Development and ageing of etioplast structures in dark grown leaves ofAvena sativa (L.)

Summary Etioplasts of dark grown plants contain a large paracrystalline prolamellar body (PLB) and, attached to this there are prothylakoid membranes (PTs).PLB-tubules inAvena are composed mainly of two saponins and include only a low percentage of other lipids, protochlorophyll(ide) and proteins.Following the development of etioplasts in darkness from the very beginning until plants loose turgescence one can observe marked changes in ultrastructure. In the early stage of development predominantly PTs are seen in small etioplasts. Wide-type PLBs are small. After eight days there is a well developed stage with the well-known big and highly crystalline PLBs, which are connected to many long PT-membranes. After 13 days the PLBs are not significantly changed, while number and length of PTs are strongly reduced.These morphological observations are quantified by measurements of PLB-area and PT-length per plastid section. Saponin content as a marker for PLB-tubules and protochlorophyll(ide)-content as a marker for PT-membranes were measured. Both methods of determination show in good agreement a peak of development for PTs around day 6–7, and for PLBs around 9–10. Beginning senescence affects PT-membranes and PChl(ide) strongly, while saponins resp. PLBs persist better. These results are presented in view of thylakoid formation during greening, starting from the different etioplast stages.Abbreviations Chl(ide) chlorophyll(ide) - EM electron-microscope - PChl(ide) protochlorophyll(ide) - PLB prolamellar body - PT prothylakoid - TLC Thin layer chromatography A preliminary report has been presented at the V. Intern. Congress on Photosynthesis at Chalkidiki, Greece 1980.