A vessel element is one of the cell types found in xylem In vascular plants, xylem is one of the two types of transport tissue, phloem being the other. The word "xylem" is derived from classical Greek ξυλον , "wood", and indeed the best-known xylem tissue is wood, though it is found throughout the plant. Its basic function is to transport water but it also transports some, the water conducting tissue of plants. Vessel elements are typically found in the angiosperms The flowering plants , also known as Angiospermae or Magnoliophyta, are the most diverse group of land plants. Together with gymnosperms, they are the only extant groups of seed-producing plants, but they can be distinguished from the gymnosperms by a series of synapomorphies (derived characteristics). These characteristics include flowers, but absent from most gymnosperms Once an authoritative and major classification level in the plant kingdom, the gymnosperms form today a rather heterogeneous group of seed-bearing plants that includes conifers, cycads, Ginkgo and Gnetales. The term "gymnosperm" comes from the Greek word gymnospermos , meaning "naked seeds", after the unenclosed condition of such as the conifers The conifers, division Pinophyta, also known as division Coniferophyta or Coniferae, are one of 13 or 14 division level taxa within the Kingdom Plantae. Pinophytes are gymnosperms. They are cone-bearing seed plants with vascular tissue; all extant conifers are woody plants, the great majority being trees with just a few being shrubs. Typical.

Vessel elements are the building blocks of vessels, which constitute the major part of the water transporting system in the plants where they occur. Vessels form an efficient system for transporting water (including necessary minerals) from the root to the leaves and other parts of the plant.

In secondary xylem, a vessel element originates from a fusiform initial in the cambium In botany this is a layer or layers of tissue, also known as lateral meristems, that are the source of cells for secondary growth. There are two types of cambium, at maturity the protoplast dies and disappears, but the lignified cell walls persist. It may be seen as a dead cell, which still has a function, and is still being protected by surrounding living cells.

The cell wall is strongly lignified. At both ends there are openings that connect the individual vessel elements. These are called perforations or perforation plates. These perforations may have a variety of shapes: the most common are the simple perforation (a simple opening) and the scalariform perforation (several elongated openings on top of each other in a ladder-like design). Other types include the foraminate perforation plate (several round openings) and reticulate perforation plate (net-like pattern, with many openings). The side walls will have pits, and may have spiral thickenings.

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 The flowering plants , also known as Angiospermae or Magnoliophyta, are the most diverse group of land plants. Together with gymnosperms, they are the only extant groups of seed-producing plants, but they can be distinguished from the gymnosperms by a series of synapomorphies (derived characteristics). These characteristics include flowers, and presence in some members of the Gnetales Gnetum is a genus of about 30-35 species of gymnosperms, the sole genus in the family Gnetaceae and order Gnetales. They are tropical evergreen trees, shrubs and lianas. Unlike other gymnosperms they possess vessel elements in the xylem. Some species have been proposed to have been the first plants to be insect pollinated as they occur in suggest that this hypothesis must be re-examined; vessel elements in Gnetales may not be homologous with those of angiosperms, or vessel elements may have originated in a precursor to the angiosperms and were subsequently lost in some archaic or "basal" lineages (e.g., Amborellaceae Amborellaceae is a family of flowering plants endemic to New Caledonia. The family consists of only a single species, Amborella trichopoda. It is currently accepted by plant systematists as the most basal lineage in the angiosperms clade, Tetracentraceae Trochodendraceae is a family of flowering plants with two living genera found in southeast Asia. The two living species share the feature of secondary xylem without vessels, which is quite rare in angiosperms. As the vessel-free wood suggested primitiveness, these two species have attracted much taxonomic attention, Trochodendraceae, and Winteraceae), described by Arthur Cronquist as "primitively vesselless". Cronquist considered the vessels of Gnetum Gnetum is a genus of about 30-35 species of gymnosperms, the sole genus in the family Gnetaceae and order Gnetales. They are tropical evergreen trees, shrubs and lianas. Unlike other gymnosperms they possess vessel elements in the xylem. Some species have been proposed to have been the first plants to be insect pollinated as they occur in to be convergent with those of angiosperms.

Vessel-like cells have also been found in the xylem of Equisetum Equisetum is the only living genus in the Equisetaceae, a family of vascular plants that reproduce by spores rather than seeds. They are commonly known as horsetails (horsetails), Selaginella Selaginella is a genus of plants in the family Selaginellaceae, the spikemosses. Many workers still place the Selaginellales in the class Lycopodiopsida . This group of plants has for years been included in what, for convenience, was called "fern allies". Some workers have used the class Isoetopsida for both the spikemosses and the (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 therefore not a stretch to believe that vessels may have appeared more than once among the angiosperms as well.

See also

References

Categories: Plant anatomy Plant anatomy is that field in botany that needs to cut into plants to be able to study its subject, as opposed to "plant morphology" that can study its subject without resorting to a knife | Wood Wood is a material found as the primary content of the stems of woody plants, especially trees, but also shrubs. This category contains wood related articles including notable trees used for supplying wood

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