Nonphotoconvertible Protochlorophyllide in Etiolated Tissue Lacking Prolamellar Bodies

Etiolated tobacco seedlings have an in vivo absorption spectrum with a maximum at 637 nm and a shoulder in the 650-nm region. Upon exposure to light, the 650-nm region diminishes, and a new peak at 675-680 nm appears It is probable that the 650-nm absorbing pigment is the precursor for the longer-wavelength form of the pigment. Dark-grown cultured tissue of tobacco has an absorption spectrum identical with that of the etiolated seedlings, but no photoconversion from the short- to the longer-wavelength pigment form occurs on exposure to light. The plastids in the cultured tissue differ from those in the seedlings in that they lack prolamellar bodies Since the protein-pigment complex is normally associated with the prolamellar body, these membranes may be necessary for the photoreduction of the protochlorophyllide to chlorophyllide in this system.