Limonium tetragonum is a halophyte grown naturally in the coastal region in South Korea. This study was conducted to investigate the effects of salt concentrations on seed germination, seedling growth, and antioxidant capacity of L. tetragonum. Seeds were collected from naturally grown plants of L. tetragonum and those at full maturity were used in this experiment. All experiments were performed at 0%, 0.5%, 1.0%, or 2.0% of salt concentrations. Seed germination rate was highest as 86% at 20℃ and followed as higher in order of 25℃, 30℃ and 15℃. The germination rate was about 80% at 0% or 0.5% of salt concentration, but it was very low at the salt concentrations higher than 1%. Growth of L. tetragonum seedlings showed no difference in Hoagland solution containing NaCl in the range of 0% to 1.0% and seedlings survived at 2.0% of NaCl concentration. As the salt concentration increased, the content of Na+ in the shoot increased, but that of K+, Ca++, or Mg++ decreased. The antioxidant activity and the content of total polyphenol and total flavonoid in the shoot were similar at 0% and 0.5% of NaCl and were highest at 2.0% of NaCl concentration. In conclusion, performance of seed germination and plant growth of L. tetragonum was highest at 0% and 0.5% of NaCl concentration, and showed no difference in antioxidant activity, total polyphenol contents, and total flavonoid contents at the same salt concentrations.

This research was carried out to investigate the germination and seedling growth characteristics of the halophyte Suaeda asparagoides under various salt concentrations, temperatures, and the presence or absence of light S. asparagoides has a non-endospermic dicotyledonous seed structure that is go stone-shaped with a dark brown color and covered by a star-shaped perianth. Germination within the temperature range 5~40°C varied from 8% to 65%. The highest germination occurred at 15°C. In seeds exposed to salt concentrations in the range 0~400 mM, the highest germination occurred at 0 mM, and the germination progressively decreased as the salt concentration increased. When the perianth of the seed was removed, the germination increased significantly. In the presence or absence of light, germination under white light was 5~20% higher than that under darkness, which varied according to salt concentrations in the range 0~300 mM. The plant growth of S. asparagoides, evaluated by plant height, branch number, root length, fresh weight, and dry weight, was higher in the concentration range 50~100 mM, and it decreased in the other concentrations. In conclusion, the seeds of S. asparagoides showed higher germination in fresh water at low temperature of approximately 15°C under light when the perianth was removed, and the plant growth was higher at salt concentrations of 50~100 mM.

The influence of rainfall during the ripening stage on pre-harvest sprouting, seed viability, and seed quality was investigated in two Korean rice cultivars, Shindongjin and Hopum. When the rainfall was artificially treated in a greenhouse, HP started to pre-harvest sprouting at three days of rainfall treatment (DRT), but Shindongjin did not show pre-harvest sprouting at 40 DAH treatment and just 0.3~0.8% at 50 DAH, which was much lower than 15.3~ 25.8% of Hopum in the same treatment. After harvest, the seed germination of Hopum decreased about 10~25% compared to non-treated seeds, but that of Shindongjin decreased much little rate than that of Hopum. The seed longevity tested by accelerated aging decreased with prolonged rainfall period in both cultivars, but the varietal difference was clear; Shindongjin could withstand longer accelerated aging than Hopum. Shindongjin maintained its germination (>50%) ability after 15 days of accelerated aging regardless of the rainfall treatment period and time, but Hopum dropped below 50% germination ability after only 5 days of accelerated aging. In conclusion, rainfall during the ripening stage induced not only pre-harvest sprouting, but also reduced seed quality and longevity during storage, which varied between two cultivars.

