# Preliminary results on A/Ci curves with LI-6800: dynamic assimilation technique vs steady-state method in common temperate trees

Juliette Archambeau, Laëtitia de Felix, Thomas Caignard, Marc Peaucelle

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Juliette Archambeau, Laëtitia de Felix, Thomas Caignard, Marc Peaucelle. Preliminary results on A/Ci curves with LI-6800: dynamic assimilation technique vs steady-state method in common temperate trees. EGU Mary Anning Conference 2025 – Novel constraints on the coupling between the water and carbon cycles, Jun 2025, Bordeaux, France. hal-05120834

HAL Id: hal-05120834

https://hal.science/hal-05120834v1

Submitted on 19 Jun 2025

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# Preliminary results on A/Ci curves with LI-6800: dynamic assimilation technique
## vs steady-state method in common temperate trees

Archambeau Juliette<fnref n="1" />, De Felix Laetitia<fnref n="1" />, Caignard Thomas<fnref n="2" />,<fnref n="3" />, Peaucelle Marc<fnref n="1" />

<figure><img src="image_3.png" /><figcaption>LI-6800 Portable Photosynthesis System</figcaption></figure>

**Introduction.** Key photosynthetic parameters—**Vcmax** (maximum rate of Rubisco carboxylation) and **Jmax** (regeneration rate of RuBP through electron transport)—can be derived from **A/Ci curves**, which measure net photosynthetic rate (A) across intercellular CO₂ concentrations (Ci) using infrared gas analyzers (IRGAs) like the LI-6800. Traditionally, these curves were obtained via the **steady-state method**, where measurements are taken only after leaf stability at each CO₂ level, making the process time-consuming. Recently, the **dynamic assimilation technique**, which uses a continuously ramping CO₂ input, has been developed to generate A/Ci curves more quickly, providing Vcmax and Jmax estimates comparable to those from the steady-state method in crops and tropical trees.

**Objective.** Evaluate whether the dynamic assimilation technique can be used in temperate trees to estimate Vcmax and Jmax.

**Methods.** Compare dynamic and steady-state A/Ci curves in four temperate tree species under saturating light conditions and a standard temperature of 25°C.

**Some preliminary results.** Species differed markedly in their responses to the dynamic assimilation technique.

<figure><img src="image_4.png" /><figcaption>Alnus glutinosa</figcaption></figure>

<figure><img src="image_5.png" /><figcaption>Populus nigra</figcaption></figure>

<figure><img src="image_6.png" /><figcaption>Quercus pubescens</figcaption></figure>

<figure><img src="image_7.png" /></figure>

**Discussion.** How to explain such differences?

* **Technical choices?**

* CO₂ ramp rate: set to 100 µmol mol⁻<fnref n="1" /> min⁻<fnref n="1" /> for *A. glutinosa* and *Q. pubescens* vs 300 µmol mol⁻<fnref n="1" /> min⁻<fnref n="1" /> for *F. sylvatica* and *P. nigra*.

* Order of curve measurements: dynamic curves measured after steady-state curves for *P. nigra*, *F. sylvatica*, and leaf 2 of *Q. pubescens*, but before steady-state curves for *A. glutinosa* and leaves 1 and 3 of *Q. pubescens*.

* **Species strategies?** e.g., fast-growing vs slow-growing species.

* **Stomatal responses?** See curves below.

<figure><img src="image_8.png" /></figure>

<figure><img src="image_9.png" /></figure>

<figure><img src="image_10.png" /></figure>

<figure><img src="image_11.png" /></figure>

**Feedback on these open questions is more than welcome!**

Feel free to email us at [juliette.archambeau@inrae.fr](mailto:juliette.archambeau@inrae.fr) and [marc.peaucelle@inrae.fr](mailto:marc.peaucelle@inrae.fr)

Or if you see us around, don't hesitate to have a chat!

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<figure><img src="image_13.png" /></figure>

Funded by the European Union (ERC, LEAFPACE, 101117001). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Research Council. Neither the European Union nor the granting authority can be held responsible for them.

<footnote n="1">¹ INRAE, University of Bordeaux, UMR 1391 ISPA, 33140 Villenave-d'Ornon, France</footnote>

<footnote n="2">² INRAE, University of Bordeaux, UMR BIOGECO, F-33610 Cestas, France</footnote>

<footnote n="3">³ Institute for Transitions, University of Bordeaux, France</footnote>