• Korean Journal of Weed Science
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• v.5 no.1
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• pp.63-72
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• 1985

To establish the method of integrated weed management in rice nurserybed, phytotoxic factors of herbicide and antidote efficacy were evaluated at the Yeongnam Crop Experiment Station in 1982 and 1984. Seven hundred eighty four research items were carried out as weed control research since 1961. While 65% of these were belonged to rice research, only 6% was attributed to nurserybed among rice research. More herbicidal phytotoxicity exhibited when seedbed was pressed just after seeding than sand covered or uncovered seedbed and also this phytotoxic symptom enhanced by using intact seed compared to pregerminated seed. Rinsing practice of seedbed reduced the phytotoxic effect of butachlor and this effect was more pronounced with the number of rinsing operation increase and at the pressed plot. However, herbicidal efficacy was not significantly decreased by rinsing operation. Growth of rice seedling hardly affected where the herbicide was absorbed through root only compared to absorption from both of root and shoot for pyrazolate, butachlor and thiobencarb. Herbicide antidote `CGA 123'407' completely protected from the phytotoxic effect of pretilachlor without arising any adversal effect in weed control. However, without antidote, pretilachlor showed the most severe phytotoxic symptom among used herbicides.

• Korean Journal of Weed Science
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• v.5 no.1
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• pp.50-55
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• 1985

Effects of weed removal time on maize growth and yield were evaluated in the fields dominated with Poligonum spp., Chenopodium album, Echinochloa crusgalli and Digitaria adsendens from 1982 to 1983 in Suweon. Weed removal treatments were as follows: (a) kept weedfree all season, (b) weeded at 10 day intervals after maize emergence but stopped weeding at 3,5,7,9 leaf stages, (c) weeds initially removed at 3,5,7 and 9 leaf stages and the plots then kept weed free, (d) weeds left all season. Maize kept weed free from maize emergence to 7 leaf stages showed no grain yield reduction due to competition from weeds emerging later, but weeding from emergence to 3 and 5 leaf stages reduced grain yield 46 and 44%, respectively, in 1982 and 29 and 18%, respectively, in 1983. Weeding at 3 leaf stage and thereafter did not influence grain yield but initial weedings at 5, 7 and 9 leaf stages reduced grain yield 10, 36, and 67%, respectively, in 1982 and 14,18, and 21%, respectively, in 1983. Responses of maize to weeding time in the dry matter yields were same as in the grain yields.

• Korean Journal of Weed Science
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• v.8 no.1
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• pp.71-89
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• 1988

This study was conducted to evaluate the effect of a growth retardant, Paclobutrazol on the growth, yield and its components. and physiological traits in peanut cv. Saeddle (early variety) and Nampung (medium variety). The results are summarized as follows : Main stem and branch length of both varieties were remarkably retarded at early growth stage application, but the retardation effect was reduced at late growth stage application. Number of branches was increased remarkably by treating 60ppm at 20days after seedling (DAS) in early variety. Lodging ill medium variety was not observed through growth period when 120ppm of Paclobutrazol was applied while lodging was not appeared between 40 DAS and 80 DAS in early variety. The numbers of riped pods in early variety was increased when application of 120ppm at 40 DAS was made while it was increased as application of 120ppm at 90 DAS in the medium variety. Cercospora leaf spot was reduced by spraying at 40 or 50 DAS regardless of concentration and varieties. Chlorophyll content and photosynthetic activity increased when paclobutrazol was applied during 40-60 DAS in early variety while these were observed at 90 DAS in medium variety. Seed weight tended to increase as paclobutrazol application was delayed. The ratio of pods to seeds was higher at 60ppm-40 DAS in early variety while it was higher at 120ppm-90 DAS in medium variety.

• Korean Journal of Weed Science
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• v.7 no.2
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• pp.144-155
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• 1987

Water extracts of polygonum hydropiper and Polygonum aviculare completely inhibited the germination of lettuce seeds. Methanol extracts from these two species also inhibited the seed germination of lettuce (Lactuca sativa) and Oenothera odorata. Fifteen phenolic acids in total were identified by GLC from P. hydropiper and eighteen from P. aviculare. The most common phenolic acids identified from P. hydropiper were sinapic, salicylic+vanillic and ferulic acid presented in all the fractions. In addition, salicylic+vanillic, tannic+gallic, sinapic, ferulic and p-coumaric acid seemed to be important phenolic compounds in terms of quantity. However, salicylic+vanillic acids were the unique phenolic acids occurred in all the fractions of P. aviculare. The others such as tannic+gallic, sinapic, ferulic, p-coumaric acid, p-cresol and catechol present in large amount appeared also the important phenolic substances influencing allelopathic effects of P. aviculare. Linolenic acid and oxalic acid were the major fatty and organic acids in both plant species, presented in 2.38mg/g and 20.588mg/g in P. hydropiper, 3.70mg/g and 14.288mg/g in P. aviculare, respectively, which seem to be exhibiting allelopathic effects of these plants. Total alkaloids were presented in low amount such as 0.20% in P. hydropiper arid 0.22% in P. aviculare which may not be important elements. Pet. ether extracts were 2.42% in P. hydropiper and 1.65% in P. aviculare, which exhibit another potential for allelopathic effects that need further investigation. Various authentic phenolic compounds at different concentrations inhibited the germination of lettuce seed, indicating that the phenolic substances identified here may be directly related to biologically active substance.

