PREPARATION OF AMYLOPLASTS FROM SWEET-POTATO CALLUS-CULTURE

Culture conditions for sweet potato callus were manipulated to enhance starch content. Tissue cultures were frozen in liquid nitrogen, pulverized in a ceramic mortar, and ground with a buffer and sea sand. Fractional centrifugation in a discontinuous Percoll gradient enabled separation of amyloplasts in a 40% Percoll layer sandwiched between 20% and 50% layers. A latency test of marker enzymes for amyloplast, and a preliminary feeding experiment with radio-labeled substrates for starch synthesis confirmed that the preparation is suitable for use in the study of starch biosynthesis.