Glyphosate physiological effects

Little information has been published on pesticide degradation products, produced in coffee, that may have significant physiological effects. Some information has been published, however, for glyphosate,191 aldicarb,194 and carbofuran,187 although there is some controversy surrounding the carbofuran data.188... 

In considering the commercially successful herbicides known to be inhibitors of amino acid biosynthesis, three aspects will be considered the kinetic description of the inhibition, the molecular interactions involved, and the relevance of the proposed target site to the observed physiological effects. Because of the extensive body of research published on the shikimate pathway and the herbicide glyphosate, this example will be taken as a paradigm of the inhibitor-enzyme relationship. The other cases considered will be the branched-chain amino acid family, histidine biosynthesis, and glutamine synthetase. 

Glyphosate is phloem mobile and accumulates in accordance with source-sink relationships in meristematic areas of the treated plants. " The general physiological effects of glyphosate are consistent with its acting as a metabolic poison. Death is a slow process, requiring days or weeks much more rapid effects, within hours, can be demonstrated at the biochemical level. These effects can be explained if the turnover rates of specific proteins, and therefore sensitivity to amino acid synthesis inhibition, differ. Inhibition of phenolic biosynthesis and chlorophyll formation and effects on the levels of the phytohormone 3-indoleacetic acid have been considered as target sites but can be viewed as necessary consequences of the primary interference with aromatic amino acid biosynthesis. " ... 

Figure 3. Effect of glyphosate on fresh weight (o), chlorophyll content (x), and anthocyanin content ( ) of excised buckwheat cotyledons after 24 h of treatment in the light. Reproduced with permission from Ref. 6. Copyright 1980, Plant Physiology.

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