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, pulve rized in a ceramic mortar, and ground with a buffer and sea sand. Frac tional centrifugation in a discontinuous Percoll gradient enabled sepa ration of amyloplasts in a 40% Percoll layer sandwiched between 20% an d 50% layers. A latency test of marker enzymes for amyloplast, and a p reliminary feeding experiment with radio-labeled substrates for starch synthesis confirmed that the preparation is suitable for use in the s tudy of starch biosynthesis.