Figure 2.

Effects of nitrate on nodulation in the sunn nlp1 double mutant.

(A–D) Nodule phenotype (A), number of total nodules (B), number of big nodules (≥1 mm) (C), and number of infection threads (D) in wild type (R108), nlp1-1, sunn-6, and sunn nlp1. Plants were grown in a vermiculite and perlite (1:1) mixture and irrigated with 10 mM KCl or KNO₃. Total nodules and large nodules were counted at 3 wpi, and the infection threads were scored at 7 dpi.

(E) Acetylene reduction assay (nM min⁻¹ g nodule⁻¹) of nodules formed on wild-type and nlp1-1, sunn-6, and sunn nlp1 mutant plants (n = 3). Scale bars in (A), 1 mm; error bars show ±SEM. Data points from one representative experiment of three independent experiments are plotted as dots. Asterisks in (B–E) indicate significant differences (two-tailed t-test, ∗P < 0.05, ∗∗P < 0.01, ∗∗∗P < 0.001; ns, not significant).