Physiological and biochemical responses to salt stress in the mangrove, Bruguiera gymnorrhiza

Physiological and biochemical responses induced by salt stress were studied in laboratory-grown young plants of the mangrove, Bruguiera gymnorrhiza. T he growth rates and leaf areas were highest in the culture with 125 mM NaCl . Transpiration rates showed a diel periodicity when the plants were placed in water, but the oscillatory cycles disappeared for plants placed in high er salt concentration (250-500 mM NaCl). The transfer of plants from water to any higher salinity resulted in an immediate increase in transpiration. Both the steady-state rates of transpiration and light-saturated rates of p hotosynthesis decreased as the salt concentration was increased. The activi ties of the antioxidant enzymes, superoxide dismutase (SOD) and catalase, s howed an immediate increase after the plants were transferred from water to high salinity, reaching in 10 days five and eight times those of initial a ctivities, respectively. The activities of these two enzymes were not affec ted by salt concentrations up to 1000 mM NaCl, twice that of seawater. (C) 2000 Elsevier Science B.V. All rights reserved.