• Korean Journal of Weed Science
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• v.8 no.1
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• pp.64-70
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• 1988

An experiment was carried out to know the effects of paclobutrazol on the lodging related traits and yield of a japonia (Seomjinbyeo) and an indica (Samgangbyeo) rice variety grown at 3 N levels (10, 20, 30 kg/10a) and 3 N split rates [basal + top dressing 15 days after transplanting (DAT) : top dressing 25 days before heading (DBH) was 100 : 0, 80 : 20, and 60 : 40]. Paclobutrazol (3kg/10a of 0.6% G) was applied 15 DBH and lodging related traits were observed 3, 13, 23, and 33 days after heading (DAH). The results obtained summarized as follows. 1. Culm length was increased as N level increased, but decreased by application of paclobutrazol. Culm length was not affected by N split rates in both varieties. 2. Lodging was not occurred at all plots, but lodging index of Seomingbyeo was much greater than that of Samgangbyeo. In both varieties loding index increased up to 23 DAH due to an increase in fresh weight and a decrease in breaking strength and levelled off thereafter due to a decrease in both fresh weight and breaking strength. 3. Culm length of Seomjinbyeo and fresh weight of shoot and culm length of Samgangbyeo were positively correlated with lodging index, but breaking strength was not correlated with lodging index in both varieties during the most of ripening stages. Direct effect of culm length contributing to lodging index was positive and much greater than that of fresh weight and breaking strength in Seomjinbyeo, but in Samganbyeo direct effect of culm length and fresh weight was positive, but that of breaking strength was negative with similar magnitudes. 4. Yield in brown rice of Seomjinbyeo was not affected by N level, but split application of N increased yield. In contrast, yield of Samgangbyeo was increased as N level increased, but yield was not affected by N split rates. Paclobutrazol did not affect yield of rice in Seomjinbyeo, but decreased yield by 5.2% in Samgangbyeo due to a decrease in the number of spikelets per panicle.

• Korean Journal of Weed Science
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• v.8 no.1
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• pp.53-58
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• 1988

This study was carried out to determine effect of butachlor [N.-(buthoxymethyl)-2-chloro-N-(2,6-diethylphenyl) acetamide] and bialaphos [2-amino-4(hydroxy)(methyl) phosphionyl] butyryl-alanylalanine sodium salt on the germination of tobacco seed, induction and growth of callus from tobacco. Further, fatty acids and ammonia content of tobacco calli were determined. Bialaphos had no effect on tobacco seed germination, but the growth of seedling was markedly affected by an application of 10 ppm bialaphos. However, regardless of varieties tested, tobacco seed germination was completely inhibited by $5{\times}10^{-5}M$ of butachlor. At an application of $5{\times}10^{-5}M$ butachlor, tobacco seeds were to some extent germinated and showed further growth. Hyangcho among varieties tested, showed the most tolerant response to butachlor. In induction of callus from various tobacco varieties and their growth, aromatic type of tobacco varieties exhibited the most tolerance against bialaphos. However, no distinct varietal differences were determined in the treatment of butachlor. The major fatty acids identified in tobacco calli were palmitic, oleic and linoleic acid. No marked difference in terms of fatty acids was observed among tobacco varieties used, but it was observed that there was the higher ratio of quantity in unsaturated fatty acids over saturated one, bialaphos treatment accumulated about 9 times higher ammonia content than that of the untreated control, giving an evidence that bialaphos might inhibit glutamine synthetase activity.

• Korean Journal of Weed Science
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• v.18 no.2
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• pp.171-178
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• 1998

Growth response and acetolactate synthase(ALS) activity were examined to determine the resistance of corn cultivars to primisulfuron when primisulfuron and/ or insecticide Terbufos were applied. Pioneer 3571 IR showed resistance to primisulfuron regardless of Terbufos treatment, but Pioneer 3571 was greatly injured with primisulfuron plus Terbufos treatment. Suwon 118 was relatively tolerant to primisulfuron compared to Chalok 2, but crop injury was occurred at both cultivars by primisulfuron plus Terbufos treatment. ALS activity at Pioneer 3751 IR was very high in primisulfuron and/ or Terbufos treatment. Suwon 118 also showed higher ALS activity compared to Pioneer 3751 and Chalok 2, but ALS activities were greatly decreased by primisulfuron plus Terbufos treatment at Suwon 118 and Chalok 2. The $I_{50}$ concentration for 50% inhibition of the ALS enzyme was 10.0, 0.06, 7.75, and 0.04${\mu}M$ for Pioneer 3751 IR, Pioneer 3751, Suwon 118, and Chalok 2, respectively. Consequently, resistance of corn cultivars to primisulfuron was significantly related to ALS activity. Crop injury and lower ALS activity were recognized in susceptible corn cultivars by primisulfuron plus Terbufos treatment.

