• KOREAN JOURNAL OF CROP SCIENCE
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• v.35 no.6
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• pp.512-517
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• 1990

This experiment was conducted to evaluate the tillering behavior of low- and high-tillering rice plants, IR58. a high-tillering cultivar with small panicles showed not only higher tiller number but also earlier tillering, faster tillering rate and longer tillering duration than IR25588. a low-tillering cultivar with large panicles, Tillering ability of IR25588 was only 59% that of IR58, Percent effective tillers was higher in IR25588(85%) than in IR58 (67%), Tillering response to wider spacing was higher in a high-tillering cultivar than in a low-tillering cultivar, Grain yield response to closer spacing (close spacing adaptability) was higher in a low-tillering cultivar than in a high-tillering cultivar.

• Korean Journal of Breeding Science
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• v.41 no.1
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• pp.25-31
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• 2009

This study was conducted in order to breed Japonica salt tolerant rice and select salinity tolerant lines by establishing reliable and practical method of screening voluminous materials. Salinized nutrient solution by adding NaCl was effective compared with the salinized nutrient solution by adding 0.3%, 0.6% and 0.7% of diluted sea water. There was no different visual score of salinity injury between salinization using tap water and distilled water. Seedling salinity tolerant lines between region and order by year were showed very stable and reproducible results, 3~4.2 of visual score at Gyehwado-substation and International Rice Research Institute (IRRI, Philippines) in 2002, 2003 and 2004. Heading date of 6 selected seedling salt tolerant lines showed a range of 16. Aug.~21. Aug. and delayed 2~6 days than that of Donjinbyeo. Percentage of ripened grain and yield of milled rice in 6 lines was lower, 52.2~14.7% and 50~5%, respectively than those of Donjinbyeo.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.39 no.4
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• pp.366-372
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• 1994

The experiments were conducted to evaluate the effect of nitrogen application on the development of small vascular bundle in the rice plants. Two cultivars, IR58, an indica type and Unbong 7, a japonica type were used in this study. The number of small vascular bundles in peduncle of different tillers was increased with the increase of nitrogen level. In the main culm, number of small vascular bundles at higher nitrogen level was increased by 39% in IR58 and 24% in Unbong 7 compared with nitrogen free plot. The main culm had more small vascular bundles in the peduncle and number of small vascular bundle was decreased with later tiller order and tiller development. The number and cross sectional area of small vascular bundles in flag leaf blade and sheath of main culm were increased with increasing levels of nitrogen. The number of small vascular bundles in peduncle was highly correlated with the number of spikelets and grain weight per panicle.

• Korean Journal of Weed Science
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• v.9 no.2
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• pp.108-115
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• 1989

An experiment was carried out at the International Rice Research Institute in 1987 to understand the seed germination and seedling development of rice and Echinochloa species. The percentage germination of rice cultivars(IR64 for lowland-type and UPLRi-5 for upland-type) was extremely high(>90%) regardless of temperature while that of Echinochloa species ranged from 10 to 80% depending on the species. Among these, E. crus-galli ssp. kispidula had the lowest germination with less than 20% at the high temperatures ($30^{\circ}C$, $35^{\circ}C$) and about 45% at the low temperature ($25^{\circ}C$). Original seed weight gradually decreased with time white root and shoot weight increased for both rice and Echinochloa species. However, increase in root and shoot weight did not compensate for the loss of stored carbohydrate during the experimental period. The root of E. glabrescens grew from the seed on the opposite side of the shoot while for rice it grew from the same side of the seed as the shoot. Echinochloa glabrescens had a leaf blade-like expanded first leaf that contained chlorophyll while rice had an incomplete first leaf that had no leaf blade and no chlorophyll. Due to this E. glabrescens could grow independently 2 to 3 days earlier than rice.

• Korean Journal of Weed Science
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• v.10 no.4
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• pp.338-343
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• 1990

The intraspecific susceptibility of twelve Echinochloa colona(L.) Link ecotypes to herbicides was studied at three different stages of growth. At germination and post-germination stage, the Batangas ecotype was most susceptible to both butachlor (N-butoxymethyl-2-chloro-2', 6'-diethylacetanilide) and thiobencarb (S-4-dichlorobenzyldiethylthiocarbamate), whereas the Bukidnon ecotype was the most tolerant. The susceptibility of the ecotypes used was not associated with the seed weight and maturity. When the preemergence herbicides were applied at the 2-leaf stage of the ecotypes, the Nueva Ecija ecotype was least susceptible to butachlor at 1 ppm, but it was most susceptible to thiobencarb. The reverse was exhibited by the Cagayan ecotype. Differential susceptibility of the ecotypes to propanil (3', 4'-dichloropropionanilide) as determined by the necrotic length of the third leaf of 20-day-old seedlings was pronounced in the Camarines Sur, Iloilo, and IRRI (red) ecotypes. However, no necrotic tip appeared in the Cagayan and Batangas ecotypes. The differential responses varied with the type and the concentration of the herbicide studied and the growth stage of the ecotypes.

