Localization of the Biflavonoid Fraction in Plant Leaves, With Special Reference to Agathis robusta (C. Moore Ex F. Muell.) F.m. Bail

Abstract

Aluminium chloride-induced fluorescence was used to localize biflavonoids in fresh leaf sections of Agathis robusta. This method indicates that the biflavonoids are confined to the outer periclinal wall and anticlinal walls of the epidermal cells. This was confirmed by extraction and chromatographic analysis of epidermal peels, cuticular scrapings and middle leaf tissue fractions. A survey of representatives of the Psilotales, and of all orders of the gymnosperms using aluminium chloride-induced fluorescence, indicates that localization of biflavones in the cuticle is a general feature of biflavonoid-containing plants. Members of the Pinaceae and Gnetales, in which biflavonoids have not been found, show no such fluorescence in the cuticle. The possible functional roles of biflavonoid accumulation are discussed. It is postulated that biflavones serve a protective role against invasion of the leaf by microorganisms and/or attack by leaf-eating insects.