Taxonomic Significance of Pollen Morphological Characters in Some Taxa of Family Acanthaceae Juss

Abstract

Acanthaceae is characterized by its diverse and complex pollen types. It is a difficult group to classify. No comprehensive global study of this family has been undertaken. For this purpose, a wild Blepharis edulis was collected from its natural habitat and 24 ornamental taxa from different botanical gardens in Egypt. The present work aims to study several pollen morphological characters as a tool to understand the relationships between the studied taxa using SEM. The results indicate various variations in pollen characteristics, viz., shape of apertures, pseudocolpi, pollen class, pollen shapes, and pollen surface sculpture. Based on these pollen characters, the studied taxa were categorized under four major groups, viz., I, II, III, and IV (syncolpate, colpate, colporate, and porate pollen, respectively) and 10 types. Group I distinguished the studied taxa of subfamily Thunbergoideae (Thunbergia type). Groups II, III, and IV gathered all the studied taxa of subfamily Acanthoideae. Group II (Blepharis type). Group III (Anisacanthus, Odontonema, Hypoestes, Barleria, Dyschoriste, and Eranthemum types). Group IV (Justicia and Ruellia types). The interpretation and discussion were refined to highlight the relationships among the species, which were established on the basis of their pollen traits. An artificial key was constructed based on the pollen grain characters to assist in distinguishing the studied taxa.