Alleviation of salt-induced adverse effects in pepper seedlings by seed application of glycinebetaine

Abstract

In this study, the possibility of enhancing salt stress tolerance of pepper (Capsicum annuum L.) during early growth stages by seed application of glycinebetaine (GB) was investigated. To improve salt tolerance during seedling stage, GB was applied in four different concentrations (0, 1, 5, or 25mM) as a pre-sowing seed treatment. When the seedlings reached four fully developed true leaf stage, they were either exposed to salt stress (150mM NaCl) for 2 weeks or allowed to grow under optimum conditions (0mM NaCl). Salt stress applied through the root medium markedly suppressed plant growth, however, seed application of GB provided significant protection against salt stress compared to non-GB-treated seedlings, considerably enhancing photosynthesis and chlorophyll and proline contents of the seedlings. GB pre-treatment also improved leaf water potential, relative water content, and superoxide dismutase (SOD) enzyme activity while reducing membrane permeability and lipid peroxidation. Moreover, GB pre-treatment reduced the accumulation of Na+ and Cl- contents and prevented salt-induced K+ leakage thereby maintaining a lower Na+/K+ ratio. Among the GB concentrations applied, the highest salt tolerance was obtained with 5mM GB pre-treatment. Results, therefore, indicate that GB, applied as pre-sowing seed treatment, could be used effectively to protect pepper seedlings from damaging effects of salt stress without any adverse effect on seedling growth. © 2012 Elsevier B.V.