A Comparative Study of Floral and Pollen Micromorphology in Robinia pseudoacacia and Robiniae Flos (Fabaceae)

Background: Robinia pseudoacacia L. and its herbal product, Robiniae Flos, are traditionally used in Korea. However, commercially processed floral materials often exhibit similar morphological characteristics despite originating from different botanical sources. This study aimed to establish reliable authentication criteria by comparing the micromorphologies of fresh R. pseudoacacia flowers and Robiniae Flos. Methods and Results: Floral structures (petals, sepals, and pollen) were examined using stereo, light, and field-emission scanning electron microscopy. Petal epidermal features, including papillose and tabular flat cells and densely pubescent sepals, were identified. The pollen grains were monads and tricolporate with psilate–perforate ornamentation. No significant micromorphological differences were observed between the fresh and herbal samples. However, the pollen of the potentially confusable species, Styphnolobium japonicum, was significantly smaller, enabling clear discrimination between R. pseudoacacia and Robiniae Flos. Conclusions: Fresh and commercial samples of R. pseudoacacia exhibited highly similar micromorphological traits. However, pollen samples from S. japonicum were distinct, providing a basis for discrimination. These findings provide reliable micromorphological criteria for distinguishing Robiniae Flos from other herbal products of morphologically similar species.