Submitted to: American Phytopathological Society Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 5/22/2000
Publication Date: N/A
Technical Abstract: Phototoxins may play important roles in plant defenses, and their synthesis can be induced by pathogen and insect attack. Hypericins, a family of anthraquinones in Hypericum perforatum L. (St. John's Wort), exhibit anti-microbial, anti-viral, and antifeedant properties in vitro due to the formation of singlet oxygen when exposed to light. We are interested in determining whether hypericin is involved in defense strategies of St. John's Wort. Samples from eight wild populations of H. perforatum were collected at flowering and analyzed for hypericins using HPLC. Total plant yields were from 0.0003 - 0.1250% DW hypericin and 0.0019 - 0.8458% DW pseudohypericin. Hypericin concentrations were highest in reproductive tissues, followed by leaf and stem tissues, except for two sites where leaf levels were high and extensive herbivory had occurred. The elevation of hypericins from these sites might represent a plant defense response or be due to selective pressure from herbivory over time, giving rise to variant populations. We are currently examining whether hypericin can be induced under laboratory conditions.