Identification of "Huoshan shihu" Fengdou: Comparative authentication of the Daodi herb Dendrobium huoshanense and its related species by macroscopic and microscopic features

"Huoshan shihu," derived from Dendrobium huoshanense, is a well-known, valuable, and rare Daodi herb. Because of its higher price and scarce resources, its related species D. officinale and D. moniliforme are usually presented as "Huoshan shihu" for sale. Fengdou, the processed form of D. huoshanense, its identification is particularly important. To effectively identify Fengdou of D. huoshanense and protect the Daodi herb, the morphological and microscopic characteristics of the stems of three Dendrobium species were examined. The results showed that macroscopic and microscopic features helpful for identification of the three species were the total lengths and internode numbers of stems, diameter and length of each internode, number of vascular bundles, and presence or absence of silica masses. The key features useful for distinguishing between D. huoshanense and its related species, and also between their Fengdou, were the stem lengths and the trends of change in diameter in different internodes. The results of the study indicated that a combination of macroscopic and microscopic identification techniques might conveniently and effectively be applied for identification of Dendrobium species. "Longtou Fengwei" is the main feature of the Daodi herb "Huoshan shihu," (D. huoshanense Fengdou) and reflects the wisdom behind the protection of Daodi herbs in ancient times.