Photosynthesis of a tropical canopy tree, Ceiba pentandra, in a lowland forest in Panama.

Diel (24 h) courses of CO(2) and water-vapor exchange of Ceiba pentandra (L.) Gaertn. (Bombacaceae) were studied under natural tropical conditions in the semi-evergreen moist forest of Barro Colorado Island, Panama. Measurements were conducted from early February 1991 (dry season), shortly after new leaves emerged, until mid-October 1991 (wet season), when leaves were shed. Rates of net CO(2) uptake were significantly higher in the dry season than in the wet season, and showed a linear decrease with leaf age. Leaf nitrogen concentrations and contents also decreased with age. Our estimate of annual carbon gain (2640 g CO(2) m(-2) year(-1) or 21 g CO(2) g(DW) (-1) year(-1)) is considerably higher than estimates available for temperate forest trees.