• Weed & Turfgrass Science
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• v.4 no.4
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• pp.321-329
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• 2015

The present study aimed to evaluate the phytotoxic potential of essential oils. For this purpose, 18 essential oil samples extracted from Korean plants and 64 commercial essential oils were screened for their phytotoxic potential against the seedling growth of Brassica napus L. (rapeseed). Among the 82 samples, 11 commercial oils (cinnamon, citronella, clove, cumin seed, geranium, jasmine, lemongrass, palmarosa, pimento, rose otto and spearmint) strongly inhibited the seedling growth with $GR_{50}$ value < $150{\mu}g\;mL^{-1}$. Major components from these effective essential oils were identified by solid phase microextraction/gas chromatography-mass spectrometry (SPME/GC-MS). GC-MS analyses revealed that the effective samples mainly consist of benzyl benzoate, carvone, citral, citronellol, eugenol, geraniol, D-limonene and terpinene. Subsequently, bioactivity of these individual components was evaluated against the seedling growth of B. napus, Echinochloa crus-galli and Aeschynomene indica. The components from different chemical groups exhibited different potency in inhibiting the seedling growth with varied $GR_{50}$ values ranged from $29{\mu}g\;mL^{-1}$ to > $1000{\mu}g\;mL^{-1}$. In the greenhouse experiment, citral and geraniol completely suppressed the growth of all the tested 10 plants at $100kg\;ha^{-1}$. In conclusion, the individual essential oil components geraniol and citral could be used as natural herbicides for weed management.

• Korean Journal of Plant Resources
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• v.32 no.5
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• pp.543-558
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• 2019

This study was carried out to apply the taxonomic characters to identify and to provide the habitat circumstances for forty one un-introduced environmentally harmful plants in the Korea which have been designated by Ministry of Environment in 2016. We investigated the dried plant specimen from several herbaria and performed field habitat survey in western coast area of United States including California, Oregon and Washington. We suggest the first result for ecological risk discussion, weed risk assessment, taxonomic characters and classification keys for 8 species with the related species - Carduus acanthoides L. (Asteraceae), Carduus tenuiflorus W. Curtis (Asteraceae), Onopordum acanthium L. (Asteraceae), Chromolaena odorata (L.) R.M. King & H. Rob. (Asteraceae), Hydrocotyle ranunculoides L.f. (Apiaceae), Oenanthe pimpinelloides L. (Apiaceae), Ehrharta erecta Lam. (Poaceae), and Paspalum conjugatum P.J. Bergius (Poaceae).

• Korean Journal of Agricultural Science
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• v.50 no.4
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• pp.749-758
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• 2023

An understanding of safety problems pursuant to environmental release of GM (Genetically Modified) crops is considered important. Among the recognized safety problems, the possibilities of weediness and ecosystem invasion are constantly being validated. We herein compared the growth characteristics and germination rate of soybeans formed by hybridization with vitamin A-enhanced soybeans carrying an introduced gene that increases β-carotene content. We also examined overwintering, survival, and weed competitiveness to evaluate hybrid ecological impact on long-term unmanaged cultivatable land. These studies revealed that the hybrid soybeans exhibited intermediate growth characteristics and germination rate compared with the vitamin A-enhanced soybeans and wild soybeans, or exhibited traits similar to those of the maternal strain. Overwintering experiments were conducted by planting seeds at depths of 0, 5, 10, and 20 cm and recovering them after three or five months. After five months, all seeds at depths more than 5 cm lost viability. Among seeds recovered after three months, only wild soybeans retained viability at depths of more than 5 cm. Survival and weed competitiveness were assessed by sowing each type of seed and performing no irrigation, or pest or weed control. Quantitative assessment of numbers of individual soybean plants that appeared in the experimental plot revealed that all plants germinated after sowing, but only wild type plants survived overwintering. These studies suggest that both GM soybeans and hybrid soybeans cannot survive in uncultivated land even if they are released into the environment, which indicates less possibility of ecosystem invasion and weediness.

