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Intercropping is a widely recognised technique that contributes to agricultural sustainability. While intercropping leguminous green manure offers advantages for soil health and tea plants growth, the impact on the accumulation of theanine and soil nitrogen cycle are largely unknown. The levels of theanine, epigallocatechin gallate and soluble sugar in tea leaves increased by 52.87% and 40.98%, 22.80% and 6.17%, 22.22% and 29.04% in intercropping with soybean–Chinese milk vetch rotation and soybean alone, respectively. Additionally, intercropping significantly increased soil amino acidnitrogen content, enhanced extracellular enzyme activities, particularly β‐glucosidase and N‐acetyl‐glucosaminidase, as well as soil multifunctionality. Metagenomics analysis revealed that intercropping positively influenced the relative abundances of several potentially beneficial microorganisms, including Burkholderia, Mycolicibacterium and Paraburkholderia. Intercropping resulted in lower expression levels of nitrification genes, reducing soil mineral nitrogen loss and N2O emissions. The expression of nrfA/H significantly increased in intercropping with soybean–Chinese milk vetch rotation. Structural equation model analysis demonstrated that the accumulation of theanine in tea leaves was directly influenced by the number of intercropping leguminous green manure species, soil ammonium nitrogen and amino acid nitrogen. In summary, the intercropping strategy, particularly intercropping with soybean–Chinese milk vetch rotation, could be a novel way for theanine accumulation. Summary statement: The theanine content of tea leaves increased by 52.87% and 40.98% when intercropped with soybean–Chinese milk vetch rotation and soybean alone, respectively. The accumulation of theanine in tea leaves was directly influenced by the intercropping green manure species and their quantity, as well as the levels of soil ammonium nitrogen and amino acid nitrogen. [ABSTRACT FROM AUTHOR]

Microorganisms play essential roles in soil-ecosystem multifunctionality. However, the contribution of their community assembly processes, composition, diversity, and keystone species to ecosystem multifunctionality is unclear, especially in tea-plantation ecosystems. In order to assess the effects of various intercropping patterns (tea-plant monoculture and tea plants, respectively, intercropped with soybean, soybean—milk vetch, soybean—red clover, and soybean—smooth vetch) on soil rare and abundant taxa, a field experiment was carried out. We found that tea plantation intercropping with legumes improved the soil-ecosystem multifunctionality by altering the soil environment, and ultimately benefited nutrient absorption and quality improvement of tea leaves. Whether it was in bacteria or fungi, rare taxa had a higher proportion of deterministic processes in community assembly than abundant taxa. Additionally, intercropping practices changed the soil environment, and rare bacterial taxa were assembled and shifted from variable selection to homogeneous dispersal. Intercropping practices significantly changed the bacterial and fungal communities' composition, and rare taxa had higher α-diversity than abundant taxa. Increasing legume species in intercropping practice enhanced community dissimilarity to the tea monoculture by affecting soil pH, ammonium nitrogen, and nitrate nitrogen. Rare bacterial and fungal β-diversity exhibited stronger positive relationships with ecosystem multifunctionality (both average and multi-threshold approaches) compared to the corresponding abundant taxa. Furthermore, ecosystem multifunctionality under different intercropping practices was closely related to the keystone rare operational taxonomic units, especially rare bacterial species of Chloroflexi. Our results emphasize the disparate feedbacks of rare and abundant taxa to diverse intercropping practices, as well as the important connection between rare bacterial taxa and ecosystem multifunctionality. [ABSTRACT FROM AUTHOR]

The effects of metal pollution on tea are of great concern to consumers. We apply Geographic information systems technology to study the distribution of heavy metal elements in tea plantation ecosystems in Jiangsu Province, explore the relationships among metals in the soil, tea leaves and tea infusions, and assess the human safety risks of metals. The concentrations of nine metals in a soil–tea leaves–tea infusion system were studied at 100 randomly selected tea plantations in Jiangsu Province, China. Concentrations of selected metals, zinc (Zn), nickel (Ni), manganese (Mn), chromium (Cr) and copper (Cu), were quantified using an inductively coupled plasma-optical emission spectrometer (ICP-OES), and cadmium (Cd), arsenic (As), plumbum (Pb) and mercury (Hg) were quantified using inductively coupled plasma-mass spectrometry (ICP-MS). Arc-Map 10.3 was used for the spatial analysis of metals in soil, tea leaves and tea infusions. We found that the contents of Mn, Ni and Zn are high level in soil, tea leaves and tea infusions. The Mn level showed a spatial distribution pattern with greater concentrations at the junction of Nanjing and Yangzhou, southwest of Changzhou and west of Suzhou. The hazard index (HI) values in north-central Nanjing, southern Suzhou, southwestern Changzhou and northern Lianyungang were relatively greater. The Zn, Ni, Mn, Cr and Cu levels in the soil–tea infusion system were 17.3, 45.5, 54.5, 1.5 and 14.3%, respectively. The order of the leaching rates of the elements was Ni > Cr > Zn > Mn > Cu. The relative contribution ratios of HI were in the order of Mn > Ni > Cu > Zn > Cr > Pb > Cd > As > Hg. In tea infusions, the Mn level has the greatest potential health risks to consumers. Moreover, using Csoil it was inferred that the safety thresholds of Zn, Ni, Mn, Cr and Cu in soil were 27,700, 50, 1230, 493,000 and 16,800 mg L–1, respectively. The content of heavy metals in soil and tea varies greatly in different regions of Jiangsu Province, 92% of the soil has heavy metal content that meets the requirements of pollution-free tea gardens, 91% of tea samples met the requirements of green food tea. The thresholds for Ni (50 mg L−1) and Mn (1230 mg L−1) can be used as maximum limits in tea plantation soils. The consumption of tea infusions did not pose metal-related risks to human health. [ABSTRACT FROM AUTHOR]

