• Korean Journal of Weed Science
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• v.15 no.4
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• pp.247-253
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• 1995

The herbicide butachlor [N-(butoxymethyl)-2-chloro-N-(2,6-di-methylphenyl) acetamide] is widely used by farmers as a tool for weed management of transplanted rice(Oryza sativa L.) in Taiwan. The herbicide did not stop germination of rice and weed seeds, but strongly inhibited the subsequent growth of young shoots and roots. The inhibition was also strong on established seedlings. However, they could recover to normal growth after the herbicide effect disappeared. Butachlor greatly decreased the endogenous indole-3-acetic acid (IAA) but increased the endogenous abscisic acid (ABA) contents of rice seedlings. Addition of lAA into growth medium (Hoagland's solution) partly relieved growth inhibition. Pretreatment of both gibberellic acid ($GA_3$) and IAA 24 hours before butachlor treatment almost completely alleviated the butachlor-interfere with GA and/or IAA metabolism or their action resulting in the growth inhibition of rice. Butachlor was readily absorbed by rice roots. During 24 hours of uptake experiment, 32% of the applied herbicide was absorbed. Pretreatment of the herbicide for 2 days did ncx affect the absorption. Of the absorbed herbicide, 80% remained in roots, only 20% transported into shoots, and more than 50% was metabolized to water soluble substances. Thin-layer chromatographic (TLC) analysis indicated that the Rf value of the most abundant metabolite was butachlor-glutathione conjugate. Rice, barnyardgrass (Echinochloa crus-galli (L.) Beauv.), and monochoria (Monochoria vaginalis Presl) seedlings contained relatively high level of non-protein thiols, while the glutathione S-transferase (GST) activity was found highest in rice, barnyardgrass the next, monochoria the lowest. The difference in GST activity among these species might be related to their sensitivity to butachlor.

• BMB Reports
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• v.33 no.1
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• pp.1-36
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• 2000

Acetohydroxyacid synthase (EC 4.1.3.18) catalyses the first reaction in the pathway for synthesis of the branched-chain amino acids. The enzyme is inhibited by several commercial herbicides and has been subjected to detailed study over the last 20 to 30 years. Here we review the progress that has been made in understanding its structure, regulation, mechanism, and inhibition.

• Korean Journal of Weed Science
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• v.7 no.2
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• pp.200-207
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• 1987

This study was conducted to select and develop herbicide resistant plant through tissue culture. Growth response of seedlings and callis of various rice varieties with Echinochloa species was assessed under the treatment of various rates of butachlor [N-(butoxy methyl)-2-chloro-2', 6'-diethyl acetamide] and simetryne [2,4-bis(ethyl amino)-6-methyl thio-1,3,5-triazine]. Further, succinate dehydrogenase activity was determined in herbicide treated callus to characterize different response of plants to herbicide. Rice variety like Sangpung showed relative resistance in both callus and seedling states against butachlor, indicating maintenance of resistance. However, in the simetryne treatment, the similar response was not observed in callus and seedling state, although there was a great different response among plant materials against simetryne. Rice variety which exhibited resistance in callus and seedling states showed low succinate dehydrogenase inhibition index. Succinate dehydrogenase inhibition index can be used as an important marker characters to differentiate varietal response of plant to herbicide. Rice plant was differentiated from butachlor and simetryne tolerant callus treated at $2.5{\times}10^{-5}$ M is growing under the growth chamber and can be used for resistant source.

• Korean Journal of Environmental Agriculture
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• v.22 no.1
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• pp.36-40
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• 2003

Cyclosulfamuron a herbicide of sulfonylurea type, is a relatively new compound which control broad leaves and perennial weeds in rice field. However, this herbicide has a minor disadvantage of decreasing rice plant growth, especially in early growth stage. Therefore, far introducing this cyclosulfamuron as a herbicide in rice field, it is important to minimize the suppression of early plant growth with maintaining weed control efficacy. This study was conducted to evaluate effects of cyclosulfamuron early plant growth and acetolactate synthase activity of rice (Oryza sativa cv Dongjinbyeo, Hwasungbyeo, Ilpumbyeo). Rice growth was inhibited by cyclosulfamuron in their early growth stage. The concentrations required far 50% inhibition of Dongjinbyeo, Hwasungbyeo and Ilpumbyeo growth were 6.3, 9.2 and 146.mg/kg, respectively. Inhibition effect of cyclosulfamuron on the root elongation was greater than the effect on the shoot growth. Concentrations required far 50% inhibition of acetolactate synthase activity from Dongjinbyeo, Hwasungbyeo, Ilpumbyeo were 42.7, 32.7 and $56.7\;{\mu}M$, respectively.