제주피의 발아특성 및 파종 심도에 따른 초기 생육 특성을 조사한 결과를 요약하면 다음과 같다. 가. 사료피 1호 종자는 15℃ 이상에서 발아가 가능하였으며, 10-25℃의 범위에서 20℃에서 가장 높은 발아율을 보였다. 나. 입모율은 담수와 직파에서 모두 20℃에서 가장 높았으며, 담수직파에서 평균 입모율은 5.9%, 건답직파는 70.5%로 나타났다. 다. 사료피 1호의 출아가 가능한 종자의 최대 파종 깊이는 담수직파에서 15, 20, 25℃에서 0.5, 1.8, 1.5 cm, 건답직파는 각각의 온도에서 9.5, 10.0, 9.9 cm로 파종조건과 온도에 따라 변이를 보였다. 라. 사료피 1호는 담수와 건답직파 모두에서 온도와 관계없이 파종심도와 중배축장이 정의상관관계를 보여, 출아에 중배축 신장이 가장 크게 영향을 미치고 있을을 알 수 있다.

본 연구는 벼의 출수 후 일수에 따라 수발아 양상을 조사하고 수발아 피해가 발생할 수 있는 시기를 예측하여 수발아 방제를 위한 기초자료를 얻고자 수행하였으며, 그 결과를 요약하면 다음과 같다. 1. 벼 등숙기간 중 호품벼는 출수 후 20일, 신동진벼는 출수 후 30일부터 수발아 조건이 충족되면 발아가 시작되었으며, 50% 이상의 종자가 발아력을 갖는 시기는 호품벼가 약 35일, 신동진벼가 약 45일이었고, 출수 후 50일에는 두 품종에서 모두 80% 이상의 종자가 발아하였다. 2. 한 이삭 내에서 종자의 위치에 따른 수발아의 순서는 상위부 > 중위부 > 하위부 순으로 나타났으며 지경별로는 2차 지경보다는 1차 지경의 것이 높게 나타났다. 3. 수발아 검정 시 미발아된 종자는 배의 미숙, 종자휴면, 종자의 등숙불량 (불완전립)이 원인인 것으로 판단되었다. 4. 출수 후 30~45일의 등숙중기에 신동진벼는 호품벼보다 종자 휴면성이 높았다.

찰벼 4품종을 두 온도조건(저온; 15℃, 대조; 25℃)에서 왕겨의 유무에 따라(정조 및 현미) 발아특성을 조사한 결과, 현미 발아율은 품종간 차이가 없었으나 정조 발아율은 저온 에서 품종간 차이가 컸다. 종자를 침윤시키면 온도나 왕겨 의 유무에 관계없이 수분이 급격히 증가하다가 30%에서 더 이상 증가하지 않고 정체하는데 이때 정체기에 도달하는 시 간은 온도가 높을수록, 정조보다 현미가 빨랐다. 그러나 수 분정체기에 도달하는 시간은 품종간 차이가 있고 저온에서 차이가 컸다. 수분흡수시간은 발아율, 발아세, 발아속도, 평 균발아일수와 모두 높은 부의 상관을 보여 초기 수분흡수시 간이 빠를수록 발아를 촉진하는 것으로 나타났다. 침윤 24 시간 뒤 guaiacol peroxidase활성은 처리 및 품종간에 큰 차 이를 나타냈으며 발아세와 발아속도와 정의 상관이 있었으 나 최종발아율과는 상관이 낮았다. Catalase활성은 발아율, 발아속도 등과 상관이 매우 낮았으며, 용해성 단백질함량 및 maltose농도도 발아특성과 상관이 낮았다. 종자활력검사 (TTC활력검사)와 표준발아율검사(25℃)에서 발아율이 높 더라도 정조는 저온에서 품종간 발아율의 변이가 커 종자활력검사만으로 발아율을 예측하기 힘들었다. 따라서 초기의 종자활력은 TTC검사와 guaiacol peroxidase활성을 함께 고 려하는 것이 더 정확한 것으로 생각된다. 또 품종간 발아율 의 변이를 줄이고 발아속도를 높혀 균일한 발아를 유도하기 위해서는 적정범위에서 가능한 온도를 높혀 수분흡수를 촉 진시켜야 한다.

