Growth And Physiological Mechanism Of Phoebe Chekiangensis Seedlings In Response To Lead Nitrate Stress

This experiment uses annual Phoebe chekiangensis seedlings as experimental material,which has researched the influence of seedling growth,physiology and photosynthesis under the stress of different concentration of Pb?NO₃?₂ solution from 0?300 ? 600 ? 900 to 1200 mg/L.By measuring their growth,physiological and photosynthetic indexes to analyze its resistance to heavy metal Pb?NO₃?₂.The results indicate that:1.Different concentration of Pb?NO₃?₂ solution make different influence on Phoebe chekiangensis of different growth index.With the increase of concentration of Pb?NO₃?₂,the tendency of Phoebe chekiangensis seedling height,base diameter growth,biomass above ground and underground part of the whole biomass,root biomass,total root surface area,root volume,total root length and root activity increases first while decreases afterwards,and those growth index are all at the maximum of 300 mg/L of Pb?NO₃?₂ solution.Through multiple comparison,the results showed that the seedling height growth,diameter growth,the total number of root,total root length and root activity are significantly higher than that of control while root-top ratio basically present a rising trend.2.Different concentration of Pb?NO₃?₂ solution make different influence on Phoebe chekiangensis physiological indexes as well.With the increase of concentration of Pb?NO₃?₂,the conductivity and MDA content of Phoebe chekiangensis seedlings shows a trend of rise after the first reduce,the minimum value is at 300 mg/L,and significantly less than the control?P < 0.05?;while the POD,SOD and CAT activity increases firstly but decreases afterwards,and the stress concentration peak is at 300 mg/L.Among the CAT activity is significantly higher than control?P < 0.05?.Besides,the protein content and chlorophyll content also present a trend of decrease after the first increase,and peaked at 600 mg/L,among the maximum of protein content is significantly higher than control?P < 0.05?.3.The different concentration of Pb?NO₃?₂ solution also affects the photosynthesis of Phoebe chekiangensis.With the increase of concentration of Pb?NO₃?₂,the net photosynthetic rate,stomatal conductance,intercellular CO2 concentration,transpiration rate are all increase at first then decrease with the peak at 300mg/L,and all significantly higher than control?P < 0.05?;Water use efficiency present a rising trend overall.4.According to correlation analysis: the growth index?seedling height growth,diameter growth,above ground biomass,underground biomass,whole plant biomass?are positive correlated significantly?P < 0.01?,and significantly positive correlated to root activity?P < 0.05?,significantly negative correlated with conductivity?P < 0.01?,while are significantly or extremely significantly negatively correlated to MDA content?P < 0.05 or P < 0.01?,also significantly or extremely significantly positive correlated to POD,SOD and CAT activity?P < 0.05 or P < 0.01?,and shows a significant positive correlation to photosynthesis indicators?P < 0.05?.While root growth indicators?total root number,total root surface area,total root length,root volume,root activity?are all significantly positive correlated with each other?P < 0.01?,except the root activity is unrelated to other root growth index?P > 0.05?,also,other root growth index are all significantly positive correlated?P < 0.05?,but electrical conductivity and MDA content are significantly negative correlated?P < 0.05?,and the SOD activity is significantly positively correlated?P < 0.05?,significantly or extremely significantly positively correlated to photosynthesis indexes?P < 0.05 or P < 0.01?.Through comprehensive analysis and comparison,the low concentration of Pb?NO₃?₂ solution can promote the growth of Phoebe chekiangensis seedlings to a certain extent,but high concentration of Pb?NO₃?₂ solution has obvious inhibitory effect on the growth of Phoebe chekiangensis.This study found that Phoebe chekiangensis seedlings can grow well under the Pb?NO₃?₂ solution of 300 mg/L,and begin to show the stress function from concentration of 600 mg/L of Pb?NO₃?₂ solution,and shows significant concentration of 900,1200 mg/L of Pb?NO₃?₂ solution,which receives an obvious inhibition.The experiment results shows that: Phoebe chekiangensis seedlings has a certain resistance to Pb?NO₃?₂,it is suitable to promote planting in some Pb?NO₃?₂ pollution areas.