The effects of UV-B radiation on the seedling growth, carbohydrate metabolism and antioxidants activities of rice (Oryza sativa L.) were investigated under environmentally controlled chamber. Supplementary UV­B radiation reduced dry matter as well as leaf area, there­fore, relative growth rates (RGR) of seedlings were decreased by up to half compared to control. Photosynthetic products such as soluble sugars and starch were rapidly and significantly reduced by within 1 day of enhanced UV-B radiation due to the inhibition and degradation of photosynthetic processes and thylakoid membrane integrity. In our study, nonstructural carbohydrate levels were proved to be a main indicator on UV-B­induced stress. The behavior of SOD, CAT, APX and POD activities was monitored in the leaves of rice seedlings subjected to UV-B radiation. Under UV-B treatments, SOD activity was initially increased, whereas CAT and POD activities were slowly and slightly increased. However, APX activity showed no presumable results with an increase of UV-B dose. In leaves of rice seedlings, supplementary UV-B radiation caused an increase in free putrescine and spermidine, however spermine remained unaltered, although 24-hrs UV-B treatment slightly increased. This result presumes that an excess UV-B dose may induce ethylene biosynthesis (senescence) rather than polyamine biosynthesis (defense).

국제미작연구소(IRRI)의 IRGC와 INGER유전자원에 대한 직파적성을 평가하기 위하여 다양한 직파조건으로 처리된 20개 시험에서 공통으로 공시된 대비품종군(8개 품종) 직파조건에 대한 입모반응을 검토하여 품종들의 유전적 특성으로 평가하고자 시험한 결과를 요약하면; 1. 직파조건에 따른 입모율의 품종, 파종시기, 이들의 상호작용 및 모든 처리간에 통계적인 유의성이 인정되었다. 2. 직파양식, 복토깊이, 파종기 등의 직파조건별 대비품종군의 품종간 입모반응은 거의 같은 경향으로 나타나서 품종의 특성으로 분류할 수 있었다. 3. 직파조건에 따른 평균 입모율의 품종간 차이는 ASD1 > IR50 > IR72 > Taothabi > Uplri5 > CO25 > Dula > Moroberakan순으로 높게 나타났다. 4. 건답직파(파종깊이 25mm, 50mm)에서 파종시기에 따른 입모율의 품종 간 차이는 ASD1과 Moroberakan 품종 간에는 모든 직파조건에서 유의한 차이를 보였으나 다른 품종들은 직파조건에 따라서 유의성 정도가 다소 상이하여 평균 입모율의 순서와 같은 경향이었다.

Rice farmers can save labor and expenses by using expanded rice husk (ERH) as a seedling medium since ERH is lighter and cheaper than other commercial seedling media (CSM). This study was carried out to develop a method for rice seedling cultivation using ERH as a seedling medium. It is suggested that a mixture of 60~% of ERH and 40~% of a CSM could be used as a seedling medium; the planting densities would be 240g per tray for infant seedlings and 200 g for young seedlings; and nitrogen (N) would be applied at a rate of 1g per tray for infant seedlings prior to planting and 2g per tray for young seedlings with division. Great care should be taken to use CO(NH2)2 as an N-source fertilizer. These results would lay a foundation for the rice seedling cultivation with ERH as a medium.

This study was conducted to examine the physiological and biochemical responses against UV-B radiation in the seedling of 15 different rice cultivars, having the different physiological sensitivities. Out of 15 rice cultivars tested, moderate and susceptible groups showed significant decreases in biomass and RGR (relative growth rate). Contents of total chlorophyll were reduced remarkedly by irradiation of UV-B. In all rice cultivars tested, the content of chlorophyll a was strongly decreased, while the contents of chlorophyll b were slightly reduced without showing clear different among three groups and 15 cultivars. Carotenoid content was largely reduced by UV-B radiation, whereas polyamine content was moderately increased. The contents of MDA (malondialdehyde) that reflect the level of lipid peroxidation of cell membranes were clearly increased by UV-B stress, showing higher content in susceptible cultivars than moderate and torelant cultivars. The physiological important parameters highly related to visible injury were leaf color, chlorophyll, carotenoid, and lipid peroxidation, whereas biomass and polyamines were not closely correlated. Based on this results, it was concluded that changes of visible injury and the contents of chlorophyll and MDA could be adequately applied and utilized as physiological indicators to UV-B radiation

