• Proceedings of the Botanical Society of Korea Conference
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• 1999.07a
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• pp.69-73
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• 1999

In plants as well as in other multicellular organisms, programmed cell death plays essential roles in the abortion or formation of specific cells and tissues during development to organize the plant [11, 15, 18]. A typical example of developmentally programmed cell death in plants is the death during differentiation of tracheary elements which are components of vessels and tracheids, a water-conducting system. The programming of cell death during tracheary element differentiation has been revealed to be unique to plant cells by using the in vitro Zinnia mesophyll cell culture system. In particular, new biosynthesis of autolysis-related enzymes such as cysteine proteases and nucleases, their accumulation of the vacuole and the programmed collapse of the vacuole are essential to the death of tracheary elements and differ greatly from the process of the apoptotic cell death in animals.

• Journal of Plant Biology
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• v.36 no.1
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• pp.35-42
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• 1993

This study deals with the effect of dwarf growth for the wood and the structural changes of cambium in Pinus koraiensis subjected to water stress. The length and wall thickness of tracheary elements in dwarf trees was shorter and thicker than that in normal trees. The redial width and cell number of the annual rings are narrower and smaller in dwarf trees than those in normal trees. In serial tangential sections, the frequency of anticlinal division is low and loss of cambial initials is small in dwarf trees. The length of cambial initials in water deficit, trees are slightly shorter than that in normal trees, and the instructive growth of cambial initials during differentiation of xylem mother cells is inactive in dwarf trees. Thus, it is interpreted that the shortening of tracheary elements in dwarf trees is due to the fact that the length of cambial initials are shortened and the intrusive growth of those during differentiation of xylem mother cells is inactive. The structural variations in the wood of naturally occurring dwarf trees are similar to those of trees subjected to artificial water stress. Therefore, it is suggested that the variation of xylem element in dwarf trees are related to water conditions.

• Journal of Plant Biology
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• v.34 no.1
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• pp.9-18
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• 1991

This study deals with the effect of dwarf growth on xylem structure, especially on the dimension of xylem elements described for 12 species of naturally occuring dwarf trees. The length and tangential diameter of tracheary elements and fibers in dwarf trees appear to be shorter and narrower than those in normal trees. Radial width and cell number of the same annual rings are narrower and smaller in dwarf trees than those in normal trees. Height of rays in dwarf trees is lower than that in normal trees. Dwarf conifers appear to have higher ratio, of latewood to earlywood than that in normal trees. In the hardwood species studied, mesomorphy of vessel elements is lower in dwarfs than that in normal trees. It can be concluded that this dwarf growth occurs as a result of extremely slow growth by environmental stress such as water deficiency.ciency.

• Journal of the Korean Wood Science and Technology
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• v.34 no.6
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• pp.1-11
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• 2006

Grafted tissues were investigated using various microscopic techniques. Pinus thunbergii was used as stock and scion and autografted by cleft graft method. Histochemically, grafting processes can be proceeded by four stages: 1) formation of necrotic layer, 2) proliferation of callus, 3) development of neo-cambium from callus, and 4) restoration of new vascular xylem. Necrotic la yer composed of pectin and lignin was gradually degraded during grafting process and disappeared when new union was formed between stock and scion. A large number of starch and lipid bodies in the cytoplasm were also gradually degraded during grafting process and disappeared at the grafting interface. Nucleus and plasmodesmata were not changed. Bubble-like callus was generated from all living parenchyma cells and from the callus. The tracheary elements differentiated from the callus had either reticulate or pit-like thickenings in the secondary walls with bordered pits. Secondary cell wall thickening occurred toward filing to the void parts between reticulated secondary wall. Tracheids formed in the secondary xylem were short with irregular wall thickness. New secondary xylem cells with swirled shapes, which developed in graft union were oriented horizontally and obliquely to axis of the stem.

• Journal of Plant Biology
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• v.37 no.3
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• pp.371-380
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• 1994

To determine the patterns and the levels of expression of the cauliflower mosaic virus (CaMV 35S) promoter and the rice actin 1 (Act1) promoter in rice, transgenic rice plants containing CaMV 35S-$\beta$-glucuronidase (GUS) and Act1-GUS constructs were generated and examined by fluorometric and histochemical analyses. The fluorometric analysis of stably transformed calluses showed that the activity of the rice Act1 promoter was stronger than that of the CaMV 35S promoter in rice cells. In a histochemcial study of the transgenic rices, it was shown that the GUS activity directed by the CaMV 35S promoter was localized mainly in parenchymal cells of vascular tissues of leaves and roots and mesophyll cells of leaves. These results are similar to those of potato, a dicot plant. In contrast, rice plant transformed with Act1-GUS fusion construct revealed strong GUS activity in parenchymal cells of vascular tissue, mesophyll cells, epidermal cells, bulliform cells, guard subsidiary cells of leaves and most cells of the root, suggesting that the rice Act1 promoter is more constitutive than the CaMV 35S promoter. It was also confirmed that in both types of transgenic rice little or no staining was localized in metaxylen tracheary elements of vascular tissue from leaves or roots. These results indicate that the rice Act1 promoter can be utilized more successfully for expression of a variety of foreign gene in rice than the CaMV 35S promoter.

• Korean Journal of Plant Tissue Culture
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• v.26 no.2
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• pp.127-132
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• 1999

Protoplasts were isolated from the leaf mesophyll tissue of in vitro 4-weeks-old Arabidopsis thaliana and cultured in MS liquid medium supplemented with 2.0 mg/L NAA, 0.5 mg/L BAP and 9% mannitol in the dark at $25^{\circ}C$. When protoplast-derived microcolonies were dehydrated, the frequency of callus induction enhanced approximately 7-fold higher compared with non-dehydrated microcolonies in CP medium. Fifty callus lines were selected from dehydrated microcolonies. Shoots were efficiently initiated from the green spots of the selected shoot forming calli cultured on MS regeneration medium supplemented with 0.05 mg/L IAA, 7.0 mg/L 2-iP and 30 g/L sucrose under continous illumination for 4 weeks. Shoot regeneration frequencies (calli regenerating at least one shoot) were 3.5%~56%. Histological observations of shoot forming callus revealed that tracheary elements initiated from inner compact cells, and that meristemoids developed to shoot primordia and shoots. Roots were induced from these regenerating shoots on MS medium without phytohormones. These regenerants were successfully transplanted into potting soil. Morphological characterization of 50 protoplast-derived plants showed that the frequency of normal type was 78%.