Comparative vegetative anatomy of Wrightia tinctoria R.Br. and the endemic Wrightia indica Ngan (Apocynaceae Juss.) occurring in peninsular India

Abstract

• The vegetative anatomy of Wrightia tinctoria and Wrightia indica was examined. • Giant stomata were present in leaves of W. tinctoria . • Trichomes were absent in the stem of W. tinctoria but present in W. indica . • Gelatinous fibers present in roots of W. indica were absent in W. tinctoria . • Vegetative anatomy could be valuable in the pharmacognosy of the Wrightia species. Wrightia tinctoria R.Br. and the endemic Wrightia indica Ngan are important medicinal plants possessing novel therapeutic compounds. However, the anatomy of these medicinal plants is not well studied. Therefore, the present study illustrates the vegetative anatomy of the two Wrightia R.Br. species using light microscopy. The stomata in the leaves were paracytic/anomocytic type in W. tinctoria and of paracytic type in W. indica . The foliar cuticle was of varying thickness, and multicellular trichomes were distributed on the abaxial surface of W. tinctoria and both leaf surfaces of W. indica . The leaf anatomical characters like uniseriate epidermis, collenchymatous hypodermis, heterogeneous mesophyll, endarch xylem, idioblasts, starch grains, and raphides were common for both the Wrightia species. Stems of W. indica were sparingly covered by multicellular trichomes. The stems of both Wrightia species possess uniseriate epidermis, angular collenchymatous hypodermis, parenchymatous cortex, starch grains, bicollateral vascular bundles with endarch xylem, idioblasts containing calcium oxalate crystals and water-cells in the stelar region. Starch grains were abundant in the pith of W. indica . The root periderm consists of rectangular cells and the cortex was parenchymatous in both Wrightia species. Water-cells and sclereids were present in the cortex of W. tinctoria , whereas sclereids were absent in W. indica . Vascular bundles were amphicribral in both Wrightia species. Significant differences were evident in the cellular dimensions of vegetative parts of both the Wrightia species. The observations of the present study indicate that the vegetative anatomy could aid in the discrimination of these two Wrightia species.