Fig. 4.

Primary root length (A), total lateral root (LR) length (B), number of laterals (C) and mean lateral root length (D) 7 d after transfer of 8-d-old A. thaliana seedlings to vertical split-root plates, in which the primary root tip was positioned in the bottom zone and the rest of the root system in the top zone. The x-axis values indicate the exposure concentrations (μm) as ‘top zone–bottom zone’. Plants were exposed to CdSO₄, CuSO₄ or ZnSO₄, colour-coded on the figure; black indicates zones with zero exposure. Different letters indicate statistically significant differences (P < 0·05) after one-way ANOVA and Tukey correction (n = 6–14) (ng, no growth detected).