Improvement of soil acidification in tea plantations by long-term use of organic fertilizers and its effect on tea yield and quality

Reducing nitrogen fertilizer usage coupled with organic substitution improves soil quality and boosts tea yield and quality in tea plantations

BACKGROUND

The utilization of chemical fertilizers is a key measure for maintaining tea yield and quality, but excessive use has negative environmental impacts. The substitution of chemical fertilizer with organic fertilizer has been promoted to sustain crop yield and soil quality. However, knowledge gaps regarding the effects of organic substitution on soil quality and tea yield in tea plantations still exist.

RESULTS

A field experiment was conducted to investigate the influence of organic substitution treatments (i.e. 25% partial substitution: biogas slurry + green manure + formula fertilizer, BFG; sheep manure + formula fertilizer, OFF; 100% complete substitution: sheep manure + green manure, OG) on the soil quality, tea yield and quality, and nitrogen utilization efficiency in southwestern China. Results showed that all organic substitution treatments slightly increased soil pH, and significantly increased soil organic matter by 13.22-14.88% compared to conventional fertilization (CF). The BFG treatment was the most effective in enhancing the soil quality index, showing increases of 16.80%, 8.37% and 24.87% higher than the CF, OFF and OG treatments, respectively. Tea yield significantly increased under the BFG, OFF and OG treatments by 11.97%, 13.58% and 5.90% compared to CF, respectively. The BFG treatment increased the amino acid content by 7.78% and decreased the tea polyphenol/amino acid ratio by 6.87%. Additionally, the BFG, OFF and OG treatments greatly increased the nitrogen utilization efficiency of young sprouts by 70.71%, 82.54% and 34.28%, respectively.

CONCLUSION

Overall, partial organic substitution could effectively improve soil quality while maintaining tea yield. © 2024 Society of Chemical Industry.

Exploring the mechanisms of organic fertilizers on Cd bioavailability in rice fields: Environmental behavior and effect factors

The problem of paddy Cadmium (Cd) contamination is currently the focus of global research. Earlier researches have confirmed that utilization of organic fertilizers regulates Cd chemical fraction distribution by increases organic bound Cd. However, environmental behaviours of organic fertilizers in paddy are still lack exploration. Here, we critical reviewed previous publications and proposed a novel research concept to help us better understand it. Three potential impact pathways of utilization of organic fertilizers on the bioavailability of Cd are presented: (i) use of organic fertilizers changes soil physicochemical properties, which directly affects Cd bioavailability by changing chemical form of Cd(II); (ii) use of organic fertilizers increases soil nutrient content, which indirectly regulates Cd supply and bioaccumulation through ion adsorption and competition for ion-transport channels between nutrients and Cd; and (iii) use of organic fertilizers increases activity of microorganisms and efflux of rice root exudates, which indirectly affects Cd bioavailability of through complexation and sequestration of these organic materials with Cd. Meanwhile, dissolved organic matter (DOM) in the rhizosphere of rice is believed to be the key to revealing the effects of organic fertilizers on Cd. DOM is capable of adsorption and complexation-chelation reactions with Cd and the fractionation of Cd(II) is regulated by DOM. Molecular mass, chemical composition, major functional groups and reaction sequence of DOM determine the formation and solubilization of DOM-Cd complexes.

The effect of novel biotechnological vermicompost on tea yield, plant nutrient content, antioxidants, amino acids, and organic acids as an alternative to chemical fertilizers for sustainability

