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.

Raman Spectroscopy Detects Changes in Carotenoids on the Surface of Watermelon Fruits During Maturation

“…These distinct carotenoid signals also enabled the effective monitoring of four levels of maturity index in hot peppers by Raman spectroscopy ( Legner et al, 2021 ). Raman spectroscopy was recently explored for the in situ , non-destructive, and rapid quantitative analysis of photosynthetic pigments, chlorophyll, and carotenoids in tea leaves ( Zeng et al, 2021 ). Other characteristic vibrational bands observed at 520 and 1,047 cm −1 can be assigned to cellulose, 915 cm −1 to carbohydrates, 747 and 850 cm −1 to pectin, 1,267 and 1,606 cm −1 to phenylpropanoids or lignin, 1,670 cm −1 to protein and 1,286, 1,327, 1,386 and 1,439 cm −1 to CH 2 /CH 3 vibrations of aliphatic groups ( Supplementary Table S1 ).…”

Local Drivers Associated to Temporal Spectral Response of Chlorophyll-a in Mangrove Leaves

“…The photosystems I and II convert light energy into chemical energy through a reaction center. Chemical energy is stored in high caloric power compounds that give the leaf the green color, which is related to the leaf's ability to absorb the red and blue fractions of sunlight [29,30].…”

Raman Spectroscopy Applications in Grapevine: Metabolic Analysis of Plants Infected by Two Different Viruses

“…The assignment of bands of the most relevant peaks are reported in Table 1 . According to previous literature, most of the wavenumbers were related to photosynthetic pigments ( Zeng et al, 2021 ).…”