Screening the Key Region of Sunlight Regulating the Flavonoid Profiles of Young Shoots in Tea Plants (Camellia sinensis L.) Based on a Field Experiment

Abstract

Both UV and blue light have been reported to regulate the biosynthesis of flavonoids in tea plants; however, the respective contributions of the corresponding regions of sunlight are unclear. Additionally, different tea cultivars may respond differently to altered light conditions. We investigated the responses of different cultivars (‘Longjing 43’, ‘Zhongming 192’, ‘Wanghai 1’, ‘Jingning 1’ and ‘Zhonghuang 2’) to the shade treatments (black and colored nets) regarding the biosynthesis of flavonoids. For all cultivars, flavonol glycosides showed higher sensitivity to light conditions compared with catechins. The levels of total flavonol glycosides in the young shoots of different tea cultivars decreased with the shade percentages of polyethylene nets increasing from 70% to 95%. Myricetin glycosides and quercetin glycosides were more sensitive to light conditions than kaempferol glycosides. The principal component analysis (PCA) result indicated that shade treatment greatly impacted the profiles of flavonoids in different tea samples based on the cultivar characteristics. UV is the crucial region of sunlight enhancing flavonol glycoside biosynthesis in tea shoots, which is also slight impacted by light quality according to the results of the weighted correlation network analysis (WGCNA). This study clarified the contributions of different wavelength regions of sunlight in a field experiment, providing a potential direction for slightly bitter and astringent tea cultivar breeding and instructive guidance for practical field production of premium teas based on light regimes.

Effects of Different Shading Treatments on the Biomass and Transcriptome Profiles of Tea Leaves (Camellia sinensis L.) and the Regulatory Effect on Phytohormone Biosynthesis

“…The increase in TC was mainly attributed to the increase in EGCG, with the increased percentage being 15%. Thus, flavonol glycosides were more sensitive to the growth light condition than catechin compounds, which was consistent with the previous studies (Jin et al, 2021;Ye et al, 2021). The flavonoid composition of BN was close to that of BKN, suggesting that blue net shading treatment exerted a similar effect on flavonoid compounds in tea leaves to black net shading treatment.…”

“…The flavonoid composition of BN was close to that of BKN, suggesting that blue net shading treatment exerted a similar effect on flavonoid compounds in tea leaves to black net shading treatment. The comparable effects of blue and black net shading treatments on the reduction of flavonol glycosides in tea leaves have been reported (Jin et al, 2021).…”

“…The information about the effect of light condition on the production yield of tea plants is scarce. In our previous study, flavonol glycosides were greatly reduced under both black and blue net shading treatments, while the production yield of tea plants under blue net shading treatment was apparently higher than that of black net shading treatment (Jin et al, 2021). The impact of light condition on the biomass of tea plants and the light-mediated regulatory effect on the biosynthesis of phytohormones in tea plants need further investigations.…”

“…China). The shading treatments were implemented according to the method of our previous work (Jin et al, 2021;Ye et al, 2021). After shading for 15 days (29 June 2021), the tea plants were at the stage of two leaves and one bud, and the second leaves basipetal from the apical bud were randomly collected.…”

“…In addition to tea breeding (Xia et al, 2020), agronomic practices are efficient to reduce the bitter and astringent taste of tea, e.g., shading treatment and fertilization (Ye et al, 2022). Black net shading treatment is effective to decrease the accumulation of bitter and astringent compounds like flavonol glycosides in tea leaves (Jin et al, 2021). However, the growth of tea plants is also attenuated or even adversely impacted due to the weak light condition.…”