Pb^(2+)对桐花树幼苗抗氧化酶活性及脂质过氧化的影响

Effects of Lead Stress on Activities of Antioxidant Enzymes and Lipid Peroxidation in Aegiceras Corniculatum Seedling

通过土培实验,研究铅胁迫对桐花树(Aegiceras Corniculatum)幼苗膜脂过氧化及抗氧化保护酶的影响.结果表明,桐花树幼苗受铅胁迫源于时间和浓度的双重影响.Pb2+(0 mg/kg、500 mg/kg、1 000 mg/kg1、500 mg/kg2、000 mg/kg、3 000 mg/kg)胁迫30 d后超氧负离子(O2-)、丙二醛(MDA)的含量,过氧化物酶(POD)、过氧化氢酶(CAT)活性总体上都较铅离子胁迫15 d更高.随着Pb2+浓度(0~3 000 mg/kg)的升高,O2-、MDA的含量均呈上升趋势,表明Pb2+胁迫浓度越高,使桐花树幼苗膜脂过氧化而引起的膜伤害越大;在Pb2+胁迫浓度不超过2 000 mg/kg时,POD、CAT活性高于对照,且随铅浓度的升高而上升,高峰值在2 000 mg/kg处,体现其作为抗氧化保护酶对铅胁迫起到防御作用,亦是植物体对Pb2+的一种保护性的应激反应,但在高浓度(3 000 mg/kg)胁迫下,POD、CAT活性却下降低于对照,表明高浓度Pb2+胁迫已经伤害桐花树幼苗POD、CAT酶的防御保护能力,3 000 mg/kg铅离子浓度超过了桐花树幼苗正常生理过程所能承受的阈限值.

The effects of lead stress on the activities of antioxidant enzymes and lipid peroxidation in Aegiceras Corniculatum seedling grown in the soil treated with various concentrations of Pb^2＋ ranging from 0 to 3 000 mg/kg were studied. The results showed that the contents of the superoxide anion （O2）, malondialdehyde （MDA）, eatalase （ CAT）, peroxidase （POD） in seedling growing in the treated soil of 30 days are greater changes than those of 15 days caused by lead stress. The activities of antioxidant enzymes and lipid peroxidation in the seedling were affected by both their exposing time and increasing Pb concentrations in the soils. In the groups below 2 000 mg/kg Pb concentrations, the activities of CAT and POD in the seedling were higher than the control group, while they were dropped significantly when the Pb concentration up to 3 000 mg/kg of soil that the seedling growed in. It suggested that the increasing activity of antioxidant enzyme in seedling is not only playing a defensive role but also a kind of physiological stimulated response to the lead stress. Moreover, the stress of high Pb concentration has damaged the resistant ability of the seedling and the accepted tolerance of Aegiceras Corniculatum seedling to maintain the normally physiological functions have exceeded when they were grown in the soil with 3000mg/kg Pb concentration.