• KOREAN JOURNAL OF CROP SCIENCE
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• v.28 no.1
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• pp.41-57
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• 1983

The effect of temperature 'during the reduction division stage on the Indica-Japonica rice varieties were studied in artificial temperature-controlled cabinets (Bioclimatic Laboratory). Varieties used were indica-japonica crosses (Suweon 264, Suweon 258, Milyang 29), indica (IR36, Lengkwang) and japonica rice (Jin-heung). The results obtained from this study are summarized as follows. The most sensitive stage to low temperature, the tetrad stage, was observed in each variety with the following auricle distance: Jinheung, -12cm; IR36, -3cm; Suweon264, -9cm; Suweon258, -3cm; Milyang29, -6cm and Lengkwang, +1cm. The tetrad stage occured when the palea elongation was about 50 to 60% of the final palea length at flowering stage in all varieties. The percentage of degenerated spikelets at tetrad as influenced by low-temperature treatment was very low in Jinheung and Lengkwang, but very high in IR36. In indica-japonica crosses only the 7-days treatments had a very high percentage. Between the 4-day and 7-day treatments as well as among all varieties, clear differences were observed in the low temperature induced sterility of 'special spikelets' (upper position grains at tetrad). In the 7-day treatments except in Lengkwang, all varieties showed very high sterility. It appears that the treatments is over the critical limit for treatment. However in the 4-day treatments, the intervarietal differences in sterility were very clear. In Jinheung, sterility was 46.8%; IR36, 67.6%; Suweon264, 60.9%, Milyang29, 62.2%; Lengkwang, 27.8%. A close relationship was observed between fertility and auricle distance. The lowest fertility of special spikelets was at the tetrad stage and the first contraction phase. Before and after the stage there was an increase in fertility. The palea length elongated nearly in a straight line from the spikelet formation stage to flowering. And there was a high correlation between palea length and auricle distance. distance.

• Korean Journal of Ecology and Environment
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• v.37 no.1 s.106
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• pp.70-77
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• 2004

In order to the epilithic diatom community and an assessment of water quality with diatom assemblage index of organic water pollution (DAlpo) in the middle reaches of the Nakdong River, the samples were collected from nine sampling stations on May, July, September, November, 2002 and on January 2003. A total 162 taxa was identified from this study, which were classified into 139 species and 23 varieties belonging to 33 genera. Achnanthes minutissima, Navicula subminuscula, Navicula viridula var. rostellata, Nitzschia inconspicua and Nitzschia palea indentified in every stations and examination for the whole periods. A total of 12 taxa was dominant species at any station at least one more times. In this study, average DAlpo was 30.90 ${\sim}$ 44.61 and the saprobic level was estimated ${\beta}$-mesosaprobic in the middle reaches of the Nakdong River.

• Journal of Microbiology and Biotechnology
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• v.30 no.7
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• pp.1072-1081
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• 2020

Screening suitable strains with high temperature adaptability is of great importance for reducing the cost of temperature control in microalgae cultivation, especially in summer. To obtain high temperature-tolerant diatoms, water samples were collected in summer from 7 different regions of China across the Northeast, North and East. A total of 731 water samples was collected and from them 131 diatom strains were isolated and identified based on the 18S rRNA sequences. Forty-nine strains out of the 131 diatoms could survive at 30℃, and 6 strains with relatively high biomass and lipid content at high temperature were selected and were found to be able to grow at 35℃. Cyclotella sp. HB162 had the highest dry biomass of 0.46 g/l and relatively high triacylglycerol (TAG) content of 237.4 mg/g dry biomass. The highest TAG content of 246.4 mg/g dry biomass was obtained in Fistulifera sp. HB236, while Nitzschia palea HB170 had high dry biomass (0.33 g/l) but relatively low TAG content (105.9 mg/g dry biomass). N. palea HB170 and Fistulifera sp. HB236 presented relatively stable growth rates and lipid yields under fluctuating temperatures ranging from 28 to 35℃, while Cyclotella HB162 maintained high lipid yield at temperatures below 25℃. The percentage of saturated fatty acids and monounsaturated fatty acids in all the 6 strains was 84-91% in total lipids and 90-94% in TAGs, which makes them the ideal feedstock for biodiesel.

