Tobacco plans were transformed by the Agrobacterium tumefaciens strain A 699, with no target genes. Processes related to rate of photosynthesis in leaves of transgenic tobacco plants and stability of the transformed plant development are discussed. The effects of increase of photosynthetic rate and of decrease of developmental stability observed under the conditions of increased illumination may be bound up with reconstructions in the transformants’ genome functions due to the stress caused by the transformation process. The attenuation of effects observed at T₅, T₆ generations of transgenic plants can be a result of work of population homeostasis mechanism.