Paper Reviewed
da Silva, J.R., Patterson, A.E., Rodrigues, W.P., Campostrini, E. and Griffin, K.L. 2017. Photosynthetic acclimation to elevated CO2 combined with partial rootzone drying results in improved water use efficiency, drought tolerance and leaf carbon balance of grapevines (Vitis labrusca). Environmental and Experimental Botany 134: 82-95.

In providing the rationale for their work, da Silva et al. (2017) write that grapevines are a widely cultivated fruit, grown on nearly every continent. Given the importance of this cultivation, they say that "it is imperative to study the effects of predicted global change on the physiological underpinnings of production, as well as the possible management alternatives that may be used to maintain this production." Therefore, it was their objective to examine the interactive effects of elevated CO2 and reduced water availability on a number of key physiological and growth traits. This was accomplished by growing six week old Concord (Vitis labrusca) grape plants in controlled environment chambers at either ambient (400 ppm) or elevated (800 ppm) levels of atmospheric CO2 for a period of 24 days under three different water management treatments: (1) full irrigation, in which the rootzone was irrigated to saturation three days per week, (2) partial root drying, where alternating halfs of the rootzone were irrigated to saturation three days per week, and (3) no irrigation, in which irrigation was suspended for the duration of the 24 day experiment.

Results indicated that elevated CO2 increased net photosynthesis by 24 percent and specific leaf weight by 16 percent, whereas it reduced stomatal density by 25 percent over the 24 days of enrichment. With respect to its influence on drought, da Silva et al. report that "elevated CO2 dramatically increased drought tolerance of grapevines" by enhancing plant water use efficiency, which occurred primarily because of observed CO2-induced increases in net photosynthesis and corresponding CO2-induced declines in both stomatal conductance and transpiration rates. What is more, the authors state that in the no irrigation treatment, water depletion in the root zone developed at a slower rate in the elevated CO2 chambers, delaying the effects of drought by about four days. Such combined findings led da Silva et al. to conclude that, "overall, elevated CO2 improves the leaf carbon balance and this mitigates the deleterious effects of drought on grapevines." And that is good news for grape growers and consumers, especially in drought-prone regions.