2001년 국립식량과학원 인공기상실에서 수경재배로 규산의 시용 여부가 영양생장기 벼의 수분과 질소흡수량에 미치는 효과를 조사하여 규산시용 여부 및 공급된 질소의 형태별 처리에 의한 시험품종들의 수분과 질소이용효율을 산출한 결과는 다음과 같다.1. 처리 67일 후의 벼 건물중은 규산처리 시험구 및NH4+NO3 혼합시용 처리구가 규산을 처리하지 않은시험구 및 NH4 단독시용 처리구보다 유의하게 증가하였음.2. 이앙 후 67일간 조사된 벼의 수분흡수량은 규산처리와 규산 무처리 간의 차이가 없었으나 질소흡수량은규산 무처리에 비해 규산처리구에서 유의하게 증가하였음.3. 질소형태별로는 NH4 단독 시용보다 NH4+NO3 혼합시용에서 규산처리 여부와 관계없이 수분과 질소흡수량이 월등히 많았음.4. 수분이용효율은 규산처리 시험구가 규산을 처리하지않은 시험구에 비해 유의하게 증가하였으나 질소형태별 처리에서는 차이가 없었음.5. 질소형태의 혼합처리가 암모늄태 단독처리보다 질소흡수량은 유의하게 많았으나 질소이용효율은 감소하였음.

Direct-seeding method on dry paddy soil could make rice farming large-scale cultivation and cost-saving, but it has still some problems on poor seedling establishment caused by low temperature and varying sowing depth. This research was carried out to identify weedy rice genetic resources that may help to poor seedling establishment in direct-seeded rice on dry paddy soil in temperate region. The genetic resources screened in this study were 128 accessions that consist of 92 japonica weedy rices, 24 indica weedy rices, and 12 Korean bred cultivars.The weedy rices on average have very superior abilities to emerge form depth than cultivated rice. The germplasm showed that the coleoptile or/and mesocotyl lengths were positively correlated with emergence rate to a high degree. Among the germplasm, WD-3, a japonica weedy rice, evidenced the highest level of emergence with the longest coleoptile and mesocotyl elongation. The emergence ability of WD-3 depending on the burial depth under low temperature condition was confirmed in both the phytotron and the field conditions. WD-3 showed 100% of emergence rate until a burial deptho f 7 cm in the dry soil in the phytotron, and 76.2 % of very high emergence rate in the total layer of paddy field where the seeds were sown from the surface to 10 cm depth. In the emerged plants in the field, the mesocotyl elongation increased with increasing burial depth in a logarithmic fashion, and the coleoptile extension increased exponentially. The total elongation lengths of the mesocotyl and coleoptile were similar with a plant burial depth, which indicated that they could induce the safe emergence of the main leaf of the seedling from the soil to thesurface. Conclusively, the elongation habit of mesocotyl and coleoptile of WD-3 could be one of the important characteristics to develop direct-seeding cultivars.

Over the past few decades Miscanthus has been studied as a potential bioenergy crop in Europe but not much been studied in Korea although Korea has many native Miscanthus species and genetic resources. Because of their features, such as low demands of fertilizers and other agrochemicals, high water use efficiency and high productivity, Miscanthus can be cultivated in marginal lands. However, it is not known how Miscanthus can survive in saline soil and what extent Miscanthus can tolerate salt stress, one of main abiotic stresses in reclaimed lands or dry climates. Therefore, this study was conducted to investigate physiological response of Miscanthus species to salt stress and thus to establish a salt stress threshold. Miscanthus sinensis and M. sacchariflorus showed similar responses to salt stress. Chlorophyll contents, photosynthesis and plant growth were all significantly affected by salt stress. Both species were completely killed at > 100 mM NaCl. The GR50 values estimated by non-linear regression analysis with the logistic model were 116.2 mM and 63.1 mM for M. sinensis and M. sacchariflorus, respectively. These GR50 values can be used as their thresholds of salt stress. Further studies will be conducted to screen salt-tolerant Miscanthus genotypes.

