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.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

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.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
The small choroidal vessels (mainly capillaries) that perforate the tapetum en route for the choriocapillaris can be viewed ophthalmoscopically as distinct dark dots the stars of Winslow.
Morphological aspect of tapetum lucidum at some domestic animals.
Moreover, it is reported that abnormal vacuolization of the tapetum during the tetrad stage was possible reason causing recessive GMS (Wan et al., 2010).
2, 3(I-II), the microsporangium wall of sterile anthers consisted of epidermis, endothecium, middle layer, and tapetum. It is shown that tapetal cells were large with condensed cytoplasm, several organelles, normal single nucleus and double nuclei, as well as large nucleus and conspicuous nucleolus (Fig.
The single cell layer of tapetum surrounding the anther loculus is first recognizable at the early Microsporocyte stage .
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., 1998).
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.
Areas of pigmentation of retinal pigment epithelium overlying tapetum were noticed in all seven pugs dogs especially near the tapetal- non tapetal junction.
When ascertaining tapetum type, it is often necessary to examine several developmental stages of the anthers to avoid confusion.
There are two major types of tapetum, the more primitive secretory type, considered to be the prevalent type in the majority of plants, and amoeboid type that extends to microspores in the anther locule [9].
In a recent overview Pacini and Franchi (1993) listed 33 species from 22 angiosperm families with secretory tapetum and orbicules (references from 1971 to 1993).