[Structural changes of DNA-containing areas in etioplasts during plastid division]

By means of serial sections of etioplasts of Hordeum vulgare the spatial arrangement of nucleoplasma-like regions before and during plastid division was investigated. 1. After aldehyde-osmium fixation the etioplasts exhibit areas of low electrondensity containing DNA-fibers 50-100 Å thick which are preferentially stained by uranyl-acetate. 2. As could be shown by a series of thin sections, etioplasts 2-3 μ long predominantly contain only one polymorphous nucleoplasma-like region which may be split in such a fashion as to show more than one of these low electron density areas in a single section. 3. Two DNA-containing nucleoplasma-like regions could be demonstrated in enlarged plastids (5-6 μ in length). It is tentatively concluded that the original regions are divided before plastid division. 4. In some cases the DNA-containing area showed a parallel arrangement to the constriction of the dividing plastid. In these cases it is assumed that the DNA-containing area is distributed between the daughter plastids during plastid division.