Influence of climate seasonality on the accumulation of carbohydrates and cell wall polymers in organs of three tree species of a restinga forest

Abstract

Due to the great variety of environments in which tropical forests are distributed, the occurrence of tree species is conditioned to places that present favorable environmental characteristics. If the species does not show considerable phenotypic plasticity, its distribution limits will be reduced. However, given the predictions of climate change, environments may undergo relatively abrupt variations and species will have to respond quickly to new conditions. To investigate how this can influence the dynamics of carbon compounds in plant tissues, studies on environmental gradients, combined with seasonal analysis of climate, are a powerful tool. The objective of this study was to evaluate the seasonal variation (dry period-rainy period) in the concentrations of non-structural carbohydrates and cell wall polymers in stems, branches and leaves of tree species distributed in zones of a restinga (sandbank) forest. For this, we carried out collections in the dry season (winter) and in the rainy season (summer) in populations of Eugenia bahiensis , Guarea macrophylla and Calophyllum brasiliense . Starch and hemicellulose concentrations were lower in the rainy season. However, the reduction in hemicellulose concentrations was the most uniform result. Probably, these molecules were used as energy source in the reproductive and growth demands of the species. Due to a long period of drought, the other non-structural carbohydrates (glucose, fructose and sucrose) did not show significant variations. Small variations in cellulose and lignin contents were attributed to fluctuations in the concentration of other molecules. In general, it was assumed that the low rainfall recorded during the study interfered with the expected seasonal responses. This phenomenon may have reduced the differences in soil moisture between forest zones.