类芦根系抗氧化酶和植物螯合肽对Cd、Pb胁迫的应答

摘要

类芦（Neyraudiarey naudiana）是中国南方金属矿区最为常见的耐性植物，且能大量富集重金属，是修复重金属污染的潜能植物。为研究其对重金属胁迫的应答机制，采用营养液培养的方法研究了不同浓度（0、25、50、100μmol·L-1）Cd、Pb处理24 h后，类芦根系氧化损伤、抗氧化酶活性和非蛋白巯基化合物含量的变化。结果表明，在Cd、Pb胁迫下，类芦根系H2O2和O2•-含量显著增加，且伴随有MDA含量的升高，当Cd、Pb浓度为100μmol·L-1时，MDA分别达到6.72和16.12 nmol·g-1，发生膜脂质过氧化，造成植物氧化损伤。Pb胁迫下，SOD，POD活性随着处理浓度的增加呈现先上升后下降的趋势；Cd胁迫下SOD活性变化趋势与Pb胁迫的相似，而POD活性呈下降趋势。根系非蛋白巯基化合物含量检测显示，Cd、Pb处理下，GSH和PCs均呈先增加后下降的趋势。综合分析得出，类芦根系对不同重金属的不同浓度胁迫响应不一，其能通过调节抗氧化酶活性和植物螯合肽等的合成水平，降低重金属的毒性及其对植物的伤害，从而维持自身的稳态。%Neyraudia reynaudiana is one of the most common heavy-metal tolerant plants surrounding mines. Because N. reynaudiana can accumulate large amounts of heavy metals, it could be an effective plant for phytoremediation. In order to study its response to heavy metal stress, a solution culture experiment was carried out at different lead (Pb) and cadmium (Cd) concentrations (0, 25, 50, and 100 μmol·L-1). After 24 hours, oxidative damage, antioxidant enzyme activity, and non-protein thiol compound content or root tissue were assessed. Under Cd and Pb stress, increases in H2O2 and O2•- content were accompanied by malondialdehyde (MDA) content increases. At Pb and Cd concentrations of 100μmol·L-1, the MDA contents respectively reached 6.72 and 16.12 nmol·g-1, and both lipid peroxidation and oxidative damage had increased. Additionally, enzymatic function was effected, with superoxide dismutase (SOD) and peroxidase (POD) activity initially increasing with metal concentration and then declining under higher Pb stress. SOD activity under Cd stress was similar to that under Pb stress, but POD activity was lower. The non-protein thiol content of roots showed that glutathione and phytochelatins initially increased and then decreased with Cd and Pb concentrations. Comprehensive analysis thus revealed that these two heavy metals at different concentrations have different effects on N. reynaudiana root tissue. Overall, N. reynaudiana can adjust its antioxidant enzyme activity and non-protein thiol synthesis levels in order to reduce heavy metal toxicity and damage.