Despite several studies having tried to correlate coffee growth periodicity with environmental factors, the relations found were, ordinarily, circumstantial. Control of the beginning, maintenance and the end of active and quiescent growth phases seem to be really complex and not very well understood (Barros et al. 1997). Nevertheless, according to the same authors there is a strict parallelism between reduction in stomatal conductance and decrease in growth rate of coffee plants at lower temperatures during the Brazilian winter. It is important to stress that in winter, a decrease of the photochemical efficiency of photosystem