Effect of salinity on sodium and chloride uptake, proline and soluble carbohydrate contents in three alfalfa varieties

Abstract

Salinity stress affected severely plant growth and production. Indeed, soil salinity represented one of the most important environmental stresses, which caused serious threats to agriculture and also results in the deterioration of environment. Accumulation of sodium, chloride, proline and soluble sugars was investigated in leaves, stems and roots of three alfalfa varieties (Hunterfield, Hyb.555 and Gabès) at the late bloom-early pod stage. The study was conducted in a greenhouse for 90 days of salt stress in whole-plants. Plants were irrigated with top water with four NaCl concentrations: (0 – 2.5 – 5 and 10g.l-1). Results showed that all varieties accumulated high Na+ and Cl- contents in leaves and stems. Gabès variety differed from Hunterfield and Hyb.555 with Na+ and Cl- contents significantly lower in leaves at the stressful treatments. Furthermore, Gabès proline content at 5 and 10g.l-1 NaCl in three organs was significantly higher than in the introduced varieties. Proline content in leaves, stems and roots increased with the rise of salt in pots, reaching a significantly higher level for Gabès at the stressful treatment (10g.l-1). Soluble sugar content in leaf tissue was higher in Gabès than those in the introduced varieties at the stressful treatments (5 and 10g.l-1). Contrary to the air parts (leaves and stems), soluble sugar contents in roots for Hunterfield and Hyb.555 are significantly higher, compared to Gabès variety, at the stressful treatment. This could be probably related to the difficulty in generating new leaves in Hunterfield and Hyb.555 varieties.