The response of dissolved oxygen (DO) concentrations caused significant change in root number, root length, coleoptile length, shoot length and leaf age of seedlings. The genotypic difference in the effect of DO also highly significant (P<0.01) for all of the seedling traits. The number and length of root were extremely inhibited at the condition of 0.39~pm0.09 DO concentration. While the coleoptile elongated markedly in the lowest DO concentrations, the shoot did not develop. The root growth was improved slightly at the 1.39~pm0.27mg L-1 , however, there were no difference among genotypes at these two low DO concentrations. As the DO concentration become higher, the growth of root and shoot was improved remarkably. Root number, root length and shoot length was significantly different between 20~;and~;30~circC in DO rich and normal conditions, the development of those traits were apparently accelerated in high water temperature, however those traits of seedlings in DO deficiency were not different between the two temperatures except for shoot length. On the other hand the coleoptile length was not affected by the stagnant water temperature; it was stimulated by the low DO concentration. The competition of DO was greater as the seedling density was increased in the stagnant water, therefore the seedlings grown under high density have long and white coleoptiles, and the growth of roots and shoots was retarded severely.

This study was conducted to obtain basic information of growth, chlorophyll, and Na+~;and~;K+ content of rice (Oryza sativa L.) seedlings after transplanting in different NaCl conditions. Plants grown in pots for 8 days after germination were grown for 10 days after transplanting in 50 and 100 mM NaCl concentrations. At higher NaCl concentration, plant height, root length, dry weight and chlorophyll content were reduced with NaCl stress. Among rice cultivars, the shoot dry weight of Gancheokbyeo, Janganbyeo and Hwasungbyeo, and the root dry weight of Janganbyeo, Gancheokbyeo and Juanbyeo showed relatively low reduction compared to the other rice cultivars at 100 mM NaCl stress. The Na+ content in seedling rapidly increased with the increase of NaCl concentration but K+ contents decreased. There was a significant relationship between Na+ content and shoot and root dry weight after transplanting rice seedlings to saline conditions. The shoot and root dry weight showed highly negative relationship with the Na+/K+ ratio in saline conditions.

In order to investigate low molecular antioxidants synthesized by enhanced UV-B radiation, we used the seedlings of two rice varieties. Woonjangbyeo, UV-tolerant, and Hwajoongbyeo, UV-susceptible, were subjected under supplemental UV-B irradiation. When rice seedlings were irradiated with UV light for short period, biosynthesis of total phenolic compound, ascorbate and glutathione were momently reduced. With an increase of UV-B radiation, however, those were slightly synthesized. The content of lipid peroxides in UV-challenged rice leaves was considerably increased after 12 hrs of UV-B treatment. Lipoxygenase activity under supplemental UV-B radiation was differently responded on rice varieties.

본 연구는 벼 종자의 파종 후 발아, 유묘출현 및 생육 초기에 가하여지는 광질처리가 유묘 출현, 생장, 형태, 엽록소 함량 및 광합성율에 미치는 영향을 조사하여 벼의 육묘에 이용되고 있는 부직포의 색상을 전환할 필요가 있는가를 검토하고자 실시하였으며 그 결과를 요약하면 다음과 같다. 1. 파종 직후에 가하여지는 광질처리에서 유묘출현율은 조사일 모두 일미벼에서는 광질처리간 차이가 없었다. 그러나 동진벼와 대산벼에서는 원적색광 처리에서 가장 낮았으며, 청색광과 적색광간에는 차이가 거의 없었다. 2. 파종 직후에 가하여지는 광질처리로 인하여 원적색광 처리에서 초장과 엽장이 가장 짧았던 반면, 적색광은 뿌리수를 증대시켰다. 3. 파종 직후에 가하여지는 광질처리로부터 지상부 건물중은 청색광 처리에서, 뿌리의 건물중은 적색광 처리에서 가장 많았던 반면, 지상부 및 뿌리 건물중 모두 원적색광에서 가장 적었다. 4. 엽록소 함량과 광합성율 모두 품종간에는 일정한 경향이 없었으나, 광질처리에서는 이들 모두 적색광에서 가장 높고, 청색광, 원적색광 순으로 감소하였다.

