Understanding mechanisms involved in the response of plants to environmental stress is a prequisite for chooising a suitable genotype for a given environment. Present study was carried out to identify morphological and physiological parameters that might be involved in adaptation of sunflower to salt conditions. Five sunflower genotypes (Oro 9, Mirasol, Flamme, Pinto and Ludo) were submitted, under greenhouse conditions, to four NaCl concentrations (0, 50, 75 and 100 mM). Results showed that increasing NaCl concentrations in the medium significantly reduced all morphological parameters of genotypes. Leaf area was more affected (-72% for Oro 9), followed by the plant height (-67% for Ludo). Root lenght and root volume were also affected. Sodium chloride depressed more root growth than shoot growth of all genotypes. Chlorophyll content declined drastically at 100 mM NaCl (-61,67%). Mirasol displayed the highest chlorophyll content. At the opposite, amino acids (AA) content of both leaves and roots of stressed plants increased as NaCl concentrations in the medium was increased. Oro 9 and Pinto accumulated less AA in their shoots whereas Ludo accumulated more. Under stress conditions, all genotypes accumulated soluble sugars in both shoots and roots. At 100 mM NaCl, Oro 9 showed the highest shoot soluble sugar content, whereas Mirasol alone showed the highest content in both shoots and roots. Proline was another solute that accumulates under stress conditions. Pinto displayed the lowest shoot proline content under saline conditions whereas Ludo had the highest. Proline content of root was also increased by NaCl. Flamme displayed the highest root proline content, whereas Oro 9 showed the lowest one. Root volume and shoot biomass were positively correlated (r=0.63) but total soluble sugars content and NaCl tolerance were negatively correlated (r =- 0.94).

It was concluded that soluble sugars could be a suitable criteria for screening plants for higher saline constraints (100 mM NaCl) with root volume and soluble sugars could be used for screening for lower salt conditions.