Salinity variation effects on photosynthetic responses of the mangrove species Rhizophora mangle L. growing in natural habitats

Abstract

This study evaluated the photosynthetic efficiency in Rhizophora mangle plants in two mangrove forests, the highest salinity (HS) area, and the lower salinity (LS) area. The CO2 assimilation rate (PN), stomatal conductance, leaf transpiration, intrinsic water-use efficiency, and chlorophyll a fluorescence L-band, IP-phase, and performance index were higher in the LS area. The instantaneous water-use efficiency, initial fluorescence, maximum fluorescence, and J-step were higher in the HS area. The plants growing in the HS area exhibited greater efficiency in electron transfer between the oxygen-evolving complex and the acceptor side of the PSII. The plants growing in the LS area exhibited greater efficiency of the reduction of the final acceptors of the PSI, an important strategy to the stress conditions. The results show that a greater variation in salinity in the LS area had the effect on PN and long-term changes in the rainfall regime may alter the vegetation community of mangrove forests.

Keywords

• energy flow; gas exchange; halophytes; jip test; salt tolerance; tropical region.