Does the response of Rubisco and photosynthesis to elevated CO2 change with unfavourable environmental conditions?

Climate change due to anthropogenic CO2 emissions affects plant performance globally. To improve crop resilience, we need to understand the effects of elevated CO2 concentration (eCO2) on CO2 assimilation and Rubisco biochemistry. However, the interactive effects of eCO2 and abiotic stress are especially unclear. This study examined the CO2 effect on photosynthetic capacity under different water availability and temperature conditions in 42 different crop species, varying in functional group, photosynthetic pathway, and phenological stage. We analysed close to 3000 data points extracted from 120 published papers. For C3 species, eCO2 increased net photosynthesis and intercellular CO2, while reducing stomatal conductance and transpiration. Maximum carboxylation rate and Rubisco in vitro extractable maximal activity and content also decreased with eCO2 in C3 species, while C4 crops are less responsive to eCO2. The interaction with drought and/or heat stress did not significantly alter these photosynthetic responses, indicating that the photosynthetic capacity of stressed plants responded to eCO2. Moreover, eCO2 had a strong effect on the photosynthetic capacity of grasses mainly in the final stages of development. This study provides insight into the intricate interactions within the plant photosynthetic apparatus under the influence of climate change, enhancing the understanding of mechanisms governing plant responses to environmental parameters.