Effects of salt and water stresses on osmotic adjustment of Suaeda salsa seedlings

Forty-day old Suaeda salsa (L.) Pall. seedlings were treated with different concentrations of NaCl and iso-osmotic PEG solutions. The content of the main organic solutes and inorganic ions,the osmotic potential and osmotic adjustment ability of leaves were determined 10 days after treatment. The results showed that under NaCl stress,the sum of inorganic ions had a significant increase and their contribution to the calculated osmotic potential (COP) was up to 95% to 98%. The great increase of Na(+) and Cl(-) content accounted for 71% to 98% of COP, whereas the total content of organic solutes decreased slightly and thier contribution to COP was only 2% to 5%. Under water stress the organic solutes (amino acid, sugar and organic acid) were markedly increased, especially amino acid, which accounted for more than 9% of COP. The measured osmotic potential (MOP) from each treatment was always lower than the COP,which indicated that the other osmotic solutes were involved in the osmotic adjustment in S. salsa seedlings under these circumstances. The results also suggested that osmotic adjustment ability of S. salsa seedlings increased with the external salinity.