Actavia 0 OLIVEIRA, M.F. MARENCO, R.A. 2019 2019-1-30 137-146 Climate models predict an increase in atmospheric CO₂ concentration and prolonged droughts in some parts of the Amazon, but the effect of elevated CO₂ is still unknown. Two experiments (ambient CO₂ ‒ 400 ppm and elevated CO₂ ‒ 700 ppm) were conducted to assess the effect of drought (soil at 50% field capacity) on physiological parameters of Carapa. At ambient CO₂ concentration, light-saturated net photosynthetic rate (P_Nsat) was reduced by 33.5% and stomatal conductance (g_s) by 46.4% under drought, but the effect of drought on P_Nsat and g_s was nullified at elevated CO₂. Total plant biomass and leaf area production were also reduced (42‒47%) by drought. By changing leaf traits, Carapa is able to endure drought, as the consumptive use of water was reduced under drought (32‒40%). The improvement of P_Nsat under elevated CO₂ and water stress and the leaf plasticity of Carapa broaden our understanding of the physiology of Amazonian trees. 1 57