Studies on The Greening of Dark-Grown Bean Plants II. Development of Photochemical Activity

Abstract

A study of the photochemical activity of plastids isolated from etiolated bean leaves which had been illuminated for increasing periods was undertaken. Proplastids isolated from etiolated leaves were inactive in the Hill reaction. Photochemical ferricyanide reduction was obtained with plastids isolated from etiolated leaves which had been illuminated for 6 hr. The reduction increased to a maximum value of 400 p.lloles ferricyanide/mg chlorophyll/hr after 10 hr of illumina· tion and thereafter decreased to 300,umoles ferricyanidejmg chlorophylljhr for mature bean chloroplasts. Plastids isolated from etiolated leaves illuminated for 16 hr reduced nicotinamide adenine dinucleotide phosphate (NADP) at a rate less than half that of mature chloroplasts, while B·hr plastids showed no NADP reduction.