Chlorophyll fluorescence parameters and spectral reflectance at leaf level were measured at both predawn and noon, under different temperatures and natural light conditions from autumn to winter. Predawn F_v / F_m of both mango (Mangifera indica L.), a tropical fruit tree, and Podocarpus nagi Zoll. et Moritz., a subtropical conifer, decreased with decreasing temperature, with the former to a greater extent than the latter. Yet, predawn F_v / F_m of Taiwan alder (Alnus formosana Makino), a broadleaf tree widely distributed from the lowlands to 3000 m above sea level in Taiwan, was less influenced by temperature. Nevertheless, taking all three species into consideration, predawn F_v / F_m showed a strong correlation with predawn photochemical reflectance index [(PRI_p), PRI = (R₅₃₁ - R₅₇₀) / (R₅₃₁ + R₅₇₀), where R = reflectance]. For the data obtained at noon, ΔF / F_m′ showed a significant but weak correlation with PRI (PRI_n). However, stronger correlation between ΔF / F_m′ and ΔPRI (PRI_p - PRI_n) was found. In addition, while a non-significant or weak correlation between non-photochemical quenching (NPQ) and PRI_n was observed in species sensitive to low temperature, their NPQ was significantly correlated with ΔPRI. We conclude that PRI_p can serve as an indicator of the seasonal variation of potential PSII efficiency; and ΔPRI reflects the actual photodissipation as well as actual PSII efficiency during illumination. For the three species in this study, the PRI provides a more consistent measure of the variation in predawn fluorescence values than for steady-state values measured under normal seasonally varying daylight illumination.