Ultrastructural changes in plants exposed to extended darkness. A to D, Transmission electron micrographs of leaf cells of the wild type (A), sdp1-4 (B), pxa1-2 (C), and sdp1-4 pxa1-2 (D) before dark treatment. E to G, Transmission electron micrographs of leaf cells of the wild type (E), sdp1-4 (F), and pxa1-2 (G) after 2 d of darkness. H and I, Transmission electron micrographs of leaf cells of the sdp1-4 pxa1-2 double mutant after 2 d of darkness. Plants were 3 weeks old prior to dark treatment. Arrows indicate LDs. Bars = 2 µm.