In this study, the performance of a novel organic tea compost developed for the first time in the world from raw tea waste from tea processing factories and enriched with worms, beneficial microorganisms, and enzymes was tested in comparison to chemical fertilizers in tea plantations in Rize and Artvin provinces, where the most intensive tea cultivation is carried out in Turkey. In the field trials, the developed organic tea vermicompost was incorporated into the root zones of the plants in the tea plantations in amounts of 1000 (OVT1), 2000 (OVT2) and 4000 (OVT4) (kg ha-1). The experimental design included a control group without OVT applications and positive controls with chemical fertilizers (N: P: K 25:5:10, (CF) 1200 kg ha-1) commonly used by local growers. The evaluation included field trials over two years. The average yields obtained in two-year field trials in five different areas were: Control (6326), OVT1 (7082), OVT2 (7408), OVT4 (7910), and CF (8028) kg ha-1. Notably, there was no significant statistical difference in yields between the organic (at 4000 kg ha-1 ) and chemical fertilizers (at 1200 kg ha-1). The highest nutrient contents were obtained when CF and OVT4 were applied. According to the average values across all regions, the application of OVT4 increased the uptake of 63% N, 18% K, 75% P, 21% Mg, 19% Na, 29% Ca, 28% Zn, 11% Cu and 24% Mn compared to the control group. The application of chemical fertilizers increased the uptake of 75% N, 21% K, 75% P, 21% Mg, 28% Na, 27% Ca, 30% Zn, 18% Cu and 31% Mn compared to the control group. The organic fertilizer treatment had the lowest levels of antioxidants compared to the control groups and the chemical fertilizers. It was also found that the organic fertilizer increased the levels of amino acids, organic acids and chlorophyll in the tea plant. Its low antioxidant activity and proline content prepared them for or protected them from stress conditions. With these properties, the biotechnologically developed organic tea compost fertilizer has proven to be very promising for tea cultivation and organic plant production.

The Ability of Different Tea Tree Germplasm Resources in South China to Aggregate Rhizosphere Soil Characteristic Fungi Affects Tea Quality

It is generally recognized that the quality differences in plant germplasm resources are genetically determined, and that only a good "pedigree" can have good quality. Ecological memory of plants and rhizosphere soil fungi provides a new perspective to understand this phenomenon. Here, we selected 45 tea tree germplasm resources and analyzed the rhizosphere soil fungi, nutrient content and tea quality. We found that the ecological memory of tea trees for soil fungi led to the recruitment and aggregation of dominant fungal populations that were similar across tea tree varieties, differing only in the number of fungi. We performed continuous simulation and validation to identify four characteristic fungal genera that determined the quality differences. Further analysis showed that the greater the recruitment and aggregation of Saitozyma and Archaeorhizomyces by tea trees, the greater the rejection of Chaetomium and Trechispora, the higher the available nutrient content in the soil and the better the tea quality. In summary, our study presents a new perspective, showing that ecological memory between tea trees and rhizosphere soil fungi leads to differences in plants' ability to recruit and aggregate characteristic fungi, which is one of the most important determinants of tea quality. The artificial inoculation of rhizosphere fungi may reconstruct the ecological memory of tea trees and substantially improve their quality.

Effects of Photoperiod and Light Quality on Germination and Growth of Camellia sinensis 'HuangKui'

Light, as a critical environmental factor, plays a pivotal role in photosynthesis, ultimately influencing the timing of bud flush in tea plants. However, the synergistic effects of different photoperiods and light qualities on the timing of bud flush in the albino tea cultivar 'HuangKui' (later germination variety) remain unknown. Thus, the objective of this study was to investigate the effects of different photoperiods (12L/12D, 14L/10D, 16L/8D, and 18L/6D, where L = the number of daylight hours and D = the number of hours of darkness) and ratios of red (R) to blue (B) light (R/B 1:1, R/B 1:2, R/B 1:3, and R/B 2:1) on the germination and growth of the albino tea variety 'HuangKui'. In our study, we examined how different photoperiods and red light and blue light affected tea germination and growth by investigating the timing of bud flush, photosynthesis, chlorophyll content, and growth indicators. First, our study showed that 'HuangKui' germinated 4 days, 2 days, and 1 day earlier under the 16L/8D photoperiod at the one bud and one leaf period compared with plants cultivated under the 12L/12D, 14L/10D, and 18L/6D photoperiods under light simulating the solar spectrum. Also, the growth of 'HuangKui' was maximumly promoted under the 16L/8D photoperiod treatment. Additionally, the earliest germination of 'HuangKui' was observed for the 16L/8D photoperiod under the R/B 2:1 (red/blue) treatment compared with the other treatments. Moreover, the greatest plant height, length of the new shoots, and new leaf areas were detected in the albino tea variety 'HuangKui' under R/B 2:1. Moreover, the contents of auxin (indole acetic acid, IAA) and trans-zeatin (tZ) under R/B 2:1 were significantly higher than those under the R/B 1:1 and control treatments with the 16L/8D photoperiod. Additionally, the auxin-related expression levels of CsIAA13, CsGH3.1, CsAUX1, and CsARF2 under the R/B 2:1 treatment were significantly higher than those in the control. The expression of CsARR-B, a positive regulator of cytokinin-related genes, was significantly higher under the R/B 2:1 treatment than under the control treatment, while the opposite result was found for the expression of the negative regulator CsARR-A. Therefore, the R/B 2:1 treatment with the 16L/8D photoperiod was an appropriate means of timing the bud flush for the albino tea variety 'HuangKui', which may be related to IAA or tZ signal transduction. In conclusion, our research offers a novel lighting strategy that promotes the germination and growth of albino tea cultivars.

