@article {JRN54522, title = {Effect of light intensity and wavelength on concentration of plant secondary metabolites in the leaves of Flourensia cernua}, journal = {Biochemical Systematics and Ecology}, volume = {65}, year = {2016}, month = {04/2016}, pages = {108-114}, chapter = {108}, abstract = {

Flourensia cernua (tarbush) is a shrub that has encroached into grasslands in many areas of the northern Chihuahuan Desert and contains high levels of carbon-based secondary compounds. Concentrations of secondary compounds are affected by numerous biotic and abiotic influences, including amount and wavelength of solar radiation. However, responses to shade and ultraviolet light restriction are inconsistent among plant species and compound class. We conducted a three-year study to evaluate the effect of shade and UV light restriction on total phenolic and terpene concentrations in tarbush. Sixty plants were randomly assigned to one of three treatments (control, UV light restriction, or 50\% incident light restriction). Mean concentrations of total phenolics and total volatiles in tarbush were 82.4 and 12.5 mg/g DM, respectively. Total phenolics did not differ between UV-restricted and control plants, but were lower in shaded plants than the other treatments (P \< 0.05).\  Total volatiles tended to be greater for the UV-restricted treatment than control plants (P= 0.056), with shaded plants not different from either treatment. Treatment effects were detected for 18 individual compounds (P \< 0.05). Our results partially support the hypothesis that UV restriction and shading alter carbon-based secondary chemical concentrations.

}, keywords = {Flourensia cernua, phenolics, plant secondary metabolites, shade, terpenes, ultraviolet light}, doi = {10.1016/j.bse.2016.02.019}, url = {/files/bibliography/16-006.pdf}, author = {Richard E. Estell and E.L. Fredrickson and D. K. James} } @article {49847, title = {Within-plant distribution of volatile compounds on the leaf surface of Flourensia cernua}, journal = {Biochemical Systematics and Ecology}, volume = {48}, year = {2013}, month = {01/2013}, pages = {144-150}, chapter = {144}, abstract = {

We are using Flourensia cernua as a shrub model to study the role of terpenes on intake by livestock. Two experiments were conducted to examine distribution of volatile chemicals within a plant in an effort to minimize sample variability. In Exp. 1, leaves (current year\&$\#$39;s growth) were collected from 20 tarbush plants. Two leaders were sampled from each of three positions (outer canopy, subcanopy, and basal) in all four quadrants (based on ordinal direction). In Exp. 2, 10 leaders of current year\&$\#$39;s growth were removed from another 20 plants. Leaders were collected from the outer canopy of each quadrant and separated into thirds before removing leaves, thereby creating three leaf age categories. Volatile compounds were extracted with ethanol and analyzed with gas chromatography/mass spectrometry. Ninety-four chemicals (including 15 unknowns) were present on the leaf surface of F. cernua. Although 14 and 21 compounds differed (P \< 0.05) among quadrants in Exp. 1 and 2, respectively, no consistent quadrant effect was detected in either study. Leaf position differed (P \< 0.05) for 52 chemicals in Exp. 1 but outer canopy and subcanopy leaves differed for only 10 compounds. In Exp. 2, 63 compounds differed among leaf age categories. Immature leaves contained greater concentrations of 46 chemicals (P \< 0.05) than moderate or mature age categories, but moderate and mature leaves differed for only seven compounds. Estimated total concentration (i.e., cumulative concentration of all compounds) was not affected by leaf position but varied among leaf age categories (P \< 0.05; immature \> moderate \> mature). Differences in leaf position were attributed about equally to mono- and sesquiterpenes, whereas leaf age was affected to a greater extent by sesquiterpenes. Leaf position and maturity both affect terpene concentration and sampling variability for tarbush. However, little difference was detected between subcanopy and canopy positions. Thus, by avoiding basal sprouts and sampling from the mid-point of current year\&$\#$39;s growth, sampling variation should be minimal.

}, keywords = {Flourensia cernua, leaf age, plant secondary metabolites, terpenes, volatiles, within-plant distribution}, doi = {10.1016/j.bse.2012.11.020}, url = {/files/bibliography/13-002.pdf}, author = {Richard E. Estell and D. K. James and E.L. Fredrickson and D.M. Anderson} } @article {51213, title = {Relationship of tarbush leaf surface terpene profile with livestock herbivory}, journal = {Journal of Chemical Ecology}, volume = {24}, number = {1}, year = {1998}, month = {January 1, 1998}, pages = {1-12}, abstract = {

Tarbush (Flourensia cernua DC.) is a Chihuahuan Desert shrub with a resinous leaf surface containing terpenes that may affect livestock herbivory. Cattle, sheep, and goats were densely stocked in paddocks containing tarbush in two consecutive years for six to nine days and defoliation of 160 plants was recorded daily. Plants were categorized as exhibiting high or low defoliation. Leaves were collected from these plants the third year for chemical analysis. A selection procedure was used to generate two variable sets closely related to defoliation category. One set contained 14 variables (dry matter, ash, -pinene, sabinene, 3-carene, p-cymene, limonene, camphor, bomeol, cis-jasmone, {\^a} -caryophyllene, alpha-humulene, ledene, and flourensadiol) and the other set contained 14 unidentified compounds. When subjected to multivariate analysis, each group distinguished between the two defoliation categories (P \<0.001 and P \<0.0019 for known and unknown variable sets, respectively). These data support the hypothesis that leaf surface chemistry of individual tarbush plants is related to extent of defoliation by livestock.

