Apertures as Pitfalls

Sometimes the apertures are inconspicuous and not discernible at first sight. In Pachira aquatica (Bombacaceae) pollen three large, more-or-less hemispherical areas are seen equatorially, which may at first sight be interpreted as three pores. However, a detailed observation reveals planaperturate pollen grains with three short colpi.

Apertures as pitfalls

Pachira aquatica Bombacaceae polar view equatorial view oblique equatorial view (SEM)

Apertures as pitfalls

Pachira aquatica Bombacaceae polar view equatorial view oblique equatorial view (SEM)

The monads of the Calliandra emar-ginata (Mimosaceae) polyad are separated by narrow groove-like depressions. At low magnification the presence and localization of the apertures remain indistinct; high SEM magnification reveals that the apertures are very inconspicuous pores, situated equatorially, usually at the conjunction of three or four monads.

Apertures as pitfalls

Calliandra emarginata

Mimosaceae massula dry state apertures (pores) at the junction of four monads

Apertures as pitfalls

Calliandra emarginata

Mimosaceae massula dry state apertures (pores) at the junction of four monads

The apertural condition may be hidden by prominent features. The clypeate pollen of Phyllanthus * elongatus (Euphorbiaceae) seems to be inaperturate. Only close-ups reveal the inconspicuous pores between the exine shields.

The disk-like pollen of Oryctanthus sp. (Loranthaceae) shows at both poles conspicuous circular depressions that are not apertures (FEUER and KUIJT 1985). The pollen is tricolpate with inconspicuous short slit-like colpi between the polar depressions on

Apertures as pitfalls

Phyllanthus x elongatus Euphorbiaceae left:

clypeate pollen seemingly inaperturate right:

inconspicuous pores between the exine shields

Apertures as pitfalls

Oryctanthus alveolatus

Loranthaceae acetolyzed left:

tricolpate (short colpi on both sides, with bridge), pollen grains in polar view right: colpus

Apertures as pitfalls

Phyllanthus x elongatus Euphorbiaceae left:

clypeate pollen seemingly inaperturate right:

inconspicuous pores between the exine shields

Apertures as pitfalls

Oryctanthus alveolatus

Loranthaceae acetolyzed left:

tricolpate (short colpi on both sides, with bridge), pollen grains in polar view right: colpus both sides. The colpi are interrupted by a broad exine bridge at the equator plane; thus calling the aperture condition "hexa-colpate" would be a possible interpretation.

Trapa (Trapaceae) pollen is triaperturate (colpate or porate). Recent and fossil pollen grains are distinguished by unique meridional exine features (crests); these cover the apertures so that only after removal of the crest the aperture is visible.

Apertures as pitfalls

Trapa sp. Trapaceae, fossil equatorial view crest broken

Apertures as pitfalls

Trapa sp. Trapaceae, fossil equatorial view crest broken

Apertures as pitfalls

Trapa sp. Trapaceae, fossil equatorial view crest in part broken colpus visible

Trapa sp. Trapaceae, fossil equatorial view

Apertures as pitfalls

Trapa sp. Trapaceae, fossil equatorial view crest in part broken colpus visible

Trapa sp. Trapaceae, fossil equatorial view

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