Browsing by Author "Foy, Chester L."

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    Absorption, translocation, and fate of the herbicide, 2-(3,4- dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-dione, in cotton
    Jones, Donald W. (Virginia Tech, 1971-08-05)
    Absorption, translocation, and metabolism of the ¹⁴C-labeled herbicide 2-(3,4-dichlorophenyl)-4-methyl-I,2,4-oxadiazolidine-3,5-dione (VCS-438) in cotton (Gossypium hirsutum L. 'Acala 4-42-77') were studied using autoradiography, thin-layer chromatography, and counting. Foliar penetration and acropetal distribution of 14C occurred within 3 hr and increased with time. No basipetal translocation of ¹⁴C out of treated leaves was detected after treatment. Radioactivity first occurred in the leaf veins, then more generally in interveinal tissues distally from the point of application. Absorption into roots of 30-day-old plants via nutrient solution was rapid; translocation into stem and leaves occurred 12 to 24 hr after treatment. Radioactivity was translocated more rapidly in 40-day-old plants. ¹⁴C in leaves of root-treated plants was first located in the veins, then distributed throughout with accumulation of ¹⁴C in lysigenous glands and leaf margins. Little ¹⁴C moved into young growing points; most accumulated in older leaves. Heterocyclic ring-labeled and phenyl ring-labeled VCS-438- ¹⁴C had similar distribution patterns of ¹⁴C, characteristic of compounds
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    Characterization of Organosilicone Surfactants and Their Effects on Sulfonylurea Herbicide Activity
    Sun, Jinxia (Virginia Tech, 1996-04-05)
    This research focused on the characterization of organosilicone surfactants and their effects on sulfonylurea herbicide activity. The project included efficacy tests, rainfastness studies in the greenhouse, radiotracer studies on herbicide uptake, fluorescent dye studies on surface deposition, and various measurements of physico-chemical properties. In measuring physico-chemical properties, a logistic dose response relationship was found between adjuvant concentration and contact angle on parafilm. An AsymSigR relationship existed between adjuvant concentration and surface tension for all the adjuvants. The organosilicones, Silwet L-77, Silwet 408, and Sylgard 309, and Kinetic (a blend of an organosilicone with a nonionic surfactant) gave equilibrium surface tension values around 20 dyne/cm and showed great spreading ability on the foliage of velvetleaf. With the conventional adjuvants, Agri-Dex, methylated soybean oil, Rigo oil concentration, and X-77, and Dyne-Amic (a blend of an organosilicone with a crop oil concentrate), surface tension was rarely below 28 dyne/cm and spreading ability was limited on velvetleaf. In addition, the organosilicone surfactant and Kinetic also lowered dynamic surface tension, which may improve droplet retention on leaf surfaces. The differences in physico-chemical properties between Kinetic and Dyne-Amic confirmed that carefully electing a co-adjuvant for an organosilicone blend is critical to avoid antagonism with trisiloxane molecules and retain the unique physico-chemical properties of organosilicone in the blends. Studies involving structurally-related organosilicones showed that the end structure in the trisiloxane hydrophilic group has little or no effect on surface tension, contact angle, spread pattern, herbicide uptake and translocation, and efficacy of primisulfuron on velvetleaf. It may be suggested that there is not a strict requirement to purify the end structure during the synthesis process, which is time consuming and expensive. When 14C-primisulfuron was combined with organosilicones or the blends, the uptake of 14C at 1 or 2 h after herbicide application was significantly higher than when combined with conventional adjuvants in velvetleaf. In the greenhouse, organosilicone surfactants greatly increased the rainfastness of primisulfuron in velvetleaf. The effect was immediate and dramatic, even when simulated rainfall was applied 0.25 h after treatment. In addition, herbicide efficacy on marginally susceptible weed species, velvetleaf and barnyardgrass, was significantly increased. A very complicated relationship exists between herbicides and adjuvants. The enhancement effects of adjuvants are often herbicide specific, weed species specific, and even environment specific. No one type of adjuvant functions well in all circumstances. Therefore, there is a need to understand the properties and functions of each class of adjuvants and locate the 'right' niche for each individual adjuvant.
