Technical


Glyphosate is a topical subject, so we thought we’d take a look at how it works, what a ‘Bio’ formulation actually means and what we, as an industry, can do to ensure that glyphosate is available for use for the foreseeable future.


Pitchcare’s Technical Manager, John Handley, provides a detailed explanation


How it works - the science


Glyphosate is a non-selective, chemical herbicide that kills plants by inhibiting the shikimate pathway. A pathway in the field of biochemistry is a sequence of reactions, usually controlled and catalysed by enzymes, by which one organic substance is converted to another. Glyphosate is a competitive inhibitor of a plant enzyme - EPSP synthase. EPSP synthase participates in


biosynthesis of the aromatic amino acids phenylalanine, tyrosine and tryptophan. These amino acids are only synthesised in plants and microorganisms. Animals obtain aromatic amino acids by ingesting plants and other organisms, therefore this pathway is a very appropriate target when seeking to


focus on controlling species within the plant kingdom and, thereby, creating a formula that has a good


toxicological profile. Glyphosate binds more tightly to EPSP


Glyphosate formulation and function


130 I PC JUNE/JULY 2014


synthase than its natural substrate and inhibits the production of the enzyme and, consequently, shuts down the entire pathway. Plants require the shikimate pathway to produce aromatic amino acids which, in turn, are used to make proteins. By shutting down this pathway, this effectively kills the plant, though the plant must utilise its available store of these amino acids, which is why we see a difference in the time that it takes to kill some plants, though the effect is inevitably the same. Shikimic acid was first isolated from the plant star anise (Illicium religiosum) in 1885. The name is derived from the Japanese name for this plant, shikimi-no-ki.


Formulation


So, what makes one glyphosate different to another glyphosate, and which one should we choose? Glyphosate, in its raw state, is a waxy


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