• Journal of Ecology and Environment
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• v.47 no.4
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• pp.241-249
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• 2023

Background: This study analyzed the drought responses of five forest tree species grown in Korean peninsula, Korean fir Abies koreana (Ak), eastern white pine Pinus strobus (Ps), keyaki Zelkova serrata (Zs), tulip tree Liriodendron tulipifera (Lt), and Japanese elm Ulmus japonica (Uj). Physiological (chlorophyll, root collar diameter [RCD]) and biochemical responses (non-structural carbohydrates, proline, lipid peroxidase and abscisic acid [ABA]) of the plants grown under mild (MD) and severe drought (SD) were compared. Results: In this study, three soil moisture regimes: control (100% precipitation), MD (60% reduction in precipitation) and SD (20% reduction in precipitation) were applied. Soil moisture content showed high water content in control site compared to MD and SD. A decline in RCD was found for Korean fir, keyaki, and tulip plants, with eastern white pine and Japanese elm showing no significant decline to the prolonged drought exposure (both MD and SD). Total chlorophyll showed a significant decline in Korean fir and tulip, with the sugar levels indicating a significant increase in Korean fir and keyaki species under SD compared to control plants. Non-significant decline in sugar level was noted for eastern white pine and Japanese elm. High accumulation of ABA, malondealdehyde and proline was noted in Korean fir, tulip, and keyaki under SD compared to control. Signs of tree mortality was only observed in Korean fir under MD (38%) and SD (43%). Conclusions: The observed findings indicate the drought responses of five tree species. The majority of the morpho-physiological (especially mortality) and biochemical variables assessed in our study indicate superior long-term drought resistance of Ps and Uj compared to the highly sensitive Ak, and moderately sensitive Lt and Zs. The results provided will help species selection for afforestation programs and establishment of sustainable forests, especially of drought-tolerant species, under increased frequency and intensity of spring and summer droughts.

• Korean Journal of Environmental Agriculture
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• v.7 no.1
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• pp.43-51
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• 1988

