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Several reports have suggested that inoculation of cereal plants with different species of the beneficial rhizosphere bacterium Azospirillum results in an enhanced plant growth (Levanony et al. 1989). The underlying mechanism by which Azospirillum affects plant growth are poorly understood. One mode of action could be linked to an enhancement of mineral uptake by the root system (Pacovsky 1990) and of root surface area (Levanony et al. 1989), although quantitative data are scanty. This communication provides evidence that A.brasilense promotes root and root hair growth along with the uptake of NO3 -, and enhances Fe++ accumulation in plant tissues.

Pre-germinated corn seeds were aseptically grown with Azospirillum cultures or GA3. Both, inoculation with Azospirillum and GA 3 in concentrations similar to those produced by Azospirillum cultures, significatively increased root growth. Results sustain that GAs are effective in promoting root growth in very small quantities and the effect of Azospirillum might be mediated by GA production.