The angiosperm pollen wall

The ektexine consists in general of tectum, infratectum and foot layer. The outer layer, the more-or-less continuous tectum, can be covered by supratectal elements. The infratectum beneath is columellate or granular (a second layer of columellae may form an internal tectum). The foot layer may be either continuous, discontinuous or absent. The endexine may be characterized as continuous or discontinuous, spongy or compact, is present overall, only in apertures, or even completely absent. Some typical deviations of the wall thickness are named with special terms: arcus, annulus,

Costa

Nyssa sp. Nyssaceae, fossil equatorial view

Austrobuxus nitidus Picrodendraceae, fossil broken grain, thickening around the endoaperture

Costa

Nyssa sp. Nyssaceae, fossil equatorial view

Austrobuxus nitidus Picrodendraceae, fossil broken grain, thickening around the endoaperture tenuitas (see "Illustrated Glossary") and costa (a thickening of the nexine/endexine bordering an endoaperture).

Pollen terminology in saccate gymnosperm pollen

Abies sp. Pinaceae, fossil equatorial view left: corpus right: sacci left: cappa right: leptoma

Pollen types in saccate Pinus pollen

Pinus sp. Pinaceae, fossil left: polar view right: equatorial view

Haploxylon-pollen-type

Diploxylon-pollen-type left: corpus right: sacci

Haploxylon-pollen-type

Diploxylon-pollen-type

Extreme examples of variable ektexine design include massive forms lacking almost any subdivision or stratification, extremely reduced forms, or even their complete absence.

The typical angiosperm aperture shows a thick, bilayered intine.

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