榕樹氣根之研究（1）根帽的構造

The Study on Aerial Root of Ficus microcarpa L. f. (1) The structure of root cap

榕樹（Ficus microcarpa L. f.）莖上發育出許多細長的氣根，此氣根具有根帽，但缺乏根毛。若由中央縱切面觀察，榕樹氣根尖端屬於開放型的分生組織構造。根帽中軸是8～15層分裂自根帽源的活薄壁細胞，而位於根帽周圍之細胞則會瓦解、脫落。根帽源之細胞具有一帶明顯核仁之大的細胞核及許多小液胞，其顆粒體為原顆粒體。在根帽細胞之分化過程中，可確認顆粒體（包括澱粉粒之形成與瓦解）、粒線體及內質網等胞器微細構造之變化。榕樹氣根的根帽中軸細胞之胞器的分佈不具極性。

Numerous thin, adventitious aerial roots develop on the stems of Ficus microcarpa L. f., They bear root caps, but lack root hairs. In this paper, the tips of aerial roots of Ficus microcarpa were investigated by means of light microscopy, scanning electron microscopy and transmission electron microscopy. In the median longitudinal section, the meristem of aerial root shows an open type of construction. The cap columella consists of 8-15 layers of living parenchyma cells derived from the calyptrogen. The peripherial cells of the root cap are collapsed and sloughed off. The cells of calyptrogen have a large nucleus with a pronounced nucleolus and many small vacuoles. The plastids are proplastids. When the cells of the cap leave the initial zone, the alteration in the ultrastructure of plastids including the build-up and the breakdown of starch grains, mitochondria and endoplasmic reticulum can be recognized. The columella cells (statocytes) of aerial root cap in Ficus microcarpa show no strict ultrastructural polarity.