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

Jing Jin,Da Li,Yi-Qing Lv,Jia-Hao Zhou,Ding-Mi Chen,Wei-Zhong He,Jian-Hui Ye,Jing-Na Shao,Zai-Fa Shu,Ying Ye,Qing-Sheng Li

doi:10.3390/molecules26237158

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.

Highlights

Tea is a popular beverage with a unique taste, which is produced from the leaves of Camellia sinensis (L.) O
Greater proportions of TFG were reduced in the young shoots of ‘Longjing 43’, ‘Zhongming 192’, ‘Wanghai 1’ and ‘Jingning 1’ under all the shade treatments compared with TC, suggesting that the biosynthesis of flavonol glycosides was more sensitive to ambient light conditions
The present study investigated the effects of black net and colored net shade treatments on the flavonoid compositions of the young shoots of ‘Longjing 43’, ‘Zhongming 192’, ‘Wanghai 1’, ‘Jingning 1’ and ‘Zhonghuang 2’ tea cultivars

Summary

Introduction

Tea is a popular beverage with a unique taste, which is produced from the leaves of Camellia sinensis (L.) O. Flavanols and flavonols are the top two flavonoid subclasses in tea leaves [4]. The predominant flavanols in fresh tea leaves are catechins, accounting for 70~80% of tea polyphenols. Flavonols account for ~13% of tea polyphenols [5], mainly consisting of the O-glycosides of quercetin, kaempferol and myricetin [6]. The contents of flavonols and their glycosyl derivatives are much lower than catechins, flavonol glycosides are important bitter and astringent compounds in tea infusions, considering their extremely low thresholds and ability enhance the bitterness of caffeine [7]. The biosynthesis of flavonoids in regular tea cultivars was shown to be attenuated by low illumination [12]. Black net shade treatment is a common agronomic practice for producing high-grade green tea in several countries, such as China and Japan, due to its reduction effect on light intensity

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Conclusion