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Level 15

Ultrastructure. Tectum, Infratectum and tectal ele


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Tectum
The layer of sexine, which forms a roof over the columellae, granules or other infratectalelements.
Intectate
Describing pollen grains without a tectum, but with sculpturing. Examples: Viscum(Loranthaceae), Ilex (Araliaceae).
Semitectum
A partially discontinuous tectum in which the tectal perforations are equal to or wider than the muri and usually larger than 1μm in diameter.
Tegillum
Synonym of tectum.
Tectum solidum
Synonym of eutectum.
Pertectate
Synonym of eutectate.
Supratectal
Indicating the position of features, such as spines, on the top of the tectum.
Etectate
Describing pollen grains interpreted as having lost their tectum during evolutionary development.
Eutectum
Describing a pollen grain with a continuous tectum.
Infratectum
A general term for the layer beneath the tectum, which may be alveolar, granular,columellar, or structureless.
Columellae layer
Synonym of infratectum.
Interstitium
The layer of the exine situated between the nexine and the tectum.
Internal tectum
A more or less continuous layer within the outer sexineectexine composed of laterally connected parts of columellae. Example: Nigella damascena (Ranunculaceae).
Tectum perforatum
A tectum with perforations smaller than 1μm in diameter.
Tectum imperforatum
With a continuous tectum, without perforations.
Striae
Grooves between elongated sculpturing elements.
Punctum
A rounded or elongate tectal perforation, less than 1μm in length or diameter.
Scrobiculus
Synonym of punctum.
Gemma
A sexine element which is constricted at its base, higher than 1μm, and that has approximately the same width as its height.
Discordant pattern
A pattern in a tectate pollen grain in which the arrangement of the columellae is different from that of the elements on the tectum. Example: Geranium (Geraniaceae).
Concordant pattern
A pattern in a tectate pollen grain in which the arrangement of the columellae is the same as that of the elements upon the tectum. Example: Lilium (Liliaceae).
Areola
A feature of ornamentation in which the sexine/ectexine is composed of circular or polygonal areas separated by grooves which form a negative reticulum. Examples: Apama(Aristolochiaceae), Phyllanthus spp. (Euphorbiaceae).
Alveolate
Describing a type of sexine/ectexine structure, in which the infratectal layer is characterised by partitions forming compartments of irregular size and shape. Example:Pinus (Pinaceae).