Relationship between peroxidase activity and organogenesis in Panax ginseng calluses

The changes of redox status during culture and their effect on organogenesis were investigated in ginseng callus cultures. Three kinds of Panax ginseng calluses (non-organogenic calluses, root-forming and bud-forming calli) 21 were obtained from each of the three examined auxins (2,4-D, IBA and NAA) at 2 mg l^–1 (9.05 M 2,4-D; 9.84 M IBA; 10.74 M NAA) concentration and 0.1 mg l^–1 (0.46 M) kinetin over 5 weeks. Peroxidase in the soluble fraction, which indicates oxidative status and shows a correlation with differentiation, was higher in bud-forming calluses cultured in the three types of auxins. On the other hand, reducing capacity (overall reducing capacity of glutathione, ascorbic acid, tocoferol, carotenoids and phenol) which indicates reductive status, was higher when these calluses grew on media containing 2,4-D but specially so in the case of non-organogenic calluses. With the three types of auxin used, the reducing capacity was always higher in non-organogenic calluses and lower in calluses with more organogenic capacity. It seems that organogenesis of calluses is conditioned by a high peroxidase activity in soluble fraction (equal to or more than 0.8 A430/mg protein per min) and therefore a low reducing capacity (less than 0.3 A760/g DW). On the other hand 2,4-D promotes proliferation whereas NAA promotes morphogenesis.