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    Characterization of the Mechanism of Resistance of a Johnsongrass (Sorghum halepense) Biotype to Selected Graminicides in Virginia and Response of Mugwort (Artemisia vulgaris) to Specific Herbicidal and Cultural Control Strategies
    Bradley, Kevin Wayne (Virginia Tech, 2000-04-26)
    Johnsongrass [Sorghum halepense (L.) Pers.] and mugwort (Artemisia vulgaris L.) are both rhizomatous perennial weeds that are capable of rapidly colonizing a variety of different environments. Separate experiments were conducted throughout Virginia from 1996 to 1999 to determine more effective methods for reducing infestations of these perennial weeds in the future. Field and greenhouse experiments conducted on a resistant johnsongrass population discovered in New Kent County, Virginia revealed that this biotype exhibits low levels of resistance to the aryloxyphenoxypropionate (APP) herbicides quizalofop-P and fluazifop-P and the cyclohexanedione (CHD) herbicide sethoxydim. Additional laboratory experiments revealed that resistance is not due to differential absorption, translocation, or metabolism of the APP and CHD herbicides in the resistant vs. the susceptible biotype. However, acetyl-coenzyme A carboxylase (ACCase) assays revealed that resistance to the APP and CHD herbicides is conferred by an overproduction of the ACCase enzyme in the resistant compared to the susceptible johnsongrass biotype. In field experiments conducted on mugwort infestations discovered in several counties throughout Virginia, 100% mugwort control was achieved with standard application rates of picloram at 4 months after treatment (MAT), and also greater than 70% mugwort control was achieved with the higher application rates of clopyralid, glyphosate, and dicamba at 4 MAT. However, all other herbicides evaluated in these experiments provided less than 65% mugwort control at 4 MAT, even at exceptionally high use rates. Additionally, the results from these trials revealed that sequential herbicide applications and sequential mowings prior to herbicide application are both effective mugwort control strategies.
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    Comparative studies on the modes of action of SC-0224 and glyphosate
    Cooley, William Edward (Virginia Polytechnic Institute and State University, 1985)
    The biological actions of the herbicides SC-0224 (trimethylsulfonium carboxymethylaminomethylphosphonate) and glyphosate [N-(phosphonomethyl)glycine] (PMG) were compared. In each study trimethylsulfonium iodide (TMS-I) was included as a treatment because the trimethylsulfonium ion is a constituent of the SC-0224 molecular structure. In inflated duckweed (Lemna gibba L.), both formulated and technical grade forms of SC-0224 were found to be much more phytotoxic to duckweed than either formulated or technical grade forms of glyphosate. The growth inhibition caused by glyphosate was partially prevented by different combinations of the aromatic amino acids phenylalanine, tyrosine, and tryptophan; whereas, the duckweed growth inhibition caused by SC-0224 could not be reduced by the same amino acid combinations. TMS-I and SC-0224 were found to be equally phytotoxic to duckweed. SC-0224 caused larger increases than glyphosate in the pool levels of amino acids; the increases caused by SC-0224 were similar, however, to those caused by trimethylsulfonium iodide. Expressed on a per gram fresh weight basis none of the chemical treatments caused significant changes in soluble protein or the incorporation of ¹⁴C-leucine into soluble protein. On a per flask basis (allowing for decreased growth in treated flasks), both herbicides and TMS-I caused significant decreases in soluble protein and ¹⁴C-leucine incorporation. SC-0224 and TMS-I caused larger decreases than glyphosate in both cases but the SC-0224 and TMS-I treatments were not significantly different. These data indicate that differences in the phytotoxicity of SC-0224 .and glyphosate may be due to the action of the trimethylsulfonium ion of the SC-0224 structure. The effects of these herbicides on the conversion of shikimate to anthranilate in a cell-free extract of Klebsiella pneumoniae ATCC 25306 were also compared. SC-0224 and glyphosate equally inhibited the production of anthranilate indicating that SC-0224 has action similar to glyphosate on the shikimate pathway. The effects of these herbicides on photosynthetic electron transport (the Hill reaction) was determined using isolated thylakoids from Alaska pea (Pisum sativum L.). The action of SC-0224 was compared with the action of glyphosate, TMS-I and diuron [3-(3,4-dichorophenyl)-1,1-dimethylurea]. SC-0224, glyphosate and TMS-I did not inhibit the Hill reaction at concentrations up to 10 mM; whereas, diuron caused an almost total inhibition at 0.10 mM. The results of this study indicate that SC-0224 is not an inhibitor of photosynthetic electron transport. These studies indicate that both constituents of the SC-0224 structure, TMS and PMG, are phytotoxic and may act independently.
