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https://en.wikipedia.org/wiki/Glufosinate

DL-Phosphinothricin is an herbicidal ammonium salt (a derivative of glufosinate) with the chemical formula C5H15N2O4P. It is a potent inhibitor to the enzyme glutamine synthetase, which is central to nitrogen regulation in various plant cell types, thus making it a highly effective compound in many nonselective systemic herbicides. . DL-Phosphinothricin inhibits glutamine synthetase, an enzyme necessary for the production of glutamine and for ammonia detoxification. DL-Phosphinothricin use in plants leads to reduced glutamine levels and elevated ammonia levels in tissues, halting photosynthesis, resulting in plant death. (http://www.pan-uk.org/pestnews/Actives/glufosin.htm)

History
DL-phosphinothricin is typically used in three different situations as an herbicide:
 * directed sprays for weed control
 * use as a crop desiccant to facilitate the harvest
 * use in genetically modified DL-phosphinothricin-resistant crops

Most DL-phosphinothricin use within the United States is with genetically modified crops in industrial farming.

History and Use of Phosphinothricin-Resistant Crops
Glufosinate-resistance was first commercialized in canola in 1995 and has since been commercialized in other crops such as corn, cotton and soybeans. Utilizing the BAR gene from Streptomyces hygroscopicus or the PAT gene from Streptomyces viridochromeogenes, crops are transformed to resist the herbicidal properties of the chemical. The two genes encode highly homogenous L-phosphinothricin acetyltransferases that catalyze N-acetylation of glufosinate. .

Sales of the glufosinate-resistant corn started in 1997. Commercial corn lines use both bar and pat genes in the transformation process.

Properties and Chemistry
DL-Phosphinothricin has a molecular formula of C5H15N2O4P. Its broad-spectrum herbicidal properties control important weeds such as morning glories, hemp sesbania (Sesbania bispinosa), Pennsylvania smartweed (Polygonum pensylvanicum) and yellow nutsedge better than a formerly used, narrow-spectrum herbicide, glyphosate. DL-Phosphinothricin is a contact herbicide, and is applied to young plants during early development for full effectiveness. .

Biochemistry
Dl phosphinothricin is a component of the tripeptide bialophos from Streptomyces viridochromeogenes. Bialopophos is is hydrolyzed to L-phosphinothricin which directly acts as the irreversible inhibitor of glutamine synthetase. The build up of ammonia after application is measurable after 1h of treatment. .