• Journal of Plant Biotechnology
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• v.40 no.1
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• pp.55-58
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• 2013

Immature embryos of Glycine max L. was cultured on Murashige and Skoog's (MS) medium supplemented with 1 mg/L 2,4-dichlorophenoxy acetic acid (2,4-D). After 6 to 8 weeks of culture, immature embryos produced somatic embryos. Of somatic embryos, two cotyledonary embryo (14%), one cotyledonary embryo (37%), fused cotyledonary embryo (43%), and stunted globular embryos (6%) were observed. The procambial strand of cotyledons originated from circular procambial tissues of lower hypocotyl. The circular procambial tissues were independently divided into one or two procambial strand at the edge of cotyledonary-node, and then connected to each cotyledon to form somatic embryos with one or two cotyledons. When cotyledon was a fused type, the circular procambial strand in lower hypocotyl was continuously connected to the cotyledon. Also, somatic embryos with two cotyledons developed a functional shoot apex with the tunica-corpus structure. In contrast, somatic embryos with one or fused cotyledon formed an abnormal shoot apex without the tunica-corpus structure or with non-dome shape in the inter-cotyledonary area. These results indicated that the variation of cotyledon in somatic embryos is closely related to procambial differentiation and shoot apical meristem development.

• Korean Journal of Plant Resources
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• v.26 no.4
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• pp.511-515
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• 2013

Hypocotyls explants of melon seedling were cultured on Murashige and Skoog's (MS) medium supplemented with 1 mg/L 2,4-dichlorophenoxy acetic acid (2,4-D) and 0.5 mg/L benzyl aminopurine (BA) for 6 weeks to produce somatic embryos. In somatic embryos produced through intervening bright yellow friable (BYF) from the explants, somatic embryos with two-cotyledon (26%) and horn-type cotyledon (74%) were observed. The procambial strand of cotyledons was originated from circular procambial tissues of lower hypocotyls. The circular procambial independently divided into two procambial strand at the edge of cotyledonary-node, and then connected to each cotyledon to form somatic embryos with two-cotyledon. When cotyledon was horn-type, the circular procambial strand in lower hypocotyls would continuously remain connected to the cotyledon. However, somatic embryos with two or horn type cotyledon formed an abnormal shoot apex without the tunica-corpus structure or dome shape in the inter-cotyledonary area. These results demonstrated that the variation of cotyledon in somatic embryos was closely related to procambial tissue differentiation and shoot apical formation.

• Korean Journal of Plant Resources
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• v.12 no.2
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• pp.133-138
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• 1999

The structure of shoot apex in zygotic and somatic embryos of Daucus carota L. cv. Hongshim was observed by using SEM and longitudinal sections. Shoot apex of zygotic embryo was of an inverted boat shape, and these of two, three and four cotyledon somatic embryos were of an inverted boat shape, a pyramid shape and a convex diamond shape, respectively. In zygotic embryo shoot apex is consisted of small cells which are arranged in layers (tunica) and show corpus in central region. In somatic embryos shoot apices are consisted of somewhat large cells which are arranged in irregularly or slight regularly.

• Horticultural Science & Technology
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• v.28 no.6
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• pp.996-1002
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• 2010

Flow cytometry (FCM) was used to measure the ploidy level of three different sports from 'Campbell Early' ($Vitis$ $labruscana$) grape. Results of the study showed different ploidy levels. FCM analysis for 'Campbell Early' grape which contains 2C DNA diploid cells showed single peak around 35-40 while 'Kyoho' grape with 4C DNA tetraploid cells had a different level of 70-80. However, analysis of the sports displayed a histogram with 2 peaks containing both 2C and 4C nuclei. There was no difference in histograms of 2C DNA flesh and pericarp; on the other hand, 4C DNA flesh type of sports had a different histogram from that of the 2C DNA pericarp. Chromosome numbers of diploid ('Campbell Early'), tetraploid ('Kyoho'), and three sports were counted under the microscope. 'Campbell Early' and 'Kyoho' have 38 and 76 chromosomes, respectively. Three different sports are mixoploids with mixtures of diploid and tetraploid cells. Microscopic observations of shoot apical meristems in sports from 'Campbell Early' grape were carried out to determine the type of plant chimera. 'Campbell Early' grape (diploid) and 'Kyoho' grape (tetraploid) showed that both had 2 tunica layers covering corpus cells, while the three different sports had tunica layers showing mostly oblique division. Most cells from 'Kyoho' grape were larger than 'Campbell Early' grape. Cells from L-2 and L-3 layers of the three sports were similar to 'Kyoho' grape in size, although all cells in L-1 surface layer were uniform in size like 'Campbell Early' grape. Results of FCM analysis indicated that both normal and polyploid cells could be intermixed in sports and could become mixoploidy consisting of diploid and tetraploid. All sports used in the tests were periclinal chimera plants with two distinct L-1 and L-2 cell layers. The result of this study suggests that all three sports which originated from 'Campbell Early' grape might be 2-4-4 type chimera formation.

• Journal of Plant Biotechnology
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• v.41 no.4
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• pp.180-193
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• 2014

In plants, a shoot apex has a small region known as the shoot apical meristem (SAM) having a group of dividing (initiating) cells. The SAM gives rise to all the groundabove structures of plants throughout their lifetime, and thus it plays important role in growth and development of plants. This review describes theories to explain the SAM organization and function developed over the last 250 years. Since in 1759 German botanist C. F. Wolff has described firstly the SAM, in 1858 Swiss botanist C. N${\ddot{a}}$geli proposed the apical cell theory from the observation of a large single apical cell in the SAM of seedless vascular plants: however, this view was recognized to be unsuitable to seed plants. In 1868, German botanist J. Hanstein suggested the histogen theory: this concept subdividing the SAM into dermatogen, periblem, and plerome was unable to generally apply to seed plants. In 1924, German botanist A. Schmidt proposed the tunica-corpus theory from the examination of angiosperm SAM in which two parts show different planes of cell division: this theory was proved to be not suitable to gymnosperm SAM, not have stable surface tunica layer. In 1938, American botanist A. Foster described zones in gymnosperm SAM based on the cytohistologic differentiation and thus called it a cytohistological zonation theory. With works by E. Gifford, in 1954, this zonation pattern was demonstrated to be also applicable to angiosperm SAM. As another theory, in 1952 French botanist R. Buvat proposed the m${\acute{e}}$rist${\grave{e}}$me d'attente (waiting meristem) theory: however, this concept was confuted because of its negation of function during vegetative growth phase to central initial cells. Rescent studies with Arabidopsis thaliana have found that formation and maintenance of the SAM are under the control of selected genes: SHOOTMERISTEMLESS (STM) gene forms the SAM, and WUSCHEL (WUS) and CLAVATA (CLV) genes function in maintaining the SAM; signaling between WUS and CLV genes act through a negative feedback loop.