The secretory structure of Hypericum perforatum and its relation to hypericin accumulation

Three different kinds of internal secretory structures, secretory cell globules (black dots), secretory cavities (translucent dots) and secretory ducts (translucent streaks) were observed in Hypericum perforatum L. The secretory cell globule, which occurred in flower, leaf and stem, consisted of a core of large secretory cells surrounded by two layers of flattened sheath cells. The secretory cavities were present throughout the lamina and the secretory ducts throughout the newer, both consisted of one or two layers of flattened cells walling an oil chamber or duct. Histochemical and fluorescence microscopy revealed that hypericin was accumulated in the secretory cell globules. Microscopic and ultrastructural observation further demonstrated that hypericin was accumulated in the large central vacuole of the mature secretory cells. Numerous dictyosome, endoplasmic reticulum and small vacuoles were observed in the dense cytoplasm surrounded the large central vacuole. The process of hypericin accumulation in the secretory cells was preliminarily discussed.