Résumé
Objective To observe the histological structure of plant roots of Dendrobium Sw. for assisting identification of crude drug Herba Dendrobii. Methods Morphological and histological studies were carried out on 11 medicinal plant roots in Dendrobium Sw. by microstructural observation. The 11 species were divided into three groups according to their stem morphology: a) pair fleshy-stem group, including D. chrysanthum, D. crepidatum, D. primulinum, D. hercoglossum, and D. crystallium; b) thick-and rigid-stem group, including D. fimbriatum and D. aurantiacum var. denneanum; c) node-or inter- node- bulgy-stem group, including D. findlayanum, D. gratiosissimum, D. pendulum, and D. wardianum. The surface descriptions of velamen were conducted for D. fimbriatum and D. aurantiacum var. denneanum which are similar in characters of cross section. Results There were differences in shape and layers of velamen cell, number of xylem bundles, maximum diameter of vessels, organization of pith, as well as the types, quantity, and size of crystals. D. fimbriatum could be distingushed from its adulterant species D. aurantiacum var. denneanum by the different surface structure of velamen cells. Conclusion The histological characters of the roots can be used for assisting identification of Herba Dendrobii.