###### Abstract  
The strong correlation between gross primary production (GPP) and sun-induced chlorophyll fluorescence (SIF) has been reported in many studies and is the basis of the SIF-based GPP estimation. However, GPP and SIF are not fully synchronous under various environmental conditions, which may destroy a stable GPP-SIF relationship. Therefore, exploring the difference between responses of GPP and SIF to the environment is essential to correctly understand the GPP-SIF relationship. As the common driver of GPP and SIF, the incident radiation could cause GPP and SIF to have similar responses to the environment, which may obscure the discrepancies in the responses of GPP and SIF to the other environmental variables, and further result in the ambiguity of the GPP-SIF relationship and uncertainties in the application of SIF. Therefore, we tried to exclude the dominant role of radiation in the responses of GPP and SIF to the environment based on the binning method, in which continuous tower-based SIF, satellite SIF, and eddy covariance GPP data from two growing seasons were used to investigate the differences in the responses of GPP and SIF to radiation, air temperature (Ta), and evaporation fraction (EF). We found that the following: (1) At both the site and satellite scales, there were divergences in the light response speeds between GPP and SIF which were affected by Ta and EF. (2) SIF and its light response curves were insensitive to EF and Ta compared to or power, and the consistency in GPP and SIF light responses was gradually improved with the improvement of Ta and EF. (3) The dynamic slope values of the GPP-SIF relationship were mostly caused by the different sensitivities of GPP and SIF to EF and Ta. Our results highlighted that GPP and SIF were not highly consistent, having differences in environmental responses that further confused the GPP-SIF relationship, leading to complex SIF application. G 2024 14 771 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 111 11 111 11 111 111 111 111 11 111 111 1  
Sun-induced chlorophyll fluorescence (SIF) is the irradiance re-emitted from chlorophyll molecules in the 650-800 nm range during light reactions under excitation by solar radiation, which is directly linked with photosynthesis [15]. Compared with traditional vegetation indices, the physiological information included in SIF has great potential and advantages in GPP estimation [4]. In the light use efficiency (LUE) model, GPP and SIF can be expressed as similar expressions:  
\[GPP=FPAR\times PAR\times\Phi_{P} \tag{1}\]  
\[SIF=FPAR\times PAR\times\Phi_{F}\times f_{esc} \tag{2}\]  
where \(FPAR\) is the fraction of absorbed photosynthetically active radiation (\(APAR\)), \(PAR\) is photosynthetically active radiation, and \(\Phi_{P}\) is the efficiency of the light used for photosynthesis [12; 16]. \(\Phi_{F}\) is the chlorophyll fluorescence emission yield and \(f_{esc}\) is the fraction of SIF photons escaping the canopy [17]. Based on Equations (1) and (2), APAR (\(\mathrm{FPAR}\times\mathrm{PAR}\)), as the common driver of GPP and SIF, could lead to similar trends of GPP and SIF, which are the basis of the linear GPP-SIF relationship to some degree. However, vegetation has unique survival strategies that try to regulate the efficiency of photosynthesis under various environmental conditions [18; 19]. Chlorophyll fluorescence is one of the byproducts of this strategy to avoid light damage of photosynthetic system, which means that SIF is the result of photosynthesis (GPP) adapting to the environment [20]. Therefore, an incomplete synchronization between GPP and SIF theoretically exists. Indeed, an increasing number of studies have highlighted the fact that GPP and SIF are not fully synchronous. For example, [PERSON] et al. [21] found that GPP and red SIF exhibited different responses to radiation under different environmental conditions in an evergreen forest. [PERSON] et al. [22] indicated that the sensitivities of SIF and GPP to the environment are different. [PERSON] et al.