Conducted till now studies on symbiosis of papilionaceous plants and rhizobia discovered the genetic background of this phenomenon and allowed to identify numerous plant and bacteria metabolites involved in the process of starting of symbiosis and development of nodules. One of this compounds are flavonoids, recognised as signal particles participating in information exchange between a bacteria and a plant, affecting among others nodules formation on papilionaceous plants. These compounds are often submitted to processes which decrease their concentration on the way from a producer to a destined organism, they diffuse or break-up in the soil solution and are degraded by soil microorganisms. It can be then assumed that their insufficient amount is a cause of low efficient symbiosis, what considerably limits plant supply with nitrogen and decreases their yielding. An effect of use of flavonoid extract obtained from germinating seeds on ontogenesis, forming of physiological growth indexes and yielding of pea was evaluated in these studies. Application of a flavonoid preparation increased, among others, the number and weight of nodules and activity of nitrogenase, what in a consequence led to production of greater mass of vegetative and generative organs by pea plants.