The changes of redox status during the cultures and their meanings in regulating somatic embryogenesis were investigated in ginseng callus cultures. When calli were placed on the media containing 2.4-D (+2.4D media) longer than 8 months, somatic embryos began to appear. Unless the cultures on +2,4-D media passed 8 months before transfer to media lacking 2.4-D (-2.4-D media), somatic embryos never appear. ed. During the 8 months on + 2,4-D media, reductants, which indicate reductive status, showed induction in the middle periods and declined thereafter. On the contrary, peroxidase, which indicates oxidative status, was high at first and decreased during the middle periods and showed induction in the late periods. Somatic embryos began to arise when reductive status was low and oxidative status was high. It seems that transition of redox status on the +2,4-D media during 8 months plays some roles on triggering somatic embryogenesis in ginseng calli.
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