Fig. 4

Measured concentrations (µg cm⁻³) of Mg, P, K and Mn per unit volume and the estimated concentrations of Mg, P, K and Mn per unit tissue water (mM) and per unit dry weight (µg g⁻¹). Measured concentrations (µg cm⁻³) of Mg, P, K and Mn per unit volume of tissue obtained by laser micro-dissection of the stele and cortex of barley roots (a). Estimated concentrations of Mg, P, K and Mn per unit tissue water (mM) and per unit dry weight (µg g⁻¹) of stele and cortex together with the resulting stele:cortex ratio (b). The concentrations were calculated assuming a fresh root tissue density of 1 g cm⁻³ and assuming a dry matter content of 7% in the roots. Stele and cortex were microdissected, collected and pooled from 3 cross-sections and subsequently digested and analyzed by ICP-MS. Data was tested with a one-way ANOVA t-test, and the asterisks indicate significant differences (*P ≤ 0.05; **P ≤ 0.01; ***P ≤ 0.001), between the tissues, for each element (n = 4)