Fotossíntese, crescimento e alocação de biomassa de sumaúma (Ceiba pentandra (L.) Gaertn, Malvaceae) em resposta ao estresse hídrico e elevada concentração de CO2

Abstract

Climate models forecast prolonged droughts for some parts of the Amazon, and it isunclear how Amazonian trees will respond to water stress and to the increase in CO2 concentration. The aim of this study was to evaluate the effect of elevated CO2 and water stress on photosynthetic rates, growth and biomass production of Ceiba pentandra. The treatments were undergone under two CO2 levels (400 and 800 ppm) and two water regimes (50 and 100% of field capacity). The plants were submitted to the treatments for 138 days. Chlorophyll fluorescence, photosynthesis (maximum and potential) and stomatal conductance were measured. Radial growth, height growth, leaf area production, biomass and water use efficiency of the whole plant were also measured. In comparison to plants grown at ambient CO2 concentration, photosynthetic rates, biomass production, radial growth and water use efficiency were higher in plants submitted to elevated CO2 concentration. With respect to the water regime, there was a reduction in photosynthesis, stomatal conductance and transpiration under water stress. The CO2 enriched environment led to an increase in photosynthetic rates, but there was no acclimation of photosynthesis under elevated CO2. Plants under water stress showed a reduction in leaf area and growth rates, while they had greater water use efficiency when compared to those grown under 100% of field capacity.