Abstract
The ultrastructure of wood fibres has been studied incambial cells, differentiating fibres and mature xylem fibres,using the Rapid-Freeze Deep-Etching (RFDE) technique combinedwith transmission electron- and epifluorescence microscopy.Pectin distribution in mature wood fibres, and in fibres duringdevelopment, have been studied by immunolabelling. Furthermore,lignin polymerisation has been studied by13C-CP/MAS NMR. With these modern techniques newfindings regarding the ultrastructure of wood fibres have beenfound. Lignin is one of the major components in mature wood andis an obstacle in ultrastructural studies of the other woodpolymers (cellulose, hemicellulose and pectin). Therefore,fibres have been studied before, during and afterlignification, and after delignification, in order to obtaininformation and draw conclusions on the structure of fullylignified fibres. The lignification process has also beenstudied. The RFDE-technique revealed an extensive fibrillarnetwork in both the primary and secondary cell wall. Thefibrillar structure was visible both in unlignified andlignified cell walls indicating that lignin is deposited ontothe cellulose/hemicellulose fibrils in the cell wall, and notas a continuous matrix. The network in the primary wall showedextensive crosslinking. The crosslinks in the primary wallsuggestively consists of pectin and hemicelluloses. Crosslinkswere also found in secondary walls, and they are probably ofhemicellulose origin. An extensive network structure was alsopresent in the unlignifiedmiddle lamella. This network wasclearly different from the cell wall polymer network andprobably consists mainly of pectin. The fully lignified middlelamella is compact with no visible pores. After chloritedelignification an underlying network was revealed in themiddle lamella. This network was thin, irregular and differentfrom any structures found in the unlignified middle lamella orcell wall, and it is suggested to be composed ofhemicellulose/cellulose.Pectin is a polymer whose chemistry and distribution isdifficult to study in native wood. However, byimmunolocalisation using monoclonal antibodies (JIM5 and JIM7),pectin, acidic and methyl esterifed polygalacturonan,distribution has been revealed. Pectin was found in thecompound middle lamella, ray cell wall and pit membrane inpine, spruce, birch and aspen. The distribution pattern indifferent wood species seemed to vary. Birch showed only smallamounts of acidic pectin, and in aspen both methylated andacidic pectin were concentrated to the middle lamella cellcorners. Spruce showed a very similar distribution pattern topine.A method to produce specifically13C-labelled polylignols in natural wood tissue(cell wall-DHP) has been developed, with the intention to usethe cell wall-DHP complex in structural studies of thelignification process, as well as in studies of ligninreactions in technical applications. The13C-enriched cell wall-DHP complex has shown to be agood system to mimic the natural lignification process, and bymaking difference spectra of unenriched and13C enriched samples, the bond frequencies involvingthe specifically13C-labelled atom can be determined quantitativelyby13C- NMR.Keywords: cambium, differentiating xylem, xylem,rapid-freeze deep-etching technique, immunolocalisation, JIM5,JIM7,13C-CP/MAS NMR, DHP, ultrastructure, microfibrils,crosslinks, middle lamella, cell wall,Pinus sylvestris,Picea abies,Betula pubescens,Populus tremula,Pinus thunbergii, lignin, pectin, hemicellulose,cellulose, lignification
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Claims 14
Claim · model-written summary
The primary and secondary cell walls contained extensive fibrillar networks.
- Outcome
- extensive fibrillarnetworke0
Not reportedTaxon
Verbatim
e0“The RFDE-technique revealed an extensive fibrillarnetwork in both the primary and secondary cell wall.”
Claim · model-written summary
The fibrillar structure occurred in unlignified and lignified walls, suggesting lignin deposits onto fibrils.
- Outcome
- lignin is deposited ontothe cellulose/hemicellulose fibrilse0
- Qualifier
- fibrillar structure was visible both in unlignified andlignified cell wallse0
Not reportedTaxon
Verbatim
e0“Thefibrillar structure was visible both in unlignified andlignified cell walls indicating that lignin is deposited ontothe cellulose/hemicellulose fibrils in the cell wall, and notas a continuous matrix.”
Claim · model-written summary
The primary wall network had extensive crosslinking.
- Outcome
- extensive crosslinkinge0
Not reportedTaxon
Verbatim
e0“The network in the primary wall showedextensive crosslinking.”
Claim · model-written summary
The primary wall crosslinks were suggested to consist of pectin and hemicelluloses.
Not reportedTaxon
Verbatim
e0“The crosslinks in the primary wallsuggestively consists of pectin and hemicelluloses.”
Claim · model-written summary
Secondary wall crosslinks were found and probably originated from hemicellulose.
Not reportedTaxon
Verbatim
e0“Crosslinkswere also found in secondary walls, and they are probably ofhemicellulose origin.”
Claim · model-written summary
The unlignified middle lamella contained an extensive network likely composed mainly of pectin.
Not reportedTaxon
Verbatim
e0“An extensive network structure was alsopresent in the unlignifiedmiddle lamella. This network wasclearly different from the cell wall polymer network andprobably consists mainly of pectin.”
Claim · model-written summary
The fully lignified middle lamella was compact and had no visible pores.
- Outcome
- compact with no visible porese0
Not reportedTaxon
Verbatim
e0“The fully lignified middlelamella is compact with no visible pores.”
Claim · model-written summary
Chlorite delignification revealed a thin irregular network in the middle lamella, suggested to contain hemicellulose and cellulose.
Not reportedTaxon
Verbatim
e0“After chloritedelignification an underlying network was revealed in themiddle lamella. This network was thin, irregular and differentfrom any structures found in the unlignified middle lamella orcell wall, and it is suggested to be composed ofhemicellulose/cellulose.”
Claim · model-written summary
Pectin occurred in compound middle lamella, ray wall and pit membrane in pine, spruce, birch and aspen.
Verbatim
e0“Pectin was found in thecompound middle lamella, ray cell wall and pit membrane inpine, spruce, birch and aspen.”
Claim · model-written summary
Birch had small amounts of acidic pectin.
Verbatim
e0“Birch showed only smallamounts of acidic pectin”
Claim · model-written summary
In aspen, methylated and acidic pectin concentrated in middle lamella corners.
Verbatim
e0“in aspen both methylated andacidic pectin were concentrated to the middle lamella cellcorners.”
Claim · model-written summary
Spruce had a pectin distribution pattern similar to pine.
PiceaOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Spruce showed a very similar distribution pattern topine.”
Claim · model-written summary
A method produced specifically labelled polylignols in natural wood tissue.
- Outcome
- specifically13C-labelled polylignolse0
Not reportedTaxonValue
Verbatim
e0“A method to produce specifically13C-labelled polylignols in natural wood tissue(cell wall-DHP) has been developed”
Claim · model-written summary
The enriched cell wall DHP complex mimicked natural lignification and enabled quantitative determination of labelled atom bond frequencies.
- Outcome
- good system to mimic the natural lignification processe0
- Comparator
- natural lignification processe0
Not reportedTaxon
Verbatim
e0“The13C-enriched cell wall-DHP complex has shown to be agood system to mimic the natural lignification process, and bymaking difference spectra of unenriched and13C enriched samples, the bond frequencies involvingthe specifically13C-labelled atom can be determined quantitativelyby13C- NMR.”