Figure 5.

The srk2d/e/i triple mutant shows increased susceptibility to a high external Mg²⁺ concentration. A, Growth phenotypes of the wild type, srk2d/e/i and cipk26/3/9 triple mutants, and the cipk26/3/9/23 quadruple mutant grown under a high external Mg²⁺ concentration. Photographs show representative phenotypes of 18-d-old seedlings grown vertically for 4 d on GM plates and then for 14 d on one-half-strength Murashige and Skoog medium agar plates containing indicated concentrations of MgCl₂. Bars = 1 cm. B, Fresh weight of seedlings treated as described in A. Similar results were obtained in independent experiments; representative data are shown. Bars indicate sd (n = 8). Asterisks indicate statistically significant difference. **, P < 0.01, two-way ANOVA followed by a post hoc Tukey-Kramer multiple comparison test. C, ICP-MS analyses of magnesium, calcium, potassium, and sodium concentrations in aerial parts of plants grown vertically for 4 d on GM plates and then for 12 d on one-half-strength Murashige and Skoog agar plates with or without the addition of 20 mm MgCl₂. For each biological replicate, material from four plants was pooled to make one sample for ICP-MS analysis. Data represent means and sds (n = 6). Orange bars, 20 mm MgCl₂; white bars, control. Asterisks indicate that the corresponding mean is significantly different from the mean value of the wild type within each condition. *, P < 0.05; **, P < 0.01, two-way ANOVA followed by a post hoc Tukey-Kramer multiple comparison test. D, Susceptibility of the srk2d/e/i/cipk26/3/9/23 septuple mutant to high external Mg²⁺ concentrations. Plants were grown as described in A. Bars = 1 cm. E, Fresh weight of seedlings treated as described in D. Similar results were obtained in independent experiments; representative data are shown. Bars indicate sd (n = 8). WT, Wild type.