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Glyphosate (N-(phosphonomethyl)glycine) is the phytotoxic reagent in the widely used Roundup® herbicide. Its mode of action in plants is the disruption of the Shikimate pathway, part of an important route to the biosynthesis of essential aromatic amino acids. It is well documented that glyphosate can be degraded by soil microorganisms after contact of the herbicide solution with the soil. It is also accepted that glyphosate, an excellent ligand, is readily absorbed to metal ions, such as Fe(III), that can be abundant in soils. There have been many accounts on the microbial degradation of glyphosate, and several metal-glyphosate complexes have been synthesised and characterised. Surprisingly, given the degree of adsorption to metal ions in the soil, there have not, to date, been any reports in the literature on the reactivity of metal-glyphosate complexes. The behaviour of these types of complexes under various reaction conditions may give us an insight into the mechanisms present when glyphosate degrades. In order to explore the behaviour of metal-glyphosate adducts, we have prepared several new cobalt-PMG complexes in the lab. These complexes have been characterised by NMR, mass spectrometry, elemental analysis, and in some cases X-ray crystal structure determination. We chose to synthesise complexes where the PMG ligand is bidentate or tridentate, filling the remaining four or three (respectively) coordination sites with an ancillary, nitrogen-containing ligand. We have subjected the complexes to photolytic and basic conditions, as we are interested in ascertaining how coordinated PMG might behave when irradiated with UV light, and when it is C-deprotonated. Metal-glyphosate complexes in nature may be exposed to UV light, so we are concerned with how the coordinated ligand might react under these circumstances. We have found that the prepared cobalt-PMG complexes are reactive when exposed to UV light, and that this appears to result in the degradation of the complex, and in some cases, the PMG ligand itself. The reactivity of C-deprotonated PMG is also an area of interest to us. It is possible that elevations in soil pH can lead to C-deprotonation of glyphosate, then further reactivity that may contribute to the degradation of the compound. Furthermore, when the herbicide is held in the active site of an enzyme within a microbe, it may become deprotonated, and this may aid in its microbial degradation. We have found that, under basic conditions, the reactivity of the prepared PMG complexes depends on the ancillary ligand attached - π-acidic, pyridine-containing ancillary ligands appear to increase the reactivity of coordinated PMG. It seems that amine-containing ligands hinder the reactivity of the coordinated PMG such that the complex remains intact. It is hoped that the results of the research described in this thesis will assist in the future investigations into the reactivity of the herbicide glyphosate.

Glyphosate (N-(phosphonomethyl)glycine) is the phytotoxic reagent in the widely used Roundup® herbicide. Its mode of action in plants is the disruption of the Shikimate pathway, part of an important route to the biosynthesis of essential aromatic amino acids. It is well documented that glyphosate can be degraded by soil microorganisms after contact of the herbicide solution with the soil. It is also accepted that glyphosate, an excellent ligand, is readily absorbed to metal ions, such as Fe(III), that can be abundant in soils. There have been many accounts on the microbial degradation of glyphosate, and several metal-glyphosate complexes have been synthesised and characterised. Surprisingly, given the degree of adsorption to metal ions in the soil, there have not, to date, been any reports in the literature on the reactivity of metal-glyphosate complexes. The behaviour of these types of complexes under various reaction conditions may give us an insight into the mechanisms present when glyphosate degrades. In order to explore the behaviour of metal-glyphosate adducts, we have prepared several new cobalt-PMG complexes in the lab. These complexes have been characterised by NMR, mass spectrometry, elemental analysis, and in some cases X-ray crystal structure determination. We chose to synthesise complexes where the PMG ligand is bidentate or tridentate, filling the remaining four or three (respectively) coordination sites with an ancillary, nitrogen-containing ligand. We have subjected the complexes to photolytic and basic conditions, as we are interested in ascertaining how coordinated PMG might behave when irradiated with UV light, and when it is C-deprotonated. Metal-glyphosate complexes in nature may be exposed to UV light, so we are concerned with how the coordinated ligand might react under these circumstances. We have found that the prepared cobalt-PMG complexes are reactive when exposed to UV light, and that this appears to result in the degradation of the complex, and in some cases, the PMG ligand itself. The reactivity of C-deprotonated PMG is also an area of interest to us. It is possible that elevations in soil pH can lead to C-deprotonation of glyphosate, then further reactivity that may contribute to the degradation of the compound. Furthermore, when the herbicide is held in the active site of an enzyme within a microbe, it may become deprotonated, and this may aid in its microbial degradation. We have found that, under basic conditions, the reactivity of the prepared PMG complexes depends on the ancillary ligand attached - π-acidic, pyridine-containing ancillary ligands appear to increase the reactivity of coordinated PMG. It seems that amine-containing ligands hinder the reactivity of the coordinated PMG such that the complex remains intact. It is hoped that the results of the research described in this thesis will assist in the future investigations into the reactivity of the herbicide glyphosate.

