scholarly journals The Nature of Reaction Wood III. Cell Division and Cell Wall Formation in Conifer Stems

1952 ◽  
Vol 5 (4) ◽  
pp. 385 ◽  
Author(s):  
ABW Ardrop ◽  
HE Dadswell
Keyword(s):  
Cell Wall ◽  
Cell Division ◽  
Secondary Wall ◽  
Compression Wood ◽  
Normal Wood ◽  
Reaction Wood ◽  
Primary Wall ◽  
Wall Formation ◽  
Tracheid Length ◽  
Secondary Wall Formation

Cell division, the nature of extra-cambial readjustment, and the development of the secondary wall in the tracheids of conifer stems have been investigated in both compression wood and normal wood. It has been shown that the reduction in tracheid length, accompanying the development of compression wood and, in normal wood, increased radial growth after suppression, result from an increase in the number of anticlinal divisions in the cambium. From observations of bifurcated and otherwise distorted cell tips in mature tracheids, of small but distinct terminal canals connecting the lumen to the primary wall in the tips of mature tracheids, and of the presence of only primary wall at the tips of partly differentiated tracheids, and from the failure to observe remnants of the parent primary walls at the ends of differentiating tracheids, it has been concluded that extra-cambial readjustment of developing cells proceeds by tip or intrusive growth. It has been further concluded that the development of the secondary wall is progressive towards the cell tips, on the bases of direct observation of secondary wall formation in developing tracheids and of the increase found in the number of turns of the micellar helix per cell with increasing cell length. The significance of this in relation to the submicroscopic organization of the cell wall has been discussed. Results of X-ray examinations and of measurements of� tracheid length in successive narrow tangential zones from the cambium into the xylem have indicated that secondary wall formation begins before the dimensional changes of differentiation are complete.

The structure of the cell wall in lignifield collenchyma of Eryngium sp. (Umbelliferae)

1969 ◽  
Vol 17 (2) ◽  
pp. 229 ◽  
Author(s):  
AB Wardrop
Keyword(s):  
Cell Wall ◽  
Cell Division ◽  
Cell Differentiation ◽  
Secondary Wall ◽  
Indoleacetic Acid ◽  
Cellulose Microfibrils ◽  
Cell Axis ◽  
Wall Formation ◽  
Microfibril Orientation ◽  
Secondary Wall Formation

In Eryngium vesiculosum and E. rostratum, the leaf collenchyma is characterized by the development of a lignified secondary wall in the final stages of cell differentiation. The collenchyma wall is rich in pectic substances which are distributed uniformly. In the outer limiting region of the collenchyma wall the microfibril orientation is random and this structure is considered to be the wall formed at cell division. The collenchyma wall consists of six to eight layers in which the microfibrils are alternately transversely and longitudinally oriented. Each layer consists of a number of lamellae of microfibrils. In the secondary lignified wall the cellulose microfibrils are arranged helically, the direction of their orientation making an angle of 40-45° to the cell axis. Excised leaf segments showed greatest elongation in solutions of glucose and 3-indoleacetic acid, when the collenchyma walls were thin, and no elongation occurred in segments in which secondary wall formation had commenced. In radial sections layers of transversely oriented microfibrils could not be seen distant from the lumen although discontinuities in wall texture were apparent. Layers of transversely oriented microfibrils could be seen adjacent to the lumen. It is suggested that reorientation of layers of initially transversely oriented microfibrils takes place during elongation of the cells.

The nature of reaction wood. IV. Variations in cell wall organization of tension wood fibres

1955 ◽  
Vol 3 (2) ◽  
pp. 177 ◽  
Author(s):  
AB Wardrop ◽  
HE Dadswell
Keyword(s):  
Cell Wall ◽  
Tension Wood ◽  
Secondary Wall ◽  
Degree Of Crystallinity ◽  
Tropical Species ◽  
Normal Wood ◽  
Reaction Wood ◽  
Gelatinous Layer ◽  
Wood Fibres ◽  
Cell Wall Organization

