Fig. 4.

Effects of nitrate on nodulation in the nrsym1 har1 double mutants. a The number of infection threads in the har1-7 mutants and the nrsym1-1 har1-7 double mutants (n = 11–12 plants). Plant growth conditions were the same as those shown in Fig. 1c. b The number of nodules and (c) maximum nodule diameter (mm) in WT, the nrsym1-1 mutants, the har1-7 mutants, and the nrsym1-1 har1-7 double mutants grown in the presence of 0 or 10 mM KNO₃ at 21 dai (n = 9–12 plants). d Acetylene reduction activity (ARA; μmol h⁻¹ per g nodule) of nodules formed on the har1-7 mutants and the nrsym1-1 har1-7 double mutants (n = 4 plants). Plant growth conditions were the same as those shown in Fig. 1e. e Nodulation and nodule numbers of plants derived from shoot–root grafts having WT, nrsym1-1, and har1-7 genotypes. Plants were grown in the presence of 10 mM KNO₃ for 21 dai (n = 13 plants). Arrowheads indicate mature nodules. *P < 0.05 by Student’s t-test. ns, not significant. Degrees of freedom are shown above the t-values (a–d). Columns with the same lower-case letter indicate no significant difference (Tukey’s test, P < 0.05; e). Error bars indicate SEM. Scale bars: 1 mm (c); 2 mm (e)