The maximum rate of carboxylation of ribulose-1,5-bisphosphate (Vcmax) represents a key biochemical trait and a fundamental parameter in C3 models of photosynthesis, as it enables an accurate representation of leaf carbon assimilation and gas exchange. Accurate estimation of this parameter is essential for process‑based modelling across scales, as uncertainties in Vcmax may influence model behaviour when scaled from leaves to larger spatial domains. Traditionally, Vcmax is derived from the response of photosynthesis (A) to intercellular CO2 concentration (Ci), known as the A/Ci curve, a reliable but time-consuming and labour-intensive procedure that limits its application in high-throughput phenotyping. To address this limitation, rapid approaches such as the Rapid A/Ci Response (RACiR) and the one-point (OP) methods have been developed. However, their accuracy, reliability, and reproducibility must be carefully validated, as discrepancies arising from the use of heterogeneous data sources for model parameterization may introduce significant uncertainty. In this study, the RACiR and the OP methods were evaluated against the conventional A/Ci curve in a two-year field experiment on four Cannabis sativa varieties grown under different irrigation regimes. Photosynthetic traits derived from each method were compared and integrated into a coupled A-stomatal conductance (gs) model to assess how method-driven differences affect model outputs. Overall, photosynthetic traits estimated from A/Ci curves provided the most accurate simulations of gs, with R2 values ranging from 0.55 to 0.84 and the lowest RMSE. In contrast, traits derived from RACiR and OP methods resulted in gs overestimations of 26.7% and 50.7%, respectively. Field application of RACiR was hindered by high failure rates under high summer temperatures, while OP estimates showed substantial variability. These results indicate that, despite the appeal of faster alternatives, the A/Ci curve remains the most reliable method for estimating Vcmax under Mediterranean field conditions, particularly when high accuracy is required for model-based applications.
Quantification of leaf photosynthetic traits in field conditions: Towards an efficient and reliable method for plant phenotyping and modelling ecophysiological processes
A. Conte
Primo
Writing – Original Draft Preparation
;A. Carli;M. Haworth;V. Montesano;D. Danzi;G. Atzori;A. P. M. Fabbri;A. Daccache;R. M. Balestrini;M. Centritto
2026
Abstract
The maximum rate of carboxylation of ribulose-1,5-bisphosphate (Vcmax) represents a key biochemical trait and a fundamental parameter in C3 models of photosynthesis, as it enables an accurate representation of leaf carbon assimilation and gas exchange. Accurate estimation of this parameter is essential for process‑based modelling across scales, as uncertainties in Vcmax may influence model behaviour when scaled from leaves to larger spatial domains. Traditionally, Vcmax is derived from the response of photosynthesis (A) to intercellular CO2 concentration (Ci), known as the A/Ci curve, a reliable but time-consuming and labour-intensive procedure that limits its application in high-throughput phenotyping. To address this limitation, rapid approaches such as the Rapid A/Ci Response (RACiR) and the one-point (OP) methods have been developed. However, their accuracy, reliability, and reproducibility must be carefully validated, as discrepancies arising from the use of heterogeneous data sources for model parameterization may introduce significant uncertainty. In this study, the RACiR and the OP methods were evaluated against the conventional A/Ci curve in a two-year field experiment on four Cannabis sativa varieties grown under different irrigation regimes. Photosynthetic traits derived from each method were compared and integrated into a coupled A-stomatal conductance (gs) model to assess how method-driven differences affect model outputs. Overall, photosynthetic traits estimated from A/Ci curves provided the most accurate simulations of gs, with R2 values ranging from 0.55 to 0.84 and the lowest RMSE. In contrast, traits derived from RACiR and OP methods resulted in gs overestimations of 26.7% and 50.7%, respectively. Field application of RACiR was hindered by high failure rates under high summer temperatures, while OP estimates showed substantial variability. These results indicate that, despite the appeal of faster alternatives, the A/Ci curve remains the most reliable method for estimating Vcmax under Mediterranean field conditions, particularly when high accuracy is required for model-based applications.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
