NaCl stimulates growth and alleviates drought stress in the salt-secreting xerophyte Reaumuria soongorica

Abstract

Reaumuria soongorica, a salt-secreting xerophytic shrub, is a dominant species in arid desert regions of northwest China. To investigate whether NaCl could stimulate the growth and alleviate drought stress in R. soongorica, the seedlings were treated with a range of different concentrations of 0–1.17 g kg−1 NaCl, and also were withheld water for drought stress under without or supplementary 0.59 g kg-1 NaCl. The results showed that 0.59 g kg-1 NaCl (moderate NaCl) significantly stimulated the growth of R. soongorica, and also effectively alleviated deleterious impacts of drought stress on its growth and leaf morphological structure. Further analysis showed that moderate NaCl significantly improved photosynthetic capacity and mitigated light suppression of drought stress on photosystem II in R. soongorica, concomitantly, decreased osmotic potential, enlarged turgor pressure as well as increased the relative water content in leaves under drought stress. Furthermore, moderate NaCl induced an obvious increase of Na+ accumulation in tissues of R. soongorica, which resulted in a significant increase of the contribution of Na+ to leaf osmotic potential from13 to 22% under drought stress. Additionally, moderate NaCl also promoted Na+ secretion via salt glands of leaf. These results suggest that the positive roles of NaCl on the growth and drought resistance of R. soongorica is due to the increase of Na+ accumulating in leaf tissues, facilitating plant to maintain higher photosynthetic activity and better water status in arid environment, simultaneously, salt secretion of salt glands protects plant from excess Na+ toxicity.