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Accueil > Scientific events > Past seminars

Seminar of the UGSF - 22nd of September 2017

WEEKLY SEMINAR OF THE UGSF

"Characterization of plant cell wall polymers with infra-red vibrational microscopy"

Speaker :
Anne-Sophie BLERVACQ, C9, Bureau 226.

From the team "Fibres végétales"

They will be here : Isabelle De Waele (IGR, head of the platform FT-IR, LASIR, C8), Myriam Moreau (IGE, head of the platform RAMAN, LASIR, C5) pour les éventuelles questions très techniques.

Resume :

Plant cell walls can be divided into two main categories according to the relative proportion of their constitutive polymers : cellulose-rich walls such as those found in flax and hemp bast fibers (textile fibers), and lignin-rich ones found in wood (secondary xylem). Cell wall differentiation occurs progressively during plant cell growth but the final cell wall quality also depends on environmental conditions.

We investigated the cell wall composition of six different cell types from the stem of flax (Linum usitatissimum) plants using middle infra-red microscopy (FT-IR, Brucker Hyperion). Spectra were collected from stem cross-sections within the cell wall-characteristic fingerprint range (1,800-900 cm-1). Data were treated through chemiometry (MatLab software) and PCA allowed us to identify specific peaks that (i) describe the dynamics of cell wall differentiation during optimal growth, and (ii) identify differentiated cell types within the xylem. Focal-Plan Array (FPA) analyses were performed on identified peaks to produce cell/tissue chemical imaging. The same approach was subsequently used to undertake a detailed investigation of the effect of a gravitational stress on cell wall composition. While this stress is known to provoke alterations in bast fiber morphology and the appearance of a gelatinous layer (G-Layer) within xylem vessels, a detailed analyses of cell wall polymer changes is currently lacking.

If FT-IR analyses or FPA chemical imaging are now established as possible for flax (after paraffin embedding). PCA allow us to determine 5 significant windows that could illustrate growth dynamics, but also stress impacts : 1,296-1,188 cm-1 cellulose+xylan, 1,440-1,401 cm-1 hemicelluloses, 1,525-1,483 cm-1 pectin, 1,692-1,562 cm-1 xylan+pectin, 1,760-1,692 cm-1 lignin. Cell wall polymer changes during the stress concerned particularly, mannan (1,065 cm-1), pectin (1,117 cm-1), microcristalline cellulose (1,169 cm-1) and lignin (1,761 cm-1). If such windows highlighted the significant differences between control, tension, opposite bast fibers and G-layer (in vessels), two peaks were common in control and G-layer (but not with tension and opposite fibers) : 1,218-1,190 cm-1 (CH vibration, CH2-rocking vibration at C6 ; cellulose, xylan, xyloglucan), and 1,347-1,328 cm-1 (cellulose, xyloglucan).

In order to obtain a more detailed picture of the stress-induced modifications in plant cell wall polymers we used Raman confocal microscopy to collect additional vibrational spectral information in the 940-300 cm-1 range and to increase imaging resolution. PCA analyses led us to identify the same windows as in FT-IR, but complete them with 378-405 cm-1 cellulose (symmetric ring deformation), 430-460 cm-1 xylan (d(COC), d(CCC) ring defromation) and 817-850 cm-1 pectin.
Both FT-IR and Raman vibrational microscopies are powerful and convenient techniques that allow detailed spatial information to be obtained on plant cell wall dynamics and plasticity , and provide complementary information to chemical analyses an

On the Friday 22 of september 2017 à 11.00 at the UGSF- Salle André Verbert