The photosynthesis and chlorophyll a fluorescence in seedlings of Kandelia candel (L.) Druce grown under different nitrogen and NaCl controls

Kandelia candel (L.) Druce is the dominant mangrove species on the west coast of northern Taiwan, We have measured the net photosynthetic rate (PN) and chlorophyll (Chl) a fluorescence of seedlings grown at combinations of two nitrogen (0.01 and 0.1 mM) and two NaCl (250 and 430 mM NaCl) controls. With the same nitrogen level, seedlings grown at higher salinity (HS) had a significantly lower PN and stomatal conductance (g(s)) than those at lower salinity (LS). An increase in nitrogen availability significantly elevated P-N and g(s) of the LS-grown seedlings. Compared to dark adapted leaves, the maximum quantum yield of photosystem 2 (PS2) (F-v/F-m) of leaves exposed to PFDs of 1200 and 1600 mu mol m(-2) s(-1) for 2 h was significantly reduced. The degree of F-v/F-m reduction differed among leaves of the four types of treated plants. Chl fluorescence quenching analysis revealed differences among the examined plants in coefficients of non-photochemical and photochemical quenching.