COMPATIBLE SOLUTES AND INORGANIC-IONS IN THE MANGROVE PLANT AVICENNIA-MARINA AND THEIR EFFECTS ON THE ACTIVITIES OF ENZYMES

Naturally grown two-month-old seedlings of Avicennia marina contain hi gh concentrations of Na+ and Cl-. Our NMR studies revealed an accumula tion of glycinebetaine, asparagine and stachyose in A. marina. The hig hest concentration of glycinebetaine was observed in young leaves, whi le the distribution of stachyose was restricted in stems and roots. As paragine comprised more than 96% of total free amino acids in roots an d 84% in leaves from two-year-old plants. Little or no accumulation of proline or polyols, which are proposed as compatible solutes in other plants, could be detected in A. marina. The activities of phosphofruc tokinase, pyrophosphate:fructose-6-phosphate 1-phosphotransferase, glu cose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase (deca rboxylating), phosphoenolpyruvate carboxylase and NAD:malate dehydroge nase from young leaves of A. marina were inhibited by NaCl, while the activity of fructose-1,6-bisphosphate aldolase was activated by 50-200 mM NaCl. There was little or no effect of high concentrations (up to 500 mM) of glycinebetaine on the activities of any of these enzymes. N o significant protection by glycinebetaine was detected against NaCl i nhibition of these enzymatic activities. Based on these results, possi ble mechanisms for the salt-resistance of A. marina cells are discusse d.