• Journal of Korean Society on Water Environment
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• v.33 no.4
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• pp.424-433
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• 2017

The purpose of this study is to understand the changes on species composition of the epilithic diatoms and the appearance of morphological abnormalities in the upper region of the Nakdong River where heavy metal inflow is observed. The samples were collected once a week for a month of September 2016 from selecting 7 sampling stations. The heavy metals of cadmium (Cd) and arsenic (As) were not detected during the survey period, but zinc (Zn) was detected in st.4 - st.6 with the range of $0.015{\sim}0.188mg\;L^{-1}$. Metal sensitive species such as Achnanthes convergens, Cocconeis placentula, Cocconeis placentula var. euglypta, Cocconeis placentula var. lineata showed high dominance in st.1 - st.3, st.7. However, metal tolerant species such as Nitzschia palea, Achnanthes minutissima showed high dominance in st.4 - st.6. It is concluded that heavy metal inflow directly affects the changes in species composition of epilithic diatoms. As a result of CCA, the characteristics of the sampling sites were divided into 3 groups. Group 1 was represented the non-detected Zn sites with C. placentula, C. placentula var. euglypta, C. placentula var. lineata. Group 2 was showed the detected Zn sites with Navicula minima and Nitzschia palea. Group 3 was included st.3 - st.7 on 4th week that was stabilized the community structure. Total 8 taxa of abnormal frustules observed. This occurrence of abnormal frustules reflected the temporal and quantitative indicators of heavy metal pollution, in particular, it was confirmed that genus Fragilaria, which has a high abnormality according to heavy metal pollution, can be used as an indicator species.

• Korean Journal of Ecology and Environment
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• v.43 no.1
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• pp.91-102
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• 2010

Water quality and epiphytic diatom on the submerged stems of reed (Phragmites communis), which occupy 90% of the Donghwa wetland macrophytes were monthly monitored at three points such as inflow stream, high- and low-level wetlands, and outflow stream between March and October, 2005. 1) A diverse and high density of diatom species observed in the cold-season, especially Nitzschia palea and Nitzschia amphibia dominated the diatom community without wetlands. 2) High DAIpo and TDI indices were measured over the sampling periods and stations, regardless of nitrogen increase and phosphorus increase through the wetlands. 3) Higher density of diatom species in high wetland than low wetlands was attributed in the enough nutrients and light penetration by low growth of reed. Therefore, epiphytic diatom of reed stem in Donghwa wetland, where high nutrients released from the sediment and reed debris after the death of macrophytes, flourished with low canopy of low reed vegetation.

• Korean Journal of Ecology and Environment
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• v.46 no.4
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• pp.551-560
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• 2013

Environmental factors and epilithic diatom communities in the lower streams near the harbor region of South Korean peninsula were examined during no monsoon period in May 2013. The sampling of water and epilithic diatoms was conducted at both streams, 19 regulated streams (RS) that there are one or several dams constructed in the river system, and 19 un-regulated streams (US) that there are no dams within the river. A cluster analysis based on the number of species and abundance of epilithic diatoms through the stations, divided into three groups such as groups I (mainly US), II (mixed with US and RS) and III (mainly RS), respectively. Group I showed that water quality is good and high diversity of diatom, while Group II and III was water quality is relatively poor, but not differed in biomass of diatom from Group I. In addition, Group II that had high conductivity, nitrogen and phosphorus, was the lowest in diatom diversity among them. Dominant species were Nitzschia palea (17%) and Navicula seminuloides (11%) in Group I, Nitzschia inconspicua (19%) and Navicula perminuta (9%) in Group II, and Nitzschia inconspicua (15%) and Nitzschia palea (14%) in Group III, respectively. These taxa were widely distributed in brackish water, and not closely related with specific water quality, like eutrophic water. However, the groups II and III belonged to RS, had not only little biomass, but bad water quality such as high concentrations of nutrient and chlorophyll-a. Therefore, to determine the effect of dam construction on the lower water ecosystem, the planktonic algae, which can occur algal bloom in the estuary, also was considered to be a parallel investigation.

