Palynological study of the urban flora of Chihuahua City, Mexico

The aim of this study was to provide the first palynological study of Chihuahua City, Mexico, resulting in the development of a graphic reference document about pollen of Gymnosperms and Angiosperms in this zone. Samples of both ornamental and wild plants were included, which were collected on sidewalks, parks, public areas, and suburbs of the studied area. The study included 91 taxa: 15 trees, 10 shrubs and 66 herbs from 37 families and 86 genera. Pollen grains were directly obtained from the stamens and observed with scanning electronic microscope without acetolizing, hydrating or dehydrating. Most of the studied pollen grains had a medium size (60%). The most common ornamentation patterns were echinate (23%) and reticulate (22%). A large percentage of the pollen grains showed elongated apertures: tricolporate (41%) and tricolpate (13%), which coincides with the folding pattern of sunken apertures. Pollen grains of most of the studied species show spheroidal shape in hydrated state (83%), while the most common shape among dehydrated grains is prolate (51%). Three main pollen types were observed; the first type corresponds to the family Asteraceae and the second one to Poaceae. The third type included 10 families and 15 species whose pollen grains have reticulated ornamentation, elongated apertures, prolate shape in its dry state and sunken apertures. It is recognized that the inclusion of more species present in the area is needed.