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Scutellaria baicalensis Georgi is a medicinal plant commonly used in China and other parts of East Asia. A high flavonoid content endows it with multiple beneficial biological activities that have anti-inflammatory, antibacterial, antiviral, and anti-COVID19 properties. Light-emitting diodes (LEDs) have been recognized as effective artificial lights to enhance plant growth and the accumulation of secondary metabolites for commercial plant production. However, little is known regarding the effects of LEDs on S. baicalensis. Here, we explored the effects of monochromatic blue light (B, 460 nm), monochromatic red light (R, 660 nm), white light (CK), and different combinations of R and B (R9B1, R7B3, R5B5, R3B7, and R1B9) on the growth of, and flavonoid accumulation in S. baicalensis. The results revealed that under R:B ratios of 9:1 or 7:3, the whole plant and roots of S. baicalensis seedlings had a higher biomass and flavonoid content. Targeted metabolomics analysis showed that 48 differentially expressed metabolites (DEMs) were verified between different groups, and the number of upregulated DEMs, particularly flavonoids, were higher in the R9B1 and R7B3 groups compared with the CK. Transcriptome data identified 1412 and 1508 differentially expressed genes (DEGs) in the R9B1 and R7B3 groups, respectively, in contrast to the CK. KEGG pathway analysis indicated that DEGs in both the R9B1 and R7B3 groups were primarily enriched in the phenylpropane biosynthesis, plant hormone signal transduction, flavonoid biosynthesis, starch and sucrose metabolism, galactose metabolism, cartenoid biosynthesis, zeatin biosynthesis, and nitrogen metabolism pathways. The qRT-PCR results showed that SbPAL , SbCLL-7 , SbCHI , SbFNS , and SbOMT encoding enzymes for the flavonoid biosynthesis pathway were significantly upregulated in S. baicalensis , which was consistent with the transcriptome data. Finally, based on correlation analysis between the main flavonoids in S. baicalensis and the genes encoding transcription factors and enzymes for the flavonoid metabolism pathway, a co-expression network map was developed, which provided a basis for the mining of light responsive genes related to flavonoids biosynthesis in S. baicalensis. This is the first report to articulate how the combination of red light and blue light influences the growth and secondary metabolism of S. baicalensis. • Combination of red and blue light (R9B1 and R7B3) increased root biomass of S. baicalensis and the flavonoids accumulation. • Some key enzyme genes and hormone signal related genes contribute to the phenotypic change and flavonoids accumulation. • Correlation analysis between TF/enzyme genes and the main flavonoids identified dozens of genes highly related to the flavonoids synthesis. [ABSTRACT FROM AUTHOR]

Abstract: Drought is a recurring phenomenon in north-central China. Long-term information about the history of drought is still limited because the instrumental records for many areas in north-central China go back only a few decades at best. This paper presents an earlywood width (EWW) chronology of Chinese pine (Pinus tabulaeformis) in the Shimen Mountains, Tianshui, eastern Gansu, north-central China. The climate-response analysis shows that April–July precipitation is the main factor limiting the earlywood growth of Chinese pines in the Shimen Mountains, Tianshui. Based on the EWW chronology, an April–July precipitation reconstruction for the period A.D. 1629–2008 was developed for Tianshui. The climate/tree-growth model accounts for 41.6% of the observed precipitation variance during the period 1953–2008. Spatial analysis shows that the precipitation reconstruction contains a strong common drought signal for north-central China. Reconstructed drought events are compared to a precipitation reconstruction of Huashan and historical archives for north-central China. The results reveal common climatic extremes over much of north-central China. Moreover, some dry periods coincided with solar minima or volcanic eruptions over the past several hundred years. Multi-taper spectral analysis reveals the existence of significant 3.8-year (90%), 3.1-year (95%), 2.7-year (99%), 2.4-year (99%) and 2.0-year (99%) periods of variability. The linkages to the Asian-Pacific Oscillation Index suggest regional precipitation variations may be linked to the East Asian summer monsoon circulations. [Copyright &y& Elsevier]