The physiological responses of P. Fortunei seedling roots to Pb stress under natural light and 50% natural light treatments were investigated. Results showed that production rate of superoxide anion, hydrogen peroxide and MDA contents consistently increased with the increase of added Pb. Compared to natural light treatment, their increasing trends were less sharper under 50% natural light treatment. Under natural light treatment,the activities of SOD,CAT and APX increased firstly and then decreased with the increase of added Pb,while the activities of POD consistently increased. At 50% natural light treatment, all the antioxidant enzyme activities consistently increased with the increase of added Pb. The activities of SOD and POD under 50% natural light treatment were higher than those under natural light treatment. Results suggested that the decrease of light irradiance relieved the oxidative damage of Pb stress to the roots of P. Fortunei.%分析全光照和50％光照条件下,不同浓度Pb对白花泡桐根生理特性的影响,以研究白花泡桐根对Pb胁迫的生理响应机制.结果显示:超氧阴离子产生速率、过氧化氢和丙二醛含量均随Pb浓度增加而上升,而且5o％光照条件下上升趋势要低于全光照条件.全光照条件下,SOD、CAT和APX活性随Pb浓度增加呈现先上升再下降的趋势,而POD活性则呈现持续上升趋势.50％光照条件下,SOD、POD、CAT和APX活性均呈现持续增加的趋势,SOD和POD活性均低于全光照条件.脯氨酸含量均随Pb浓度增加而增加,而且在50％光照条件下含量相对较低.这表明光照强度下降减弱了Pb胁迫对白花泡桐根的氧化损害.
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