Somatic embryogenesis of Panax ginseng in liquid cultures: a role for polyamines and their metabolic pathways

A callus with embryogenic capacity was generated from root sections of Panax ginseng and used as an inoculum source for embryogenic liquid cultures in a three-step process: - a suspension culture of cell aggregates in the presence of an auxin/cytokinin mixture, - an induction medium containing auxin only (for 5 to 30 days), - a regeneration medium containing cytokinin only (for one month). Up to 25 embryos were recovered per 2.5 g of aggregates in these conditions. Incorporation of polyamines or their precursors arginine and ornithine into either the induction or regeneration media increased the number of embryos produced by up to 4 times. Inhibitors of both biosynthesis and biodegradation of polyamines reduced the number of embryos. These results support earlier findings of the role of polyamines in the process of somatic embryogenesis. The success of these liquid cultures opens up the possibility of producing somatic embryos of Panax ginseng in bioreactors.