Submitted to: Journal of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: 3/9/2011
Publication Date: 7/11/2011
Citation: Estell, R.E., Fredrickson, E.L., James, D.K., Anderson, D.M. 2011. Distribution of antiherbivory compounds in Flourensia cernua [abstract]. Journal of Animal Science. 89,E-Suppl. 1, p. 47-48, M124.
Technical Abstract: Flourensia cernua is serving as a shrub model to study the influence of terpenes on intake by livestock at this location. Two studies (n=20 plants per study) were conducted to examine within plant distribution of volatile compounds to improve sampling protocol. Leaves from 3 positions (outer canopy, subcanopy, and basal) were collected from 4 quadrants (based on ordinal direction) in Exp. 1. Leaves were removed from 2 leaders of current year's growth for each position in each quadrant. In Exp. 2, 10 leaders of current year's growth were collected from the outer canopy in each quadrant and 3 leaf age categories were formed by separating leaders into thirds and removing leaves. Chemicals were extracted from 5 leaves in duplicate with ethanol and analyzed with gas chromatography/mass spectrometry. Data were log transformed and analyzed by univariate ANOVA and means were separated using Tukey's HSD. Ninety-three volatile compounds (including 15 unknowns) were present on the leaf surface of F. cernua. Only 7 compounds (including 3 unknowns) in Exp. 1 and 9 in Exp. 2 differed (P<0.05) among quadrants, and no consistent effect of quadrant was observed in either study. In Exp. 1, 31 compounds differed (P<0.05) among leaf positions, but outer canopy and subcanopy leaves did not differ for any compound. Basal leaves contained greater concentrations than outer canopy and subcanopy leaves for 10 compounds, and less than the other 2 positions for 10 compounds. Thirty-two compounds differed for leaf age in Exp. 2, with immature leaves containing greater concentrations than mature leaves for 30 compounds and greater than the middle age category for 26 compounds (P<0.05). Total concentration (cumulative concentration of all compounds) did not differ among leaf positions but differed for leaf age (greater in immature than mature leaves; P<0.05). Compounds that differed in Exp. 1 were represented about equally by mono- and sesquiterpenes, whereas compounds affected by leaf age were predominantly sesquiterpenes (only 3 of 32 were monoterpenes). Both leaf position and age affect terpene concentrations and sampling variability in this shrub.