砷胁迫对不同砷富集能力植物叶片抗氧化酶活性的影响

采用室内水培试验方法，研究了砷胁迫（0～50mgAs·L^-1）对砷超富集植物大叶井口边草（Pteris cretica vat．nervosa）和非砷超富集植物剑叶凤尾蕨（Pteris ensiformis）叶片的过氧化氢酶（CAT）、过氧化物酶（POD）、超氧化物歧化酶（SOD）、抗坏血酸过氧化物酶（APX）活性以及丙二醛（MDA）含量和自由基0i·产生速率的影响，并研究了25mgAs·L^-处理下上述6种指标的时间动态。结果表明，随着砷浓度升高，除APX外，剑叶凤尾蕨叶片的CAT、POD和SOD活性受到很大抑制，而大叶井口边草叶片这3种酶的活性能够维持，特别是POD活性显著增加；大叶井口边草叶片的MDA含量降低，剑叶凤尾蕨则升高；剑叶凤尾蕨叶片中的O2^-·产生速率比大叶井口边草增加显著。从时间动态看，随处理时间的延长，大叶井口边草叶片中的CAT和APX活性先降低再升高，POD活性显著增加，SOD活性变化不显著；剑叶凤尾蕨叶片的POD和SOD活性显著降低，APX活性无显著变化，CAT活性则先降低后升高；两种供试植物叶片的MDA含量第6d时均出现明显下降，但大叶井口边草叶片中O2^-·的产生速率在第6d则显著增加，而后降至实验初始时的水平。总起来看，砷超富集植物大叶井口边草比非砷超富集植物剑叶凤尾蕨具有更强的抗氧化能力，并且POD在其抗氧化体系中起关键作用。

Effects of Arsenic Stress on Activities of Antioxidant Enzymes in the Fronds of Plants with Different Abilities to Accumulate Arsenic

The effects of arsenic （ As ） stress （0, 5, 25, 50 mgAs·L^-1 ） on activities of catalase （CAT）, peroxidase （POD）, superoxide dismulase （SOD） and aseorbate peroxidase （APX） as well as malondialdehyde （MDA） content and production rate of free radical O2^-· in the fronds of As hyperaccumulator（Pteris eretica var. nervosa） and non-hyperaccumulator（Pteris ensiformis ） were evaluated by hydroponic experiments. In addition, the variatiolls of these six indexes along with time under 25mgAs·L^-1 stress were also studied. Results showed that increased inhibition of CAT, POD and SOD activities were observed in the fronds ofP. ensiformis with increasing As concentrations except for APX. However for P. ensiformis, the activities of CAT, POD and SOD were maintained, and POD activity was enhanced under the stress of As. MDA contents in the fronds of P. cretiea var. nervosa were depressed by As, but P. ensiformis showed the opposite trend. The production rate of free radical O2^-· in the fronds ofP. ensiformis increased more significantly compared with P. cretica var. nervosa in the presence of As. For P. eretiea var. nervosa, CAT and APX activities decreased followed by an increase with extended time, POD activity increased significantly, but no significant change in SOD activity was observed with time. In the ease ofP. ensiformis, the activities of POD and SOD decreased signifieantly, CAT activity deereased and then increased, while APX activity did not show any significant change along with time. MDA contents in both plants decreased significantly starting from the sixth day. O2^- · production rate in the fronds of P. eretiea var. nervosa increased significantly in the sixth day, then decreased to the initial level with extended time. These findings indicate that the antioxidative ability of P. eretiea var. nervosa is superior to that of P. ensiformis under As stress, and POD plays an important role in the antioxidative system.