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.

摘要 尾穗苋（Amaranthus cruentus L.）是一种饲用作物，其籽粒具有优异的营养特性，其中‘BRS Alegria’是巴西首个推荐种植的尾穗苋品种。本研究以尾穗苋‘BRS Alegria’品种为材料，旨在评估盐胁迫对其生长以及有机、无机溶质含量的影响。研究测定了不同植株器官的株高、茎粗、叶片数、叶干重、茎干重、根干重、叶面积、相对含水量、细胞膜完整性百分比，以及可溶性糖、游离氨基酸、可溶性蛋白、游离脯氨酸、钠离子（Na+）、氯离子（Cl-）和钾离子（K+）的含量。当NaCl浓度为25 mM时，盐胁迫即显著降低了植株生物量产量与叶面积，表明‘BRS Alegria’品种对盐胁迫敏感。叶片中的可溶性糖含量下降了59%，而其余有机溶质未出现显著升高。结合相对含水量与细胞膜完整性的下降，上述结果表明该品种在盐胁迫下的渗透调节能力较弱。在25 mM NaCl处理中，钾钠比（K+/Na+）骤降，提示存在离子失衡，这可部分解释盐胁迫导致的植株生长受抑现象。