Salinity is one of the major environmental constraints limiting agricultural productivity in the world. The effects of salt stress on growth, ions and organic solutes accumulation were investigated in two amaranth (Amaranthus cruentus) cultivars: Rouge (salt-resistant) and Locale (salt-sensitive). Young plants of these cultivars were exposed, in hydroponic system, to three concentrations of NaCl: 0, 30 and 90 mM. Growth parameters, ions, free proline and soluble sugars concentrations were determined after 2 weeks of stress. NaCl effect resulted in plant growth reduction in both cultivars but plants of cultivar Rouge were less affected compared to that of cv. Locale. Na+, proline and soluble sugars concentrations increased significantly in leaves and roots under salinity while K+, Ca2+ and Mg2+ concentrations decreased in both cultivars. Proline and soluble sugars increased significantly in leaves and roots of cultivar Locale whereas in cultivar Rouge, proline increase was significant only in roots and soluble sugars increase was significant only in leaves. The highest increase of Na+ concentration occurred in leaves of cv. Rouge coupled with the lowest reduction in K+ concentration. The highest increase of proline occurred in leaves of cultivar Locale whereas the highest increase of soluble sugars was observed in leaves of cultivar Rouge. The reduction of the Ca2+ concentration under salt stress was more accentuated in both leaves and roots of cultivar Rouge than cultivar Locale while cv. Rouge maintained higher content in Mg2+ either in leaves or in roots in the presence of NaCl than cultivar Locale. These results suggest an implication of Na+, K+ and Mg2+ in salt resistance in these cultivars and that soluble sugars may play an important role in salt-resistance in Amaranthus cruentus. However, proline appears as a symptom of injury in stressed plants rather than an indicator of resistance.
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