• Proceedings of the Korean Environmental Sciences Society Conference
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• 2007.05a
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• pp.460-464
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• 2007

개구리밥, 생이가래, 은행이끼, 수련, 부들 등 5종의 식물을 대상으로 카드뮴 $(Cd^{2+})$의 농도를 달리하여 처리한 후 시간별로 식물의 광합성효율을 분석하였다. 그 결과, 개구리밥, 생이가래, 은행이끼, 부들 등 4종은 카드뮴에 민감한 것으로 조사되었고, 수련은 다른 식물종에 비해 덜 민감한 것으로 나타났다. O-J-I-P 곡선의 패턴을 살펴보면, 종에 따라 다소의 차이는 있으나 개구리밥, 생이가래, 은행이끼, 부들 등 4종의 식물은 카드뮴 농도가 증가할 수록 J, I, P값이 크게 감소하는 것을 볼 수 있었다. 특히 P-단계의 감소는 개구리밥에서 현저하게 나타나 다른 3종 보다 카드뮴에 민감한 것으로 보인다. 광계II의 광합성효율(Fv/Fm) 변화양상을 보면, 개구리밥과 생이가래는 카드뮴 농도가 50uM 이상에서는 배양 1일부터 Fv/Fm값이 급격하게 감소하였으며, 은행이끼와 부들은 3일 이후부터 50uM 이상의 카드뮴 농도하에서 Fv/Fm값이 감소하였다. 수련은 큰 변화를 보이지 않았다.

• Applied Microscopy
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• v.34 no.2
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• pp.103-111
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• 2004

Fresh specimens of the aquatic macrophyte, Spirodela polyrhiza, have been examined employing scanning and transmission electron microscopy. Observations revealed the occurrence of microbial colonization during development. Submerged parts of the small, free-floating S. polyrhiza body exhibited a variety of microorganisms such as bacteria, cyanobacteria, and diatoms throughout their development. However, immature and/or young plants normally demonstrated much less microbial colonization compared to mature plants. During the study, heavy colonization by the microorganisms was routinely encountered at maturity, especially in the fully developed abaxial fronds and root caps. The mucilaginous layer was shown along the root caps, and the microorganisms appeared to be either clustered or attached to this layer. In contrast, only moderate degrees of colonization were observed in the root, and little to no colonization was observable in the adaxial frond surface. Transmission electron microscopy clearly demonstrated the microbial colonization to be external in the S. polyrhiza specimen examined in the current study. The association between the microorganisms and S. polyrhiza has been considered non-harmful, as no frond senescence and almost no mechanical penetration of the plant by the microorganisms were noticed during the study.

• Korean Journal of Environment and Ecology
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• v.32 no.4
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• pp.425-439
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• 2018

W investigated the environmental factors and inhabiting biota such as macrophytes and zooplankton in 43 sites located on Jeju Island from May and June 2017 to evaluate the spread and ecosystem risk of dotted duckweed (landoltia punctata) which was recently found for the first time in Jeju Island. Dotted duckweeds were found in a total of 18 sites which tended to show low biomass of aquatic macrophyte species other than the dotted duckweed. We conducted a pattern analysis using SOM (Self-Organizing Map), which extracts information through competitive and adaptive properties, to analyze the effect of inhabiting biota on aquatic macrophytes such as the dotted duckweed and environmental factors. The SOM analysis showed that the inhabiting biota such as the zooplankton affected the biomass of aquatic macrophytes than they did the environmental factors. In particular, the biomass of dotted duckweed was positively related to plant-attached species (Alona, Chydorus, and Pleuroxus). Considering that low density of aquatic macrophytes covers the streams and wetlands on Jeju Island because of irregular water source and sharp change of water depth, the dotted duckweeds are likely to play an essential role as the vital habitat for micro-biota including zooplankton in wetlands and streams on Jeju Island. Furthermore, considering that organic matters are utilized as the primary food source in the areas occupied by dotted duckweed, dotted duckweeds have the role of being both habitat and food source. Although the dense growth of dotted duckweed adversely affects growth and development of some aquatic plants due to the shadow effect, it is due to the dominance of floating plants on the water surface should not be regarded as the risk of the dotted duckweed. In conclusion, the dotted duckweeds have spread and settled in most of the water systems on Jeju Island, their impact on inhabiting biota and the aquatic environment was minor. It is necessary to monitor the distribution and spread of dotted duckweeds in the inland areas outside of Jeju Island in the future.

