Fig. 5. Mosaic analysis of brk2. (A) DIC image of epidermal peel illustrating sector boundaries of types A and B (Fig. 4B). (B) Same field of view as in A but showing chlorophyll autofluorescence in wild-type guard cells. (A,B) White + signs indicate wild-type guard-cell pairs; black minuses indicate mutant guard-cell pairs in an adjacent cell file. Lobe formation in brk2 mutant epidermal cells is not rescued by adjacent wild-type epidermal cells or underlying wild-type mesophyll. (C) DIC image of a glue impression showing junctions between brk2 and wild-type pavement cells; black arrows indicate areas where the lobes of a wild-type cell appear to have grown over the top of an adjacent, unlobed mutant cell. (D) DIC image of an epidermal peel showing four mosaic stomata, two having a wild-type subsidiary flanking brk2 mutant guard cells (white arrowheads), and two having a brk2 mutant subsidiary flanking wild-type guard cells (black arrowheads); the upper one of these brk2 subsidiary cells is abnormal. Scale bars: A, 100 µm; C, 50 µm.