Growth and yield stimulation under elevated CO2 and drought: A meta-analysis on crops

© 2015 Elsevier B.V. Exposure of plants to elevated CO2(eCO2) has a number of physiological effects, including increased photosynthetic carbon fixation and decreased stomatal conductance, resulting in greater growth and yield and also improved water use efficiency. Therefore, eCO2is considered to ameliorate the adverse effects of drought. To test this assumption in existing literature, we undertook a meta-analysis to study the interactive effects of eCO2and experimentally imposed drought on biomass and yield of crops and pasture grasses. We found that for crop species with C3metabolism, eCO2stimulates biomass accumulation and yield under both well-watered and dry conditions to a similar extent. For C4crops, however, stimulation of biomass accumulation and yield by eCO2occurs only under dry growing conditions. Disentangling other functional groups (annuals vs. perennials, crop species, experimental setups) also showed that plant metabolism greatly determines the overall effect of eCO2and water availability on plant performance. Our results suggest that crops grown in areas with limited water availability will benefit from future eCO2, regardless of their metabolism. Drought leads to stomatal limitation of photosynthesis in both C3and C4crops, which is alleviated when the plants are grown under eCO2.