Foliar micromorphology, ultrastructure, and histochemical analysis of Barleria albostellata C.B. Clarke

Abstract

Barleria albostellata (Acanthaceae), is a valuable medicinal plant with a broad spectrum of antibacterial and anti-inflammatory activities. This study aimed to characterize the micromorphology, distribution, and chemical composition of the trichomes present on the leaves and stems of B. albostellata using light and electron microscopy and histochemistry. Morphological observations using stereo and scanning electron microscopy (SEM) revealed a dense indumentum bearing numerous non-glandular trichomes on the leaves and stems of B. albostellata. The histochemical and SEM analyses revealed the presence of five morphologically distinct glandular capitate trichome types, multangulate-dendritic branched (MDB) non-glandular trichomes and a glandular head attached to a branched non-glandular trichome. Transmission electron micrographs showed that numerous plastids, mitochondria, and endoplasmic reticulum cisternae were actively involved in the secretory process. The stained leaf and stem sections indicated the presence of alkaloids and phenolics as the major medicinal compounds in glandular and non-glandular trichomes. To our knowledge, this study represents the first detailed report describing the key micromorphological features of the foliar structures of B. albostellata as well as the preliminary chemical composition of the secretions produced by these structures.