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    Egyptian Broomrape (Orobanche aegyptiaca Pers.) and Small Broomrape (Orobanche minor Sm.) Parasitism of Red Clover (Trifolium pratense L.) in Vitro
    Morozov, Ivan Vladimirovitch (Virginia Tech, 1998-05-13)
    Broomrapes, Orobanche spp., are holoparasites that affect the growth of a variety of broadleaf crops. One of the distinct characteristics of the family Orobanchaceae is the lack of chlorophyll, and hence inability to synthesize their own food. Broomrapes subsist on the roots of the host plant from which they derive the carbon, water, and nutrients needed for further growth. Parasitism as such leads to yield reductions, and in case of heavy infestations, complete crop failure. Among other plants parasitized by broomrapes are several legumes, some of which are also the world's most economically important crops. As part of their unique biology, legumes provide an ecological niche for diazotropic soil bacteria, which belong to the family Rhizobiaceae. In return, the host plant receives fixed nitrogen from the nodules, specialized structures produced on the roots of most legume plants upon inoculation with bacteria. Orobanche spp. germination depends on the presence of chemical stimulant in host root exudates. It has been reported that inoculation of some legumes resulted in greater infestation by parasitic weeds. In addition, bacterial nodules were assumed to provide a place for broomrape invasion of host legume. Furthermore, infestations were observed to be more intense in aerobic conditions when rhizobia are most active. It is possible that production of the stimulant could be correlated with the infection of roots with Rhizobium, and that the nodules formed on the roots could play a role in broomrape parasitism; however, others have not confirmed this. Studies were conducted to investigate the possibility of interaction between Orobanche spp. attack and Rhizobium nodulation in legumes. Seed germination, number of parasitic attachments, as well as the morphology of two broomrape species, small broomrape (Orobanche minor Sm.) and Egyptian broomrape (Orobanche aegyptiaca Pers.), were studied. O. minor showed a greater percent seed germination, and formed a greater number of attachments on red clover (Trifolium pratense L.) inoculated with Rhizobium leguminosarum bv. trifolii in comparison with non-inoculated plants. However, the addition of the inoculum did not appear to enhance O. aegyptiaca seed germination or the number of its attachments on the host roots compared with the controls. Morphological observations of O. minor attachments on red clover suggest that parasitic attachments were not situated over the bacterial nodules, but perhaps involve parasite-induced enzymatic degradation followed by mechanical protrusion of host plant root cortex, possibly utilizing host plant-rhizobacteria interactions as well.
