GROWTH, WATER AND ION RELATIONSHIPS IN THE COASTAL HALOPHYTES TRIGLOCHIN BULBOSA AND T-STRIATA

The effects of salinity on growth, water and ionic relations in the mo nocotyledonous halophytes, Triglochin bulbosa and T. striata were inve stigated in hydroponic culture. Both species were subjected to salinit ies of 0, 50, 100, 200 and 400 mol m(-3) NaCl for 9 weeks. There was n o significant growth stimulation at salinities less than 200 mol m(-3) NaCl, while further increase to 400 mol m(-3) NaCl reduced growth in both species. With increase in substrate salinity from 0 to 400 mol m( -3) NaCl, shoot and root concentrations of Na+ and Cl- increased, thos e of K+ decreased, and Na+/K+ ratios increased in both species. Sodium interacted with Ca2+ and Mg2+ resulting in decreased concentrations o f these ions in shoots of both species. At 200 mol m(-3) NaCl, inorgan ic ions in shoots contributed to 72% of the osmotic adjustment in T. b ulbosa and to 83% in T. striata, while NaCl concentrations were 209 an d 372 mol m(-3) respectively. Both species accumulated proline, which at 400 mol m(-3) NaCl increased by about 200% in shoots and 500% in ro ots compared to non-saline controls. The significance of the interacti ve effects of Na+ with other ions, as well as the role of proline accu mulation in osmoregulation, are discussed in relation to salt toleranc e.