LAUSR

Solar-induced fluorescence (SIF) is a promising proxy for photosynthesis, but it is unclear whether SIF performs well in tracking the gross primary productivity (GPP) under different environmental conditions. In this study, we investigated the dynamics of SIF and GPP from October 2020 to June 2021 in a winter wheat (Triticum aestivum L.) field and found that the ability of SIF to track GPP was weakened at chilling temperatures. Accounting for the coupling of light and temperature at seasonal scales, we found SIF yield showed a lower temperature sensitivity and had a lower but broader optimal temperature range compared with light use efficiency (LUE), although both SIF yield and LUE decreased in chilling conditions. The discrepancy between the temperature responses of SIF yield and GPP caused an increase in the ratio of SIF to GPP in winter, which indicated the variation in the GPP-SIF relationship during this period. The results of our study highlight the impact of low temperature on the relationship between SIF and GPP and show the necessity of reconsidering the dynamics of energy distribution inside plants under changing environments.