Section D Physiology and Cultivation Differences between Singlet Oxygen and 8 202 Scavenging Activities among Various Organs of Common and

Abstract: The resistance to oxidation caused by light irradiation was investigated among different organs in common and Tartary buckwheats. The scavenging activities of hydrogen peroxide and singlet oxygen produced by UV or strong photosynthetic active radiation were evaluated by photon counting of visible light using chemiluminescence. A second method of evaluation was the time-resolved photon counting of near-infrared induced by YAG laser. In each species. the leaf, stem, flower. and seed were separated at early and late stages of the flowering period, and were dried and ground into flour. Hot water extracts of the flowers had a shorter lifetime for singlet oxygen than that of the leaf. stem, and fruit extracts for both species. Scavenging activities of H202 in the leaf and flower samples were higher than other organs in each species and those in common buckwheat were higher compared with Tartary buckwheat. There was a significant negative correlation between the singlet oxygen lifetime and the scavenging activity of H202. The flower has a higher antioxidant activity than other organs in each buckwheat species due to the presence of water soluble compounds