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 (e[CO2]) on CO2 assimilation and Rubisco biochemistry. However, the interactive effects of e[CO2] 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 C-3 species, e[CO2] 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 e[CO2] in C-3 species, while C-4 crops are less responsive to e[CO2]. 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 e[CO2]. Moreover, e[CO2] 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.

MA was supported by the 'Juan de la Ciervaformacion' postdoctoral fellowship (FJC2020-044164-I) from the Spanish Ministry of Science and Innovation MCIN/AEI/10.13039/501100011033 and the European Union 'Next Generation EU/PRTR'. IJ thanks the Navarra Government for granting him the fellowship Andia Senior Talent 2021. This work has been conducted within the context of the CropEqualT-CEC project funded by the European Union's Horizon 2020, Marie Curie Rise re-search and innovation program. Finally, the authors acknowledge the support provided by the CSIC Open Access Publication Support Initiative, facilitated through its Unit of Information Resources for Research (URICI), for covering the open access fee.