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    Field efficacy and availability, movement, and persistence of ICIA-0051 herbicide in soils
    Wilson, John Samuel (Virginia Polytechnic Institute and State University, 1989)
    Fields studies conducted in 1987 and 1988 determined the weed control efficacy of ICIA-0051 and SC-0774 in conventional and no-till systems of corn (Zea mays L.) culture. Results of the preemergence and postemergence applications of ICIA-0051, across all treatments after 8 weeks, showed 85% control or better of triazine-resistant smooth pigweed (Amaranthus hybridus L.), while fall panicum (Panicum dichotomiflorum Michx.) control ranged from 43 to 87%. Giant ragweed (Ambrosia trifida L.) control ranged from 30 to 95%, while control of ivyleaf morningglory (Ipomoea hederacea (L.) Jacq.) was below 75% in the preemergence treatments and ranged from 89 to 99% in the postemergence treatments. In general, the addition of atrazine to the pre- and postemergence treatments of ICIA-0051 improved weed control. SC-0774 treatments gave 85% or better control of fall panicum, but inadequate broadleaf weed control (75% or worse). Soil mobility studies using soil thin-layer chromatography and soil leaching columns indicated that the movement of ICIA-0051 was highly negatively correlated with the organic/humic matter fraction. Although the mobility patterns were similar, ICIA-0051 was more mobile than SC-0774, which was more mobile than atrazine. A comparison of ICIA-0051 across soils indicated that the order of mobility was Appling loamy sand (Rf = 6.4) > Davidson clay (Rf = 5.6) > Bojac sandy loam (Rf = 5.0) = Frederick silt loam (Rf = 4.9) > Hyde silty clay loam (Rf = 1.1). Other soil properties such as the clay content and pH were not strongly correlated with ICIA-0051 movement. Results of the adsorption/desorption studies indicated that the organic/humic matter fraction was primarily responsible for the binding and retention of ICIA-0051 across the five soils investigated. Based on the K constants derived from the Freundlich equation, the order of adsorption was Hyde > Frederick > Davidson = Bojac > Appling. The desorption results indicated that ICIA-005l was not tightly bound to the soil particles, with losses between 20 and 50% of the amount adsorbed after two desorptions. Results of the greenhouse persistence study, using mustard (Brassica kaber L.) as a bioassay species, indicated that ICIA-0051 was more biologically available than atrazine. Similar to the adsorption and leaching results, the persistence of ICIA-0051 was highly positively correlated with the soils’ organic matter. Regardless of the rate used, crop injury decreased over time, although the highest rate (1 ppm of ICIA-0051) showed significant crop injury even after 6 months in several soils in the greenhouse studies.
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    Influence of grazing sheep and cattle together and separately on soils, plants and animals
    Abaye, Azenegashe Ozzie (Virginia Tech, 1992-02-25)
    Angus cows (Bos taurus) with calves and 1/2 Dorset, 1/4 Finn and 1/4 Rambouillet ewes (Ovis aries) with lambs grazed Kentucky bluegrass (Poa pratensis) - white clover (Trifolium repens) in a randomized block design with three replications during 3 yr, to investigate effects of grazing cattle and sheep together and separately on soils, plants and animals. Additionally, changes in stocking rate, seasonal distribution of cool-season forages and varying nutritional requirements of animals were examined. There were 6 cow-calf pairs or 6 ewes with 11 lambs per replication of cattle alone and sheep alone treatments. Six cows plus six ewes, with their offspring, were allotted to each replication of mixed grazed pastures. Initial stocking rates were equilibrated among treatments to 1 cow and calf per .45 ha. Grazing sheep alone increased (P < .05) percentage bluegrass (58%) but decreased white clover (6%) and weeds (36%), compared to pastures grazed only by cattle (30, 16 and 53%, respectively, which was similar to initial composition). Soils in mixed grazed pastures remained higher (P < .05) in plant nutrients, pH, and percent organic matter and were less (P < .05) compacted, compared to soils where sheep or cattle grazed alone. Total forage mass and quality were higher (P < .05) in mixed grazed pastures, compared to pastures grazed by cattle and sheep alone. Daily gain (.23 kg/d), total gain (23 kg), and weaning weights (43 kg) of lambs were higher (P < .01) in pastures grazed by both animal species, compared to sheep alone (.18 kg/d, 19 and 38 kg, respectively). These animals also reached target weaning weights (43 kg) 14 d earlier (P < .05) than those grazed alone. Body condition of ewes was improved by the breeding season, compared to ewes grazed alone. Five measuring techniques were investigated to determine forage mass and botanical composition. Measurements based on small plots permanently located within pastures were as accurate as those based on the entire pasture. Visual estimations of forage mass were lower, compared to hand clipping, but reflected canopy height. Visual evaluations more accurately estimated presence of individual plant species than hand separated samples. Grazing ewes and cows with associated spring-born offspring on bluegrass-white clover improved the balance between plant growth and animal forage requirements and improved sustainability of the soil-plant-animal system.
