【摘要】 镉(Cd)积累是造成土壤重金属污染的重要因素之一,它是一种对植物生理代谢过程产生诸多影响的环境胁迫因子,光合作用的变化可以直接反映植物对Cd胁迫的适应特性。通过对外来植物南美蟛蜞菊(Wedelia trilobata(L.) Hitchc.)生长过程不同程度的Cd胁迫处理,利用光合气体交换与叶绿素荧光技术,初步观测盆栽土壤中不同质量分数的Cd对南美蟛蜞菊叶片净光合速率、蒸腾速率、水分利用效率、叶绿素质量分数与荧光特征等光合特性的影响。结果显示:①当土壤中Cd质量分数达到5mg·kg-1时,叶片净光合速率Pn明显降低,但蒸腾速率Tr和气孔导度gs降幅较小,水分利用率WUE则没有表现出明显差异;②随着土壤中Cd的增加,叶绿素a质量分数与叶绿素a/b降低,但叶绿素b变化不明显;③Cd质量分数达到2mg·kg-1时,初始荧光Fo与光化效率Fv/Fm变化明显,光系统Ⅱ电子传递速率ETR和量子效率ΦPSⅡ从Cd质量分数为0.5mg·kg-1起有明显变化。由此看出,Cd对叶绿素有一定程度的破坏作用,其中光反应中心对Cd胁迫尤为敏感,叶片光合速率和光能转化效率的下降与此密切相关。更多还原

【Abstract】 Cadmium(Cd) accumulation is an important factor to cause the heavy metal pollution in soil,and Cd-induced environ-mental stress produce many influences on plant physiological metabolism processes.Photosynthetic changes can directly reflect the adaptation to Cd stress in plants.With the treatment of different concentrations Cd to the growth of exotic plant f Wedelia tri-lobata(L.) Hitchc.,and using the technique of photosynthetic gas exchange and chlorophyll fluorescence,the photosynthetic traits such as photosynthetic rate and chlorophyll fluorescence parameters were observed primarily.The results showed that:① Under condition of soil Cd concentrations at 5 mg·kg-1,the net photosynthetic rate(Pn) reduced evidently,while transpiration rate(Tr) and stomatal conductance(gs) decreased a little,and water use efficiency(WUE) did not exhibit distinct difference.② With the increasing of Cd concentration in the soil,chlorophyll a content and chlorophyll a/b ratio decreased in leaves,but chlorophyll b content altered insignificantly.③ Respectively,initial fluorescence(Fo) increased and Photosystem Ⅱ(PSⅡ ) photochemistry efficiency(Fv/Fm) decreased significantly with soil Cd concentration at 2 mg·kg-1.Moreover,PSⅡelectron transport rate(ETR) and quantum yield(ΦPSⅡ) decreased obviously from soil Cd concentration at 0.5 mg·kg-1.These results suggested that Cd caused a certain extent damage to the chlorophyll in leaves,and the photoreaction center was especially sensitive to Cd-induced stress,which were closely correlative with the decreases of the photosynthetic rate and light energy conversion efficiency.更多还原