• Korean Journal of Environment and Ecology
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• v.28 no.5
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• pp.510-515
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• 2014

Duckweed (Lemna perpusilla J. Torrey) is a typical floating aquatic macrophyte that has been used for evaluating phytotoxicity of toxicants. In this study, we evaluated the responses of duckweed to PAHs and ammonium as toxicants that frequently affect the growth of plants in polluted industrial and agricultural areas. As the duckweed is growing in aquatic environment, the PAHs and ammonium were incorporated into nutrient solution and the fronds were cultured hydroponically. Frond growth was responded differentially to the concentration and type of PAHs. The severe inhibition of frond growth was observed in the treatment of fluorene. Fluoranthene and pyrene, however, showed weak inhibition of frond growth. The latter PAHs that showed weak inhibition did not reduced frond number at the low concentration of 30 ppm. Pigment contents were also responded differentially. Phenanthrene and fluorene reduced chlorophyll content more strongly than fluoranthene and pyrene. Carotenoids, well-known antioxidative compound, was relatively increased at the low concentration of PAHs up to 30 ppm by the treatment of fluoranthene and pyrene, suggesting an increased antioxidative activity in fronds. Ammonium treatment showed higher inhibitory effect even low concentration of 3 mM.

• Korean journal of applied entomology
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• v.46 no.1 s.145
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• pp.13-18
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• 2007

Morphological characters of adult and immature stages on Elophila turbata (Butler, 1881) belonging to subfamily Nymphulinae, family Crambidae are redescribed base on Korean materials. Also we observed biological characters of this species including host plants, Spirodela polyrhiza(L.) Schleiden, Salvinia natans ($Linn\acute{e}$) Allioni and Lemna perpusilla Torre. And, photographs of adult, genitalia and immature stages are provided.

• Applied Microscopy
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• v.41 no.1
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• pp.55-60
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• 2011

Reduced plants of Spirodela polyrhiza consisting only of fronds, stalks and roots form turions during dormancy. In development, mature fronds produce offspring fronds by vegetative reproduction, and turions arise laterally from the mother frond before dormancy. The turion primordium is derived from the frond, while the frond primordium forms within the turion tissue. In the present study, cellular features, especially those of the plastids, of the above four tissue types have been examined and compared using electron microscopy. Proplastids, found to be numerous in the frond and turion primordia, differentiated into chloroplasts rapidly upon growth. The proplastids were small and the thylakoidal membrane system was rudimentary, howerver the chloroplasts exhibited variation by cell type. Chloroplasts were found within cells of the frond, stalk and root tissue. The thylakoidal membrane system, which formed grana stacks, was moderately developed within frond chloroplasts, while only a few were present in those of the stalk and root cortical cells. One to two starch grains were accumulated within frond chloroplasts, but little to none were found in stalk and root cortical chloroplasts. Contrary to other types of root chloroplasts, those found in the root cap cells developed chloroplasts similar to the frond type. Unlike proplastids of the turion primordia, numerous large amyloplasts occupied most of the turion cell volume. Moreover, the turion cell produced quite large starch grain (s) within the amyloplasts. Accumulation of the starch grains continued until they occupied the most of the stroma and in some cases, individual starch grains reached up to $9.0{\mu}m$ in length. None to little, if any, thylakoidal or internal membranous systems were seldom detected in these amyloplasts. Although the degree of cellular and tissue differentiation was rather minimal within their reduced body, the functional differentiation of Spirodela polyrhiza was very efficient, as is the case in other advanced species.

