Submitted to: Biochemical Systematics and Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/12/2016
Publication Date: 3/1/2016
Publication URL: http://handle.nal.usda.gov/10113/61950
Citation: Estell, R.E., Fredrickson, E.L., James, D.K. 2016. Effect of light intensity and wavelength on concentration of plant secondary metabolites in the leaves of Flourensia cernua. Biochemical Systematics and Ecology. 65:108-114.
Interpretive Summary: Shrub expansion into grasslands is a concern to livestock producers and land managers. Many shrubs contain chemicals that cause them to be unpalatable to livestock and wildlife. We have been studying how plant chemicals affect tarbush consumption by livestock. In this study, we examined the effect of shade and UV light restriction on amount of terpenes and phenolics. Total phenolics were decreased by shading, while total volatiles were increased by UV restriction. Our results suggest climatic shifts may affect palatability of non-preferred shrubs.
Technical 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.