Effects Of Single And Combined Pollution Of Cd,Pb On The Growth Of Ginkgo Biloba Seedlings And The Content Of Flavonoids In Ginkgo Biloba L.

As a traditional greening tree species in China,Ginkgo biloba L.integrates ornamental,medicinal and economic value.With the economic development and people's expectation of environmental improvement,the soil environment is increasingly polluted by heavy metals such as Cd and Pb.The growth of heavy metal stress and the accumulation of secondary metabolite ginkgo flavonoids were studied.The growth of Ginkgo biloba seedlings under different stress and Cd and Pb was studied by using different concentrations of heavy metals Cd and Pb.The physiology,the content of flavonoids in Ginkgo biloba and the expression of PAL,CHS,CHI and FLS genes in key synthetic pathways of Ginkgo biloba,provide a scientific basis for the selection of urban landscape tree species and the useful substances of secondary metabolites of Ginkgo biloba.The research results are as follows:(1).Single and compound stress of heavy metal Cd,Pb could promote the growth of Ginkgo biloba seedlings at a certain low concentration level,while high concentration could inhibit the growth of Ginkgo biloba seedlings.The growth increment of plant height,specific leaf area and root fresh weight and dry weight of ginkgo biloba seedlings were promoted by single Cd at the concentration below 50mg/kg,while the stress at or above 100mg/kg level showed inhibitory effect on the growth of Ginkgo biloba seedlings.The effects of single Pb on the basal diameter,leaf fresh weight and root dry weight of ginkgo biloba seedlings were also promoted when the concentration of Pb was less than 300mg/kg,and the effect of inhibition was observed at or above 500mg/kg the concentration of Gingko biloba seedlings.The combined stress of Cd50mg/kg and Pb300mg/kg could promote the growth of Ginkgo biloba seedlings,and the growth was gradually inhibited with the increase of complex concentration.(2).The single and compound stress of Cd,Pb resulted in the enhancement of membrane lipid peroxidation and internal osmoregulation,the decrease of total chlorophyll content and the inhibition of root activity in Ginkgo biloba seedlings.The antioxidant defense system showed different response to different concentrations of stress.Low concentration stress could promote the enzyme activity of antioxidant system,but when the stress concentration increased,the enzyme activity was inhibited to some extent.(3).Under single and compound stress of heavy metal Cd,Pb,Cd,Pb was mainly accumulated in the root of Ginkgo biloba,followed by in the leaves of Ginkgo biloba.With the increase of Cd and Pb concentrations,the content of Cd and Pb in roots and leaves increased gradually,and there was a significant dose-increasing effect.Under the combined stress of Cd and Pb,the content of heavy metals in roots and leaves increased with the increase of complex concentration,and the effect of synergistic promotion was obvious.(4).Single Cd stress The total flavonoids,kaempferol and quercetin content of Ginkgo biloba seedlings decreased with the increase of Cd concentration.Under single Pb stress,Pb could promote the total flavonoids of Ginkgo biloba at a concentration of 150mg/kg.The content was 10.2% higher than that of CK.The content of total flavonoids,kaempferol and quercetin were inhibited with the increase of Pb concentration.When combined with stress,the total flavonoids of Ginkgo biloba increased by 3% at Cd25Pb150mg/kg.With the increase of complex concentration,total flavonoids,kaempferol and quercetin were gradually decreased.Isorhamnetin is low in content at each concentration level and has substantially no change.(5).Single Cd treatment can promote the expression of PAL,CHS and CHI,while FLS increases first and then decreases with the increase of Cd concentration.When single Pb stress,PAL gradually decreases with the increase of Pb concentration,CHS,CHI,FLS The expression is expressed as a low concentration to promote high concentration inhibition.Under compound stress,Pb500mg/kg and Pb1000mg/kg combined with different concentrations of Cd,the expression of PAL,CHS,CHI and FLS was significantly inhibited,and the inhibitory effect increased with the increase of complex concentration.