High Concentrations Of Herbicide Research Articles

Growth, carbohydrates and associated invertase and amylase activities in castor bean and maize as affected by metribuzin and NaCl

Growth parameters (leaf area, length of shoot and root, water content and dry matter accumulation), contents of reducing sugars and saccharose as well as activities of α- and β-amylases of castor bean and maize seedlings and adult plants supplemented with 0.5 μg g-1 and 2.5 μg g-1 of metribuzin either alone or in combination with 50 μg g-1 NaCl, were increased significantly whereas at high concentrations (5 and 10 μg g-1) of herbicide, an opposite response was apparent. On the other hand, polysaccharide content and invertase activity of castor bean and maize seedlings and adult plants were significantly decreased in response to low concentrations (0.5 and 2.5 μg g-1) of metribuzin and increased significantly at high concentrations (5 and 10 μg g-1) of the herbicide either alone or in combination with 50 μg g-1 NaCl. Total carbohydrate contents of castor bean and maize seedlings and whole plants treated with herbicide either alone or in combination with NaCl did not change significantly. Growth parameters, carbohydrate fractions contents and activities of enzymes in both castor bean and maize seedlings and whole plants treated with herbicide alone were consistently higher than those values detected in plants treated with herbicide in combination with NaCl.

Factors influencing the adsorption of atrazine on montmorillonitic and kaolinitic clays

The herbicide atrazine, a member of the S-triazine family was reacted with a montmorillonitic and a kaolinitic clay, two soil constituents of different mineralogical composition and with different adsorption properties. The clays were characterized by determination of the cation exchange capacity (CEC), the total and internal surface area and the particle size distribution. X-ray diffraction studies were made to acquire the mineralogical composition of the two clays. The influence of the initial pesticide concentration, the pH and the solid/liquid ratio on the adsorption of atrazine was tested in a miniaturized approach, yielding less than 5 ml of suspension per sampling. Freundlich adsorption isotherms were set up to determine the Freundlich k and l/n values. Heat of adsorption ΔH and the velocity of the establishment of a steady state were determined. Furthermore, investigations on the desorbability of the pesticide adsorbed were made. The montmorillonitic clay adsorbed a great amount of the pesticide in contrast to the kaolinitic one. Montmorillonite reached apparent adsorption equilibrium within a few minutes while establishment of apparent equilibrium with kaolinite took some days. ΔH varied between 10 and 50 kJ mol−1. Adsorption increased with higher herbicide concentrations and decreased with rise in temperature. Larger solid/liquid ratios diminished adsoprtion coefficients. All experiments were carried out with dry as well as with water-saturated montmorillonitic clay. Desorption experiments showed that only part of the herbicide adsorbed was desorbable by several subsequent water treatment steps. For the first time immunoassay technology in the form of an ELISA (enzyme-linked immunosorbent assay) selective for atrazine was applied to detect low concentrations of the analyte in the few milliliters of eluent obtained in this miniaturized approach.

Immunofluorescence and electron microscopic investigations of the effects of dithiopyr on onion root tips

Light, immunofluorescence, and electron microscopy are used to investigate the effects of dithiopyr [ S,S-dimethyl 2-(difluoromethyl)-4-(2-methylpropyl)-6-(trifluoromethyl)-3,5-pyridine-dicarbothioate] on onion root meristems. At high herbicide concentrations (10 −4, 10 −5 M) all of the dividing cells are in an arrested prometaphase configuration although, at lower concentrations (10 −6, 10 −7 M), multipolar mitosis, along with some apparently normal mitotic figures, also are noted. Immunofluorescence microscopy reveals that nearly all of the microtubules are absent after treatment with high concentrations of herbicide, although small tufts of microtubules remain at the kinetochore. These kinetochore tufts are confirmed to be microtubules (and not just aggregates of tubulin protein) by electron microscopic analysis. Phragmoplast arrays are absent at these higher concentrations and no cell plates are formed. Nuclei that reform after the arrested prometaphase or multipolar division are irregularly formed, either highly lobed or fragmented into multiple nuclei. Branched and undulating phragmoplast microtubule arrays oriented in abnormal directions are observed frequently after 10 −6 M treatment. The walls that result from these abnormal phragmoplasts are also unusual. Branched walls, multiple walls/cell, walls with electron opaque depositions, and incomplete reticulate walls are also noted. Because dithiopyr does not bind tubulin, we propose that this herbicide destabilizes microtubules as they are formed so that only short microtubules result. These shortened, destabilized microtubules are ineffective in chromosome movement during mitosis or other cellular functions involving microtubules. Thus, the net effects of dithiopyr are similar to those compounds that cause complete microtubule loss, such as trifluralin or amiprophosmethyl, even though the mechanism of disruption is different.

