Effects of photosynthetic characteristics and chlorophyll fluorescence in Verbena bonariensis under single and combined Cu and Ni stress
[Objective]To reveal the adaptability of Verbena bonariensis under single and combined Cu and Ni stress.[Method]Verbena bonariensis was cultured in river sand with nutrient solution,and leaf photosynthetic char-acteristics and chlorophyll fluorescence indexes were determined by setting different copper(or Cu)stress concentra-tions of 0,300,600,900,and 1 500 mg/kg,different nickel(or Ni)stress concentrations of 0,300,600,900,and 1 500 mg/kg,and different combined Cu and Ni stress concentrations of 0,300,600,900,and 1 500 mg/kg,respec-tively.[Result]With increasing single and combined Cu and Ni stress,plant height,leaf length,leaf width,leaf area,root activity,chlorophyll,and carotenoid contents increased first and then decreased and reached the maximum value at Cu.300,Ni.300,and Cu+Ni.300,respectively.Transpiration rate,net photosynthetic rate,stomatal conductance,water use efficiency,and stomatal limitation value were decreased and reached the minimum value at Cu.1500,Ni.1500,and Cu+Ni.1500,respectively,while intercellular carbon dioxide concentration increased and reached the maximum value at Cu.1500,Ni.1500,and Cu+Ni.1500,respectively,which indicated that the non-stomatal factor restricted photosynthesis.Except for the increase of the non-photochemical quenching coefficient,actual photochemi-cal efficiency,maximum photochemical efficiency,electron transport rate,photochemical quenching coefficient,and photochemical quantum yield were decreased.The contents of Cu2+and Ni2+in roots,stems,and leaves increased sig-nificantly and the order was roots>leaves>stems.Cu2+content in roots was 2 461.27 mg/kg at Cu.1500,and Ni2+content in roots was 1 506.21 mg/kg at Ni.1500,and Cu2+and Ni2+contents in roots were 2 080.14 mg/kg and 1 469.45 mg/kg at Cu+Ni.1500,respectively.[Conclusion]Verbena bonariensis has strong tolerance under single and combined Cu and Ni stress,and the contents of Cu2+and Ni2+are mostly in the roots.
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