Na⁺ and/or Cl⁻ Toxicities Determine Salt Sensitivity in Soybean (<i>Glycine max</i> (L.) <i>Merr.</i>), Mungbean (<i>Vigna radiata</i> (L.) R. Wilczek), Cowpea (<i>Vigna unguiculata</i> (L.) <i>Walp.</i>), and Common Bean (<i>Phaseolus vulgaris</i> L.)

• Main Authors: Ly Thi Thanh Le, Lukasz Kotula, Kadambot H.M. Siddique, Timothy D. Colmer
• Format: Article
• Language: English
• Published: MDPI AG 2021-02-01
• Series: International Journal of Molecular Sciences
• Subjects: salinity stress; specific ion stress; osmotic stress; growth responses; photosynthesis responses; ion “exclusion”
• Online Access: https://www.mdpi.com/1422-0067/22/4/1909
• ISSN: 1661-6596; 1422-0067

Grain legumes are important crops, but they are salt sensitive. This research dissected the responses of four (sub)tropical grain legumes to ionic components (Na⁺ and/or Cl⁻) of salt stress. Soybean, mungbean, cowpea, and common bean were subjected to NaCl, Na⁺ salts (without Cl⁻), Cl⁻ salts (without Na⁺), and a “high cation” negative control for 57 days. Growth, leaf gas exchange, and tissue ion concentrations were assessed at different growing stages. For soybean, NaCl and Na⁺ salts impaired seed dry mass (30% of control), more so than Cl⁻ salts (60% of control). All treatments impaired mungbean growth, with NaCl and Cl⁻ salt treatments affecting seed dry mass the most (2% of control). For cowpea, NaCl had the greatest adverse impact on seed dry mass (20% of control), while Na⁺ salts and Cl⁻ salts had similar intermediate effects (~45% of control). For common bean, NaCl had the greatest adverse effect on seed dry mass (4% of control), while Na⁺ salts and Cl⁻ salts impaired seed dry mass to a lesser extent (~45% of control). NaCl and Na⁺ salts (without Cl⁻) affected the photosynthesis (<i>P_n</i>) of soybean more than Cl⁻ salts (without Na⁺) (50% of control), while the reverse was true for mungbean. Na⁺ salts (without Cl⁻), Cl⁻ salts (without Na⁺), and NaCl had similar adverse effects on <i>P_n</i> of cowpea and common bean (~70% of control). In conclusion, salt sensitivity is predominantly determined by Na⁺ toxicity in soybean, Cl⁻ toxicity in mungbean, and both Na⁺ and Cl⁻ toxicity in cowpea and common bean.