Anderegg Jonas, Kirchgessner Norbert, Aasen Helge, Zumsteg Olivia, Keller Beat, Zenkl Radek, Walter Achim, Hund Andreas
Plant Pathology Group, Institute of Integrative Biology, ETH Zurich, Zurich, Switzerland.
Crop Science Group, Institute of Agricultural Sciences, ETH Zurich, Zurich, Switzerland.
Front Plant Sci. 2024 Jun 4;15:1335037. doi: 10.3389/fpls.2024.1335037. eCollection 2024.
Canopy temperature (CT) is often interpreted as representing leaf activity traits such as photosynthetic rates, gas exchange rates, or stomatal conductance. This interpretation is based on the observation that leaf activity traits correlate with transpiration which affects leaf temperature. Accordingly, CT measurements may provide a basis for high throughput assessments of the productivity of wheat canopies during early grain filling, which would allow distinguishing functional from dysfunctional stay-green. However, whereas the usefulness of CT as a fast surrogate measure of sustained vigor under soil drying is well established, its potential to quantify leaf activity traits under high-yielding conditions is less clear. To better understand sensitivity limits of CT measurements under high yielding conditions, we generated within-genotype variability in stay-green functionality by means of differential short-term pre-anthesis canopy shading that modified the sink:source balance. We quantified the effects of these modifications on stay-green properties through a combination of gold standard physiological measurements of leaf activity and newly developed methods for organ-level senescence monitoring based on timeseries of high-resolution imagery and deep-learning-based semantic image segmentation. In parallel, we monitored CT by means of a pole-mounted thermal camera that delivered continuous, ultra-high temporal resolution CT data. Our results show that differences in stay-green functionality translate into measurable differences in CT in the absence of major confounding factors. Differences amounted to approximately 0.8°C and 1.5°C for a very high-yielding source-limited genotype, and a medium-yielding sink-limited genotype, respectively. The gradual nature of the effects of shading on CT during the stay-green phase underscore the importance of a high measurement frequency and a time-integrated analysis of CT, whilst modest effect sizes confirm the importance of restricting screenings to a limited range of morphological and phenological diversity.
冠层温度（CT）通常被解释为代表叶片活性特征，如光合速率、气体交换速率或气孔导度。这种解释基于这样的观察：叶片活性特征与影响叶片温度的蒸腾作用相关。因此，CT测量可为灌浆初期小麦冠层生产力的高通量评估提供依据，这将有助于区分功能性与非功能性持绿。然而，虽然CT作为土壤干燥条件下持续活力的快速替代指标的有用性已得到充分证实，但其在高产条件下量化叶片活性特征的潜力尚不清楚。为了更好地理解高产条件下CT测量的敏感性极限，我们通过不同的短期花前冠层遮荫改变库源平衡，在基因型内产生了持绿功能的变异性。我们通过结合叶片活性的金标准生理测量以及基于高分辨率图像时间序列和深度学习语义图像分割的器官水平衰老监测新方法，量化了这些改变对持绿特性的影响。同时，我们通过安装在杆子上的热成像相机监测CT，该相机提供连续的、超高时间分辨率的CT数据。我们的结果表明，在没有主要混杂因素的情况下，持绿功能的差异转化为CT的可测量差异。对于一个高产源限制型基因型和一个中产库限制型基因型，差异分别约为0.8°C和1.5°C。持绿阶段遮荫对CT的影响具有渐进性，这突出了高测量频率和CT时间积分分析的重要性，而适度的效应大小证实了将筛选限制在有限形态和物候多样性范围内的重要性。
