Growth and contents of organic and inorganic solutes in amaranth under salt stress

ABSTRACT Amaranthus cruentus L. is a forage species, with grains that exhibit excellent nutritional characteristics, being the 'BRS Alegria' the first cultivar recommended for cultivation in Brazil. This study aimed at evaluating the effect of salt stress on the growth and concentrations of organic and inorganic solutes in Amaranthus cruentus L. ('BRS Alegria' cultivar). Height, stem diameter, number of leaves, leaf, stem and root dry mass, leaf area, relative water content and membrane integrity percentage, as well as soluble carbohydrate, free amino acid, soluble protein, free proline, Na+, Cl- and K+ contents, were evaluated in different plant organs. Salinity significantly reduced the biomass yield and leaf area from the treatment with 25 mM of NaCl, indicating that the 'BRS Alegria' cultivar is sensitive to salt stress. Soluble carbohydrates in the leaves decreased by 59 %, while the other organic solutes showed no substantial increases. These results, coupled with the reduction in the relative water content and membrane integrity, suggest a low ability of this cultivar to adjust osmotically under salt stress. The K+/Na+ ratio abruptly decreased in 25 mM of NaCl, suggesting an ionic imbalance, which may partially explain the salt-induced growth reduction.