Fig. 2. Expression of ET1335-GUS in correlation to procambium formation. DIC micrographs of (A,B) lateral views, (C-H) abaxial views. (A,C,E,G) Congruence of ET1335-GUS expression and anatomically recognizable procambium in leaves of various ages as indicated. (B,D,F,H) Enlargements of A,C,E,G, respectively (boxed in C,E,G). Outlined cell boundaries illustrate our recognition criterion for procambium: procambial cells (red) are narrow and approximately twice the length of surrounding GM cells (yellow). Numbers refer to vein orders. Upper right: primordium age in days after germination (DAG). Scale bars: (A,B,D,F,H) 10 µm; (C,E,G) 25 µm.