Metal nanoparticles could be accumulated in soils,which threatens the ecological stability of crops.In-vestigating the effects of cuprous oxide nanoparticles(Cu2 O-NPs)on photosystem Ⅱ(PS Ⅱ)of wheat seedling leaves holds considerable importance in comprehending the implications of Cu2 O-NPs on crop photosynthesis.Fol-lowing the hydroponic method,we investigated the effects of 0,10,50,100,and 200 mg·L-1 Cu2O-NPs on chlo-rophyll fluorescence induction kinetics and photosynthetic-related genes in wheat seedlings of"Zhoumai 18".The results showed that,with the increases of Cu2 O-NPs concentrations,chlorophyll contents in wheat leaves decreased,and the standardization of the OJIP curve showed a clearly K-phase(△K＞0).Cu2O-NPs stress increased the parameters of active PS Ⅱ reaction centers,including the absorption flux per active RC(ABS/RC),the trap-ping flux per active RC(TRo/RC),the electron transport flux per active RC(ETo/RC),and the dissipation flux per active RC(DIo/RC).Cu2 O-NPs stress decreased the parameters of PS Ⅱ energy distribution ratio including the maximum quantum yield of PS Ⅱ(ψPo),the quantum yield of electron transport from QA(ψEo),and the probabil-ity that a trapped exciton moved an electron further than QA(Ψo),while increased the quantum ratio for heat dis-sipation(ψDo).Moreover,there was a decrease in photosynthetic quantum yield Y(Ⅱ),photochemical quenching coefficient(qp),net photosynthetic rate(Pn),stomatal conductance(gs),intercellular CO2 concentration(Ci),and transpiration rate(Tr)of leaves with the increases of Cu2O-NPs concentration.Under Cu2O-NPs stress,the expression levels of genes which included PS Ⅱ genes(PsbD,PsbP,Lhcb1),Rubisco large subunit genes(RbcL),cytochrome b6/f complex genes(PetD,Rieske),and ATP synthase genes(AtpA,AtpB,AtpE,AtpI)were downregulated.These results indicated that Cu2O-NPs stress altered the activity and structure of PS Ⅱ in wheat seedlings,affected the activity of PS Ⅱ reaction centers,performance parameters of PS Ⅱ donor and acceptor sides.PS Ⅱ related genes were downregulated and exhibited significant concentration effects.
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