In order to explore the mitigatory mechanism of rare earths on the midday depression of photosynthesis,this study used fast-phase chlorophyll fluorescence technology combined with an antioxidant enzyme system to analyze the effects of lanthanum and cerium on the photosystem Ⅱ(PSⅡ)function of Pseu-dostellaria heterophylla leaves at noon.The results show that the maximum photochemical efficiency(Fv/Fm)and the photosynthetic performance index(PIABS)of P.heterophylla leaves during the photosynthetic noon-break are only 0.73 and 0.86,respectively.The leaves of P.heterophylla show obvious photo-inhibition.The application of two rare earth fertilizers promotes the light energy absorption,capture,conversion,and electron transfer efficiencies of PSⅡ in the P.heterophylla leaves and alleviates the photoinhibition caused by excess excitation energy.Additionally,the effect of lanthanum is better than that of cerium.In the fertilization groups,P.heterophylla leaves show higher PSⅡ photochemical activity.Fertilization protects the oxygen-evolving complex(OEC)activity of P.heterophylla,thus reducing oxidative damage to the chloroplasts and preventing the dissociation of the thylakoids to maintain the normal physiological functioning of PSⅡ,thereby reducing the degree of photoinhibition.Additionally,fertilization increases the electron transfer ability from QA to QB on the PSⅡ electron receptor side of P.heterophylla.Correlation analysis shows that the fluorescence parameters VL,VK,and Vj are significantly negatively correlated with antioxidant enzyme activity and are significantly positively correlated with malondialdehyde content,relative electric conductivity and reactive oxygen species(ROS),which further indicates that rare earths can enhance the ROS scavenging system in plants and reduce the degree of membrane lipid peroxidation and plasma membrane damage,thereby maintaining the structure and function of the OEC on the donor side of PSⅡ,increasing the electron receptor pool,and contributing to the defense against photoinhibition.

Yingli Ma;Tao Wang;Yinfeng Xie;Qian Lv;Lingling Qiu

Co-Innovation Center for Sustainable Forestry in Southern China,College of Biology and the Environment,Nanjing Forestry University,Nanjing 210037,China;Jiangsu Key Laboratory for the Research and Utilization of Plant Resources,Institute of Botany,Jiangsu Province and Chinese Academy of Sciences(Nanjing Botanical Garden Mem.Sun Yat-Sen),Nanjing 210014,China

稀土学报（英文版）

[1]Yingli Ma;Tao Wang;Yinfeng Xie;Qian Lv;Lingling Qiu-.Alleviatory effect of rare earth micro-fertilizer on photosystem Ⅱ(PSⅡ)photoinhibition in Pseudostellaria heterophylla leaves at photosynthetic midday depression)[J].稀土学报（英文版）,2022(07):1156-1164

Alleviatory,mitigatory,Pseu,dostellaria,thylakoids

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