Effects of saturation flash protocols on photosynthetic induction and assessment of mesophyll conductance and maximum carboxylation rate sensitivity to parameter inputs in Ficus carica

TL;DR

This study examines how saturation flash protocols affect photosynthesis in Ficus carica and finds they don't interfere with the induction process.

Contribution

The study provides new insights into the sensitivity of mesophyll conductance and carboxylation rate to parameter changes during photosynthetic induction.

Findings

Saturation flashes do not interfere with the photosynthetic induction process in Ficus carica.

Mesophyll conductance and maximum carboxylation rate increase gradually during induction.

Stomatal limitation is the primary factor limiting photosynthesis in Ficus carica.

Abstract

Improving photosynthetic efficiency during the induction phase is a key strategy for enhancing plant productivity. A critical prerequisite for achieving this goal is identifying the limitation factors that affect photosynthesis during induction. While stomatal conductance to water vapor (gsw) can be quantified using gas exchange measurements, the quantification of mesophyll conductance (gm) and maximum carboxylation rate (Vcmax) remains uncertain and underexplored. This study, using Ficus carica as plant material, aims to investigate whether saturation flashes influence the photosynthetic induction process and assess the sensitivity of gm, Vcmax, and photosynthetic limitation analysis to key photosynthetic parameters. The results revealed no significant differences in the dynamics of photosynthesis and stomatal conductance between treatments with and without saturation flashes, indicating that saturation flashes did not interfere with the photosynthetic induction process. Further analysis of the photosynthetic induction process showed that gm and Vcmax exhibited a gradual increase during induction. Moreover, sensitivity analysis demonstrated that variations in the leaf absorptance parameter (αβ) and CO2 compensation point (Γ*) significantly impacted the estimation of gm and Vcmax, while changes in the Rubisco affinity constant (Km) also notably influenced Vcmax. Finally, photosynthetic limitation analysis revealed that stomatal limitation (SL) was the primary factor limiting photosynthesis in Ficus carica, accounting for 41.4% of the total limitation, followed by mesophyll conductance limitation (MCL) and biochemical limitation (BL), which accounted for 30.9% and 27.7%, respectively. Statistical analysis revealed no significant changes in the overall pattern of photosynthetic limitations across different sensitivity analysis scenarios. Overall, this study demonstrates that saturation flashes do not interfere with photosynthetic induction in Ficus carica, while changes in αβ, Γ*, and Km affect the estimation of gm and Vcmax but have no significant impact on the estimation of photosynthetic limitations. This study provides a theoretical basis for improving photosynthetic efficiency during the induction phase in Ficus carica and enhances our understanding of photosynthetic induction measurement and calculation methods.

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