Tapetum


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tapetum

[tə′pēd·əm]
(botany)
A layer of nutritive cells surrounding the spore mother cells in the sporangium in higher plants; it is broken down to provide nourishment for developing spores.
(neuroscience)
A reflecting layer in the choroid coat behind the neural retina, chiefly in the eyes of nocturnal mammals.
A tract of nerve fibers forming part of the roof of each lateral ventricle in the vertebrate brain.

Tapetum

 

a layer (occasionally several layers) of cells in the sporangia of the majority of higher plants; it is rich in nutrients and physiologically active substances. The tapetum may originate from the archespore, as in leptosporangiate ferns and selaginellas. It may be the inner layer of the sporangium wall, as in eusporangiate ferns, plants of the order Lycopodiales, and plants of the genus Equisetum, or the inner layer of a microsporangium, as in seed plants.

The substances in tapetum cells are used by the developing sporocytes and spores; in seed plants they are used by the pollen grains as well. The tapetum cells either form a periplasmodium, or amoeboid tapetum, or they maintain their position, forming a secretory tapetum. There is no tapetum in the sporangia of Psilotophyta or Isoëtales.

References in periodicals archive ?
Areas of pigmentation of retinal pigment epithelium overlying tapetum were noticed in all seven pugs dogs especially near the tapetal- non tapetal junction.
In dogs with absence of tapetum, position of OD could not be differentiated.
Moreover, it is reported that abnormal vacuolization of the tapetum during the tetrad stage was possible reason causing recessive GMS (Wan et al.
2, 3(I-II), the microsporangium wall of sterile anthers consisted of epidermis, endothecium, middle layer, and tapetum.
The single cell layer of tapetum surrounding the anther loculus is first recognizable at the early Microsporocyte stage .
anther wall followed the dicotyledonous type, which was composed of an epidermal layer, an endothelial layer, one middle layer and tapetum which is consistent with Davis 1966 and bagheri 2014.
Since the early days of orbicule-research, a positive correlation was hypothesised between the presence of orbicules and a parietal tapetum type (von Ubisch, 1927; von Kosmath, 1927), although several species were identified with parietal tapetal cells but lacking orbicules (Huysmans et al.
The relatively large size of her eyes, the dense population of rods in her retina, and the tapetum lucidum layer behind the retina are all adaptations aimed at maximizing night vision.
By the late sporogenous mass stage, when callose first appeared around the sporogenous cells, the tapetum and parietal layer cells from male-sterile plants showed vacuoles (Fig.
When ascertaining tapetum type, it is often necessary to examine several developmental stages of the anthers to avoid confusion.
On maturation of the anther, the sporangial wall consists of the epidermis and the endothecium, whereas the middle layers and tapetum disintegrate.
The aim of the present paper is threefold: (1) to give a concise state of knowledge about tapetum and orbicules, (2) to enumerate the taxa where orbicules were reported to be present or certified absent, and (3) to visualize the systematic distribution of orbicules throughout the angiosperms by plotting the information on a dahlgrenogram.