To elucidate the effects of UV-B radiation on the physiological mechanisms, gene expression, and spectral characteristics of sorghum seedlings, this study applied UV-B lamp irradiation to treat sorghum seedlings with different exposure durations: 0.5 h (UVB0.5), 1 h (UVB1), 1.5 h (UVB1.5), and 3 h (UVB3). A control group with no UV irradiation (UVB0) was included for comparison. Physiological indices, gene expression levels, and spectral information of the sorghum seedlings were analyzed. The results showed that enhanced UV-B radiation induced brown spots on the leaves and reduced chlorophyll content. Compared with UVB0, the net photosynthetic rate (Pn) and Fv/Fm values in UVB3 decreased by 148.5% and 97.7%, respectively. With prolonged UV-B radiation, H2O2 content initially decreased and then increased, while O2.-, MDA, Relative electrical conductivity, Soluble protein, and Soluble sugar contents all showed an upward trend, compared with UVB0, UVB3 exhibited increases of 250.1%, 124.9%, 153.8%, 11.8%, and 82.4% in these indices, respectively. Using the Random Frog algorithm for extracting characteristic spectral bands of sorghum leaves, MATLAB calculations revealed that the area of characteristic peaks decreased with longer UV-B radiation, with UVB3 showing an 80.1% reduction compared to UVB0. Transcriptomic analysis under UV-B radiation indicated that the expression levels of genes involved in photosynthetic response, including LHC, PSI, and PSII, were downregulated with increasing irradiation duration. In contrast, LOX, SPS, and GS genes showed partial discrepancies compared with their corresponding physiological indicators. The selected characteristic spectral data were closely correlated with chlorophyll content, photosynthetic capacity, osmoregulation-related physiological indices, and gene expression levels. In summary, enhanced UV-B radiation reduced photosynthetic pigments, decreased photosynthetic efficiency, downregulated gene expression, and hindered biomass accumulation. High-dose UV-B radiation led to reactive oxygen species accumulation and oxidative damage to membranes in sorghum plants. Furthermore, spectral information indicated significant differences in leaf spectral data among treatments, demonstrating that visible/near-infrared spectroscopy can characterize the extent of damage in sorghum seedlings through changes in plant metabolites and even through variations in photosynthetic performance indicators. Graphical Abstract

Spectral Correlation Analysis of UV-B-Treated Sorghum Seedlings Metabolic Physiology and NIR Characteristics

期刊论文
发表日期：

2026年6月22日

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Huaigang Guo,
Zhan Gao,
Jibang Hu,
Changjiang Zhao

摘要

To elucidate the effects of UV-B radiation on the physiological mechanisms, gene expression, and spectral characteristics of sorghum seedlings, this study applied UV-B lamp irradiation to treat sorghum seedlings with different exposure durations: 0.5 h (UVB0.5), 1 h (UVB1), 1.5 h (UVB1.5), and 3 h (UVB3). A control group with no UV irradiation (UVB0) was included for comparison. Physiological indices, gene expression levels, and spectral information of the sorghum seedlings were analyzed. The results showed that enhanced UV-B radiation induced brown spots on the leaves and reduced chlorophyll content. Compared with UVB0, the net photosynthetic rate (Pn) and Fv/Fm values in UVB3 decreased by 148.5% and 97.7%, respectively. With prolonged UV-B radiation, H₂O₂ content initially decreased and then increased, while O₂^.-, MDA, Relative electrical conductivity, Soluble protein, and Soluble sugar contents all showed an upward trend, compared with UVB0, UVB3 exhibited increases of 250.1%, 124.9%, 153.8%, 11.8%, and 82.4% in these indices, respectively. Using the Random Frog algorithm for extracting characteristic spectral bands of sorghum leaves, MATLAB calculations revealed that the area of characteristic peaks decreased with longer UV-B radiation, with UVB3 showing an 80.1% reduction compared to UVB0. Transcriptomic analysis under UV-B radiation indicated that the expression levels of genes involved in photosynthetic response, including LHC, PSI, and PSII, were downregulated with increasing irradiation duration. In contrast, LOX, SPS, and GS genes showed partial discrepancies compared with their corresponding physiological indicators. The selected characteristic spectral data were closely correlated with chlorophyll content, photosynthetic capacity, osmoregulation-related physiological indices, and gene expression levels. In summary, enhanced UV-B radiation reduced photosynthetic pigments, decreased photosynthetic efficiency, downregulated gene expression, and hindered biomass accumulation. High-dose UV-B radiation led to reactive oxygen species accumulation and oxidative damage to membranes in sorghum plants. Furthermore, spectral information indicated significant differences in leaf spectral data among treatments, demonstrating that visible/near-infrared spectroscopy can characterize the extent of damage in sorghum seedlings through changes in plant metabolites and even through variations in photosynthetic performance indicators.

Graphical Abstract