Effects of Cadmium and Zinc Applied To the Soil Enriched With Sewage Sludge on Plant Growth and Antioxidative Enzyme Activity of Lettuce (Lactuca Sativa L. Var. Longifolia)

Abstract

The aim of this study is to investigate the effects of a constant rate of sewage sludge (SS) together with cadmium (Cd) and zinc (Zn) at varying levels on the growth of lettuce and antioxidative enzyme activity. In the pot experiment, a fixed ratio of 10%SS with varying doses of Cd (Cd1:50 mg Cd kg-1; Cd2:100 mg Cd kg-1) and Zn (Zn1:250 mg Zn kg-1; Zn2:500 mg Zn kg-1) was applied. According to experiment results, compared to the control, 10% SS + Cd1 and 10% SS + Cd2 applications significantly reduced fresh and dry shoot weights, plant height, Zn content and SOD (superoxide dismutase) enzyme activity in the root and shoot of lettuce. However, 10%SS +Cd1 and 10%SS+Cd2 applications significantly increased shoot and root Cd contents, GPX (glutathione peroxidase) enzyme activity in plant and the amount of Cd in soil. On the other hand, 10%SS+Zn1+Cd1 application increased fresh shoot weight, Zn content, SOD and GPX enzyme activities in the shoot of lettuce and decreased the amount of DTPA-Cd in comparison with 10%SS+Cd1 application. Compared to the Cd1 application, 10%SS+Zn2+Cd1 application increased SOD and GPX enzyme activities in the root of lettuce. In comparison with 10%SS +Cd2 application, 10%SS+Zn2+Cd2 application increased fresh and dry shoot weight, Zn content, SOD and GPX enzymes in both shoot and root of lettuce and decreased shoot Cd content and the amount of DTPA-Cd in soil. These results indicate that the Zn application could be beneficial for reducing the toxic effects of Cd in lettuce. © 2019, Centenary University. All rights reserved.