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'''Glyphosate''', ''N''-phosphonomethyl glycine, is broad-spectrum herbicide, sold under the brand name [[Roundup]]. It is "the most widely used broad-spectrum herbicide on <nowiki>[a]</nowiki> global scale."<ref>Tsehaye Tesfamariam, S. Bott, I. Cakmak, V. Römheld, G. Neumann, "[http://stopogm.net/webfm_send/53 Glyphosate in the rhizosphere – role of waiting times and different glyphosate binding forms in soils for phytoxicity to non-target plants]," ''European Journal of Agronomy (2009), 31:126-132.</ref> Some [[genetically engineered crops]], sold as [[Roundup Ready Crops]] have their DNA altered to allow them to withstand glyphosate.Commercial formulations of glyphosate were first sold in 1974.<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>
== How It Works ==
Glyphosate is absorbed through a plant's foliage and then transported throughout the stems, leaves, and roots of the entire plant. A 2009 study says :<ref>Tsehaye Tesfamariam, S. Bott, I. Cakmak, V. Römheld, G. Neumann, "[http://stopogm.net/webfm_send/53 Glyphosate in inhibits plant growth by inhibiting the rhizosphere – role production of waiting times and different glyphosate binding forms in soils for phytoxicity to non-target plants]," ''European Journal of Agronomy (2009), 31:126-132.</ref>:"The herbicidal effect is based on essential aromatic amino acids through competitive inhibition of the shikimate pathway enzyme 5-enolpyruvylshikimic acid-3-enolpyruvylshikimate phosphate synthas (EPSPSEPSP), involved synthase. This is a key enzyme in the biosynthesis shikimic acid pathway for the synthesis of aromatic chorismate..., which is a precursor for the essential amino acids phenylalanine, tyrosine, and phenolic compoundstryptophan."<ref>Guy Della-Cioppa, SJohn P. Christopher BauerGiesy, Barbara K. KleinStuard Dobson, Dilip Mand Keith R. ShahSolomon, Robert T. Fraley, and Ganesh M. Kishore2000, "[http://www.ncbicolby.nlm.nih.govedu/pmcbiology/articlesBI402B/PMC386612/ Translocation of the precursor of 5-enolpyruvylshikimate-3-phosphate synthase into chloroplasts of higher plants ''in vitro''Giesy%20et%20al%202000.pdf Ecotoxicological Risk Assessment for Roundup Herbicide], Proc Natl Acad Sci U S A. 1986 September; 83(18)" Rev Environ Contam Toxicol 167: 6873–687735-120.</ref><ref>John E. Franz In other words, Michael Kglyphosate prevents plants from making amino acids they need to survive. MaoIt does this by inhibiting an enzyme needed to make chorismate, and James A. Sikorski, ''Glyphosate: A Unique Global Herbicide'', American Chemical Society, 1997, ppa precursor to those amino acids. 65-97.</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.
In other words, low doses of glyphosate equal to the amount plants are exposed to in spray drift, can result in iron deficiencies in the plants. For crops destined as animal feed or as human food, this could result in decreased dietary iron.
== Glyphosate in the Environment ==
Although glyphosate is highly soluble in water, its tendency to bond to soils makes it unlikely to leach into groundwater or runoff "significantly." (Studies have found about 1%-2% of glyphosate may runoff in rainfall after glyphosate is applied.<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>)
=== Glyphosate in the Soil ===
Glyphosate can reach the soil by washing off the foliage of plants, via spray drift, by exudation from the roots of treated plants, or by the decomposition of treated plants. However, "risks of glyphosate toxicity to non-target organisms in soils are generally considered as marginal,since glyphosate is almost instantaneously inactivated by adsorption to clay minerals and cationic binding sites of the soil matrix (Piccoloetal.,1992;Dong-Meietal.,2004), while glyphosate in the soil solution is prone to rapid microbial degradation (Giesy et al., 2000)."<ref>Tsehaye Tesfamariam, S. Bott, I. Cakmak, V. Römheld, G. Neumann, "[http://stopogm.net/webfm_send/53 Glyphosate in the rhizosphere – role of waiting times and different glyphosate binding forms in soils for phytoxicity to non-target plants]," ''European Journal of Agronomy (2009), 31:126-132.</ref><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 residues in the soil are not considered hazardous as it either breaks down quickly or binds to minerals that make it no longer a threat to plants. Glyphosate that biodegrades usually breaks down into carbon dioxide and ammonium (NH4+).<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 an analysis of 47 studies, 50% of glyphosate broke down in the soil in time periods ranging from 1.2 days to 197.3 days. The arithmetic mean amount of time was 32 days and the geometric mean was 17 days.<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>
=== Glyphosate in Water ===
Although most glyphosate applied to soil does not run off into waterways, sometimes glyphosate is applied to aquatic environments directly. In flowing water, it is dissipated via "tributary dilution, dispersion, and loss through processes such as absorption to suspended particulate matter or sediments and microbial degradation."<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> The half-life of glyphosate in water has been estimated to be from 7 to 14 days.<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>
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