Recruitment and Aggregation Capacity of Tea Trees to Rhizosphere Soil Characteristic Bacteria Affects the Quality of Tea Leaves

There are obvious differences in quality between different varieties of the same plant, and it is not clear whether they can be effectively distinguished from each other from a bacterial point of view. In this study, 44 tea tree varieties (Camellia sinensis) were used to analyze the rhizosphere soil bacterial community using high-throughput sequencing technology, and five types of machine deep learning were used for modeling to obtain characteristic microorganisms that can effectively differentiate different varieties, and validation was performed. The relationship between characteristic microorganisms, soil nutrient transformation, and tea quality formation was further analyzed. It was found that 44 tea tree varieties were classified into two groups (group A and group B) and the characteristic bacteria that distinguished them came from 23 genera. Secondly, the content of rhizosphere soil available nutrients (available nitrogen, available phosphorus, and available potassium) and tea quality indexes (tea polyphenols, theanine, and caffeine) was significantly higher in group A than in group B. The classification result based on both was consistent with the above bacteria. This study provides a new insight and research methodology into the main reasons for the formation of quality differences among different varieties of the same plant.

Organic management pattern improves microbial community diversity and alters microbial network structure in karst tea plantation

Soil microbiomes play a crucial role in enhancing plant growth, health, and overall agricultural productivity. Nevertheless, the influence of distinct agricultural management practices on the microbial diversity and community structure within tea (Camellia sinensis) plantations has remained enigmatic. This study postulates that organic agricultural management models can enhance microbial diversity and optimise the microbial community structure within tea plantations, indirectly augmenting soil fertility and tea quality. We employed metagenome technology and conducted molecular ecological network analysis to explore the impact of organic management, pollution-free management, and conventional management on the microbial network structure of tea plantation soil in Weng'an County in the southwestern karst region. Soils subjected to organic management exhibited a higher relative abundance of soil microbial and carbohydrate-active enzyme functional genes than those subjected to other management regimes. Additionally, the relative abundance and diversity of dominant bacteria and keystone species were notably higher under organic management than under the other management regimes. Correlation analysis showed that soil microorganisms were closely related to soil fertility and tea quality, respectively. One-way analysis of variance and the structural equation modelling results showed significant variability in soil fertility under the three agricultural management modes and that soil fertility and soil microbial diversity had a direct impact on tea quality (P > 0.05). In conclusion, this study underscores the profound impact of management modes on microbial diversity and community structure within tea plantations. These management practices alter the soil microbial network structure and potential function, ultimately regulating the microecological dynamics of the soil community in tea plantations.