• Korean Journal of Weed Science
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• v.30 no.3
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• pp.183-190
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• 2010

The objective of this study was to isolate a herbicidally active compound from curly dock (Rumex crispus), a native weed in Korea and to identify its' chemistry. The $GR_{50}$ value of methanol extracts which is determined by a seed bioassay using rapeseed (Brassica napus) seedlings was $935\;{\mu}g\;g^{-1}$. Activity-directed isolation of ethylacetate extract led to the isolation of ECDA fraction with $GR_{50}$ value $53\;{\mu}g\;g^{-1}$. Based on data of GC-MS, $^1H$-NMR and $^{13}C$-NMR, the chemical structure of ECDA was determined as 2H-furo[2,3-H]-[1]-benzopyran-2-one which is known as angelicin. The $GR_{50}$ values of angelicin to barnyardgrass (Echinochloa crus-galli), southern crabgrass (Digitaria ciliaris), and indian jointvetch (Aeschynomene indica) were 426, 66 and $216\;{\mu}g\;g^{-1}$, respectively. Our results suggest that angelicin could be used as a lead compound for the development of new herbicides.

• Korean Journal of Weed Science
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• v.16 no.1
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• pp.8-13
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• 1996

This study was conducted to know the effect of storage period, harvesting time and light condition on dormancy breaking of major weeds. Echinochloa crus-galli, Cyperus serotinus, Aeschynomene indica, Ludwigia prostrata and Bidens tripartita had the 10 or 30% germination ability within 30 days after harvest but scirpus juncoides, Potamogeton distinctus, Aneilema japonica and Monochoria vaginalis had not germination untill 120 days after harvest of seed. C. serotinus and P. hydropiper required strong light for germination but S. juncoides, L. prostrata and B. tripartita showed the less tham 5% germination in the dark condition gerntinator. S. juncoides germination showed negative response in chemical soaking but A. japonica, B. tripartita and L. prostrata showed high germination percentage in Acetone, Chloroform and distilled water soaking during the 10 days after treatment.

• Weed & Turfgrass Science
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• v.5 no.1
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• pp.10-16
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• 2016

Proper actions such as discard, return or manufacturing should be taken to imported plants contaminated with quarantine weeds. Heat-treatment has been used as a processing method in many countries such as U.S., Australia, Canada as well as Korea. This study was carried to find appropriate heat-treatment methods for devitalizing dodder seeds mixed with plant seeds. Two species of dodder seeds and six imported seeds were treated for 1, 5, 10, 15, 30, 45 minutes or 1, 2, 4, 5, 6, 8 hours at the temperatures of $75^{\circ}C$, $80^{\circ}C$, $85^{\circ}C$, $90^{\circ}C$, $95^{\circ}C$, $100^{\circ}C$ and $120^{\circ}C$. According to the study, dodder seeds were devitalized at the conditions of $85^{\circ}C$ for 2 hours, $90^{\circ}C$ for 30 minutes, $95^{\circ}C$ and $100^{\circ}C$ for 15 minutes, $110^{\circ}C$ for 10 minutes and $120^{\circ}C$ for 5 minutes. Meanwhile, seed vigours of Cosmos bipinnatus and Callistephus chinensis had no difference when compared with untreated control at the heat-treatment conditions of $85^{\circ}C$ for 2 hours, $90^{\circ}C$ for 30 minutes.

• Korean Journal of Weed Science
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• v.9 no.2
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• pp.116-122
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• 1989

An experiment was carried out at the International Rice Research Institute in 1987 to understand the seed dormancy and germination habit of rice and several weed species. The germinability of the weed seeds just after harvest was variable depending on the species and ranged from 0 to 72%. Two rice cultivars, IR64(lowland type) and UPLRi-5(upland type) had higher than 95% in germination ability throughout the experimental period due to the fact that the rice seeds came from the harvest of the previous season and dormancy had already been overcome. The length of the storage period needed to overcome dormancy at room temperature($25{\pm}2^{\circ}C$) was about 50 days for Echinochloa glabrescens Munro ex Hook, f., more than 60 days for E. crus-galli ssp. hispidula (Retz.) Honda and 20 days for Ludwigia octovalvis(Jacq.) Raven. Seeds of E. colona(L.) Link, Monochoria vaginalis(Burm. f.) Presl, Fimbristylis miliacea(L.) Vahl and Cyperus difformis L. appeared to have no dormancy. Among the nine species M. vaginalis had the lowest germination of less than 1% throughout the experimental period. However, its seed germinated easily when planted in soil. The low germinability of E. glabrescens, E. crus-galli ssp. hispidula and L. octovalvis just after harvest could be overcome through pretreatment of seeds either by soaking in nitric acid(0.1N) for 1 day or removal of the hull in the grass species, the nitric acid treatment being superior. The results imply that germination habit of weed species varied depending on the species through their differential dormancy period or differential germination strategy.

