This paper investigates the effects of heat source and radiation on unsteady two dimensional, laminar, boundary layer flow of a viscous, incompressible, electrically conducting fluid along a semi-infinite vertical plate in the presence of thermal and concentration buoyancy effects. A time-dependent is assumed and the radiative flux is described using the differential approximation for radiation. Asymptotic series expansion about a small parameter e, is performed to obtain the flow fields. The velocity of the porous plate increases exponentially with time and a variable suction velocity is applied normal to the plate. The governing equations of the flow field are solved using perturbation technique and the expressions are obtained for velocity, temperature and concentration fields. The effects of various parameters such as  and  are discussed and derived through graphs and tables.