Influence of brassinosteroid and silicon on growth, antioxidant enzymes, and metal uptake of leafy vegetables under wastewater irrigation

Abstract

Vegetable cultivation under sewage irrigation is a common practice mostly in developing countries due to a lack of freshwater. Long-term usage provokes heavy metals accumulation in soil and ultimately hinders the growth and physiology of crop plants and deteriorates the quality of food. A study was performed to investigate the role of brassinosteroid (BRs) and silicon (Si) on lettuce, spinach, and cabbage under lead (Pb) and cadmium (Cd) contaminated sewage water. The experiment comprises three treatments (control, BRs, and Si) applied under a completely randomized design (CRD) in a growth chamber. BRs and Si application resulted in the highest increase of growth, physiology, and antioxidant enzyme activities when applied under canal water followed by distilled water and sewage water. However, BRs and Si increased the above-determined attributes under the sewage water by reducing the Pb and Cd uptake as compared to the control. It’s concluded that sewerage water adversely affected the growth and development of vegetables by increasing Pb and Cd, and foliar spray of Si and BRs could have great potential to mitigate the adverse effects of heavy metals and improve the growth. The long-term alleviating effect of BRs and Si will be evaluated in the field conditions at different ecological zones.

STATEMENT OF NOVELTY

Numerous studies evaluated the effect of Brassinosteroid (BRs) and Silicon (Si) to mitigate heavy metal stress in vegetables through soil application. However, research on the foliar application of both BRs and Si to improve vegetable growth under heavy metal stress is very limited. Moreover, most researchers used only a single source of irrigation water but in our study, three different water sources including distilled water (CW), canal water (CW), and sewage water (SW) were used to evaluate their impact on growth, physiology, and antioxidant activities of leafy vegetables. In this way, this study could be the first in terms of specific vegetable crops (lettuce, spinach, and cabbage) and evaluated for their growth and development performance and antioxidant activities under three different types of irrigation sources with foliar application of BRs and Si.

HIGHLIGHTS

1. Brassinosteroid and Silicon improved the growth of leafy vegetables.

2. Sewage water hindered the growth and physiological parameters of lettuce, spinach, and cabbage.

3. Brassinosteroid and Silicon mitigated the heavy metal-induced stress in leafy vegetables.

Keywords:

• Ascorbate peroxidase
• cabbage
• cadmium
• catalase
• lead
• lettuce
• spinach
• superoxide dismutase

Acknowledgments

The authors are thankful to the anonymous reviewer.

Conflicts of interest

No conflicts of interest have been declared.