• Korean Journal of Plant Tissue Culture
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• v.26 no.2
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• pp.115-119
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• 1999

The single node cuttings of sweet potato (cv. Mokpo #29) plantlets maintained in vitro were cultured with (MF+) or without membrane filter (MF-) under photomixotrophic (PM), hetrotrophic (HT) and autotrophic (AT) conditions. Shoot length was the greatest (11.9cm) in 3$0^{\circ}C$ (HT) treatment and it was the shortest (3.4 cm) in $25^{\circ}C$ (PM) treatment. Nodal explants cultured in 3$0^{\circ}C$ treatment looked more vigorous than those of $25^{\circ}C$ in appearance, and node number was the greatest (10.5 per plantlet) among the treatments. But plantlets grew in 3$0^{\circ}C$ (HT) treatment were observed all overgrown. The size in leaf area was about 2 times greater and shoot length was about 2 times shorter in PM than in HT condition. Percent dry matter of shoots was 5.9% (HT) and 7.4% (PM) in $25^{\circ}C$ treatment and 6.1% (HT) and 7.4% (PM) in 3$0^{\circ}C$ treatment. Plantlets cultured in the MF+ treatments were less succulent than those cultured in the MF- treatment. Vitrified plantlets were examinated 14.8% (both $25^{\circ}C$ and 3$0^{\circ}C$) in PM condition and 22.2% ($25^{\circ}C$) and 31.5% (3$0^{\circ}C$) in HT condition. Sucrose was necessary for the survival of in vitro plantlets. In the sucrose-free medium, explants cultured in the MF- had turned yellow and were dead after 30 days of culture. But explants cultured in the MF+ were alive and produced plantlets with shoot and root (AT). On the other hand, the survival of explants on the MS basal medium (sucrose-free and hormone-free) depended entirely upon the MF attachment.

• Korean Journal of Weed Science
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• v.12 no.2
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• pp.102-109
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• 1992

There was significant reduction in the mitotic indices of oat roots treated with alachlor. Uniform decrease in prophase, metaphase, anaphase, and telophase as treatment time increasing was observed. Alachlor did not disrupt mitosis, but rather inhibited the onset of mitosis. Labeled dividing cells were significantly inhibited, but the number of labeled interphase cells of all treatment were increased, as compared with control in 8 hr and 12hr period. Labeled dividing cells which entered mitosis thru $G_2$ were inhibited approximately 68% at 8hr after treatment with $1{\times}10^{-5}$ M of alachlor. Alachlor apparently inhibited from the $G_2$stage into mitosis of dividing cells. After 24 hr treatment, 12.1% abd 46.6% inhibition of coleoptile growth occurred at $1{\times}10^{-5}$ M and $1{\times}10^{-4}$ M, respectively. Cell elongation was inhibited by alachlor but was less sensitive than cell division. The longitudinal section cells of oat roots treated with $1{\times}10^{-4}$ M alachlor for 12 hr were observed to be enlarged central cylinder and also showed degradation of apical meristem zone, as compared with the untreated roots.

• Korean Journal of Plant Tissue Culture
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• v.27 no.6
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• pp.423-428
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• 2000