• Journal of Korean Society on Water Environment
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• v.25 no.4
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• pp.606-614
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• 2009

To evaluate the biological water quality, diatom-based biological indices (DAIpo and TDI) were examined in the Sum-River and the Dal-stream. Having BOD concentrations below $2mg{\cdot}L^{-1}$ in most sites, water quality of both rivers was good. The DAIpo and TDI values ranged from 29.8 to 91.4 and from 38.7 to 93.0 respectively. From the biological water quality assessment, DAIpo and TDI for both rivers displayed fair to fairly poor water quality levels. However, the two indices showed more polluted conditions than expected from the BOD vlaues. In addition, DAIpo, having wider range of differences, appears to be more sensitive to the change in water quality when compared to TDI values. Statistical analysis using principal component analysis showed that Nitzschia palea and Diatoma vulgare might not be the appropriate indicators due to their low correlations with other indicators.

• 한국균학회소식:학술대회논문집
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• 2014.10a
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• pp.25-25
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• 2014

Three species of Fusarium, F. fujikuroi, F. verticillioides and F. proliferatum, are known to be associated with bakanae disease of rice [1, 2]. F. fujikuroi infects rice flowers and survive in endosperm and embryo of the seeds. Infected seed is an important source of primary inoculum of pathogens [3]. Seeds of rice (Oryza sativa cv. Boramchan) collected from bakanae-infected field were found to be 96% infected with Fusarium sp., 52% with F. fujikuroi, 42% with F. verticillioides, and 12% with F. proliferatum as determined by incubation method and species-specific PCR assays. F. fujikuroi was detected at lemma/palea, endosperm and embryo whereas F. verticillioides and F. proliferatum were recovered only from lemma/palea by means of component plating test. Seed disinfection methods have been developed to control bakanae disease and prochloraz has been most widely used for rice seeds. Two chemicals formulated with prochloraz (PC 1) and prochloraz + hexaconazole (PC 2) that inhibit biosynthesis of ergosterol strongly reduced the incidence of Fusarium spp. on selective media to 4.7% and 2.0%, respectively. Disease symptoms of rice seedlings in nursery soil were alleviated by chemical treatment; seedlings with elongated leaves or wide angle between leaf and stem were strikingly reduced from 15.6 to 3.2% (PC 1) and 0 (PC 2), stem rots were reduced from 56.9 to 26.2% (PC 1) and 32.1% (PC 2), and normal seedling increased from 0.4 to 13.3% (PC 2). Prochloraz has some disadvantages and risks such as the occurrence of tolerant pathogens [4] and effects on the sterol synthesis in animals and humans [5]. For these reasons, it is necessary to develop new disinfection method that do not induce fungal tolerance and are safe to humans and animals. Chlorine dioxide ($ClO_2$), that is less toxic, produces no harmful byproducts, and has high oxidizing power, has been reported to be effective at disinfection of several phytopathogenic fungi including Colletotrichum spp. and Alternaria spp. [6]. Gaseous $ClO_2$ applied to rice seeds at a concentration of 20 ppm strongly suppressed mycelial growth of Fusarium fujikuroi, F. verticillioides and F. proliferatum. The incidence of Fusarium spp. in dry seed with 8.7% seed moisture content (SMC) tended to decrease as the concentration of $ClO_2$ increased from 20 to 40 ppm. Applying 40 ppm $ClO_2$ at 90% relative humidity, incidence was reduced to 5.3% and resulted in significant reduction of disease symptoms on MS media. In nursery soil, stem rot was reduced from 56.9 to 15.4% and the number of normal seedlings increased from 0.4 to 25.5%. With water-soaked seeds (33.1% SMC) holding moisture in the endosperm and embryo, the effectiveness of disinfection using $ClO_2$ increased, even when treated with only 20 ppm for four hours. This suggests that moisture was a key element for action of $ClO_2$. Removal of the palea and lemma from seeds significantly decreased the incidence of Fusarium spp. to 3.0%. Seed germination appeared to decrease slightly by water-soaking at $30^{\circ}C$ because of increased SMC and by physical damage of embryos from hulling. These results indicate that the use of gaseous $ClO_2$ was effective as a means to disinfect rice seeds infected with Fusarium spp. and that moisture around the pathogens in the seed was an important factor for the action of $ClO_2$. Further investigations should be conducted to ascertain the best conditions for complete disinfection of Fusarium spp. that infect deep site of rice seeds.