Thesis (M. Sc.)--University of Canterbury, 2005. / Typescript (photocopy). On t.p. "n+" is superscript. "April 2005." Includes bibliographical references (leaves 135-137). Also available via the World Wide Web.

Pre-harvest glyphosate is applied to cereal grains to remove weeds. However, it has been claimed that oat compositions are affected by pre-harvest glyphosate. Research was conducted to evaluate differences in properties of β-glucan in the treated versus untreated oat groats. Two oat cultivars (Rockford and Souris) were grown at Minot and Prosper, North Dakota in 2015, and glyphosate was sprayed during the soft dough stage, physiological maturity stage, or not applied. β-Glucan viscosity was not significantly (p > 0:05) affected by treatment at soft dough or physiological maturity stages. Use of glyphosate at the soft dough stage significantly (p < 0:05) reduced the percentages of β-glucan content and solubility versus untreated samples. Treatment at soft dough and physiological maturity stages significantly (p < 0:05) increased β-glucan molecular weights compared to untreated controls. Therefore, glyphosate can be applied at the physiologically mature stage of grain development because β glucan properties from the groats were not negatively affected.

Glyphosate-resistant (GR) Italian ryegrass has been documented in many different countries around the world and has now become a major problem in row crop production areas of Mississippi. Field experiments were conducted from 2006 to 2008 in the Mississippi Delta to evaluate various herbicide and tillage treatment programs for its control. style='mso-spacerun:yes'> Highest level of control and reduction of GR Italian ryegrass biomass was observed with mechanically incorporated as well as surface applied residual herbicides in the fall of the year. style='mso-spacerun:yes'> Control of GR Italian ryegrass was 86-95% with surface applications of clomazone at 0.56, 0.84, and 1.12 kg ai/ha, s-metolachlor at 1.79 kg class=SpellE>ai/ha and KIH-485 at 0.16 kg ai/ha 171 days after emergence. Using a systems approach, preplant incorporated (PPI) class=SpellE>clomazone and/or s- class=SpellE>metolachlor followed by preemergence (PRE) application of paraquat + linuron+ non-ionic surfactant was also found to control and reduce biomass of GR Italian ryegrass.

Due to reduced reproductive tolerance, current Roundup Ready cotton only allows for over-the-top glyphosate applications through the fourth leaf stage of development. To combat this issue, Roundup Ready Flex cotton was introduced in 2006, offering both vegetative and reproductive tissue tolerance to glyphosate. Roundup Ready Flex cotton offers a wider window of application timing, without risk of plant injury. The primary objectives of this research were to test Roundup Ready Flex cotton against current Roundup Ready cotton technology at various application rates and timings and to test various elite varieties of Roundup Ready Flex cotton for glyphosate tolerance. Roundup Ready Flex cotton tolerance was unaffected by application rates or timings. Roundup Ready Flex cotton varieties were unaffected by glyphosate applications. Roundup Ready Flex cotton exhibits both vegetative and reproductive tolerance to glyphosate and is an effective alternative to current Roundup Ready cotton cropping systems.

Thèse de doctorat : Sciences agronomiques : INPL : 2007. / Titre provenant de l'écran-titre. Bibliogr.

Field experiments were conducted at Carman, Manitoba to determine the effect of tank-mixing different contact herbicides with glyphosate and time of application of harvest aid herbicides on residue accumulation in dry bean seed and the effect of tank-mixing a contact herbicide with glyphosate on weed control. Carfentrazone-ethyl in mixture with glyphosate was the least effective harvest aid herbicide and did not fully desiccate plant parts or reduce glyphosate residues in the seed to less than 2 ppm. Saflufenacil, diquat, flumioxazin, and glufosinate in mixture with glyphosate effectively desiccated all plant and reduced glyphosate residue accumulation in the seed. Saflufenacil in mixture with glyphosate provided the most consistent efficacy on three weed species. Time of application of harvest aid herbicides influenced residue accumulation and yield; however, all harvest aids applied at or after 75% pod colour change had no negative effect on yield and significantly reduced the risk of residue accumulation.

Thesis (M.S.) in Ecology and Environmental Science--University of Maine, 2007. / Includes vita. Includes bibliographical references (leaves 55-59).