Alleviation of water stress effects on pepper seedlings by foliar application of glycinebetaine

In this study, the possibility of enhancing water stress tolerance of pepper during early growth stages by foliar application of glycinebetaine (GB) was investigated. Pepper seedlings with four true leaves were sprayed with three different concentrations (0, 5 or 25 mM) of GB after which they were subjected to water stress for 10 days. Water stress caused substantial reductions in shoot dry weight, leaf area, chlorophyll content, leaf water potential, gas exchange characteristics and efficiency of photosystem-II while increasing membrane permeability and lipid peroxidation. However, foliar application of GB significantly counteracted the water stress-induced adverse effects by increasing chlorophyll content, stomatal conductance, efficiency of photosystem-II and proline content, while reducing visual damage symptoms, membrane permeability and lipid peroxidation. GB application also improved leaf water potential, relative water content and antioxidant enzymatic activity. Among the GB concentrations applied, enhanced water stress tolerance was obtained with 5 mM GB pre-treatment. Results, therefore, indicate that GB, applied as foliar spray, could be used as an ameliorative agent for pepper seedlings against the deleterious effects of water stress.