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[Pathophysiologic and nutritional effects of amino-4-trichloro-3,5,6-picolinic acid (picloram) in rats].
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[Toxicity and nutritional effects, in the rat, of 2 herbicides: picloram (4-amino-3,5,6-trichloropicolinic acid) and atrazine (2-chloro-4-ethylamino-6-isopropylamino-S-triazine)].
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Teratology and postnatal studies on 4-amino-3,5,6-trichloropicolinic acid (picloram) in the rat.
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Novel determinations of picloram by gas-liquid chromatography.
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An inexpensive and efficient pyrolysis unit for the analysis of picloram and other herbicides by thermal decomposition.
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The determination of picloram in fescue by gas-liquid chromatography.
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A new technique for the determination of picloram and other herbicides containing carboxylic acid and ester groups.
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Picloram photolytic decomposition.
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A gas-chromatographic determination of residues of Picloram.
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Pesticides in soil. The persistence and movement of picloram in Texas and Puerto Rican soils.
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Comparison of flash-induced light-scattering transients and proton efflux from auxinic-herbicide resistant and susceptible wild mustard protoplasts: a possible role for calcium in mediating auxinic herbicide resistance.
Comparison of flash-induced light-scattering signals from protoplasts of auxinic herbicide-resistant ('R') and -susceptible ('S') wild mustard biotypes suggest that ATP-dependent activity manifested as a conformational change differs between the biotypes. The signal obtained from R protoplasts is unaffected by 50 microM picloram, an auxin analogue. In comparison, the signal amplitude from the S protoplasts decreases 40% in 20 microM picloram and is abolished in 50 microM picloram. Signal amplitude from the R protoplasts can be decreased by simultaneous incubation with 50 microM picloram and 50 microM verapamil, a calcium channel blocker. Incubation of the S protoplasts with the calcium ionophore A23187 in the presence of 0.5 mM calcium reduced the inhibitory effect of picloram. Absorbance spectrophotometry using acridine orange as a pH indicator suggests that picloram affects the proton flux in the S biotype only. Based on these results, we hypothesize that picloram affects the calcium and hydrogen dynamics in the S biotype. Because the scattering characteristics of S protoplasts incubated with picloram can be nearly reproduced in the R protoplasts by simultaneous incubation with picloram and verapamil, calcium may have a significant role in modulating auxinic herbicide resistance. To our knowledge, this is the first report to implicate such a role for calcium.
A highly efficient plant regeneration system through multiple shoot differentiation from commercial cultivars of barley (Hordeum vulgare L.) using meristematic shoot segments excised from germinated mature embryos.
A fast and highly efficient short-term in vitro regeneration system was developed for barley (Hordeum vulgare L.) based on readily available explants. Clumps of multiple shoots and buds suitable for transformation were obtained 9-10 weeks after culture initiation from model and current commercial cultivars. Meristematic shoot segments (MSSs) excised from mature embryo-derived seedlings and subsequently cultured on MS-based medium containing 2 mg/l Picloram and 3 mg/l thidiazuron (TDZ) differentiated up to ten multiple shoots after 3-4 weeks with no or very little callus formation. Sectors of the already multiplied shoot clumps were further multiplied on proliferation-maintenance medium containing 2 mg/l Picloram and 2.5 mg/l TDZ. Biweekly subcultures resulted in a continuous process of multiplication of these highly differentiating green sectors without any loss of morphogenic potential. The differentiated small shoots and shoot buds gave rise to normal shoots on medium with 0.1 mg/l Picloram and 1 mg/l TDZ. After rooting on basal medium with 0.5 mg/l or 1 mg/l IBA the plants were transferred to soil and showed normal growth and fertility compared to the seed-grown plants. All of the genotypes tested formed multiple shoots. The percentage of relative MSS multiplication was 63-83%, and the average number of multiplied shoots per MSS ranged from 16 to 34 among the genotypes after 9-11 weeks.
Pesticide levels in surface waters in an agricultural-forestry basin in Southern Chile.
