First Report of Palynological Study and Taxonomic Significance of Boraginaceae Using Scanning Electron Microscopy

The palynological characteristics of 24 plant species of Boraginaceae were studied in the present work. Using scanning electron microscopy, 24 taxa from 11 different genera were collected, identified, analyzed, and studied for their morphological and phylogenetic features. Pollen size varies from very small to medium, showing both types of polarity, and pollen types were heterogeneous, ranging from tricolporate to octacolporate. Exine ornamentations varied among the reported species, i.e., psilate, reticulate, psilate-reticulate, granulate, perforate, and psilate-perforate. Different quantitative and qualitative features of the pollen grains were noted, including polar diameter, equatorial diameter, P/E ratio, exine thickness, mesocolpium, colpi length, and colpi width, which were measured using microscopic techniques. The pollen morphologies of the species vary, and the data were analyzed using the software IBM SPSS Statistics 20. The highest exine thickness was noted in Arnebia speciosa (3.12±0.3μm), whereas the lowest value (0.95±0.1μm) was observed in two species, including Buglossoides arvensis and Onosma hispida. The maximum P/E ratio was recorded in Arnebia hispidissima 1.4. The study revealed the pollen morphology of Boraginaceae taxa, which plays a major role in the identification and phylogeny of the species and their association with systematic studies.