Fig. 1.

Chloroplast macrodomain and subdomain rearrangements during senescence. (A) Main ultrastructural changes associated with chloroplast-to-gerontoplast transition. As senescence progresses, mature chloroplasts (left panel) show increased disorganization of the thylakoid membrane system and an increase in the size and number of plastoglobules (middle panel); finally, gerontoplasts (right panel) are characterized by the almost complete loss of thylakoids, highest plastoglobule size, and envelope perforations that allow extrusion of stroma content. (B) Rearrangements occurring during grana unstacking in the chloroplast-to-gerontoplast transition were classified in stages: 1, chlorophyll and LHCII degradation; 2, LHCII migration; 3, formation of PSI–NDH complex. Schemes representing each of the complexes are indicated.