Avila, R.T., de Almeida, W.L.,
Costa, L.C., Machado, K.L.G.,
Barbosa, M.L., de Souza, R.P.B.,
Martino, P.B., Juáárez, M.A.T.,
Marcal, D.M.S., Martins, S.C.V.,
Ramalho, J.D.C. and DaMatta, F.M.
2020
Elevated air [CO2] improves
photosynthetic performance
and alters biomass accumulation
and partitioning in drought-stressed
coffee plants.
Environmental and Experimental Botany
177: 104137.
FULL SUMMARY HERE:
http://www.co2science.org/articles/V23/oct/a2.php
My Short Summary Follows:
Avila et al. (2020) examined the effect of water stress on coffee plants under ambient (400 ppm) or elevated (700 ppm) CO2 levels, for seven months -- five months with adequate water, then half of the plants were exposed to drought stress for two months.
Elevated CO2 enhanced plant total dry matter by +32% under well-watered conditions, but by a much larger +59% under drought-stressed conditions.
Figure 1:
The effect of watering (well-watered or drought-stressed plants) and CO2 supply (400 or 700 ppm) on the net photosynthetic rate (left panel) and water-use efficiency (right panel) of coffee plants. Measurements were made at 50, 37.5, 25 and 20 % of field capacity for the drought-stressed plants. The percentages in red text indicate the change in photosynthesis or water use efficiency due to atmospheric CO2 for a given water treatment (i.e., well-watered or drought).
Figure 2:
Representative phenotypic appearance of shoot and roots of coffee plants exposed to different combinations of ambient or elevated CO2 and well-watered or drought-stressed conditions.