Figure 2.

Transmission electron micrographs showing the morphological changes in D. tertiolecta placed in the darkness. Chl, Chloroplast; LD, lipid drops; Mit, mitochondria; N, nucleus; NS, nuclear space; P, pyrenoid; S, starch. A, Normal vegetative cells grown in the light. B and C, Cells after 1 and 2 d in darkness, respectively. Note the movement of chromatin from the nucleolus (arrows). D, After 3 d in darkness, chromatin has moved to the nuclear membrane, and the nucleolus has disappeared. Chloroplastic thylakoids are disorganized, but none of the organelles show evidence of disintegration or swelling. E, After 4 d in darkness, the nucleus is no longer observed. F, After 5 d in darkness, cells have lysed. Horizontal bar = 1 μm.