EFFECTS OF SALINITY ON THE GROWTH OF MANGROVE SEEDLINGS

Abstract

Growth analysis was done with mangrove trees, namely Bruguiera gymnorrhiza, B. parviflora and Ceriops tagal to study the establishment of seedlings. Seedlings were grown for 120 days in a glasshouse in varied NaCl salinity regimes (0, 10, 15 and 20 ppt). Bruguiera gymnorrhiza thrived up to a maximum salinity of 15 ppt with highest biomass produced at 10 ppt. Bruguiera parviflora and C. tagal, however, grew well up to 20 ppt NaCl salinity but with a reduced rate of growth. The relative growth rate in C. tagal increased by more than 90% over the control at a salinity of 10 ppt, followed by 42% in B. parviflora and 32% in B. gymnorrhiza at 15 ppt. Growth analysis showed that both net assimilation rate and leaf area ratio accounted for differences in relative growth rate in all the species studied. Bruguiera gymnorrhiza was found most sensitive to high salinity compared with the other species. Depletion of this species can be reduced by growing them in low salinity regimes for successful seedling establishment.