Microbial responses to large concentrations of herbicides in soil

To determine the effects of herbicide spills on microbial activity, soil was treated with excessive amounts (10,000 mg/kg) of formulated alachlor alone or as a mixture with formulated atrazine, metolachlor, and trifluralin. Soil was also treated with the same combinations of herbicides at a rate of 10 mg/kg, which is typical of normal farming practices. Simulated spills initially inhibited bacteria, but after 7 d, bacterial numbers had recovered to levels similar to those in untreated controls. Fungal populations were drastically reduced after 1 d and became undetectable after 7 and 21 d of incubation in the mixed herbicide and alachlor-only treatments, respectively. Dehydrogenase activities were severely depressed after 1 d in both high-level herbicide treatments and did not recover after 125 d. Esterase activities were depressed in soils receiving the mixture of herbicides but were generally unaffected in the alachlor-only treatment. Normally applied concentrations did not have any pronounced effect on bacterial and fungal populations or on the activities of soil dehydrogenase and esterase. At 10 mg/kg, all the herbicides degraded by 80 to 90% within one year; there was no difference between degradation of alachlor applied alone or as a herbicide mixture. With high concentrations of herbicides, degradation was negligible after one year of incubation.

Effect of fenoxaprop, haloxyfop and sethoxydim on acetyl coenzyme A carboxylase from rice, barnyardgrass and sprangletop

Acetyl coenzyme A carboxylase (ACCase), the target site inhibited by two groups of herbicides, the aryloxyphenoxypropionates and cyclohexanediones, was extracted and partially purified from rice ( Oryza sativa LeMont L.), barnyardgrass ( Echinchloa crusgalli (L.) Beauv.) and sprangletop ( Leptochloa fascicularis (Lam.) Gray). This was to determine whether the lack of inhibition of rice to three grass toxic herbicides, haloxyfop, fenoxaprop and sethoxydim is due to a differential selectivity at the enzyme level. Incorporation ration rates of NaH 14CO 3 into malonyl coenzyme A (CoA) were linear up to 8 min and maximum specific activity was obtained at 0.1–0.2 mg protein. Inhibition of ACCase from rice and the two weed species by haloxyfop and fenoxaprop showed differences that disappeared with higher concentrations of herbicide. I 50 values for haloxyfop inhibition of ACCase from rice, barnyardgrass and sprangletop were 3.50, 2.50 and 2.40 μM, respectively. I 50 values for fenoxaprop inhibition of enzyme from rice, barnyardgrass and sprangletop were 0.63, 0.33 and 0.33 μM, respectively. ACCase from rice was more sensitive to sethoxydim than from the two grass weeds. I 50 values for rice, barnyardgrass and sprangletop were 6.18, 6.76 and 7.23 μM, respectively. These results suggest that selectivity of fenoxaprop and haloxyfop in rice may be in part attributable to a decreased sensitivity of ACCase, but this cannot totally account for the margin of tolerance exhibited in the field.

Effect of the triazine herbicides Goltix and Igran on germination and growth of Aspergillus fumigatus, Fusarium oxysporum, Helminthosporium oryzae, and Verticillium agaricinum

The effect of two triazines on spore germination, radial growth, and biomass production were studied in A. fumigatus, F. oxysporum, H. oryzae, and V. agaricinum. Igran inhibited spore germination of all species to some extent and at 1000 ppm completely inhibited spore germination in A. fumigatus and F. oxysporum. Goltix inhibited germination of F. oxysporum and H. oryzae, but stimulated germination of A. fumigatus and V. agaricinum. Germ tube length was significantly decreased at high herbicide concentrations. Both derivatives reduced radial growth rate as well as mycelial growth in liquid cultures. The level of inhibition depends on the herbicide, its concentration, and the fungal species.

