PALYNOLOGY OF SOME SPECIES IN THE FAMILY CUCURBITACEAE FROM NIGERIA

Pollen morphology of ten (10) species representing nine (9) genera, two (2) varieties in the family Cucurbitaceae from Nigeria has been examined under light microscope. The pollen grains are largely monads. Exine wall ornamentation is most often reticulate in all the species of the family studied with the exception of pollens in Cucurbita maxima Duch. which are echinate, this is a diagnostic character for this species. Cell wall thickness is the least variable among all the characters studied. Almost all types of pollen shape classes have been observed within this family, namely spheroidal, subprolate, oblate-spheroidal, prolate-spheroidal, suboblate and prolate, with more than one shape type occurring in a species. It is worthy of note that pollen shape and aperture type can be used to delimit Lagenaria siceraria (spatulate fruit shape) from Lagenaria siceraria (oval fruit shape). However, the shapes are the same in Citrullus lanatus (black seeds water melon) and Citrullus lanatus (brown seeds water melon). Three (3) types of apertures, porate, colpate (very occasionally) and colporate are documented for the family in this study, while seven (7) pollen types have been distinguished based on the apertures: monoporate, monocolpate, bicolporate, triporate, tricolporate, tetraporate and tetracolporate. Tricolporate pollens were observed to occur more frequently than other apertural types. Pollen grains belong to the size categories Media and Magna and only very occasionally in the Minuta category. The implication of these size categories in the reproductive success of the plants in this family is highlighted.