EVALUATION OF SALT TOLERANCE MECHANISMS IN ALFALFA (MEDICAGO SATIVA L.) THROUGH MORPHOLOGICAL AND PHYSIOLOGICAL PARAMETERS

Responses to salt stress were investigated in three alfalfa varieties (Gabès, Hunterfield, and Hyb.555). Seedlings were submitted to salinity induced by adding NaCl into water at 4 concentrations (0 - 2.5 - 5 and 10g.l-1). Growth parameters (DM, plant height, LA, LAR, SLA, leaves thickness, succulence), and hydraulic parameters (RWC, WC, WUE) were investigated in leaves, stems and roots after three months of salt stress. Results showed that NaCl decreased DMY of the three varieties. However, Gabès variety, compared to Hunterfield and Hyb.555 has a DMY significantly higher, in the absence and presence of NaCl. The severe decrease in the DMY of the introduced varieties was related to the premature senescence accelerated by the salt intensity and the duration. On the other hand, Gabès variety has a well-equilibrated distribution of DM between organs. The LAR and the SLA decreased significantly with the salt increasing. The salt increased the leaves thickness and succulence. WC increased in concomitance with the rise of leaf succulence. WUE under salt stress decreased in the three lucernes. However, Gabès variety has WUE significantly higher in all salt treatments. This study allowed highlighting the interest of the Gabès variety in any selection program for salt tolerance