To identify the new source of breeding materials for rice salt tolerance, the salinity tolerance of thirty-four varieties was evaluated under 0.5% saline condition at seedling stage. The salinity score showed highly significant correlations to dry weight and dead leaf ratio. The tested varieties were classified into three groups by visual score, reduction ratio of dry weight, and dead leaf ratio. Eighteen varieties were classified as the highly tolerant group (salinity scores of 1.3-3.7), seven varieties were fallen into the tolerant group (salinity scores of 4.2-5.8), and others were susceptible (salinity scores of 6.7-9.0). In highly tolerant group, most indica varieties including Getu, Dikwee and Kuatic Putic, didn't exsert a panicle under the Korean climate. But six varieties, Xiangcho V, Annapuruna, HP 3319-2wx-6-3-1, Giza 175, and GZ 2447-S-17, GZ 4255-6-3 were suitable to the Korean climate, and their heading date (6-16, August) and culm length (65-78㎝) were similar to the Korean varieties. Accordingly, these varieties can be utilized as crossing materials for the salt tolerance in japonica rice.

Four different rice varieties, Sindongjinbyeo, Dongjin #1, Saegyehwabyeo, and Iksan 467, were transplanted under three different nitrogen levels and two different seedling numbers per hill to obtain basic information on panicle traits under different cultural conditions and to propose the ideal panicle structure in Japonica rice. Sindongjinbyeo and Iksan 467 were characterized by more primary rachis branches (PRBs) per panicle and more grains on PRB than other cultivars. The two varieties also had fewer secondary rachis branches (SRBs) per PRB and fewer grains on SRB per PRB. These characteristics, consequently, resulted in higher ripened grain rate, contrary to that of Dongjin #1 and Saegyehwabyeo. In the correlation coefficient analysis, PRB number per panicle and grain number on PRB per panicle were positively correlated with ripened grain rate, while SRB number per panicle, number of grains on SRB per panicle, SRB number per PRB, number of grains on SRB per PRB and grain number per panicle were negatively correlated with ripened grain rate. Therefore, the number of grains on PRB per panicle, SRB number per PRB and the number of grains on SRB per PRB were the appropriate criteria for determining and achieving higher ripened grain rate in rice. High ripened grain rate over 90% was obtainable with over 12.5 PRBs per panicle and 63 grains on PRB per panicle, and with under 1.7 SRBs per PRB, 5 grains on SRB per PRB, 130 grains per panicle, and 14 panicles per hill. The study recommended that for over 90% high ripened grain rate, the critical limiting factors should be under 2 SRBs per PRB, 6 grains per PRB, and 130 grains per panicle, irrespective of the PRB number per panicle and the number of grains on PRB.

The study of this experiment is focused on labor saving of healthy rice seedling production using PSF (polypropylene spunbonded fabrics) as thermal protection material. Several factors such as different compositions of nursery soil and PSF materials were tested to produce healthy rice seedlings. The inner thermal protection material in PE film (polyethylene film) showed 0.9-1.7~circC higher than that of PSF 40-100 ~textrmgm-2 . The light transmittance-ratio also showed similar trends. It is considered that the appropriate PSF material density was 40 gm~textrmgm-2 in accordance with economic values and healthy rice seedlings. Plant height and dry weight according to various nursery soil showed the rang-es of 8.5-14.2cm and 5.5-10.0mg, respectively. In composition of nursery soil, artificial soil combined with paddy soil was effective in producing healthy seedling for rice seedling production. The total sugar content also showed the difference between PSF 40, 60 ~textrmgm-2 PE film (0.43-0.52mg FW ~textrmg-1 ) and PSF 80, 100 ~textrmgm-2 (0.28-0.35mg FW ~textrmg-1 ) and it showed the same tendency among varieties as well as various nursery soil. These results demonstrate that PSF 40 ~textrmgm-2 economically affordable, and can be recommended as thermal protection material for producing good healthy rice seedling.

