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 ?
And Southwell's PS8million refurbishment will be completed when Fibresand makes way for Tapeta, which is widely used in America and Australia.
Clerk of the course Fergus Cameron said last night: "It's the first time Tapeta has been in this situation so we don't know how it's going to react.
She is doing very well and should run her race provided she handles the Tapeta.
It has taken considerable time and effort to get used to working with Tapeta, as well as new working practices for race days and overall track maintenance.
Dickinson has two Tapeta tracks at his stables in Maryland and also hopes to utilise many other new technologies, including a hyperbaric chamber, an auxiliary energy system and a bio-mechanical analyser.
Tapeta is a synthetic surface consisting of sand, fiber, rubber and a unique brand of wax.
Bin Surour said: "They are nice horses who go well on the Tapeta.
In a statement, Dickinson said: "I need 100% of my time to concentrate on Tapeta Footings.
That Dickinson trains at a 200-acre Tapeta Farm near Chesapeake Bay, Md.
A successful floodlit trial evening has already taken place with horses galloping on the tapeta.
A 6lb penalty is unlikely to trouble him in what looks a weaker race but one thing that might is the Tapeta surface, which is not fully comparable with that at Lingfield, where he scored last month.
It was a similar experience when we learned that the Tapeta would be replaced by a new surface for the 2014-2015 UAE Racing Season and that the Dubai World Cup once again become a dirt race.