In botany, the theca is related to plant's flower anatomy. The theca of an angiosperm consists of a pair of microsporangia that are adjacent to each other and share a common area of dehiscence called the stomium.[1] Any part of a microsporophyll that bears microsporangia is called an anther. Most anthers are formed on the apex of a filament. An anther and its filament together form a typical (or filantherous) stamen, part of the male floral organ.
The typical anther is bilocular, i.e. it consists of two thecae. Each theca contains two microsporangia, also known as pollen sacs. The microsporangia produce the microspores, which for seed plants are known as pollen grains.
If the pollen sacs are not adjacent, or if they open separately, then no thecae are formed. In Lauraceae, for example, the pollen sacs are spaced apart and open independently.
The tissue between the locules and the cells is called the connective and the parenchyma. Both pollen sacs are separated by the stomium. When the anther is dehiscing, it opens at the stomium.
The outer cells of the theca form the epidermis. Below the epidermis, the somatic cells form the tapetum. These support the development of microspores into mature pollen grains. However, little is known about the underlying genetic mechanisms, which play a role in male sporo- and gametogenesis.
The thecal arrangement of a typical stamen can be as follows:
Divergent: both thecae in line, and forming an acute angle with the filament
Transverse (or explanate): both thecae exactly in line, at right angles with the filament
Oblique: the thecae fixed to each other in an oblique way
Parallel: the thecae fixed to each other in a parallel way
Zoologyedit
In biology, the theca of follicle can also refer to the site of androgen production in females. The theca of the spinal cord is called the thecal sac, and intrathecal injections are made there or in the subarachnoid space of the skull.
^Larry Hufford, "The origin and early evolution of angiosperm stamens" in The Anther: form, function, and phylogeny, William G. D'Arcy and Richard C. Keating (editors), Cambridge University Press, 1996, 351pp, p.60, ISBN978-0-521-48063-5 (from Google Books)
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theca, this, article, needs, additional, citations, verification, please, help, improve, this, article, adding, citations, reliable, sources, unsourced, material, challenged, removed, find, sources, news, newspapers, books, scholar, jstor, april, 2009, learn, . This article needs additional citations for verification Please help improve this article by adding citations to reliable sources Unsourced material may be challenged and removed Find sources Theca news newspapers books scholar JSTOR April 2009 Learn how and when to remove this template message In biology a theca plural thecae is a sheath or a covering Strawberry anther with parallel thecae Contents 1 Botany 2 Zoology 3 In other taxonomic groups 4 See also 5 ReferencesBotany editIn botany the theca is related to plant s flower anatomy The theca of an angiosperm consists of a pair of microsporangia that are adjacent to each other and share a common area of dehiscence called the stomium 1 Any part of a microsporophyll that bears microsporangia is called an anther Most anthers are formed on the apex of a filament An anther and its filament together form a typical or filantherous stamen part of the male floral organ The typical anther is bilocular i e it consists of two thecae Each theca contains two microsporangia also known as pollen sacs The microsporangia produce the microspores which for seed plants are known as pollen grains If the pollen sacs are not adjacent or if they open separately then no thecae are formed In Lauraceae for example the pollen sacs are spaced apart and open independently The tissue between the locules and the cells is called the connective and the parenchyma Both pollen sacs are separated by the stomium When the anther is dehiscing it opens at the stomium The outer cells of the theca form the epidermis Below the epidermis the somatic cells form the tapetum These support the development of microspores into mature pollen grains However little is known about the underlying genetic mechanisms which play a role in male sporo and gametogenesis nbsp Divergent thecae in GraderiaThe thecal arrangement of a typical stamen can be as follows Divergent both thecae in line and forming an acute angle with the filament Transverse or explanate both thecae exactly in line at right angles with the filament Oblique the thecae fixed to each other in an oblique way Parallel the thecae fixed to each other in a parallel wayZoology editIn biology the theca of follicle can also refer to the site of androgen production in females The theca of the spinal cord is called the thecal sac and intrathecal injections are made there or in the subarachnoid space of the skull In human embryogenesis the theca cells form a corpus luteum after a Graafian follicle has expelled its secondary oocyte arrested in second meiosis Thecal shape is also important in graptolite and pterobranch taxonomy In dinoflagellates that are armoured their covering is made up of thecal plates In other taxonomic groups editIn microbiology and planktology a theca is a subcellular structural component out of which the frustules of diatoms and dinoflagellates are constructed See also editIntrathecal Thecal sacReferences edit Larry Hufford The origin and early evolution of angiosperm stamens in The Anther form function and phylogeny William G D Arcy and Richard C Keating editors Cambridge University Press 1996 351pp p 60 ISBN 978 0 521 48063 5 from Google Books nbsp This plant physiology article is a stub You can help Wikipedia by expanding it vte Retrieved from https en wikipedia org w index php title Theca amp oldid 1171368661, wikipedia, wiki, book, books, library,
