Epibrassinolide ameliorates Cr (VI) stress via influencing the levels of indole-3-acetic acid, abscisic acid, polyamines and antioxidant system of radish seedlings

Abstract: The present investigation determined the effects of epibrassinolide (EBL) on the levels of indole-3-acetic acid (IAA), abscisic acid (ABA), and polyamine (PA) and antioxidant potential of 7-d old Raphanus sativus L. cv. ‘Pusa chetki’ seedlings grown under Cr (VI) metal stress. Reduced titers of free (0.767μgg−1 FW) and bound (0.545μgg−1 FW) IAA in Cr (VI) stressed seedlings were observed over untreated control. Supplementations of EBL to Cr (VI) stressed seedlings were able to enhance both free (2.14–5.68μgg−1 FW) and bound IAA (2.45–7.78μgg−1 FW) concentrations in comparison to Cr (VI) metal treatment alone. Significant rise in free (13.49μgg−1 FW) and bound (12.17μgg−1 FW) ABA contents were noticed for Cr (VI) stressed seedlings when compared to untreated control. No significant increase in ABA contents were recorded for Cr (VI) stressed seedlings upon supplementation with EBL over Cr (VI) treatment alone. A significant increase in Put (18.40μgg−1 FW) and Cad (9.08μgg−1 FW) contents were found for 10−9 M EBL plus Cr (VI) metal treatments when compared to Cr (VI) treatment alone. Spermidine (Spd) contents were found to decline significantly for EBL treatment alone or when supplemented with Cr (VI) treatments over untreated controls and Cr (VI) treatment alone. Antioxidant levels were found to enhance, with glutathione (57.98mgg−1 FW), proline (4.97mgg−1 FW), glycinebetaine (39.01μmolmL−1), ascorbic acid (3.17mgg−1 FW) and phytochelatins (65.69μmolg−1 FW) contents noted for EBL supplemented to Cr (VI) metal solution over Cr (VI) treatment alone. Reduced activities of guaiacol peroxidase (0.391 Umg−1 protein) and catalase (0.221Umg−1 protein) and enhanced activities of glutathione reductase (7.14Umg−1 protein), superoxide dismutase (15.20Umg−1 protein) and ascorbate peroxidase (4.31Umg−1 protein) were observed in seedlings treated with EBL plus Cr (VI) over Cr metal treatment alone. Reduced MDA (2.55μmolg−1 FW) and H2O2 (33.24μmolg−1 FW) contents were recorded for 10−9 M EBL supplemented to Cr (VI) stress over Cr (VI) treatment alone. Enhancement in free radical scavenging potential as indicated by higher values of 1,1-diphenylpicrylhydrazyl, deoxyribose and reducing power activity assays, and increased levels of phenols and soluble sugars also showed significant influence of EBL in alleviating Cr (VI) stress in radish seedlings. [Copyright &y& Elsevier]