This experiment was carried out to investigate the relationship between grain shapes and ecotypes in Korean native weedy rice. The 111 lines of Korean weedy rice were classified into japonica (91 lines) and indica (20 lines) by RAPD analysis, which was reported in 2005 (Chung and Ahn). The characteristics of grain shape such as grain length, width, thickness, 1,000 grain weight, the ratio of length to width (L/W), the ratio of length to thickness (L/T), and the ratio of width to thickness (W/T) were measured in each ecotype, and their statistical distributions were compared by t test. The mentioned 7 characteristics were significantly different between japonica and indica weedy rice groups, but these could not classify weedy rice accessions into two groups without exceptions according to the classification by RAPD analysis. Out of variables concerning grain shape, the L/W was the highest distinctive to separate ecotypes. A critical point of L/W to divide ecotypes was calculated from the mid point between upper critical limit of japonica and lower critical limit of indica in confidence interval at α=0.05. At critical point of L/W = 2.138, decision error was 2.2% in japonica group, and 5.0% in indica group. Conclusively, the classification of ecotypes by L/W of grain made almost (under 5% error) same result with that by RAPD markers in Korean native weedy rice.

The present study was carried out to assess the genetic diversity, population structure and linkage disequilibrium in Korea. In model-based population, Korean rice germplasm were classified into four subpopulaton designated as indica cultivated, japonica cultivated, indica weedy, and japonica weedy were identified. Pair-wise estimates of FST indicated a different degree of differentiation between the four model-based populations with values ranging from 0.073 (between japonica cultivated and japonica weedy) and 0.474 (between japonica weedy and indica weedy). The indica weedy population appeared to be highly differentiated as compared to other populations. The indica cultivated have the highest gene diversity (0.58), followed by japonica cultivated (0.50), japonica weedy (0.42) and indica weedy (0.35). The total number of specific alleles in indica weedy and japonica weedy populations was 39 alleles (23 markers) and 55 alleles (22 markers), respectively. An average of LD (r2) value of indica weedy and japonica weedy type was higher than two other populations, both in inter- and intra-chromosome, indicating the possible reproductive and geographical isolations of sub-populations in cultivated rice fields.

To understand the heading habit of recently developed 20 Korean rice cultivars, rice plants in a phytotron were exposed to different temperature: 22.5~circC(day~;27~circC/night~;18~circC),~;27.5~circC(day~;32~circC/night~;23~circC) , and day-length conditions: 10, 12, 13, 14, 15 hours. Four rice cultivars (Sobibyeo, Juanbyeo, Ilpumbyeo and Shindongjinbyeo) showed relatively short Basic Vegetative Phase (BVP) of 17 to 18 days, while Dasanbyeo showed the longest (35 days) BVP, compared to other remaining 15 tested cultivars which exhibited 24 to 31 days of BVP. In this experiment, it was tried out to separate the eliminable vegetative phase into photosensitivity and thermo-sensitivity with two different pathways. Many tested cultivars, however, exhibited quite different responses under low temperature and / or long day-length conditions. Especially, Surabyeo and Juanbyeo were the most difficult cultivars to separate into photo- or thermo-sensitivity in that the eliminable vegetative phase of these two cultivars increased greatly only under low temperature (22.5~circC) and long day-length (15 hr.) conditions. Regarding the heading response to temperatures, tested cultivars could be categorized into 2 groups. In 1st group of rice cultivars, the eliminable vegetative phase decreased almost equally as the temperature changed from 20.0~circC~rightarrow22.5~circC~rightarrow25.0~circC~rightarrow27.5~circC . In contrast, the 2nd group of rice cultivars exhibited eliminable vegetative phase slowly decreasing when the temperature changed from 22.5~circC~rightarrow25.0~circC~rightarrow27.5~circC , but rapidly decreasing when the mean temperature changed from 20.0~circC~;to~;22.5~circC . All the cultivars belonged to 2nd group, the heading date would be very delayed if cool summer comes.