Flavonoid accumulation in common buckwheat (Fagopyrum esculentum) sprout tissues in response to light

Abstract

The content and accumulation patterns of flavonoids in response to light were investigated in common buckwheat (Fagopyrum esculentum) sprouts over the course of 9 days. Buckwheat sprouts were grown under fluorescent (FL), red (RL), and blue (BL) light sources, as well as in darkness, and their extracts were analyzed. Sprout elongation and chlorophyll content were high in the presence of red light. The contents of the major buckwheat sprout flavonoids, orientin, isoorientin, vetexin, isovetexin, and rutin all peaked 5 days after germination under all four growth conditions, then gradually decreased. Sprouting cotyledons accumulated around 1.5-fold more orientin, isoorientin, quercetin-3-O-robinobioside, and rutin in the presence of red light, including from the RL and FL light sources, than in blue light alone. The C-glycosyl flavones, orientin, isoorientin, vetexin, and isovetexin, were not detected in the stem tissues of the hypocotyls, but C-glycosyl flavonols, such as quercetin-3-O-robinobioside and rutin, were present, and were twice as abundant under BL and FL than in the RL and darkness conditions. In the root tissues, a small amount of C-glycosyl flavonols was detected after BL exposure only; however, the other flavonoids were not detected at all. These results indicated that red light induces flavonoid biosynthesis in the cotyledons of buckwheat seedlings, but blue light has a greater effect on the accumulation of C-glycosyl flavonols in other seedling tissues.