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    Influence of osmotic stress, ethanol, and a substituted pyridazinone, BAS 13-338, on the growth and lipid composition of two Chlorella species
    Goedhart, Christian Leonard (Virginia Polytechnic Institute and State University, 1987)
    Chlorella vulgaris and Chlorella pyrenoidosa were compared relative to their abilities to grow at osmotic potentials of -0.1, -0.5, -1.0, -1.5, -2.0 MPa, [polyethylene glycol(PEG)-induced], and for osmotically-induced changes in lipid composition. C. vulgaris growth was inhibited as osmotic potentials decreased, while C. pyrenoidosa growth was moderately inhibited at -2.0 hPa. C. vulgaris produced increasing concentrations of triglycerides and sterol esters and decreasing levels of polar lipids and sterols as osmotic concentrations increased. Polar lipids, triglycerides, and sterols declined in C. pyrenoidosa while steryl esters remained constant. Ratios of free sterols to polar lipids were 10-fold greater in C. pyrenoidosa and were unaffected by reduced osmotic potentials. In C. vulgaris the sterol to polar lipid ratio declined. Decreasing osmotic potentials in a continuous culture of C. vulgaris, lowered cell lipid concentration, and had no effect on chlorophyll concentrations. The greatest decrease occurred as the osmotic potential decreased from -0.1 to -0.5 HPa. Decreasing osmotic potential caused the phospholipid concentrations to decline. Saturation of triglycerides and free fatty acids increased and decreased, respectively, while polar lipids remained fairly constant. However, the sterol to phospholipid ratio increased as the osmotic potential was lowered. BAS 13-338 (4-chloro-5-(dimethylamino)-2-phenyl-5- 3(2H)pyridazinone) had no effect on C. vulgaris resistance to osmotic stress, but caused growth inhibition as concentrations increased. However, BAS 13-338 was effective in decreasing growth inhibition of C. vulgaris grown in inhibitory levels of ethanol. BAS 13-338 had differing effects on the lipid composition of C. vulgaris when grown in PEG at an osmotic potential of -1.5 MPa compared to -0.1 MPa with 0.33% ethanol. The greatest effects were observed in the ethanol treatments where the qualitative composition of precursor sterols increased as the level of BAS 13-338 increased. This investigation confirmed the important role of lipids in responding to environmental stress through observations of lipid responses to osmotic stress and by manipulation of lipid concentrations using BAS 13-338. Resistance to ethanol inhibition but not osmotic inhibition was achieved in the investigation.