Acidification induce chemical and microbial variation in tea plantation soils and bacterial degradation of the key acidifying phenolic acids

Camellia sinensis is an important economic plant grown in southern subtropical hilly areas, especially in China, mainly for the production of tea. Soil acidification is a significant cause of the reduction of yield and quality and continuous cropping obstacles in tea plants. Therefore, chemical and microbial properties of tea growing soils were investigated and phenolic acid-degrading bacteria were isolated from a tea plantation. Chemical and ICP-AES investigations showed that the soils tested were acidic, with pH values of 4.05-5.08, and the pH negatively correlated with K (p < 0.01), Al (p < 0.05), Fe and P. Aluminum was the highest (47-584 mg/kg) nonessential element. Based on high-throughput sequencing, a total of 34 phyla and 583 genera were identified in tea plantation soils. Proteobacteria and Acidobacteria were the main dominant phyla and the highest abundance of Acidobacteria was found in three soils, with nearly 22% for the genus Gp2. Based on the functional abundance values, general function predicts the highest abundance, while the abundance of amino acids and carbon transport and metabolism were higher in soils with pH less than 5. According to Biolog Eco Plate™ assay, the soil microorganisms utilized amino acids well, followed by polymers and phenolic acids. Three strains with good phenolic acid degradation rates were obtained, and they were identified as Bacillus thuringiensis B1, Bacillus amyloliquefaciens B2 and Bacillus subtilis B3, respectively. The three strains significantly relieved the inhibition of peanut germination and growth by ferulic acid, p-coumaric acid, p-hydroxybenzoic acid, cinnamic acid, and mixed acids. Combination of the three isolates showed reduced relief of the four phenolic acids due to the antagonist of B2 against B1 and B3. The three phenolic acid degradation strains isolated from acidic soils display potential in improving the acidification and imbalance in soils of C. sinensis.

Characterization of Key Odorants in Lushan Yunwu Tea in Response to Intercropping with Flowering Cherry

Lushan Yunwu tea (LSYWT) is a famous green tea in China. However, the effects of intercropping tea with flowering cherry on the overall aroma of tea have not been well understood. In this study, headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS) was used for analysis. A total of 54 volatile compounds from eight chemical classes were identified in tea samples from both the intercropping and pure-tea-plantation groups. Principal component analysis (PCA), orthogonal partial least-squares discriminant analysis (OPLS-DA), and odor activity value (OAV) methods combined with sensory evaluation identified cis-jasmone, nonanal, and linalool as the key aroma compounds in the intercropping group. Benzaldehyde, α-farnesene, and methyl benzene were identified as the main volatile compounds in the flowering cherry using headspace solid-phase microextraction/gas chromatography-mass spectrometry (HS-SPME/GC-MS). These findings will enrich the research on tea aroma chemistry and offer new insights into the product development and quality improvement of LSYWT.

Understanding and exploring the diversity of soil microorganisms in tea (Camellia sinensis) gardens: toward sustainable tea production

Leaves of Camellia sinensis plants are used to produce tea, one of the most consumed beverages worldwide, containing a wide variety of bioactive compounds that help to promote human health. Tea cultivation is economically important, and its sustainable production can have significant consequences in providing agricultural opportunities and lowering extreme poverty. Soil parameters are well known to affect the quality of the resultant leaves and consequently, the understanding of the diversity and functions of soil microorganisms in tea gardens will provide insight to harnessing soil microbial communities to improve tea yield and quality. Current analyses indicate that tea garden soils possess a rich composition of diverse microorganisms (bacteria and fungi) of which the bacterial Proteobacteria, Actinobacteria, Acidobacteria, Firmicutes and Chloroflexi and fungal Ascomycota, Basidiomycota, Glomeromycota are the prominent groups. When optimized, these microbes' function in keeping garden soil ecosystems balanced by acting on nutrient cycling processes, biofertilizers, biocontrol of pests and pathogens, and bioremediation of persistent organic chemicals. Here, we summarize research on the activities of (tea garden) soil microorganisms as biofertilizers, biological control agents and as bioremediators to improve soil health and consequently, tea yield and quality, focusing mainly on bacterial and fungal members. Recent advances in molecular techniques that characterize the diverse microorganisms in tea gardens are examined. In terms of viruses there is a paucity of information regarding any beneficial functions of soil viruses in tea gardens, although in some instances insect pathogenic viruses have been used to control tea pests. The potential of soil microorganisms is reported here, as well as recent techniques used to study microbial diversity and their genetic manipulation, aimed at improving the yield and quality of tea plants for sustainable production.

