This research aims to study the effect of Gebbrilin compounds, specially GA٣, on the percentage of germination of seeds in different concentrations and duration, Also the effect of this compound on the growth of the root cells and so on the cellular division. It was observed from the results that these compounds had an evident effect on the degree of germination within the low concentration, but it has an opposition effect in the high concentrations. The results concerning the growth of the roots are analogous to those of the germination results. An obvious difference was in the reaction of wheat and barley to the different concentrations of GA٣. For the mitotic index no differences were observed compared to the control.