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.
Highlights
Cadmium (Cd) is a non-essential and toxic heavy metal (Grant et al, 1998)
Plant cell which is exposed to Cd stress activates enzymatic defence mechanism including superoxide dismutase (SOD), glutathione-S-transferase (GST), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR) (Hana et al, 2008; Monterio et al, 2009; Lin and Aarts, 2012; Viehweger, 2014)
The application of 10% sewage sludge (SS) alone did not have a significant impact on shoot length, shoot fresh weight and shoot dry weight in lettuce compared to the control due to low Cd content. 50 mg Cd kg1(Cd1) and 100 mg Cd kg-1 (Cd2) additions decreased shoot length, shoot fresh and dry weight compared to the control in lettuce (Table 2)
Summary
Cd is very taken up by plant roots and accumulates in plants due to its much more mobile nature relative to other heavy metals. Various crops such as lettuce and spinach, grown in heavy metal polluted soils accumulate large amounts of Cd. Various crops such as lettuce and spinach, grown in heavy metal polluted soils accumulate large amounts of Cd This causes heavy metals to join the food chain (Monterio et al, 2009). Cd has been found to induce oxidative stress in cells leading to the accumulation of reactive oxygen species (ROS) (Liu et al, 2008). Plant cell which is exposed to Cd stress activates enzymatic defence mechanism including superoxide dismutase (SOD), glutathione-S-transferase (GST), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR) (Hana et al, 2008; Monterio et al, 2009; Lin and Aarts, 2012; Viehweger, 2014)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