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    Mechanisms of action and selectivity of the cyclohexen-one herbicide cycloxydim (BAS 517)
    Li, Hwei-Yiing (Virginia Tech, 1990-09-27)
    The activity and the selectivity of cycloxydim {2-[1-(ethoxyimino)butylJ-3-hydroxy- 5-(2H-tetrahydrothiopyran-3-yl)-2-cyclohexen-l-one}, code designation BAS 517, were examined flIst with etiolated seedlings of com (Zea mays L.) and soybean [Glycine max (L.) Merr.]. Etiolated soybean seedlings were not affected by cycloxydim. The degree of growth inhibition of com varied with concentration of cycloxydim and incubation time. Compared to mesocotyls and coleoptiles, radicles of corn were the most sensitive to cycloxydim. Meristematic tissues appeared to be the site of action of cycloxydim as root meristems were the first to show symptoms. A band of reddening tissue developed at meristematic tips followed by the complete cessation of root growth. In a study comparing activities of technical grade and formulated cycloxydim and sethoxydim, {2-[ l-(ethoxyimino )butyl}- 5-[2-(ethylthio )propy11-3-hydroxy-2-cyclohexen-l-one}, formulated compounds were more potent than the technical grade chemicals without formulation additives. Technical sethoxydim was more potent than technical cycloxydim. Root tips excised from com and soybean seedlings were used subsequently for cycloxydim treatments. The activity and selectivity of cycloxydim expressed at the isolated root tip level were similar to those of cycloxydim bioassayed with whole seedlings. However, root tips appeared to be more sensitive than the whole seedlings. Injury at the tissue and cell levels of the 2-mm root tips that were treated with various concentrations of cycloxydim was examined after 24 hours incubation. Concentrations of 0.1, 1, and 10 μM cycloxydim caused severe cell vacuolization. A gradient of decreasing injury from epidermal cells toward the center of roots was observed. This pattern of injury appeared to reflect the penetration of cycloxydim into roots along a concentration gradient.
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    A neutron activation analysis investigation of traceable elements from automobile exhaust in roadside soil and vegetation
    Oakes, Thomas Wyatt (Virginia Tech, 1975-08-03)
    The purpose of this work was to demonstrate the effectiveness of neutron activation analysis in studying a complex environmental problem. The area chosen for study was the exhaust emitted by automobiles and its dispersion into soil and selected plants near highways. The elements chosen for this study were the major traceable components of gasoline and automobile exhaust. Variations in the concentrations of these trace elements in soil, grass and wash off the grass at various distances from two highways were investigated. Of the elements found in gasoline and in automobile exhaust, bromine most clearly indicated where some of the atmospheric components were going and, therefore, would be the most suitable element for neutron activation studies of atmospheric and turbulence modeling and possibly for following biological effects of automobile traffic.
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    Pest management guide for soybeans
    McPherson, Robert M.; Smith, John C.; Roberts, James E. Sr.; Phipps, Patrick M.; Rud, O. E.; Wilson, H. P.; Foy, Chester L. (Virginia Cooperative Extension Service, 1981-01)
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    Physiological aspects of broomrape (Orobanche spp.) parasitism, host specificity and selective control by glyphosate
    Jain, Rakesh (Virginia Polytechnic Institute and State University, 1987)
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    Selective Control o Egyptian Broomrape (Orobanche Aegyptiacapers.) by Glyphosate and its Amino Acid Status in Relation to Selected Hosts
    Nandula, Vijay K. II (Virginia Tech, 1998-02-05)
    Broomrapes are achlorophyllous holoparasites of many economically important dicotyledonous crops. As weeds, they cause reductions in crop yield, adversely affect crop quality, and result in loss of cultivated land due to reduced crop alternatives. Few effective control measures exist for broomrapes. One of the most promising approaches is the use of low rates of glyphosate in hosts with tolerance to the herbicide. Recently, availability of glyphosate-resistant crops has provided an alternative in broomrape infested areas. Knowledge about the nitrogen status of broomrapes is essential for developing new control strategies. Broomrapes have two potential sources of amino acids. First, the haustorium aids in the translocation of amino acids from the host plant to the parasites. Second, broomrapes may be able to synthesize some amino acids themselves and obtain the rest from the host. However, the relative importance of these two modes of acquiring amino acids by broomrapes is not clear. Osmotic stress has been implicated as a possible reason for inhibition of broomrape germination by nitrogen. To date, there has been no attempt to correlate osmotic potential with nitrogen induced inhibition of broomrape germination. Optimum temperatures for conditioning and germination are different