Castasterone assisted accumulation of polyphenols and antioxidant to increase tolerance of B. juncea plants towards copper toxicity

Abstract

The concentration of copper in soil is increasing, which may potentially affect the crop yield. Brassinosteroids are well known to enhance tolerance towards abiotic stress, but role of castasterone in this context is poorly understood. The present study was designed to explore the potential of castasterone to enhance copper tolerance in Brassica juncea plants. Results indicate that copper increased the production of superoxide anion radical and hydrogen peroxide, maximum at 0.75 mM of copper exposure (31.71 and 68.29% at 60 days). This overproduction of reactive oxygen species hampered the photosynthetic pigments and gas exchange parameters. Application of castasterone as seed soaking method significantly activated the enzymatic defense system. Superoxide dismutase, polyphenol oxidase and catalase showed maximum enhancement in the activities. The study further highlighted the modulations of polyphenols in B. juncea with castasterone and copper. Phenolic profiling shows that accumulation of polyphenols increase with the castasterone application under copper stress. Caffeic acid, ellagic acid, catechin and chlorogenic acid were the most prominent polyphenols observed in this study.