Comparison of Growth and Ion Absorption with Compatible Solute Accumulation of Three Wild Vigna Species under Salt Stress

Abstract

The genus Vigna contains various economically important species such as cowpea and mung bean. The growth of three wild Vigna species—V. vexillata, V. luteola, and V. marina—was examined with cation and anion absorption and translocation as well as compatible solute accumulation, such as sugar and proline concentrations, that are considered to relate to osmoregulation against salt stress with 100 mM NaCl treatment. Vigna plants’ specific characteristics of Na⁺ absorption and translocation of salt-tolerant accessions as Na⁺ excluders or includers became even clearer when the accumulation of Na⁺ content in each part was compared. It was also clarified that the extent of the increase in Cl^- content was larger than that of Na⁺, especially in the root under salt stress, although the growth of Vigna plants was impacted more by the change in Na⁺ than that in Cl^-. Furthermore, the increase in sucrose, glucose, fructose, and proline in the plant body was considered to enable salt-tolerant Vigna plants to retain their physiological functions through osmotic adjustment under salt stress. The extent of increase in each type of sugar and proline was different between the species.