• Korean Journal of Soil Science and Fertilizer
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• v.31 no.1
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• pp.56-60
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• 1998

Radish and Chinese cabbage were cultivated under hydrophonic culture to investigate the effect of chromium on germination, cell elongation, ${\alpha}$-amlyase activity, contents of chlorophyll and protein. With increasing concentration of cromium, germination, cell elongation, ${\alpha}$-amlyase activity were decreased in both radish and Chinese cabbage, the rate was higher in radish than in Chinese cabbage. Contents of chlorophyll a and b were also decreased and chlorophyll a was higher than chlorophyll b. As the concentration of chromium was increased inhibited in the order of protein> ${\alpha}$-amylase activity>chlorophyll a>chlorophyll b.

• Korean Journal of Weed Science
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• v.16 no.1
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• pp.64-71
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• 1996

This study was conducted to determine the physiological responses of corn plants to chlorsulfuron, CHL, (2-chloro-N-(((4-methoxy-6-methyl-1,3,5- triazin-2-yl)amino)carboxyl) benzenesulfonamide) and/or imazaquin, IMA, (2-(4,5-dihydro-4-methyl-4-(1-methyl)-5-oxo-1H-imidazol-2y1)-3-quinoline carboxylic acid). CHL inhibited the plant growth within 6h after treatment, whereas IMA inhibited the growth more slowly(i.e., 36h). CHL inhibited the cell division of the root tips rapidly, however, little effect was found with IMA treatment. Neither CHL nor IMA had effect on the cell elongation of the shoots. CHL inhibited acetolactate synthase(ALS) activity of the roots within 1h after treatment. Interaction between CHL and IMA in growth inhibition was found to be additive or synergistic with simultaneous or sequential treatment of the two herbicides, respectively. In addition, interaction between CHL and IMA in ALS inhibition was found to be additive when the two herbicides were treated simultaneously.

• Korean Journal of Animal Reproduction
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• v.11 no.3
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• pp.206-217
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• 1987

Testes from the drake and the gander have been examined by the electron microscopy in thin sections in order to examine the spermiogenesis and the structure of spermatozoa. The spermiogenesis can be divided into three stages: early spermatid, nuclear elongation, and matured spermatid. In the early spermatid of the drake, there are thread-like material in the nucleus, a prominent nuclear envelope around the nucleus, and big lumens in the cytoplasm. The shape of the gander's mitochondria in the early spermatid is slender compared to that of the drake, and the inner membrane of the mitochondria is thicker than the outer membrane. The distal centriole of the drake and the gander in the early spermatid is a long hollow cylinder form. In the nuclear elongation stage, elongated nucleus forms two or three cross sections in one spermatid cell and it is surrounded by the amorphous sheath. The nucleus of the matured spermatid is compact and its apical end is covered with acrosome cap and acrosome spine. The axoneme is surrounded by the amorphous material.

• Journal of Plant Biology
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• v.32 no.4
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• pp.305-312
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• 1989

Developmental anatomy was conducted in order to elucidate the differentiating pattern of fascicular cambial initials in the hypocotyl of Ricinus communis. The homogeneous procambium with relatively short cells in early stage is transformed into a heterogeneous structure with long and short cells in late stage in tangential view. Fusiform and ray initials are gradually originated from the long and short cells of the procambium in hypocotyl in later stage respectively. Fusiform initials are not shorter than procambial cells because of the successive elongation of vascular meristematic cells. Therefore, the distinction between procambium and fascicular cambium is not made from comparison with their cell length. The characteristics of the fascicular cambium are gradully acquired at or just after completion of hypocotyl elongation.

• Polymer(Korea)
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• v.26 no.2
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• pp.218-226
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• 2002

For the preparation of high resilience polyurethane (PU) foams with polyether type cell openers which have different ethylene oxide (EO) content, molecular weight and chain structure, the influences of tell opener structure on the kinetics, rheology, structural stability, open cell content and mechanical properties of the obtained foam were investigated. It was observed that urea formation reaction was delayed with the increase of EO content and incorporation of ester linkage in cell opener molecule and was relatively independent on the molecular weight. With the rheological studies, the decreases of viscosity and storage modulus were confirmed for the increase of EO content and molecular weight, so that the resulted foam had low structural stability and high open cell content. The cell opener having ester linkage in molecule exhibited the lowest values of viscosity and storage modulus and the obtained foam has high open cell content. However, the structural stability increased due to the larger intermolecular interaction of ester linkage. The hardness, tensile strength, tear strength and elongation of foam were deteriorated with increase of EO content and molecular weight of tell opener. On the other hand, the cell opener having ester linkage in molecule improved the values of tensile strength, tear strength and elongation.

• Journal of Plant Biotechnology
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• v.5 no.3
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• pp.137-142
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• 2003

