All transgenic lines were able to balance electron transport and biochemical process at low radiation keeping apparent quantum yield constant and the light saturation point relatively low. Thus, the photosynthetic changes associated with the transgenic events could make the transgenic lines appropriate for use in low light regions such as forest intercropping systems of productivity was increased. Although one transgenic line had weakly improved photosynthesis under cool conditions in this study, improving cold temperature photosynthesis in switchgrass will require more than manipulating the expression of a single gene.