Abstract
The effects of nitrate, ammonium and salinity on the growth of the mangrove, Bruguiera gymnorrhiza (L.) Lam. were investigated in two solution culture experiments over 8 months. In the first, at 100 mol m −3 NaCl, dry matter accumulation increased with an increase in added nitrogen (N) from 0 to 10 mg l −1 NO 3 −-N and from 0 to 15 mg l −1 NH 4 +-N. Thus this species assimilates both forms of inorganic N. Further increases in added N to 20 mg l −1 decreased biomass, even though tissue N concentrations increased. Trends in total leaf area, area per leaf and specific leaf area paralleled those for dry biomass. In the second, at 20 mg l −1 NH 4 +-N, the accumulation of dry matter and photosynthetic leaf area were maximal at 50 mol m −3 NaCl and declined at higher salinities up to 250 mol m −3. The data suggested that growth enhancement in response to added N occurs at low salinities. Higher salinities tend to reduce biomass, even at high levels of added N. There were significant effects of N source and concentration, as well as of salinity, on N content, biomass accumulation and photosynthetic leaf area.
Published Version
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