Moderate Soil Salinity Alleviates the Impacts of Drought on Growth and Water Status of Plants

Abstract Drought and soil salinity are the main environmental stress factors affecting plant growth and development. A certain appropriate concentration of NaCl in the soil has been suggested to show a beneficial effect on halophyte and xerophyte growth, while drought could cause severe damage to plants. Thus, under drought conditions, whether the moderate soil salinity could still stimulate all plant growth and productivity is curious. In this study, three plants with different salt tolerance, including arrowleaf saltbush (Atriplex tr-iangularis Willd.), cotton (Gossypium hirsutum L.) and soybean [Glycine max (Linn.) Merr.], were sown in soils containing different concentrations of NaCl and exposed to drought and non-drought conditions for 30 days. The shoot biomass, water potential, osmotic potential, Na+ and K+ concentrations in seedlings were measured. Both drought and salt stress could inhibit the growth of arrowleaf saltbush, cotton and soybean, but the decreases in plant height and shoot biomass under drought conditions were attenuated with the increase of NaCl concentration. The Na+ concentration in the leaves subjected to combined drought and salt stresses was significantly higher than that in leaves subjected only to drought stress. Meanwhile, the osmotic potential of the leaves was significantly lower in the former than the latter, and the RWC and cell turgor pressure in the leaves were significantly higher in the former than the latter. Our results prove that the appropriate soil salinity could alleviate the detrimental effects of drought stress on the water status and plant growth, no matter they are salt-tolerant or salt-sensitive plants.