In polar semiconductor samples of the self-organized quantum dots, grown by the Stranski-Krastanow growth method, the lowest-energy extended states of the motion of the electronic excitations, are assumed to be the wetting-layer states. The coupling between these extended states and the electronic states localized in the individual quantum dots, may influence the optical spectra of such samples in the sub-wetting layer region of energy. This effect is studied assuming the Fröhlich's coupling between the electrons and the polar optical phonons. The contribution of this interaction to the appearance of the sub-wetting layer continuum in the optical spectra, and to the level broadening of the localized states, pointed out in some experiments, is estimated.