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A natural herbicide useful against plants susceptible to allelopathic effects

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Title: The effect of UV exposure on the allelopathic activity of sunflower on the tall morning glory
Subject: Environmental Sciences
Subcategory: Botany / Chemistry
Grade level: High School - Grades 10-12
Academic Level: Advanced
Project Type: Experimental
Cost: High
Awards: Google Science Fair Finalist
Affiliation: Google Science Fair
Year: 2011
Materials: Helianthus annuus seeds, Ipomoea purpurea seeds, deionized water, Folin-Ciocalteu reagent, sodium carbonate solution, gallic acid solution, bleach solution, orbital shaker
Techniques: Folin-Ciocalteu assay, spectrophotometric analysis
Description: Increasing global UV levels may stimulate allelochemical production in Helianthus annuus (sunflower) and the leachates could be used as natural herbicides against plants susceptible to allelopathic effects. Helianthus annuus (Sunflower) is known to inhibit the growth of plants like Ipomoea purpurea (Tall Morning Glory) via allelochemicals produced in its leaves and other parts. Allelochemicals are secondary metabolites that affect growth and development of neighbouring organisms such as other plants, algae, bacteria or fungi, in response to various environmental stresses. I investigated the effect of ultraviolet exposure of Helianthus annuus on water-soluble allelochemical production, such as phenolic compounds, in Helianthus annuus leaf leachates and their effect on the growth and physiology of Ipomoea purpurea seedlings. I grew Helianthus annuus plants for 4 weeks and then irradiated them daily for 1 week with UV for 0, 3, 6, 9 and 12 hours while also providing them with a total of 12 hours of visible light from a florescent lamp. I then prepared 3% aqueous leaf leachates and determined their content of phenolic compounds using the Folin-Ciocalteu assay followed by spectrophotometric analysis at an absorbance of 750nm. After that, I treated Ipomoea purpurea seeds with these leachates for 1 week and monitored the percentages of its germination, respiration rates, dry mass, root physiology, and root and shoot lengths.
Link: sites.google.com...

Allelochemicals as Growth Regulators and Natural Herbicides

Allelopathy is a biological phenomenon by which an organism produces one or more biochemicals that influence the growth, survival, and reproduction of other organisms. These biochemicals are known as allelochemicals and can have beneficial (positive allelopathy) or detrimental (negative allelopathy) effects on the target organisms. Allelochemicals with negative allelopathic effects are an important part of plant defense against herbivory.

Some plants produce natural herbicides, such as the genus Juglans (walnuts), or the tree of heaven; such action of natural herbicides, and other related chemical interactions, is called allelopathy.

The possible application of allelopathy in agriculture is the subject of much research. Current research is focused on the effects of weeds on crops, crops on weeds, and crops on crops. This research furthers the possibility of using allelochemicals as growth regulators and natural herbicides, to promote sustainable agriculture. A number of such allelochemicals are commercially available or in the process of large-scale manufacture. For example, Leptospermone is a purported thermochemical in lemon bottlebrush (Callistemon citrinus). Although it was found to be too weak as a commercial herbicide, a chemical analog of it, mesotrione (tradename Callisto), was found to be effective. It is sold to control broadleaf weeds in corn but also seems to be an effective control for crabgrass in lawns. Sheeja (1993) reported the allelopathic interaction of the weeds Chromolaena odorata (Eupatorium odoratum) and Lantana camara on selected major crops.

There is also evidence that the roots of some perennials such as couch grass exude allelopathic chemicals which inhibit the growth of other nearby plants.

See also:
Weed Control

Source: Wikipedia (All text is available under the terms of the Creative Commons Attribution-ShareAlike License)

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