Effect of NaCl and nitrogen availability on growth and photosynthesis of seedlings of a mangrove species, Kandelia candel (L.) Druce

The growth, photosynthetic gas exchange, leaf stable carbonisotope ratio (δ13C), osmotic potential (Ψs), and sodium (Na) and potassium (K) contents were measured in seedlings of a mangrove species, Kandelia candel (L.) Druce, grown under combinations of two kinds of nitrogen availability, high and low nitrogen (0.1 and 0.01 mmol/L NH4NO3), and three NaCl treatments, low, medium, and high salinity (85, 250, and 430 mmol/L NaCl). The objectives of this study were to investigate the responses of these parameters to salinity during growth and to evaluate whether nitrogen availability alters these responses. The accumulation of biomass, shoot elongation, photosynthetic rate, stomatal conductance, leaf Ψs, and leaf K contents were found to decrease with increasing NaCl. In contrast, leaf δ13C value and Na content increase with increasing NaCl. An increase in N availability significantly increased photosynthetic rates and leaf biomass, but lowered root and leaf Ψs of seedlings. In contrast, the amount of Na and K accumulation in roots and leaves was not affected by nitrogen availability.