EFFCTS OF SALT STRESS ON GROWTH AND PHYSIOLOGICAL CHARACTERISTICS OF POMEGRANATE (PUNICA GRANATUM L.) CUTTINGS

With 2-years-old pomegranate (Punica granatum L.) cv. 'Tunisia' cuttings as materials, the growth properties, salt injury indexes, leaf membrane permeability, Chlorophyll (Chl) content, malondialdehyde (MDA) content, proline and soluble protein content, and activities of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) were investigated under different NaCl concentrations (0, 0.1, 0.2, 0.3, 0.4, 0.5, and 0.6%, w/w) treatments after 7, 21 and 35 days. The results showed that: the height and ground diameter of pomegranate were increased at low salinity (0.1%), and they were significantly inhibited at high salinity (>= 0.5%). With increased NaCl concentrations, Chl a, Chl b, and Chl (a + b) contents were decreased and chlorophyll a/b were increased. Leaf membrane permeability was seriously enhanced and the amount of MDA was markedly increased at high salinity (>= 0.5%). The proline and soluble protein were significantly accumulated and quickly responded to NaCl stress. The activities of SOD, CAT, and POD showed a trend of first rising and then decreasing, with the maximum appearing at 0.4% salinity. In addition, the adverse effects on these physiological indexes aggravated gradually over time. Our study suggested that pomegranate 'Tunisi' was a moderately salt tolerant cultivar (0.4% NaCl) with a promoting effect on the growth below 0.1% salinity. This cultivar presents a mechanism of alleviating the detrimental effects of salt stress through improving the proline content, soluble protein content and the activities of antioxidant enzymes. But the protections of antioxidant enzymes are in a limited range of salinity.