Changes of physiological characteristics, element accumulation and hormone metabolism of tea leaves in response to soil pH

Soil acidification is very likely to affect the growth of tea trees and reduce tea yield. In this study, we analyzed the effects of soils with different pH on the physiological characteristics of tea leaves and determined the multi-element content and hormone metabolomes of tea leaves by ICP-MS and LC-MS/MS, based on which we further analyzed their interaction. The results showed that increasing soil pH (3.29~5.32) was beneficial to increase the available nutrient content of the rhizosphere soil of tea tree, improve the antioxidant enzyme activity and photosynthesis capacity of tea tree leaves, and promote the growth of tea tree. Orthogonal partial least squares discriminant analysis (OPLS-DA) and bubble characteristics analysis were used to screen key elements and hormones for the effect of pH on tea leaves, which were further analyzed by redundancy analysis (RDA) and interaction network. The results showed that an increase in soil pH (3.29~5.32) favored the accumulation of seven key elements (C, K, Ca, Mg, Mn, P, S) in tea tree leaves, which in turn promoted the synthesis of six key hormones (salicylic acid, salicylic acid 2-O-β-glucoside, tryptamine, 2-oxindole-3-acetic acid, indole-3-acetic acid, trans-zeatin-O-glucoside). It can be seen that the increase in soil pH (3.29~5.32) enhanced the resistance of the tea tree itself, improved the photosynthesis ability of the tea tree, and effectively promoted the growth of the tea tree.

Transcriptomic Analysis of the Effect of Pruning on Growth, Quality, and Yield of Wuyi Rock Tea

Pruning is an important agronomic measure in tea plantation management. In this study, we analyzed the effect of pruning on gene expression in tea leaves from a transcriptomics perspective and verified the results of a transcriptomic analysis in terms of changes in physiological indicators of tea leaves. The results showed that pruning enhanced the gene expression of nine metabolic pathways in tea leaves, including fatty acid synthesis and carbohydrate metabolism, nitrogen metabolism, protein processing in the endoplasmic reticulum, and plant hormone signal transduction, thereby promoting the growth of tea plants and increasing tea yield. However, pruning reduced the gene expression of nine metabolic pathways, including secondary metabolites biosynthesis, flavonoid biosynthesis, phenylpropanoid biosynthesis, and sesquiterpenoid and triterpenoid biosynthesis, and lowered the content of caffeine, flavonoids, and free amino acids in tea plant leaves. In conclusion, pruning could promote the growth of tea plants and increase the yield of tea, but it was not conducive to the accumulation of some quality indicators in tea leaves, especially caffeine, flavonoids, and free amino acids, which, in turn, reduced the quality of tea. This study provides an important theoretical reference for the management of agronomic measures in tea plantations.

Effects of pruning on tea tree growth, tea quality, and rhizosphere soil microbial community

Pruning is an important agronomic measure in tea plantation management. This study analyzed the effects of pruning on tea tree growth, tea quality, rhizosphere soil physicochemical indexes, microbial communities, and metabolic pathways. The results showed that pruning was beneficial for promoting tea tree growth and increasing tea yield, but not for the synthesis and accumulation of quality-related compounds in tea leaves. After pruning, organic matter, available phosphorus content and catalase, acid phosphatase, and sucrase activities in rhizosphere soil were significantly higher than those in unpruned tea trees, while total phosphorus, total potassium, and available nitrogen content were significantly lower than those in unpruned tea trees. The results of microbial community analysis of tea rhizosphere soil showed that the key changed characteristic microorganisms after pruning were Haliangium, Acidicaldus, Reyranella, Acidobacterium, Aquicella, and Granulicella, and the key changed characteristic microbial metabolic pathways were ko00072, ko00473, ko00750, ko01055, ko00521, and ko02040. Furthermore, the results found that pruning promoted Haliangium, Acidicaldus, and Reyranella abundances, ko00072, ko00473, and ko00750, respectively, microbial metabolic pathways in tea trees rhizosphere soil, and reduced Acidobacterium, Granulicella, and Aquicella abundance, ko01055, ko00521, and ko02040, respectively, microbial metabolic pathways, thereby increasing the activities of soil catalase, acid phosphatase, and sucrase, improving soil organic matter decomposition efficiency and available phosphorus content, and promoting tea yield, but not synthesis and accumulation of quality-related compounds in tea leaves. This study provides an important theoretical reference for the management of agronomic measures in tea plantations. IMPORTANCE Pruning is an important agronomic measure in tea cultivation and management. We found that pruning was beneficial to increase tea yield, but it would reduce tea quality, especially the content of polyphenols, theanine, flavonoids, and free amino acids in tea leaves was reduced. The reason for this phenomenon was that pruning promotes the enrichment of special functional microorganisms and the enhancement of special metabolic pathways in the soil, leading to changes in the nutrient cycle in the soil.

