NaCl stimulates growth and alleviates water stress in the xerophyte Zygophyllum xanthoxylum

Zygophyllum xanthoxylum is a succulent xerophyte that is recognized as one of the most drought-resistant plants found to date. Our previous investigations have shown that the strong drought resistance of Z. xanthoxylum might be related to the accumulation the Na+ in the leaves. In this study, we further investigated the effects of NaCl on the growth and drought resistance of Z. xanthoxylum under water stress. We found that 50 mM NaCl resulted in optimal plant growth and alleviated the deleterious impacts on leaf growth of different osmotic stress levels induced by PEG 6000. The positive effects of NaCl on the drought resistance of Z. xanthoxylum were also further confirmed by soil culture experiments. Ion analysis showed that the Na+ absorption of Z. xanthoxylum was specifically induced by water stress in a non-saline medium and that the addition of 50 mM NaCl increased the leaf Na+ concentration under water stress. These findings suggest that the positive roles of NaCl in the drought resistance of Z. xanthoxylum might be due to the ability of the plant to accumulate high concentrations of Na+ in the leaves and use the Na+ as an osmoregulator to cope with water stress. ► 50 mM NaCl could stimulate growth and alleviate water stress of Zygophyllum xanthoxylum. ► Z. xanthoxylum could accumulate high concentration of Na+ in leaves. ► Na+ is used as an osmoregulator to contribute to osmotic adjustment. ► Tissue water status is improved due to the contribution of Na+ to osmotic adjustment.