$SO_2$ gas injuries for 19 varieties of 10 species of plants were investigated within a environmentally controlled growth chamber. Visible injuries were observed when exposing the plants either 0, 0.2, 0.4, 0.7 or 1.5ppm of $SO_2$ gas for 5 days from 9 : 00 to 17 : 00 everyday. The results obtained were as follows: 1. Light brown spots were shown on Raphanus sativus(Chunchu, Taeback, Jinjudaepyung), Brassica campestris(Manchun, Josaengmiho, Seoul, Jeonseung), and Capsicum annum(Searona, Hongsanho, Hongilpum); brown spots on Sesamum indicum(Pungnyun, Kwangsan); reddish brown shades on Cleosia cristata; and black brown spots on Perilla frutescens, Calendula officinalis, Chrysanthemum morifolium, and Salvia splendens, respectively. 2. The spotty injuries induced by $SO_2$ gas injuries for 19 varieties of 10 species of plants were investigated within a environmentally controlled growth chamber. Visible injuries were observed when exposing the plants either 0, 0.2, 0.4, 0.7 or 1.5ppm of $SO_2$ gas for 5 days from 9 : 00 to 17 : 00 everyday. The results obtained were as follows: 1. Light brown spots were shown on Raphanus sativus(Chunchu, Taeback, Jinjudaepyung), Brassica campestris(Manchun, Josaengmiho, Seoul, Jeonseung), and Capsicum annum(Searona, Hongsanho, Hongilpum); brown spots on Sesamum indicum(Pungnyun, Kwangsan); reddish brown shades on Cleosia cristata; and black brown spots on Perilla frutescens, Calendula officinalis, Chrysanthemum morifolium, and Salvia splendens, respectively. 2. The spotty injuries induced by SO₂ gas on Raphanus sativus, Callistephus chinensis, Capsicum annum, Perilla frutescens, Calendula officinalis, Salvia splendens, and Sesamum indicum; the many small spots on Chrysanthemum morifolium; and the brown shade on Celosia cristata appeared on the upper surface of the intervein, on the leaf apex area and on the entire upper surface of leaves, respectively. 3. Visual injuries of Capsicum annum(Chunchu), Perilla frutescens, Sesamum indicum(Pungnyun, Kwangsan), and Salvia splendens were developed at 0.4ppm of SO₂ gas fumigation. Brassica campestris(Jeonseung), Capsicum annum(Searona, Hongilpum), and Cleosia cristata, however, showed the injury at 1.5ppm of $SO_2$ gas concentration. 4. Based on the tolerance grade(time when the 1st injury appeared), Raphanus sativus, Perilla frutescens, Sesamum indicum, and Salvia splendens were the most sensitive plants and Chrysanthemum morifolium, Callistephus chinensis, Cleosia cristata, and Calendula officinalis were the plants most tolerant of $SO_2$ gas. gas on Raphanus sativus, Callistephus chinensis, Capsicum annum, Perilla frutescens, Calendula officinalis, Salvia splendens, and Sesamum indicum; the many small spots on Chrysanthemum morifolium; and the brown shade on Celosia cristata appeared on the upper surface of the intervein, on the leaf apex area and on the entire upper surface of leaves, respectively. 3. Visual injuries of Capsicum annum(Chunchu), Perilla frutescens, Sesamum indicum(Pungnyun, Kwangsan), and Salvia splendens were developed at 0.4ppm of $SO_2$ gas injuries for 19 varieties of 10 species of plants were investigated within a environmentally controlled growth chamber. Visible injuries were observed when exposing the plants either 0, 0.2, 0.4, 0.7 or 1.5ppm of $SO_2$ gas for 5 days from 9 : 00 to 17 : 00 everyday. The results obtained were as follows: 1. Light brown spots were shown on Raphanus sativus(Chunchu, Taeback, Jinjudaepyung), Brassica campestris(Manchun, Josaengmiho, Seoul, Jeonseung), and Capsicum annum(Searona, Hongsanho, Hongilpum); brown spots on Sesamum indicum(Pungnyun, Kwangsan); reddish brown shades on Cleosia cristata; and black brown spots on Perilla frutescens, Calendula officinalis, Chrysanthemum morifolium, and Salvia splendens, respectively. 2. The spotty injuries induced by SO₂ gas on Raphanus sativus, Callistephus chinensis, Capsicum annum, Perilla frutescens, Calendula officinalis, Salvia splendens, and Sesamum indicum; the many small spots on Chrysanthemum morifolium; and the brown shade on Celosia cristata appeared on the upper surface of the intervein, on the leaf apex area and on the entire upper surface of leaves, respectively. 3. Visual injuries of Capsicum annum(Chunchu), Perilla frutescens, Sesamum indicum(Pungnyun, Kwangsan), and Salvia splendens were developed at 0.4ppm of SO₂ gas fumigation. Brassica campestris(Jeonseung), Capsicum annum(Searona, Hongilpum), and Cleosia cristata, however, showed the injury at 1.5ppm of $SO_2$ gas concentration. 4. Based on the tolerance grade(time when the 1st injury appeared), Raphanus sativus, Perilla frutescens, Sesamum indicum, and Salvia splendens were the most sensitive plants and Chrysanthemum morifolium, Callistephus chinensis, Cleosia cristata, and Calendula officinalis were the plants most tolerant of $SO_2$ gas. gas fumigation. Brassica campestris(Jeonseung), Capsicum annum(Searona, Hongilpum), and Cleosia cristata, however, showed the injury at 1.5ppm of $SO_2$ gas concentration. 4. Based on the tolerance grade(time when the 1st injury appeared), Raphanus sativus, Perilla frutescens, Sesamum indicum, and Salvia splendens were the most sensitive plants and Chrysanthemum morifolium, Callistephus chinensis, Cleosia cristata, and Calendula officinalis were the plants most tolerant of $SO_2$ gas.

