There remains limited information to characterize the solar-induced chlorophyll fluorescence (SIF)-gross primary production (GPP) relationship in C4 cropping systems. The annual C4 crop corn and perennial C4 crop miscanthus differ in phenology, canopy structure and leaf physiology. Investigating the SIF-GPP relationships in these species could deepen our understanding of SIF-GPP relationships within C4 crops. Using in situ canopy SIF and GPP measurements for both species along with leaf-level measurements, we found considerable differences in the SIF-GPP relationships between corn and miscanthus, with a stronger SIF-GPP relationship and higher slope of SIF-GPP observed in corn compared to miscanthus. These differences were mainly caused by leaf physiology. For miscanthus, high non-photochemical quenching (NPQ) under high light, temperature and water vapor deficit (VPD) conditions caused a large decline of fluorescence yield (Φ_F), which further led to a SIF midday depression and weakened the SIF-GPP relationship. The larger slope in corn than miscanthus was mainly due to its higher GPP in mid-summer, largely attributed to the higher leaf photosynthesis and less NPQ. Our results demonstrated variation of the SIF-GPP relationship within C4 crops and highlighted the importance of leaf physiology in determining canopy SIF behaviors and SIF-GPP relationships.

在 C4 种植系统中，描述太阳诱导的叶绿素荧光 (SIF)-总初级生产 (GPP) 关系的信息仍然有限。一年生C4作物玉米和多年生C4作物芒草在物候、冠层结构和叶片生理方面存在差异。研究这些物种中的 SIF-GPP 关系可以加深我们对 C4 作物中 SIF-GPP 关系的理解。使用两种物种的原位冠层 SIF 和 GPP 测量以及叶水平测量，我们发现玉米和芒草之间的 SIF-GPP 关系存在显着差异，在玉米中观察到更强的 SIF-GPP 关系和更高的 SIF-GPP 斜率相比芒草。这些差异主要是由叶片生理引起的。对于芒草，高光下的高非光化学猝灭（NPQ），_F )，这进一步导致了 SIF 中午抑郁并削弱了 SIF-GPP 关系。玉米比芒草更大的斜率主要是由于其在盛夏的 GPP 较高，主要归因于较高的叶片光合作用和较低的 NPQ。我们的结果证明了 C4 作物中 SIF-GPP 关系的变化，并强调了叶片生理学在确定冠层 SIF 行为和 SIF-GPP 关系中的重要性。