Ecophysiological responses of coffee plants to heat and drought, intrinsic resilience and the mitigation effects of elevated air [CO₂] in a context of climate changes

Climatic models have projected increasing harmful impacts of climate changes on natural and agricultural ecosystems along this century. The increase of atmospheric CO₂ concentration ([CO₂]) has been associated with a greater frequency of extreme weather events, as increased air temperature and heat waves, and altered rainfall patterns that boost floods and droughts more often and for longer periods. Agriculture ecosystems are expected to be greatly vulnerable to such new climatic conditions, with relevant impacts on crop productivity/quality/sustainability, and plant survival. Forecasts suggest that the coffee tree (Coffea spp.) will be strongly affected by warming and drought, with decreases in crop productivity, and biodiversity. However, several studies indicate that some coffee elite genotypes display a greater environmental resilience than what was usually believed. Moreover, elevated [CO₂] (e[CO₂]) has been shown to remarkably attenuate the impairments associated with stressful conditions at physiological and biochemical levels, by improving the photosynthesis apparatus functioning, heightening water-use efficiency, and strengthening some protective mechanisms. Additionally, e[CO₂] may also promote architectural and morphological changes, with allometric adjustments linked to biomass partitioning within plant organs and growth stimulation, and ultimately greater crop yields. In this context, here we highlight the latest studies regarding coffee response mechanisms to low water availability and elevated temperatures, and why e[CO₂] can improve plant resiliency to such environmental stresses. Altogether, these findings are of utmost importance to the coffee crop sustainability under the projected future climatic scenarios.