A glimpse of climate change impact on C. Arabica L. and C. canephora Pierre EX A. Froehner physiology - the combined effects of enhanced growth CO2 and temperature

At the moment, there is a total an absence of biological studies concerning the effective impact of climate changes on the coffee plant physiology, promoted by enhanced air [CO2] and global warming. Therefore, this work aims at linking coffee physiological responses to environmental changes of enhanced growth [CO2] and temperature, on genotypes from the two major producing species. Potted plants from C. arabica cv. Catucaí IPR 108 and of C. canephora cv. Conilon Clone 153 were grown under controlled conditions of temperature (25/20 ºC, day/night), irradiance (650-800 μmol m-2 s-1), RH (75%), photoperiod (12 h), and either 380 or 700 μL CO2 L-1 air for 1 year, without water, nutrient or root development restrictions. After that the temperature was increased from 25/20 ºC up to 42/34 ºC, at a rate of 0.5 ºC per day, with a 7 days stabilization temperature at 31, 37 and 42 ºC. The long-term impacts of elevated growth [CO2] and enhanced temperature on the photosynthetic functioning were assessed through leaf gas exchanges (net photosynthesis, Pn, stomatal conductance, gs, transpiration, Tr, and photosynthetic capacity, Amax), instantaneous water use efficiency (iWUE), fluorescence parameters (photochemical efficiency of the photosystem II under dark, Fv/Fm and light, Fv’/Fm’, conditions, as well as the photochemical, qP, and non-photochemical, NPQ, quenchings, and quantum yield of the linear electron transport, fe), photosynthetic pigments (chlorophyll and carotenoids) and some molecules with antioxidant role (ascorbate and α-tocopherol). The results showed that such enhanced growth [CO2] stimulates the photosynthetic functioning, without down-regulation. The photochemical functioning was barely affected until 37 ºC, but extensive impacts were found at 42 ºC, especially in IPR108. Furthermore, the enhanced [CO2] allowed the preservation of a higher functional status (e.g., Pn, Amax, Fo, Fv/Fm) at high temperatures (37 and 42 ºC), what seemed quite relevant under the predicted climate changes and global warming scenarios.