Growth regulation and other secondary effects of herbicides

Authors: VELINI, EDIVALDO - Sao Paulo State University (UNESP); TRINDADE, MARIA - Sao Paulo State University (UNESP); BARBERIS, RODRIGO - Sao Paulo State University (UNESP); Duke, Stephen

Submitted to: Weed Science
Publication Type: Review Article
Publication Acceptance Date: 1/5/2010
Publication Date: 7/6/2010
Citation: Velini, E.D., Trindade, M.L., Barberis, R.M., Duke, S.O. 2010. Growth regulation and other secondary effects of herbicides. Weed Science. 58:351-354.

Interpretive Summary: As all herbicides act on pathways or processes crucial to plants, in an inhibitory or stimulatory way, low doses of any herbicide might be used to beneficially modify plant growth, development, or composition. Glyphosate, the most used herbicide all over the world, is widely applied at low rates to ripen sugarcane. Low rates of glyphosate also can stimulate plant growth (this effect is called hormesis). When applied at recommended rates for weed control, glyphosate can inhibit rust diseases in glyphosate-resistant wheat and soybean. Fluridone blocks the carotenoid biosynthesis by inhibition of phytoene desaturase and is effective in reducing the production of abscisic acid in drought-stressed plants. Among the ALS inhibitors, sulfometuron-methyl is widely used to ripen sugarcane and Imidazolinones can be used to suppress turf species growth. The application of protoporphyrinogen oxidase inhibitors can raise plant defenses against pathogens. Glufosinate, a glutamine synthetase inhibitor, can also control plant diseases. Auxin agonists (like dicamba and 2,4-D) are effective, low cost plant growth regulators. Currently, auxin agonists are still used in tissue cultures to induce somatic embryogenesis and to control fruit ripening, to reduce drop of fruits to enlarge fruit size or to extend the harvest period in citrus orchards. At low doses, triazine herbcides stimulate growth through beneficial effects on nitrogen metabolism and through auxin-like effects. Thus, sublethal doses of several herbicides have uses or potential uses other than killing weeds.

Technical Abstract: As all herbicides act on pathways or processes crucial to plants, in an inhibitory or stimulatory way, low doses of any herbicide might be used to beneficially modify plant growth, development, or composition. Glyphosate, the most used herbicide all over the world, is widely applied at low rates to ripen sugarcane. Low rates of glyphosate also can stimulate plant growth (this effect is called hormesis). When applied at recommended rates for weed control, glyphosate can inhibit rust diseases in glyphosate-resistant wheat and soybean. Fluridone blocks the carotenoid biosynthesis by inhibition of phytoene desaturase and is effective in reducing the production of abscisic acid in drought-stressed plants. Among the ALS inhibitors, sulfometuron-methyl is widely used to ripen sugarcane and Imidazolinones can be used to suppress turf species growth. The application of protoporphyrinogen oxidase inhibitors can raise plant defenses against pathogens. Glufosinate, a glutamine synthetase inhibitor, can also control plant diseases. Auxin agonists (like dicamba and 2,4-D) are effective, low cost plant growth regulators. Currently, auxin agonists are still used in tissue cultures to induce somatic embryogenesis and to control fruit ripening, to reduce drop of fruits to enlarge fruit size or to extend the harvest period in citrus orchards. At low doses, triazine herbcides stimulate growth through beneficial effects on nitrogen metabolism and through auxin-like effects. Thus, sublethal doses of several herbicides have uses or potential uses other than killing weeds.