The effects of soil acidification on the phoD-harboring microbial community and the fractions of soil phosphorus in tea plantation soils are still unclear. In this study, tea plantations with different soil pH were used as the research object to analyze changes in soil phosphorus fractions, phoD gene abundance, phoD-harboring microbial community composition, and their relationship with tea yield and quality. The results showed that the content of tea polyphenols, caffeine, free amino acids, theanine, and tea yield decreased significantly after acidification. Moreover, the content of total phosphorus in the acidified soil also decreased significantly. Further analysis of soil phosphorus fractions showed that the acidification of the tea plantation soil resulted in a significant decrease in the content of different types of labile and moderately labile phosphorus, whereas the content of non-labile phosphorus exhibited the opposite trend. As the content of soil NaHCO₃-Po, NaOH-Po, Resin-Pi, NaHCO₃-Pi, NaOH-Pi, and HCl-Pi decreased significantly after acidification, its organic and inorganic phosphorus content also decreased significantly. Its phosphorus activation capacity decreased by 4.75% after soil acidification. Soil acidification significantly reduced the diversity of phoD-harboring microbial communities by 61.89%. Analysis of the phoD-harboring microbial community composition suggested that the microbial abundance of Acidobacteria and Proteobacteria showed a decreasing trend in acidified soils, while for Nitrospirae, Verrucomicrobia, Actinobacteria, and Planctomycetes, it showed an increasing trend. Correlation analysis showed that microorganisms with significantly decreasing abundance in tea plantation soils were significantly and positively correlated with soil pH, labile phosphorus, moderately labile phosphorus, phosphorus activation coefficients, and tea yield and quality after soil acidification. It is evident that soil acidification inhibited soil phosphorus availability by shifting phoD-harboring microbial community composition in tea plantation soils, thus affecting the yield and quality of above-ground tea leaves.

During the production of Wuyi rock tea, withering and fermentation play a crucial role in the primary processing of the tea, greatly influencing the development of its distinct taste characteristics. In this study, Rougui (Camellia sinensis) was selected as the research object to investigate the effects of withering and fermentation on metabolites and taste characteristics in tea leaves. The findings revealed that a total of 1249 metabolites were detected in Rougui leaves at various processing stages, of which only 40 key metabolites were significantly altered. The process of withering and fermentation is crucial to increase the content of organic acids, plumerane, alkaloids, nucleotides and derivatives, amino acids and derivatives, and free fatty acids in the leaves of Rougui and to decrease the content of saccharides, phenolic acids, flavonols, flavones, and flavanols, which in turn enhances the mellowness, fresh and brisk taste, and aroma of tea and attenuates the saccharides, bitterness, and astringency. Withering and fermentation had the greatest effect on the bitterness and astringency of Rougui taste characteristics, followed by mellowness. It can be seen that withering and fermentation were extremely important for the development of Rougui’s special taste characteristics. The present study provides important support for optimizing Rougui processing and the formation of its special taste characteristics.

Fertilization is a necessary measure in the cultivation and management of the tea bush, and the use of different fertilizers significantly affects the quality of tea leaves. In this study, 100% chemical fertilizer (CF), 100% organic fertilizer (OF), and 50% chemical fertilizer + 50% organic fertilizer (COF) were used to analyze the effects of different fertilizer treatments on the quality indices and volatile component compositions of tea leaves. The results showed that COF treatment significantly increased the content of water extract, tea polyphenols, theanine, free amino acids, and soluble sugar, but decreased the content of total flavonoids and caffeine, indicating that COF treatment has an advantage in improving the overall quality of tea leaves. Analysis of volatile components showed that different fertilizer treatments significantly affected the content of eleven characteristic metabolites in tea bush leaves, of which four characteristic metabolites were most abundant under CF treatment, eight under OF treatment, and only one under COF treatment. The odor characteristics and their intensity analyses showed that the 11 characteristic volatile components mainly exhibited three types of odor characteristics, such as woody, green, and floral, of which OF treatment enhanced woody and green intensities, while CF treatment enhanced floral intensity. Taken together, different fertilizer treatments could regulate the quality indices and volatile components of tea leaves, while the use of chemical fertilizers or organic fertilizers alone was conducive to enhancing the intensity of individual special odor characteristics in tea leaves. Overall, the combination of chemical fertilizers and organic fertilizers was more conducive to the improvement of tea quality. This study provides a theoretical basis for optimizing the fertilization strategy of tea bushes to improve tea quality.

