Plant height, number of branches and leaves per plant, leaf area, fresh and dry weights of the shoot system, specific leaf weight (SLW), leaf weight ratio (LWR), specific leaf area (SLA) and leaf area ratio (LAR), estimated at the active growth period; after 90 days from planting, were decreased due to decreasing NPK dose less than the recommended one during the two growing seasons. Bio-fertilizers used, over all NPK doses, counteracted, in general the depressing effect of NPK stresses on most growth parameters studied. The most effective strain restoring most of the plant growth capacity was found with NFB when used individually or in combination with the others. The anatomical structure, of the terminal leaflet blade, taken from the 3^rd  compound leaf from the plant tip, taken at the middele part indicated that NPK stress decreased thickness leaflet in the midrib region, mesophyll tissue, palisade tissue and spongy tissue . Midrib V.B. dimension (length and width), as well as thickness of xylem tissue and phloem tissue at the midrib bundle (external and internal) and metaxylem vessel dimension were also decreased. The most striking effects were found with respect to components of the vascular system. The inoculation of bacterial strains used counteracted the depressing effects of NPK stresses on all these parameters. The most effective treatments were found with NFB+PDB+SB, NFB+PDB, NFB+SB, NFB alone in a descending order. The stem structure at the 3^rd internode of the main stem of potato plants as seen in T.S. indicated that stem diameter, cortex thickness, large vascular bundle dimension, external and internal phloem and xylem tissue thickness as well as pith tissue dimension  were decreased due to NPK stress compared with the recommended one. All bacterial inoculation treatments counteracted the reduction in cell volume caused by NPK stress and increased stem diameter, cortex thickness, large vascular bundle dimension, external and internal phloem and xylem tissue thickness as well as pith tissue dimension. Metaxylem vessel dimension was also increased. Inoculation with NFB alone as well as inoculation with either NFB+PDB or mixed strains (NFB+PDB+SB) were generally the best treatment compared with plants grown without inoculation under any NPK doses.