Paper Reviewed
Pérez-Jiménez, M., Hernández-Munuera, M., Piñero, M.C., López-Ortega, G. and del Amor, F.M. 2017. CO2 effects on the waterlogging response of 'Gisela 5' and 'Gisela 6' (Prunus cerasus x Prunus canescens) sweet cherry (Prunus avium) rootstocks. Journal of Plant Physiology 213: 178-187.

One of the model-based climate predictions to result from increases in the atmosphere's CO2 content is that there will be an increase in the number of heavy precipitation events. Such events, if they occur, could lead to flooding and waterlogging of soils. Despite this possibility, Pérez-Jiménez et al. (2017) point out in their recently-published paper that "the combined effect of waterlogging and elevated CO2 has been scarcely studied," while additionally pointing out that the topic "has never been studied in fruit trees." Thus, it became the objective of this group of five Spanish scientists to perform the first such analysis by examining the interactive effects of elevated CO2 and waterlogging on sweet cherry (Prunus avium).

To accomplish their design, Jiménez et al. subjected 1-year-old seedlings of the Burlat sweet cherry cultivar that was grafted onto one of two different rootstocks (Gisela 5 and Gisela 6) to three weeks of growth in a controlled-environment chamber of either 400 or 800 ppm CO2. After the first seven days, plants in each chamber were subjected to two additional treatments (1) a control treatment in which normal daily irrigation was allowed to counter daily water loss, or (2) a waterlogging treatment where the water level was maintained at least 1 cm above the surface of the soil. Seven days later, the waterlogged plants were drained and returned to the control conditions experienced during the first seven days of the study. Multiple parameters pertaining to plant water status and growth were measured during the experiment so that the scientists could test their hypothesis, which was that elevated CO2 would "confer on plants better resistance to waterlogging."

In describing their findings, Jiménez et al. report that the net photosynthesis of the cherry tree leaves was "markedly influenced by the CO2 concentration," such that "it was significantly higher after every phase of the experiment, in plants grafted on both rootstocks, at elevated CO2." Indeed, percentage increases in net photosynthesis due to elevated CO2 in both rootstock plants ranged from 113 to 180 percent higher under control conditions (normal watering) and from 106 to 663 percent higher under waterlogged conditions. Jiménez et al. also found that there was a reduction in stomatal conductance in waterlogged plants under the ambient CO2 treatment, whereas they report that "an atmosphere enriched with CO2 improved the physiological status of waterlogged plants, reducing the need for a stomatal conductance reduction to mitigate water logging." Elevated CO2 was also found to have increased the stem diameter of the Gisela 6 rootstock plants (relative to ambient) and both the stem diameter and height of Gisela 5 seedlings.

In light of all of the above discoveries, plus others of the author's observations, Jiménez et al. conclude that "elevated CO2 was able to increase photosynthesis and thereby help plants to overcome waterlogging." And thus they document yet another important benefit of atmospheric CO2 enrichment for earth's plant life.