Elevated air CO2 conditions changes the metabolic profile of Arabic coffee leaves during vegetative and reproductive stages.

Effects of drought, elevated air CO2 and temperature can change the quality of food. Arabic coffee is characterized by biannual phenological cycle constituted by six stages: vegetative that occurs under long days, maturation of reproductive buds (MRB), flowering and grain expansion (FGE), grain formation (GF), grain maturation (GM) and senescence. We expected that leaf metabolic profile of plants cultivated under elevated CO2 would differentiate among stages of vegetative and reproductive growth. The aim of this study was to analyze those variations in Free-Air-CO2-Enrichment (FACE) experiment. In the 2nd year of growing under rainfed conditions in FACE, fully expanded coffee leaves were collected in four periods: June 2012 (MRB1-transformation of vegetative to reproductive buds), July 2012 (MRB2-relative bud dormancy), December 2012 (FGE) and January 2013 (GF). GCMS datasets, coupled with multivariate statistical methods, were used to investigate 35 compounds identified in coffee leaves growing in two CO2 conditions, actual (a[CO2], ~ 390?L CO2 L-1) and elevated (e[CO2], ~590?L CO2 L-1). Mainly, the content of amino, fatty and organic acids besides phenolic compounds and sterols, diminished under e[CO2] (Table 1). Only the content of dodecanoic (GF) and citric (MRB1) acids increased. Under e[CO2], both reduction or increase in leaf carbohydrate contents occurred. Sugar alcohols as mannitol (FGE), galactitol (FGE) and pinitol (MRB1) showed 16, 22 and 37 times higher content under e[CO2] than a[CO2], respectively. The PCA showed an obvious separation in CO2 treatments, differing metabolites in all stages, not only vegetative from reproductive ones (Figure 1). The high leaf investments in carbohydrates, specifically sugar alcohols, indicates quick investments of carbon in metabolites under e[CO2]. Higher levels of citric and dodecanoic acids under e[CO2] than a[CO2] suggest the mitigation of various stress conditions under e[CO2], as drought, low/high temperatures and presence of coffee leaf rust attack, which were observed along the experimental period.