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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.
Microsporangia occur in all vascular plants that have heterosporic life cycles, such as seed plants, spike mosses and the aquatic fern genus Azolla. In gymnosperms and angiosperm anthers , the microsporangia produce microsporocytes, the microspore mother cells , which then produce four microspores through the process of meiosis .
Conifers typically bear their microsporangia on microsporophylls aggregated into papery pollen strobili, and the ovules, are located on modified stem axes forming compound ovuliferous cone scales. Flowering plants contain microsporangia in the anthers of stamens (typically four microsporangia per anther) and megasporangia inside ovules inside ...
The microsporangia of gymnosperms develop in pairs toward the bases of the scales, which are therefore called microsporophylls. Each of the microsporocytes in the microsporangia undergoes meiosis, producing four haploid microspores. These develop into pollen grains, each consisting of four cells and, in conifers, a pair of external air sacs.
In heterosporous plants, sporophylls (whether they are microphylls or megaphylls) bear either megasporangia and thus are called megasporophylls, or microsporangia and are called microsporophylls. The overlap of the prefixes and roots makes these terms a particularly confusing subset of botanical nomenclature.
During megasporogenesis, a diploid precursor cell, the megasporocyte or megaspore mother cell, undergoes meiosis to produce initially four haploid cells (the megaspores). [1] Angiosperms exhibit three patterns of megasporogenesis: monosporic, bisporic, and tetrasporic , also known as the Polygonum type, the Alisma type, and the Drusa type ...
As the diatom divides, each daughter retains one theca of the original frustule and produces one new theca. This means that one daughter cell is the same size as the parent (epitheca and new hypotheca) while in the other daughter the old hypotheca becomes the epitheca which together with a new and slightly smaller hypotheca comprises a smaller ...
Each type of cell behaves differently in response to FSH. Theca interna cells express receptors for luteinizing hormone . LH induces the production of androgens by the theca cells, most notably androstendione, which are aromatized by granulosa cells to produce estrogens, primarily estradiol. Consequently, estrogen levels begin to rise.