Deposition and organisation of cell wall polymers during maturation of poplar tension wood by FTIR microspectroscopy
To advance our understanding of the formation of tension wood, we investigated the macromolecular arrangement in cell walls by Fourier transform infrared microspectroscopy (FTIR) during maturation of tension wood in poplar (Populus tremula x P. alba, clone INRA 717-1B4). The relation between changes in composition and the deposition of the G-layer in tension wood was analysed. Polarised FTIR measurements indicated that in tension wood, already before G-layer formation, a more ordered structure of carbohydrates at an angle more parallel to the fibre axis exists. This was clearly different from the behaviour of opposite wood. With the formation of the S2 layer in opposite wood and the G-layer in tension wood, the orientation signals from the amorphous carbohydrates like hemicelluloses and pectins were different between opposite wood and tension wood. For tension wood, the orientation for these bands remains the same all along the cell wall maturation process, probably reflecting a continued deposition of xyloglucan or xylan, with an orientation different to that in the S2 wall throughout the whole process. In tension wood, the lignin was more highly oriented in the S2 layer than in opposite wood.
KeywordsFTIR microscopy Maturation Orientation Polarisation Polymers Populus tremula x P. alba Tension wood
Fourier transform infrared
Mercury cadmium telluride
Relative orientation absorbance
Secondary cell wall layer, first layer
Secondary cell wall layer, middle layer
Secondary cell wall layer, third layer
This work was supported by COST Action FP0802 through the Short Term Scientific Mission (STSM) funding for Shan Shan Chang. Shan Shan Chang benefits a fellowship from the Scientific Council of Montpellier University. Lennart Salmén received support from the Wallenberg Wood Science Center (WWSC). The authors wish to thank Gilles Pilate and Françoise Laurans (AGPF, Genobois technical platform, INRA Orleans, France) for providing the wood samples and for making the stained sections presented in Fig. 1, Jasna Stevanic Srndovic and Joanna Hornatowska (Innventia Stockholm, Sweden) for their assistance during FTIR experiment. Thanks are also extended to Cécile Barron (INRA Montpellier, France) and Antonio Pizzi (ENSTIB-LERMAB Epinal, France) for critical discussions. Part of this work was performed in the framework of the project “StressInTrees” funded by the French National Research Agency (ANR-12-BS09-0004).
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