Glyphosate sensitive plants

EPSPS has been isolated from both microorganisms and plants, and several of its properties have been studied. The bacterial and plant enzymes are mono functional with molecular mass of 44-48 kD (8-15). The fungal enzyme is a part of the multifunctional arom complex which catalyzes four other reactions of the shikimate pathway (16). While the bacterial enzymes show differences with respect to glyphosate sensitivity, the plant enzymes exhibit a much more narrow range of sensitivity (17). This accounts for the susceptibility of most plant species to glyphosate. 

Overproduction of EPSPS has been observed in several plant cell cultures tolerant to glyphosate (12, 13, 29). In the case of glyphosate-tolerant Corydalis cultures, Smart et al. demonstrated by 2 D-gel electrophoresis, the overproduction of other proteins besides EPSPS. Since the levels of activity of several shikimate pathway enzymes were unaltered in the tolerant cell line compared to the parent cell line, it was concluded that these amplified proteins may not be involved in aromatic amino acid biosynthesis. It is possible that the other proteins may not have a role in the tolerance mechanism. Alterations in protein profiles between glyphosate-sensitive and tolerant petunia cell lines have also been observed. With the glyphosate tolerant carrot cell line, in addition to overproduction of EPSPS, the levels of aromatic amino acids were found to be enhanced (29). Based on the results with plant cell cultures, it was therefore not clear if overproduction of EPSPS was sufficient to obtain glyphosate tolerance in plants. 

The increased tolerance of bean seedlings growing in heat treated soils is immense they are typically 10- to 100-fold less sensitive to glyphosate in heat treated soil compared with raw soil. The tolerance of the other plant... 

What causes the reduced sensitivity to glyphosate observed in plants growing in heat treated soils Both autoclave and microwave treatments were effective in creating reduced sensitivity. Both types of heat treatment markedly reduced populations of resident Pythium and Fusarium spp. This effect persisted for at least 2 weeks following seeding of wheat Triticum aestivum) and beans into the treated soils at the time when the soils were first exposed to recontamination (Table II). 

Glyphosate is soluble in water but not in waxes and lipids. The uptake and therefore the sensitivity of plants with waxy cuticles are thus low. Furthermore, glyphosate is inactivated in soil by forming insoluble salts with soil minerals, and this property can be exploited in selective usage. When used during the summer months, white anomones and some other dormant spring flowers are not harmed and will flourish the next year. 

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. " ... 

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