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109 218 226 Hoekstra S., van Bergen S., van Brouwershaven I. R., Schilperoort R. A. Heidekamp F. (1996). The interaction of 2,4-D application and

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. Its chemical composition was determined to be as Na 2 Si 14 O 29 ·9H 2 O [ 15 , 16 ]. In this study, magadiite was used as host to remove the following herbicides: 2,4- d (2,4-dichlorophenoxyacetic acid), and Diuron (3-(3,4-dichlorophenyl)-1

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A 2-year field study was conducted during the rainy seasons of 1999 and 2000 at Houfa in northern Jordan, to study the performance of two wheat cultivars ACSAD 65 and F8 and their response to hand weeding (practised monthly during the growing seasons) and 2,4-D application at different growth stages. In both growing seasons, no significant differences (P≤0.05) in grain yield were recorded between the cultivars studied. Differences in weed number and fresh weight were significant between the various treatments in both seasons. Hand weeding proved the best method of weed control. In both growing seasons, yield reductions occurred when 2,4-D was applied to wheat, irrespective of the stage of application. Hand weeding treatment was more effective than 2,4-D application in suppressing weed growth.

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Abstract  

A method based on neutron activation analysis was developed for the determination of fractions of milligrams of 2,4-D (2,4-dichlorophenoxy acetic acid) in aqueous solution in laboratory tests. The indirect determination of 2,4-D was based on the quantification of chlorine,38Cl, produced by neutron activation. The range of application was 0.01–100 mg l−1. No loss of38Cl by chemical effects of the nuclear reaction was found. The advantages of the proposed method include high precision and sensitivity of determination. Results were compared with those obtained by UV-Vis spectrophotometry, where concentrations less than 1 mg·l−1 were not detected.

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Acta Agronomica Hungarica
Authors: S. P. Saikia, S. P. Saikia, V. Jain, V. Jain, G. C. Srivastava, and G. C. Srivastava

Research over the last few years has shown that inoculation with nitrogen-fixing bacteria of the genus Azorhizobium presents an alternative for (or supplement to) chemical fertilization, mainly due to the capability of the bacteria to produce plant growth- promoting hormones. The Azorhizobium caulinodans strain ORS 571 in combination with 2,4-D was able to colonize the root interior of an Indian maize cultivar. After transplanting to pots, it was noticed that nodulated and Azorhizobium -treated plants showed higher chlorophyll content in the leaf and enhanced nitrate reductase activity, leading to higher yield as compared to the control plants (non-nodulated). A plant growth-promoting effect was clearly visible in all inoculated plants examined. nodulated plants treated with Azorhizobium had higher physiological activities as compared to plants treated only with Azorhizobium . Azorhizobium therefore creates potentially better symbiosis in the form of para -nodules and promotes a higher level of nitrogen fixation, leading to better growth and plant development, with reduced requirements for chemical fertilizers.

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Abstract  

The paper presents the conditions under which compounds of the commercial herbicides, 2,4-dichlorophenoxyacetic acid (2,4D; C8H6O3Cl2) and 2-(2,4-dichlorophenoxy)-propionic acid (2,4DP; C9H8O3Cl2), with lead(II) and cadmium(II) are formed and the results of the examination of their properties.On the basis of the elemental analysis and Pb and Cd determination, the following molecular formulae for the obtained compounds were proposed: Pb(C8H5O3Cl2)2.H2O, Cd(C8H5O3Cl2)2.2H2O, Pb(C9H7O3Cl2)2·H2O and Cd(C9H7O3Cl2)2·H2O. Water solubility of the synthesized complexes at room temperature was examined. X-ray powder analysis was carried out. The discussion of IR spectra and conductivity data is presented. Thermal decomposition of these compounds in air was studied by TG/MS methods.