• Korean Journal of Weed Science
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• v.17 no.1
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• pp.24-30
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• 1997

The influence of nutrients on the phytotoxicity of herbicides (bensulfuron-methyl, pyrazosulfuron-ethyl, imazosulfuron, dimepiperate, and molinate) was investigated in controlled-environment growth chamber with direct-seeded rice (Oryza sativa L. cv. Dongjin). The phytotoxicity of bensulfuron-methyl, pyrazosulfuron-ethyl, and imazosulfuron for rice was greater in nutrient culture than in no-nutrient condition. The root growth of rice applied with these herbicides was more inhibited than the shoot growth. The most severe inhibition was obtained with pyrazosulfuron-ethyl application. The growth inhibition of rice applied by dimepiperate was increased under no-nutrient culture condition. Dimepiperate suppressed more remarkably shoot growth than root. Especially the shoot elongation was much more inhibited than the others. The shoot growth inhibition in rice applied by molinate was severer than the root. The shoot growth was reduced under nutrient culture condition, while the root growth was reduced under no-nutrient culture.

• Korean Journal of Weed Science
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• v.12 no.3
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• pp.261-270
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• 1992

Many herbicides that are applied at the soil before weed emergence inhibit plant growth soon after weed germination occurs. Plant growth has been known as an irreversible increase in size as a result of the processes of cell divison and cell enlargement. Herbicides can influence primary growth in which most new plant tissues emerges from meristmatic region by affecting either or both of these processes. Herbicides which have sites of action during interphase($G_1$, S, $G_2$) of cell cycle and cause a subsequent reduction in the observed frequency of mitotic figures can be classified as an inhibitor of mitotic entry. Those herbicides that affect the mitotic sequence(mitosis) by influencing the development of the spindle apparatus or by influencing new cell plate formation should be classified as causing disruption of the mitotic sequence. Sulfonylureas, imidazolinones, chloroacetamides and some others inhibit plant growth by inhibiting the entry of cell into mitosis. The carbamate herbicides asulam, carbetamide, chlorpropham and propham etc. reported to disrupt the mitotic sequence, especially affecting on spindle function, and the dinitroaniline herbicides trifluralin, nitralin, pendimethalin, dinitramine and oryzalin etc. reported to disrupt the mitotic sequence, particularly causing disappearence of microtubles from treated cells due to inhibition of polymerization process. An inhibition of cell enlargement can be made by membrane demage, metabolic changes within cells, or changes in processes necessary for cell yielding. Several herbicides such as diallate, triallate, alachlor, metolachlor and EPTC etc. reported to inhibit cell enlargement, while 2, 4-D has been known to disrupt cell enlargement. One potential danger inherent in the use of soil acting herbicides is that build-up of residues could occur from year to year. In practice, the sort of build-up that would be disastrous is unikely to occur for substances applied at the correct soil concentration. Crop injury caused by soil applied herbicides can be minimized by (1) following the guidance of safe use of herbicides, particularly correct dose at correct time in right crop, (2) by use of safeners which protect crops against injury without protecting any weed ; interactions between herbicides and safeners(antagonists) at target sites do occur probably from the following mechanisms (1) competition for binding site, (2) circumvention of the target site, and (3) compensation of target site, and another mechanism of safener action can be explained by enhancement of glutathione and glutathione related enzyme activity as shown in the protection of rice from pretilachlor injury by safener fenclorim, (3) development of herbicide resistant crops ; development of herbicide-resistant weed biotypes can be explained by either gene pool theory or selection theory which are two most accepted explanations, and on this basis it is likely to develop herbicide-resistant crops of commercial use. Carry-over problems do occur following repeated use of the same herbicide in an extended period of monocropping, and by errors in initial application which lead to accidental and irregular overdosing, and by climatic influence on rates of loss. These problems are usually related to the marked sensitivity of the particular crops to the specific herbicide residues, e.g. wheat/pronamide, barley/napropamid, sugarbeet/ chlorsulfuron, quinclorac/tomato. Relatively-short-residual product, succeeding culture of insensitive crop to specific herbicide, and greater reliance on postemergence herbicide treatments should be alternatives for farmer practices to prevent these problems.

