Dysosma comprises seven species distributed from central and southern China to Taiwan. Among them, Dysosma pleiantha (Hance) Woodson (Berberidaceae), highly prized by the mountain tribes of Taiwan for its medicinal properties, is a herbaceous, rhizomatous perennial. It is an interesting species discovered by Watters in Taiwan in 1881 and described by Hance in 1883 as Podophyllum pleianthum (). It was later introduced as the synonyms P. versipelle Hance, P. onzoi Hayata, etc.. Woodson (1928) compared the floral and vegetative features of P. pleiantha and those of other species of Podophyllum in herbarium material, and indicated some features which are quite different, and suggested this herb as D. pleiantha (Hance) Woodson. This plant, distributed from Himalayan districts to Taiwan through the mountainous parts of China, was rarely cultivated in any of the European and American botanical gardens until earlier in this century. So, contrary to its related species Podophyllum peltatum L. and P. Emodi Wall., its morphological and histological studies have been rather neglected, although some descriptions were given by Kumazawa (1936), Ying (1979), and Terabayashi (1983). Studies on its heteromorphic karyotype have been documented.
Several natural chemicals have been isolated from this herb. Those present in Podophyllum species have now been chemically modified to produce the clinically useful drugs etoposide and teniposide. Etoposide is of particular value in the treatment of testicular cancer and small-cell lung cancer, and is now produced from podophyllotoxin. This upsurge in pharmacological activities and demand for large quantities of rhizomes for studies and folk medicine make this species one of the most highly priced herbs in the local herb market in Taiwan.
Natural regeneration of Dysosma is either by seed or by sprout from the rhizomes, but due to its long juvenile phase (5-7 years) and low quantity in fruit setting, poor seed variability, and slow seedling growth, propagation through seeds is not satisfactory. Propagation by rhizomes is also very slow. Thus, in vitro culture was undertaken in the attempt to develop a more rapid method for multiplication for urgent needs.
Conclusion and Prospects
Explants from young leaves, rhizome pith tissue, and immature seeds are excellent material for production of embryoids in tissue culture of D. pleiantha. We recommend their maintenance at 25 ± 1 °C in the dark on MS basal medium plus 1 mg/1 2,4-D as the best medium for establishment of callus cultures and forming embryogenic callus. Once the embryogenic calli have been isolated, embryoid proliferated optimally in MS plus 0.1-0.5 mg/1 2,4-D in the condition as for callusing. Plant regeneration occurred best in a medium based on MS or B5 plus benzyladenine 1 mg/1 and gibberellic acid 1 mg/1 for 3 to 4 weeks kept under 16/8 h light/dark regime at 27 ± 1°C.
To the present, dozens of plants have been established under glasshouse condition. The stability of the clone raised so far, with respect to the medicinally valuable components, is under assessment. If it is confirmed that embryoid-derived plants are homogeneous and genetically similar to mother plants, our protocols for micropropagation through somatic embryogenesis could replace the conventional methods for mass propagation, provided that the cost is compatible.
Selections from the book: “Medicinal and Aromatic Plants III”, 1991.