Transformation of Herbicide Pentoxazone by Soil Microorganisms1
The metabolism of herbicide pentoxazone, 3-(4-chloro-5-cyclopentyloxy-2-fluorophenyl)-5-iso- propylidene-1,3-oxazolidine-2,4-dione, was investigated by soil microorganisms with a liquid medium applied with radiolabeled pentoxazone. Four different types of Japanese agricultural soils were inoculated as the sources of microorganisms. There was no marked difference in the degradation profiles among the four soils. Pentoxazone decreased rapidly, and N-(4-chloro-5-cyclopentyloxy-2-fluorophenyl)-3- methyl-2-oxobutanamide (A-0505, a hydrolysate at the carbonyl group of C2 in 1,3-oxazolidine-2,4-dione ring followed by decarboxylation) increased up to about 57% of applied dosage. After transient accumulation of A-0505, N-(4-chloro-5-cyclopentyloxy-2-fluorophenyl)-2-hydroxy-3-methylbutanamide (A-1374, a reduction product of A-0505) increased up to about 71%. The other metabolites, 4-chloro-5-(cyclopentyloxy)-2-fluoroaniline (A-0480, an aniline derivative), hydrated-pentoxazone (another hydrolysate at the carbonyl group of C4 in 1,3-oxazolidine-2,4-dione ring) and one unidentified compound were detected over 10% of applied dosage. Pentoxazone is likely to be readily transformed by ubiquitous soil microorganisms. These microbes which can proliferate in soil/water environment would play an important role in the progress of the degradation of pentoxazone.
1Microbial Metabolism of Herbicide Pentoxazone (Part 1).Key words: soil microorganisms, pentoxazone, degradation.
Pattern and Rate of Dissipation of Pretilachlor and Mefenacet in Plow Layer and Paddy Water under Lowland Field Conditions: A Three-year Study
Field trials were conducted at the National Institute of Agro-Environmental Sciences experiment station from 1995 to 1997. Each trial was carried out from mid-May to early July every year. Determining the pattern and rate of dissipation of pretilachlor and mefenacet in paddy soil at three different depths (0-1, 1-5 and 5-10cm) and in paddy water was the primary objective of the experiments. Half-lives (DT50) of the herbicides were calculated using both the simple first order kinetics (SFOK) and the biphasic first order kinetics (BFOK). The pattern and rate of dissipation of pretilachlor in both soil and water were quite different from that of mefenacet. At the 0-1cm soil layer (oxidative), dissipation of pretilachlor was quite rapid during the first 3 weeks but slowed down afterwards. In case of mefenacet, dissipation was a steady decline until the last sampling day. The DT50 in this layer was between 9 to11 days and 7 to10 days for mefenacet and pretilachlor, respectively. At the lower soil layers (1-5 and 5-10cm; reductive) pretilachlor appeared to leach from the upper layer within the first two weeks and then quickly disappeared afterwards. Faster degradation of pretilachlor was noted in these reductive soil layers. On the other hand, mefenacet dissipation declined steadily at these layers. Also, leaching of mefenacet was not as evident as in pretilachlor. Mefenacet concentration in paddy water peaked over the second to third day and its dissipation was rapid until the fourth week. Dissipation pattern of pretilachlor was a steady curvilinear decline. In paddy water, DT50 was about 3.3 to 4.1 days for mefenacet and 3.0 to 3.6 days for pretilachlor. Calculating the half-life in soil (0-1cm layer) using SFOK appears sufficient for mefenacet while a more complex model such as the BFOK describes that of pretilachlor better. The half-life and dissipation pattern of both herbicides did not vary considerably across years. There was no evidence of residue build-up due to continuous application of the herbicides in the same plots.
Key words: dissipation, half-life, pretilachlor, mefenacet, first-order kinetics, 3 soil layers.
Photosynthetic Electron Transport Inhibitory and Herbicidal Activities of 2-(Fluorinated methyl)-4-benzylamino-6-methyl-1,3,5-triazines
To investigate the substitution effect of the fluorine atom on methyl group, a methyl group of 2-benzylamino-4,6-dimethyl-1,3,5-triazines was replaced with fluoromethyl, difluoromethyl and trifluoromethyl groups and photosynthetic electron transport (PET) inhibitory and herbicidal activities of these (fluorinated methyl)-1,3,5-triazine compounds were evaluated. With increasing the number of fluorine atom of fluorinated methyl group, PET inhibitory activity became higher. Furthermore by introduction of a halogen atom to the 4-position of the benzyl group, PET inhibitory activity was much improved compared to the triazines having an un-substituted benzylamino group. The (fluorinated methyl)-1,3,5-triazine derivatives with higher PET inhibitory activity showed also stronger herbicidal activity in soil and foliar application tests.
Key words: photosynthetic electron transport (PET), PET inhibitory activity, herbicidal activity, 2-(fluorinated methyl)-4-(4-halogenobenzylamino)-6-methyl-1,3,5-triazines.
