Effects of Salinity on the Growth and Survival of the Seedlings of Mangrove, Rhizophora stylosa

Abstract

Aims: There are contradictory views on whether mangroves are obligate halophytes or facultative halophytes. In this study, we examined :(1)if seedlings of a mangrove, Rhizophorastylosa, require NaCl for theiand (2) whether the growth response of R. stylosaseedlings under varying salinities was explained from the context of carbon economics. Methodology: Seedlings ofR. stylosawere hydroponically grown under varying salinities (0-480 mMNaCl) and their growth, mortality, photosynthetic and respiration rates were analyzed. Results:Most of the seedlings grown under NaCl -free condition died during the 34 -week culture, demonstrating their salt dependency. The best growth was accomplished under moderate salinity (240 mMNaCl) with highest stem elongation, maximum biomass gain and lowest leaf mortality. Whole -plant photosynthetic production was highest under the moderate salinity anddeclined towards high and low salinity ranges whereas wholeplant respiration did not increase towards high and low salinity ranges. The lower photosynthetic production under high salinity involved reductions in both leaf area and Original ResearchArticle