본 연구는 벼 생산비중 육묘에 투입되는 비용을 경감시키고 이앙의 효율을 제고하기 위하여 기계이앙용 상자육묘시 상토를 전혀 사용하지 않고 물과 양액만으로 묘를 생산하는 수경육묘법을 개발하고자 하였다. 이를 위해 적절한 양액의 선발과 공급횟수를 구명하고자 시험을 실시하였던 바 그 결과를 요약하면 다음과 같다. 1. Yoshida액과 원시표준액간의 육묘후 묘소질은 두 양액간에 차이가 없었으나, 양액 공급횟수는 1회에서 3회로 증가할수록 초장, 엽수, 건물중이 증가되었다. 2.육묘후 인장강도는 Yoshida액이 원시표준액에 비해 높았고, 양액 공급횟수는 증가할수록 낮아졌다. 3. 경엽의 무기성분 함량은 공급양액 종류에 관계없이 N, P, K 함량은 증가하였으나 Ca와 Mg는 뚜렷한 경향이 없었다. 4. 수경묘에 축적된 무기성분량은 양액종류에 관계없이 공급횟수가 많을수록 N, P와 K의 축적량은 증가되었으며, 그 정도는 N에서 가장 컸다. 5. 수경묘에 축적된 N에 대한 다른 무기성분 비을중 P/N과 Mg/N의 비율은 원시표준액에 비해 Yoshida액에서 놀았고, 공급횟수가 증가할수록 K/N 비율이 증가되었다. 6. 양액의 이용효율은 N의 경우 공급횟수에 관계없이 비슷하였으나, P, K, Ca와 Mg는 파종 5일후 1회 공급 시 높았다.

벼 생산비중 육묘에 투입되는 비용을 경감시키고 이앙의 효율을 제고하기 위하여, 기계이앙용 상자육묘시 상토를 전혀 사용하지 않고 물과 양액만으로 묘를 생산하는 수경육묘법을 개발하고자 양액의 환경중 적정 EC설정에 대한 시험을 실시하였던 바 그 결과를 요약하면 다음과 같다. 1. 초기 설정 EC 농도는 육묘시기에 관계없이 3.0 dS/m 까지는 초장과 건물중이 증가되었으나 EC 3.0 dS/m 이상에서는 차이가 없었다. 2. 육묘후 폐양액의 EC는 초기 설정 3.0 dS/m은 1.1 dS/m로 낮아졌던 만면, 4.0과 5.0 dS/m에서는 1.5-2.4 dS/m로 높게 나타났다. 3. 경엽의 무기성분 함량은 양액의 EC가 높을수록 N, P 및 K 함량은 증가하였는데 그 중 K의 증가율이 가장 높았고. Ca는 반대로 감소하였다. 4. 수경묘에 축적된 무기성분량 중 N과 P는 양액의 EC 2.0 또는 3.0 dS/m를 기점으로 증가도가 둔화되었다. 5. 초기 EC 설정농도가 높을수록 수경묘에 축적된 N에 대한 다른 무기성분 비율 중 K/N 비율은 EC가 높을수록 증가한 반면, Ca/N 비율은 만대로 감소하였다. 6. 공급된 양액의 무기성분 중 N, P 및 K의 이용효율은 EC 2.0과 3.0 dS/m에서 높았으나, Ca와 Mg의 이용효율은 EC가 높을수록 감소하였다.

팽화왕겨'를 이용한 벼 육묘의 가능성을 제시하고자 실험을 수행하였다. 시판상토와 '팽화왕겨'의 성분분석 결과 산도와 유기물 함량은 '팽화왕겨'가 '부농상토' 보다 높았고, 유효인산,질산태 및 암모니아태 질소는 '부농상토'에서 높았다. 상토 종류에 따른 15일묘의 초장은 '부농상토'에서 22.8㎝로 가장 길었고 '팽화왕겨'만을 이용했을 때 12.8㎝로 가장 짧았다. 염수는 상토종류 간에 큰 차이가 없었으며, 묘충실도와 매트형성 정도는 '팽화왕겨'를 깔고 시판상토를 복토한 것에서 가장 양호한 것으로 나타났다 15일묘의 초장은 공시 품종 모두 '부농상토'에서 컸으나, 묘충실도와 매트형성은 '팽화왕겨'를 깔고 '부농상토'를 복토한 것에서 오히려 양호한 것으로 나타났다. 시판상토의 파종후 상자당 무게는 4.8㎏이였으나 '팽화왕겨'를 깔고 시판상토를 복토한 것은 3.5㎏에 불과하였다.

Molecular markers were used to map and characterize quantitative trait loci (QTLs) for traits related to cold tolerance in an intrasubspecif ic backcross population of r ice. The parents of the cross were a cold susceptible Tongil-type cultivar 'Milyang23