Prolamellar bodies (PLBs) isolated from etiolated wheat seedlings were studied 
with the use of atomic force microscopy (AFM), transmission electron microscopy 
(TEM) and fluorescence spectroscopy. With AFM, PLBs were seen as spherical 
structures about 1-2μm in diameter, more elastic than mica and poly-l-lysine 
substrate. TEM analyses confirmed that PLBs of wheat leaf etioplasts also had an 
average diameter of appr. 1μm. Illumination induced the photoreduction of 
photoactive protochlorophyllide (Pchlide), i.e. Pchlide bound to 
protochlorophyllide oxidoreductase, which was shown in fluorescence spectra. The 
photoreduction was followed by the disruption of PLB structures, which started 
with the enlargement of PLB spheres and then their fragmentation into small 
balls as seen with AFM. Light-induced vesicle formation and the outgrowth of 
lamellar (pro)thylakoid membranes on the PLB surface were also confirmed by TEM 
analyses, and resulted in the apparent enlargement of the PLB diameter. The 
blue-shift of the fluorescence emission maximum of chlorophyllide observed for 
PLBs at room temperature after Pchlide photoreduction was completed within 
25min. However, structural changes in PLBs were still observed after the 
completion of the blue-shift. The incubation of PLBs in darkness with HgCl2 also 
resulted in PLB enlargement and a loosening of their structure. AFM provides a 
unique opportunity to observe PLBs at a physiological temperature without the 
necessity of fixation.