Abstract

The present work focused on evaluation of the physiological and metabolic behavior of alfalfa (Medicago sativa L., var. Siriver), when faced with two important ecosystems constraints, namely salinity and flooding-associated hypoxia. After germination, seedlings in symbiosis with Sinorhizobium meliloti were grown on different salt concentrations (0, 20 and 50 mM NaCl). At four weeks post-germination, plants were submitted to a five-day long flooding treatment and then analyzed for various physiological (growth, biomass) and biochemical (proteins, chlorophylls, ions, proline) parameters. Our results showed that when M. sativa was cultured on moderate (20 mM NaCl) or average (50 mM NaCl) salt stress, the classical mechanisms of stress response (ions and proline accumulation) are set up and the growth (FW, DW, growth of aerial parts) was moderately affected by salt. In a situation of average salt stress (50 mM NaCl), the combined salinity and short-term flooding led to an early alteration of the photosynthetic machinery and a modification of ions and proline contents in the leaves.

Key words: Chlorophyll, hypoxia, legume, NaCl, proline, salinity.