Physiological Response And Absorption Characteristics Of Illicium Verum Seedlings To Lead And Cadmium Stress

Taking the prevention and control of soil heavy metal pollution in Guangxi Zhuang Autonomous Region,as an opportunity to study the physiological response and absorption characteristics of annual Illicium verum seedlings under heavy metal lead（Pb）and cadmium（Cd）stress,to provide scientific basis for the cultivation and management of I.verum seedlings and the bioaccumulation and translocation characteristics of lead and cadmium elements in plants.In this study,I.verum seedlings are used as test materials,and potted stress tests are carried out through different concentrations of Pb(Pb₅₀₀,Pb₁₀₀₀,Pb₁₅₀₀),Cd(Cd₁₀,Cd₂₅,Cd₅₀)and compound(Pb₅₀₀Cd₁₀,Pb₅₀₀Cd₅₀,Pb₁₅₀₀Cd₁₀,Pb₁₅₀₀Cd₅₀)solutions to determine the growth physiology and absorption characteristics of I.verum seedlings under different treatments.Seedling quality index,tolerance index,membership function analysis and principal component analysis are used to comprehensively compare each treatment.The main findings are as follows:（1）The comprehensive effect of Pb and Cd stress on the growth of I.verum seedlings is shown as"low concentration promotion,high concentration inhibition"under single Pb stress and single Cd stress,and inhibites under compound stress.When the concentration of Cd≤1000mg/kg,and Cd concentration≤10mg/kg is less than or equal to 10 mg/kg,the quality index and tolerance index of I.verum seedlings are higher,and the growth is better.In compound stress,the effect of Cd element on the growth of I.verum seedlings is more dominant than that of Pb element.The order of inhibitory effects of the three stresses is:Pb-Cd compound stress>single Cd stress>single Pb stress.（2）Under the stress of low concentrations of Pb and Cd,the chlorophyll content,osmotic adjustment substances and antioxidant enzyme activities of I.verum seedlings can respond to the stress and activate the defense mechanism through energy supply,osmotic pressure regulation,cell protection and scavenging excess reactive oxygen species,and other ways to reduce the harm of stress to I.verum seedlings.With the increase of stress concentration,the chlorophyll content of I.verum seedlings decreased,the degree of oxidative damage increased,the enzyme system collapsed and the cell membrane structure destroyed,which eventually leads to metabolic disorders and weakened defense capabilities.The order of inhibitory effects of the three stresses is:Pb-Cd compound stress>single Cd stress>single Pb stress.（3）The absorption of lead and cadmium by I.verum seedlings is mainly concentrated in the roots and stems,and the absorption ratio of leaves is less.Compound stress had different interactions on Pb and Cd uptake.At low concentrations,compound stress has antagonistic effects on Pb absorption and bioaccumulation in I.verum seedlings,and synergistic effects on Cd.（4）Through membership function evaluation and principal component analysis,it can be seen that the evaluation of heavy metal stress in I.verum seedlings can be evaluated by three main component indicators,including the first principal component on growth and development,tolerance and resistance,and on osmotic regulation,root status and Heavy metal absorption,the second main component of cell stability,and the third main component of protection regulation and antioxidant capacity.Finally,it was concluded that the quality of I.verum seedlings was higher and the resistance was stronger when Pb stress≤1000 mg/kg and Cd stress≤10mg/kg.Under high concentration stress,the quality of seedlings was lower,and the stress resistance was weakened.The stress resistance of I.verum seedlings to Pb and Cd stress was ranked as single Pb stress>single Cd stress>Pb and Cd combined stress.