Application of Multi-Perspectives in Tea Breeding and the Main Directions

Tea plants are an economically important crop and conducting research on tea breeding contributes to enhancing the yield and quality of tea leaves as well as breeding traits that satisfy the requirements of the public. This study reviews the current status of tea plants germplasm resources and their utilization, which has provided genetic material for the application of multi-omics, including genomics and transcriptomics in breeding. Various molecular markers for breeding were designed based on multi-omics, and available approaches in the direction of high yield, quality and resistance in tea plants breeding are proposed. Additionally, future breeding of tea plants based on single-cellomics, pangenomics, plant-microbe interactions and epigenetics are proposed and provided as references. This study aims to provide inspiration and guidance for advancing the development of genetic breeding in tea plants, as well as providing implications for breeding research in other crops.

Differences in microbial community structure and metabolic activity among tea plantation soils under different management strategies

Introduction

Microorganisms play an important role in the multifunctionality of soil ecosystems. Soil microbial diversity and functions have a great impact on plant growth and development. The interactions between tea trees and soil microbiota can be linked with planting patterns and management strategies, whose effects on soil microbial community structure and metabolites are still unclear.

Methods

Here we used amplicon sequencing and metabolomic analysis to investigate the differences in soil microbial composition and metabolites among three tea production systems: organic, non-organic, and intercropping.

Results

We detected significant differences among the three systems and found that Firmicutes, Proteobacteria, Acidobacteriota, Actinobacteriota and Chloroflexi were the main bacteria in the three soil groups, although they varied in relative abundance. Acidobacteria bacterium increased significantly in the organic and intercropping groups. For fungi, Ascomycota and Basidiomycota were the main differential fungal phyla. Fungi alpha-diversity in the non-organic group was significantly higher than that in the other two groups, and was correlated with multiple soil physical and chemical factors. Moreover, network analysis showed that bacteria and fungi were strongly correlated. The changes in soil microorganisms caused by management and planting patterns may affect soil quality through corresponding changes in metabolites. Metabolomic analysis showed differences in metabolite composition among different groups. It was also found that the arachidonic acid metabolic pathway was affected by changes in soil microorganisms, and may further affect soil quality in an essential manner.

Discussion

Planting patterns and management strategies may significantly affect soil microorganisms and therefore metabolites. Changes in soil microorganisms, especially in fungi, may alter soil quality by affecting soil physicochemical properties and metabolites. This study will provide new insights into soil quality monitoring from a microbiological perspective.

Effects of peach branch organic fertilizer on the soil microbial community in peach orachards

Peach branches is a by-product of peach industry. Making peach branch waste into peach branch organic fertilizer (PBOF) is a promising strategy of ecological utilization. In this study, the effects of PBOF on the yield and quality of peach fruit, chemical properties of bulk soil, and soil bacterial communities were investigated in a peach orchard. The results showed that the yield and sugar/acid ratio of two high-level PBOF treatments (SDH.4 and SKR.4) was higher than no fertilization treatment (CK), but there was no significant difference compared to the commercial organic fertilizer treatment (SYT.4). Moreover, the three fertilizer treatments increased soil nutrients such as soil organic matter (SOM) and available potassium (AK), compared to CK. Furthermore, PBOF increased the relative abundance of beneficial bacteria, and enhanced the soil bacterial co-occurrence pattern and the potential function of bacterial communities to degrade exogenous compounds. In addition, thanks to the local policy of encouraging the use of PBOF, the use cost of PBOF is lower than commercial organic fertilizer, which is conducive to the development of ecological agriculture.

