Remote sensing has been widely used in vegetation observation and analysis. Indices calculated from spectra acquired by remote sensing are powerful tools for vegetation modeling. Among them, Photochemical Reflectance Index (PRI) has attracted attention due to its characteristics related to the photosynthetic activity. PRI is directly related with non-photochemical quenching (NPQ), which reflects from dissipation of excess energy in the photosynthetic apparatus. However, previous research studied relationships between PRI and NPQ only under steady-state light conditions. While it is known that various functions dynamically change with time after changing light intensity, it is still unclear whether temporal dependence of PRI is similar to CO2 assimilation rate (A) and NPQ and whether the relationship between PRI and photosynthetic characteristics is held under the dynamic phase. Here, we studied temporal dependence of gas exchange characteristics, chlorophyll fluorescence parameters and PRI in two types of poplar differing in stomatal responses to light intensity. The results showed that, when a dark-adapted leaf was exposed to strong light (induction phase), the response time is sorted as, the PSII quantum yield (ФP) = NPQ < PRI < A for stomatal limited poplar and ФP = NPQ < A < PRI for stomatal unlimited poplar. Consequently, the PRI-NPQ and the PRI-A relationships differed between the steady-state and induction phase. On the other hand, when the light-adapted leaves were transferred from dark to light, time response was similar between ФP, NPQ and PRI. Therefore, PRI can be used to assess ФP and NPQ even under dynamic light conditions if light-adapted leaves are used. Comparison between the two types of poplar showed that stomatal responses to light change do not affect time responses in ФP, NPQ and PRI, suggesting that CO2 fixation and PSII activity are decoupled with each other under dynamic light conditions.