| Heavy metal pollution in soil affects the ecological environment seriously,the tolerance and enrichment ability of plants to heavy metals in soil has become a research focus.In this paper,potted plant of triennial Ardisia japonica was used as materials to study the response of physiological parameters and changes of plant morphology under different concentrations of Pb,Cd and Cr stress in soil,and the tolerance and response mechanism were analyzed,so as to provide guidance for remediation and greening of heavy metal contaminated soil.The main conclusions were as follows:(1)Effects of soil Pb stress on Ardisia japonica:①When the concentration of Pb in soil was 500 mg·kg(-1),,after 60 days of stress,total chlorophyll content,Fv/Fm,qP,increasing extent of light response curve,increasing extent of A-Ci curve,carboxylation efficiency,water content of plant tissues increased,Fo,Fv’/Fm’,ETR and respiration rate decreased,soluble sugar content,soluble protein content and SOD activity showed the phenomenon of initial promotion and late inhibition,MDA content continued to increase,dry weight of plant increased,and growth was promoted.②When the concentration of Pb in soil was 800 mg·kg(-1),after 60 days of stress,increasing extent of A-Ci curve,carboxylation efficiency and water content of plant tissues were lower than those of the control,and the dry weight of shoots decreased,the change trend of other indexes was consistent with 500 mg·kg(-1) treatment group.③When the concentration of Pb in soil were 1200 mg·kg(-1) and 1800 mg·kg(-1),the changes of various indicators were similar,after 60 days of stress,on the basis of 800 mg·kg(-1) treatment group,total chlorophyll content,Fv/Fm,increasing extent of light response curve and qP decreased,Fo increased and plant growth was hindered.The results showed that:Ardisia japonica could tolerate Pb stress of 1800 mg·kg(-1) for 60 days without death.Changes in physiological indicators indicated that:the growth of Ardisia japonica was obviously inhibited when the concentration of Pb in soil was 1200 mg·kg(-1),when the concentration of Pb in soil was 800 mg·kg(-1),the growth of Ardisia japonica.was better than control.Therefore,it was suggested that the area with the concentration of Pb in soil less than 800 mg·kg(-1) should be planted in order to avoid affecting the growth and ornamentation of Ardisia japonica.(2)Effects of soil Cd stress on Ardisia japonica:①When the concentration of Cd in soil was 25 mg·kg(-1),after 60 days of stress,total chlorophyll content,Fv/Fm,Fv’/Fm’,qP,ETR,respiration rate and carboxylation efficiency decreased,Fo increased.increasing extent of light response curve,increasing extent of A-Ci curve,soluble sugar content and water content in plant tissues increased first and then decreased,soluble protein content and SOD activity decreased first and then increased,MDA content continued to increase,plant growth was good,and dry weight of the whole plant increased.②When the concentration of Cd in soil was 50mg·kg(-1),increasing extent of light curve was always lower than the control,the soluble sugar content was higher than the control from the beginning and then decreased,the soluble protein content and SOD activity were lower than the control and then increased,the other indicators were consistent with the change trend of 25 mg·kg(-1) treatment group.③When the concentration of Cd in soil were 100 mg·kg(-1) and 200 mg·kg(-1),the total chlorophyll content,chlorophyll fluorescence parameters,carboxylation efficiency and other indicators were affected more and more significantly.After 60 days of stress,the respiration rate,soluble protein content,SOD activity and MDA content increased to the highest value in each group,and the dry matter accumulation decreased,the ornamental quality decreased.The results showed that:The resistance of Ardisia japonica to Cd stress was strong.When the concentration of Cd in soil was 25 mg·kg(-1),some physiological indexes of Ardisia japonica decreased after 60 days of Cd stress,but when the concentration of Cd in soil reached 200 mg·kg(-1),Ardisia japonica could still respond to the stress by increasing the content of soluble protein and SOD activity after 60 days of stress,and there is no death of Ardisiajaponica under 200 mg·kg(-1) of Cd stress.It had the potential to be used as landscape greening plant in heavy metal Cd polluted areas.(3)Effects of soil Cr stress on Ardisia japonic ① When the concentration of Cr in soil was 150 mg·kg(-1),after 60 days of stress,the total chlorophyll content,Fv/Fm,Fv’/Fm’,qP,ETR,increasing extent of light response curve,increasing extent of A-Ci curve,respiration rate,carboxylation efficiency and water content of plant tissues were lower than those of the control.Fo,soluble sugar content,soluble protein content,SOD activity and MDA content were higher than those of the control,and plant growth was good.②When the concentration of Cr in soil was 300 mg·kg(-1),,after 60 days of stress,on the basis of 150 mg·kg(-1) treatment,the respiration rate was higher than that of the control,the soluble sugar content was lower than that of the control,and the growth of the plant was seriously damaged.③When the concentration of Cr in soil was 450 mg·kg(-1),after 45 days of stress,on the basis of 300 mg kg-1 treatment,the soluble protein content was lower than that of control.After 39 days of stress,some plants died,and 55 days after stress,the whole group died.The results showed that:When the concentration of Cr in soil was 450 mg·kg(-1),Ardisiajaponica could not survive for more than 55 days;when the concentration of Cr in soil was 300 mg·kg(-1),no death occurred,and some indicators still responded to resistance,but the ornamental was effected more obviously;when the concentration of Cr in soil was 150 mg·kg(-1),Ardisiajaponica grew relatively well.Therefore,when Ardisia japonica was used for greening contaminated land with Cr,the area Cr contaminated concentration of soil should not more than 150 mg·kg(-1). |
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