Distribution of NADPH-protochlorophyllide oxidoreductase (POR) in etioplast of etiolated barley leaf was studied by using Western blot analyses of etioplast fractions isolated on a sucrose gradient. When the leaf was exposed to light, POR content decreased in the etioplast inner membrane and prolamellar body sub-membrane fraction while it was simultaneously increased in the stroma. By using 77 K fluorescence spectroscopy analyzes, we found for irradiated etiolated leaf that the POR protein in the stroma was co-localized with chlorophyllide (Chlide) emitting at 678 nm. Relocalization of the POR-Chlide complex induced by irradiation suggests that POR participates in the pigment transport processes during early stages of the thylakoid membrane development. and D. Kovacevic, D. Dewez, R. Popovic.