Quantitative visualization of photosynthetic pigments in tea leaves based on Raman spectroscopy and calibration model transfer.

Abstract

Background Photosynthetic pigments participating in the absorption, transformation and transfer of light energy play a very important role in plant growth. While, the spatial distribution of foliar pigments is an important indicator of environmental stress, such as pests, diseases and heavy metal stress. Results In this paper, in situ quantitative visualization of chlorophyll and carotenoid was realized by combining the Raman spectroscopy with calibration model transfer, and a laboratory Raman spectral model was successfully extended to a portable field spectral measurement. Firstly, a nondestructive and fast model for determination of chlorophyll and carotenoid in tea leaf was established based on confocal micro-Raman spectrometer in the laboratory. Then the spectral model was extended to a real-time foliar map scanning spectra of a field portable Raman spectrometer through calibration model transfer, and the spectral variation between the confocal micro-Raman spectrometer in the laboratory and the portable Raman spectrometer were effectively corrected by the direct standardization (DS) algorithm. The portable map scanning Raman spectra of the tea leaves after the model transfer were got into the established quantitative determination model to predict the concentration of photosynthetic pigments at each pixel of the tea leaves. The predicted photosynthetic pigments concentration of each pixel was imaged to illustrate the distribution map of foliar pigments. Statistical analysis showed that the predicted pigment contents were highly correlated with the real contents. Conclusions It can be concluded that the Raman spectroscopy was applicable for in situ, non-destructive and rapid quantitative detecting and imaging of photosynthetic pigment concentration in tea leaves, and the spectral detection model established based on the laboratory Raman spectrometer can be applied to a portable field spectrometer for quantitatively imaging of the foliar pigments.

Plant phenotyping relevance

ラマン分光と校正モデル移転を用いて茶葉のクロロフィル・カロテノイド濃度を画素単位で定量・画像化する手法を開発し、携帯型装置への移転と実測値との相関も検証しているため、植物フェノタイピング手法が中心である。

Code and data availability

The article describes Raman spectroscopy of tea leaves with PLSR modeling and DS calibration transfer, but no public phenotype dataset, spectral data deposit, author code, or trained model is mentioned. Supplementary files contain only figures/tables (leaf positions, wavenumbers, scatter plots), not raw data or code.

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