAT and SOD and the content of ASA in the rice leaves treated with the acid rain pH 4. 0 is in a position to reduce the accumulation of H2O2 and O-2·,and the membrane peroxidation,and then the activity of the plasma membrane H＋-ATPsae can go on stay at the level of the control. On the contrary,the acid rain at pH 2. 5 is likely to lead to the excessive accumulation of H2O2 and O-2·,till the degree goes beyond the scavenging capacity of antioxidant enzymes for the inhibitive function of the antioxidant enzymes. And,that is why the content of MDA in the plant leaves may continue to increase,which may lead to the increase of the oxidative damage,resulting in the decline of H＋-ATPase activity in the plasma membrane and the blockage of the regulation of the intracellular pH function. In the given experiment,the response of the antioxidant system in the rice seedlings to the acid rain stress show that SOD turns to be most sensitive,which is followed by CAT,and ASA. Therefore,the recovery and the recovery process of the antioxidant system in the growing rice prove to be dependable on the intensity of the acid rain in a great sense.