Early growth phase and caffeine content response to recent and projected increases in atmospheric carbon dioxide in coffee (Coffea arabica and C. canephora)

Authors: Vega, Fernando; Ziska, Lewis; Simpkins, Ann; INFANTE, FRANCISCO - Colegio De La Frontera; DAVIS, AARON P - Royal Botanical Gardens; RIVERA, JOSEPH - Coffee Intelligence, Llc; Barnaby, Jinyoung; Wolf, Julie

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/16/2020
Publication Date: 4/3/2020
Citation: Vega, F.E., Ziska, L.H., Simpkins, A., Infante, F., Davis, A., Rivera, J., Barnaby, J.Y., Wolf, J.E. 2020. Early growth phase and caffeine content response to recent and projected increases in atmospheric carbon dioxide in coffee (Coffea arabica and C. canephora). Scientific Reports. 10:5875.

Interpretive Summary: Projections for increased carbon dioxide levels in the atmosphere have generated an interest in understanding plant responses, not only in terms of growth, but also in terms of the plants’ internal chemistry. Among the plants receiving worldwide attention, coffee is of special interest because of its importance to coffee-producing countries and to consumers worldwide. Three Coffea arabica cultivars (arabica coffee) and one Coffea canephora (robusta coffee) line were grown from germination to 12 months at one of four carbon dioxide concentrations: 300, 400, 500 or 600 parts per million. We assessed leaf area, branch number, and total above-ground biomass. At the qualitative level, leaf nitrogen declined and carbon to nitrogen ratios increased when averaged for all cultivars. For caffeine, there were significant differences in carbon dioxide response between arabica and robusta. This information will be of use to coffee scientists, plant physiologists, ecologists, and the coffee industry.

Technical Abstract: Since 1960, background levels of atmospheric carbon dioxide concentration, [CO2], have risen from 317 to ca. 415 parts per million by volume (ppmv), an increase of ca. 31%. At present rates, it is anticipated that [CO2] will double from pre-industrial levels to between 600-800 ppmv by the end of the 21st century. However, less is known on the influence of recent and projected [CO2] increases in perennial crops, relative to annual crops, particularly regarding post-germination growth and early development. Among perennial crops, coffee is recognized as being of global importance, with two primary species, Coffea arabica (arabica coffee) and C. canephora (robusta coffee) accounting for 99% of global production. In the current study, three arabica cultivars and one robusta line were grown from germination to 12 months at one of four CO2 concentrations (300, 400, 500 or 600 ppmv). Significant increases were observed in all leaf area and biomass markers in response to [CO2] with significant [CO2] by varietal differences observed at 122-124 days after sowing (DAS). At 12 months (366-368 DAS), CO2 by cultivar variation in growth and biomass response among arabica cultivars was not significant; however, significant trends in leaf area, branch number and total above-ground biomass were observed between arabica and robusta. At the qualitative level, leaf nitrogen declined and carbon to nitrogen ratios increased when averaged for all cultivars in response to [CO2]; similar increases where observed for both arabica and robusta. However, for caffeine, there were significant differences in [CO2] response between arabica and robusta. Overall, these data suggest that differential responses during early growth and development of arabica and robusta may have already occurred with recent [CO2] increases, and that such differences may be exacerbated as [CO2] continues to increase.