Pollen morphology of some Cucurbitaceae species in Iran

The Cucurbitaceae family is a fairly large plant family species of mainly climbing plants, mostly distributed in tropical areas, subtropical areas, and temperate regions in the northern hemisphere. The Iranian territory encompasses five genera and eight species of thus family, distributed as wild in flora of Iran. However, twelve species of this family, known as vegetables have been cultivated in different parts of Iran. In this study, pollen morphology of four species representing three genera and two varieties of the family Cucurbitaceae in Iran has been examined under light microscope. The studied taxa included Citrullus colocynthis, Citrullus lanatus, Cucumis melo and Cucurbita pepo. The target species presented pollen grains in monads, which were medium (Cucumis melo) to large (Cirtulus colocynthis and Citrulus lanatus) and very large (Cucurbira pepo) in size. Among the studied species, Cucumis melo possess the smallest pollen grains and Cucurbita pepo has the largest pollen. Two types of apertures as porate and colporate are documented for the family in this study, while three pollen types have been distinguished based on the apertures: tricolporate, triporate, and pantoporate. Tricolporate pollens were observed in Cirtulus colocynthis and Citrulus lanatus, triporate in Cucumis melo and pantaporate in Cucurbita pepo. Tricolporate pollens were observed to occur more frequently than other apertural types. Exine wall ornamentation is most often reticulate in the studies species with the exception of pollens in Cucurbita pepo, which is echinate, thus, this is a diagnostic character for this species. Our findings revealed that pollen characteristics such as aperture type and sculpturing of exine provides valuable evidences for separating of the studied species of Cucurbitaceae.