College of Instrumentation and Electrical Engineering, Jilin University, Changchun, Jilin, 130061, China; Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Science, Chongqing, 400714, China.
Citrus Research Institute, Southwest University, Chongqing, 400712, China.
Plant Physiol Biochem. 2023 Jan;194:52-59. doi: 10.1016/j.plaphy.2022.10.032. Epub 2022 Nov 8.
Low temperature stress, in the form of chilling and freezing, is one of the major environmental factors impacting on citrus yield, which changes plant's water state and results in the crops' sub-health or injury. The innovative terahertz (THz) spectroscopy and imaging based sensing technology has been shown to be a suitable tool for plant leaf water status determination, due to THz radiation's innate sensitivity to hydrogen bond vibration in aqueous solutions, which is usually related to plant phenotype change. We demonstrate experimentally that the THz absorption coefficient of leaf could be used for distinguishing plant's physiological stress status, exhibiting clear decreasing or increasing trend under chilling or freezing stress respectively. The underlying rationale might be that membrane damage shows a diverse pattern, changing the intra- or extra-cellular liquid environments, likely being linked to the various THz spectral characteristics. There were different adaptations in leaf morphology, leading to different leaf density, which in turn affects the water volume fraction. Moreover, different patterns of the dynamic equilibrium state of free water and bound water under chilling and freezing treatment were revealed by THz spectroscopy. Here, THz spectroscopic monitoring has shown unique potential for judging citrus's low temperature stress state through bio-water detection and discrimination.
低温胁迫（冷胁迫和冻胁迫）是影响柑橘产量的主要环境因素之一，它会改变植物的水分状态，导致作物处于亚健康或受伤状态。基于太赫兹（THz）光谱和成像的创新传感技术已被证明是一种用于植物叶片水分状态测定的合适工具，因为太赫兹辐射对水溶液中氢键振动具有固有敏感性，这通常与植物表型变化有关。我们通过实验证明，叶片的太赫兹吸收系数可用于区分植物的生理胁迫状态，在冷胁迫或冻胁迫下分别表现出明显的降低或增加趋势。其潜在原理可能是细胞膜损伤呈现出多样化的模式，改变了细胞内或细胞外的液体环境，可能与太赫兹光谱的各种特征有关。叶片形态的不同适应性导致了不同的叶片密度，进而影响了水体积分数。此外，太赫兹光谱技术还揭示了在冷胁迫和冻胁迫处理下自由水和束缚水动态平衡状态的不同模式。在这里，太赫兹光谱监测通过生物水分检测和区分，显示出判断柑橘低温胁迫状态的独特潜力。
