DNA REPLICATION AND SYNTHESIS OF DNABINDING PROTEINS IN THE CHLOROPLASTS OF A CALLUS CULTURE

Continuous labelling of callus with H-thymidine results in intermittent peaks of H-DNA per chloroplast, showing synchrony of division. The increase in H-DNA could be due to several replication rounds, and the drop to successive plastid divisions without intervening DNA synthesis. The level of DNA-binding proteins in the chloroplast parallels the peaks of plastidal DNA synthesis; such proteins could hence comprise factors necessary for plastid multiplication in tissue cultures