Effect of long-term salinity on the growth and biomass of two non-secretors mangrove plants Rhizophora apiculata and Ceriops tagal

The present study describes the effect of long-term salinity on morphological character and biomass content of two non-secretors mangrove plants Rhizophora apiculata and Ceriops tagal. Two mangrove seedlings were grown for six months in 0%, 0.5%, 1.5%, 2.0% and 3.0% salt concentration. The growth of R. apiculata was significantly enhanced by salt with maximal stimulus at 1.5% (equal to 50% natural seawater), and this increase appeared to be attenuated by increasing the salinity concentration above 1.5%. By contrast, the growth of C. tagal thrived up to 0.5% salt concentration. Our findings, therefore, suggested that within the range of treatments used, 1.5% and 0.5%, respectively were the optimal salinity of R. apiculata and C. tagal for growth. The highest leaf area of C. tagal was obtained at 1.5% salinity concentrations and, on the other hand, R. apiculata showed much greater extent. The wet and dry weight of the two seedlings was changed in the same manner as the height of plants upon salt treatment. Our results indicated that R. apiculata was more salt tolerant than C. tagal, which may provide valuable information for mangrove rehabilitation in North Sumatra, Indonesia.