The loss of the <i>AtERF4</i> gene leads to an increased Fe deficiency response.

<p>(A) The Fe and Mg content of WT and mutant <i>erf4</i> root under Fe-sufficient and Fe-deficient for 5 d. (B) The Fe reductase activity of WT and mutant <i>erf4</i> root under Fe-sufficient and Fe-deficient conditions for 5 d. Bars represent means ± SE of three replicates. Different letters represent statistically different means at <i>P</i> < 0.05 (one-way ANOVA with a Duncan post-hoc test). (C) The qualitative analysis of the rhizosphere H₂ of WT and mutant <i>erf4</i> under Fe-sufficient and Fe-deficient conditions for 5 d, scale bar = 0.8 cm. (D) The transient H⁺ flux of WT and mutant <i>erf4</i> root hair under Fe-sufficient and Fe-deficient conditions for 5 d. (E) Relative expression of the Fe uptake-related genes <i>AtIRT1</i>, <i>AtHA2</i> and <i>AtFIT</i> in WT and mutant <i>erf4</i> under Fe-sufficient and Fe-deficient conditions for 2 d. Bars represent means ± SE of three replicates. Different letters represent statistically different means at <i>P</i> < 0.05 (one-way ANOVA with a Duncan post-hoc test).