Figure 5.

Irreversible MR growth arrest of Ct-1 in low K is caused by cell death in the apical meristem. A and B, Col-0 (A) and Ct-1 (B) seedlings (n = 8–15 per genotype per condition) were grown on control (black lines, circles) and low-K (dashed lines, triangles) media or on low-K medium resupplied with 2 mm KCl for 1 h at 3 DAG (blue lines, circles), 6 DAG (green lines, squares), or 9 DAG (red lines, diamonds). MR growth in Ct-1 could not be recovered when resupply occurred later than 6 DAG, whereas in Col-0, MRs continued to elongate in all conditions. C to F, Seedlings starved for K were stained with propidium iodide solution 6 DAG and observed with a confocal microscope. Representative images are shown for MR apices of Col-0 (C) and Ct-1 (D) as well as LR tips (Col-0, E; Ct-1, F). Cell lesions are highlighted with white arrows. Bar = 0.1 mm.