FOLIAR PHENOLICS OF NEBRASKA SANDHILLS PRAIRIE GRAMINOIDS - BETWEEN-YEARS, SEASONAL, AND INTERSPECIFIC VARIATION

Because of their potential as antiherbivore defenses, plant phenolics elicit considerable attention. We made quantitative and qualitative an alyses 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 hall ii Hack., Andropogon scoparius Michx., Bouteloua gracilis (H.B.K) Lag. ex Griffiths, Calamovilfa longifolia (Hook.) Scribn., Carex heliophil a Mack., and Stipa comata Trin & Rupr. Their leaves contain low levels of phenolics that vary significantly among species. A more detailed e xamination of the three species with the highest levels of phenolics s howed among-year, seasonal, and spatial heterogeneity in the levels of total phenolics. In all seven species, the majority of the specific p henolics present have the chromatographic properties of phenylpropanoi ds and are likely to be present as sugar-linked derivatives such as fr ee glycosides or cell wall-bound phenolics. These species do not conta in condensed tannins. The absence of other common kinds of secondary m etabolites indicates that these graminoids are unlikely to have signif icant chemical defenses, at least in terms of substances likely to be active against mammalian herbivores. In this, they exemplify the situa tion thought typical for prairie graminoids.