Shade, Irrigation and Fertility Effects on Biomass Production and Flavonoid Content in American skullcap.

American skullcap (Scutellaria lateriflora), native to moist habitats in eastern North America, is valued for its medicinal properties associated with various flavonoids. Information on how growing conditions affect yield and concentration of flavonoids is lacking. A 2X2X3 split plot factorial experiment was established in Shorter, Alabama, to determine effects of growing conditions on dry matter yield (DMY) and flavonoid content. 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) and chicken litter (100 kg N, 50 kg P and 123 kg K ha-1). Shade formed the main plot units; irrigation and nutrient factors were randomized within subplots. Seedlings were transplanted on April 30, 2007. Shoots were harvested at full bloom on June 29 and September 5, 2007. Dry matter yield was 39% higher at second than at first harvest. At first harvest, shade did not affect DMY; irrigation and nutrients increased DMY by 23.7% and 45.7%. At second harvest, shade increased DMY by 63.4%; irrigation had no effect and nutrient application increased DMY by 10.4%. The flavonoid, baicalin, was found at higher concentration and yield under all experimental conditions followed by baicalein. Chrystin and wogonin were found at very low concentration and yield. Baicalin and baicalein concentrations were 32% and 50% higher, respectively, at harvest 1 than at harvest 2. Shade decreased Baicalin and baicalein concentration by 28 % and 15%, increased Baicalin and baicalein yield by 6% and 16%. Irrigation increased baicalin yield by 27% under full sun, baicalein yield and concentration by 34% and 35%. Nutrients increased baicalein concentration and yield by 16% and 47% and increased baicalin yield by 11%. Results of second year will also be presented.