The cell wall organization, the cell wall texture, and the degree of lignification of tension wood fibres have been investigated in a wide variety of temperate and tropical species. Following earlier work describing the cell wall structure of tension wood fibres, two additional types of cell wall organization have been observed. In one of these, the inner thick "gelatinous" layer which is typical of tension wood fibres exists in addition to the normal three-layered structure of the secondary wall; in the other only the outer layer of the secondary wall and the thick gelatinous layer are present. In all the tension wood examined the micellar orientation in the inner gelatinous layer has been shown to be nearly axial and the cellulose of this layer found to be in a highly crystalline state. A general argument is presented as to the meaning of differences in the degree, of crystallinity of cellulose. The high degree of crystallinity of cellulose in tension wood as compared with normal wood is attributed to a greater degree of lateral order in the crystalline regions of tension wood, whereas the paracrystalline phase is similar in both cases. The degree of lignification in tension wood fibres has been shown to be extremely variable. However, where the degree of tension wood development is marked as revealed by the thickness of the gelatinous layer the lack of lignification is also most marked. Severity of tension wood formation and lack of lignification have also been correlated with the incidence of irreversible collapse in tension wood. Such collapse can occur even when no whole fibres are present, e.g. in thin cross sections. Microscopic examination of collapsed samples of tension wood has led to the conclusion that the appearance of collapse in specimens containing tendon wood can often be attributed in part to excessive shrinkage associated with the development of fissures between cells, although true collapse does also occur. Possible explanations of the irreversible shrinkage and collapse of tension wood fibres are advanced.

scholarly journals Engineering the Oryza sativa cell wall with rice NAC transcription factors regulating secondary wall formation

2013 ◽  
Vol 4 ◽  
Author(s):  
Kouki Yoshida ◽  
Shingo Sakamoto ◽  
Tetsushi Kawai ◽  
Yoshinori Kobayashi ◽  
Kazuhito Sato ◽  
...  
Keyword(s):  
Cell Wall ◽  
Oryza Sativa ◽  
Transcription Factors ◽  
Secondary Wall ◽  
Nac Transcription Factors ◽  
Wall Formation ◽  
Secondary Wall Formation

Ultrastructural observations on Helvellaceae (Pezizales, Ascomycetes). IV. Ascospore ontogeny in selected species of Gyromitra subgenus Discina

1990 ◽  
Vol 68 (2) ◽  
pp. 317-328 ◽  
Author(s):  
James W. Kimbrough ◽  
Chi-Guang Wu ◽  
Jack L. Gibson
Keyword(s):  
Key Words ◽  
Secondary Wall ◽  
Spore Wall ◽  
Wall Material ◽  
Wall Structure ◽  
Primary Wall ◽  
Spore Ornamentation ◽  
Wall Formation ◽  
Secondary Wall Formation ◽  
Definition Of

The ultrastructure of ascospore ontogeny and spore wall microchemistry are described in three sessile, discoid species of Gyromitra previously placed in Discina. Silver proteinate and barium permanganate were used as poststains to enhance the definition of various wall layers and spore organelles. Early stages of ascosporogenesis and primary wall formation are similar to those described in other species of Pezizales. Secondary wall formation, which results in characteristic spore ornamentation, is similar in Gyromitra brunnea, Gyromitra leucoxantha, and Gyromitra perlata. Mature spores of these species differ in the size and shape of translucent lacunae within the secondary wall, and in the morphology of apiculi. The lacunae originate through blebbing of primary wall material through the epispore into the secondary wall, resulting in the isolation of electron-translucent primary wall clumps within the electron-dense secondary wall. These and other ultrastructural observations of apothecial tissues support the maintenance of the Helvellaceae (sensu lato) to include taxa of the tribes Helvelleae, Discineae, and Rhizineae. Phylogenetic linkages of these taxa to other families of Pezizales are suggested. Key words: ascosporogenesis, ascospore wall structure and microchemistry, discomycete systematics and phylogeny.

