Figure 1 Legume nodulation and autoregulation. A) Soybean plants grown in nitrogen-poor conditions. Wild-Type (WT) plants form functional root nodules when inoculated with compatible, nitrogen-fixing, Bradyrhizobium japonicum. Non-nodulating mutant plants are unable to form nodules (nod^-) and supernodulating mutant plants (nod⁺⁺) are unable to regulate the number of nodules they form. B) Roots of wild-type (WT) and supernodulating mutant (nod⁺⁺) common bean plants exhibiting mature nodule structures.