Magnesium plays an important role in regulating the growth and quality of tea trees. However, the effect of magnesium regulation on changes in the aroma quality of tea tree leaves remains unknown. In this study, the volatile compounds of tea leaves under different magnesium concentrations were determined to obtain the characteristic volatile compounds that changed significantly and their odor characteristics and to explore the effect of magnesium regulation on the aroma quality of tea leaves. The results showed that magnesium significantly enhanced the content of 15 characteristic volatile compounds in tea tree leaves, especially heptyl formate and t-geraniol. The 15 characteristic volatile compounds mainly showed five kinds of odor characteristics, such as fruity, green, floral, pungent, woody, and burnt; magnesium regulation critically increased floral, fruity, and green odor characteristics. This study lays an important foundation for the application of exogenous magnesium ions to regulate tea aroma quality.

Soil acidification is a major environmental issue facing tea plantations in China. However, the molecular mechanisms by which acidification affects tea plant growth through rhizosphere microbial functional proteins remain unclear. In this study, tea plantation soils with different pH gradients were selected. Tea plant growth indicators, soil available nutrient contents, microbial abundance, and microbial physiological indicators were comprehensively measured, and metaproteomics was employed to analyze soil protein composition, functions, and microbial origins. The results showed that as soil pH increased from 3.54 to 5.37, the leaf chlorophyll content, leaf area, hundred-bud weight, and yield of tea plants were all significantly increased (p < 0.05). Soil available nitrogen, phosphorus, and potassium contents, as well as microbial biomass carbon, nitrogen, and phosphorus, also significantly increased in parallel. The abundances of bacteria and actinomycetes increased with rising pH, whereas fungal abundance decreased. A total of 6558 soil proteins were identified by metaproteomics, among which 236 were characterized as signature proteins (VIP > 1). Functional enrichment analysis revealed that proteins significantly upregulated with increasing pH were mainly enriched in pathways such as cysteine and methionine metabolism, galactose metabolism, and glycerophospholipid metabolism, with sulfur-containing amino acid metabolism contributing as much as 88.31%. Microbial source tracking indicated that Bacillus and Burkholderia were the primary contributors to these signature proteins; their abundances were significantly higher in the pH 5.37 treatment than in the low-pH treatment, with contribution rates of 100% and 43.73%, respectively. Partial least squares structural equation modeling (PLS-SEM) further revealed that signature microorganisms sequentially promoted microbial physiological indicators, nutrient availability, and tea plant growth by positively influencing the abundance and function of signature proteins. In conclusion, increasing soil pH to 5.37 can enhance the nutrient cycling capacity in the rhizosphere and increase tea yield. This phenomenon is closely related to the increase in the number of Bacillus and Burkholderia species, as well as the enhancement of key pathways such as sulfur-containing amino acid metabolism. This study provides molecular targets and a theoretical basis for the ecological remediation of acidified tea plantation soils.

The tea tree root system is an important tissue for nutrient uptake, accumulation, and transport, and pH is an important environmental factor regulating the growth of tea tree (Camellia sinensis). However, the physiological and molecular mechanisms of how the tea tree root system responds to pH are unclear. In this study, Tieguanyin tea tree was used as the research object, and treated with different pH values to determine the morphological indexes of the tea plant root system and systematically study the physiological and molecular mechanisms of the effect of pH on the growth of the tea plant root system using transcriptomics in combination with metabolomics. The results showed that total root length, root surface area, root volume, total root tips, root fork number, and root crossing number of root crosses of the tea plant root system increased significantly (p < 0.05) with increasing pH. Transcriptome analysis showed that a total of 2654 characteristic genes were obtained in response to pH regulation in the root system of the tea plant, which were mainly enriched in six metabolic pathways. Metabolomics analysis showed that the metabolites with the highest contribution in differentiating tea plant responses to different pH regulations were mainly heterocyclic compounds, amino acids and derivatives, alkaloids, and flavonoids. Interaction network analysis showed that pH positively regulated the metabolic intensity of the MAPK signaling pathway (plant, plant hormone signal transduction, and RNA degradation pathway), positively regulated the content of the heterocyclic compound, amino acids and derivatives, and alkaloids, and positively regulated tea plant root growth. However, it negatively regulated ribosome, protein processing in the endoplasmic reticulum, and phenylpropanoid biosynthesis pathway intensity, and negatively regulated the flavonoid content. This study reveals the physiological and molecular mechanisms of the tea plant root system in response to pH changes and provides an important theoretical basis for the cultivation and management of tea plants in acidified tea plantations.