Salt Tolerance in the Succulent, Coastal Halophyte,Sarcocornia natalensis

Abstract

The effects of 0, 50, 100, 200, 300, 400 and 500 mol m'3 NaCl on growth and ion accumulation in the succulent, coastal halophyte Sarcocornia natalensis (Bunge ex Ung.-Sternb.) A. J. Scott were investigated. Increase in salinity from 0 to 300 mol m-3 NaCl stimulated production of fresh, dry, and organic dry mass, increased succulence and shifted resource allocation from roots to shoots. Growth was optimal at 300 mol m-3 and decreased with further increase in salinity. Water contributed to a large proportion of the increase in fresh mass. Inorganic ions, especially Na+ and CI, contributed substantially to the dry mass. At 300 mol m3 NaCl inorganic ions contributed to 37% of total dry mass and NaCl concentration in the shoots was 482 mol m-3. Expressed sap osmotic potentials decreased from — 2-10 to — 3-95 MPa as salinity increased from 0 to 300 mol m-3 NaCl. Massive accumulation of inorganic ions, especially Na+ and CP, accounted for 86% of the osmotic adjustment at 300 mol m 3 NaCl. Salinity treatments decreased the concentrations of K+ in shoots. Plant Na + :K+ ratios increased steadily with salinity and reached a maximum of 16-6 at 400 mol m ~3 NaCl. It is suggested that the exceptional salt tolerance of S. natalensis is achieved by massive inorganic ion accumulation which provides sufficient solutes for osmoregulation, increased water flux and turgor-induced growth.