The salt tolerances and initial growth of Kandelia candel and Rhizophora stylosa of mangrove plants were examined in different salinity conditions. The natural growth of K. candel and R. stylosa seedlings in the Oura and Kesaji Rivers, the effects of a treatment of quick change from fresh water to saline water, and the recovery experiment of nutrient deficiency were researched.
The growth inhibition occurred in 1.8% sodium chloride treatment, both in K. candel and R. stylosa seedlings. An increase in chlorophylls content and leaf thickness appeared in saline treatments. This shows a character of regulator halophyte. The result suggests that appropriate salinity is one of the important factors of both mangrove species. In natural seedlings, cation concentrations were similar to that of cultivated seedlings grown in 1.8% salinity. This indicates that the cation concentration analyzed in this experiment is not a limiting factor for their salt tolerance. Nutrient deficiency appeared only in the cultivated condition. By the spraying of a urea solution, the seedling can recover its original good condition. Hence, it suggests that ammonium form ion as a nitrogen resources is a very important factor for their growth.