摘要:重金属锰严重抑制植物的光合作用，影响Mn污染地区植被恢复。为给Mn污染地区植被恢复提供合适的树种，以木本植物苦楝为研究对象，分别将0、10 g和30 g的MnCl₂（CK、L1和L2）溶于纯水中配成溶液掺入盆栽土壤，通过快速叶绿素荧光诱导动力学曲线、820 nm光吸收曲线以及光合气体交换参数测定技术，研究重金属Mn对苦楝叶片光系统I（PSI）、光系统Ⅱ（PSⅡ）性能及其协调性的影响。结果表明，Mn胁迫下，苦楝叶片PSⅡ性能指数（PI_ABS）表现为L2 < L1 < CK，且差异性显著（P < 0.05）；K点（W_k）和J点（V_j）均显著大于CK；电子从Q_A^-传递到PSⅠ受体侧的效率（Ψ_（Ro））和捕获的激子将电子传递到电子链中Q_A下游Q_B等电子受体的概率（Ψ_（Eo））随着时间的推移呈现出先上升后下降的趋势；PSI性能（ΔI/I₀）显著低于CK（P < 0.05），PSⅠ与PSⅡ的协调性（φ_{（PSI/PSⅡ）}）在L2水平下差异性显著（P < 0.05）；净光合速率（Pn）、气孔限制值（Ls）和RuBP羧化效率均降低，胞间CO₂浓度（Ci）增高。以上结果表明重金属Mn显著影响了苦楝叶片PSⅡ和PSI性能，使苦楝光合能力下降。



Abstract:Environmental pollution by heavy metals is becoming a serious problem globally. Excess Manganese (Mn) can inhibit the photosynthetic process, which consequently results in a reduction of phytoremediation of soils polluted by heavy metals. In this study, Melia azedarach which distributed widely in south China was employed as experimental material. MnCl₂ (analytically pure) (0, 10 and 30 g) were mixed with pure water first and the mixture solution was divided into 10 equal parts to add to the pots every day, respectively. They were designated as CK, L1, L2, respectively. The toxicity of Mn on photosystems behavior in leaves of Melia azedarach was investigated using in vivo chlorophyll fluorescence transients and light absorbance at 820 nm. The results showed that the excessive Mn levels induced the significant difference of the performance index (PI_ABS). The relative variable fluorescence intensity at the K-step (W_k) and relative variable fluorescence at the J-step (V_j) in Mn-treated leaves significantly higher than that of the CK. The probability of an electron moving from Q_A^- to reduce end electron acceptors at the PSⅠ acceptor (Ψ_(Ro))and probability that a trapped exciton moved an electron into the electron transport chain beyond Q_A (Ψ_(Eo)) showed an initial increase and then decrease trend. The PSI performance (ΔI/I₀) and the coordination between PSⅡ and PSⅠ (φ_(PSI/PSⅡ)) decreased in Mn-treated leaves. Also, excessive Mn significantly decreased the net photosynthetic rate and RuBP carboxylation efficiency, but increased intercellular CO₂ concentration. The results indicated that excessive Mn impaired the performances of photosystems (PSI and PSⅡ), which caused the decrease of the net photosynthetic rate and the rate of CO₂ assimilation.





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