Efeito do aumento da concentração de CO2 ambiente na eficiência fotossintética e proteção oxidativa em plantas de arroz submetidas ao déficit hídrico

Abstract

Water scarcity and predicted climate changes, such as increased CO2 atmospheric concentrations, may affect the growth and productivity of cultivated plants and generating varied responses, including changes morphological, physiological, biochemical and molecular. Water deficit negatively affects photosynthesis, whereas CO2 increase can benefit plants and attenuate photo-oxidative damage, especially in C3 metabolism species. However, precise responses to the combination of high CO2 and water deficit are still poorly understood and cannot be extrapolated directly from the effects of each of these separately applied agents. This work aimed to understand the beneficial effects of increasing CO2 on the mechanisms of resistance to drought in rice plants. The cv. San Francisco was cultivated in a climatic chamber, under controlled conditions of temperature, relative humidity and CO2 concentration, and submitted to two moisture levels in the substrate (well-watered and water deficit) and two concentrations of CO2 (environment and elevated), in a 2x2 factorial scheme. The study found results that confirm the beneficial effects of increased CO2 on plants and an attenuating effect on water deficit in rice plants. This effect is mainly associated to the maintenance of the water state, greater photosynthetic efficiency and the regulation of light absorption and antioxidatives processes. In addition, it was possible to demonstrate the complexity of the photorespiration process, which can be regulated by other alternative routes, influencing the loss or recovery of carbon during the sensitivity or resistance to water deficit reactions.