Pb、Cd和酸胁迫对枫香种子萌发、幼苗生长及体内抗氧化酶活性的影响

为探讨重金属及酸胁迫下枫香种子和幼苗的生理响应,设置不同浓度的Pb、Cd及酸胁迫试验,测定不同胁迫处理下枫香种子萌发、幼苗生长、抗氧化酶等指标。结果表明:Pb、Cd对枫香种子发芽率无显著影响(P0.05),但对幼苗的生长有显著的抑制效应(P0.05);随Pb胁迫浓度的增加,枫香种子超氧化物岐化酶(SOD)活性下降,第10 d过氧化物酶(POD)、及第4、7 d过氧化氢酶(CAT)活性均呈多项式变化,表现为"升高-降低-升高"的趋势;Cd胁迫显著提高枫香种子的SOD和CAT活性,发芽初期(4 d)POD活性受到抑制,但随胁迫时间延长POD活性显著升高;pH4.5、pH5.5对枫香种子的发芽指数、幼苗生长均有促进的作用;随pH值减小,胁迫第7 d的POD活性及第10 d的POD、CAT活性均显著增加。随胁迫时间的增加,在强酸条件下萌发初中期,枫香种子通过增加POD活性清除体内H2O2对细胞的氧化损伤;丙二醛(MDA)含量整体表现出上升趋势,未萌发种子的MDA含量显著高于胁迫处理(P0.05),说明胁迫造成枫香种子膜脂过氧化严重。综上,CAT活性变化是枫香种子响应Pb、Cd和酸胁迫的主要策略,SOD在枫香种子适应Cd胁迫、POD在枫香种子适应Pb和酸胁迫过程中也发挥了一定作用。

Effects of Pb, Cd, and acid stress on seed germination, seedling growth, and antioxidant enzyme activities of Liquidambar formosana

Soil acidification and heavy metal pollution are two major limiting factors of the ecological restoration of ionic-rare abandoned land. Some special morphological and physiological mechanisms may exist in Liquidambar formosana Hance owing to its strong adaptation to ionic-rare abandoned land in Changting, Fujian. A controlled artificial climate experiment chest was applied to explore the response strategy of Liquidambar formosana to Pb, Cd, and pH stress. The stress treatments were conducted in triplicate. Seed germination status, growth of seedlings, and antioxidant enzyme activity were measured. The results showed that there was no significant difference for seed germination(P>0.05), but the growth of seedlings significantly decreased(P<0.05) under Pb and Cd stress. Superoxide dismutase(SOD) activity,peroxidase(POD) activity of the tenth day and catalase(CAT) activity of the fourth and seventh day changed polynomial,showing a trend of decrease after increase,and then rising up again at the second inflexion, The activities of CAT and SOD significantly improved with the increase of Cd concentration. POD activity was inhibited in the early stage of germination(4 d) but significantly increased with enhanced stress in the late stage. The pH levels of 4.5 and 5.5 had a promotion effect on the germination index and growth of seedlings. With the decrease of soil pH, POD activity of the seventh day increased significantly, and the POD and CAT activities of the tenth day improved obviously. With stress time increased, the results indicated that under strong acidic conditions, the activity of POD was increased and the oxidative damage of H₂O₂ to the cells was eliminated in the middle stage of germination. The malonaldehyde(MDA) contents had an increasing trend, with those of the un-germinated seeds significantly(P<0.05) higher than those of the germinated seeds, indicating that the membrane lipid peroxidation got serious. To sum up, CAT activity was the main response strategy of Liquidambar formosana to Pb, Cd, and acid stress. SOD activity played an important role in the adaptation of Liquidambar formosana to Cd stress, as did POD activities for Pb and acid stress.