• Korean Journal of Ecology and Environment
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• v.39 no.3 s.117
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• pp.402-412
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• 2006

The Shihwa constructed wetland was established to treat the severely polluted water from Banwoul, Donghwa and Samhwa streams. This study was focused on investigating the dynamics of epiphytic algal communities on reed (Phragmites communis) planting area at 5 stations from October 2001 to June 2002. The concentration of total nitrogen and phosphorus of inlet stations from the streams were decreased after flowing through the wetland. However, the TN : TP ratios at all stations were slightly over 16 indicating that the total phosphorus may play some role as a limitation factor. Epiphytic algae on the reed were total 329 taxa which were composed of 295 species, 13 varieties, 3 forma and 18 unidentified species. The species numbers were recorded in the order of Chlorophyceae-Bacillariophyceae-Cyanophyceae-Euglenophyceae-Chrysophyceae. The relative percentage showed a seasonal variation from Cyanophyceae to Bacillariophyceae and to Chlorophyceae. The biomass of epiphytic algae measured by chlorophyll-a concentration ranged from 0.6 to $36.4\;{\mu}g\;cm^{-2}$. Dominant species were 16 taxa which were Lyngbya angusta of Cyanophyceae in the early investigation, and were changed to Stigeoclonium lubricum of Chlorophyceae, and Nitzschia palea of Bacillariophyceae etc. in the late. Species number, standing crops and chlorophyll-a concentrations of epiphytic algae showed higher values at the inlet stations than the stations after flowing through the wetland.

• Korean Journal of Ecology and Environment
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• v.43 no.2
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• pp.232-241
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• 2010

Epilithic diatom communities and water quality were monitored to evaluate the ecological impact of the inflow of Wonju-stream passing through the urban area in the Seom River Watershed. We selected the 14 sampling stations (5 main stream sites and 9 tributary sites), and collected diatom and water samples between October 2007 and September 2008, on the seasonal basis. The results indicate that most water quality parameters showed the site-specific patterns over the study, except for water temperature and dissolved oxygen. The levels of water quality parameters were highest at the site of Wonju stream, whereas the lowest in the upstream sites, and intermediate or gradually decreased in the downstream sites of the Seom river. One species, Achnanthes convergens, showed the highest biomass and frequency over the sites, while three saprophilous species-Navicula goeppertiana, Navicula subminuscula, Nitzschia palea were appeared only in Wonju Stream and other polluted sites. According to trophic diatom index (TDI) values, which were highly correlated with nutrients and EC, the study sites were classified into three classes: upstream and tributary (Class A and B), Wonju Stream (Class D), and mixed zone and downstream (Class C). A cluster analysis supported the result of TDI classification. Therefore, Wonju-stream located in populated urban area exerted the adverse ecological effects on the epilithic diatom community and water quality of the lower Seom River System, although its severity gradually decreased downstream.