In vitro mass multiplication and production of roots in Plumbago rosea.

Mass multiplication of Plumbago rosea was achieved by indirect organogenesis in young stem, leaf and root explant cultures of 6-9-month-old plants. All the explants responded similarly in a hormonal regime of 2.5 mg/L BA and 1.5 mg/L NAA with the formation of nodular callus in 4 weeks; the callus was divided and subcultured at 4-week intervals in the presence of 3.0 mg/L BA to produce up to 23.5 +/- 1.6 shoots in 18 weeks and then at 2.0 mg/L BA to produce up to 79.6 +/- 1.5 shoots in 23 weeks. The shoots of 2.0-3.5 cm length were rooted easily in half-strength MS agar medium supplemented with 0.1 mg/L IBA and rooted plants established within 4 weeks at a 95-98 % rate without hardening. Eight weeks after establishment, the micropropagated plants were transferred to experimental plots and cultivated for 10 months to obtain a significantly higher number (18.0 +/- 0.5) of larger tuberous roots (137.4 +/- 3.4 g fw/plant) compared to conventional rooted cuttings (14.0 +/- 1.7, 47.9 +/- 1.6 g fw/plant). During this period, the concentration of the root-specific compound, plumbagin recorded per g dw (1.5 %), was higher than that of conventionally propagated plants (0.9-1.0 %). The early formation of plumbagin-rich tuberous roots holds significant potential for the commercial cultivation of the micropropagated plants.