| Cadmium is one of the most toxic heavy metals threatening human and animal health and the heavy metal with the most serious standard-exceeding point rate.Poplar have become one of the important research object in the phytoremediation of the soil heavy metal pollution due to its characteristics of rapid growth,huge biomass,and so on.The tolerance/accumulation ability of plant to heavy metals should have intraspecific genetic variance in theory,but current researches on the tolerance /accumulation ability of poplar to heavy metals have normally concentrated only on a few clones,which cannot reflect the characteristics of genetic variation within a specific poplar species.Therefore,this study took Populus cathayana as the research object and collected cuttings from 30 individuals within each of four natural distributed populations of Dawei(DW),Maoniugou(MN),Pengta(PT)and Yulin(YL)in northwest Sichuan to conduct the pot experiment with three cadmium treatments,of CK,L(25mg/kg)and H(50mg/kg).The systematic research from population genetics and genetic breeding on the genetic variance of tolerance/ accumulation ability of P.cathayana to cadmium among populations and among individuals within populations was carried out,the results are showed as followings:(1)With the increase of soil cadmium concentration,the growth response of P.cathayana of four populations generally showed an increased promotion or switching from inhibition to promotion.However,the obvious differences of growth response among populations and among individuals within populations were found.Wherein,DW was significantly worse than the other three population,and the change rates of individual growth(total biomass)relative to CK under L and H treatments were between-33.7%~73.4% and-46.3%~116.5%,respectively.(2)With the increase of soil cadmium concentration,cadmium concentration in root increased among three treatments approximate equally,but the cadmium concentration in stem and leaf under L treatment was nearly close to thoses under H treatment,indicating that the tolerant ability of P.cathayana to cadmium mightbe based on the strategy of accumulation aboveground.Significant differences among populations and among individuals were found,and the variation among individuals accounted for more than the variation among populations.Among population it was showed DW <MN,PT and YL,and among individuals the maximum values under L and H treatments were 2.78 and 2.59 times of the minimum values,respectively.(3)With the increase of soil cadmium concentration,cadmium accumulations in organs and in plant totally increased significantly in turn with the trend among organs being leaf > stem > root.Significant differences among populations and individuals were also found,in which the difference among individuals was similar to that of cadmium concentration,and the individual maximum values under L and H treatments were 3.91 and 4.63 times of the individual minimum values,respectively.(4)The bioaccumulation factor(BCF)and the transport coefficient(TF,TF’)of P.cathayana were generally decreased and the tolerance coefficient(Ti)was generally increased with the increase of soil cadmium concentration.Except for TF’,BCF,TF and Ti of DW were significantly lower than those of MN,PT and YL,and the coefficients of variation(CVs)of BCF,TF,TF’ and Ti were between 14.9%~30.3%,14.4%~32.4%,18.3%~46.6% and 11.3%~18.2%,respectively.(5)The average heritabilities of each index of P.cathayana in populations were moderate,which indicated that there was a good potential for the selection and breeding of P.cathayana based on cadmium tolerance/accumulation.(6)The correlation analysis showed that the correlation of various indices of poplar under cadmium treatment would be generally the same.Cadmium concentrations in organs had a significant positive correlation with cadmium accumulations,and BCF,TF,and TF’ were negatively correlated with cadmium concentration and accumulation in root.Cluster analysis showed that poplar individuals could be classified into four types: low accumulation type or antagonistic type,medium accumulation type,high accumulation type and hyperaccumulation type.Most of individuals of DW belong to the type of low accumulation or antagonistic,individuals of YL belong to the type of medium enrichment,and many individuals of MN and PT belong to the type of hyperaccumulation.In conclusion,P.cathayana was of the good tolerance and cadmium accumulation ability to cadmium,which showed the growth promotion even under the treatment with 50mg/kg cadmium in soils other than the growth inhibition.There were a significant genetic variations among populations and among individuals within popualtion in the ability of cadmium accumulation/tolerance,in which the variation among individuals was larger than the variation among populations,and the heritability was generally moderate.Cluster analysis exhibited that some individuals may tolerate cadmium stress by accumulation strategy and some individuals by antagonistic strategy.The results provide scientific basis for selection and breeding of poplar for the remediation of heavy metal pollution in soil. |