Residues of five pesticides in surface water were surveyed during 2001 and 2003 in the Traiguen river basin in Southern Chile. Simazine, hexazinone, 2,4-D, picloram herbicides and carbendazim fungicide were selected through a pesticide risk classification index. Six sampling stations along the river were set up based on agricultural and forestry land use. The water sampling was carried out before and after the pesticide application periods and in correspondence to some rain events. Pesticides were analyzed by HPLC with DAD detection in a multiresidue analysis. During 2001, in the first sampling campaign (March), the highest concentrations of pesticides were 3.0 microg l(-1) for simazine and hexazinone and 1.8 microg l(-1) for carbendazim. In the second sampling (September), the highest concentration were 9.7 microg l(-1) for 2,4-D, 0.3 microg l(-1) for picloram and 0.4 microg l(-1) for carbendazim. In the last sampling period (December), samples indicated contamination with carbendazim fungicide at levels of up to 1.2 microg l(-1). In sampling carried out on May 2003, no pesticides were detected. In October 2003, the highest concentrations of pesticides were 4.5 microg l(-1) for carbendazim and 2.9 microg l(-1) for 2,4-D. Data are discussed in function of land use and application periods of the products, showing a clear seasonal pattern pollution in the Traiguen river. Risk assessment for these pesticides was calculated by using a risk quotient (RQ = PNEC/PEC). For picloram the calculated RQ < was 0, which indicates that no adverse effects may occur due to the exposure to this herbicide in the Traiguen river basin. For 2,4-D, simazine, hexazinone, carbendazim RQ > 1, meaning that adverse effects could occur and it is necessary to reduce pesticide exposure in surface waters. It is recommended to continue with a pesticide monitoring program and the implementation of ecotoxicological testing with local and standardized species in order to consider the probability of effects occurrence, with less uncertainty. Thus, it will be more feasible to make some recommendations to regulatory agencies regarding the pesticide use.
Tradescantia-micronucleus and -stamen hair mutation assays on genotoxicity of the gaseous and liquid forms of pesticides.
The clastogenic and mutagenic effects of the insecticide Dimethoate (Cygon-2E), herbicides Atrazine, Simazine (Princep), Dicamba (Banvel D) and Picloram (Tordon) were studied using the Tradescantia-micronucleus (Trad-MCN) and Tradescantia-stamen hair mutation (Trad-SHM) assays. In clone 4430, dimethoate fumes both significantly increased the pink mutation events and reduced the number of stamen hairs per filament with increasing dosages. The pink mutation events were elevated by the liquid treatment with Picloram at 100 ppm concentration. The result of Trad-MCN test on Dimethoate fumes was not significantly different between the control and treated groups. The herbicide Atrazine showed positive effects at 10-50 ppm dose (liquid) and signs of overdose at 100 and 500 ppm concentrations. Simazine was mildly positive in elevating the MCN frequencies in the dose range of 5 to 200 ppm (liquid doses). Both Dicamba and Picloram induced a dosage-related increase in MCN frequencies in the Trad-MCN tests using Tradescantia clone 03. However, in higher dosages (200 ppm or higher), there were signs of overdose, reduction of MCN frequencies and physical damage of the leaves and buds of plant cuttings.
Effects of a herbicide formulation, Tordon 75D, and its individual components on the oxidative functions of mitochondria.
This investigation evaluates the toxicity of a herbicide formulation, as well as testing its active and other components (other components comprise all components of Tordon 75D excluding the active components: i.e. the solvents, triisopropanolamine and diethyleneglycol monoethyl ether, a silicone defoamer and a proprietary surfactant, polyglycol 26-2). The results showed that Tordon 75D (a mixture of the triisopropanolamine salts of 2,4-dichlorophenoxy acetic acid (2,4-D) and 4-amino-3,5,6-trichloropicolinic acid (picloram) and its other components) impaired the oxidative functions of submitochondrial particles (SMPs). The effective concentrations that caused 50% inhibition of SMP activity (EC50s) for Tordon 75D were in the low micromolar range for 2,4-D and picloram in the presence of the other components, while in the absence of the other components exposure to 136 times higher concentrations of the triisopropanolamine forms of 2,4-D and picloram administered as a mixture were required to inhibit the oxidative functions of SMPs. Tordon 75D also significantly decreased the respiratory control ratio of intact rat liver mitochondria. The results show that the toxic effects of Tordon 75D on SMPs (at the EC50) and intact rat liver mitochondria were not due to any additive or synergistic actions of a mixture of its active and other components, but rather were caused solely by the proprietary surfactant. Since mitochondria are responsible for over 90% of the energy production in all eukaryotic organisms, the use of the SMP assay provides a convenient in vitro assay for evaluating cellular toxicity and can be regarded as an informative screening assay when designing chemical products which contain mixtures of chemicals.
