Paclobutrazol application enhances antioxidant enzyme activities in pomegranate plants affected by cold stress

Paclobutrazol (PBZ) is a member of the triazole plant growth inhibitor group that is responsible for inducing tolerance to a number of biotic and abiotic stresses. An experiment was, therefore, conducted to test whether PBZ application at various concentrations (0, 25, 50, or 75mgL(-1)) through foliar spray or soil drench would protect pomegranate (Punica granatum) seedlings cv. Robab, subjected to freezing at -3 degrees C for 7hours. PBZ improved the growth rate of pomegranate seedlings subjected to freezing stress and increased relative leaf chlorophyll content, chlorophyll fluorescence ratio, relative water content, soluble carbohydrate content, and enzyme activity of ascorbate peroxidase and guaiacol peroxidase compared with the control at the end of experiment. PBZ ameliorated the injury caused by freezing stress by inhibiting increases in proline content and leaf electrolyte leakage, which suggested that PBZ ameliorated the negative effect of freezing stress. The best protection was obtained from plants treated with PBZ at 50 or 75mgL(-1). The most evaluated parameters were not affected by PBZ application method.