Effect of paclobutrazol and salinity on ion leakage, proline content and activities of antioxidant enzymes in mango (Mangifera indica L.)

A study was conducted to investigate the effects of paclobutrazol (PBZ) on ion leakage (IL), proline content and activities of antioxidant enzymes like superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) of 1-year-old 'Olour' mango plants subjected to NaCl stress. Plants were treated with two levels of salt, i.e., 0.0 g NaCl (control) and 25 g NaCl/25 kg soil and three levels of paclobutrazol (PBZ) solution (0.0 (control), 750 and 1500 mg/l). Ion leakage, proline content and activities of antioxidant enzymes were significantly altered by both salinity and PBZ treatments. Results indicated that PBZ (1500 mg/l) mitigated the salinity stress and reduced ion leakage of mango seedlings by 64% over non-PBZ-treated salinised plants. PBZ upregulated the endogenous proline content and salinised plants treated with PBZ (1500 mg/l) had 17% higher proline content than salinised plants without PBZ treatment. Higher antioxidant enzyme activity was also observed in salinised plants treated by PBZ than salinised plants without PBZ treatments. Moreover, higher dose of PBZ (1500 mg/l) resulted in higher activity of these enzymes in mango leaves. In comparison to salinised plants without PBZ treatment, salinised plants treated with PBZ (1500 mg/l) had higher SOD (24%), CAT (46%) and POD (163%) activities. Our results suggest that PBZ application under salt stress conditions alters the equilibrium between free radical production and enzymatic defense reactions in mango by enhancing the proline content and free radical scavenging capacity. (C) 2010 Elsevier B.V. All rights reserved.