11,313
edits
Changes
Jump to navigation
Jump to search
SW: →How It Works: add info
:"Glyphosate inhibits plant growth by inhibiting the production of essential aromatic amino acids through competitive inhibition of the enzyme enolpyruvylshikimate phosphate (EPSP) synthase. This is a key enzyme in the shikimic acid pathway for the synthesis of chorismate..., which is a precursor for the essential amino acids phenylalanine, tyrosine, and tryptophan."<ref>John P. Giesy, Stuard Dobson, and Keith R. Solomon, 2000, "[http://www.colby.edu/biology/BI402B/Giesy%20et%20al%202000.pdf Ecotoxicological Risk Assessment for Roundup Herbicide]," Rev Environ Contam Toxicol 167:35-120.</ref>
In other words, glyphosate prevents plants from making amino acids they need to survive. It does this by inhibiting an enzyme needed to make chorismate, a precursor to those amino acids.One of these amino acids, tryptophan, "is necessary for the synthesis of indolylacetic acid (IAA), the main growth promoter, that can explain the widespread field observation of reduced in depth root growth of plants."<ref>Preface "Glyphosate interactions with physiology, nutrition, and diseases of plants: Threat to agricultural sustainability?", European Journal of Agronomy 31 (2009) 111-113.</ref>
A 1984 study found plants that died following treatment with glyphosate were infected with pathogenic fungi, compared to control plants not treated with glyphosate but planted in the same media that did not yield pathogenic fungi.<ref>Gurmukh S. Johal and James E. Rahe, "[http://www.nationalorganiccoalition.org/resources/Biblio/glyphosatepathogenkillRahe.pdf Effect of soilborne plant-pathogenic fungi on the herbicidal action of glyphosate on bean seedlings]," ''Phytopathology'' (1984), 74:950-955.</ref> The study concluded that more research was needed but postulated that glyphosate inhibits the plant's defense mechanisms and/or increases nutrient leakage from treated plants.
