Fig. 4. Expression of Athb8-GUS during development of the first leaf. (A-D) Lateral view. (E-P) Abaxial view. (A-P) DIC microscopy. Arrow in E points to a single Athb8-GUS expressing cell at the onset of 2nd order loop formation. Upper right: primordium age in days after germination (DAG). Lower left: fraction of primordia showing nearly identical features. Scale bars: 25 µm.