Solar-induced chlorophyll fluorescence (SIF) has shown great potential for detecting changes in vegetation function under herbicide stress. However, how physiological (ΦF, canopy SIF emission efficiency) and non-physiological (e.g., structure and illumination) dynamics regulate canopy SIF, and the coupling between SIF and gross primary production (GPP) under herbicide stress remains unclear. Here, we conducted continuous eddy covariance flux and far-red SIF measurements during the early stage of maize in an herbicide-resistant maize field, where herbicide exclusively affects weeds. We investigated the performance of SIF, GPP, and vegetation indices (VIs) in capturing herbicide stress and then explored the sensitivity of SIF to the effects of herbicide treatments by disentangling canopy SIF into the physiological (ΦF) and non-physiological components (NIRvP). We found that SIF rapidly increased in response to the herbicide and that GPP decreased, and that both were more responsive than VIs in capturing the early effects of herbicides. Thus, the opposing responses in SIF and GPP disrupted their otherwise linear relationship during herbicide treatment. More importantly, we found that the increased ΦF dominated the variation of SIF during the early stages of herbicide stress, while the influence of NIRvP was prominent in the variability of SIF in the absence of herbicide. By unraveling its physiological and non-physiological contributions, our findings advance our understanding of how SIF responds to herbicide stress in heterogeneous cropland and will improve our interpretation of SIF as a tool for monitoring photosynthesis.

太阳诱导的叶绿素荧光 (SIF) 在检测除草剂胁迫下植被功能的变化方面显示出巨大的潜力。然而，生理（ΦF，冠层 SIF 排放效率）和非生理（例如，结构和光照）动力学如何调节冠层 SIF，以及在除草剂胁迫下 SIF 与总初级生产力（GPP）之间的耦合仍不清楚。在这里，我们在抗除草剂玉米田的玉米早期阶段进行了连续涡流协方差通量和远红 SIF 测量，其中除草剂只影响杂草。我们调查了 SIF、GPP、和植被指数 (VIs) 在捕捉除草剂胁迫中的作用，然后通过将冠层 SIF 分解为生理 (ΦF) 和非生理成分 (NIRvP) 来探索 SIF 对除草剂处理效果的敏感性。我们发现 SIF 对除草剂的反应迅速增加，而 GPP 下降，并且两者在捕捉除草剂的早期效果方面都比 VI 更敏感。因此，SIF 和 GPP 中的相反反应破坏了它们在除草剂处理期间的线性关系。更重要的是，我们发现在除草剂胁迫的早期阶段，增加的 ΦF 主导了 SIF 的变化，而在没有除草剂的情况下，NIRvP 的影响在 SIF 的变化中很突出。通过揭示其生理和非生理贡献，