Abstract:The present paper deals with the effect of shading on the formation and absoission of Vicia faba flowers and pods during the three different periods before, during and after flowering, the capability of yield compensation and the ecologicphysiologie, principle of the formation and abscission of flowers and pods. In our experiments the total number of flowers and pods was reduced in the case of shading before flowering, but the rate of abscission was reduced. The weight of the resulting grain was therefore significantly larger than thar of the treatment of shading of during and after flowering, even larger than the unshaded plants. There was no distinct influence on the total number of flowers of shading before flowering and after flowering, but the ruduction of the grain yield was significantly higher than the unshaded plants. The specific leaf weight, chlorophyll content of the leaves by the end of shading, photosynthetic production, the rate of distributing dry matter to the reproductive organs, the sugar and the nitrogen contents of plants were reduced at various stages of shading, but at mature, the sugar and nitrogen contents and the amounts of nutritive elements (P,K, Ca, Mg)absorbed by the grains, stems and leaf were not affected. The principal reason for flower and pod reduction caused by shading was the decrease of the sugar-nitrogen ratio, and not any change in the abundance of nutritive elements.