• Journal of Plant Biology
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• v.34 no.4
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• pp.253-260
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• 1991

Spirodela polyrhiza and Lemna aequinoctialis often occurred at the sites of high ammonium concentration and at the sites of high nitrate concentration, respectively. We investigated the different distribution between two species in relation to the type of nitrogen sources and their concentrations. Our experiments showed that L. aequinoctialis grew faster than S. polyrhiza in nitrate media with lower than 15 mM concentration. The nitrate uptake was also faster in L. aequinoctialis than in S. polyrhiza. However, neither differences in growth nor in uptake patterns between these two species were observed in ammonium media. Glutamine synthetase (GS), glutamate dehydrogenase (GDH) and glutamate synthetase (GOGAT) activities were higher in L. aequinoctialis. In particular, nitrate reductase activity (NRA) in L. aequinoctialis was 12.1 times as high as that in S. polyrhiza. These results showed that the two species responded varyingly to the types of nitrogen sources and their concentrations. Therefore, the difference in geographic distribution between the two species appeared to reflect the interspecific differences in enzyme activities and, subsequently, nitrogen absorption abilities.

• Journal of the Korean Chemical Society
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• v.8 no.4
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• pp.164-168
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• 1964

We isolated histone-type basic proteins from lemna paucicostata for the first time. Basic proteins were extracted directly with dilute mineral acids from homogenized lemna paucicostata. Amino acid compositions of basic protein portions adsorbed on Amberlite CG-50(at pH 6. 0) were resembled to those of calf thymus histones. Especially, lysine content was the greatest of the other amino acids. By chromatographic studies, adsorbed portions of basic protein components on carboxymethyl cellulose column(at pH 4. 2) were shown to be homogeneous to calf thymus histones, however, the area under the individual curve was different, and furthermore, the containing of a non-adsorbed portion in the large extent was markedly different from calf thymus histones. And amino acid compositions of adsorbed portions represented the histone-type basic propertes, but non-adsorbed portions were considered as a different protein compared with the typical histone. When calf thymus histone and protein components separated from lemna paucicostata were heated($60^{\circ}C$) with a solution of $HgSO_4-H_2SO_4$, precipitates were not obtained.

• Korean Journal of Environment and Ecology
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• v.31 no.4
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• pp.349-364
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• 2017

Duckweed family (Lemnaceae Martinov), including the genus Lemna L., is a typical floating aquatic perennial plant, and about five genera and 40 species in the family are in wide distribution around the world except the polar regions. The genus Lemna is the smallest and the simplest plant among the angiosperms. It has a characteristic of doubling every three days with fast vegetative propagation, which helps the organisms to increase in rapid growth. As such, the plant is ideal for environmental pollution assessment and toxicity test. Although taxonomists and scholars have used different scientific names for the species, many of them have agreed that there is only one member of species of the genus Lemna in Korea. Paying attention to the external morphological variation observed in the Korean genus Lemna, we conducted a molecular phylogenetic analysis to identify the entity of the Korean Lemna species and to investigate the possibility of two or more members of the species existing in Korea. We determined and aligned the DNA sequences of the atpF-H region of the chloroplast DNA in 37 populations of the nationally distributed Lemna species. The results showed that the sequence length of the cp DNA atpF-H region was 463-483 bp, the length of the aligned sequences was 488 bp, and the number of variation site in nucleotide sequences was 47. There were two types of aligned sequences of the cp DNA atpF-H region from 37 populations of Lemna species in Korea. The maximum parsimony analysis revealed that the Korean Lemna consists of two clades, and one of them had two subclades. The results suggest that, contrary to the general understanding, at least two taxa (L.aequinoctialis, L.minor) exist in Korea.

• Agrochemical news magazine
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• v.22 no.10 s.173
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• pp.42-44
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• 2001