Quantifying high-temperature stress on soybean canopy photosynthesis: The unique role of sun-induced chlorophyll fluorescence

Authors: KIMM, HYUNGSUK - University Of Illinois; GUAN, KAIYU - University Of Illinois; BURROUGHS, CHARLES - University Of Illinois; PENG, BIN - University Of Illinois; Ainsworth, Elizabeth - Lisa; Bernacchi, Carl; MOORE, CAITLIN - University Of Western Australia; KUMAGAI, ETSUSHI - National Agriculture And Food Research Organization (NARO), Agricultrual Research Center; YANG, XI - University Of Virginia; BERRY, JOSEPH - Carnegie Institute - Stanford; WU, GENGHONG - University Of Illinois

Submitted to: Global Change Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/7/2021
Publication Date: 6/1/2021
Citation: Kimm, H., Guan, K., Burroughs, C.H., Peng, B., Ainsworth, E.A., Bernacchi, C.J., Moore, C.E., Kumagai, E., Yang, X., Berry, J.A., Wu, G. 2021. Quantifying high-temperature stress on soybean canopy photosynthesis: The unique role of sun-induced chlorophyll fluorescence. Global Change Biology. 27(11):2403-2415. https://doi.org/10.1111/gcb.15603.
DOI: https://doi.org/10.1111/gcb.15603

Interpretive Summary: Rising temperatures and increased vapor pressure deficit can alter crop physiological function without changing the canopy structure or spectral signature. Sun-induced fluorescence (SIF) has potential use to detect plant temperature stress because it is mechanistically linked to photosynthesis. This study tested how SIF changed in soybeans grown at a range of elevated temperatures (from +1.5 to +6 C) in the field. When normalized by radiation and crop canopy size and shape, SIF was strongly correlated with crop light use efficiency, and sensitive to temperature treatments. These results suggest the potential to use SIF to detect high temperature stress and subsequent yield loss in soybean.

Technical Abstract: High temperature and accompanying high vapor pressure deficit often stress plants without causing distinctive changes in plant canopy structure and consequential spectral signatures. Sun-induced chlorophyll fluorescence (SIF), because of its mechanistic link with photosynthesis, may better detect such stress than remote sensing techniques relying on spectral reflectance signatures of canopy structural changes. However, our understanding about physiological mechanisms of SIF and its unique potential for physiological stress detection remains less clear. In this study, we measured SIF at a sophisticated high-temperature experiment, Temperature Free-Air Controlled Enhancement (T-FACE), to explore the potential of SIF for physiological investigations. The experiment provided a gradient of soybean canopy temperature with 1.5, 3, 4.5, and 6.0 °C above the ambient canopy temperature in the open field environments. SIF yield, which is normalized by radiation and canopy structure, showed a high correlation with photosynthetic light use efficiency (R2=0.8) and captured dynamic plant responses to high-temperature conditions. SIF yield was affected by canopy structural and plant physiological changes associated with high-temperature stress (partial correlation r=0.60 and -0.23). Near-infrared reflectance of vegetation, only affected by canopy structural changes, was used to minimize the canopy structural impact on SIF yield and to retrieve physiological SIF yield (FF), which outperformed SIF yield in responding to physiological stress (r=-0.37). Our findings highlight that the derived FF sensitively responded to the physiological downregulation of soybean GPP under high temperature. FF, if reliably derived from satellite SIF, can support monitoring regional soybean growth under high-temperature stress and thus mitigating consequential yield loss.