Terahertz Spectroscopy in Assessing Temperature-Shock Effects on Citrus

Abstract

Rapid assessment of physiological status is a precondition for addressing biological stress in trees so that they may recover. Environmental stress can cause water deficit in plants, while terahertz (THz) spectroscopy is sensitive to changes in aqueous solutions within organisms. This has given the THz sensor a competitive edge for evaluating plant phenotypes, especially under similar environmental stress, if there are existing differences in the corresponding THz information. In this study, we utilized THz technology in association with traditional weighing methods to explore physiological changes in citrus leaves under different temperature, duration, and stress treatment conditions. It was found that the higher the temperature and the longer the exposure duration, the more severe the reduction in the relative absorption coefficient. There was a positive correlation between the trends and the increase in the ion permeability of cells. In addition, based on the effective medium theory, THz spectral information can be transformed into information on free water and bound water in the leaves. Under different treatment conditions, water content shows different trends and degrees of change on the time scale, and accuracy was verified by traditional weighing methods. These findings revealed that characteristics of THz information can serve as a simple and clear indicator for judging a plant's physiological status.

Plant phenotyping relevance

THz分光法で柑橘葉の生理状態・水分状態を推定し、従来の秤量法で精度検証しており、植物表現型取得法が中心である。

Code and data availability

The paper reports THz spectroscopy measurements of citrus leaves under temperature stress, but no public dataset, code, or model deposit is described. The Data Availability Statement states raw data are available only from the corresponding author upon reasonable request. An MDPI supplementary materials URL exists, but

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