Uptake of inorganic ions and compatible solutes in cultured mangrove cellsduring salt stress

Callus of the mangrove plant, Sonneratia alba J. Smith, established from pi stils of flower buds were cultured on solid Murashige and Skoog medium supp lemented with 0 to 500 mM NaCl, Maximum growth was observed with 50 mM NaCl , and net growth of callus occurred for concentrations up to 200 mM NaCl. A t 500 mM NaCl, growth of callus was completely inhibited, although a part o f the tissue was still alive after 30 d. Cellular levels of Na+ and Cl- wer e greatly increased bl the treatment with NaCl. Uptake of K+ was also enhan ced and was accompanied by increasing levels of Na+ and Cl- so that the Na/K+ ratio was almost constant (4.1-4.2) in callus grown with 50-200 mM NaCl . Levels of Mg2+ and Ca2+ were not changed significantly with 50-200 mM NaC l, whereas levels of free NH4+, NO3- and SO42- ions, which are convertible to organic compounds, were lowest in callus grown with 50 mM NaCl. The rate of conversion of (NH4+)-N-15 into macromolecules during 30 d culture with 0-100 mM NaCl did not vary greatly, but 200 mM NaCl reduced the biosynthesi s of macromolecules from this ion. The highest rate of conversion of (NO3-) -N-15 into macromolecules was observed at 50 mM NaCl. Identification of com patible solutes with NMR-spectroscopy indicated that mannitol is the compat ible solute for intact plants of Sonneratia alba. hut no accumulation of ma nnitol was found in calluses. not even in those grown at high concentration s of NaCl.