AUTHOR=Niu Zhengwen , Ye Zi-Wu-Yin , Huang Qi , Peng Chunju , Kang Huajing 

TITLE=Accuracy of photorespiration and mitochondrial respiration in the light fitted by CO2 response model for photosynthesis

JOURNAL=Frontiers in Plant Science

VOLUME=Volume 16 - 2025

YEAR=2025

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2025.1455533

DOI=10.3389/fpls.2025.1455533

ISSN=1664-462X

ABSTRACT=IntroductionAtmospheric CO2 elevation significantly impacts plant carbon metabolism, yet accurate quantification of respiratory parameters—photorespiration rate (Rp) and mitochondrial respiration rate in the light (Rd)—under varying CO2 remains challenging. Current CO2-response models exhibit limitations in estimating these parameters, hindering predictions of crop responses under future climate scenarios.MethodsLow-oxygen treatments and gas exchange measurements, calculating CO2 recovery/inhibition ratio in of wheat (Triticum aestivum L.) and bean (Glycine max L.) were employed to elucidate the biological significance and interrelationships of Rp and Rd. Model-derived estimates of Rp and Rd were compared with measured values to assess the accuracy of three CO2-response models (biochemical, rectangular hyperbola, modified rectangular hyperbola). Furthermore, the effects of ambient CO2 concentration (0~1200 μmol·mol-1) on the measured Rp and Rd were quantified through polynomial regression.ResultsThe A/Ca model achieved superior fitting performance over the A/Ci model. However, significant disparities persisted between A/Ca-derived Rp/Rd estimates and measurements (p < 0.05). CO2 concentration exhibited dose-dependent regulation of respiratory fluxes: Rp-measured ranged from 4.923 ± 0.171 to 12.307 ± 1.033 μmol (CO2) m-2 s-1 (wheat) and 4.686 ± 0.274 to 11.673 ± 2.054 μmol (CO2) m-2 s⁻ ¹ (bean), while Rd-measured varied from 0.618 ± 0.131 to 3.021 ± 0.063 μmol (CO2) m-2 s-1 (wheat) and 0.492 ± 0.069 to 2.323 ± 0.312 μmol (CO2) m-2 s-1 (bean). Polynomial regression revealed strong non-linear correlations between CO2 concentrations and respiratory parameters (R² > 0.891, p < 0.05; except bean Rp-Ca: R² = 0.797). Species-specific CO2 thresholds governed peak Rp (600 μmol·mol-1 for wheat vs. 1,000 μmol·mol-1 for bean) and Rd (400 μmol·mol-1 for wheat vs. 200 μmol·mol-1 for bean).DiscussionThese findings expose critical limitations in current respiratory parameter quantification methods and challenge linear assumptions of CO2-respiration relationships. They establish a critical framework for refining photosynthetic models by incorporating CO2-responsive respiratory mechanisms. The identified non-linear regulatory patterns and model limitations provide actionable insights for advancing carbon metabolism theory and optimizing crop carbon assimilation strategies under rising atmospheric CO2, with implications for climate-resilient agricultural practices.