The "One-Point Rapid" Method for Estimating the Capacity for Photosynthetic CO2 Assimilation Must be Used with Caution
Acclimation to saturating light is often required for the method to be effective.
The gold-standard method for measuring the capacity for photosynthetic carbon dioxide (CO2) assimilation is time consuming. A rapid method to mathematically estimate this capacity from a single measurement rather than a full curve has been celebrated in the literature, but there are several key limitations to the effectiveness of this rapid method, including acclimation to light.
The accurate estimation of the capacity for photosynthetic CO2 assimilation is critical for the parameterization of climate models. Employing a rapid “one-point” method can improve model parameterization but only if the results are accurate. Deepening the scientific understanding of the limitations of this method allows appropriate use of the technique.
The maximum carboxylation capacity of photosynthesis (Vc,max) is usually obtained using a gold-standard photosynthetic CO2 response curve. A rapid one-point method mathematically estimates Vc,max from a single-point measurement of photosynthesis rather than a full response curve, taking only a fraction of the time. Scientists from Brookhaven National Laboratory evaluated the practical application of the one-point method in six species measured both under standard conditions and under conditions that would increase the likelihood of successful estimation of Vc,max. Under standard measurement conditions, the one-point method significantly underestimated Vc,max in four of the six species, providing estimates 21% to 32% below fitted values. They identified three factors that can limit the effective use of the one-point method to accurately estimate Vc,max: (1) limitation of photosynthesis by carboxylation, when the measurement is taken; (2) acclimation of leaves to saturating light conditions prior to measurement; and (3) accurate estimation of leaf respiration. Most critical of these is the requirement for acclimation to saturating light. The requirements vary among species, meaning that the one-point method requires a species-specific understanding of its application and must be used with caution.
Brookhaven National Laboratory
This work was supported by the Office of Biological and Environmental Research (BER), within the U.S. Department of Energy (DOE) Office of Science, under Contract No. DE-SC0012704 to Brookhaven National Laboratory and received partial support (e.g., some of the data collection) from the Next-Generation Ecosystem Experiments (NGEE)–Arctic project, which is supported by DOE BER.
Burnett, A. C., K. Davidson, S. P. Serbin, and A. Rogers. “The ‘one-point method’ for estimating maximum carboxylation capacity of photosynthesis: A cautionary tale.” Plant, Cell & Environment 42(8), 2472–81 (2019). [DOI:10.1111/pce.13574].
Burnett, A. C., K. Ely, K. Davidson, et al. “Evaluation of the one-point method for estimating carboxylation capacity, Barrow, Alaska and Upton, New York, 2018. (2019) Next Generation Ecosystem Experiments Arctic Data Collection, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tenn. [DOI:10.5440/1506965].