Can Enhanced CO2 Help to Mitigate the Global Warming Impact in the Tropical Coffee Plant?

AbstractCoffee crop has been predicted to become threatened by future climate changes and global warming conditions. Still, the effective biological impact of enhanced air [CO2] and temperature on this plant remain to be fully elucidated, as only recently this subject has begun to be studied for coffee (1,2). Therefore, this work aims at linking coffee physiological and biochemical responses to such environmental changes, using the photosynthetic metabolism as probe of the plant tolerance. Potted plants from Coffea arabica L. cv. Icatu (an important cultivated genotype) were grown for 1 year under controlled conditions (temperature, RH, irradiance, photoperiod), at 380 or 700μLCO2L-1 air, without nutrient, water and root space limitations (2). Temperature was then gradually increased (0.5°C/day) from 25/20°C (day/night) up to 42/34°C. Photosynthetic functioning was assessed at 25/20°C, 31/25°C, 37/30°C and 42/34°C through: leaf gas exchanges (net photosynthesis, stomatal conductance, photosynthetic capacity), fluorescence parameters (photochemical efficiency of the photosystem (PS) II), thylakoid electron transport rates involving PSI and II, activities of RuBisCO and RuB5PK. The impact on lipid components of chloroplast membranes and respiratory enzymes (NADH-MDH, PK) was also evaluated. Globally, the results showed a higher metabolic performance in the plants grown under enhanced [CO2] and to a marginal impact until 37°C, configuring a much higher tolerance to high temperature than suggested by classical works for C. arabica plants. Only at 42°C the tolerance limit was exceeded, as shown by significant impacts in most parameters (particularly at enzymes level), although the high [CO2] plants usually preserved a better performance. If available, results from a large transcriptomics approach (RNAseq) will be presented in order unravel global and integrated plant responses. Our findings showed that the enhanced growth [CO2] promoted the preservation of the photosynthetic functional status at high temperatures (37 and 42°C) in the coffee plant, what is quite relevant in a context of predicted climate changes and global warming scenarios