Polleniferous materials of four Onobrychis species were used in this study. Two different microscopes and one-way ANOVA analysis were applied. The pollen grains were tricolpate, isopolar, and consistently radially symmetrical. The value of the polar axis/equatorial diameter ranged from prolate to perprolate, which were categorized as tiny or medium in size. Exine sculpture patterns varied significantly when scanning electron microscopy was used: Onobrychis megataphora, O. crista-galli, and O. caput-galli have reticulate patterns; O. galegifolia has micro-reticulate perforates. The pollen morphology of O. caput-galli was noticeably perprolate due to its maximum polar axis/equatorial diameter value (2.02 µm). The O. crista-galli had the lowest polar axis/equatorial diameter value (1.37 µm), showing its prolate pollen morphology. A one-way ANOVA analysis revealed significant differences (P < 0.05) in the morphological features of polar length and equatorial diameter. The O. megataphros was primarily circular to ovoid-triangular in form, and O. caput-galli had a triangular outline. The two remaining species had circular shapes in polar view. In equatorial view, two species had elliptic-elongated shapes, while others had rectangular-obtuse outlines. Thus, these micromorphological dissimilarities indicate variations among taxa, and they can be used as taxonomic characters to identify and delimit Onobrychis species
Darweesh et al. (Tue,) studied this question.