Figure 18.

Diagrammatic representation of a root hair showing its differentiation into a nitrogen fixation and microbe replication zone along the hair length, and nitrogen transfer zone in the hair tip. Lack of movement of microbes in the tip of the hair results in a maximum exposure to superoxide and maximum secretion of nitric oxide. Rapid movement of microbes along the lateral walls reduces exposure to superoxide and replicates microbes, facilitating nitrogen fixation by the microbes.