The hda19 mutant has defects in root epidermal cell and ground tissue patterning. Cross-section images show Toluidine Blue-stained root tips of wild-type Columbia (Col) and hda19 mutant at 5 and 8 d old (A and B, respectively), 35Spro:HDA19 (overexpression line) at 8 d old (C), and HDA19pro:HDA19-EGF/hda19 (complementation line) at 8 d old (D). Black arrows indicate darkly stained hair cells (H cells) at N positions, and the red arrow indicates lightly stained nonhair cells (N cells) at H positions. Red asterisks indicate the original cortical cells, and orange asterisks indicate the additional cortical layer. En, Endodermis. Bar in the inset of B = 10 μm; bar in D = 20 μm and applies for all other micrographs.