Secondary walls in hyaline cells of Sphagnum

2004 ◽  
Vol 52 (2) ◽  
pp. 243 ◽  
Author(s):  
Celeste L. Kremer ◽  
Andrew N. Drinnan
Keyword(s):  
Cell Wall ◽  
Cell Differentiation ◽  
Secondary Wall ◽  
Secondary Cell Wall ◽  
Higher Plants ◽  
Cell Formation ◽  
Primary Wall ◽  
Random Arrays ◽  
Secondary Wall Formation ◽  
Hyaline Cell

The cytoskeleton and ultrastructural events associated with cell differentiation and secondary cell wall and pore formation in hyaline cells of Sphagnum are investigated. Microtubules reorient from random arrays in undifferentiated hyaline cells to transverse arrays in elongating cells. Once cells are fully elongated, broad bands of microtubules aggregate into a spiral that predicts the site of secondary cell wall deposition. The secondary wall has a similar fibrillar composition to the primary wall. After the secondary wall is deposited, the thin primary wall covering the pore breaks down, usually by cell-wall degradation at the centre of the pore and around its margin. Finally, the hyaline cell undergoes cytoplasmic degeneration. The orientation of microtubules associated with hyaline-cell formation and secondary cell wall patterning resembles ultrastructural development in tracheary elements of higher plants. The similarities in cytoskeletal arrays during cell differentiation and secondary-wall formation suggest a fundamental pathway of development shared by bryophytes and higher plants.

Ultrastructural observations on Helvellaceae (Pezizales). Ascosporogenesis of selected species of Helvetia

1988 ◽  
Vol 66 (4) ◽  
pp. 771-783 ◽  
Author(s):  
Jack L. Gibson ◽  
James W. Kimbrough
Keyword(s):  
Early Development ◽  
Secondary Wall ◽  
Primary Wall ◽  
Spore Ornamentation ◽  
Wall Formation ◽  
Wall Deposition ◽  
Secondary Wall Formation

The ultrastructure of ascosporogenesis including observations on spore delimitation, primary wall deposition, and formation of the secondary wall is examined in three species of the genus Helvella. The double membranes delimiting the spores and the ascus plasmalemma stain identically with silver proteinate poststain. Primary wall formation is similar in all species examined, although very early development was observed only for H. macropus. Secondary wall formation, which results in the characteristic spore ornamentation, appears to be quite similar for the three species. In addition, observations are made on the structure and origin of the epispore and on cytological details of the epiplasm and sporoplasm relating to spore ontogeny.

scholarly journals The Nature of Reaction Wood II. The Cell Wall Organization of Compression Wood Tracheids

1950 ◽  
Vol 3 (1) ◽  
pp. 1 ◽  
Author(s):  
AB Wardrop ◽  
HE Dadswell
Keyword(s):  
Cell Wall ◽  
Pinus Radiata ◽  
Compression Wood ◽  
Large Angle ◽  
Reaction Wood ◽  
Micellar Structure ◽  
X Ray ◽  
Similar Length ◽  
Tracheid Length ◽  
Cell Wall Organization

Optical and X-ray methQds have been used in the examinatiQn Qf the secQndarycell wall Qf cQmpressiQn WQQd tracheids from a number Qf species QfgymnDsperms.By these methQds it has been shQwn that the cell wall Qf CQmpressiQn WQQd tracheidscDnsists Qf two. layers. In the Quter layer the micelles are inclined at a large angle 'to. the lQngitudinal axis Qf the tracheid, while in the inner layer the micelles areinclined at a relatively smaller angle. In the inner Df the two. layers there exist radialdiscQntinuities in the spiral micellar structure, which are visible as IQngitudinal striatiQnsin the cell wall. These discQntinuities also. aCCQunt for the radial distributiQn Qflignin which is observed in transverse sectiQns Qf cQmpressiQn WQQd tracheids. Bydetermining the average tracheid length Qf the last-fDrmed late WQod in the variQusgrowth rings Df several eccentric stems Qf Pinus radiata D.DQn it has been shDwn thatthe tracheids Qf cQmpressiQn WQQd are appreciably shQrter than WQuld be the case ifno. cQmpressiQn WQQd were present. A study Qf the change in micellar QrientatiQn withchange in tracheid length has indicated that the angle Qf micellar QrientatiQn in CQmpressiQnWQQd tracheids dQes nQt differ signific(mtly frQm that existing in nQrmalWQQd tracheids Qf similar length. In so. far as the prQperties Qf WQQd are determinedby cell wall QrganizatiQn, it is cQncluded that cQmparisQns between cQmpressiQn WQDdand normal WQQd shQuld be made Qn material Qf the same tracheid length and spiralQrganizatiDn. It is suggested that bQth the reductiQn in tracheid length and eccentricradial growth in stems cQntaining cQmpressiQn WQQd are to. be attributed to. an increasein the number Df bDth transverse and tangential lQngitudinal divisiQns Qf thefusifQrm initials Qf the cambium.

