We used different doses of ¹³⁷Cs-γ irradiation to irradiate the seeds of Phyllostachys heterocycla ‘Pubescens’, in order to determine the physiological response to ¹³⁷Cs-γ stress. By determining photosynthetic pigment content and chlorophyll fluorescence parameters in leaves of seedlings, we explored the use of radiation in screening beneficial mutants. The photosynthetic pigment content and chlorophyll fluorescence parameters such as F_m, F_v, F_v/F_m, F_v/F_o, yield, apparent electron transport rates (ETR) at 30 or 60 Gy were higher than those at 90 Gy. Low-dose irradiation produced high efficiency of excitation energy capture by open PSII reaction centers of leaves and strong photosynthetic capacity. However, high-dose irradiation produced opposite effects. The degree of light energy dissipation with different doses of radiation and the analysis of the ETR-photosynthetically active radiation response curve further confirmed the findings.