Significance of Petiolar Anatomy in Taxonomy of Acanthaceae

The present paper reports observations on anatomy of petioles hitherto uninvestigated 9 species belonging to 6 genera of the family Acanthaceae. The species studied are Pachystachys lutea Nees, Peristrophe montana Nees, Pseuderanthemum malabaricum (C. B. Clarke) Gamble, P.reticulatum Radlkf, Rungia parviflora (Retz.) Nees, Staurogyne zeylanica (Nees) O.Ktze, Stenosiphonium cordifolium (Vahl ) Alston, S.parviflorum T. Anders and S.russellianum Nees. The petioles are usually circular or broadly circular in outline and adaxially channeled. The degree of development of endomorphic features and their distribution, inclusive of cell inclusions, are described. The vasculature is generally resolved into a central prominent arc along with few or none vascular bundles. The anatomical patterns showed great variation in the epidermis, wings, pattern of vascular supply and sclerenchyma surrounding it, cell inclusions, etc., and should be considered systematically important characters in the future. A key helping identification of taxa investigated is provided based on these characters. Anatomical characters are constant and conservative and thus have potential to be used in plant taxonomy.