Heavy metal toxicity induced by sewage water treatment in three different vegetables (lettuce, spinach and cabbage) was alleviated by brassinosteroid and silicon supplementation

Abstract

Purpose: Heavy metal stress due to the application of sewage water is considered a leading factor for constrained plant growth. Therefore, Current study was performed in the field to investigate the interactive influence of two irrigation sources (canal and sewage) and exogenous application of brassinosteroid (BRs) and silicon (Si) at different rates on growth, photosynthetic and physiological attributes of three leafy vegetables (lettuce, cabbage, and spinach). Methods: Three treatments were applied such as control, BRs and Si with three replications under split plot factorial design. Results: The results indicated that all the growth parameters including fresh biomass of plants and roots, dry biomass of plant and root, leaf area (LA), photosynthetic traits, chlorophyll contents, water use efficiency (WUE), activity of antioxidant enzymes; superoxide dismutase (SOD), peroxidase (POD), Catalase (CAT), ascorbate peroxidase (APX) and uptake of silicon except Cd and Pb contents were improved significantly with the foliar spray of BRs and Si over control treatment under both types of irrigation sources. However maximum improvement in leafy vegetables was recorded when the foliar spray of BRs and Si were applied under canal water irrigation. Conclusions: The foliar application of BRs and Si was proved as an ameliorating strategy for improving tolerance mechanisms associated with heavy metal stress. The major restoring mechanism was the restricted translocation of Cd and Pb leading to better growth and physiology under sewage water. Thus the application of BRs and Si reduced the detrimental effect of Cd and Pb led to improve the growth and physiological traits of leafy vegetables under irrigation with sewage water.