Vascular cambium

The vascular cambium (also called main cambium, wood cambium, bifacial cambium; plural cambia) is a plant tissue located between the xylem and the phloem in the stem of a vascular plant. It is a cylinder of unspecialized meristem cells that divide to form secondary vascular tissues. Namely, it is the source of both secondary xylem growth inwards towards the pith,[1] and secondary phloem growth outwards to the bark. Vascular cambium does not occur in the root. Unlike the xylem and phloem, it does not transport water, minerals or food through the plant.[2]

Vascular cambia are found in dicots and gymnosperms but not monocots, which usually lack secondary growth. A few leaf types also have a vascular cambium.[3] In wood, the vascular cambium is the obvious line separating the bark and wood.[4] For successful grafting, the vascular cambia of the rootstock and scion must be aligned so they can grow together.

Structure and function

The cambium present between primary xylem and primary phloem is called intrafasicular cambium. During secondary growth, cells of meduallary rays, in a line with intrafasicular cambium, become meristematic and form interfascicular cambium. Therefore, the intrafascicular and interfascicular cambia form a ring which separates the primary xylem and primary phloem, and is known as cambium ring. The vascular cambium produces secondary xylem on the inside of the ring, and secondary phloem on the outside, pushing the primary xylem and phloem apart.

The vascular cambium usually consists of two types of cells:

Maintenance of cambial meristem

The vascular cambium is maintained by a network of interacting signal feedback loops. Currently, both hormones and short peptides have been identified as information carriers in these systems. While similar regulation occurs in other meristems of plants, the cambial meristem receives signals from both the xylem and phloem sides for the meristem. Signals received from outside the meristem act to down regulate internal factors, which promotes cell proliferation, and promotes differentiation.[5]

See also

References

  1. ↑ Introductory Plant Biology-edition seven-Kingsley R. Stern
  2. ↑ Introductory Plant Biology-edition seven-Kingsley R. Stern
  3. ↑ Ewers, F.W. 1982. Secondary growth in needle leaves of Pinus longaeva (bristlecone pine) and other conifers: Quantitative data. American Journal of Botany 69: 1552-1559.
  4. ↑ Capon, Brian (2005). Botany for Gardeners (2nd ed.). Portland, OR: Timber Publishing. p. 64. ISBN 0-88192-655-8.
  5. ↑ Etchells, J. Peter; Mishra, Laxmi S.; Kumar, Manoj; Campbell, Liam; Turner, Simon R. (April 2015). "Wood Formation in Trees Is Increased by Manipulating PXY-Regulated Cell Division". Current Biology. 25 (8): 1050–1055. doi:10.1016/j.cub.2015.02.023.

External links

Wikisource has the text of The New Student's Reference Work article Cambium.
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