• Korean Journal of Weed Science
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• v.8 no.1
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• pp.23-27
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• 1988

This experiment was conducted to determine germination ability, life cycle, regrowth ability of Portulaca oleracea L. The newly harvested seeds from P. oleracea flowered before July 15 were able to germinate, but percent germination decreased markedly as the flowering time was later than July 15, showing no germination of seed collected at Sept. 12 which were flowered at August 30, 76.5% of seeds can be germinated in the light as seed stored in room condition for 90 days, but in dark condition, it needed 2 years of seed storage for germination. Low temperature treatment at $2^{\circ}C$ for 5 days enhanced seed germination of P. oleracea in both light and dark conditions. The maximum vagetative growth was observed at 30 to 75 days after seeding. The late seeding time such as July 1 shortened the period of vegetative growth. However, regardless of the seeding times, the first flowering was observed at about 40 days after seeding. Leaf numbers, shoot lengths, fresh and dry weights were greatly affected by the seeding dates, showing that the earlier seedings produced significantly higher shoot length, fresh and dry weight, leaf numbers and branch numbers than those of the late seedings. When all branches were removed on 68 days after seeding, their regrowth ability was 50.3% and cuttaged branches showed 78.1% regrowth as compared to intact plant.

• Korean Journal of Weed Science
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• v.17 no.3
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• pp.295-302
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• 1997

The study conducted to know the effect of growth and yield by different weed control duration using by 'chalok 1 ho', waxy maize, at Suweon in 1995. The emergence of weed and growth and yield of waxy maize on weedy check and 10, 20, 30, 40, 50, 60, 70, 80, and 90 days weed control and whole season weed control during cultivation summrized as follows; 1. Chenopodium album, Echinochoa crus-galli, Persicaria hydropiper and Panicum bisulcatum emerged as major weeds and dominant weed was Chenopodium album. 2. The number of emerged weeds grouped by mophologically ordered broad leaf weeds, grass weeds and sedge weeds. 3. 30 days weed control duration from the sowing effect to silking stage and 40 days weed control duration from the sowing decreased stem length, ear length, ear weight, number of plant, and number of ear. 4. The yield of weedy check, and 10 days weed control from the sowing showed no yield and 20, 30 and 40 days weed control from the sowing decreased to 76, 64 and 33 %, individually. 5. The yield loss of waxy maize on weeds can be prevent by 40 days weed control duration from the sowing.

• Korean Journal of Weed Science
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• v.17 no.1
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• pp.59-65
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• 1997

Bentazon 6-hydroxylase (B6H) and cinnamic acid 4-hydroxylase (CA4H) activities were determined in rice (Oryza sativa L.) microsomes to study methods of enhancing cytochrome P-450 mediated aryl hydroxylation of bentazon by hydoxylase inducing compounds. Pretreating rice seeds with 1,8-naphthalic anhydride at 0.5-2% and fenclorim at 5 and 10 ${\mu}M$ increased B6H and CA4H activities. Treatments of rice seedling with ethanol 2.5% enhanced B6H and CA4H activities, and with phenobarbital at 12 mM enhanced B6H activity, and CA4H activity was enhanced at 2 mM. B6H activity was synergistically enhanced by combined treatments of ethanol 2.5 or 5% and phenobarbital 8 or 12mM and also that of 1,8-naphthalic anhydride 0.5 or 1% and phenobarbital 8 or 12 mM, but CA4H activity was decreased by combined treatment. Five-day-old rice seedlings showed higher B6H and CA4H activities which decreased with seedling age.

• Korean Journal of Weed Science
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• v.16 no.2
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• pp.100-107
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• 1996