In 1997 when cloned sheep Dolly and soon after Polly were born, it had become head-line news because in the former the nucleus that gave rise to the lamb came from cells of six-year-old adult sheep and in the latter case a foreign gene was inserted into the donor nucleus to make the cloned sheep produce human protein, factor IX, in e milk. In the last few years, once the realm of science fiction, cloned mammals especially in livestock have become almost commonplace. What the press accounts often fail to convey, however, is that behind every success lie hundreds of failures. Many of the nuclear-transferred egg cells fail to undergo normal cell divisions. Even when an embryo does successfully implant in the womb, pregnancy often ends in miscarriage. A significant fraction of the animals that are born die shortly after birth and some of those that survived have serious developmental abnormalities. Efficiency remains at less than one % out of some hundred attempts to clone an animal. These facts show that something is fundamentally wrong and enormous hurdles must be overcome before cloning becomes practical. Cloning researchers now tent to put aside their effort to create live animals in order to probe the fundamental questions on cell biology including stem cells, the questions of whether the hereditary material in the nucleus of each cell remains intact throughout development, and how transferred nucleus is reprogrammed exactly like the zygotic nucleus. Stem cells are defined as those cells which can divide to produce a daughter cell like themselves (self-renewal) as well as a daughter cell that will give rise to specific differentiated cells (cell-differentiation). Multicellular organisms are formed from a single totipotent stem cell commonly called fertilized egg or zygote. As this cell and its progeny undergo cell divisions the potency of the stem cells in each tissue and organ become gradually restricted in the order of totipotent, pluripotent, and multipotent. The differentiation potential of multipotent stem cells in each tissue has been thought to be limited to cell lineages present in the organ from which they were derived. Recent studies, however, revealed that multipotent stem cells derived from adult tissues have much wider differentiation potential than was previously thought. These cells can differentiate into developmentally unrelated cell types, such as nerve stem cell into blood cells or muscle stem cell into brain cells. Neural stem cells isolated from the adult forebrain were recently shown to be capable of repopulating the hematopoietic system and produce blood cells in irradiated condition. In plants although the term$\boxDr$ stem cell$\boxUl$is not used, some cells in the second layer of tunica at the apical meristem of shoot, some nucellar cells surrounding the embryo sac, and initial cells of adventive buds are considered to be equivalent to the totipotent stem cells of mammals. The telomere ends of linear eukaryotic chromosomes cannot be replicated because the RNA primer at the end of a completed lagging strand cannot be replaced with DNA, causing 5' end gap. A chromosome would be shortened by the length of RNA primer with every cycle of DNA replication and cell division. Essential genes located near the ends of chromosomes would inevitably be deleted by end-shortening, thereby killing the descendants of the original cells. Telomeric DNA has an unusual sequence consisting of up to 1,000 or more tandem repeat of a simple sequence. For example, chromosome of mammal including human has the repeating telomeric sequence of TTAGGG and that of higher plant is TTTAGGG. This non-genic tandem repeat prevents the death of cell despite the continued shortening of chromosome length. In contrast with the somatic cells germ line cells have the mechanism to fill-up the 5' end gap of telomere, thus maintaining the original length of chromosome. Cem line cells exhibit active enzyme telomerase which functions to maintain the stable length of telomere. Some of the cloned animals are reported prematurely getting old. It has to be ascertained whether the multipotent stem cells in the tissues of adult mammals have the original telomeres or shortened telomeres.

• Korean Journal of Weed Science
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• v.14 no.3
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• pp.199-211
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• 1994

Butachlor applied pre-emergence at 3.6kg ai/ha inhibited the growth and developments of shoot of barnyardgrass under dry condition, whereas rice was unaffected. Growth of rice and barnyardgrass under water condition was severely inhibited by treatment of butachlor but that of transplanted rice was not affected. The inhibition rate was higher under water condition, in broadcast rice and direct seeded rice than under dry condition, drilled rice and transplanted rice, respectively. The major anatomical response of stem of barnyardgrass seedling to butachlor under dry condition were partial reduction in thickness and collapse of leaf sheath, while not in rice. Broadcast rice on soil under water condition appeared reduction and constriction of leaf primordia thickness, and barnyardgrass formed tubular-like leaves and showed inhibited elongation of apical meristem. On the other hand, transplanted rice did not show these responses.