Changes in cell wall organization resulting from surface growth in parenchyma of oat coleoptiles

1958 ◽  
Vol 6 (2) ◽  
pp. 89 ◽  
Author(s):  
AB Wardrop ◽  
J Cronshaw
Keyword(s):  
Cell Wall ◽  
Outer Surface ◽  
Secondary Wall ◽  
Surface Growth ◽  
Extension Growth ◽  
Primary Wall ◽  
Cell Wall Formation ◽  
Wall Formation ◽  
Cell Wall Organization ◽  
Mechanism Of Growth

The primary walls present during the phase of extension growth in oat coleoptiles possess an almost transverse microfibril orientation on their inner surfaces but on the outer surface the microfibrils are considerably disoriented from this direction, which is consistent with the concept of multi-net mechanism of growth. Coleoptile segments grown at 2°C to depress cell wall formation show no difference in orientation on their inner and outer surfaces; this is also considered to be consistent with the multi-net mechanism. It is shown that the longitudinal ribs of microfibrils present at the cell corners, and hitherto referred to as secondary thickening, are on the outer surface of the cell wall and are considered to arise from a disorientation of microfibrils as a result of multi-net growth. As a result of this microfibril disorientation there is a tendency for the pit fields to be reduced in area. After surface growth has ceased a secondary wall is formed with a well-defined helical organization distinctly different from that of the primary wall. The implications of these results in terms of previous investigations are discussed.

scholarly journals MYB Transcription Factors and Its Regulation in Secondary Cell Wall Formation and Lignin Biosynthesis during Xylem Development

2021 ◽  
Vol 22 (7) ◽  
pp. 3560
Author(s):  
Ruixue Xiao ◽  
Chong Zhang ◽  
Xiaorui Guo ◽  
Hui Li ◽  
Hai Lu
Keyword(s):  
Cell Wall ◽  
Transcription Factors ◽  
Secondary Wall ◽  
Secondary Cell Wall ◽  
Lignin Biosynthesis ◽  
Cell Wall Formation ◽  
Long Distance ◽  
Secondary Cell Wall Formation ◽  
Myb Transcription Factors ◽  
Wall Formation

The secondary wall is the main part of wood and is composed of cellulose, xylan, lignin, and small amounts of structural proteins and enzymes. Lignin molecules can interact directly or indirectly with cellulose, xylan and other polysaccharide molecules in the cell wall, increasing the mechanical strength and hydrophobicity of plant cells and tissues and facilitating the long-distance transportation of water in plants. MYBs (v-myb avian myeloblastosis viral oncogene homolog) belong to one of the largest superfamilies of transcription factors, the members of which regulate secondary cell-wall formation by promoting/inhibiting the biosynthesis of lignin, cellulose, and xylan. Among them, MYB46 and MYB83, which comprise the second layer of the main switch of secondary cell-wall biosynthesis, coordinate upstream and downstream secondary wall synthesis-related transcription factors. In addition, MYB transcription factors other than MYB46/83, as well as noncoding RNAs, hormones, and other factors, interact with one another to regulate the biosynthesis of the secondary wall. Here, we discuss the biosynthesis of secondary wall, classification and functions of MYB transcription factors and their regulation of lignin polymerization and secondary cell-wall formation during wood formation.

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