Tolerance And Remediation Potential Of Three Invasive Plants To Soil Heavy Metal Pollution Of Cd And Pb

In this study,we used indoor pot experiments to simulate heavy metal pollution at different concentrations of Cd and Pb,and to explore the tolerance and repair characteristics of three invasive plants for the two heavy metals.The remedial potential of three invasive plants on heavy metal contaminated soils was studied.The main results are as follows:Chromolaena odorata showed strong tolerance and remediation characteristics to Cd stress.Plant height,length of root,biomass,photosynthetic rate,stomatal conductance,intercellular carbon dioxide concentration,CAT and POD activities in roots and leaves showed a tendency to rise first and then decrease.The content of Cd in leaves was the highest,followed by that in the stems and roots.With the increase of Cd concentration,the Cd content in the above-ground part increased with the increase of Cd concentration of 60mg·kg-1,the maximum root BCF could be up to 1.89,and the above-ground BCF could be up to 2.73,which are all more than the hyper-accumulator threshold 1.Chromolaena odorata showed strong tolerance and enrichment characteristics for Pb stress.As the increasing of the Pb concentration,plant height,length of root,biomass,photosynthetic rate,stomatal conductance,intercellular carbon dioxide concentration,CAT,POD are all going up and come down.The results showed that the Pb content of each organ was respectively reach 1029.37±23.44mg·kg-1,467.76±17.21mg·kg-1,272.54±2.97mg·kg-1.when the concentration of Pb was 800mg·kg-1,the maximum root BCF can reach 1.66,the BCF can reach 2.26,and the migration coefficient under the Pb stress of the Chromolaena odorata is greater than 1,which meets the requirement of Pb-rich plants.Bidens pilosa showed strong tolerance and remediation characteristics to Cd stress.The results showed that the plant height,root length,biomass,net photosynthetic rate,intercellular carbon dioxide concentration,and the concentration of carbon dioxide were significantly higher than those of the control group.The activities of CAT and POD in roots and leaves were increased first and then decreased,and both activities were higher at lower concentrations.The Cd contents in roots,stems and leaves of Bidens pilosa were increased with the increase of Cd concentration,and the differences among treatments were significant.The accumulation of Cd in above-ground plants was the same as that of the control group more than 65%.The root BCF of Bidens pilosa could reach 2.73,the above-ground BCF could reach 1.84,and the migration coefficient was more than 1,which reached the standard of Cd hyperaccumulator.Bidens pilosa showed strong tolerance and repair characteristics to Pb stress.The plant height,root length and biomass of Bidens pilosa were increasing with the increase of Pb concentration,and the photosynthetic rate,stomatal conductance,the activity of CAT and POD in roots and leaves increased first and then decreased.Pb content was the highest in roots,followed by stems and leaves.The Pb accumulation of roots,stems and leaves increased with the increase of Pb concentration,and the maximum root BCF could reach 1.95 and the above-ground BCF could reach 0.85,indicating that there was a certain tolerance to Pb,but the enrichment and remediation capacity did not reach the threshold for Pb hyperaccumulators.Eupatorium catarium has a certain tolerance to Cd stress,but its remediation capacity is not as good as that of Bidens pilosa and Chromolaena odorata.With the increase of Cd concentration,the plant height,root length,biomass,net photosynthetic rate,intercellular carbon dioxide concentration,stomatal conductance and CAT and POD activities in roots and leaves was increased first and then decrease.And the root BCF was up to 1.53 and the above-ground BCF was up to 0.98.The Eupatorium catarium had some tolerance to Pb stress,but its enrichment was not as good as that of Bidens pilosa and Chromolaena odorata.With the increase of Pb concentration,the plant height,root length,biomass,photosynthetic rate,intercellular carbon dioxide concentration,stomatal conductance and CAT and POD activities in roots and leaves was increased first and then decrease,the root BCF up to 1.65,the above-ground BCF up to 0.88,the migration coefficient is low.In summary,Chromolaena odorata and Bidens pilosa have strong tolerance and remediation ability to Cd and Pb,but the tolerance and repair ability of Eupatorium catarium to Cd and Pb are not as good as the other two plants.Therefore,the use of Chromolaena odorata and Bidens pilosa for remediation of Cd and Pb contaminated soil has great potential.