Cu^(2+)胁迫下菹草叶片活性氧水平变化及生理应答

Changes of reactive oxygen species levels induced by Cu^(2+) stress and physiological responses to Cu^(2+) stress in Potamogeton crispus leaves

菹草经不同浓度Cu2+(0、0.01、0.03、0.05、0.07mmol·L-1)处理后,研究其叶片活性氧水平(O·-2和H2O2)及超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、过氧化物酶(POD)活性、可溶性蛋白含量和硫代巴比妥酸反应物(TBARS)含量的变化。结果表明:①随外源Cu2+浓度的增高,菹草叶片Cu2+含量明显增加,Cu2+累积产生了明显的毒害效应,主要表现为可溶性蛋白含量明显减少和TBARS含量逐步增加;②就活性氧水平而言,在0.01mmol·L-1Cu2+胁迫下,H2O2大幅提升,此后在POD和CAT的共同作用下,其含量显著下降。而POD活性仅在0.01mmol·L-1处理后出现短暂上升而后逐渐下降,而CAT活性则表现为逐渐升高的趋势,CAT在清除H2O2过程中发挥着更为明显的作用;O·-2产生速率仅在Cu2+最高处理浓度(0.07mmol·L-1)时出现明显增加。这些指标变化提示,过量的Cu2+将引起菹草叶片氧化损伤,抗氧化酶(SOD、POD和CAT)在抵抗Cu2+胁迫中发挥着重要作用,明显地抑制活性氧(O·-2和H2O2)的累积,尤其是SOD作用更为显著。

ABSTRACT： Potamogeton crispus leaves were subjected to different concentrations of Cu2＋ （0, 0.01, 0.03, 0.05, 0.07 mmol · L-1 ） and levels of reactive oxygen species （O2 ·- and H2O2 ）, activities of superoxide dismutase （SOD）, cat- alase （CAT） and peroxidase （POD）, contents of soluble protein and TBARS were determined. The results indicated that： O Cu2＋ content increased significantly with the increase of exogenous Cu2＋ concentrations. The content of soluble protein decreased obviously and the content of TBARS increased gradually, which resulted from toxicity of excess Cu^2＋ to P. crispus leaves; （2） different reactive oxygen species showed different responses to Cu2＋ stress. Treatment with 0.01 mmol·L^-1 Cu2＋ enhanced H2O2 content temporarily, because of congenerous function of POD and CAT, H2O2 content dropped to a low level at last. POD activity appeared temporary enhancement at 0.01 mmol ·L^-1 Cu2＋ treatment then reduced gradually, whereas CAT activity enhanced gradually with the increase of exogenous Cu2＋ concentrations, which indicated that CAT played more evident role in cleaning H2O2 than POD. The generation rate of O2· -accelerated markedly only at the highest Cu2＋ treatment （0.07 mmol ·L^-1 ）, which resulted from the high activity of SOD. The results of this study indicated that excess Cu2＋ induced oxidative stress, antioxidant enzymes （SOD, POD and CAT） played an important role in protecting P. crispus leaves against oxidative stress, which inhibited the accumulation of reac- tive oxygen species O2· - and H2 O2, especially for SOD.