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KMID : 0381920100400020101
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Korean Journal of Microscopy
2010 Volume.40 No. 2 p.101 ~ p.108
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Developmental Patterns of Glandular Trichomes in Leaves of Vitex negundo
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Park Jae-Young
Kim In-Sun
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Abstract
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Vitex negundo is an aromatic plant which releases a unique scent due to the presence of essential oil stored presumably within glandular trichomes. The focus of this research was to study developmental patterns of glandular trichomes in Vitex negundo leaves using electron microscopy. There are two types of glandular trichomes which develop on the leaf epidermis of Vitex negundo, peltate glandular type (PT) and capitate glandular type (CT). Structural features differ significantly depending on size and density, formation of secretory cavity, plastid, etc during developmental stages. In young leaves, undifferentiated PTs are densely distributed in the upper epidermis, but are not externally exposed in the lower epidermis because they are covered by non-glandular simple trichomes. Upon leaf development, PTs and CTs show clear structural differentiation in the upper and lower epidermis. PTs are composed of up to eight head cells (ca. 35~40 μm) and one stalk cell (ca. 5 μm), while CTs are composed of four head cells (ca. 10~15 μm) and 1~2 stalk cells (ca. 10 μm). Although secretory cavities develop on the secretory head cells, their size, structure, and formation proceed very differently depending on trichome type. In early development of PT, a large cavity with numerous secretory vesicles form rapidly from the head cells. In CT, however, only a small secretory cavity is formed, slowly relative to PT, without secretory vesicles. The PTs are considered to play an important role in releasing the aromatic components of Vitex negundo.
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KEYWORD
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Developmental pattern, Electron microscopy, Glandular trichomes, Leaf, Vitex negundo
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