• Korean Journal of Plant Tissue Culture
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• v.25 no.1
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• pp.69-74
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• 1998

The somatic embryos of Daucus carota L. cv. Hongshim developed in MS basal medium far 4 weeks had varied number of cotyledons. Palisade and spongy parenchyma of cotyledon were not clearly discriminated in all seedlings developed from the embryos. No independent existence of collateral vascular bundle was observed in all seedlings with various types of cotyledon ; instead, vascular bundles were either interconnected or partially connected with one another. Most of the cotyledonary bases on hypocotyl showed short cylinder structure which encircle plumule. The vascular tissues of cotyledonary bases and nodes of seedlings with jar-shaped or 1 cotyledon were connected in ring forms, showing the pattern of ectophloic shiphonostele, and similar ring form structure was also found in the vascular arrangement of 5 cotyledon seedlings. The vascular bundles of seedlings with 2, 3 and 4 cotyledons in many cases had independently arranged within the cotyledonary bases and nodes, showing the pattern of eustele. In hypocotyl, tetrarch or hexarch xylems prevailed in seedlings with jar-shaped cotyledon or 1 and 5 cotyledon; tetrarch xylems prevailed in 2 cotyledon seedlings; and triarch xylems prevailed in 3 cotyledon seedlings. In most of seedlings, cortex vascular bundles were dispensed in the region from cotyledonary node to hypocotyl, but double vascular bundles were also observed occasionally. In roots, diarch xylems were observed in most of seedlings with 2 cotyledons, triarch xylems in half of seedlings with 3 cotyledons, and diarch xylems in most of the remaining seedlings with the occasional occurrences of tetrarch xylems.