Pre- and post-emergent control of Aneilema keisak was investigated in no-till paddy fields. In addition, a pot trial was conducted to determine use rates of the experimental post-emergent herbicide LGC40863. For pre-emergent control, butachlor(1,800g ai/ha), pretilachlor(600g ai/ha), pretilachlor plus pyrazosulfuron(300+18g ai/ha, respectively), thiobencarb plus bensulfuron(2,100+51g ai/ha, respectively), and molinate plus pyrazosulfuron(1,500+21g ai/ha, repectively) were treated at 20 days before seeding. Among the herbicides, molinate plus pyrazosulfuron was the least effective (23% control), while all other herbicides provided excellent(>95%) control of A. keisak. None of these herbicides caused rice phytotoxicity. However, rice yield in the plot treated with molinate plus pyrazosulfuron decreased about 50% due to poor A. keisak control. LGC40863 controlled A. keisak completely, by foliar application, across wide growth stages from the 5- to 15-leaf at 50g ai/ha in pot tests. In the field, treatment of LGC40863(30 to 50g ai/ha) provided >95% control of A. keisak when treated either at 15 days after transplanting or at non-productive tillering stage. Efficacy of 2,4-D and bentazon was insufficient when treated at non-productive tillering stage. These results suggest that, in no-till paddy fields, A. keisak is controlled by pre-emergent application of butachlor, pretilachlor, pretilachlor plus pyrazosulfuron, or thiobencarb plus bensulfuron, and by post-emergent application of LGC40863.

• Korean Journal of Weed Science
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• v.16 no.2
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• pp.122-131
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• 1996

The inhibition characteristics of chlorsulfuron [CHL, 2-chloro-N-[{ (4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino}carbonyl]benzenesulfonamide] and imazaquin [IMA, 2-{4,5-dihydro-4-methyl-4-(1-methy-lethyl)-5-oxo-1H-imidazol-2-yl}-3-quinolinecarboxylic acid] on acetolactate synthase(ALS) activity of corn plants were investigated. CHL and IMA rapidly inhibited ALS activity of corn plants in vitro. Their $I_{50}$ values for ALS activity were 100nM and $5{\mu}M$, respectively, indicating that CHL had 50 times more inhibitory effect on ALS activity than IMA. The first applied herbicide had a dominant inhibitory effect on ALS activity when the two herbicides were applied sequentially. Branched-chain amino acids, valine(Val), leucine(Leu), and isoleucine(Ile) showed a feedback inhibition on ALS activity ; Val or Leu had a more inhibitory effect on ALS activity than Ile. Branchedchain amino acids and CHL or IMA exhibited an additive effect on inhibiting ALS activity. This suggests that branched-chain amino acids inhibit ALS activity by a different mechanisms) from that of CHL or IMA. Apparent ALS activity, which was measured on the basis of the conversion of pyruvate to acetolactate, was decreased by the addition of 2-ketobutyrate into the ALS reaction mixture in a concentration-dependent manner. In addition, kinetic studies revealed that CHL acts as a noncompetitive inhibitor, while IMA acts as an uncompetitive inhibitor to ALS with respect to pyruvate.

• Weed & Turfgrass Science
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• v.6 no.1
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• pp.32-39
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• 2017

This study was carried out to investigate the ACCase inhibiting herbicide resistant Echinochloa oryzicola collected in a Honam rice field and to investigate the control of E. oryzicola in directly seeded paddy rice field. The study result showed that about 44% of the 67 biotypes collected in the rice field in Honam region were resistant to ACCase-inhibiting herbicides. The efficacy of several chemical herbicides on these resistant E. oryzicola biotypes was evaluated according to their application timings. Among herbicides applied 4 days before seeding, pretilachlor, butachlor, oxadiazon, oxadiargyl, oxadiazon+pretilachlor, and fentrazamide+oxadiargyl, provided 95% or higher control of the resistant E. oryzicola biotypes. Among the herbicides applied 10 days after seeding, bromobutide+fentrazamide+imazosulfuron, benzobicyclon+fentrazamide+imazosulfuron, pyrazosulfuron-ethyl+thiobencarb, fentrazamide+imazosulfuron, bromobutide+imazosulfuron+mefenacet and bromobutide+imazosulfuron+pyraclonil provided ${\geq}95%$ control of the weeds. Bromobutide+imazosulfuron+mefenacet and bromobutide+pyrazosulfuron-ethyl+pyriminobac-methyl, applied 15 days after seeding, provided ${\geq}95$ and 90% control of the weeds. Foliar application of cyhalofop-butyl+propanil at 30 days after seeding provided ${\geq}90%$ control of the weeds. In addition, oxaziclomefone provided ${\geq}90%$ control for 40 days after soil application. These results show that E. oryzicola biotypes resistant to ACCase-inhibiting herbicides could be effectively controlled in directly seeded rice in submerged paddy fields using single or tank-mixed chemical herbicides currently available on the market.

