Phenotype of nip and wild-type (A17) plants 15 dpi with S. meliloti. Plants were grown in aeroponic chambers as described in “Materials and Methods” and placed on an agar support for photography. A, Wild-type plants. Bar = 5.0 cm. B, nip plants. Bar = 5.0 cm. C, Wild-type primary root with emergent lateral roots. Bar = 1.0 mm. D, nip lateral root primordium. Bar = 0.25 mm. E, Wild-type nodule. Bar = 0.50 mm. F, nip nodules/bumps. Note the presence of a dark pigment at the distal ends of the nodules. Bar = 0.50 mm.