In situ identification, localization and quantification of flavones in petals and green leaves of Silene pratensis grown under different light regimes

Abstract

Quartz optic microscopy with variable wavelength illumination was used to locate and quantify the ultraviolet absorbing flavone isovitexin 7-0-qlucoside in leaf and petal epidermis in Silene pratensis. Mean vacuolar absorption spectra and mean cell wall thickness were used to estimate flavone contents in different organs. The flavone spectrum in vivo coincides with that found in vitro (absorption peaks at 273 and 335 nm). Flavone concentration in the green leaves is determined by the light levels under which individual plants were raised; with low levels (8,000 lux) a few upper epidermal cells show faint absorption at 335 nm. In plants raised at 18,000 lux, 60-70 % of the upper epidermal cells absorbed at 334 nm and flavone concentration in the absorbing cells was 1-3 mM. In plants raised under high light intensity (36,000 lux), most of the upper epidermal cells absorbed at 335 nm and the flavone concentration in the cells ranged from 8.5 to 15 mM. In the high light intensity plants some lower epidermal cells also absorb at 335 nm (flavone concentrations 2-5 mM). In all plants investigated, nearly all the cells of the upper epidermis of the netals absorb strongly at 335 nm (concentrations exceeding 19 mM).