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 ?
Tapetal development and abiotic stress: a centre of vulnerability.
Most of the genes showing anther-specific or predominant expression are related to tapetal and pollen developments (Table 2).
The optic disc was more distinct, round and more prominent (due to presence of larger amount of myelin) and located within the tapetal fundus (Fig.
Marsh, "Tapetal effect of an azalide antibiotic following oral administration in beagle dogs," Fundamental and applied toxicology: Official Journal of the Society of Toxicology, vol.
Oguchi disease is a rare autosomal recessive form of congenital stationary night-blindness that is characterized by a golden tapetal fundus reflex.
At the ocular fundus examination horizontal bands were observed in the non-tapetal fundus area, as well as, mild peri-papillary edema (Figure 1), and tapetal hyper-reflectivity zones (Figure 2) with retinal folds and active inflammation (Figure 3) and inflammatory exudates (Figure 4), which guided the diagnosis of active corio-retinitis.
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., 1998).
Structural adaptations include modifications to dioptric elements, to photoreceptor arrangement, and to presence or absence of tapetal reflectors, while physiological adaptations may be to spectral (wavelength) sensitivity, absolute irradiance sensitivity, and temporal resolution (reviewed in Land and Nilsson, 2002).
Measurements from frontal sections rather than sagittal sections were used and the tapetal periphery was taken to represent the limits of the visual cells and therefore define the width of the retina.
Male sterility was attributed to tapetal malfunction.