RESUMO
Tea is a popular beverage with characteristic functional and flavor qualities, known to be rich in bioactive metabolites such as tea polyphenols and theanine. Recently, tea varieties with variations in leaf color have been widely used in agriculture production due to their potential advantages in terms of tea quality. Numerous studies have used genome, transcriptome, metabolome, proteome, and lipidome methods to uncover the causes of leaf color variations and investigate their impacts on the accumulation of crucial bioactive metabolites in tea plants. Through a comprehensive review of various omics investigations, we note that decreased expression levels of critical genes in the biosynthesis of chlorophyll and carotenoids, activated chlorophyll degradation, and an impaired photosynthetic chain function are related to the chlorina phenotype in tea plants. For purple-leaf tea, increased expression levels of late biosynthetic genes in the flavonoid synthesis pathway and anthocyanin transport genes are the major and common causes of purple coloration. We have also summarized the influence of leaf color variation on amino acid, polyphenol, and lipid contents and put forward possible causes of these metabolic changes. Finally, this review further proposes the research demands in this field in the future.
RESUMO
In order to ensure the suitable shade model for 'Huangjinya' tea plant in Shandong Province, black or blue shading net at 55%, 70% or 85% shading rates was selected to recover tea garden in summer and autumn, then micro-climate of tea garden, leaf color, chlorophyll fluorescence parameters, growth status and biochemical composition of tea shoots were investigated.The results showed that compared with the control, light intensity and air temperature in tea garden, leaf temperature of tea plants in different shading treatments significantly decreased, while air humidity in tea garden increased. The contents of chlorophyll in the tea leaves were obviously increased with increasing the shading rate, which resulted in the leaf color becoming green. The yellowing characteristics and biochemical quality of 'Huangjinya' tea plants could be well kept in 55% shading treatments. In 70% shading treatments, 'Huangjinya' tea plants had better growth situation and higher yield with no photo-inhibition. Compared with the blue shading treatments, black shading treatments could obviously promote the growth of 'Huangjinya' tea plants, keep yellowing characteristics, and improve the quality. Therefore, the 70% black shading treatment (daily PAR values of 1.2-3.5 ten thousand lx) was appropriate for promoting the growth of 'Huangjinya' tea plants at the seedling stage. For mature tea plants, the 55% black shading treatment (daily PAR values of 1.8-5.5 ten thousand lx) could be used to keep the yellowing characteristics and to improve biochemical quality effectively, so as to give full play to its variety characteristics, to achieve goal of high quality and high yield.