• Korean Journal of Ecology and Environment
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• v.41 no.4
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• pp.441-448
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• 2008

The purpose of this study was to analyze chemical water quality, fish trophic guilds, tolerance indicators, and fish community conditions in the Gap Stream and to compare the stream conditions between the unimpacted site and impacted site. This study was conducted in the physically stable season (May 2008) to minimize physical impacts such as flow and hydrological disturbance, and applied the study in the Gap Stream with two sites of unimpacted upstream site (Unim-S), mainly surrounded by forested area and impacted site (Im-S), influenced by the wastewater disposal plants and industrial complex in the urban region. Chemical data analysis showed that the degree of organic matter pollution, based on BOD, and COD, was $2{\sim}3$ fold greater in the Im-S than the Unim-S, and that TP, as eutrophication indicators, was 4.7 fold greater in the Im-S. Also, $NH_3-N$ was in 8.2 fold greater in the Im-S ($6.25\;mg\;L^{-1}$) than the Unim-S ($0.76\;mg\;L^{-1}$), indicating a massive influence of wastewater from the disposal plant. Similar results were found in other chemical parameters. Thus, chemical impacts in the Im-S were evident, compared to the unimpacted site. Evaluations of tolerant indicator species indicated that sensitive species were dominant in the Unim-S (23.9%) and tolerant species were dominant (97.8%) in the Im-S. Condition factor (CF) was averaged 0.95 ($0.68{\sim}1.18$) in the Unim-S and 1.08 ($0.93{\sim}1.22$) in the Im-S. Fish community in the Unim-S and Im-S was categorized as Zacco-community and Hemibarbus-community, respectively, and the community diversity index (H') was significantly (p<0.05) higher in the Unim-S (0.810) than the Im-S (0.466). Overall, our results suggest that the comparison approach of various chemical and ecological indicators provide important information in identifying multiple stressors in the stream ecosystems.

• Journal of Plant Biotechnology
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• v.44 no.2
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• pp.142-148
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• 2017

Drought stress is one of the important factors that restrict the expansion of Hevea brasiliensis cultivation to non-traditional regions experiencing extreme weather conditions. Plants respond to drought stress by triggering expression of several drought responsive genes including transcription factors which in turn trigger expression of various downstream signalling pathways and adaptive networks. Expression of such drought responsive genes may revert back to their original level upon re-watering. However, no reports are available on such phenomenon in Hevea and hence, this study was initiated. For this purpose, NAC transcription factor (NAC tf) was chosen as candidate gene. Its expression levels were monitored under intermittent drought as well as irrigated conditions in two clones (RRII 105 and RRIM 600) of H. brasiliensis with contrasting tolerance level. Copy number of NAC tf was found similar in both the clones. Expression of NAC tf was found highly up-regulated in RRIM 600 (a relatively drought tolerant clone) than in RRII 105 (a relatively drought susceptible clone) throughout the drought incidences which upon re-watering, reached back to its original levels in both the clones. The study indicated the existence of an association between expression of NAC tf and drought tolerance trait exhibited by the tolerant clone RRIM 600. The study also proves the influence of drought and re-watering on the leaf photosynthesis and expression of NAC tf in H. brasiliensis.

• Journal of Ecology and Environment
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• v.35 no.4
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• pp.279-289
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• 2012