A second mutation enhances resistance of a tobacco mutant to sulfonylurea herbicides

Cultures of Nicotiana tabacum cells homozgous for a mutation (S4) at the SuRB locus that confers resistance to the sulfonylurea herbicides chlorsulfuron and sulfometuron methyl (Chaleff and Ray 1984; Chaleff and Bascomb 1987) were used to isolate a doubly mutant cell line (S4 Hra/S4+) resistant to even higher herbicide concentrations. Growth of cells homozygous for both the S4 and Hra mutations (S4 Hra/S4 Hra) was uninhibited by a herbicide concentration 500-fold higher than a concentration by which growth of S4+/S4+ callus was inhibited by 75%. Plants homozygous for both mutations were at least five-fold more resistant to foliar applications of chlorsulfuron than were singly mutant S4+/S4+ plants. This enhanced resistance was inherited as a single, semidominant, nuclear trait that is genetically linked to the S4 mutation. Acetolactate synthase (ALS) activity in extracts of leaves of doubly mutant (S4 Hra/S4 Hra) plants was approximately 20-fold more resistant to inhibition by chlorsulfuron and sulfometuron methyl than was ALS activity in singly mutant (S4+/ S4+) leaf extracts, which was in turn more resistant to inhibition by these compounds than was the normal enzyme. Extracts prepared from plants of these three genotypes possessed the same ALS specific activities. Therefore, Hra represents a second independent mutation at or near the SuRB locus that reduces the sensitivity of tobacco ALS activity to inhibition by sulfonylurea herbicides.

Comparative herbicide binding by photosynthetic membranes from resistant mutants

Resistance patterns against herbicides inhibiting photosynthetic electron transport have been obtained from several mutants of higher plants and algae. While most of the herbicides assayed show varying resistance patterns with different mutants, resistance against metribuzin is generally very high and always present. On the other hand, no resistance is measured using the phenol-type herbicide ioxynil. With both herbicides replacement experiments vs 14C-labeled atrazine yield a mixed-type competition, i.e., loss of binding sites (receptors) and increasing binding constant. Contrary to ioxynil, the phenol-type herbicide bromonitrothymol gives normal binding and (competitive) replacement data. A mutant of Bumilleriopsis filiformis was isolated which is resistant against bromonitrothymol. Resistance generally does not lead to total loss of binding of a certain inhibitor. A model with two independent receptors at a binding protein is presented, which may explain the nonspecific binding at high herbicide concentrations.

Aschegehalt und Mineralstoffmenge der oberirdischen Organe zweier Waldgräser nach Herbizidbehandlung

Summary Calamagrostis villosa and Deschampsia flexuosa growing in a spruce forest were treated with the herbicide Azaplant-Kombi (30 % simacine, 30 % amitrol). The ash content (%) of the plant tops increased with higher herbicide concentration and time whereas the minerals quantity decreased. The paper elucidates on the fundamental relations between biomass, ash content and minerals quantity. The relationship between herbicide concentration and its effect on biomass and the quantity of minerals and organic substance are described by functions of the type y = a + b • e CX .

THE EFFECT OF BIPYRIDYL HERBICIDES ON THE LOSS OF NUTRIENTS FROM FUNGI

SummaryParaquat and diquat cause rapid loss of potassium and phosphate from Aspergillus niger, Penicillium frequentans, Mucor hiemalis and Zygorrhynchus heterogamus. The rate of loss is greater at higher concentrations of herbicide, particularly from Zygorrhynchus and Mucor. A brief incubation in paraquat or diquat is followed by sustained loss of potassium when colonies of the four species are transferred to water. Sodium azide also stimulates loss of potassium but thisceases when colonies are transferred to water. Paraquat enhances the level of malondialdehyde, a breakdown product of membrane fatty acids, in Zygorrhynchus and Mucor. These results are discussed with reference to the possible mode of action of bipyridyl herbicides in fungi.

Veränderung der Krankheitsdisposition von Forstpflanzen durch Herbizide1

Modification in discase-sensibility of forest plants by herbicide treatment. I. Field trials with Lophodermium pinastri. The effect of two herbicides TOP-KH (salt of 2,4,5-T) and Casoron G (Dichlobenil) on incidence of Lophodermium pinastri on Scots pine (Pinus sylvestrii L.) was investigated in field trials with potted plants. Treatment with TOP-KH led to increase in infection with higher herbicide concentrations and to higher numbers of severely infected plants in comparison with controls. Differences were greatest in spring. With Casoron G, however, smaller numbers of sevcrely infected plants were seen in spring and at the end of the growing season the damage was not much greater than in the controls. Possible reasons for changes in degree of infection are discussed as well as effects that could be expected on the epidemiology of pine needle cast.

