Figure 3.

dal1 mutant of Arabidopsis. (A and B) Two-month-old dal1 mutant plants are shown. Mutant plants from the same seed stock were grown in vitro in six Petri plates, but only plants from a single plate began to develop greenish young leaves (B). The only apparent difference between plants from these different plates is that in B plants are vitrified. The ultrastructure of plastids from mutant plants (D and F) compared to that of the wild type (C and E). Plants were either grown on agar-solidified Murashige and Skoog medium supplemented with 20 g/liter of sucrose (C and D) or grown in the same, but liquid medium on a gyratory shaker (E and F). In plastids of the dal1 mutant a membranous structure resembling thylakoids can be observed (F, but not in D). General morphology of the leaf cells for dal1 (H and J) compared to that of wild type (G and I). Young leaves of the plants grown on agar plates (G and H) or fully expanded leaves of plants grown in a liquid medium (I and J) were sectioned after imbedding into vinylcyclohexene dioxide (Spurr mixture). In the mutant, no palisade parenchyma cells developed and cells are more rounded. [Bars = 2 μm (C–F), 50 μm (G–H), and 100 μm (I–J).]