FIG. 9.

Symbiotic phenotype of S. meliloti mutants in K⁺ uptake systems. (A) Nodulation kinetics of alfalfa plants inoculated with strain 1021 (wild type; black squares), 10tAK1 (Trk⁻ Kup1⁻; black triangles), 10tAKK (Trk⁻ Kdp⁻ Kup1⁻; black dots), or 10tAK21 (Trk⁻ Kup2⁻ Kup1⁻; asterisks). The bars indicate standard errors. (B) Competition assays. Data represent the percentage of white nodules occupied by the wild type (1021), 10tAG (Trk⁻) (tAG), 10tAK1 (Trk⁻ Kup1⁻) (tAK1), 10tAK2 (Trk⁻ Kup2⁻) (tAK2), or 10tAKdp (Trk⁻ Kdp⁻) (tAKdp) after inoculation with 1:1 mixtures of each strain and 1021(pGUS3). A representative example of two experiments is shown. Bars correspond to standard errors, and different letters indicate significative differences according to an analysis-of-variance test.