Platyopuntia


O. engelmannii © E.Arnold


UofAz
O. engelmannii UofAz 10876


UofAz
O. engelmannii UofAz

Platyopuntia:
Platyopuntia (prickly pear) pollen is large (up to 100 µm), fenestrate and reticulate. In general, the grains and fenestrae tend to be polygonal in outline.

Plants:
Classically, the Platyopuntia (prickly pears) include the flat-stemmed members of the the genus Opuntia (Cactaceae). The members of this subgenus (which freely hybridize) are widespread throughout arid regions of the New World. Currently, the genus Opuntia is divided into the Cylindropuntia (chollas), Opuntia (now the prickly pears), Grusonia (club chollas), and Nopalea and Consolea - rare taxa found only in Florida. "Platyopuntia" is used here, due to the current widespread usage of "Opuntia" to refer also to the chollas, whose pollen is distinct from that of the prickly pears. The term should be abandoned when (if?) the new systematics achieves general acceptance.

Pollen light micrograph:
Generally large, 30 - 100 µm, fenestrate, reticulate pollen grains, generlly with polygonal outlines. Sculpturing elements are apparent in the lumina, and on the floors of the fenestrae. The pollen of the various species (if taxonomists can agree that they exist) probably can be determined by size, with larger grains showing a square or hexagonal pattern of fenestrae, and smaller grains with a triangular pattern (see. Opuntia chlorotica [silver dollar cactus] below). Opuntia engelmannii pollen is dimorphic, with about 1 % of the grains being small (¼ normal size) and inaperturate (shown at right).


Opuntia basilaris UofAz 1788

Opuntia chloritica UofAz 1967

Opuntia echios UofAz 1224

Opuntia erinacea UofAz 1520

Opuntia phaeacantha UofAz 1222

Opuntia santarita UofAz 950

Pollen scanning electron micrograph (SEM)
Note the then membranes on the floors of the fenestrae, which may serve as egress for the pollen tube.

Production and Dispersal:
Low production and poor dispersal for these insect-pollinated species. The flowers are visited by a host of beetles and solitary bees.

Preservation:
The thick wall is resistant to deterioration, but the large grains often break apart.

Fossil Occurrence:
Late Quaternary.

References:

Links
Owen Davis 12/01