How glyphosate works
Plants absorb glyphosate through their leaves and other green parts. From here, the glyphosate moves to the growing points of shoots and roots, where it interferes with the enzymatic production of certain amino acids that are essential for plant growth. This pathway exists only in plants, fungi and bacteria, so the toxicity to animals is low.
Compared to other active ingredients in herbicides, glyphosate is a small molecule with a molecular weight of 169 g. Glyphosate is a derivative of the amino acid glycine, where one of the amino hydrogen atoms has been replaced with a phosphonomethyl group. (Phosphorus atoms in orange, hydrogen atoms in white, oxygen atoms in red, nitrogen atom in blue).
In addition to glyphosate’s low toxicity (observed in many studies), a number of other qualities have made it popular as a herbicide: It is effective against a broad range of weeds and, despite not being selective, it removes the whole of a treated plant – the roots as well as the above-ground parts.
On its own, glyphosate is not water soluble enough to be readily sprayed and taken up by the plant. This is why glyphosate is commonly applied in salt form. In addition, herbicides contain other chemical substances, such as surfactants, to improve their solubility and enhance penetration of glyphosate, the active ingredient, into plants. Surfactants, which are also commonly used in washing powders, washing-up liquids and shampoos, make the waxy surfaces of plants more penetrable and the herbicide stickier, so it is not washed off by rain immediately after spraying.
Last update: 19 June 2013