Effect of hydrogen peroxide on somatic embryogenesis of Lycium barbarum L.

The subject of this study is inducing somatic embryogenesis in the callus of Lycium barbarum L, and determining hydrogen peroxide in somatic embryogenesis. First of all, the activities of three antioxidant enzymes (SOD, peroxidase, catalase) in different stages of somatic embryogenesis were determined. The result showed that the activity of SOD gradually increased in the early days of differentiation culture and gradually decreased along with further division and development of multi-cellular embryos. The peak of SOD activity arose on the seventh day of culture, that was exactly the time that multi-cellular embryos were formed by embryogenic cell division. Peroxidase and catalase activities were high in callus, and rapidly decreased in the early days of the differentiation culture. Aminotriazole (AT) as the inhibitor of catalase inhibited catalase activity by 85% and increased the frequency of somatic embryogenesis. Diethyldithiocarbonate (DDC) as the inhibitor of SOD inhibited SOD activity by 80% and decreased the frequency of somatic embryogenesis. Therefore, we suggest that there is an increase of intracellular H2O2 in the formation of embryogenic cells. Secondly, the effect of different concentrations of exogenous hydrogen peroxide (H2O2) in somatic embryogenesis were determined. The frequency of somatic embryogenesis reached its maximal value after treatment with 200 mu M exogenous H2O2 for 15 days. Higher concentrations of H2O2 (300 mu M) inhibited the formation of somatic embryos. In addition, the intracellular levels of H2O2 were also determined in somatic embryogenesis. Intracellular levels of H2O2 were higher in the formation of embryogenic cell than in callus. The results showed that the differentiation of embryogenic cells was affected by H2O2. Higher levels of intracellular H2O2 induced and promoted somatic embryogenesis. Finally, the study also discusses the effect of oxidative stress in cell differentiation and somatic embryogenesis. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.