Osmotic adjustment traits of Suaeda physophora, Haloxylon ammodendron and Haloxylon persicum in field or controlled conditions

The osmotic adjustment traits of Suaeda physophora (euhalophyte), Haloxylon ammodendron (xero-halophyte) and Haloxylon persicum (xerophyte) were investigated both in field and under controlled conditions. The results showed that percentage of inorganic solutes in total solutes was over 90%, while the estimated contribution of Na+ to Ψs was over 50% for the two halophytic species, in field condition. The percentages of inorganic solutes and organic solutes were 66% and 34%, respectively, and the estimated contribution of Na+ to Ψs was less than 18%, while the estimated contribution of soluble sugars to Ψs was over 20% in H. persicum, in field condition. The estimated contribution of proline to Ψs was less than 0.2% for all species both in field and under salt stress in a greenhouse experiment. The estimated contribution of NO3− to Ψs was less than 4% for all species in field condition. In greenhouse experiment, the concentration of NO3− was higher under various NaCl treatments than that in control condition for S. physophora; the estimated contribution of NO3− to Ψs was over 7% in S. physophora, and it was higher than that in other species at various treatments. In conclusion, inorganic ions especially Na+ were more important in osmoregulation for S. physophora and H. ammodendron to adapt to saline and arid environment, while organic solutes, especially soluble sugars played more important role in drought adaptation in the xerophyte, H. persicum. Proline did not play an important role in osmoregulation for all species both in field and controlled conditions. NO3− played more important role in osmoregulation in S. physophora and H. ammodendron cultured in full-strength Hoagland's nutrient solution under NaCl treatments compared with that growing in saline soils in field condition.