Growth interactions during bacterial colonization of seedling rootlets.

Rootlet elongation and bacterial growth on rootlets were determined after inoculation of cucumber and spinach seedlings with Pseudomonas strains differing in production of siderophores and HCN. Siderophore producers grew more profusely than nonproducers on both species and promoted rootlet elongation on cucumber. Coinoculation of siderophore producers and nonproducers resulted in restricted growth of the latter. The total populations of nonproducers of HCN in the presence of HCN producers were not decreased, but the tenacity of their association with the rootlet surface was altered.