Is guava phenolic metabolism influenced by elevated atmospheric CO2?

Seedlings of Psidium guajava cv. Pedro Sato were distributed into four open-top chambers: two with ambient CO2 (∼390 ppm) and two with elevated CO2 (∼780 ppm). Monthly, five individuals of each chamber were collected, separated into root, stem and leaves and immediately frozen in liquid nitrogen. Chemical parameters were analyzed to investigate how guava invests the surplus carbon. For all classes of phenolic compounds analyzed only tannins showed significant increase in plants at elevated CO2 after 90 days. There was no significant difference in dry biomass, but the leaves showed high accumulation of starch under elevated CO2. Results suggest that elevated CO2 seems to be favorable to seedlings of P. guajava, due to accumulation of starch and tannins, the latter being an important anti-herbivore substance. •Psidium guajava is an important commercial fruit tree species in Brazil.•Psidium guajava accumulated starch and tannins after 90 days under elevated CO2.•Results are in agreement to the growth–differentiation balance theory (GDB theory). Guava seedlings exposed to CO2-enriched atmosphere seem to invest the surplus carbon on accumulating non-structural carbohydrates and tannins instead growth.