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Summary

2,4-Dichlorophenoxyacetic acid (2,4-D) is a phenoxy group of herbicide used worldwide. As it is extensively used, it has consequential problems on living beings. 2,4-D is degraded into the chlorinated phenols and catechols, and these phenol compounds are more hazardous than the parent 2,4-D herbicide. In this paper, an attempt is made to detect 2,4-dichlorophenol in 2,4-D poisoning cases from human viscera. Sensitive and selective detection of 2,4-dichlorophenol using high-performance thin-layer chromatography (HPTLC) is possible by coupling it with 4-amminoantipyrene in the presence of potassium ferricyanide. Standard 2,4-dichlorophenol and human visceral extract are allowed to run on an HPTLC plate with hexane, acetone, and ethyl acetate as the mobile phase. Mechanistically, 4-amminoantipyrene reacts with 2,4-dichlorophenol in the presence of potassium ferricyanide to form p-quinoneimide which is brick red in color. This known reaction is, for the first time, applied to detect 2,4-dichlorophenol in 2,4-D poisoning cases from human viscera. The formation of brick red color spot on the HPTLC plate allows the easy and confirmed detection of 2,4-dichlorophenol in 2,4-D poisoning case. This HPTLC method is simple and easy to work in laboratory. The reagents do not react with the parent 2,4-dichorophenoxyacetic acid and other organophosphorus, organochlorine, carbamate, and pyrethroid insecticides, i.e., these reagents are specific. The constituents of the viscera (amino acids, peptides, proteins, etc.) and plant material do not interfere with the reagents. The presence of 2,4-dichlorophenol in the same visceral sample is confirmed by gas chromatography-mass spectrometry (GC-MS). The detection limit of reagents for 2,4-dichlorophenol is approximately 0.5 µg.

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Abstract  

The reactions of hydroxyl radical and hydrated electron intermediates of water radiolysis were studied in the radiolytic degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) at pH values of 4, 6 and 8. The hydrated electron reactions are also suggested to contribute to the aromatic ring decomposition in addition to the highly effective hydroxyl radical reactions. The experimental results suggest also some contribution from the O2 −•/HO2 pair to the degradation. The degradation efficiency was found to be the highest at pH 8 and the lowest at pH 6.

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A simple and efficient protocol has been developed for high frequency plant regeneration through callus cultures derived from leaf bases of abiotic stress sensitive Asian indica rice variety IR 64. Leaf base segments (4–5 mm diameter) were obtained from 6-day-old dark grown seedlings germinated on halfstrength Murashige and Skoog medium and cultured on MS medium supplemented with different concentrations of 2,4-Dichlorophenoxyacetic acid (2.2–18 μM) and Kinetin (0.2–1.7 μM). Among the various combinations, 13.5 μM 2,4-D and 1.3 μM Kn resulted in high callus induction frequency (87.5%) with a maximum fresh weight of 0.22 g per segment. The regeneration frequency was 75.5% with multiple shoots within 3 weeks of transfer on MS medium supplemented with 13.3 μM 6-benzylamino purine and 8 μM Naphthaleneacetic acid. The shoots readily rooted on half-strength MS medium without any hormonal supplements. In vitro regenerated plantlets with multiple shoots and roots were transferred to sterile soil and vermiculite mix and maintained in shade house for 30 days. Complete plantlets were then transferred to nursery and acclimatized to the external environment until seed set. RAPD profile reveals monomorphism and thus confirming the genetic stability of the regenerated plants. This method has the potential for both direct as well as indirect method of transformation for the production of genetically modified plants.

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The effect of explant type (immature vs. mature embryos) and two auxin types (2,4-dichlorophenoxyacetic acid vs. Dicamba) on the callogenesis and plant regeneration ability of 26 wheat cultivars was studied. In general, the callus induction, plant regeneration and shoot formation frequencies were higher in mature embryo-derived cultures as compared to immature ones on media originally developed for mature wheat embryo cultures. In both culture types, the auxin Dicamba was found to be more efficient, especially when mature embryos were cultured. The separation of means using Duncan’s multiple range test revealed the best in vitro response, in terms of the frequency of callus regeneration, in the cultivar Astella for both immature and mature embryo cultures. This cultivar gave very promising results, suggesting that it could be used in the future for further tissue culture investigations and as a donor material for genetic transformation experiments in wheat. Correlation analyses revealed significant similarities between the evaluated parameters within each group (immature and mature embryo-derived cultures). However, there were no significant correlations between these two groups for most of the parameters. This suggests that the mechanism of plant regeneration in the two in vitro regeneration systems (mature vs. immature embryo culture) may be different enough to hamper the development of an optimal plant regeneration protocol for use in both systems.

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