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Document Type

Thesis - University Access Only

Award Date

2000

Degree Name

Master of Science (MS)

Department / School

Plant Science

First Advisor

R. Neil Reese

Abstract

The narrow-leafed purple coneflower (Echinacea angustifolia D.C.) is a perennial native to North America. Echinacea angustifolia is found on dry prairies from Texas to Saskatchewan, west to the Rocky Mountains and east to Minnesota. Echinacea angustifolia produces many biologically active compounds that have shown allelopathic effects on lettuce (Lactuca sativa), switchgrass (Panicum virgatum) and prairie dropseed (Sporobolus heterolopis). Natural allelopathic chemicals have the potential of being used for the production of herbicides that are environmentally safe. These allelopathic compounds possess components that could be used in the development of new herbicides. The objectives of this work are to identify the ethanol soluble compounds of E. angustifolia and to examine their potential for use as natural herbicides. The allelopathic potential of ethanol soluble compounds from E. angustifolia roots from five populations (South Dakota, North Dakota, Wyoming, Kansas, and Nebraska) were examined. A common allelopathy bioassay was performed using lettuce seeds germinated in the presence of the ethanol extracts pipetted on filter paper. The extracts were brought to dryness and were resuspended in deionized water. Analysis of the seed assay was completed by measuring percent germination and root elongation of 25 lettuce seeds per replication for extracts from each of 100 E. angustifolia plants (20 plants per population). Results from the lettuce seed bioassay experiment showed that germination in the presence of Echinacea extracts ranged from 100% to 0%. As collection sites moved southward, the allelopathic potential tends to decrease. Root extracts were concentrated by evaporation and analyzed by reverse phase high performance liquid chromatography (HPLC) using a C-18 column. Absorbancy was measured at 210-nm and 254-nm. HPLC analyses revealed eleven significant peaks in all populations. The parameters of germination, root elongation and peak area were used to conduct a multiple regression analyses. These results showed that compounds identified as peak numbers three and six contribute to 72 % of the allelopathic effects of E. angustifolia root extracts. Lettuce seed germination assays showed that peaks three and six caused significant reductions in both germination and root elongation. The combined peaks were found to have an additive effect on root elongation but a synergistic effect on germination. Since peaks three and six were of most interest they were further identified by comparison HPLC analyses performed by Bauer and Remiger (1989) and NMR (nuclear magnetic resonance) at the University of Illinois, Urbanna. Peak three was identified as undeca-2E-ene-8, 10-diynoic acid isobutylarnide and peak six was identified as dodeca-2E,4E,8, 10E-tetraenoic acid isobutylarnide.

Library of Congress Subject Headings

Echinacea (Plants)
Allelopathic agents
Plant extracts
Herbicides -- Environmental aspects

Format

application/pdf

Publisher

South Dakota State University

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