| The objective of this experiment is to study changes in the antioxidant enzyme activity,Pb accumulation and trasportion in Platycladus orientalis and Robinia pseudoacaciaSeedlings grown under combined rhythmic drought and lead stress.In this study, potexperiment was combined with laboratory analysis method. Using the design of quadraticregression general rotation including three factors (water supply at early growth stage, fastgrowing stage and late growth stage of Platycladus orientalis and Robinia pseudoacacia) andfive levels(40,52.16,70,87.84and100%of soil water holding capacity). The main resultsare as follows:(1) At early growth stage of Robinia pseudoacacia seedlings, combined Pb and droughtstress had antagonistic effect on SOD and CAT activity, but had synergy on POD activity.SOD, POD and CAT activities are at high standard under combined Pb (2000mg kg-1) andsevere drought stress. Minor drought stress during the growing years will help improveseedling’s ability of removing superoxide and peroxide. Sufficient water supply during thegrowing years will help improve seedling’s ability of catalyzing decomposition of hydrogenperoxide.(2) At early growth stage of Platycladus orientalis seedlings, combined Pb and drought(52.16~87.84%of soil water holding capacity) stress had antagonistic effect on SOD and CATactivity. Combined stress had synergy on POD activity. Minor drought stress at early and fastgrowing stage, mild drought stress at late growth stage will help improve seedling’s ability ofremoving superoxide. Mild drought stress at early and fast growing stage, minor droughtstress at late growth stage will help improve seedling’s ability of removing peroxide. Minordrought stress during the growing years will help improve seedling’s ability of catalyzingdecomposition of hydrogen peroxide.(3) The lead accumulation of Robinia pseudoacacia seedlings in root is the most, that inthe leaves is less than that in the root, that in the stem is the least. Translocation factor (TFPb)of Robinia pseudoacacia seedlings in each treatment was less than1. The Pb contents in theplants varied from20.49~92.71mg kg-1(organ),39.23~176.51mg kg-1(roots),3.62~26.51 mg kg-1(stems) and4.92~47.32mg kg-1(leaves). Mild drought stress at early growth stage,minor drought stress at fast growing stage, moderate drought stress at late growth stage willhelp improve the ability of accumulating Pb.(4) The lead accumulation of Platycladus orientalis seedlings in root is the most, that inthe leaves is less than that in the root, that in the stem is the least. Translocation factor (TFPb)of Platycladus orientalis seedlings in each treatment was less than1. The Pb contents in theplants varied from51.19~128.38mg·kg-1(organ),155.41~350.36mg·kg-1(roots),8.47~48.71mg·kg-1(stems) and17.28~82.82mg·kg-1(leaves). Sufficient water supply at early growthstage, minor drought stress at fast growing stage, moderate drought stress at late growth stagewill help improve the ability of accumulating Pb. |