• Bulletin of the Korean Chemical Society
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• v.29 no.9
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• pp.1823-1826
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• 2008

• KOREAN JOURNAL OF CROP SCIENCE
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• v.47 no.2
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• pp.80-84
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• 2002

In spite of simple and cheap cultivation method, water broadcast-seeded rice demonstrates uneven and unstable seedling establishment per unit land area and requires more herbicide and labor-input for weed control. Three experiments were conducted in a phytotron at 18$^{\circ}C$ to evaluate the adaptability of seed-mat mulching cultivation technologies in water seeded rice for the uniform seedling establishment and the inhibition of weed occurrence without herbicide application. Five different kinds of mat with different mesh sizes and fabric properties were tested. The emergence of rice was the highest in Lawn-mat treatment, being comparable with the control, in which seeds were sown without mat. The Lawn-mat also exhibited the lowest mat tension. Mat tension may influence the emergence of rice. And once it was soaked in water, it didn't maintain its original shape any more. The emergence rate of rice was the lowest in Safer-mat treatment. In Lawn-mat treatment, which was the most effective for rice emergence in the first study, the differences of emergence and seedling establishment of rice depending on the seeding position (upper, beneath, and between mats) treatments were negligible, while they were higher in dry seeds than in pre-germinated seeds treatment. The emergence as affected by the kinds of mat also showed the same trend when tested using barnyard grass. Depending on the kinds of mat, the inhibition effect of weeds was the greatest in Safer-mat and the poorest in Lawn-mat. These results strongly suggest the possibility that the uniform seedling establishment and weed management without chemical could be achieved simultaneously by seed-mat mulching through the combination of effective mat for the emergence of rice and another efficient mat for the inhibition of weed occurrence. This possibility was also tested in the field.

• Journal of Plant Biology
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• v.29 no.3
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• pp.167-173
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• 1986

The effects of varying concentrations and durations of butachlor [N-(bytoxymethyl)-2-chlor-2', 6';-diethylacetanilide] treatment on oat (Avena sativa L.) root cell division were studied. Oats were treated from 0 to 48h with concentration ranging from 1$\times$10-6M to 1$\times$10-3M of butachlor. The highest concentration (1$\times$10-3M) of butachlor caused significant inhibition of cell division after 6h treatment. After 18h treatment, 49% and 66% inhibition of cell division occurred at 1$\times$10-5M and 1$\times$10-4M, respectively, while 16% inhibition of cell division occurred at 1$\times$10-6M concentration at same exposure period. Oat treated with 1$\times$10-5M and 1$\times$10-6M showed 69% and 38% inhibition of cell division after 36h. Increasing herbicide concentration at a specific time increased inhibition of cell division, and increasing the duration of treatment at a specific concentration also increased inhibition of cell division. In most instances the greatest inhibition of cell division occurred between 0 to 18h during 48h treatment. A range of concentration of 1$\times$10-5M to 1$\times$10-3M reduced cell enlargement significantly during 24h incubation period. The 1$\times$10-5M and 1$\times$10-3M caused 34% and 75% inhibition of cell enlargement. It was concluded that butachlor caused the growth inhibition of oats by inhibiting both cell division and cell enlargement.

• BMB Reports
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• v.32 no.4
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• pp.393-398
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• 1999

Acetolactate synthase (ALS) catalyzes the first reaction common to the biosynthesis of L-valine, L-leucine, and L-isoleucine. ALS is the target site of several classes of herbicides, including the sulfonylureas, the imidazolinones, and the triazolopyrimidines. Two forms of ALS (ALS I and ALS II) which have different affinity for Heparin have been separated from etiolated pea seedlings. The substrate saturation curves of both ALS I and ALS II were hyperbolic in contrast to previous reports. The two forms of ALS showed significant differences in their physical and kinetic properties. The values of $K_m$ for ALS I and ALS II were 9.0 mM and 4.8 mM, respectively. The pI values for ALS I and ALS II were determined to be 5.3 and 5.75 by isoelectric focusing, respectively. The native molecular weights for ALS I and ALS II obtained by nondenaturing gel electrophoresis and activity staining were 124 and 244 kDa, respectively. They also exhibited different sensitivity to feedback inhibition by end-product amino acids and inhibition by Cadre, an imidazolinone herbicide.