Plastid Development in Primary Leaves of Phaseolus vulgaris: The Light-induced Development of the Chloroplast Cytochromes

Etioplasts obtained from the primary leaves of dark-grown bean plants contained cytochromes f, b-559LP and b-563 in a molar ratio of approximately 1.0:2.0:1.5. On illumination of the plants there was a lag of between 10 and 15 h before these cytochromes increased in amount, but after 48 h they had increased from 6- to 10-fold on a per plastid basis. The presence of cytochrome b-559HP in the plastids was first detected after 15 h of illumination, which coincided with the commencement of grana formation and the onset of a number of photosynthetic reactions in the greening leaves. After 48 h of illumination the molar ratio for cytochromes f, b-559HP, b-559LP and b-563 was 1.0:1.2:2.8:2.6. Agranal chloroplasts formed by the exposure of dark-grown plants to intense light flashes contained high amounts of cytochromes f, b-559LP and b-563 but cytochrome b-559HP could not be detected. As the light-induced formation of cytochromes f, b-559LP and b-563 was substantially inhibited by D-threo chloramphenicol, but not by the L-threo isomer, it seems likely that their formation was dependent on 70S ribosomes. Both chloramphenicol isomers gave plastids which lacked cytochrome b-559HP.