• Journal of Ginseng Research
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• v.26 no.4
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• pp.219-225
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• 2002

Study was performed to know the effects of Panax ginseng C.A. Meyer hairy root due to $^{60}$ Co ${\gamma}$-ray irradiation. We irradiated the hairy roots under the various $^{60}$ Co ${\gamma}$-ray; 0.5~4 Krad. The growth of hairy roots is inhibited over 3 Krad treatment. The lateral roots are used as a cell line after removing the apical meristem of hairy roots irradiated below 2 Krad. We selected 206 hairy root cell lines having various different growth rates and forms, and incubated in the 1/2 Murashige & Skoog(MS) medium in the absence of hormone. We selected 10 out of 206 showing superior growth. Among those, ${\gamma}$-GHR 70 and ${\gamma}$-GHR 94 showed higher growth; 34.5, 44.7%, respectively. We observed shapable, sizable characteristics according to the width of the primary roots, the process formation of the lateral roots, and the growth of lateral roots. The discriminable cell line showed that primary root is thinner, and has a vigorous growth. 8 out of 10 had much more contents than control in the aspect of the ginsenoside. ${\gamma}$-GHR 59 and ${\gamma}$-GHR 94 showed higher contents; 19, 16.9%, respectively. Therefore, we selected ${\gamma}$-GHR 70, ${\gamma}$-GHR 94 as a superior cell line in the aspect of ginsenoside contents, and growth among those irradiated by ${\gamma}$-ray. According to content of ginsenoside, Rb$_2$ effective in anticancer has 7.5% of ${\gamma}$-GHR 59. Rc, also effective in anticancer showed 16.2% content increasement of ${\gamma}$-GHR 69. It is thought that those lines will be effective in manufacturing ginsenoside. Gene analysis (VNTRP) related to the mutation is in progress.

• Applied Microscopy
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• v.37 no.2
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• pp.83-91
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• 2007

The present study examined the epidermal changes of adhesive disks which occur during attachment in Parthenocissus tricuspidata using scanning and transmission electron microscopy. Several adhesive disks, each covered with a bract, develop from the shoot apical meristem during early development. In the initial stage, the adhesive disks are club-shaped and their upper and lower epidermis are indistinguishable. However, in the actively growing stage, they become spherical and both epidermis are clearly differentiated into the adventitious roots. Prior to wall attachment, the adhesive disks exhibit adaxial convex and abaxial concave shapes, and electron-dense substances are abundant in the vacuoles of epidermal cells. The peripheral area of the adhesive disk is adhered first to the wall surface, while the central area is drawn inward in a vacuum-like state during attachment. As the attachment progresses and the electron-dense substances continue to discharge, the upper and lower epidermis rapidly undergo deterioration and the disks shrink considerably. At this stage, structural changes of the lower epidermis occur much faster than in the upper one. The discharged substance is accumulated on the wall surface, and this aids the attachment of adhesive disks on the wall for long periods. In this manner, the shape and structure of the adhesive disk epidermis change drastically from initial growth to the mature stage. Further, the role of electron-dense substance and shrinkage of the disk during attachment has been discussed in Parthenocissus tricuspidata.

• Korean Journal of Plant Tissue Culture
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• v.25 no.4
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• pp.257-261
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• 1998

The repeated subcultures of in vitro plant materials in wasabi became highly vitrified and the capacity for multiple shoot formation from the vitrified plant materials was very low. In order to improve the quality of in vitro propagated planting materials, the experiments were carried out using culture vessels capped with membrane filter(MF). When vitrified shoots were cultured on MS medium with 0.2mg/L BA in the vessels with MF or without MF for 60 days, the shoots in the vessels with MF did not vitrified. In contrast, the shoots grown in the vessels without MF vitrified at 65%. The stomates of vitrified leaves were circular and inflated, whereas those of normal leaves acclimatizated in the vessels with MF were ovate in shape. The hardened shoots were also cultured on MS media without sucrose containing 0.01mg/L IBA in vessels with(photoautotrophic culture) or without(control) MF. Sucrose was necessary for survival of the in vitro plantlets in the vessels without MF. After 20 days of culture, the shoots in the vessels without MF on the sucrose-free media turned yellow and died. But the shoots in the vessels with MF in the sucrose-free media produced a lot of roots. When shoots were cultured on MS medium with 2% sucrose containing 0.01mg/L IBA in the vessels with(photomixotrophic culture) or without(heterotrophic culture) MF, best growth occured in photomixotrophic culture.