PERSISTENCE AND MOVEMENT OF ATRAZINE, BROMACIL, MONURON, AND SIMAZINE IN INTERMITTENTLY-FILLED IRRIGATION DITCHES

Atrazine (22.4 kg/ha), bromacil (15.2 kg/ha), monuron (35.8 kg/ha), and simazine (22.4 kg/ha) were applied to especially prepared irrigation ditches in the fall of 1970. Soil samples from ditch sides, ditch bottoms, and basins irrigated with water were taken during 1971, 1972, and 1973 seasons. Water samples were also taken during these years. The soil and water samples were analyzed chemically to determine the herbicide residues remaining in the ditches and basins, their movement in the soil profile, and the amount of herbicides carried in the flowing water over the 3-yr period. The order of persistence for the four herbicides was simazine > atrazine > monuron > bromacil. Atrazine, bromacil and monuron residues were distributed uniformly throughout the 90-cm soil depth by the third growing season. The greater part of simazine residues was, however, still present in the top 7.5-cm soil layer. In irrigation waters, the highest herbicide concentrations were in the initial ponding in the spring of 1971, decreasing by a factor of two- to fivefold in the second filling in 1971. The relative amounts of each herbicide in the first two water samplings were inversely proportional to their respective water solubilities.

Toxicity of Various Formulations of 2,4-D to Salmonids in Southeast Alaska

To determine acute toxicity to juvenile (1) pink, chum, coho, and sockeye salmon, (2) Dolly Varden char, and (3) rainbow trout, 2,4-D acid, butyl and isooctyl esters were tested in southeast Alaska. A comparable test was made in Oregon using coho salmon fingerlings. The mean percent mortality after 96 h and the highest concentration of herbicide that did not produce any mortality were determined for each formulation tested.At less than 50 ppm 2,4-D acid produced no mortality except in pink salmon fry. The butyl ester was most toxic causing nearly complete mortality in all species at concentrations > 1.0 ppm and the isooctyl ester least toxic of the ester formulations. Alaskan and Oregon coho fingerlings were similar in their responses to 2,4-D acid, butyl and isooctyl esters. The toxicities of three different formulations of isooctyl ester, a PGBE ester, and butyl ester to Alaskan coho fingerlings were also determined. There were few or no differences in toxicity among isooctyl ester formulations. The butyl and PGBE esters were similar in toxicity.

LABORATORY STUDIES ON GLYCERIN AS A SUPPLEMENT IN WATER–SOLUBLE HERBICIDAL SPRAYS

WATER-SOLUBLE herbicides such as arsenicals and ammonium sulfamate, applied as sprays, have shown considerable promise for eradication of noxious vegetation. However, results with sprays have been highly variable and, due to the high concentrations of herbicide required, relatively expensive. In order to increase the effectiveness of herbicidal sprays, the following laboratory studies were undertaken during the winter season of 1943-44, to determine the factors that promote transfer of sprayed herbicides from the leaves to the base of the stem. PROCEDURE.-The tests were conducted on potgrown plants about 6 inches tall which could be easily manipulated so as to expose them to different conditions and treatments. The results given in this report were obtained with Coleus blumei Benth. and Cuphea platycentra Lem., two common house plants. The two species appeared to react similarly, so that the principles determined in this investigation may be applicable to a number of species. Two methods of application were used in the study. In the one, referred to as tip-injection, the solution of poison was placed in a small vial which was so suspended that the tip of the plant could be dipped into the liquid. This method, although not a practical field technique, indicated experimentally the action of the poison in penetrating and being conducted downward through the stem when the foliage was in continuous contact with the herbicide solution. In the second technique, referred to as leaf application, the solution was applied with a camel's hair brush to the upper leaves. This method was analogous to spraying of sprouts in the field. The solutions dried on the surface of the leaf within a short time, usually 10 to 15 minutes. For the leaf application technique, a commercial sodium lauryl sulfate mixture was added to the herbicide solutions at a rate of 0.12 per cent to serve as a wetting agent.