Cd^(2+)Pb^(2+)Hg^(2+)Ni^(2+)胁迫对大麦抗氧化酶活性的影响

Effects of Antioxidant Enzymes Activities in Hordeum Vulgare Seedling Under Cd^(2+),Pb^(2+),Hg^(2+),Ni^(2+)Stresses

采用室内培养法,研究了不同浓度(1～100m g·L-1)C d2+、Pb2+、H g2+、N i2+对大麦幼苗根、叶内超氧化物岐化酶(SO D)、过氧化物酶(PO D)和过氧化氢酶(C A T)活性的影响。结果表明,不同重金属离子对SO D、PO D、C A T活性的影响存在差异,表现为激活效应或抑制效应。N i2+、Pb2+处理对大麦幼苗体内SO D、C A T具有激活效应,随着N i2+、Pb2+浓度增加和处理时间延长,根、叶中的SO D、C A T活性由低到高逐渐增大,PO D活性则表现为先升后降。C d2+胁迫对SO D、PO D存在低浓度下的激活效应和高浓度下的抑制效应,对C A T则表现为在所有浓度范围内的持续抑制效应。在1～100m g·L-1浓度范围内,H g2+对SO D、PO D、C A T活性均有不同程度的抑制效应。3种抗氧化酶对H g2+、C d2+的防御作用弱于N i2+、Pb2+,根的防御作用弱于叶。

Trace heavy metal ions of Cd2+, Pb2+, Hg2+, and Ni2+may bepresent in soil as contaminants due to industrial activities. A wide array of toxic effects have been documented in plants including genotoxicity, inhabiting seed germination inhibition, retarding root growth, decreasing mitotic index in root cells, inducing chromosomal aberrations, forming micronucleus, and altering nucleolar structure. This study examined the individual effects of these four metal ions on enzymatic activities of superoxide (SOD), peroxidase (POD) and catelase (CAT) in Hordeum vulgare. The seedlings were exposed to each of the metal ions at the concentrations from 1 to 100 mg·L-1 for 4 to 6 days. The followingenzyme kinetic analysis showed either enhanced or inhibited catalytic activities depending on ion species and enzymes used. Pb2+and Ni2+showed enhancing effects on SOD and CAT, whose activities gradually increased along with the increase in metal concentrations and exposure duration; while POD's activity increased at and but later decreased. In contrast, Cd2+was found enhancing POD and SOD activities at low concentrations but inhibiting them at higher concentrations, whereas Cd2+also consistently inhibited CAT at all the concentrations used in this study. Such steady inhibiting effects were also observed in Hg2+to SOD, POD and CAT. A further observation about these antioxidant enzymes of SOD, POD and CAT demonstrated that they are more resistant to Cd2+and Hg2+in leaves than in roots.