Abstract
The function of the elected pneumatophores of two mangrove species, A vicennia officinalis andSonneratia alba, was investigated in Thailand. In order to clarify that the photosynthetic reaction takes place in the pneumatophore and that the O2produced by this reaction diffuses to the root in the subsoil, the CO2exchange rate through the surface of the pneumatophore and the O2concentration in the root were measured in situ.
As a result, gross photosynthetic rates of pneumatophores ofA. officinalisandS. albawere 0.8-1.2 mgCO2/cm2/hr and 1.0-2.8 mgCO2/dm2/hr, respectively. The O2concentration in the root increased from 13.9% to 16.7% when the solar radiation increased from 0.7 calf cm2/min to 1.2 cal/cm2/min. This concentration decreased rapidly when the pneumatophore was shaded.
In conclusion, it was proved that the elected pneumatophore actually produced O2by the photosynthetic reaction and that such O2diffused to the root in the subsoil.
