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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.
Encephalartos villosus microsporophylls with microsporangia. A microsporangium (pl. microsporangia) is a sporangium that produces microspores that give rise to male gametophytes when they germinate. Microsporangia occur in all vascular plants that have heterosporic life cycles, such as seed plants, spike mosses and the aquatic fern genus Azolla.
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 thecal sac or dural sac is the membranous sheath (theca) or tube of dura mater that surrounds the spinal cord and the cauda equina.The thecal sac contains the cerebrospinal fluid which provides nutrients and buoyancy to the spinal cord. [1]
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.
A theca is two microspoorangia. The gynoecium (women's house) is the collective term for the female organs (carpels). A carpel is a modified megasporophyll consisting of two or more ovules, which develop conduplicatively (folded along the line). The carpels may be single, or collected together, to form an ovary, and contain the ovules.
Species with a theca are divided into four orders, based on the arrangement of the armor plates: Dinophysiales - e.g. Dinophysis; Gonyaulacales - e.g. Ceratium, Gonyaulax; Peridiniales - e.g. Peridinium; Prorocentrales - e.g. Prorocentrum; The Peridiniales are probably paraphyletic to the others, and on rRNA trees they are mixed with the ...
The organism has thick wall (theca) with internal septations that form the small wedge-shaped endospores, which are arranged radially and moulded (morula-like form). [1] Reproduction is asexual by release of the spores from the sporangia, which can occur every 5–6 hours in ideal conditions.