among broomrape species. Although temperature is known to influence germination in broomrape, its effect on subsequent development of the parasitic seedling has not been studied. Studies were conducted to determine the use of glyphosate in controlling broomrape in common vetch that is tolerant to low rates of glyphosate, and to compare this response with broomrape control in oilseed rape that has been genetically engineered for glyphosate resistance. Glyphosate dose response studies using a commercial formulation and patterns of absorption, translocation, and metabolism, using ¹⁴C-glyphosate, were determined for both host crops. Glyphosate significantly reduced the growth of broomrape at 0.18 and 0.36 kg ae ha⁻¹> in common vetch and 0.25 to 0.75 kg ha⁻¹ in oilseed rape. More than 25% of translocated ¹⁴C-glyphosate in both host crops accumulated in broomrape tubercles. Broomrape parasitism caused a redistribution of translocated ¹⁴C-glyphosate in the roots of both host crops. Glyphosate was metabolized up to 25% in common vetch, but remained intact in oilseed rape. Studies were conducted to analyze amino acid composition of both nonparasitized and broomrape-parasitized hosts and associated broomrape after hydrolysis and phenylisothiocyanate derivatization of amino acids. Results indicated that amino acid concentrations of leaves of parasitized carrot plants were lower than those of the leaves of nonparasitized carrot plants. Broomrape tubercles had equal or higher amino acid concentrations compared to those of the leaves of nonparasitized carrot plants. Levels of free alanine and arginine concentrations of broomrape callus were higher than those of any other tissue of either carrot or broomrape. The effect of glyphosate on the host-broomrape interaction regarding amino acid metabolism was examined. Glyphosate generally increased the amino acid concentrations in common vetch and oilseed rape plants, and broomrape attachments. The aromatic amino acids, phenylalanine and tyrosine, did not differ from this pattern. Concentrations of certain amino acids in broomrape were similar to those of parasitized common vetch and parasitized oilseed rape, whereas levels of several others, were higher in broomrape attachments compared to the host plants. In vitro studies were conducted to determine the influence of osmotic potential and temperature on broomrape germination. Osmotic potential significantly affected germination and radicle elongation of broomrapes. No correlation was found between osmotic potential and ammonium-induced inhibition of germination of broomrapes. Temperature significantly influenced germination and radicle elongation of all broomrape species tested.
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    Selectivity and soil behavior of chlorsulfuron
    Mersie, Wondimagegnehu (Virginia Polytechnic Institute and State University, 1985)
    Response of barley (Hordeum vulgare L.) and wheat (Triticum aestivum L.) to root-applied chlorsulfuron (2-chloro N-[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl) amino] carbonyl] benzenesulfonamide), a herbicide for use in small grains, was investigated. The results showed that, although wheat roots take up more chlorsulfuron than barley roots, barley was less tolerant to chlorsulfuron and chlorsulfuron was more mobile in barley. This study indicated that difference in uptake or translocation cannot explain the differential response of the two species to root-applied chlorsulfuron. In an interaction study, significant chlorsulfuron antagonism on ryegrass (Lolium multiflorum Lam.) control by diclofop {(±)[-2-[4-(2,4-dichlorophenoxy) phenoxy) propanoic acid} was observed. Greenhouse experiments showed that the tolerance of corn (Zea mays L.) to chlorsulfuron and metsulfuron (2-[[[[(4-methoxy-6-methyl-l,3,5-triazin- -2-yl) amino] carbonyl] amino] sulfonyl] benzoic acid) was greatly increased by seed dressing with the herbicide safener NA (1,8-naphthalic anhydride). The soil behavior of chlorsulfuron was studied in the field, greenhouse and laboratory. In the field, corn adequately tolerated soil residues present 10 months following postemergence application of chlorsulfuron at 10 to 120 g/ha. However, at the same site and rates, residues from chlorsulfuron injured corn when sampled 2 months after application. In laboratory studies chlorsulfuron was moderately adsorbed by organic matter but showed low affinity to clay. Rf values calculated from soil thin-layer chromatography closely correlated with the mobility of chlorsulfuron leached with 16.8 cm of water over a 14-day period in hand-packed soil columns. In the soil thin-layer chromatography, chlorsulfuron mobility was positively and negatively correlated with pH and organic matter, respectively. The results indicated that chlorsulfuron could be mobile in low organic matter and non-acidic soils. The relationship of chlorsulfuron phytotoxicity to soil physical and chemical properties was also evaluated. Organic matter was inversely related to chlorsulfuron phytotoxicity while no such relationship to clay content was observed. The adsorption of chlorsulfuron decreased with increasing soil pH whereas desorption was greater at alkaline pH.
