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 ?
Fundus photographs after 8 hours of patching revealed Mizou Nakamura phenomenon which is characterized by loss of the golden sheen and tapetal reflex after prolonged dark adaptation (fig-1) OCT (Topcon 3D OCT-1 Maestro) showed normal central foveal thickness but reduced retinal thickness in parafoveal region (fig-2).
Areas of pigmentation of retinal pigment epithelium overlying tapetum were noticed in all seven pugs dogs especially near the tapetal- non tapetal junction.
One of the few papers devoted to fossil orbicules and tapetal membranes is the ultrastructural work on fossil Pennsylvanian (Carboniferous, 286-320 mya) pollen grains of the Schopfipollenites-type (Taylor, 1976).
Keywords: Development; fundus; neonatal; non-tapetal; tapetal
Em estagios moderados, nota-se alteracao bem delimitada ou gradual entre as areas tapetal normais e degeneradas e, em particular, na periferia.
De modo que se ha introducido en espanol el termino camaras plasmodiales para designar las formaciones que Uehara & Kurita (1989) llamaron tapetal gaps por considerarselo apropiado tanto en los descriptivo como funcional, y asi evitar la traduccion literal.
This genetic disposition results mainly in mitochondrial dysfunction expressed in the tapetal cells of the anther tissues (Wise et al.
These storage products or their precursors are secreted by the tapetal "nurse" cells of the anther during pollen development (Wang et al.
Ophthalmoscopic and fundoscopic changes included hyper reflectivity and discoloration of the tapetal area, marked attenuation of retinal vessels, depigmentation in non-tapetal area and optic disc atrophy with scalloped borders.
Further cytological analyses revealed that deformed tapetal cells due to disintegration of middle layer may accelerate the process of apoptosis, leading to vacuolization.
In this stage, the tapetal cells are uninucleate and more vacuolated (Fig.
3h) indicates the occurrence of what are probably tapetal raphides, which also are known from other commelinaceous genera and several other related families (Hardy & Stevenson, 2000a, b; Hardy et al.