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 ?
When pollen grains become mature, the tapetal cells were degenerated, In meiotic division, the middle layers cells start a degeneration process.
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.
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).
The visual cells in these eyes bend around the tapetum, exiting through the opening between the adjacent tapetal plates.
Some tapetal derives are left between the collumella (Fig.
The uninucleate tapetal cells were commonly observed.
Systematic significance of cell inclusions in Haemodoraceae and allied families: silica bodies and tapetal raphides.
diameter and are not embedded in tapetal membrane (although exceptional
micro]m in diameter and are embedded in the tapetal membrane.
This was observed in several species and in different cell types; for example, in the tapetal cells of Zea mays (Panchaksharappa & Rudramuniyappa, 1974).
In the secretory type, a layer of tapetal cells remains intact around the anther locule, whereas in the plasmodial type a multinucleate tapetal plasmodium is formed in the anther locule by degeneration of tapetal cell walls and fusion of their protoplasts.
Since Goebel (1901) two main tapetal types are recognized: the secretory (a.