Two minuses can make a plus: waterlogging and elevated CO₂ interactions in sweet cherry (Prunus avium) cultivars

The increase in the ambient concentration of CO₂ and other greenhouse gases is producing climate events that can compromise crop survival. However, high CO₂ concentrations are sometimes able to mitigate certain stresses such as salinity or drought. In this experiment, the effects of waterlogging and CO₂ are studied in combination to elucidate the eventual response in sweet cherry trees. For this purpose, four sweet cherry cultivars ('Burlat', 'Cashmere', 'Lapins and 'New Star') were grafted on a typically hypoxia-tolerant rootstock (Mariana 2624) and submitted to waterlogging for 7 days at either ambient CO₂ concentration (400 µmol mol^-1 ) or at elevated CO₂ (800 µmol mol^-1 ). Waterlogging affected plants drastically, by decreasing photosynthesis, stomatal conductance, transpiration, chlorophyll fluorescence and growth. It also brought about the accumulation of proline, chloride and sulfate. Nonetheless, raising the CO₂ supply not only mitigated all these effects but also induced the accumulation of soluble sugars and starch in the leaf. Therefore, sweet cherry plants submitted to waterlogging were able to overcome this stress when grown in a CO₂ -enriched environment.