Physiological and metabolic responses of the Amazonian Açaí palm (Euterpe oleracea) to elevated CO2

Elevated CO₂ boosts the growth of açaí plants mainly through increased carbon assimilation and starch accumulation, however, there are signs of acclimation by sugar sensing mechanisms. Açaí (Euterpe oleracea) is an important sustainable crop in the Amazon region, used as a food supplement and widely consumed locally and exported globally. This study aimed to investigate the physiological and metabolic responses of açaí to elevated atmospheric CO2, focusing on non-structural carbohydrate dynamics. Juvenile plants grew in open-top chambers under ambient (~ 380 ppm) and elevated (~ 760 ppm) CO2 levels for 90 days, carbon assimilation, stomatal conductance, transpiration, growth, dry mass, and non-structural carbohydrate content (starch, sucrose, glucose, fructose, raffinose, and myo-inositol) were measured. Elevated CO2 significantly increased carbon assimilation, particularly in the second leaf, while reducing stomatal conductance and transpiration. Starch accumulation in leaves increased by 180%, and overall dry mass was higher, although the area of the first leaf decreased. Non-structural carbohydrate levels varied among organs, with roots showing the lowest levels. These findings suggest that elevated CO2 can promote growth in juvenile açaí plant due to high carbohydrate (starch) accumulation. However, signs of acclimation were observed over development, with declines in photosynthesis and relative growth rate. The pattern of carbohydrate metabolism, especially starch accumulation and slight raffinose transient decay, indicates that acclimation may involve sugar-sensing mechanisms.