Despite the fact that SIF can monitor the downregulation of GPP in response to drought conditions at both leaf and canopy levels, water deficit also affects the link of SIF to GPP [15]. Likewise, the SIF-GPP relationship is also somewhat impacted by the photochemistry activities and the kinetics of enzymes involved in carbon reactions, which are both affected by temperature [16]. The SIF-GPP relationship can be altered by the dynamic energy distribution among three energy dissipation pathways in response to various temperature conditions. Additionally, the SIF-GPP relationship depends heavily on the chlorophyll content, which could explain why SIF and GPP have different growth peaks [17]. Plants with the two distinct photosynthetic pathways, C3 and C4, are typically regarded as two major plant functional types (PFT) in climate-carbon models because of their significant differences in environmental requirements and global change feedback. C4 plants have higher resource-use efficiency and potential productivity because they have evolved from the C4 route to adapt to high light intensity, high temperature, and dryness through C4 photosynthesis. In C4 species, the effect of diffusional pathways on the SIF-GPP relationship is mitigated by the cooperation of mesophyll and bundle sheath cells to concentrate CO\({}_{2}\) near Rubisco. The fact that distinct PFTs have different metabolic pathways may explain why there are differences in the slopes between SIF and GPP for these PFTs [9]. SIF, a single energy dissipation pathway, is insufficient to effectively account for the dynamic fluctuations in GPP under stress. As one of three pathways for consuming the solar energy absorbed by leaves, NPQ may thus play a controlled role in the distribution of energy between fluorescence and PQ [18]. The downregulation of photosynthetic efficiency at diurnal timescales is often correlated with the degree of epoxidation in the xanthophyll pigments, which increases under stress in leaves [19]. Under stress, xanthophyll de-epoxidation typically causes a rise in NPQ. Some investigations have discovered that the photochemical reflectance index (PRI), which often exhibits a negative connection with NPQ, might describe the epoxidation status of xanthophyll pigments [20]. Variations in PRI can well represent changes in NPQ generated by the xanthophyll cycle in response to the external environment because of sluggish adjustments in pigment pools at diurnal timescales. However, at seasonal timescales, the changes in the carotenoid and chlorophyll pigment pools in leaves can also contribute to the differences in PRI [21; 22]. Therefore, at a specific chlorophyll content level, PRI can be utilized to characterize NPQ fluctuations at an instantaneous or daily scale, and it is important to thoroughly investigate the potential effects of PRI variation on the SIF-GPP relationship. Under the premise of some aspects of the information regarding NPQ that can be estimated from PRI, it makes sense to study the influences of PRI on the SIF-based GPP estimation. [PERSON] et al. [18] used MODIS PRI, OCO-2 SIF observations, and contemporaneous flux data from EC locations to evaluate the value of PRI for the SIF-based GPP estimation. However, because of various data sources and broad spatial scales, the conclusions are highly unclear. Recently, a large amount of continuously tower-based observations can offer us trustworthy data to study the SIF-GPP relationship and its reaction to various environmental conditions [2; 19; 23]. To measure radiance from a downwelling and upwelling direction, a number of tower-based spectral systems with a bi-hemispherical or hemispherical-conical setup have been developed. According to [PERSON] et al. [24], some spectral systems (e.g., FluoSpec2) contain two subsystems, one for SIF retrieval and the other for calculating vegetation indices (VI), such as the normalized difference vegetation index (NDVI), PRI.