• Korean Journal of Weed Science
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• v.11 no.2
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• pp.87-99
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• 1991

The experimental growth regulators Hoe78784 and PP-333 significantly reduced lodging in all rices. However, they did not significantly affect the crop vegetative characteristics and yield components, except by decreasing plant height when both growth regulators were applied at booting stage. Grain yield of IR21820-154-3-2-2-3 increased due to reduced lodging when Hoe78784 and PP-333 were applied at booting. These growth regulators increased the thickness and diameter of the culm. Applying CCC did not affect lodging in all test varieties. CCC-treated varieties and the control showed lower number of vascular bundles and culm thickness and diameter of the third and fourth internodes. Hoe78784 and PP-333 significantly reduced internode length from the second to the third internode in short-statured varieties. In tall varieties. reduction extended up to the fourth internode. Culm N content of the varieties did not significantly differ among treatments, except in IR8. Culm P content also did not differ significantly among treatments. although K and Si content was the highest than control when Hoe78784 was applied.

• 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.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 CROP SCIENCE
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• v.37 no.2
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• pp.155-165
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• 1992

Experiments were conducted to determined the development of the vascular bundles in the peduncle of different tillers on its development in order to improve the vascular system and possibly increase grain yield. The development of the vascular bundle in the leaf, stem and panicle is an important aspect of assimilate translocation and differentiation of panicle characters. Two cultivars were used in this study: IR58, an indica type, and Unbong 7, a japonica type. The main culm(M) had more and bigger vascular bundles in the peduncle and those vascular bundle decreased with tiller order and tiller development. In the primary tillers, P1 had more large and small vascular bundles than P5 in both cultivars. IR58 developed more large vascular bundles compared to Unbong 7, but the small vascular bundle in unbong 7 was more than in IR58. The cross sectional area of phloem and xylem in large vascular bundle decreased with tiller order in both cultivar. Larger area of phloem and xylem in the early formed tillers more efficient transport of assimilates. The number of spikelets, the weight of panicle and grain yield per panicle were highest in the main culm followed by the order of their initiation or emergence. The number of primary and secondary branches to be positive associated with the number and area of vascular bundles. Furthermore, the number of vascular bundles in the peduncle was highly correlated with the peduncle thickness which in turn was correlated with the number of primary and secondary branches on the panicle. These results showed tillers that are initiated early and have relatively ation usually have more vascular bundles, larger peduncle, more spikelets spike let filling and ultimately higher yield.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.36 no.2
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• pp.134-142
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• 1991

Since IR8, the first high-yielding rice cultivar characterised by semidwarf and high-tillering, was released in 1966, rice yields during the last two decades have apparently reached a plateau and subsequent efforts to further improve yielding ability have not resulted in visible gains. At this point of time, a new ideotype of rice plant would be necessary to increase grain yield potential. This experiment was conducted to investigate the yield contribution of different tillers within a plant in relation to an ideo type of rice plant. A low-tillering, large panicled IR25588 was compared with a high-tillering, small panicled IR58. Based on spikelet number and grain weight per panicle, the top six panicles in both low- and high-tillering cultivarswere significantly bigger than those in the other panicles. The top six panicles were M, PI, P2, P3, P4 and S1P2 in both cultivars. Their tillers had 100% probability of occurring. The top six tillers were characterised by earlier initiation and heading, longer growth duration, greater leaf area. and heavier culm and total dry weight per tiller. The top six panicles, based on grain weight was mainly due to higher spikelet number per panicle with little differences in 1,000 grain weight and percent fertility. They had also a greater number of high -density grains. The top six panicles were significantly bigger than the rest of the panicles in both low- and high-tilliering types suggesting that a new rice ideotype having six or fewer potential tillers or panicles per paint with 200 to 250 spikelets per panicle (a low-tillering, paicle weight type) may help increase grain yield potential since they have been shown to be superior physio-morphologically to the rest of the tillers.