AtCHR23 over-expression affects cell elongation. (A) Confocal images of 6-day-old Col wild-type and AtCHR23-4ov mutant roots grown at 23°C in long day conditions stained with propidium iodide. Arrows indicate the quiescent center, arrowheads indicate the boundary between the proximal meristem and elongation zone of the root. Scale bar: 50 μm. (B) Number of cells (± SD) counted in meristem (left) and mean (± SD) meristem length (right) in Col wild-type and AtCHR23-4ov mutant. (C) Mean (± SD) length of fully elongated cells in elongation zone (left) and mean (± SD) length of the elongation zone (right) in Col wild-type and AtCHR23-4ov mutant. Asterisks indicate significant differences from the wild type: ***, P < 0.001.