White potato tuber tissues (Solarium tuberosum, vars. King Edward and Craigs Royal), contained carotenoids but did not contain either protochlorophyll or chlorophyll. On illumination of tuber discs, the accumulation of chlorophyll a and chlorophyll b began simultaneously after 19 hours and continued for 3 weeks. This greening process was associated with a synthesis of galactolipids.
Light of intensity 750 1× was sufficient to induce maximum greening and to cause greening throughout the disc. Blue light was more effective than orange or green light.
Chlorophyll accumulation in tuber discs was inhibited by cycloheximide, chloramphenicol, lincomycin, δ-aminolaevulinic acid, benzyladenine, and high concentrations of sodium arsenate and potassium cyanide. It was unaffected by 2,4-D, laevulinic acid and malonic acid. When green discs were returned to darkness, the total chlorophyll content remained constant over a period of 7 days but the ratio of chlorophyll a to chlorophyll b decreased.
These results are discussed in terms of the control mechanisms and differentiation processes involved in the development of chloroplasts from amyloplasts.