During continuous illumination of etiolated leaves of Phaseolus vulgaris L. ferredoxin–NADP reductase activity increased exponentially after an initial lag period of 10–15 h while the chlorophyll/reductase molar ratio increased to a constant value of 750±50 after approximately 15 h illumination. The same ratio was obtained when greening occurred at low light intensity.

The synthesis of ferredoxin–NADP reductase was influenced by phytochrome activity as indicated by its response to red/far-red light treatments. The effects of D-threo chloramphenicol and lincomycin indicated that synthesis of this enzyme did not involve translation on chloroplast ribosomes. The data are discussed in relation to the development of ferredoxin and plastocyanin in greening bean leaves.