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n. pl. ta·pe·ta (-tə)
1. Botany A nutritive tissue that surrounds certain developing spores, particularly the microspores within an anther.
2. Anatomy
a. A reflective membrane in the back of the eye of many animals that are active during low-light conditions.
b. A layer of fibers of the corpus callosum forming the roof of part of the lateral ventricle of the brain.

[Medieval Latin tapētum, coverlet, from Latin tapēte, *tapētum, from Greek tapēs, tapēt-; see tapestry.]

ta·pe′tal (-pēt′l) adj.


n, pl -ta (-tə)
1. (Botany) a layer of nutritive cells in the sporangia of ferns and anthers of flowering plants that surrounds developing spore cells
2. (Zoology)
a. a membranous reflecting layer of cells in the choroid of the eye of nocturnal vertebrates
b. a similar structure in the eyes of certain nocturnal insects
3. (Anatomy) anatomy a covering layer of cells behind the retina of the eye
[C18: from New Latin, from Medieval Latin: covering, from Latin tapēte carpet, from Greek tapēs carpet]
taˈpetal adj


(təˈpi təm)

n., pl. -ta (-tə).
1. Bot. a layer of nutritive tissue in a developing sporangium or anther that is absorbed as the spore matures.
2. Anat. any of certain membranous layers or layered coverings, as in the choroid coat in certain animals.
[1705–15; < New Latin; Medieval Latin tapētum coverlet (Latin, only pl.) < Greek tapēt-, s. of tápēs carpet]
ta•pe′tal, adj.
References in periodicals archive ?
Both von Ubisch (1927) and von Kosmath (1927) have published lists of species with and without orbicules and considered orbicules to be restricted to taxa with a 'secretory' tapetum type.
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.
To date our knowledge is insufficient to provide plausible answers to why many plants produce orbicules and why they are absent in several evolutionary successful lineages, even when they are characterized by a parietal tapetum type (e.
The current study aims at (1) providing a summary of all data available on orbicule presence/absence in the flowering plants; (2) identifying patterns in the distribution data by mapping them on a recent angiosperm classification; (3) discussing correlations with tapetum types, pollination syndromes and other traits.
Appendix S1 summarizes the orbicule data at species level with orbicule absence/ presence and, if available, the occuring tapetum type.
The majority of pteridophytes are shown to have an amoeboid tapetum (Parkinson & Pacini, 1995), however, many homosporous ferns have globular bodies in their sporangial locules that were considered to be homologous to orbicules in spermatophytes (Lugardon, 1981).
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).
The aim of the present paper is threefold: (1) to give a concise state of knowledge about tapetum and orbicules, (2) to enumerate the taxa where orbicules were reported to be present or certified absent, and (3) to visualize the systematic distribution of orbicules throughout the angiosperms by plotting the information on a dahlgrenogram.
parietal, glandular, or cellular non-syncytial) tapetum and the amoeboid (a.
The tapetum is essentially of parietal origin, irrespective of the type of anther wall formation (Davis, 1966).
References of ontogenetic studies of tapetum can be found in, e.
Both types of tapetum occur together in 12 families.