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    Studies on the mechanisms of action of the herbicide safener CGA- 92194
    Zama, Paul (Virginia Polytechnic Institute and State University, 1985)
    CGAr92194 {α-[1,3-dioxolan-2-yl-methoxy)imino]benzeneacetonitrile} is a herbicide safener that is used as a seed dressing agent (1.25 g ai/kg seeds) to protect grain sorghum [Sorghum bicolor (L.) Moench] against metolachlor [2-chloroi-N-(2-ethyl-6-methylphenyl-N-(2-methoxy1-methylethyl)acetamide] injury. The potential adverse phytotoxic effects and the mechanisms of the protective action of this safener were studied in laboratory experiments. Adverse phytotoxicity was assessed by comparing CGA-92194 and the herbicide safeners cyometrinil {(Z)-α[(cyanomethoxy)imino]benzeneacetonitrile} and flurazole [phenylmethyl 2-chloro-4-(trifluromethyl)-5-thiazolecarboxylate] for their effects on CO₂ fixation, protein, DNA, RNA and lipid syntheses of enzymatically isolated leaf cells of soybean [Clycine max (L.) Merr]. At physiological concentrations of less than 10 μM, CGA-92194, cyometrinil and flurazole were stimulatory of all metabolic processes. At 100 μM, the safeners were inhibitory of the five processes with flurazole being the most potent. The mechanisms of the safening action of CGA-92194 were studied by examining the potential interactions of this safener with metolachlor at the levels of uptake and macromolecular syntheses in enzymatically isolated leaf mesophyll protoplasts of grain sorghum. The influence of CGA-92194 on the in vitro reactivity of metolachlor with glutathione (GSH) and it metabolism by sorghum seedlings were also examined. When CGA-92194 and metolachlor were given simultaneously, CGA-92194 enhanced the uptake of ¹⁴C-metolachlor into the sorghum protoplasts in a concentration-dependent pattern. Thus, interference with herbicide uptake is not involved in the protective action of this safener Treatments with metolachlor and CGA-92194 in combination inhibited the incorporation of ¹⁴C-uracil, ³H-thymidine and ¹⁴C-acetate into sorghum protoplast macromolecules less than metolachlor given alone, suggesting the potential involvement of a competitive antagonism in the mechanism of action of CGA-92194. The metabolic activity and growth of sorghum seedlings grown from CGA-92194-pretreated seeds was significantly lower than that of seedlings grown from untreated seeds at 10 or 20 days after planting, The relationship of these effects of CGA-92194 to its safening action is unclear at the present time. CGA-92194 increased the in vitro chemica1 reactivity of metolachlor for GSH in a concentration-dependent pattern, Sorghum seedlings grown from safener-pretreated seeds enhanced ¹⁴C-metolachlor absorption and stimulated its metabolism via conjugation to GSH. This stimulation was reduced by tridiphane [2-(3,5-dichlorophenyl)-2-(2,2,2-trichloroethy1)- oxirane] a potent inhibitor of plant GSH-S-transference enzymes, These results indicate that a safener-induced stimulation of the spontaneous or enzymatic conjugation of metolachlor with GSH is most likely involved in the protective action of CGA-92194. It is suggested that the safening mechanism of action of CGA—92194 involves a sequence of multilevel interactions which together contribute to the overall protection of grain sorghum from metolachlor injury.