不同Cd水平对小白菜叶片抗氧化酶系统的影响

Effects of Different Cadmium Levels on the Antioxidative Enzymes Activities of Leaf in Brassica chinensis

采用水培的方法,探讨了不同Cd2+水平(0、1、2.5、5、10mg·L-1)对小白菜地上部分超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性、氧自由基产生速率以及丙二醛(MDA)、谷胱甘肽(GSH)和游离脯氨酸含量的影响。结果表明,随着Cd2+浓度的提高,SOD活性呈下降趋势(r=0.94);Cd2+胁迫下小白菜POD、CAT活性分别比对照提高了28.9%～60.8%和5.6%～18.8%;MDA含量在Cd2+浓度为1、2.5、5、10mg·L-1时,分别比对照提高了4.7%、17.9%、43.3%、64.9%;游离脯氨酸含量在Cd2+浓度为1mg·L-1时最低,浓度为5mg·L-1时最高;Cd2+浓度为2.5,5,10mg·L-1时,氧自由基产生速率分别为对照的1.5、1.5、1.1倍;小白菜GSH含量随着Cd2+浓度的增加而增加(r=0.93),说明GSH在缓解小白菜Cd毒害的过程中具有重要意义。

A hydroponic experiment was carried out to study the effects of different cadmium levels （0-10 mg·L^-1） on various enzymatic antioxidants and non-enzymatic antioxidants in Brassica chinensis, including superoxide dismutase （SOD）, peroxidase （POD）, catalase （CAT）, the rate of oxygen free radicals production, and content of malondialdehyde （MDA）, glutathione（GSH） and free proline. The results showed that the activity of SOD presented a negative correlation with Cd concentration in the hydroponic medium, indicating the occurrence of oxidative stress; while the activities of both CAT and POD were higher than that of CK when treated with Cd, increasing by 28.9%-60.8% and 5.6%-18.8%, respectively. High concentration of Cd enhanced the MDA accumulation, and the maximum concentration of MDA was about 64.9% higher than that of CK at the external Cd level of 10 mg·L^-1. When exposed to Cd for 12 days, the concentration of free proline was lowest at 1 mg·L^-1 of Cd and reached a peak at 5 mg·L^-1 of Cd. The production rate of oxygen free radicals was also higher compared with CK, being 1.5, 1.5 and 1.1 times of that in plants grown without Cd at 2.5, 5 and 10 mg·L^-1 of Cd respectively. GSH concentration in the leaves showed a significantly positive correlation with Cd level （r=0.93）, indicating its significant role in detoxifying the toxicity of Cd to Brassica chinensis.