Contrasting Effects of NaCl and NaHCO3 Stresses on Seed Germination, Seedling Growth, Photosynthesis, and Osmoregulators of the Common Bean (Phaseolus vulgaris L.)

The common bean (Phaseolus vulgaris L.), the most important food legume for human nutrition globally, contributes greatly to the improvement of soil fertility in semi-dry lands where most of the soil is already salinized or alkalized, such as in the Songnen Plain of China. In this study, we investigated the effects of salt stress (neutral and alkaline) on the salt-tolerant common bean. Seed germination, seedling growth, photosynthesis, and osmotic adjustment were assessed. Neutral and alkaline salt growth environments were simulated using NaCl and NaHCO3, respectively. The results indicated that at >= 60 mmol center dot L-1, both NaCl and NaHCO3 caused significant delays in seedling emergence and decreased seedling emergence rates. NaHCO3 stress suppressed seedling survival regardless of concentration; however, only NaCl concentrations >60 mmol center dot L-1 had the same effect. Alkaline salt stress remarkably suppressed photosynthesis and seedling establishment. The common bean compensated for the increase in inorganic anion concentration (influx of Na+) by synthesizing more organic acids and soluble sugars. This adaptive mechanism enabled the common bean to balance the large inflow of cations for maintaining a stable cell pH environment under alkaline salt stress.