SITES OF NARINGIN BIOSYNTHESIS IN GRAPEFRUIT SEEDLINGS

Radioactively-labeled acetate and phenylalanine were fed to intact and detached tissues of grapefruit seedlings to characterize the biosynthesis and subsequent metabolic fate of the flavanone glycoside naringin. Radiolabeled naringin was biosynthesized from both precursors in detached leaves, but not in detached stems or roots. Young leaves were much more efficient at incorporating label into naringin than older leaves. When radiolabeled precursors were fed to whole seedlings, labeled naringin was found in all parts of the plant, including stems and roots. This suggests that naringin is synthesized in young, rapidly growing leaves, then transported to other parts of the plant.