Fig. 3. Phenotype observed at lateral sector boundaries in the epidermis. Epidermal and mesophyll genotypes are indicated to the left and right of each sector boundary (i.e., wt/wt means the epidermis and underlying mesophyll are both wild type; wt/mut means the epidermis is wild type and the underlying mesophyll is mutant, etc.). White asterisks indicate wild-type guard cells containing chloroplasts. Black asterisks indicate mutant guard cells lacking chloroplasts. Black arrows indicate oblique cell walls immediately adjacent to marked, wild-type cells. Note that the wild-type cells adjacent to these walls are of normal shape. White arrows indicate aberrantly divided wild-type cells. For regions where the interval between wild-type and mutant stomatal files is 2 or fewer cell files, numbered black arrowheads indicate the distance between the two files. (A,B) Lateral sector boundaries in the epidermis coinciding with lateral boundaries in the underlying mesophyll. Note the sharp transition between wild-type and mutant-appearing cells regardless of the distance between the stomatal files marking the boundary region. (C) Lateral sector boundary in the epidermis overlying wild-type mesophyll. Note that the phenotypes of mutant cells overlying wild-type mesophyll (lower right quadrant) are comparable to those of mutant cells overlying mutant mesophyll in A, B and D. (D) Lateral sector boundary in the epidermis overlying mutant mesophyll. Note that wild-type epidermal cells overlying mutant mesophyll (left half) appear as regular as those overlying wild-type mesophyll in A, B and C. Scale bar in A:100 µm for A-D.