PHOTOSYNTHESIS, STOMATAL CONDUCTANCE AND PRODUCTIVITY OF Eucalyptus CLONES UNDER DIFFERENT SOIL AND CLIMATIC CONDITIONS

The objective of this study was to evaluate photosynthesis rate, stomatal conductance and productivity of Eucalyptus clones in two different sites; one in Eunapolis, southern Bahia with well distributed rainfall throughout the year (wet area) and another on Salto da Divisa, east of Minas Gerais, with rainfall concentrated over the hot months of the year (dry area). Four different clones were examined, measurements of plants growth were performed by means of inventory and the photosynthetic parameters were measured with IRGA (Infrared Gas Analyser). Within each area, there is difference between clones only in the wet area for the variable volume. The average productivity of the clones in the wet area was 3.3 times higher comparing to the dry area. All clones in wet area decreased stomatal conductance in response to increase in vapor pressure deficit, decreasing 0.16 mol m(2) s(-1) to each 1kPa increase in VPD and the maximum photosynthetic rate ranging from 12.5 to 16.4 mu mol m(2) s(-1) in this area. The comparison between clones within each area resulted in a significant difference in the wet area, with the clone A reaching maximum photosynthesis higher than others. In the dry area, there was no correlation between stomatal conductance and VPD, and there was no difference in photosynthesis between the clones, ranging from 1.2 to 3.4 mu mol m(2) s(-1). A linear relationship was observed between the maximum photosynthesis and clones productivity, suggesting that photosynthetic rate was one of the factors responsible for the increased Eucalyptus productivity of the wet area.