Aumento da concentração de CO2 e adição de fósforo nos fluxos de carbono e energia do processo fotossintético de plântulas de Inga edulis Mart. no sub-bosque da Amazônia Central

Abstract

The increase in the concentration of carbon dioxide (CO2) in the atmosphere is one of the main factors that drive climate change, with CO2 also being the primary substrate for plants photosynthesis. At the current CO2 concentration, the photosynthesis of most plants is not saturated, suggesting that they can benefit from this increase. However, the photosynthetic response can be limited by other factors, such as the availability of nutrients. In general, tropical forests are regions with low concentrations of phosphorus (P) in the soil, and the effect of increasing atmospheric CO2 can be limited by this nutrient. Due to the importance of the Amazon Forest as a large CO2 sink, this study aimed to investigate how the photosynthetic parameters of seedlings of Inga edulis, an Amazon native species, respond to the elevation in CO2 (eCO2) and the addition of P in an understory environment. The seedlings were grown in chambers with ambient (aCO2 - 500 ppm) and high (eCO2 - 700 ppm) CO2, in pots either fertilized or non-fertilized with P, for ten months in the understory of Central Amazonia. To evaluate the treatments effects on the photochemical and biochemical parameters of photosynthesis, measurements of gas exchange and chlorophyll α fluorescence were performed. The results showed that seedlings grown in eCO2 increased the light use efficiency in photosynthesis and had an increase in assimilation rates. Seedlings that grew in non-fertilized soils may be adapted to the low P available, as they manage to maintain their photochemical and biochemical rates, and the addition of P had no significant interaction with eCO2. These results showed that the stimulation of the photosynthetic process promoted by eCO2 was not limited by P, and that the addition of P had no effect on the photosynthetic response of the studied plants.