摘要Solar-induced chlorophyll fluorescence(SIF)is a promising photosynthetic proxy and a valuable phenotyping tool.However,under drought and fluctuating light,the mechanistic linkages between SIF and photosynthesis require further investigation due to complex light energy partitioning.In this study,we measured leaf-level SIF,gas-exchange,and active fluorescence parameters in Ginkgo biloba under drought and fluctuating light.Our results demonstrate a drought-induced decoupling of both leaf-level SIF and PSII-emitted chlorophyll fluores-cence(SIFPSII,derived from active fluorescence parameters)from photosynthesis.This was driven by a slight SIFPSII reduction alongside strong photosynthetic suppression.The limited SIFPSII decrease resulted from a stable fluorescence yield(ΦSIF),maintained by the regulatory interplay between non-photochemical quenching(NPQ)and the fraction of open PSII reaction centers(qL),and the low responsiveness of ΦSIF to changes in the maximum photochemical quantum yield(ΦPSIImax).In contrast,photosynthetic suppression was largely due to decreased stomatal conductance(gs).ΦPSIImax and photorespiration are also central to balancing the light and carbon re-actions,preventing energy overload.Interestingly,fluctuating light phases did not significantly alter this decoupling.However,when combining data from both high and low light,SIFPSII and photosynthesis remained tightly coupled,likely due to their shared light dependency.These insights improve the physiological inter-pretation of SIF and underscore the importance of SIF-based multi-trait pheno typing models for accurate field monitoring.