Genotypic differences in antioxidative ability and salt tolerance of three poplars under sact stress

In order to evaluate genotypic difference in antioxidative ability and salt tolerance in poplars, the authors investigated the effects of increasing soil NaCl content on salt concentration in leaves, superoxide dismutase (SOD), peroxidase (POD) activities, malondialdehyde (MDA) content and membrane permeability in Populus euphratica Oliv. and P. popularis '35-44 ' and P. × euramericana cv. I-214.Na ⁺ and Cl concentrations in leaves of P.popularis markedly increased over the increase of the duration of exposure to salinity, and culminated after 28 d of salt stress.SOD and POD activities declined correspondingly, followed by significant increases of MDA and membrane permeability, and leaf injury was eventually observed.Leaf Na ⁺ and Cl^- in P.×euramericana cv. I-214 exhibited a trend similar to P.popularis, but a lower salt-induced increase of MDA and permeability was observed and lighter leaf necrosis occurred, compared with P.popularis.In contrast to P.popularis and P.×euramericana cv.I-214, leaf SOD and POD activities in P.euphratica increased rapidly at the beginning of salt stress with a light soil NaCl concentration of 58.5 mmol/L.Furthermore, salt ion concentration, MDA content and membrane permeability in leaves of P.euphratica did not significantly increase during 28 d of increasing salt stress.Therefore, the increase of membrane permeability in P.popularis and P.×euramericana cv.I-214 was related with a salt buildup in leaves under increasing salt stress.Salt-induced declines of SOD and POD activity might accelerate lipid peroxide and consequently resulted in ion leakage. P.euphratica rapidly activated antioxidant enzymes after the onset of salt stress, which might reduce reactive oxygen species (ROS) accumulation and the subsequent acceleration of lipid peroxide. P.euphratica leaves exhibited a higher capacity to exclude salt in a longer term of increasing salinity, thus limited salt-induced lipid peroxide and membrane permeability, which contributed to membrane integrity maintenance and salt tolerance of P.euphratica.