Fig. 4

Malate efflux from the apices of various root types. Data are presented as a malate efflux per root apex, or b malate efflux normalized to the tissue surface area. Data are mean ± SE (n = 3–10). Lowercase letters above the bars indicate significant differences (P < 0.05) between the root types within the control or +Al³⁺ treatments, and asterisks above the +Al³⁺ bars indicate significantly more malate exudation (P < 0.05) than the counterpart root type in the control treatment. Equal variance tests failed so data were natural log-transformed prior to two-way ANOVA with Bonferroni post hoc test