CHARACTERIZATION OF INTRAVACUOLAR PIGMENTED STRUCTURES IN ANTHOCYANIN-CONTAINING CELLS OF SWEET-POTATO SUSPENSION-CULTURES

Intravacuolar pigmented structures occurred in anthocyanin-producing c ultured cells of sweet potato (Ipomoea batatas) were characterized. Fo rmation of the pigmented structures in sweet potato cells was induced by transfer of callus cultured in 2,4-D containing agar medium into 2, 4-D free liquid medium under continuous illumination. These structures were found in the vacuoles. The pigmented structures were isolated fr om the protoplasts by precipitation in 60% (w/w) sucrose after centrif ugation. Electron microscopic observations of the anthocyanin-containi ng cultured cells showed these structures had neither membrane boundar y nor internal structures, and were found as strongly osmiophilic glob ules in vacuoles. Numerous small osmiophilic globules were observed in central vacuoles at the early stage of anthocyanin accumulation, but not found in cytoplasm. Similar pigmented structures in vacuoles were also formed by treatment with neutral red. These observations indicate that these pigmented structure is the high density and insoluble glob ules highly concentrated with anthocyanin, which was synthesized in cy toplasm and transported to the central vacuoles.