Efficient Micropropagation of Spilanthes acmella (L.) Murr.: A Threatened Medicinal Herb

The present study describes an efficient and reproducible protocol for micropropagation of S. acmella. Shoot tips taken from 3 week-old aseptic seedlings were cultured on Murashige and Skoog (MS) semi-solid medium supplemented with different concentrations of TDZ. Among various concentrations, 0.25 µM TDZ was found to be optimum for shoot regeneration as it induced a maximum of 30.0 shoots per explant however with retarded growth (1.0 cm). Among different volumes of culture media, 15 ml liquid culture medium favored best response wherein a maximum of 80.2 shoots per explant with an average shoot length of 7.0 cm were induced after 6 week of subculturing. Successful in vitro rooting was induced on 2.5 µM NAA containing half-strength MS medium. Almost 96% rooted plants successfully transferred and acclimatized ex vitro under green house conditions. Morphological and physiological parameters compared with the in vivo-grown seedlings of the same age appeared to be ‘normal’ in respect to the fundamental characteristics examined.