Effects of herbicides on two submersed aquatic macrophytes, Potamogeton pectinatus L. and Myriophyllum sibiricum Komarov, in a prairie wetland.
Clopyralid, picloram, 2,4-D and a mixture of 2,4-D plus picloram, (Tordon 202C) were added to the water of 1 m square enclosures in a prairie wetland in Saskatchewan, Canada to produce concentrations of 0.01 and 0.1 mg active ingredient litre(-1). Effects on the submersed macrophytes, Potamogeton pectinatus and Myriophyllum sibiricum, were monitored by taking repeated measurements of plant weight, flower and tuber production and inspecting for injuries at 30 and 60 days after application. Clopyralid did not inhibit weight gain (growth) in either species, but stimulated growth and flowering by M. sibiricum at 0.01 mg litre(-1) and tuber production by P. pectinatus at both rates. The low rate of 2,4-D stimulated flowering by M. sibiricum and tuber production by P. pectinatus, whereas the high rate inhibited growth of M. sibiricum and injured both species. Picloram did not affect growth of either species, but injured M. sibiricum at both concentrations and inhibited flowering at 0.1 mg litre(-1). Tordon 202C at 0.1 mg litre(-1) caused reduced growth and flowering in M. sibiricum and injured both species; 0.01 mg litre(-1) also injured M. sibiricum. Mortality resulted only from Tordon 202C and 2,4-D. Field data are lacking to assess the extent to which submerged macrophytes in prairie ponds are exposed to harmful concentrations of herbicide from aerial spraying, drift from ground application, runoff or wind erosion of soil.
Citrus Tissue Culture : AUXINS IN RELATION TO ABSCISSION IN EXCISED PISTILS.
An in vitro bioassay for chemicals that affect Citrus abscission was used to identify three inhibitors of stylar abscission in lemon pistil explants incubated on defined nutrient media. The three inhibitors (picloram, 4-chlorophenoxyacetic acid, and 3,5,6-trichloropyridine-2-oxyacetic acid) are all auxins, and the most potent of them (i.e. picloram) was found to be at least 10 times more active in the bioassay than 2,4-dichlorophenoxyacetic acid. Picloram (2 micromolar) also was shown to be effective in inhibiting stylar abscission in pistil explants from other Citrus cultivars such as mandarin, Valencia, and Washington navel oranges and grapefruit. To study the physiology of auxins active as abscission inhibitors versus inactive auxins in lemon pistils, the transport and metabolism of [1-(14)C]-2,4-dichlorophenoxyacetic acid was compared with that of [2-(14)C]indole-3-acetic acid, which is without effect in the bioassay over the range from 0.1-100 micromolar. Insignificant quantities of labeled indole-3-acetic acid and/or labeled derivatives were found to reach the presumptive zone of stylar abscission under the test conditions. Labeled 2,4-dichlorophenoxyacetic acid and/or labeled derivatives also were transported slowly through pistils, but some radioactivity could be detected in the stylar abscission zone as early as 24 hours after the start of incubation. Extensive conversion of [2-(14)C]indole-3-acetic acid to labeled compounds tentatively considered to be glycoside and cellulosic glucan derivatives was found with the use of solvent extraction methodology. A significantly smaller percentage of the radioactivity in pistils incubated on [1-(14)C]-2,4-dichlorophenoxyacetic acid was found in fractions corresponding to these derivatives. Both transport and metabolism appear to be important factors affecting the activity of auxins as abscission inhibitors in the bioassay.