Shade, Irrigation, and Nutrients Affect Flavonoid Concentration and Yield in American Skullcap
2016
Similien, Arsène | Shannon, Dennis A. | Wesley Wood, C. | Rimando, Agnes M. | Kemppainen, Barbara W. | van Santen, Edzard | Joshee, Nirmal
American skullcap (Scutellaria lateriflora L.) is valued for its sedative properties that are associated with flavonoids. Information on how growing conditions affect flavonoid content is lacking. A 2 by 2 by 3 factorial experiment was conducted in a randomized complete block design (r = 4) with a split-plot restriction on randomization to explore effects of light, irrigation, and nutrient application on flavonoid concentration and yield in American skullcap. Treatment factors were shade (40% shade vs. no shade), irrigation (applied at 30 kPa vs. no irrigation), and nutrients (no fertilizer vs. fertilizer [100 kg N, 68 kg P, 42 kg K ha⁻¹] or chicken litter [100 kg N, 50 kg P, 123 kg K ha⁻¹]). Shade formed the main plot units; irrigation and nutrients were randomized within subplots. Aboveground biomass was harvested twice in both 2007 and 2008. Dried, finely ground samples were extracted and analyzed for flavonoid concentration using high-performance liquid chromatography (HPLC). The flavonoid baicalin was present in highest concentration and yield, followed by baicalein; wogonin and chrysin were present in only small amounts. Flavonoid concentration was 72% higher in full sun, 15% higher with irrigation, while added nutrients decreased baicalin concentration by 6% but increased baicalein by 16%. Significant interactions of shade × irrigation and shade × nutrients were also observed. Flavonoid yield was 25% higher under shade, 92% higher with irrigation, and 43% higher with added nutrients. Significant interactions of shade × irrigation, shade × nutrients, and irrigation × nutrients were also observed. Increasing biomass yield had a greater effect on total flavonoid harvested than did increasing flavonoid concentration.
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