}, keywords = {diet selection, Epicuticular wax, Flourensia cernua, leaf surface chemistry, monoterpenes, sesquiterpenes}, doi = {10.1023/A:1022399426352 }, url = {/files/bibliography/608.pdf}, author = {Richard E. Estell and E.L. Fredrickson and D.M. Anderson and Kris Havstad and M.D. Remmenga} } @article {51322, title = {Tarbush leaf surface terpene profile in relation to mammalian herbivory}, year = {1996}, note = {NOT A DUPLICATE OF RECORD $\#$474}, month = {1996}, pages = {237-241}, publisher = {US Forest Service}, edition = {Gen. Tech. Rep. INT-GTR}, abstract = {

Cattle, sheep and goats were densely stocked in pad- docks containing tarbush (Flourensia cernua DC) for six to nine days and defoliation of 160 plants was recorded daily during two years. Plants were separated into high, moderate or low defoliation categories. Leaves were collected from plants during the same stage of maturity during the third year. Leaf surface compounds were extracted with ethanol and mono- and sesquiterpenes were ana-lyzed using gas chromatography/ion trap mass spectrometry. A set of 11 variables was identified that appeared most closely related to plant defoliation categories: dry matter, ash, limonene, camphor, borneol, a copaene, B caryophyllene, a pinene, p-cymene, cis-jasmone and caryophyllene oxide concentrations. This group distinguished among all three defoliation categories (P \< 0.03) when subjected to multivariate analysis. These data support the hypothesis that leaf surface chemistry is related to degree of defoliation of individual tarbush plants by livestock.

}, keywords = {diet selection, Epicuticular wax, Flourensia cernua, leaf surface chemistry, monoterpenes, sesquiterpenes}, url = {/files/bibliography/512.pdf}, author = {Richard E. Estell and E.L. Fredrickson and D.M. Anderson and Kris Havstad and M.D. Remmenga} } @article {51439, title = {Effects of organic solvents on use of tarbush by sheep}, journal = {Journal of Chemical Ecology}, volume = {20}, number = {5}, year = {1994}, month = {1994}, pages = {1137-1142}, abstract = {

Tarbush (Flourensia cernua DC) is a native perennial shrub prevelant in many parts of the Chihuahuan desert. Ruminants have exhibited limited use of tarbus leaves and new leaders as a forage during the summer growing season. Efforts to increase use of tarbush by lambs, through spraying with various organic solvents were unsuccessful. probably because of the highly variable response. However, complete immersion of tarbush in organic solvents (acetone and ethanol) increased (P\< 0.01) tarbush use by ram lambs when compared to unaltered tarbush using organic solvents enhanced acceptability of tarbush to sheep.

}, keywords = {Flourensia cernua, herbivory, leaf surface, organic solvents, sheep, tarbush}, doi = {10.1007/BF02059749}, url = {/files/bibliography/416.pdf}, author = {Richard E. Estell and D.M. Anderson and Kris Havstad} } @article {51440, title = {Secondary chemistry of the leaf surface of Flourensia cernua}, journal = {Biochemical Systematics and Ecology}, volume = {22}, number = {1}, year = {1994}, month = {1994}, pages = {73-77}, abstract = {

Epicuticular wax accounted for 9.2\% fo the dry weight of whole Flourensia cernua (tarbush) leaves. Leaf surface extracts of tarbush were analyzed for mono- and sesquieterpenoids with gas chromatography/mass spectrometry. Camphene, $\#$ mycrene, 3-carene, limonene, 1,8-cineole, borneol, cis jasmone, $\#$ caryphyllene, caryophyllene oxide and globulol were consistently present in tarbush. Concentrations of several unidentififed compunds were estimated. A great deal of plant to plant variability was detected in leaf surface mono= and sesquietepenoid concentration. Infomation obtained on surface chemistry might be exploited to enhance use of tarbush as a forage for domestic herbivores.

}, keywords = {epicuticular waxes, Flourensia cernua, leaf surface chemistry, monoterpenoids, sesquiterpenoids}, doi = {10.1016/0305-1978(94)90116-3}, url = {/files/bibliography/419.pdf}, author = {Richard E. Estell and Kris Havstad and E.L. Fredrickson and Gardea-Torresdey, J.L.} }