Synthesis and Herbicidal Activity
of 1-Arylalkyl-3-pyrrolin-2-one Derivatives
A number of 3-pyrrolin-2-one compounds were synthesized and their herbicidal activities were evaluated. Among them 1-[[(1-(benzothiazol-2-yl)-1-methyl]ethyl]-4-methyl-3-phenyl-3-pyrrolin-2-one was found to exhibit high activity to Lindernia pyxidaria, Rotala indica, Elatine triandra, and especially to Echinochloa oryzicola. It also exhibited moderate activity to Monochoria vaginalis, Sagittaria pygmaea and Cyperus serotinus. It was found that the residual effect to Echinochloa oryzicola (barnyardgrass) lasted very long compared to the existing herbicides.
Key words: herbicide, pyrrolin-2-one, benzothiazole, paddy field, barnyardgrass, MI-2826.
Reversible Conversion between Teasterone and Its Ester Conjugates in Lily Cell Cultures
Metabolisms of both teasterone and its 3-myristate were studied using lily cell cultures. Teasterone was metabolized to two ester conjugates, teasterone-3-myristate and teasterone-3-laurate, which have been identified from the lily pollen. On the other hand, teasterone-3-myristate was metabolized to teasterone. The same reversible conversion was suggested during the course of brassinolide biosynthesis in the lily pollen. It was considered that the conjugates are the reversible storage forms during the biosynthesis of brassinolide.
Key words: teasterone, teasterone ester, brassinosteroid, conjugated brassinosteroid, lily cell suspension cultures, metabolism.
Design and Drug Release Properties of Time-Controlled Release Granule Containing Metominostrobin1
A novel controlled drug release system on agrochemicals, time-controlled release granule (TCRG), which is characterized as an active ingredient release with a lag time, has been developed. This TCRG has a five-layered structure composed of core, active ingredient, swelling agent and two water-insoluble polymer membranes. The release profile of TCRG showed that lag time and release rate were optionally controlled by the coated amount of a water-insoluble polymer membrane, polyvinylidene chloride (PVC) and/or by the amount of a swelling agent, acrylate starch.
1Studies on Controlled Release Granule Applied into Seedling Box (Part.3)Key words: controlled release system, lag time, metominostrobin, time-controlled release granule (TCRG).
Effect of Vehicle on Drug Release Profiles of Time-Controlled Release Granule Containing Metominostrobin1
We examined the effect of talc as an vehicle on release profile of time-controlled release granule (TCRG). In this report, TCRG was prepared by coating a water insoluble polymer to the pre-coated granule which consists of a powder blend containing active ingredient, swelling agent and talc. The lag time of metominostrobin release from TCRG was prolonged with increase of talc, a hydrophobic vehicle. We discussed the mechanism in this phenomenon.
1Studies on Controlled Release Granule Applied into Seedling Box (Part.3)Key words: controlled release system, lag time, metominostrobin, time-controlled release granule (TCRG), water infiltration, talc.
Hydrogenated and Dichlorinated N-Phthaloyl-L-threonines and Their Dehydrated Phthalimides with Root Growth-promoting Activity for Rice Seedings
Hydrogenated N-phthaloyl-L-threonines (P-Thrs) and their dehydrated phthalimides (2-phthalimido-2-butenoic acids, P-BTEAs), novel plant growth regulators, were readily synthesized. N-(4,5-Dichlorophthaloyl)-L-threonine and its dehydrated phthalimide also were synthesized. The synthetic P-Thrs and P-BTEAs had strong root growth-promoting activity for rice seedlings. The P-Thr activities were 1.6- to 2.2-fold the control value at 1×10-4M, and the activities of the dehydrated P-BTEAs were a little higher, 2.1- to 2.6-fold the control value at the same concentration. Hydrogenation of the benzene ring of the phthaloyl group reduced root growth-promoting activity. Interestingly, none of the hydrogenated and dichlorinated P-Thrs and P-BTEAs had significant root growth-promoting activity for seedlings of lettuce, Chinese cabbage and black gram, like that of the original N-phthaloyl-L-threonine (P-Thr, 5a) and its dehydrated phthalimide (P-BTEA, 6a).
Key words: N-tetrahydrophthaloyl-L-threonine, 2-(tetrahydrophthalimido)-2-butenoic acids, N-hexahydrophthaloyl-L-threonine, 2-(hexahydrophthalimido)-2-butenoic acids, root growth-promoting activity, plant growth regulator.
Field-Scale Runoff Study for Three Pesticides under Natural Rainfall
Key words: runoff model test in field, volume of runoff water/m2/hr, pesticide residue on soil surface.
An Efficient Method to Identify Oxyfluorfen Resistant Rice Lines by Seed Germination and Mortality of Seedlings
Key words: herbicide resistance, oxyfluorfen, protoporphyrinogen oxidase, rice.
Effect of Fumigants on Soil Microbial
Population and Proliferation of Fusarium oxysporum
Inoculated into Fumigated Soil
Key words: soil microbial population, effect of fumigant, metam-ammonium, chloropicrin, Fusarium oxysporum.
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