Figure 1.

Changes to radial anatomy under low phosphate are limited to changes in cortex and hair-cell number. Schematic diagram showing the radial organization of tissues in the Arabidopsis root. Concentric rings of tissues can be seen radiating out from the central vascular cylinder; trichoblast positions in epidermal cells at the cleft between two cortex cells can be seen (light blue). Layers of middle cortex can be seen beginning to form at the xylem poles (orange). Representative images of high Pi (Left) and low Pi (Right) treated roots in transverse section show how the radial organization differs between treatments, scale bar = 50 μm, Bar charts showing number of cells files in each tissue visualized in confocal microscope cross sections for two phosphate treatments: “high P” (1 mM), “low Pi” (50 μM). Roots of seedlings growing on high Pi (1 mM), or low Pi (50 μM) have, on average, 8 and 12 cortex cell files respectively (p ≤ 0.001). This change corresponds to a change in the average number of hair position epidermal cell files (H cells) of 8 to 11 (**p ≤ 0.001).