Imaging the dynamic deposition of cell wall polymer in xylem and phloem in Populus × euramericana

Abstract

Both G units and S units deposited in the whole lignification process of xylem fiber. The topochemical variations in newly formed xylem and phloem of Populus × euramericana were investigated by combined microscopic techniques. During xylem formation, earlier cell wall deposition in vessel and afterwards in the neighboring fiber was observed in situ. Raman images in xylem fiber emphasized that cell wall deposition was an ordered process which lignification started in cell corner following carbohydrates deposition. Higher deposition speed of carbohydrates was revealed at the beginning of the cell wall differentiation, and the syringyl (S) units deposition was more pronounced compared with guaiacyl (G) units at the earlier stage of lignification. The comparative analysis of cell wall composition in phloem fiber indicated that phloem formed earlier than xylem and the distribution of lignin monomers varied significantly with phloem fiber location. Furthermore, an interesting phenomenon was found that the outermost phloem fiber near the periderm displayed a multilayered structure with alternating broad and narrow layer, and the broad lamellae showed higher concentration of carbohydrates and S lignin. The cytological information including cell wall composition and lignin structure of xylem and phloem might be helpful to understand the wood growth progresses and facilitate utilization of woody plants.

Analysis of Cellulose and Lignocellulose Materials by Raman Spectroscopy: A Review of the Current Status

“…Confocal Raman imaging [12] where analysis is carried out at diffraction-limited spatial resolution level to obtain information on the chemical constituents and their distributions within the sample has been used quite widely to investigate tissues of various plants (e.g., stem, leaves, and roots). Additionally, different vascular cell types (e.g., xylem and phloem) in woody and herbaceous plants have been studied by this spectroscopy technique [59]. Plant cell walls are highly complex structures and during growth and development phase, undergo changes.…”

“…Plant cell walls are highly complex structures and during growth and development phase, undergo changes. For poplar wood xylem and phloem, the kind of information that can be generated is shown in Figure 5 [59]. Another area where Raman imaging has played a role is in the area of nanocellulose composites [31] where the technique has allowed a better understanding of the cellulose/polymer interface.…”

Infrared and Raman spectra of lignin substructures: Dibenzodioxocin

“…In the plant cell wall, it can be distinguished from other constituents by IR and Raman microscopy . Published work has mainly focused on the estimation of ethylenic residues (cinnamyl alcohols and aldehydes) and determination of S/G ratios in lignin. However, these are only selected features of the lignin polymer; for example, cinnamaldehyde end groups only account for about 4% of lignin substructures .…”

Transcriptomics and Proteomics Reveal the Cellulose and Pectin Metabolic Processes in the Tension Wood (Non-G-Layer) of Catalpa bungei

“…And the peak value of TW was significantly lower than that of OW and NW in the wavenumbers 900~1800 cm −1 and 2000~3200 cm −1 . In the Raman spectra, the bands observed in the 2800~3000 cm −1 range could be assigned to the C-H stretching vibrations of -CH, -CH2, -CH3 groups [25][26][27][28][29], in this region all cell walls compounds contributed to the Raman signal. And the peak of TW was lower than that of OW and NW in the range of this wavelength.…”