急性镉胁迫时雨久花叶片抗氧化酶活性与光合荧光参数的变化

Variations in Antioxidant Enzyme Activities,Photosynthesis,and Fluorescence Parameters in Acute Cd-treated Monochoria korsakowii Leaves

为研究重金属急性胁迫时水生植物叶片的生理代谢活动变化,以雨久花(Monochoria korsakowii)叶片为研究材料,采用液培法,研究不同浓度Cd^(2+)急性胁迫时,叶片抗氧化酶活性、叶绿素质量分数、光合气体交换参数及叶绿素a荧光特性的变化规律。结果表明:经0.12~0.72 mmol/L Cd^(2+)处理48 h时,雨久花叶片叶绿素质量分数无明显变化,净光合速率(P_(n))、胞间CO_(2)摩尔分数(C_(i))、气孔导度(G_(s))和蒸腾速率(E)显著下降;0.12~0.48 mmol/L Cd^(2+)处理48 h,叶片过氧化氢酶(CAT)、谷胱甘肽还原酶(GR)及愈创木酚过氧化物酶(GPX)活性显著上升。当Cd^(2+)处理时间延长至96 h时,雨久花叶片叶绿素质量分数、净光合速率、气孔导度及蒸腾速率下降幅度加大,超氧化物歧化酶和谷胱甘肽还原酶活性增加。叶绿素荧光参数结果分析表明,急性Cd^(2+)胁迫导致雨久花叶片光系统Ⅱ(PSⅡ)结构被破坏,从而导致光化学效率降低;同时,与最大光化学效率(F_(v)/F_(m))相比,性能指数(PI Inst和PI abs)能够更加准确地表征急性Cd^(2+)胁迫对雨久花叶片光系统Ⅱ反应中心活性的变化。综上,雨久花叶片光合作用对急性Cd^(2+)胁迫敏感,可作为该植物预警水体突发性镉污染的一种候选指标。

To identify the variations in physiologically metabolic activities in leaves of aquatic plants,a hydroulic experiment was employed to investigate the variations in antioxidant enzyme activities,chlorophyll content,photosynthetic gas exchange parameters,and chlorophyll a fluroscence characteristics in leaves of Monochoria korsakowii with various contents of Cd^(2+)acute exposure.With 0-0.72 mmol/L Cd^(2+)acute exposure,chlorophyll content represented no significant variations,while obvious reduction in net photosynthetic rate(P_(n)),intercellular CO_(2)content(C_(i)),stomatal conductance(G_(s)),and transpiration rate(E)were observed in the plant leaves;and the 0.12-0.48 mmol/L Cd^(2+)exposure for 48 h treatment increased catalase,glutathione reductase(GR),and guaiacol peroxidase(GPX)activities.With the exposure duration prolonged to 96 h,the declined degree of chlorophyll content,P_(n),C_(i),G_(s),and E was intensified,and superoxide dismutase and GR activities in the plant leaves markedly increased.Analysis of chlorophyll a fluorescence parameters indicated the acute Cd^(2+)exposure treatment damaged photosystemⅡ(PSⅡ)in the plant leaves,thus leading to a reduction in photochemical efficiency.Simultaneously,performance index(PI Inst and PI abs)can accurately represent the damage degree to PSⅡreaction center in the leaves induced by the acute Cd^(2+)exposure in comparison to the maximum photochemical efficiency(F_(v)/F_(m)).Generally,the plant photosynthesis was sensitive to the acute Cd^(2+)exposure,and it can be as a candidate indicator of the plant for the early warning of transient Cd^(2+)contamination in water.