• Korean Journal of Weed Science
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• v.18 no.2
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• pp.146-153
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• 1998

This experiment was conducted to clarify the characteristics of germination and emergence of Panicum dichotomiflorum which is a noxious weed species in direct-seeded rice field. P. dichotomiflorum was planted with several treatments such as different depths of irrigation to verifiy the ecological habits of seedling emergence and growth. In order to know the germination characteristics, Panicum dichotomiflorum seeds, pretreated with low-temperature($4^{\circ}C$) stratification for breaking the dormancy, were germinated under different temperature regimes and water potentials. Germination rates of P. dichotomiflorum was increased from 0% of dormant seed to 1%, 35% and 44% by stratification for 21, 28 and 42 days, respectively. Two dominant weed species in directseeded rice fields, Echinochloa crus-galli and Panicum dichotomitlorum, showed different germination habit under different temperature regimes. Echinochloa crus-galli showed more higher germination rate than Panicum dichotomiflorum at relatively low temperature regime(20/$10^{\circ}C$). Both species germinated faster at 30/$20^{\circ}C$ than at 20/$10^{\circ}C$. When the water potential was lowered, germination of Panicum dichotomiflorum was reduced more drastically than Echinochloa crus-galli. The critical water potential for germination of P. dichotomiflorum was -0.7MPa but Echinochloa crus-galli was affected slightly by the same water potential. The results showed that Echinochloa crus-galli can germinate under more wide range of soil water potential than Panicum dichotomiflorum. Emergence of P. dichotomiflorum was highly affected by irrigation depth and the level of water table. When the depth of irrigation water was increased, emergence of P. dichotomiflorum was dragged and emergence rate showed significant difference under the irrigation depth deeper than 6cm. The maximum depth of irrigation water for survival of Panicum dichotomiflorum seedling was 9cm.

• Korean Journal of Weed Science
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• v.18 no.2
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• pp.128-135
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• 1998

The experiment was carried out to obtain basic informations on sod culture using water foxtail in apple orchard at Kyeongbuk Provincial RDA in 1996 to 1997. Period of seedling emergence varied with sowing time and accumulative temperature. Sowing at Nov. 25 required longer than 100 days, while it needed only 8 days when water foxtail was sowed at Sep. 20. In a view of accumulative temperature, sowing at March 15 needed $139^{\circ}C$ but it required about $1,000^{\circ}C$ at August 10. This result showed that the seed of water foxtail has strong summer-dormancy in natural condition. Water foxtail had s-shape growth curve during growing season, and growth rate was the highest from March to May in this period. Plant height increased 2 times and 4 times for dry weight from March 20 to April 20. However, growth was decreased by summer depression after May. Major weeds in apple orchard were horseweed, akino-nogeshi and shepherd's-purse. These species were suppressed by the dominance of water foxtail. Water foxtail as a cover plant could be used for a method of weed control instead of herbicide in apple orchard.

• Korean Journal of Weed Science
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• v.12 no.2
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• pp.89-101
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• 1992

In this study, various physiological and biochemical experiments were conducted to know whether the selectivity between rice and barnyardgrass treated with bleaching herbicides containing diphenyl ether compounds was also partly based on their basic physiological proterties such as peroxidation ability, membrane stability or antioxidant system. It seemed to be partly based on the differences of their physiological characteristics that barnyardgrass was commonly more susceptible to most of the bleaching herbicides than rice. The scenescence of intact leaf segment was more rapid in barnyardgrass than in rice, indicating that barnyardgrass is weak at early stage. Also pigment metabolic ability, antioxidant enzyme activities(peroxidase, catalase, superoxide dismutase, glutathione reductase) and antioxidant content (tocopherol, ascorbic acid, glutathione, carotenoids) were lower in barnyardgrass on the basic of fresh weight. However, lipoxygenase activity and the content of unsaturated fatty acid which is vulnerable to oxygen radicals were higher in barnyardgrass, suggesting that barnyardgrass seedling bave a properties easy to be peroxidized. The differences of PPIX (protoporphyrin IX) or carotenoid content, which are the primary substances inducing herbicide activity, were not related to the selectivity between rice and barnyardgrass.