Foliar phenolics of nebraska sandhills prairie graminoids: Between-years, seasonal, and interspecific variation

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Abstract
Because of their potential as antiherbivore defenses, plant phenolics elicit considerable attention. We made quantitative and qualitative analyses of phenolics, alkaloids, cyanogenic glycosides, and saponins in the dominant graminoids of a Nebraska Sandhills prairie. We examined the foliage of seven species:Agropyron smithii Rydb.,Andropogon hallii Hack.,Andropogon scoparius Michx.,Bouteloua gracilis (H.B.K) Lag. ex Griffiths,Calamovilfa longifolia (Hook.) Scribn.,Carex heliophila Mack., andStipa comata Trin & Rupr. Their leaves contain low levels of phenolics that vary significantly among species. A more detailed examination of the three species with the highest levels of phenolics showed among-year, seasonal, and spatial heterogeneity in the levels of total phenolics. In all seven species, the majority of the specific phenolics present have the Chromatographic properties of phenylpropanoids and are likely to be present as sugar-linked derivatives such as free glycosides or cell wall-bound phenolics. These species do not contain condensed tannins. The absence of other common kinds of secondary metabolites indicates that these graminoids are unlikely to have significant chemical defenses, at least in terms of substances likely to be active against mammalian herbivores. In this, they exemplify the situation thought typical for prairie graminoids.