Effects of Cu2O nanoparticles on the kinetic characteristics of rapid chlorophyll fluorescence induction and related genes in wheat seedlings
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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