Flavonoid variation in the genus briza |
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Authors: | Christine A. WilliamsB.G. Murray |
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Affiliation: | Department of Botany, The University, London Road, Reading RG1 3AQ, Berks., LondonEngland |
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Abstract: | During a survey of 6 Eurasian and 10 South American Briza species for leaf flavonoids, 27 components were found. Twelve of these were identified: tricin 5-glucoside, tricin 7-glucoside, quercetin 3-glucoside, kaempferol 3-glucoside, vitexin, isovitexin, orientin, iso-orientin, and the 4′-O-glucoside of all 4 glycoflavones, 3 of which are reported for the first time. The Eurasian species, with the exception of Briza maxima, are remarkably uniform in their flavonoid pattern, accumulating mainly vitexin and isovitexin; whereas the South American species are characterized by the presence of orientin, iso-orientin and 9 unidentified flavonoids. In Briza media and the South American species, ploidy level is shown to play a large part in flavonoid variation. Examination of 12 diploid and 8 autotetraploid plants of B. media revealed that diploids accumulate vitexin and isovitexin, whereas tetraploids accumulate orientin and iso-orientin, autotetraploidy having apparently upset regulatory genes in the formation of the flavone C-glycosides. Mild alkaline treatment of both isovitexin and iso-orientin was found to give 100% conversion to the corresponding 8-C-glucoside. |
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Keywords: | Briza Gramineae chemotaxonomy flavone C-glycosides tricin glycosides ploidy level plant geography |
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