The effect of plant growth regulators was investigated on in vitro shoot proliferation from axillary bud explants of Hypericum erectum. To determine the optimal cytokinin for proliferation of axillay buds, we carried out screening four cytokinins (BA, kinetin, 2iP, TDZ). When nodal segments were cultured on MS medium supplemented with 4.5 μM TDZ (thidiazuron), a number of shoots were induced. Our results indicated that the addition of TDZ to culture medium resulted in the induction of significantly more axillary buds than in the addition of other cytokinins. The optimal concentration of TDZ for proliferation of axillary buds was 10 μM. 92% of shoots spontaneously rooted without any plant growth regulator (PGR) and formed whole plantlets within one month. More than 95% of these regenerants survived and they did not show any detectable variation in morphology or growth characteristics compared to their donor plants.

We established a practical method for rapid and large-scale production of Valeriana fauriei var. dasycarpa Hara roots by bioreactor culture and confirmed valerenic acids and valepotriates production. We also compared valerenic acids and valepotriates production patterns according to various media conditions. Among the media tested, B5 medium gave the maximum biomass production of 101 g fresh weight, which was a 5.03-fold multiplication rate obtained 4 weeks after inoculation of 20 g of fresh weight. The best production of total valerenic acids (7.86 mg/l) and valepotriates (8.96 mg/l) was B5 medium.

An efficient plant regeneration of C. asiatica was achieved from organogenesis using petiole explants of in vitro plantlet on MS basal medium controled with different plant growth regulators (NAA,2,4-D, IAA kinetin, and BA). Best results that 50%, efficiency of regeneration per explant for regeneration were obtained with IAA 17.13 μM and BA 8.9 μM. Formation of adventitious shoots via organogenesis from the petiole explant was verified by histological sectioning of plantlets. Regenerated plants were transplanted into soil.

Centella asiatica accumulates large amounts of triterpene saponin, such as centellasaponin, asiaticoside, madecassoside. We examined the effect of two candidates, MJ (Methyl jasmonate) and TDZ (thidiazuron), on asiaticoside production and the accumulation of bAS mRNA associated with asiaticoside biosynthesis in leaves of cultured whole plants. The growth of whole plants treated with 0.1 mM MJ was found to decrease significantly, however, the growth of whole plants treated with 0.1 mM MJ plus 0.025 mg/l TDZ was better than that treated with MJ alone. When MJ alone was added to culture medium, asiaticoside contents in leaves were higher than that of control after 7 days of treatments. The maximum level of bAS (β-amyrin synthsae) mRNA in leaves of whole plant treated TDZ and MJ was transiently observed after exposure to 5 days. These results showed the up-regulation of bAS gene by adding TDZ and MJ at the molecular level, however, synergic effects of TDZ and MJ on asiaticoside biosynthesis were not testified.

Plants have been known to accumulate a very diverse range of triterpene saponins. We have investigated the regulation of saponin biosynthesis in higher plants using Centella asiatica (L.) Urban as a model plant. Effects of a feeding precursor on asiaticoside production from leaves and on the level of two-type OSCs mRNA were investigated. As a feeding precursor, squalene negatively affected the levels of CYS and bAS mRNA, but it also decreased the production of asiaticoside from whole plants. Plant hormones regulate secondary metabolism, and in plant tissue cultures they could affect both culture growth and secondary metabolite production. Although enhancement of asiaticoside production from whole plant cultures by addition of TDZ (thidiazuron) has been reported, the positive effect of TDZ on the levels of OSCs transcripts was not observed.

A protocol is described for rapid multiplication of Zanthoxylum piperitum DC. (Rutaceae), an important aromatic and medicinal plant, through shoot-tip explant cultures. Murashige and Skoog (MS) medium supplemented with various concentrations of N-6-benzyladenine (BA), N-6-benzylaminopurine (BAP) and thidiazuron (TDZ), in single or in combination with α-naphthaleneacetic acid (NAA), was used to determine the rate of shoot proliferation. N-6-benzyladenine (BA) used at 0.5mg/l, was the most effective in initiating multiple shoot proliferation at the rate of 23 microshoots per shoot-tip explants after 40 days of culture. Shoot multiplication increased 1.2-fold in each successive subculture. Induction of rooting (98%) was achieved by transferring the shoots to the same basal medium containing 2 mg/l indole-3-butyric acid (IBA). Plantlets went through a hardening phase in a controlled growth chamber, prior to in vivo transfer. These results represented that possible application for the mass production of plantlets through in vitro culture system of Zanthoxylum piperitum DC.

The effects of basal media, carbon, nitrogen, phosphate and some major macro elements on growth and shikonin production in Lithospermum erythrorhizon hairy root culture were studied. Among examined media, growth of hairy root cultured in B5 liquid medium was rapid, whereas shikonin production was high in MS liquid medium. Under B5 basal medium, sucrose concentration for optimal growth and shikonin production was 9% and 4% respectively. The growth and shikonin production on pH changes in B5 medium resulted little effect in pH 5.8 to pH 8.8 ranges, whereas growth was decreased dramatically in both above 8.8 and under 5.8. Nitrogen source and concentration effected on the growth and shikonin production. The highest growth rate was in B5 medium (50 mM KNO3 and 1 mM NaH2PO4), whereas the highest shikonin production was in the condition supplemented with 5 mM KNO3 and 10 mM NaH2PO4.