Red-light stimulation of prolamellar body recrystallization and thylakoid formation in barley etioplasts.

Abstract

ABSTRACT The etioplasts of fully dark-grown barley leaves exhibit a relatively low frequency of crystalline prolamellar bodies (ca. 16–20%). Brief red-light treatment leads to rapid disruption of all prolamellar bodies followed by a slow reformation in the subsequent dark period. When several red-light treatments are given with intervening 3-h dark periods, a marked increase in the proportion of crystalline prolamellar bodies is seen. It is suggested that this phenomenon may be associated with the regeneration of protochlorophyll. Red-light pretreatment stimulates the formation of granal thylakoids upon subsequent transfer to continuous white light. This response is correlated with the phytochrome-mediated shortening of the lag phase in chlorophyll-synthesis under identical conditions. Regular arrays of hexagonal tubules 16–19 nm in diameter have been observed often in close juxtaposition to the newly forming thylakoid membranes. These may be aggregations of Fraction I protein, although their exact nature and function is at present Unknown.