Pigment Transformations in Leaves of Wheat after Irradiation.

It has been shown that the dark steps in chlorophyll synthesis in wheat leaves following irradiation are completed in about one hour at 22°C. The most evident change is the phytolization of the chlorophyllide a according to Wolff and Price (16). The main part of the protochlorophyll present in darkness is probably unphytolized and active in transformation, while a minor fraction, probably phytolized protochlorophyll remains unchanged after irradiation. It does, however, slowly disappear in darkness, but its further fate has not been elucidated. Pigment analysis of extracts from normal, green leaves, which have been kept in darkness for five hours and afterwards treated in the same way as the etiolated seedlings, reveal that the same kind of transformations also take place here. The conclusion is drawn that the same mechanism in chlorophyll formation is working in both irradiated etiolated leaves and in normal ones, although the relative concentration of unphytolized and phytolized pigments may vary. [ABSTRACT FROM AUTHOR]