Methyl Jasmonate and Cytokinin Mitigate the Salinity-Induced Oxidative Injury in Wheat Seedlings

Abstract

Application of methyl jasmonate (MeJA) has been shown to be effective in improving plant tolerance to various environmental stresses. Present research was conducted to explore the possible role of endogenous cytokinins (CK) in MeJA-mediated alleviation of oxidative stress in wheat plants (Triticum aestivum L.) subjected to sodium chloride salinity. We have compared the effects of 0.1 µM MeJA and 0.04 µM cytokinin 6-benzylaminopurine (BAP), both causing a twofold increase in the level of endogenous cytokinins, on the reactive oxygen species generation, antioxidant enzymes activities, levels of lipid peroxidation, and electrolytes leakage, as well as on the contents of proline and dehydrins under normal and salinity conditions. Salt stress significantly increased generation of superoxide anion and activity of both superoxide dismutase and peroxidase resulting in accelerated lipid peroxidation and electrolyte leakage and also elevated the contents of proline and dehydrins in wheat seedlings. Pretreatment with either MeJA or BAP reduced the salt-induced pro-oxidants/antioxidants imbalance as well as membrane damages. Meanwhile, both hormones promoted additional accumulation of proline and dehydrins under stress and enhanced the barrier properties of the cell walls in seedling roots by accelerating the lignin deposition. Similarity in the protective action of MeJA and cytokinin together with previous data on prevention of the decline in the cytokinin content in MeJA-pretreated salt-stressed wheat seedlings suggest the involvement of endogenous CK in MeJA-induced increase in salinity tolerance of wheat plants.