A sheared background flow in a plasma induces coupling between different MHD wave modes, which results in their mutual transformation with corresponding energy redistribution between the modes. In this way, the energy can be transferred from one wave mode to the other, but energy can also be added to or extracted from the background flow. In the present paper we investigate whether the wave coupling and energy transfer mechanisms can operate under solar wind conditions. It is shown that this is indeed the case. Hence, the long-period waves observed in the solar wind at r > 0.3 AU might be generated by much faster periodic oscillations in the photosphere of the Sun. Other possible consequences for the observable peculiar beat phenomena in the wind and acceleration of the wind particles are also discussed.