• Korean Journal of Weed Science
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• v.14 no.1
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• pp.8-15
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• 1994

The mode of safening action and potency of the 1, 8-naphthalic anhydride(NA) were investigated in corn(Zea mays) and soybean(Glycine max) treated with herbicide bensulfuron[2-{{{{{(4,6-dimethoxy-2-pyrimidinyl)amino}carbonyl}amino}sulfonyl}methyl}benzoic acid] and imazaquin[2-{4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl} 3-quinolinonecarboxylic acid]. Seed dressing with 0.2%(w/w) NA showed successful protection in corn against injury from herbicide bensulfuron and imazaquin but not in soybean. Safening factors of NA against bensulfuron and imazaquin were 10.2 and 5.0, respectively, in corn, while they were both 1.3 in soybean. In vivo, Glutathione-S-transferase(GST) activity of NA-treated corn and soybean increased 1.8-and 1.3-fold, respectively, but the activity was not affected by the herbicides in vitro. Acetolactate synthase(ALS) levels of NA-treated corn was increased 1.3-fold, but not changed in soybean. Tolerance of ALS activity to the herbicides was slightly greater in ALS obtained from NA-treated corn than that from the untreated, whereas the difference was not found in soybean. A significant increase of ACCase due to NA occurred in corn, but not in soybean. The herbicides did not affect in vitro ACCase activity.

• Korean Journal of Weed Science
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• v.12 no.1
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• pp.52-60
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• 1992

There was no significant difference in the final germination percentages(Experiment 1-3) as affected by sunflower root exudates between the control and the treated for the test species. In general(Experiment 1), however, germination onset was delayed the treated bottles. Germination rate was, also, reduced for both radish(Raphanus sativus L.) and rice(Oryza sativa L.). Therefore, the germination index was low in the treated bottles but germination gradually increased with time in the greated bottles in all test species so that the final germination percentages were similar between treatments. The root exudates of sunflower had significant inhibitory effects(Experiment 1-3) on the lengths of the shoots and roots of all the test species. Fresh weight was also significantly reduced in all test species. Sunflower seedlings(Experiment 3) in the treated(with the XAD-4 resin column) were larger and healthier than those in the control (without XAD-4 resin column) because of the removal of allelochemicals. The fresh weight of sunflower seedlings was markedly inhibited by sunflower root exudates. These mean that sunflower probably is an autotoxic crop.

• Korean Journal of Weed Science
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• v.14 no.2
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• pp.107-111
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• 1994

Selective action of root-treated oxyfluorfen [(2-chloro-4-thrifluoromethylphenyl)-3'-ethoxy-4'-nitrophenyl ether] and chlomethoxynil [2, 4-dichlorophenyl-3'-methoxy-4'-nitrophenyl ether] were investigated. Oxyfluorfen showed greater activity to all plant species than chlomethoxynil. $^{14}C$-oxyfluorfen was little metabolized in roots of the plant species and more slowly absorbed than $^{14}C$-chlomethoxynil. These results suggest that herbicidal activity of oxyfluorfen at the site of action is higher than chlomethoxynil. In the tested plants, rice, barnyardgrass, sorghum, and corn were absorbed less of the oxyfluorfen and chlomethoxynil than the broad leaf plant species. However, no clear relationship was observed between a degree of tolerance and absorption and metabolism of both herbicides by the plant species.

• Korean Journal of Weed Science
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• v.13 no.1
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• pp.19-25
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• 1993

This study was conducted to evaluate effect of trinexapac-ethyl{4-(cyclopropyl-${\alpha}$-hydroxy-methylene)-3, 5-dioxocyclohexan carboxylic acid ethyl-ester} for lodging prevention, growth pattern of several organs and yield in machine transplanted rice with 10-day-old seedling. Elongation rate of the second internode affected the most largely by trinexapac-ethyl was 33-52, 35-56 and 42-53% of check in application of 12, 7 and 5days before heading, respectively and, culm elongation was reduced 27-34, 20-29 and 20-25% in application of the same time. Lodging in field was decreased by treatment of trinexapac-ethyl compared with check, Ripened grain ratio and yield were increased about 3-7 and 7-17% by trinexapac-ethyl, respectively.