This study conducted a comparative analysis of benthic macroinvertebrate communities in the Fosu and Benya lagoons in Ghana, based on the anthropogenic effect on the two lagoons. Salinity, oxygen, temperature, conductivity, turbidity and pH were measured, invertebrate richness and species densities were determined. The AZTI Marine Biotic Index (AMBI) and multivariate statistics were used to determine the different responses of fauna to pollution. The fauna were categorized into five ecological groups based on the degree of tolerance of the different species to pollution: disturbance-sensitive species; disturbance-indifferent species, disturbance-tolerant species, second-order opportunistic species; and first-order opportunistic species. The Fosu Lagoon supported more pollution tolerant species, whereas the Benya Lagoon had more species that were sensitive to organic enrichment under relatively unpolluted conditions. Chironomus sp., which is adapted to virtually anoxic conditions, was the most abundant in the Fosu Lagoon whereas Nemertea sp. was the most abundant in the Benya Lagoon. The numerical and relative abundance (%) of all 7 taxa in the Fosu Lagoon was 1,359 and 92.35%, respectively. The numerical and relative abundance (%) of all 34 taxa in the Benya Lagoon was 2,459 and 87.52%, respectively. Expectedly, the level of dissolved oxygen in the less saline Fosu Lagoon was higher than that in the more saline Benya Lagoon. The reduced photoperiod and photosynthetic activities of aquatic plants might account for this trend. There is a need to implement comprehensive monitoring and management initiatives for sustaining the ecological health of coastal lagoons in Ghana in order to support the many people that depend upon these ecosystems for their livelihood.

• Journal of Microbiology and Biotechnology
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• v.24 no.9
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• pp.1162-1169
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• 2014

Glyphosate is the active component of the top-selling herbicide, the phytotoxicity of which is due to its inhibition of the shikimic acid pathway. 5-Enolpyruvylshikimate-3-phosphate synthase (EPSPS) is a key enzyme in the shikimic acid pathway. Glyphosate tolerance in plants can be achieved by the expression of a glyphosate-insensitive aroA gene (EPSPS). In this study, we used a PCR-based two-step DNA synthesis method to synthesize a new aroA gene ($aroA_{R.\;leguminosarum}$) from Rhizobium leguminosarum. In vitro glyphosate sensitivity assays showed that $aroA_{R.\;leguminosarum}$ is glyphosate tolerant. The new gene was then expressed in E. coli and key kinetic values of the purified enzyme were determined. Furthermore, we transformed the aroA gene into Arabidopsis thaliana by the floral dip method. Transgenic Arabidopsis with the $aroA_{R.\;leguminosarum}$ gene was obtained to prove its potential use in developing glyphosate-resistant crops.

• Journal of Microbiology and Biotechnology
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• v.25 no.7
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• pp.978-987
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• 2015

Aluminum (Al) toxicity is one of the greatest limitations to agriculture in acid soils, particularly in tropical regions. Arbuscular mycorrhizal fungi (AMF) can supply plants with nutrients and give protection against Al toxicity. The aim of this work was to evaluate the effects of soil liming (i.e., reducing Al saturation) on the AMF community composition and structure in the roots of maize lines contrasting for Al tolerance. To this end, we constructed four 18S rDNA cloning libraries from L3 (Al tolerant) and L22 (Al sensitive) maize lines grown in limed and non-limed soils. A total of 790 clones were sequenced, 69% belonging to the Glomeromycota phylum. The remaining sequences were from Ascomycota, which were more prominent in the limed soil, mainly in the L3 line. The most abundant AM fungal clones were related to the family Glomeraceae represented by the genera uncultured Glomus followed by Rhizophagus and Funneliformis. However, the most abundant operational taxonomic units with 27% of the Glomeromycota clones was affiliated to genus Racocetra. This genus was present in all the four libraries, but it was predominant in the non-limed soils, suggesting that Racocetra is tolerant to Al toxicity. Similarly, Acaulospora and Rhizophagus were also present mostly in both lines in non-limed soils. The community richness of AMF in the non-limed soils was higher than the limed soil for both lines. The results suggest that the soil Al saturation was the parameter that mostly influences the AMF species composition in the soils in this study.