• Korean Journal of Weed Science
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• v.13 no.1
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• pp.36-43
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• 1993

Differences in community space of weed and rice were investigated among five types of rice (Oryza sativa L.) cultivation. The five types employed were three transplanting cultivations such as conventional hand transplanting, machine transplanting with 30-day-old seedling, and machine transplanting with 10-day-old seedling and two direct-seedlings such as flood direct-seeded rice by pregerminated seed and dry direct-seeded rice by dry seed. The greatest competition between rice and weeds as determined by growth rate of rice was found in between 10 and 11 weeks after transplanting (WAT) and/or seeding, irrespective of cultivation types. Competition injury due to weeds was greater in transplanting with 10-day-old seedling than with 30-day-old seedling. The greatest injury in growth of rice was found in direct-seeded cultivation. In transplanting cultivations space occupation by rice in lower than 80 cm height level was low as compared with that by weeds. Plant heights of dominant weeds such as E. crus-galli and E. kuroguwai were shorter by heading date, but taller after the heading date than those of rice. In direct-seeding community space was mainly occupied by the weeds. The pattern of community structure and competition injury caused by weeds showed a similar tendency obtained on the basis of species distribution, number, and dry weight of the occurred weeds.

• Weed & Turfgrass Science
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• v.2 no.4
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• pp.376-380
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• 2013

This research was carried out to establish a mass-production method and to develop ornamental Gramineae species as cash crops for famers as three species of ornamental grasses were used for seed treatment and plug production. Germination rates of Arundinella hirta were improved to 52.6% by soaking in 4% NaOCl for 60 min and 49.4% with 4% NaOH for 30 min. Germination rates of Panicum virgatum were 20.3% and 22.4% when treated with 4% NaOCl for 10 min and 2% NaOH for 60min treatment, respectively. Pennisetum alopecuroides showed germination rates higher than 98% with both 4% of NaOCl and NaOH for 60 min. When the same size of trays were used, Pennisetum showed faster plug formation in 21 and 30 days with 162 and 40 cell trays, respectively. Arundinella showed a similar trend with Pannicum in completing plug formation, those took 32, 41, and 44 days with the 162, 72, and 40 cell tray, respectively. Plug production was faster with smaller cells; however, total growing period was longer with larger cells in general.

• Weed & Turfgrass Science
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• v.2 no.3
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• pp.274-282
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• 2013

Research was initiated to investigate early germination and establishment characteristics of perennial ryegrass (PR, Lolium perenne L.). An alternative condition was applied in Experiment I with 8-hr light at $25^{\circ}C$ and 16-hr dark at $15^{\circ}C$ (ISTA condition). Experiment II was conducted under $5^{\circ}C$ to $25^{\circ}C$ (natural condition). Significant differences were observed in germination percentage, germination speed and germination peak time. Seed germinating vigor was 66.00 to 93.75% under ISTA and 66.25 to 93.50% under natural conditions. Germination speed, measured as days to germination of 50% through 90%, was much faster with 'Pennant II', 'Brightstar II', 'Sonata' and 'Accent II' under ISTA conditions. But it was faster only with 'Pennant II' and 'Brightstar II' under natural conditions. Germination peak time ranged 1.48 to 5.65 days under ISTA, while 2.17 to 10.63 days under natural conditions. Regardless of growing conditions, the shortest cultivars in peak time were 'Sonata', 'Pennant II', and 'Brightstar II' and the longest one 'Revenge GLX'. Considering germinating vigor, early germination speed and germination peak time, 'Pennant II', 'Brightstar II', 'Sonata' and 'Accent II' were regarded as excellent cultivars under ISTA conditions, while 'Pennant II' and 'Brightstar II' under natural conditions.