Submitted to: Scientia Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/26/2016
Publication Date: 9/1/2016
Citation: Rodrigues, W.P., Machado Filho, J.A., A.M.M.A. Figueiredo, F., Massi Ferraz, T., Silva, J.R., Souza Ferreira, L., Da S. Bezerra, L.B., De Abreu, D.P., De P. Bernado, W., Cespom, L., Fernandes De Sousa, E., Glenn, D.M., Ramalho, J.C., Campostrini, E. 2016. Whole-canopy gas exchange in Coffea sp. is affected by supra-optimal temperature and light distribution within the canopy: the insights from an improved multi-chamber system. Scientia Horticulturae. 211:194-202.

Interpretive Summary: Plant architecture affects productivity and susceptibility to environmental stresses. The objectives of this study were to: 1) evaluate whole-canopy gas exchange of two coffee species: Coffea arabica cv. Catuaí Amarelo and Coffea canephora cv. Emcapa 8111 Clone 02 and 2) determine the effect of leaf area, branch angle, and light distribution within the canopy in two different seasons. C. arabica had a lower area leaf and higher branch angle resulting in greater light distribution within the canopy that contributed to higher net photosynthesis and transpiration as compared to C. canephora in both seasons. The dense canopy architecture of C. canephora limited whole-canopy gas exchange due to poor light distribution within the canopy. While C. arabica had better canopy light distribution resulting in higher photosynthetic rates than C. canephora during the spring, this architecture had a negative effect when C. arabica experiences increased temperature that reduced whole-canopy conductance. High temperatures may limit the growth and production of coffee plants in tropical areas, and a more closed plant architecture may mitigate this heat stress.

Technical Abstract: Given the difference of photosynthetic rate between the leaves in different positions of the canopy, leaf-level photosynthesis measurements can provide incomplete and potentially misleading information if extrapolated to quantify photosynthesis or infer differences in water demand and crop productivity at the whole plant level. Whole-canopy gas exchange provides a more accurate measurement of CO2 assimilation (Ac) and transpiration (Ec) for the coffee plant. The objectives of this study were to: 1) evaluate whole-canopy gas exchange of two coffee species: Coffea arabica cv. Catuaí Amarelo and Coffea canephora cv. Emcapa 8111 Clone 02 and 2) determine the effect of leaf area, branch angle, and light distribution within the canopy in two different seasons. Six plants > one-year-old of each species were grown in pots (100 L) in a greenhouse. Soil moisture was maintained at field capacity. Data were continuously collected for 10 days during spring (6 to 15 September 2014 moderate temperatures) and summer (5 to 14 February 2015 with high temperature), and micrometeorological variables were monitored inside the greenhouse. C. arabica had a lower area leaf and higher branch angle resulting in greater light distribution within the canopy that contributed to higher net photosynthesis and transpiration as compared to C. canephora in both seasons. C. arabica had reduced whole-canopy CO2 assimilation and transpiration during the summer, mainly linked to reduced whole-canopy conductance. However, C. canephora had similar whole-canopy CO2 assimilation and transpiration values in both seasons. The average water use efficiency (WUEc) was similar between both seasons and species despite reduced gas exchange for C. arabica in the summer; however, the relationship between Ac and Ec indicated that C. arabica had a greater instantaneous WUEc than C. canephora in the spring, and there were no differences between species in the summer sampling. The dense canopy architecture of C. canephora limited whole-canopy gas exchange due to poor light distribution within the canopy. While C. arabica had better canopy light distribution resulting in higher photosynthetic rates than C. canephora during the spring, this architecture had a negative effect when C. arabica experiences increased temperature that reduced whole-canopy conductance. High temperatures may limit the growth and production of coffee plants in tropical areas.