• Journal of Microbiology and Biotechnology
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• v.30 no.10
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• pp.1500-1509
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• 2020

Drought is a major abiotic factor and has drastically reduced crop yield globally, thus damaging the agricultural industry. Drought stress decreases crop productivity by negatively affecting crop morphological, physiological, and biochemical factors. The use of drought tolerant bacteria improves agricultural productivity by counteracting the negative effects of drought stress on crops. In this study, we isolated bacteria from the rhizosphere of broccoli field located in Daehaw-myeon, Republic of Korea. Sixty bacterial isolates were screened for their growth-promoting capacity, in vitro abscisic acid (ABA), and sugar production activities. Among these, bacterial isolates YNA59 was selected based on their plant growth-promoting bacteria traits, ABA, and sugar production activities. Isolate YNA59 highly tolerated oxidative stress, including hydrogen peroxide (H₂O₂) and produces superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) activities in the culture broth. YNA59 treatment on broccoli significantly enhanced plant growth attributes, chlorophyll content, and moisture content under drought stress conditions. Under drought stress, the endogenous levels of ABA, jasmonic acid (JA), and salicylic acid (SA) increased; however, inoculation of YNA59 markedly reduced ABA (877 ± 22 ng/g) and JA (169.36 ± 20.74 ng/g) content, while it enhanced SA levels (176.55 ± 9.58 ng/g). Antioxidant analysis showed that the bacterial isolate YNA59 inoculated into broccoli plants contained significantly higher levels of SOD, CAT, and APX, with a decrease in GPX levels. The bacterial isolate YNA59 was therefore identified as Variovorax sp. YNA59. Our current findings suggest that newly isolated drought tolerant rhizospheric Variovorax sp. YNA59 is a useful stress-evading rhizobacterium that improved drought-stress tolerance of broccoli and could be used as a bio-fertilizer under drought conditions.

• Nuclear Engineering and Technology
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• v.52 no.3
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• pp.597-609
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• 2020

Accident Tolerant Fuels have been widely studied since the Fukushima-Daiichi accident in 2011 as one of the options on how to further enhance the safety of nuclear power plants. Deposition of protective coatings on nuclear fuel claddings has been considered as a near-term concept that will reduce the high-temperature oxidation rate and enhance accidental tolerance of the cladding while providing additional benefits during normal operation and transients. This study focuses on experimental testing of Zr-based alloys coated with Cr-based coatings using Physical Vapour Deposition. The results of long-term corrosion tests, as well as tests simulating postulated accidents, are presented. Zr-1%Nb alloy used as nuclear fuel cladding serves as a substrate and Cr, CrN, Cr_xN_y layers are deposited by unbalanced magnetron sputtering and reactive magnetron sputtering. The deposition procedures are optimized in order to improve coating properties. Coated as well as reference uncoated samples were experimentally tested. The presented results include standard long-term corrosion tests at 360℃ in WWER water chemistry, burst (creep) tests and mainly single and double-sided high-temperature steam oxidation tests between 1000 and 1400℃ related to postulated Loss-of-coolant accident and Design extension conditions. Coated and reference samples were characterized pre- and post-testing using mechanical testing (microhardness, ring compression test), Thermal Evolved Gas Analysis analysis (hydrogen, oxygen concentration), optical microscopy, scanning electron microscopy (EDS, WDS, EBSD) and X-ray diffraction.

• Journal of Plant Biotechnology
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• v.36 no.3
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• pp.219-223
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• 2009

Oxidative stress derived from excess reactive oxygen species (ROS) is a major damaging factor for plants exposed to environmental stresses. Sweetpotato [Ipomoea batatas (L.) Lam] has a relatively broad adaptability to harsh environmental conditions compared to other staple crops. In this study, to select stress-tolerant sweetpotato cultivars for sources of molecular breeding on marginal lands, we evaluated the ion leakage values in 10 different cultivars after treatment of methyl viologen (MV), an ROS-generating nonselective herbicide, to leaf discs. DPPH radical scavenging activity and the contents of total phenolics were also investigated. The ion leakage of each cultivar showed a diverse value, which is well correlated with DPPH radical scavenging activity of each cultivar. DPPH radical scavenging activity also showed a high corelation with the contents of total phenolic contents. Three cultivars of Yanshu 8, Shinhwangmi and Shinzami showed high antioxidant activity. Our results suggest that a simple and efficient DPPH radical scavenging activity would be a suitable method to select potential cultivars with enhanced tolerance to multiple environmental stress.