A vessel element or vessel member (also called a xylem vessel)[1] is one of the cell types found in xylem, the water conducting tissue of plants. Vessel elements are found in most angiosperms (flowering plants) but absent from most gymnosperms such as conifers. Vessel elements are the main feature distinguishing the "hardwood" of angiosperms from the "softwood" of conifers.
SEM image (top) and Transmission Light Microscope image (bottom) of vessel elements in Oak
Xylem is the tissue in vascular plants that conducts water (and substances dissolved in it) upwards from the roots to the shoots. Two kinds of cell are involved in xylem transport: tracheids and vessel elements.[2][3][4] Vessel elements are the building blocks of vessels, the conducting pathways that constitute the major part of the water transporting system in flowering plants. Vessels form an efficient system for transporting water (including necessary minerals) from the root to the leaves and other parts of the plant.
Stained Xylem Vessel in Red/Orange (x400 magnification)
In secondary xylem – the xylem that is produced as a stem thickens rather than when it first appears – a vessel element originates from the vascular cambium. A long cell, oriented along the axis of the stem, called a "fusiform initial", divides along its length forming new vessel elements. The cell wall of a vessel element becomes strongly "lignified", i.e. it develops reinforcing material made of lignin. The side walls of a vessel element have pits: more or less circular regions in contact with neighbouring cells. Tracheids also have pits, but only vessel elements have openings at both ends that connect individual vessel elements to form a continuous tubular vessel. These end openings are called perforations or perforation plates. They have a variety of shapes: the most common are the simple perforation (a simple opening) and the scalariform perforation (several elongated openings in a ladder-like design). Other types include the foraminate perforation plate (several round openings) and the reticulate perforation plate (a net-like pattern, with many openings).
At maturity, the protoplast – the living material of the cell – dies and disappears, but the lignified cell walls persist. A vessel element is then a dead cell, but one that still has a function, and is still being protected by surrounding living cells.
Evolutionary significanceedit
The presence of vessels in xylem has been considered to be one of the key innovations that led to the success of the flowering plants. It was once thought that vessel elements were an evolutionary innovation of flowering plants, but their absence from some basal angiosperms and their presence in some members of the Gnetales suggest that this hypothesis must be re-examined; vessel elements in Gnetales may not be homologous with those of angiosperms, or vessel elements that originated in a precursor to the angiosperms may have been subsequently lost in some basal lineages (e.g., Amborellaceae, Trochodendraceae, and Winteraceae), described by Arthur Cronquist as "primitively vesselless". Cronquist considered the vessels of Gnetum to be convergent with those of angiosperms.
Vessel-like cells have also been found in the xylem of Equisetum (horsetails), Selaginella (spike-mosses), Pteridium aquilinum (bracken fern), Marsilea and Regnellidium (aquatic ferns), and the enigmatic fossil group Gigantopteridales. In these cases, it is generally agreed that the vessels evolved independently. It is possible that vessels may have appeared more than once among the angiosperms as well.
Niklas, Karl J. (1997) The Evolutionary Biology of Plants. Chicago and London: The University of Chicago Press. ISBN0-226-58082-2.
Schweingruber, F. H. (1990) Anatomie europäischer Hölzer - Anatomy of European woods. Eidgenössische Forschungsanstalt für Wald, Schnee und Landscaft, Birmensdorf (Hrsg.) Haupt, Bern und Stuttgart.
Timonen, Tuuli (2002). Introduction to Microscopic Wood Identification. Finnish Museum of Natural History, University of Helsinki.
Wilson, K.; White, D. J. B. (1986). The Anatomy of Wood: Its Diversity and Variability. London: Stobart & Son Ltd. ISBN0-85442-033-9.
