Experiments were conducted on Arabidopsis thaliana plants in vitro to investigate the influence of three factors: inoculation with Azospirillum brasilense bacteria, the presence or stress of phosphorus and iron in the MS growth medium, and their effects on root system architecture modifications. These modifications, in turn, affected plant growth measured by the fresh weight of the shoot. The research employed a Randomized Complete Block Design (R.C.B.D). The findings showed that root structure affects plant growth. Treating the medium with bacteria resulted in decreased primary root length, elongation of root hairs, increased number of lateral roots. The presence of phosphorus in the growth medium increased primary root length and decreased root hairs length, whereas iron decreased root hairs length and increased the number and length of the lateral roots significantly. These findings indicate that each factor induced specific modifications in root growth and structure, which in turn affected plant nutrition and growth, leading to changes in shoot fresh weight. The results suggest that phosphorus is the most crucial factor among those studied, despite the influence of other factors on plant nutrition and growth, and in the two-way and three-way interactions affecting the fresh weight of the seedling shoot. The results suggest that phosphorus is the most crucial factor among those studied, despite the influence of other factors on plant nutrition and growth, and in the two-way and three-way interactions affecting the fresh weight of the plant shoot.