To determine differences between length growths for each vegetative organ in case of different experimental variants, biometric measurements were taken. The ability to stimulate or inhibit plant growth and development was closely correlated with the concentrations of polyphenolic compounds applied. Thus, in our experiments the presence of these compounds in low concentrations (130 mg GAE/dm3 or 95 mg GAE/dm3) has a beneficial effect on the development of organisms. In other cases, when the concentrations of polyphenolic compounds are higher (191 mg GAE/dm3) a phenomenon of inhibition is induced ( Popa et al., 2007). An almost similar situation was observed in the case of sunflower plants ( Fig. 3).