Micromorphology and histochemistry of the secretory apparatus of Plumbago auriculata Lam.

Abstract

This study interprets the structure and provides insights on the phyto-compounds of the leaves and calyces of Plumbago auriculata and evaluates its potential as a medicinal plant based on the presence of these compounds. Structure and possession of phyto-compounds were determined using light and electron microscopy and various histochemical tests. Glandular capitate and non-glandular uniserate trichomes were present on the surface of the calyx. Glandular trichomes bear a close resemblance to the digestive glands of the genus Drosera. Salt glands present on the leaf surface were abundant on the abaxial surface and revealed the presence of “transfer cells” reported for the first time in the genus. Abundant mitochondria, mini vacuoles, ribosomes, dictyosomes and rough endoplasmic reticulum cisternae were actively involved in the secretory process. Histochemical staining also revealed the presence of alkaloids and phenolic compounds that are of medicinal importance used to treat multiple ailments and also function as chemical deterrents in plants. Overall, this study contributes to the existing body of knowledge on the secretory structures of P. auriculata and provides new insights on the ultrastructural and histochemical aspects of the species.