The Research On Physiological Response Of Ardisia Japonica Under Cr,Cd And Pb Combined Stress

Ardisia japonica(Thunb.)Bl.is a kind of excellent ornamental shrubs and is widely used in gardens.In order to apply A.japonica to the ecological remediation of heavy metal contaminated soil,3-year-old A.japonica was used as experimental material.The effects of different concentration levels of chromium(Cr),cadmium(Cd)and plumbum(Pb)combined stress on its physiological characteristics,and the corresponding tolerance of A.japonica were studied.Correlation analysis and principal component analysis were also used for its comprehensive evaluation.The main results were as follows:(1)A.japonica grew well under the stress of Cr<150 mg·kg-1 and Cr<100 mg·kg-1.Under low concentration Cr-Cd(150+100 mg·kg-1)and Cr-Cd(450+100 mg·kg-1)combined stress,the growth of plant height was promoted.Although plants resist stress through cell osmotic regulation under medium concentration Cr-Cd(3 00+200 mg·kg-1)combined stress,plant cells are still damaged.Under Cr-Cd(150+500 mg·kg-1)combined stress and high concentration Cr-Cd(450+500 mg·kg-1)combined stress,the plant height and dry matter accumulation of A.japonica was obviously inhibited,the metabolic function of the plant was disordered,and the cell damage was serious.(2)The photosynthesis of A.japonica under Cr<300 mg·kg-1 and Pb<2000 mg·kg-1 was affected,but the normal physiological metabolism was maintained.At low concentration Cr-Pb(150+800 mg·kg-1),the growth of A.japonica under combined stress was better,the growth of plant height was promoted,and the photosynthesis of plants was enhanced.Under medium concentration Cr-Pb(300+2000 mg·kg-1)combined stress,the soluble sugar content and SOD enzyme activity increased to resist stress.With the increase of stress concentration,plant growth slowed down and dry matter accumulation was inhibited,malondialdehyde(MDA)content increased significantly,and plant cells were damaged greatly.A.japonica still maintained good light energy capture ability under Cr-Pb(150+3000 mg·kg-1)combined stress.The growth,photosynthesis and physiological metabolism of A.japonica were significantly inhibited under high concentration Cr-Pb(450+3000 mg·kg-1)and Cr-Pb(450+800 mg·kg-1)combined stress.(3)A.japonica showed strong tolerance and high physiological metabolism under Cd<500 mg·kg-1 and Pb<800 mg·kg-1 stress.Low concentration Cd-Pb(100+800 mg·kg-1)combined stress promoted the growth of A.japonica.Under Cd-Pb(500+800 mg·kg-1)combined stress,plants resisted stress through cell osmotic regulation and maintained normal growth.During medium concentration Cd-Pb(200+2000 mg·kg-1)combined stress,the indexes were affected by stress and the symptoms of plant injury were obvious.Under Cd-Pb(100+3000 mg·kg-1)combined stress and high concentration Cd-Pb(500+3000 mg·kg-1)combined stress,the center of light reaction was destroyed,and the growth of plants was obviously inhibited.Under high concentration Cd-Pb combined stress,plant individual death occurred after 30 days。。(4)A.japonica showed strong tolerance under the stress of Cr<150 mg·kg-1,Cd<100 mg·kg-1 and Pb<800 mg·kg-1.A.japonica showed strong tolerance and maintained normal growth and physiological activity under low concentration Cr-Cd-Pb(150+100+800 mg·kg-1)combined stress.As the stress concentration increased,the photosynthesis of A.japonica under medium concentration Cr-Cd-Pb(300+200+2000 mg·kg-1)combined stress was inhibited,and the self-regulation function of plant cells was damaged,which was not conducive to cell growth and metabolism.High concentration Cr-Cd-Pb(450+500+3000 mg·kg-1)combined stress caused serious damage to A.japonica,and all the indexes reached its peak,and plant function were inhibited to varying degrees.(5)The plant height growth,plant tissue water content,Fo,Fv/Fm,ETR,total chlorophyll,carotenoid,MDA,soluble sugar,soluble protein are the identification indexes that can best reflect the physiological response of A.japonica to four groups of heavy metal combined stress.The results of principal component comprehensive score ranked the resistance of A.japonica under these four heavy metal combined stress environments as follows:Cd-Pb combined stress>Cr-Cd combined stress>Cr-Pb combined stress>Cr-Cd-Pb combined stress.