The morphology of the leaves and the flowers of angiosperms exhibit remarkable diversity. One of the factors showing the greatest variability of leaf organs is the leaf index, namely, the ratio of leaf length to leaf width. In some cases, different varieties of a single species or closely related species can be distinguished by differences in leaf index. To some extent, the leaf index reflects the morphological adaptation of leaves to a particular environment. In addition, the growth of leaf organs is dependent on the extent of the expansion of leaf cells and on cell proliferation in the cellular level. The rates of the division and enlargement of leaf cells at each stage contribute to the final shape of the leaf, and play important roles throughout leaf development. Thus, the control of leaf shape is related to the control of the shape of cells and the size of cells within the leaf. The shape of flower also reflects the shape of leaf, since floral organs are thought to be a derivative of leaf organs. No good tools have been available for studies of the mechanisms that underlie such biodiversity. However, we have recently obtained some information about molecular mechanisms of leaf morphogenesis as a result of studies of leaves of the model plant, Arabidopsis thaliana. For example, the ANGUSTIFOLIA (AN) gene, a homolog of animal CtBP genes, controls leaf width. AN appears to regulate the polar elongation of leaf cells via control of the arrangement of cortical microtubules. By contrast, the ROTUNDIFOLIA3 (ROT3) gene controls leaf length via the biosynthesis of steroid(s). We provide here an overview of the biodiversity exhibited by the leaf index of angiosperms. Taken together, we can discuss on the possibility of the control of the shapes and size of plant organs by transgenic approaches with the results from basic researches. For example, transgenic plants that overexpressed a wildtype ROT3 gene had longer leaves than parent plants, without any changes in leaf width. Thus, The genes for leaf growth and development, such as ROT3 gene, should be useful tools for the biodesign of plant organs.

• Proceedings of the Korean Society of Plant Biotechnology Conference
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• 2003.04a
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• pp.49-55
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• 2003

The morphology of the leaves and the flowers of angiosperms exhibit remarkable diversity. One of the factors showing the greatest variability of leaf organs is the leaf index, namely, the ratio of leaf length to leaf width. In some cases, different varieties of a single species or closely related species can be distinguished by differences in leaf index. To some extent, the leaf index reflects the morphological adaptation of leaves to a particular environment. In addition, the growth of leaf organs is dependent on the extent of the expansion of leaf cells and on cell proliferation in the cellular level. The rates of the division and enlargement of leaf cells at each stage contribute to the final shape of the leaf, and play important roles throughout leaf development. Thus, the control of leaf shape is related to the control of the shape of cells and the size of cells within the leaf. The shape of flower also reflects the shape of leaf, since floral organs are thought to be a derivative of leaf organs. No good tools have been available for studies of the mechanisms that underlie such biodiversity. However, we have recently obtained some information about molecular mechanisms of leaf morphogenesis as a result of studies of leaves of the model plant, Arabidopsis thaliana. For example, the ANGUSTIFOLIA (AN) gene, a homolog of animal CtBP genes, controls leaf width. AN appears to regulate the polar elongation of leaf cells via control of the arrangement of cortical microtubules. By contrast, the ROTUNDIFOLIA3 (ROT3) gene controls leaf length via the biosynthesis of steroid(s). We provide here an overview of the biodiversity exhibited by the leaf index of angiosperms. Taken together, we can discuss on the possibility of the control of the shapes and size of plant organs by transgenic approaches with the results from basic researches. For example, transgenic plants that overexpressed a wild-type ROT3 gene had longer leaves than parent plants, without any changes in leaf width. Thus, The genes for leaf growth and development, such as ROT3 gene, should be useful tools for the biodesign of plant organs.

• ALGAE
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• v.24 no.4
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• pp.239-248
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• 2009

Fluorescence and electron microscopy were used to examine epidermal shedding in the fucoid alga, Ascophyllum nodosum. Mature meristoderm cells are ca. 50-100 x 30-40 ${\mu}m$ and highly polarized, with a single nucleus and chloroplasts near the base of the cell. Nuclei in these cells undergo mitosis when they are dividing to form a new cortical cell towards the middle of the frond, or anticlinal divisions as part of frond elongation. However, cytokinesis also occurs regularly in these cells when a new periclinal wall is deposited at about 30% of the cell length from the apical end. The newly formed distal cells are anucleate and without chloroplasts. Following cytokinesis the tangential walls then break at the thinnest point. The whole process is synchronous in adjoining epidermal cells across large areas of the frond surface, and this layer dehisces from the thallus. This is the only known plant or algal system in which cytokinesis regularly occurs in the absence of mitosis. We consider this process a novel form of programmed cell death.

• Molecules and Cells
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• v.19 no.3
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• pp.303-309
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• 2005

The end of eukaryotic genomic DNA is capped by a specialized structure called as "telomere" which consists of the repetitive array of nucleotide sequence, TTAGGG, in humans and mice, and a variety of binding proteins. Telomerase is a ribonucleoprotein (RNP) complex responsible for the elongation of telomeres to maintain the genomic integrity, and is composed of telomerase reverse transcriptase (TERT), telomerase RNA component (TERC), and their associated factors regulating the catalytic activity of telomerase. Although it is now apparent that telomerase protects cells from apoptosis via the maintenance of genomic integrity by stabilizing telomeres, our understanding for the physiological role of telomerase is yet far from completion, and emerging evidence suggests that telomerase has additional extratelomeric roles in mediating cell survival and anti-apoptotic functions against various cytotoxic stresses. Here we summarize and discuss how telomerase and telomeres are involved in mediating cellular protection against apoptosis.

• Food Science and Biotechnology
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• v.17 no.5
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• pp.1102-1105
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• 2008

The structural change and leakage of cellular substances of Saccharomyces cerevisiae attributed by high hydrostatic pressure (HHP) treatment were observed with scanning electron microscopy (SEM). S. cerevisiae (ATCC16664) was inoculated in apple juice for 10 min at $23^{\circ}C$ and the apple juice treated at 138, 207, 276, 345, and 414 MPa pressure for 30 sec at $23^{\circ}C$. Increased of roughness, elongation, wrinkling, and pores on yeast cell surfaces, the yeast cell walls were severely damaged by HHP treatment from 276 to 414 MPa. Inactivation of S. cerevisiae by HHP is dependent on structural changes on the cell walls observed with SEM.