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.Leaves of Agathis robusta were particularly suitable material in which to localize the biflavonoid fraction. Previous studies o n the leaves of this and several other species of the genus Agathis (Khan et al. 1972;Varshney et al. 1973) indicated that biflavonoids constitute by far the major proportion of the flavonoid fraction. Furthermore, unlike the scale-leaves of many conifers, the broad dorsiventral leaves of Agathis species are relatively easily separable into epidermal and mesophyll fractions, allowing confirmation of observations by t.1.c. analysis of extracts from these fractions. For these reasons the study concentrates o n Agathis robusta. However, a brief survey of the aluminium chlorideinduced fluorescence i n representatives of all orders of gymnosperms, as well as the Psilotales, is also included. Materials and MethodsUnless otherwise stated, all studies were carried out on mature leaves of specimens cultivated in the grounds of the University of New South Wales: voucher specimens have been lodged with UNSW.

Assessing Chemical Diversity in Psilotum nudum (L.) Beauv., a Pantropical Whisk Fern That Has Lost Many of Its Fern-Like Characters

“…Our localization data sets for amentoflavone (chlorenchyma) are also consistent with the literature for other plants. For example, amentoflavone was accumulated preferentially in the leaf epidermis in Agathis robusta (Gadek et al, 1984) and Ginkgo biloba (Beck and Stengel, 2016). An interesting, as yet unanswered, question pertains to the functional role of the differential subcellular localization one would predict for the metabolites of interest.…”

“…An interesting, as yet unanswered, question pertains to the functional role of the differential subcellular localization one would predict for the metabolites of interest. Psilotin is likely stored in the vacuole, in analogy to other (polar) phenolic glycosides (Wink, 1993), while amentoflavone is an apolar biflavonoid aglycone that was previously found to be associated with cell walls (Gadek et al, 1984). Both locations allow for the sequestration of these bioactive metabolites, thereby protecting cellular metabolism in different subcellular locations (Agapakis et al, 2012).…”

Flash pyrolysis of the outer cortical tissues in Lower Devonian Psilophyton dawsonii

“…Lignin, phenolic derivatives, e.g. biflavonoids, which exist in the cuticle and epidermis of many seed plants (Robberccht & Caldwell, 1983;Gadek et al, 1984), and hydroxycinnamic acids (Kolattukudy, 198 1;Holloway, 1982) have that role today, when UV levels are much the same as in the Siluro-Devonian (Caldwell, 1979). Recent genetic studies with Arubidopsis mutants have provided direct evidence that flavonoids play an important role in UV-protection and that they function, at least in part, by shielding DNA from UV-induced damage (Cooper-Driver, pers.…”