Effects of UV-B radiation, cold and desiccation stress on rutin concentration and rutin glucosidase activity in tartary buckwheat (Fagopyrum tataricum) leaves

To study the physiological role of flavonoids in tartary buckwheat (Fagopyrum tataricum) leaf, we focused on rutin and rutin glucosidase activity. First, we investigated the rutin concentration and rutin glucosidase activity in leaves from different positions of tartary buckwheat. The rutin concentration by dry weight was high in young leaves (more than 20% in unexpanded young leaves) and decreased along with the decrease of leaf position. Rutin glucosidase activity by dry weight was also high in young leaves and decreased along with the decrease of leaf position. Most rutin and rutin glucosidase activities were distributed in the epidermis. To obtain further information about the physiological role of rutin, tartary buckwheat leaf was treated with stress using UV-B radiation, cold and desiccation. The rutin concentration was increased 122% by UV-B radiation and 129% by desiccation treatment. On the other hand, rutin glucosidase activity was increased 363% by UV-B radiation, 190% by cold treatment and 158% by desiccation treatment over the control. From these results, we propose that rutin and rutin glucosidase activity may be related to enhancement of the defense system against stress conditions in tartary buckwheat leaf.