Ascorbic Acid and Citric Acid Reduce Explant Darkening during Shoot Tip Culture of Adonis amurensis

This study was conducted to reduce explant darkening during the shoot tip culture of Adonis amurensis. Explant darkening at initial stage of the culture was found to decrease the explant survival rate about 20%. To reduce the darkening, shoot tips were soaked in an antioxidant mixture of 150 ㎎ㆍL?¹ ascorbic acid and 150 ㎎ㆍL?¹ citric acid or in an antioxidant mixture of 300 ㎎ㆍL?¹ ascorbic acid and 300 ㎎ㆍL?¹ citric acid for 30 min before inoculation. In root development, in vitro multiple buds were cultured on MS (Murashige and Skoog) media containing antioxidants (150 ㎎ㆍL?¹ ascorbic acid, 150 ㎎ㆍL?¹ citric acid, or 150 ㎎ㆍL?¹ ascorbic acid + 150 ㎎ㆍL?¹ citric acid). When the explants were soaked in antioxidants, explant darkening significantly decreased and their survival rate was improved to 56%. When the antioxidants were added to the medium, on the other hand, the survival rate of explants was improved to 48%. However, phenolic compounds decreased during the culture without antioxidants, and little phenolic compounds were detected in more darkened explants. To prevent darkening, the antioxidant soaking treatment was more effective than the antioxidant addition to medium. In addition, combined treatment of the antioxidants was more effective to reduce the darkening than the single antioxidant treatment.