Effects Of Pb-Cd Stress On Growth And Physiological Characteristics Of Liquidambar Formosana Seedlings

With the continuous deterioration of soil lead and cadmium pollution,the theory and technology of urban environmental greening restoration has become a key research direction in landscape architecture and environmental ecology.Liquidambar formosana is a traditional garden tree species with great ornamental and garden value.It is of great significance to strengthen the research on the resistance of Liquidambar formosana to the introduction of heavy metal contaminated areas.Therefore,this experiment adopts a pot test method,using well-grown annual Liquidambar formosana seedlings as test materials to explore the effects of different concentrations of single lead,cadmium and compound stress on the growth and physiological characteristics of Liquidambar formosana seedlings;by analysis of variance,principal components The analysis method,Pearson correlation method,comprehensive evaluation of seedling quality and fuzzy membership function method were used to conduct a comprehensive analysis to explore the tolerance,response and adaptation mechanism of Liquidambar formosana to cadmium,lead and compound stress.The main findings are as follows:(1)Under single lead,cadmium,and lead-cadmium combined stress treatments,except for the ground diameter growth of Liquidambar formosana seedlings under the combined stress,the other growth morphological indicators showed a "low promotion and high suppression" effect.,The promotion effect is most significant at low concentrations,such as A3 or B3,and the promotion effect: single lead stress>single cadmium stress>compound stress;subsequent inhibition,And the inhibitory effect: compound stress>single cadmium stress>single lead stress.(2)Under the single lead,cadmium and lead-cadmium combined stress treatment,the root indexes of Liquidambar formosana seedlings have extremely significant differences.Each root index showed the phenomenon of "low promotion and high suppression",and the promotion effect: single lead stress>single cadmium stress> composite stress,but the low concentration of compound stress did not significantly promote the root index;the high concentration inhibition effect Significantly: compound stress> single cadmium stress> single lead stress.(3)Under the combined stress treatment of single lead,cadmium and lead-cadmium,the soluble sugar content,free proline content,SOD and POD activities of leaves of Liquidambar formosana seedlings showed an "up-down" trend;under the treatment of single lead and single cadmium stress,The soluble protein content in the leaves of Liquidambar formosana seedlings showed a“rising-declining”trend,showing a phenomenon of“low promotion and highinhibition”,which showed a“declining”trend under compound stress,and the inhibitory effect: compound stress> single cadmium stress> single lead stress Under the single lead,cadmium and lead-cadmium combined stress treatment,the content of malondialdehyde showed an "increasing" trend,and the promotion effect was: compound stress> single cadmium stress> single lead stress.(4)The photosynthetic pigments of Liquidambar formosana seedlings showed a "declining" trend under single lead treatment,and the photosynthetic pigments under single cadmium and compound stress treatments showed an "up-down" trend,showing "low promotion and high suppression".Under single lead,cadmium and combined stress treatments,the Pn,Gs,Ci and Tr of the leaves of Liquidambar formosana seedlings showed an "up-down" trend,showing a "low promotion and high inhibition" phenomenon;low concentration of single lead stress on maple The promotion effect of aroma photosynthesis is significant,and the single cadmium stress and the compound stress do not have significant effects on the photosynthesis of Liquidambar formosana;the high concentration lead and cadmium stress inhibit the photosynthesis of Liquidambar formosana seedlings: compound stress> single cadmium stress>single Lead stress.(5)The comprehensive analysis results show that in the comprehensive evaluation of seedling quality,A3 treated Liquidambar formosana seedlings had the best seedling quality,B3 followed by A6B6 the worst;the highest score ofthe main component is A3,followed by B3,and the lowest score of A6B6;the subsequent analysis of the membership index using the 19 indicators screened by the principal component analysis results in the indicators under A3 treatment The average membership value is the largest,B3 is the second,and the average membership value of A6B6 is the smallest,indicating that the indicators of the Liquidambar formosana seedlings perform better in the A3 and B3 treatments,and the worst performance of the indicators under the A6B6 treatment;finally,Pearson correlation analysis was performed on 19 indicators It is found that except for individual indicators,most indicators have significant or extremely significant positive correlations.(6)From the above analysis,it can be concluded that low concentrations of lead(?300mg/kg)and cadmium(?30mg/kg)can promote the growth of Liquidambar formosana seedlings to a certain extent,but the concentration is too high(>300mg/kg),Cadmium(>30mg/kg)will inhibit the growth of seedlings.Various analyses show that the Liquidambar formosana seedlings have certain tolerance and adaptability to lead and cadmium stress,and can be used in the treatment of lightly polluted soils with heavy metals.