The vegetative growth assists to reproductive responses of Arabic coffee trees in a long-term FACE experiment

TLDR: The aim was to estimate leaf-gas exchange dynamics, flowering, fruiting intensity and quality in Coffea arabica grown in long-term FACE experiment under rainfed conditions and found elevated CO 2 mitigated the effects of anomalous drought and high temperatures in rainy season, reducing the abnormal reproductive structures rate.

Abstract: In simulation studies of Arabic coffee plants under the future CO2 conditions, no data about flowering, yield fractions or beverage sensorial have been reported. It was hypothesized that elevated CO2 (e[CO2]) would improve the leaf-gas exchange responses, assisting in improvement of coffee reproduction. The aim was to estimate leaf-gas exchange dynamics, flowering, fruiting intensity and quality in Coffea arabica grown in long-term FACE experiment under rainfed conditions. Leaf-gas exchanges were followed for five years during vegetative and reproductive stages; flowering was observed at second order axis scale for 4 years; berry production, its fractions and beverage sensorial were estimated at plot scale in the 4th production year under FACE. Young coffee plants did not modify leaf-gas exchange responses under e[CO2] in observed periods, while the adult ones increased leaf-photosynthesis in all observed stages. Stomatal conductance and water use efficiency were higher under e[CO2] than actual [CO2] in some stages of flowering, berry expansion and ripping, benefited from higher water content over the soil profile in advanced years of FACE. Elevated CO2 mitigated the effects of anomalous drought and high temperatures in rainy season, reducing the abnormal reproductive structures rate. Under e[CO2], the intense leaf-photosynthesis did not improve the yield or sensorial beverage quality in 4th production year, but a fraction of green berries, indicating flowering delay or prolongated ripening. The e[CO2] supported species survival during short intensive drought through high carbon investments in reproduction, while long/anomalous droughts reduced the fraction of flower abnormalities, indicating carbon investments in individual plant survival.