Morphological and anatomical changes of Salicornia roots are associated with different salinity and nutrients conditions in contrasting genotypes

Soil salinity induces morphological and anatomical changes in the roots and shoots of halophytic plants. These variations may be associated with external nutrient factors, including minerals. In this study, we treated the halophyte Salicornia (Amarantheceae) sometimes called sea beans or marsh samphire, with NO3- (0 mM, 6 mM, and 18 mM), NH4+ (0 mM, 1 mM and 3 mM), and NaCl (0 mM, 200 mM and 800 mM). The root characteristics of the two contrasting Salicornia genotypes, Qom (susceptible) and Helleh (tolerant) were then studied using light and epifluorescence microscopy and scanning electron microscopy. An anatomical study showed that salinity increased the diameter of the xylem cell wall. It also promoted fiber network development in the Helleh and the Qom genotypes leading to lower root and shoot biomass formation. In contrast, increased NH4+ or NO3+ and salinity enhanced root biomass formation and longer root length. Combined NH4+ or NO3+ and salinity were more positively associated with endoderm lignification, increased parenchyma diameter, and the large to small ratio of parenchyma of the stele indicating that a significant root structural plasticity underlies the adaptation mechanism of the salt tolerance in different Salicornia genotypes. In light of our results, we recommend paying more attention to genotype-dependent nutrition application under salinity and promoting saline agriculture.