Pit (botany)
Pits are relatively thinner portions of the
Pits are composed of three parts: the pit chamber, the pit aperture, and the pit membrane. The pit chamber is the hollow area where the secondary layers of the cell wall are absent. The pit aperture is the opening at either end of the pit chamber. The pit membrane is the primary cell wall and middle lamella, or the membrane between adjacent cell walls, at the middle of the pit chamber.[2]
The primary cell wall at the pit membrane may also have depressions similar to the pit depressions of the secondary layers. These depressions are primary pit-fields, or primary pits. In the primary pit, the primordial pit provides an interruption in the primary cell wall that the
Pit pairs are a characteristic feature of xylem, as sap flows through the pits of xylem cells.[4]
Types of pits
Though pits are usually simple and complementary, a few more pit variations can be formed:[5]
- Simple pits: A pit pair in which the diameter of the pit chamber and the diameter of the pit aperture are equal.
- Bordered pits: A pit pair in which the pit chamber is over-arched by the cell wall, creating a larger pit chamber and smaller pit aperture.
- Half bordered pits: A pit pair in which a bordered pit has a complementary simple pit. Such a pit pair is called half bordered pit pair.
- Blind pits: A pit pair in which a simple pit has no complementary pit.
- Compound pits: A pit pair in which one cell wall has a large pit and the adjacent cell wall has numerous small pits.
Plasmodesmata
Plasmodesmata are thin sections of the endoplasmic reticulum that traverse pits and connect adjacent cells. These sections provide an avenue of transport through the pits and facilitate communication.[6] Plasmodesmata are not restricted to pits however, as plasmodesmata often cross a cell wall of constant width and occasionally the cell wall is even wider in areas where plasmodesmata traverse it.[3]
Torus and margo
The torus and margo are characteristic features of bordered pit-pairs in
The margo is flexible and can move towards either side of the pit while under stress. This allows the thick, impermeable torus to block the pit aperture. When the torus is displaced so that it blocks the pit aperture, the pit is said to be aspirated.[7]
References
- ISBN 9780521316118.
- ISBN 9780470047378.
- ^ ISBN 0-471-24520-8.
- ISBN 9780815650300.
- ^ "Pits in Plants | EasyBiologyClass". www.easybiologyclass.com. 2016-03-12. Retrieved 2023-08-31.
- ISBN 9781139486361.
- S2CID 97730825.
Further reading
- Andreas Bresinsky, Christian Körner, Joachim W. Kadereit, Gunther Neuhaus, Uwe Sonnewald: Strasburger – Lehrbuch der Botanik. Begründet von E. Strasburger. Spektrum Akademischer Verlag, Heidelberg 2008 (36. Aufl.) ISBN 978-3-8274-1455-7
- Dietger Grosser: Die Hölzer Mitteleuropas – Ein mikrophotographischer Holzatlas, Springer Verlag, 1977. ISBN 3-540-08096-1
- Rudi Wagenführ: Holzatlas, 6. neu bearb. und erw. Aufl., ISBN 978-3-446-40649-0