In the forest succession intermediate and climax tree species usually exhibit slow growth. The aim of this study was to investigate the biomass accumulation and photosynthetic traits in young S. macrophylla plants subjected to two light environments (1-open field and 2- natural shade). We investigated growth, biomass gain, chlorophyll contents and leaf gas exchange. In open field treatment, the increase photosynthetic performance reflected on the biomass accumulation of the plants, mainly due to the higher growth of the root system and stem diameter. This result happened due to the best use of photosynthetically active radiation, verified by increases in electron transport rate and quantum yield in plants grown in sunlight. This effect favors the carboxylation that was additionally induced by increased leaf gas exchange. On the other hand, the acclimation in the shade exposed seedlings was demonstrated by an increase in leaf area ratio and specific leaf area. We conclude that S. macrophylla seedlings showed physiological plasticity under high or low irradiance. But, above all, when exposed to high irradiance carbon, gain is optimized.
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