Fig. 1. Nitrate inhibits induction of symbiotic cytokinin biosynthesis.

A The root zone which was susceptible to nodule initiation at time of inoculation was used for qRT-PCR and cytokinin analysis. B–E Relative transcript abundance of selected cytokinin biosynthesis genes by qRT-PCR 1 and 2 days post inoculation (dpi) with M. loti in the absence and presence of 5 mM KNO₃. Ubiquitin is used as a reference gene. E, F Cytokinin-free base content (iP and tZ) analysed in mock or 2 days post inoculation with M. loti in the absence and presence of 5 mM KNO₃. Bars show mean ± SE for the n value shown on each bar. Significant differences among different conditions are indicated by letters (p < 0.05) as determined by ANOVA and Tukey post-hoc testing for B–E. Pairwise P-values as determined by Tukey testing are available in the Source Data file. Significant differences between nitrate presence and absence conditions as determined by Wilcoxon rank-sum test is indicated by the annotated P values in F, G.