January 01, 1970
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This article includes a list of general references but it lacks sufficient corresponding inline citations Please help to improve this article by introducing more precise citations November 2014 Learn how and when to remove this message A vessel element or vessel member also called a xylem vessel 1 is one of the cell types found in xylem the water conducting tissue of plants Vessel elements are found in most angiosperms flowering plants but absent from most gymnosperms such as conifers Vessel elements are the main feature distinguishing the hardwood of angiosperms from the softwood of conifers SEM image top and Transmission Light Microscope image bottom of vessel elements in Oak Contents 1 Anatomy 2 Evolutionary significance 3 See also 4 References 5 Further referencesAnatomy editXylem is the tissue in vascular plants that conducts water and substances dissolved in it upwards from the roots to the shoots Two kinds of cell are involved in xylem transport tracheids and vessel elements 2 3 4 Vessel elements are the building blocks of vessels the conducting pathways that constitute the major part of the water transporting system in flowering plants Vessels form an efficient system for transporting water including necessary minerals from the root to the leaves and other parts of the plant nbsp Stained Xylem Vessel in Red Orange x400 magnification In secondary xylem the xylem that is produced as a stem thickens rather than when it first appears a vessel element originates from the vascular cambium A long cell oriented along the axis of the stem called a fusiform initial divides along its length forming new vessel elements The cell wall of a vessel element becomes strongly lignified i e it develops reinforcing material made of lignin The side walls of a vessel element have pits more or less circular regions in contact with neighbouring cells Tracheids also have pits but only vessel elements have openings at both ends that connect individual vessel elements to form a continuous tubular vessel These end openings are called perforations or perforation plates They have a variety of shapes the most common are the simple perforation a simple opening and the scalariform perforation several elongated openings in a ladder like design Other types include the foraminate perforation plate several round openings and the reticulate perforation plate a net like pattern with many openings At maturity the protoplast the living material of the cell dies and disappears but the lignified cell walls persist A vessel element is then a dead cell but one that still has a function and is still being protected by surrounding living cells Evolutionary significance editThe presence of vessels in xylem has been considered to be one of the key innovations that led to the success of the flowering plants It was once thought that vessel elements were an evolutionary innovation of flowering plants but their absence from some basal angiosperms and their presence in some members of the Gnetales suggest that this hypothesis must be re examined vessel elements in Gnetales may not be homologous with those of angiosperms or vessel elements that originated in a precursor to the angiosperms may have been subsequently lost in some basal lineages e g Amborellaceae Trochodendraceae and Winteraceae described by Arthur Cronquist as primitively vesselless Cronquist considered the vessels of Gnetum to be convergent with those of angiosperms Vessel like cells have also been found in the xylem of Equisetum horsetails Selaginella spike mosses Pteridium aquilinum bracken fern Marsilea and Regnellidium aquatic ferns and the enigmatic fossil group Gigantopteridales In these cases it is generally agreed that the vessels evolved independently It is possible that vessels may have appeared more than once among the angiosperms as well See also editTracheidReferences edit Vessel plant anatomy Encyclopedia Britannica Retrieved 2021 03 30 Vessels vs Tracheids Similarities and Differences Easy Biology Class 2016 12 12 Retrieved 2021 12 31 Turner Simon Gallois Patrick Brown David 2007 Tracheary element differentiation Annual Review of Plant Biology 58 407 433 doi 10 1146 annurev arplant 57 032905 105236 ISSN 1543 5008 PMID 17472568 Xylem vessel Biology Online 2019 10 07 Retrieved 2021 12 31 Further references editNiklas Karl J 1997 The Evolutionary Biology of Plants Chicago and London The University of Chicago Press ISBN 0 226 58082 2 Schweingruber F H 1990 Anatomie europaischer Holzer Anatomy of European woods Eidgenossische Forschungsanstalt fur Wald Schnee und Landscaft Birmensdorf Hrsg Haupt Bern und Stuttgart Timonen Tuuli 2002 Introduction to Microscopic Wood Identification Finnish Museum of Natural History University of Helsinki Wilson K White D J B 1986 The Anatomy of Wood Its Diversity and Variability London Stobart amp Son Ltd ISBN 0 85442 033 9 Retrieved from https en wikipedia org w index php title Vessel element amp oldid 1217297510, wikipedia, wiki, book, 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