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The flowers of mangrove plants are pollinated by a variety of pollinators including birds, bats, and insects. This study analyzed the floral scent chemistry of mangroves on Iriomote Island (located near Taiwan) including Bruguiera gymnorrhiza (L.) Lamk. (Rhizophoraceae), Kandelia candel (L.) Druce (Rhizophoraceae), Rhizophora stylosa Griff. (Rhizophoraceae), Sonneratia alba J. Smith (Sonneratiaceae), Nypa fruticans (Thunb.) Wurmb. (Palmae), Lumnitzera racemosa Willd. (Combretaceae), Avicennia marina (Forsk.) Vierh. (Avicenniaceae or Verbenaceae), and Pemphis acidula Forst. (Lythraceae). A total of 61 chemicals (fatty acid derivatives, terpenoids, carotenoid derivatives, benzenoids, nitrogen-containing compounds, 13 unknown chemicals) were detected in the floral scents of the various species. The species displayed a distinct chemical profile ranging from only two chemicals in the floral scent of Kandelia candel to more than 25 chemicals in the floral scent of Nypa fruticans. All of the identified chemicals have been found in the floral scents of other angiosperms. The chemical profile of some species can be correlated with their floral morphology and pollinators.

Soil conditions of mangrove forests in southern Japan were found to correlate largely with zonal distributions of the species.Kandelia candel grew in soils with low salinity and low pH,Avicennia marina, Rhizophora stylosa andSonneratia alba in soils with high salinity and high pH, andBruguiera gymnorrhiza in soil with a wide range of pH but limited range of salinity.Lumnitzera racemosa colonized soil with a wide range of pH and medium salinity. Seedlings ofKandelia candel, Bruguiera gymnorrhiza andRhizophora stylosa were planted in soils with differing salinity and pH. Optimum seedling growth ofKandelia, Bruguiera andRhizophora occurred when plants were cultivated in soils similar to those of their natural habitats, suggesting that growth of mangrove species and their zonal distributions were regulated by salinity and soil pH.

Lipid compositions of mangrove trees were studied in relation to the salt-tolerance mechanism. Leaves and roots were obtained from seven mature mangrove trees on Iriomote Island, Okinawa: Bruguiera gymnorrhiza, Rhizophora stylosa, Kandelia candel, Lumnitzera racemosa, Avicennia marina, Pemphis acidula and Sonneratia alba. Lipids of mangrove leaves mainly consisted of 11 lipid classes: polar lipids, unknown (UK) 1-6, sterols, triacyl glycerols, wax ester and sterol ester (UK 3 and 4 were found to be tri-terpenoid alcohol in this study). Of these lipid classes, sterol ester was the main lipid in all species comprising 17.6-33.7% of total lipids. Analysis of the chemical structure found that the sterol esters mainly consisted of fatty acid esters of tri-terpenoid alcohols. One major tri-terpenoid alcohol was identified to be lupeol by interpretation of infrared resonance, nuclear magnetic resonance and mass spectrometry. Because of the unique anatomy of the mangrove root, lipid analyses were made separately for epidermis, cortex and innermost stele, respectively. The concentration of free tri-terpenoid alcohols showed a higher tendency in the outside part than in the inside portion of the roots, suggesting their protective roles. Relevance of lipid composition to salt tolerance was studied with propagules of K. candel and B. gymnorrhiza planted with varied salt concentrations. The proportions of free tri-terpenoids increased with salinity in both leaves and roots of K. candel, and only in roots of B. gymnorrhiza. No salt-dependent changes were noted in the phospholipid and fatty acid compositions in both species. These findings suggested that salt stress specifically modulated the terpenoid concentrations in mangroves.

Calluses initiated from leaves and seedlings of the mangrove,Bruguiera sexangula, were isolated from the original tissues and subcultured. Effects of NaCl on growth and ion content of each callus were measured. The growth rate of calluses derived from leaves (leaf callus) gradually decreased as the NaCl concentration in the medium increased, while that of calluses derived from seedlings (seedling callus) was highest in the medium containing 100 mM NaCl. Concentrations of Na and Cl in both calluses increased with increasing the NaCl concentration in the culture medium. The concentration of K of leaf calluses greatly decreased at 300 mM NaCl, while the K concentration of seedling calluses decreased only slightly and remained relatively high even in the presence of 300 mM NaCl.Transient treatment of leaf calluses with media containing high concentrations of NaCl frequently induced regeneration of adventitious tissues.