Effects of Magnesium on Transcriptome and Physicochemical Index of Tea Leaves

Magnesium (Mg) is one of the essential elements for the growth of tea tree and is extremely important for its development. In this study, we investigated the effect of Mg on the transcriptome and physicochemical indexes of tea leaves, and the results showed that Mg could significantly affect the gene expression of tea leaves. The results of Orthogonal Partial Least-Squares Discriminant Analysis (OPLS-DA) model analysis showed that a total of 300 key genes (Variable Importance for the Projection, VIP > 1) were screened under different concentrations of Mg treatment, among which 140 genes were up-regulated and 160 genes were down-regulated. The bubble map was used to screen the characteristic genes from the above key genes, and a total of 121 representative characteristic genes were obtained, mainly involving 9 metabolic pathways. Among them, gene expression of three metabolic pathways, including porphyrin metabolism, alpha-linolenic acid metabolism and photosynthesis, showed an increasing trend with the increase of Mg concentration, while gene expression of four metabolic pathways, including biosynthesis of secondary metabolites, anthocyanin biosynthesis, ABC transporters, pentose and glucuronate interconversions, showed a decreasing trend. The results of physiological index analysis showed that with the increase of Mg concentration, the photosynthetic physiological index, theanine and soluble sugar content of tea leaves showed an increasing trend, while the content of tea polyphenol, flavone and caffeine showed a decreasing trend. The results of TOPSIS analysis showed that the physiological indexes of tea trees most affected by Mg were chlorophyll, tea polyphenols and flavonoids, while the metabolic pathways most affected by Mg on gene expression were the metabolic pathways and biosynthesis of secondary metabolites. It can be seen that the effects of Mg on tea tree were mainly related to photosynthesis and synthesis of secondary metabolites, and Mg was beneficial for improving the photosynthetic capacity of tea tree, enhancing the accumulation of primary metabolites, and thus increasing tea yield. However, Mg was not conducive to the synthesis of secondary metabolites of tea tree and the accumulation of main quality indexes of tea leaves.

Metabolomics analysis of the effect of acidification on rhizosphere soil microecosystem of tea tree

Acidification can seriously affect the growth of tea trees and the yield and quality of tea leaves. In this study, we analyzed the effects of acidification on the physicochemical properties, microorganisms and metabolites of tea rhizosphere soils with different pH values, and the results showed that with the increase of soil pH, the organic matter content, cation exchange capacity, microbial biomass carbon, microbial biomass nitrogen, microbial respiration intensity, bacterial number and actinomyces number in tea rhizosphere soil all showed an increasing trend, while the fungi number decreased. The results of soil metabolite analysis showed that 2376, 2377 and 2359 metabolites were detected in tea rhizosphere soil with pH values of 3.29, 4.74 and 5.32, respectively, and the number of similar compounds reached 2331, accounting for more than 98%. The results of soil metabolite content analysis showed that with the increase of soil pH, the total contents of metabolite of tea rhizosphere soil increased significantly. The results of correlation analysis between physicochemical indexes of soil and microorganisms and soil metabolites showed that physicochemical indexes of soil and microorganisms were significantly correlated with 221 soil metabolites, among which 55 were significantly positively correlated and 166 were significantly negatively correlated. Based on correlation interaction network analysis, 59 characteristic compounds were obtained and divided into 22 categories, among which 7 categories compounds showed a significant increasing trend with the increase of soil pH, while the other 15 categories compounds showed the opposite trend. Based on the functional analysis of characteristic metabolites, this study found that with the increase of soil pH in tea rhizosphere, the diversity and number of soil microorganisms increased, and the cyclic ability of C and N of tea rhizosphere soil was enhanced, which in turn might lead to the enhancement of resistance of tea tree and promote the growth of tea tree.