Evidence of non-structural carbohydrates-mediated response to flooding and salinity in Limonium narbonense and Salicornia fruticosa

In plant species, the effects of flooding and salinity are commonly studied under controlled conditions in order to understand their acclimation to environmental stresses. Nevertheless, each stress is usually considered separately and laboratory conditions cannot encompass the complexity of the natural ecosystem, often concealing the true plant response. Our work aimed therefore at studying plant responses to flooding and salinity in the field, focusing on two target halophytes and on their reserve organs, i.e. rhizomes of Limonium narbonense and woody stems of Salicornia fruticosa. The physiological response was investigated measuring non-structural carbohydrates (NSCs) and amino acids (AA), and considering the two growing stages of the species, i.e. the growing and the seed ripening seasons. L. narbonense rhizomes showed a larger amount of starch and all measured osmolytes, i.e. NSCs, AA and proline, compared to S. fruticosa woody stem, where plant response to environmental stress seemed linked chiefly to soluble NSCs. The effects on soluble NSCs were mainly driven by flooding and were influenced by salinity only at low flooding stress. The two species showed a contrasting strategy against flooding and salinity based on soluble NSCs, and with a more intense response during the seed ripening season. Large amount of AA, proline in particular, suggested the involvement of these osmolytes in the salinity tolerance in L. narbonense, regardless to the intensity of the stress.