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| Rabaey, D.; Lens, F.; Huysmans, S.; Smets, E.; Jansen, S.. |
| Recent micromorphological observations of angiosperm pit membranes have extended the number and range of taxa with pseudo-tori in tracheary elements. This study investigates at ultrastructural level (TEM) the development of pseudo-tori in the unrelated Malus yunnanensis, Ligustrum vulgare, Pittosporum tenuifolium, and Vaccinium myrtillus in order to determine whether these plasmodesmata associated thickenings have a similar developmental pattern across flowering plants. At early ontogenetic stages, the formation of a primary thickening was observed, resulting from swelling of the pit membrane in fibre-tracheids and vesselelements. Since plasmodesmata appear to be frequently, but not always, associated with these primary pit membrane thickenings, it remains... |
| Tipo: Article / Letter to the editor |
Palavras-chave: Ontogeny; Pseudo-torus; Tracheary element; Pit membrane; Bordered pit; Wood ultrastructure; 42.56. |
| Ano: 2008 |
URL: http://www.repository.naturalis.nl/record/430078 |
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| Rabaey, D.; Huysmans, S.; Lens, F.; Smets, E.; Jansen, S.. |
| Recent studies on the functional significance of pit membranes in water conducting cells have renewed general interest in their micromorphology. At least two types of pit membrane thickenings have been described in angiosperm families, i.e. genuine tori and pseudo-tori. This study explores the distribution and morphology of pit membrane thickenings in 69 species and 23 genera within Oleaceae using light and electron microscopy. Torus-bearing pit membranes are confirmed for Osmanthus, and new records are reported for Chionanthus retusa, Picconia azorica, and P. excelsa, but not for the other species studied of Chionanthus. This infrageneric variation suggests that tori represent a plastic feature that has evolved more than once within the family as the... |
| Tipo: Article / Letter to the editor |
Palavras-chave: Electron microscopy; Pit aperture; Pit membrane; Plasmodesmata; Pseudo-torus; Torus; Tracheid; Vessel element; 42.56. |
| Ano: 2008 |
URL: http://www.repository.naturalis.nl/record/429536 |
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| Jansen, S.; Sano, Y.; Choat, B.; Rabaey, D.; Lens, F.; Dute, R.R.. |
| The micromorphology of pits in tracheary elements was examined in 35 species representing 29 genera of Rosaceae and related families to evaluate the assumption that angiosperm pits are largely invariant. In most Rosaceae, pit membranes between fibers and tracheids frequently appear to have amorphous thickenings with an irregular distribution. Although these structures are toruslike under the light microscope, observations by electron microscopy illustrate that they represent ‘‘pseudotori’’ or plasmodesmata-associated thickenings. These thickenings frequently extend from the periphery of the pit membrane and form a cap-like, hollow structure. Pseudotori are occasionally found in few Elaeagnaceae and Rhamnaceae and appear to be related to species with... |
| Tipo: Article / Letter to the editor |
Palavras-chave: Fiber; Pit; Pit membrane; Pseudotorus; Rosaceae; Rosales; Torus; Tracheid; 42.58. |
| Ano: 2007 |
URL: http://www.repository.naturalis.nl/record/423505 |
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| Rabaey, D.; Lens, F.; Smets, E.; Janssen, S.. |
| Background and Aims Intervascular pit membranes were examined within Ericales to determine the distribution and structure of torus-like thickenings. Methods Forty-nine species representing 12 families of the order Ericales were investigated using light, scanning and transmission electron microscopy. They were compared with four species of Oleaceae to determine the true nature of the thickenings. Key Results Pit membranes with torus-like thickenings were observed in seven species of Ericaceae and were found to be amorphous, plasmodesmata-associated structures with an irregular distribution. These pseudo-tori show major differences compared with true tori with respect to their distribution and ultrastructure. Genuine tori, which are strongly correlated... |
| Tipo: Article / Letter to the editor |
Palavras-chave: Ericaceae; Ericales; Oleaceae; Pit membrane; Plasmodesmata; Pseudo-torus; Torus; Tracheary elements. |
| Ano: 2006 |
URL: http://www.repository.naturalis.nl/record/407321 |
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