Long‐term elevated air [CO₂] strengthens photosynthetic functioning and mitigates the impact of supra‐optimal temperatures in tropical Coffea arabica and C. canephora species

Abstract

The tropical coffee crop has been predicted to be threatened by future climate changes and global warming. However, the real biological effects of such changes remain unknown. Therefore, this work aims to link the physiological and biochemical responses of photosynthesis to elevated air [CO2 ] and temperature in cultivated genotypes of Coffea arabica L. (cv. Icatu and IPR108) and Coffea canephora cv. Conilon CL153. Plants were grown for ca. 10 months at 25/20°C (day/night) and 380 or 700 μl CO2 l(-1) and then subjected to temperature increase (0.5°C day(-1) ) to 42/34°C. Leaf impacts related to stomatal traits, gas exchanges, C isotope composition, fluorescence parameters, thylakoid electron transport and enzyme activities were assessed at 25/20, 31/25, 37/30 and 42/34°C. The results showed that (1) both species were remarkably heat tolerant up to 37/30°C, but at 42/34°C a threshold for irreversible nonstomatal deleterious effects was reached. Impairments were greater in C. arabica (especially in Icatu) and under normal [CO2 ]. Photosystems and thylakoid electron transport were shown to be quite heat tolerant, contrasting to the enzymes related to energy metabolism, including RuBisCO, which were the most sensitive components. (2) Significant stomatal trait modifications were promoted almost exclusively by temperature and were species dependent. Elevated [CO2 ], (3) strongly mitigated the impact of temperature on both species, particularly at 42/34°C, modifying the response to supra-optimal temperatures, (4) promoted higher water-use efficiency under moderately higher temperature (31/25°C) and (5) did not provoke photosynthetic downregulation. Instead, enhancements in [CO2 ] strengthened photosynthetic photochemical efficiency, energy use and biochemical functioning at all temperatures. Our novel findings demonstrate a relevant heat resilience of coffee species and that elevated [CO2 ] remarkably mitigated the impact of heat on coffee physiology, therefore playing a key role in this crop sustainability under future climate change scenarios.

Nutrient accumulation in bean and fruit from irrigated and non-irrigated Coffea canephora cv. Conilon

“…Such preservation of adequate mineral contents and balance within the plant is determinant for the expression of stress tolerance mechanisms on coffee (Ramalho et al, 2013), and assume a particular importance under predicted future conditions of climate changes and global warming (Martins et al, 2014), which are expected to simultaneously alter temperature and water availability to main crops, including to coffee (Rodrigues et al, 2016).…”

<b>Vegetative growth of Conilon coffee plants under two water conditions in the Atlantic region of Bahia State, Brazil

“…They also demonstrated a relevant heat resilience of coffee species and showed that an elevated CO 2 concentration remarkably mitigated the impact of heat on coffee physiology. In this regard, and fortunately, future perspectives on the sustainability of the coffee crop that are based on increasing temperature scenarios should not be as catastrophic as previously predicted (Rodrigues et al, 2016). …”

“…By studying the physiological and biochemical responses of photosynthesis to elevated atmospheric CO 2 concentration and/or temperature in several C. arabica and C. canephora genotypes, Rodrigues et al (2016) demonstrated that predictions concerning the impacts of climate change and global warming should consider the role of CO 2 as a key player in coffee heat tolerance. They also demonstrated a relevant heat resilience of coffee species and showed that an elevated CO 2 concentration remarkably mitigated the impact of heat on coffee physiology.…”

Microclimate and development of Coffea canephora cv. Conilon under different shading levels promoted by Australian cedar (Toona ciliata M. Roem. var. Australis)

“…According to Bunn et al (2015), higher temperatures may imply reduction in area suitable for coffee production. However, Rodrigues et al (2016) evaluating the interaction of high temperature coupled with the increase of CO 2 concentration on Coffea canephora and Coffea arabica, found increasing CO 2 concentrations strongly mitigated the effects of high temperatures on the photosynthetic machinery of coffee plants. In what concerns the relative humidity levels (RH), the Australian cedar promoted higher values along the entire year on both distances (T1 and T2) when compared to T3 (Fig.…”