台灣蝴蝶蘭根和葉的形態與解剖的特性

Characteristics of Morphology and Anatomy in Root and Leaf of Phalaenopsis amabilis

台灣蝴蝶蘭（Phalaenopsis amabilis var. formosana）以解剖、光學顯微鏡及穿透式電子顯微鏡觀察其根和葉之形態及其內部微細構造，供瞭解其生長習性與CAM型植物特性之參考。蝴蝶蘭具著生根，外層有2～3層已木質和木栓化的根被，可即時貯存水分。根被內層緊鄰一層外皮層，其細胞的外切線和經線細胞壁連續性加厚，可調節根部水分的吸收，它與根被皆具防止水分往外散失之功用。根部的皮層細胞含葉綠體及澱粉粒，根表皮上的白斑狀構造稱為通氣組織或被裂孔（pneumathode），為氣體交換之重要管道。根之內皮層細胞具內外切線和徑線細胞壁連續性加厚，可防止已進入維管束的水分往外散失；穿插於厚壁性內皮層細胞間之薄壁通過細胞與根部維管束的韌皮部相對應，似有利養分及水分的橫向運輸。蝴蝶蘭為厚葉性CAM植物，上表皮及下表皮氣孔密度各為8.0～9.5/mm2及15.3～21.0/mm2。氣孔外部形成外側角質突出物，可防止水分從氣孔散失。表皮細胞覆有一層厚的角質，氣孔外圍大致與4～5個表皮細胞緊鄰。葉肉細胞內同時具有葉綠體和一個巨大的液泡，其細胞之間隙大，使厚葉的內部細胞間方便進行氣體交換。未完全展開的葉片其葉綠體祗貯存油滴，成熟葉片內之葉綠體則充滿澱粉粒及油滴。

Morphology and anatomy in root and leaf of Phalaenopsis amabilis were observed by microscope and TEM. The root has 2 ~ 3 layers velamen with lignified and suberized cell walls and one layer exodermis around the cortex. The mature velamen cells are vacuolated structures and pneumatodes are present in the velamen. The function of these structures is to enable gas exchange during the periods when the root is saturated with moisture. The V- shaped cells of the exodermis situated at the inner edge of the velamen develop secondary wall thickenings in the radial wall and outer tangential wall. The structure of exodermal cells are considered to play an important role in regulation of water absorption. The cortical cells store some starch grain in the cytoplasm and water in the large vacuole. The outer layes of the cortical cells contain more chloroplasts. The enodermis which form the innermost sheath of the cortex are continuous thick-walled cells. Whereas the thick-walled endodermis are constantly interrupted by the thin-walled passage cells, at the place where are exactly opposite to the phloem pole that is suggested to have relations with the nutrient and water transportation of cross section in the root. Phalaenopsis amabilis is CAM plant with thick leaves. The stomata densities of adaxial side and abaxial side in the leaf are 8.0 ~ 9.5/mm2 and 15.3 ~ 21.0/mm2, respectively. There are some protuberance from cuticle of the, epidermal surface. The outer cuticular ledges form at the outer cavity of stomata. These structures are protection and reduction in loss of water from the stomata and epidermis. There are some inter cellular space in the mesophyll that is beneficial to gas exchange. In the mesophyll cells, a large vacuole and chloroplasts are localized in the same cells. The chloroplast of mature leaf stores some starch grains and plastoglobuli, but in immature leaf, the chloroplast only stores plastoglobuli.