Palynomorphological diversity among the Asteraceous honeybee flora: An aid to the correct taxonomic identification using multiple microscopic techniques

This study aimed to characterize the palynological morphology of melliferous species of family Asteraceae belonged to seven tribes which were categorized into 15 genera and were studied under light and scanning electron microscopy. The pollen grains were acetolyzed, measured, and described qualitatively. Quantitative data were analyzed by descriptive and multivariate statistical analysis. The species were analyzed considering 11 quantitative pollen characteristics. The study revealed that the pollen grains are circular, triangular, angular, semi-angular, quadrangular, pentagonal and hexagonal amb, and 3-colporate or 3-colpate. The size of the pollen is variable among the species, ranged from 56.1 to 23.2 μm. Three pollen types: oblate spheroidal (eight species), prolate spheroidal (six species), and suboblate (two species) were observed. The surface pattern of the exine varies from echinoperforate, echinate, echinate microperforate, fenestrate, echinoperforate reticulate, microreticulate, echinate perforate, tectate, and scabrate. Exine thickness was calculated minimum in Cichorium intybus (2.47 μm) and maximum in Taraxacum campylodes (5.15 μm). A key to studied bee floral species, based on the morphological features of pollen grains, is also provided. The palynomorphological characters here analyzed can be potentially used to correctly identify the Asteraceous honeybee floral species most commonly plants visited by honeybees in the study area.