Minerals Uptake, Organic Osmotica Contents and Water Balance in Alfalfa under Salt Stress

Abstract

Organic osmotica contents (proline, soluble sugars), minerals (sodium and potassium), osmotic and water potentials were investigated in leaves, stems and roots of three alfalfa varieties, at the late bloom-early pod stage. Varieties (Gabès, Hunterfield, and Hyb.555) were irrigated with water having four NaCl concentrations: (0g.l^-1; 2.5g.l^-1; 5g.l^-1 and 10g.l^-1). Results showed that all varieties accumulated high Na⁺ and low K⁺ contents in leaves and stems. However, the local variety Gabès differed from the other ones by significantly lower Na⁺ and higher K⁺ contents in leaves at the highest salt concentration. Furthermore, its proline content at 5 and 10g.l^-1 NaCl was significantly higher in leaves, stems and roots than in Hunterfield and Hyb.555 varieties. Nevertheless, proline content in the different plant parts increased with increasing salt concentration in the medium, reaching a significantly higher level for Gabès at the greatest salt concentration (10g.l^-1). Leaf tissue soluble sugar contents in Gabès were higher than those recorded for Hunterfield and Hyb.555 varieties at 5 and 10g.l^-1 treatments. However, stems had similar sugar contents in the three varieties. Soluble carbohydrate contents in root tissues of Hunterfield and Hyb.555 were higher than in those of Gabès. This could probably be related to the difficulty in generating new leaves in both introduced varieties. Water potential (Yw) decreased in three varieties with increasing of NaCl. The Yw for Gabès variety was lower, compared to the introduced alfalfa. In the same way, osmotic potential (Ys) decreased with the increase of the salt at the three varieties. The Ys of Gabès reached a lower level in the most stressful treatment, compared to the introduced varieties.

Key words: Alfalfa, Osmotic potential, Potassium, Proline, Salinity, Sodium, Soluble sugar, Water potential

Mezni M et al. Minerals Uptake, Organic Osmotica Contents and Water Balance in Alfalfa under Salt Stress. J Phytol 2/11 (2010) 01-12