Agroecosystem Sustainability Center, Institute for Sustainability, Energy, and Environment (iSEE), University of Illinois at Urbana-Champaign, Urbana, IL, USA.
College of Agricultural, Consumers, and Environmental Sciences, University of Illinois Urbana-Champaign, Urbana, IL, USA.
Glob Chang Biol. 2021 Jun;27(11):2403-2415. doi: 10.1111/gcb.15603. Epub 2021 Apr 12.
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 high-temperature experiment, Temperature Free-Air Controlled Enhancement, to explore the potential of SIF for physiological investigations. The experiment provided a gradient of soybean canopy temperature with 1.5, 3.0, 4.5, and 6.0°C above the ambient canopy temperature in the open field environments. SIF yield, which is normalized by incident radiation and the fraction of absorbed photosynthetically active radiation, showed a high correlation with photosynthetic light use efficiency (r = 0.89) 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 (Φ ) signals. Φ further excludes the canopy structural impact than SIF yield and indicates plant physiological variability, and we found that Φ outperformed SIF yield in responding to physiological stress (r = -0.37). Our findings highlight that Φ sensitively responded to the physiological downregulation of soybean gross primary productivity under high temperature. Φ , if reliably derived from satellite SIF, can support monitoring regional crop growth and different ecosystems' vegetation productivity under environmental stress and climate change.
高温及其伴随的高蒸气压亏缺通常会给植物带来压力，但不会引起冠层结构的明显变化和随之而来的光谱特征。太阳诱导的叶绿素荧光（SIF）由于与光合作用的机制联系，可能比依赖冠层结构变化光谱反射特征的遥感技术更好地检测这种胁迫。然而，我们对 SIF 的生理机制及其对生理胁迫检测的独特潜力的理解仍然不太清楚。在这项研究中，我们在高温实验“Temperature Free-Air Controlled Enhancement”中测量了 SIF，以探索 SIF 进行生理研究的潜力。该实验在开放环境中提供了大豆冠层温度的梯度，比环境冠层温度高出 1.5、3.0、4.5 和 6.0°C。SIF 产量，用入射辐射和吸收的光合有效辐射的分数归一化，与光合光利用效率（r=0.89）表现出高度相关性，并捕捉到植物对高温条件的动态响应。SIF 产量受到与高温胁迫相关的冠层结构和植物生理变化的影响（部分相关 r=0.60 和-0.23）。受冠层结构变化影响的植被近红外反射率，用于最大限度地减少冠层结构对 SIF 产量的影响，并提取生理 SIF 产量（Φ）信号。Φ 比 SIF 产量进一步排除了冠层结构的影响，并指示了植物生理变异性，我们发现Φ在响应生理胁迫方面比 SIF 产量表现更好（r=-0.37）。我们的研究结果强调了Φ对高温下大豆总初级生产力的生理下调敏感。如果从卫星 SIF 中可靠地得出 Φ，它可以支持监测环境胁迫和气候变化下区域作物生长和不同生态系统的植被生产力。
