Study on the salt and drought tolerance of Suaeda salsa and Kalanchoe claigremontiana under iso-osmotic salt and water stress

Seedlings of Suaeda salsa and Kalanchoe claigremontiana grown in plastic pots were treated with ( I) Hoagland's nutrient Solution, (2) 100 mM NaCl, (3) 50 mM NaCl+PEG (M(W) 6000) iso-osmotic to 50 mM NaCl, (4) PEG iso-osmotic to 100 mM NaCl. After 2 weeks, the plant fresh and dry weight, organic and inorganic osmotica, osmotic adjustment ability, subcelluar distribution of Na(+) and Cl(-), and the activities of tonoplast H(+)-ATPase and H(+)-PPase were determined. Results found that euhalophyte S. salsa grew best with 100 mM NaCl, but worst with iso-osmotic PEG and died after 6 days. However, the growth of K. claigremontiana was not significantly inhibited by PEG iso-osmotic to 100 mM NaCl, but dramatically inhibited by 100 mM NaCl and died after 8 days. The subcellular analysis of Na(+) and Cl(-) in fully mature leaves revealed that & salsa retained Na(+) and Cl(-) in the vacuoles, while Na(+) and Cl(-) of K. claigremontiana was mainly distributed in the cytoplasm. The analysis of tonoplast H(+)-ATPase activity and H(+)-PPase hydrolysis activity demonstrated that the enzyme activities were much more prompted by NaCl in S. salsa than in K. claigremontiana, which was closely related to the salt inclusion capacity in S. salsa. The results pointed out that S. salsa was salt-tolerant and drought-tolerant, only when the low water potential of the latter was caused by high Na(+) and Cl(-) concentration. (C) 2003 Elsevier Ireland Ltd. All rights reserved.