Photosynthesis and successional status of Costa Rican rain forest trees

Seven tree species from three different light environments in the wet lowland forests of Costa Rica were grown under controlled environment conditions to assess light related photosynthetic potentials. Light saturated photosynthesis rates were clearly related to light levels of the field environments. Mean saturated, net photosynthetic rates ranged from 6.8 to 11.3 to 27.7 mol m^–2 sec^–1 for plants from heavy shade, canopy light gaps and man-made clearings respectively. Light saturation of plants from clearings occurred at photosynthetic photon flux densities greater than 1000 mol m^–2 sec^–1 whereas plants from heavy shade environments became light saturated near 500 mol m^–2 sec^–1. Plants that normally occur in intermediate light environments were intermediate in light saturation levels. Mean maximum stomatal conductances ranged from 1.0 to 7.3 mm sec^–1 and followed a pattern similar to photosynthetic rates.