# The multiple mechanosensitive responses of wood formation to bending

Jeanne Roignant, Éric Badel, Bruno Moulia, Nathalie Leblanc-Fournier, Nicole Brunel-Michac, Julien Ruelle, Mélanie Decourteix

► To cite this version:

Jeanne Roignant, Éric Badel, Bruno Moulia, Nathalie Leblanc-Fournier, Nicole Brunel-Michac, et al. The multiple mechanosensitive responses of wood formation to bending. 10th International Plant Biomechanics Conference, Aug 2022, Lyon (ENS Lyon), France. **hal-04953094**

HAL Id: hal-04953094

https://hal.science/hal-04953094v1

Submitted on 24 Feb 2025

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# The multiple mechanosensitive responses of wood formation to bending: a matter of sign of the strains, dose, and sensitivity adjustments

INRAE
Auvergne
Rhône-Alpes

U.M.R. PIAF

<figure><img src="image_2.png" /></figure>

UNIVERSITÉ
Clermont
Auvergne

Jeanne Roignant¹, Éric Badel¹, Bruno Moulia¹, Nathalie Leblanc-Fournier¹, Nicole Brunel-Michac¹, Julien Ruelle² and Mélanie Decourteix¹*

¹Université Clermont Auvergne, INRAE, PIAF, F-63000 Clermont-Ferrand, France

² Université de Lorraine, AgroParisTech, INRAE, UMR Silva, F-54000, Nancy, France

<figure><img src="image_3.png" /></figure>

* melanie.decourteix@uca.fr

## INTRODUCTION

<figure><img src="image_4.png" /></figure>

## HYPOTHESIS

- Different types of specific local strains (strain amplitude and strain sign) could generate different radial growth and wood differentiation responses.

- There could be a dose-effect of bending on wood formation : a higher number of bending may modify the wood formation responses.

## EXPERIMENTS

<figure><img src="image_5.png" /></figure>

ε = strains

CFW = Compressive Flexure Wood

TFW = Tensile Flexure Wood

N = neutral zone

C = Compressed zone

S = Stretched zone

<figure><img src="image_6.png" /></figure>

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

## The effects of repeated bending on secondary growth

### The number of bending treatments modulates the secondary growth

Cumulative radial increment
of the stem (D//–D₀) (mm)

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

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

The weekly radial increment of the stem was measured parallel to the bending direction

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

D// = diameter parallel
to the bending direction

D₀ = D// the day of the
first bending

$3B/w < 15B/w$

$3B/w \neq 5 \times 15B/w$

The response isn't linear

⇒ **DOSE-EFFECT**

⇒ **ACCOMMODATION**

to successive stimulations

### Increasing the dose reveals new abilities of wood cells to respond to bending

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

elliptic shape

<figure><img src="image_12.png" /></figure>

egg-shape

**LOCAL perception** of longitudinal strains (3B/w)
**BUT MORE THAN** just the absolute value of longitudinal strain! (15B/w)

## The effects of repeated bending on xylem anatomy

### Tensile and compressive strains lead to contrasted responses

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

CONTROL

<figure><img src="image_14.png" /></figure>

<figure><img src="image_15.png" /></figure>

<figure><img src="image_16.png" /></figure>

15B/w treatment

G-layer = peculiar internal cell wall layer produced by wood fibers in tension wood

FLA = Fasciclin-like arabinogalactan-protein -> important for the formation of tension wood

<figure><img src="image_17.png" /></figure>

STRETCHED

<figure><img src="image_18.png" /></figure>

<figure><img src="image_19.png" /></figure>

<figure><img src="image_20.png" /></figure>

Vessel density: **-28%**

Vessel diameter: **-8%**

Fibers with G-layer: S-layer ↗

**UP-regulation** of the expression of some **FLA** genes

Fibers without G-layer: S-layer ↗

<figure><img src="image_21.png" /></figure>

COMPRESSED

<figure><img src="image_22.png" /></figure>

<figure><img src="image_23.png" /></figure>

Vessel density: **-25%**

Vessel diameter: not modified

**Inhibition of G-layer formation**

**DOWN-regulation** of the expression of some **FLA** genes
S-layer ↗↗

A, B, C : cross-sections of xylem samples stained with Astra blue-safranin

a, b, c : close-up on fibers

b1 : fibers without G-layer; b2 : fibers with G-layer

Ability to perceive the **SIGN OF THE STRAINS** (tensile or compressive strains)

### The formation of the secondary cell wall is sensitive to the dose (number) of bending

<figure><img src="image_24.png" /></figure>

18.6%

Proportion
of fibers with
G-layer
<

<figure><img src="image_25.png" /></figure>

31.9%

<figure><img src="image_26.png" /></figure>

G-layer thickness: 1.16µm

G-layer
thickness
<

<figure><img src="image_27.png" /></figure>

G-layer thickness: 1.54µm

⇒ **DOSE-EFFECT**

### REFERENCES

(1) Coutand C. and Moulia B. (2000). *Journal of Experimental Botany* **51**(352): 1825-1842.; (2) Coutand C., Martin L., Leblanc-Fournier N., Decourteix M., Julien J.L. and Moulia B. (2009). *Plant Physiology* **151**: 1-10.; (3) Telewski FW (1989) *Tree Physiology* **5**: 113-121.; (4) Telewski FW, Jaffe MJ (1986) *Physiologia Plantarum* **66**: 219-226.; (5) Kern KA, Ewers FW, Telewski FW, Koehler L (2005) *Tree physiology* **25**: 1243-1251.