Abstract: It was proved by electron microscopic observation that the secretory cavity which was found to be formed schizogenously was consisted of an oil chamber lined with epithelial cells and Sheath cells in the fruit of Zanthoxylum bungeanum Maxim. The ultrastructure of the secretory cavity in different stages of development showed that the essential oil started to be accumulated in the oil chamber when it appeared in the form of oil droplets in the plastids and cytoplasm of the epithelial cells. Based on the character of changes in various organdies, the authors inferred that the plastids were the main organdie where oil was synthesized. Endoplasmic reticulum participated in the process of oil synthesis and oil transportion, while mitochontrion was the energy provider. It seems that oil droplets were synthesized by the plastids in the sheath cells and were transported to the epithelial cells where oil was accumulated. The epithelial cells then excreted the oil droplets in two ways into the oil chamber for accumulation. In the mature secretory cavity owing to the functional change of the plasfids, protein crystals and starch grains were also found in the plastids.

Key words: Secretory cavity, Zantharylum bungeanum, Fruit, Ultrastructure