Background: Intercropping, especially with legumes, as a productive and sustainable system, can promote plants growth and improves the soil quality than the sole crop, is an essential cultivation pattern in modern agricultural systems. However, the metabolic changes of secondary metabolites and the growth in tea plants during the processing of intercropping with soybean have not been fully analyzed. Results: The secondary metabolomic of the tea plants were significant influence with intercropping soybean during the different growth stages. Especially in the profuse flowering stage of intercropping soybean, the biosynthesis of amino acids was significantly impacted, and the flavonoid biosynthesis, the flavone and flavonol biosynthesis also were changed. And the expression of metabolites associated with amino acids metabolism, particularly glutamate, glutamine, lysine and arginine were up-regulated, while the expression of the sucrose and D-Glucose-6P were down-regulated. Furthermore, the chlorophyll photosynthetic parameters and the photosynthetic activity of tea plants were higher in the tea plants-soybean intercropping system. Conclusions: These results strengthen our understanding of the metabolic mechanisms in tea plant's secondary metabolites under the tea plants-soybean intercropping system and demonstrate that the intercropping system of leguminous crops is greatly potential to improve tea quality. These may provide the basis for reducing the application of nitrogen fertilizer and improve the ecosystem in tea plantations. [ABSTRACT FROM AUTHOR]

Tea plant often suffers from low temperature induced damage during its growth. How to improve the cold resistance of tea plant is an urgent problem to be solved. Nitric oxide (NO), γ-aminobutyric acid (GABA) and proline have been proved that can improve the cold resistance of tea plants, and signal transfer and biosynthesis link between them may enhance their function. NO is an important gas signal material in plant growth, but our understanding of the effects of NO on the GABA shunt, proline and NO biosynthesis are limited. In this study, the tea roots were treated with a NO donor (SNAP), NO scavenger (PTIO), and NO synthase inhibitor (L-NNA). SNAP could improve activities of arginine decarboxylase, ornithine decarboxylase, glutamate decarboxylase, GABA transaminase and Δ1-pyrroline-5-carboxylate synthetase and the expression level of related genes during the treatments. The contents of putrescine and spermidine under SNAP treatment were 45.3% and 37.3% higher compared to control at 24 h, and the spermine content under PTIO treatment were 57.6% lower compare to control at 12 h. Accumulation of proline of SNAP and L-NNA treatments was 52.2% and 43.2% higher than control at 48 h, indicating other pathway of NO biosynthesis in tea roots. In addition, the NO accelerated the consumption of GABA during cold storage. These facts indicate that NO enhanced the cold tolerance of tea, which might regulate the metabolism of the GABA shunt and of proline, associated with NO biosynthesis. [ABSTRACT FROM AUTHOR]

Intercropping is an important agroforestry practice that can not only increase biodiversity, improve microenvironment and resource utilization, but also improve crop yield and quality. In this paper, the soil environmental characteristics and tea quality of three tea-fruit intercropping patterns (loquat-tea, waxberry-tea, and citrus-tea) and pure tea garden were studied. The soil samples of 0–10 cm, 10–20 cm and 20–30 cm depths in different seasons (spring and autumn) were collected to analyze the physicochemical characteristics of the soil. Corresponding tea bud samples in spring were collected for the determination of the main chemical components. The soil nutrient of the three intercropping patterns was higher than that of the single tea plantation, while the heavy metal content and pH value were opposite. Moreover, the difference in soil nutrient and pH under intercropping patterns were correlated with the sampling period. The tea plantation under intercropping patterns had higher free amino acid content, lower catechins content and the ratio of phenol to amino acids, which is conducive to the formation of green tea quality. Under the patterns of loquat-tea intercropping and citrus-tea intercropping, soil nutrients were higher than that of waxberry-tea intercropping. For the tea plantation soil heavy metals, waxberry-tea intercropping and citrus-tea intercropping had lower concentration than that of loquat-tea intercropping. However, citrus-tea intercropping is superior to the other two intercropping patterns for tea quality. These results may enhance the understanding of tea-fruit intercropping patterns for improving the soil environment of tea plantation and the quality of tea. [ABSTRACT FROM AUTHOR]

Intercropping has been recommended as a beneficial cropping practice for improving soil characteristic and tea quality. However, there is limited research on the effects of intercropping fruit trees on soil chemical properties, soil aggregate structure, and tea quality components. In this study, intercropping fruit trees, specifically loquats and citrus, had a significant impact on the total available nutrients, AMN, and AP in soil. During spring and autumn seasons, the soil large-macroaggregates (>2 mm) proportion increased by 5.93% and 19.03%, as well as 29.23% and 19.14%, respectively, when intercropping loquats and citrus. Similarly, intercropping waxberry resulted in a highest small-macroaggregates (0.25 mm–2 mm) proportion at 54.89% and 77.32%. Soil aggregate stability parameters of the R 0.25 , MWD, and GMD were generally considered better soil aggregate stability indicators, and significantly improved in intercropping systems. Intercropping waxberry with higher values for those aggregate stability parameters and lower D values, showed a better soil aggregate distribution, while intercropping loquats and citrus at higher levels of AMN and AP in different soil aggregate sizes. As the soil aggregate sizes increased, the AMN and AP contents gradually decreased. Furthermore, the enhanced levels of amino acids were observed under loquat, waxberry, and citrus intercropping in spring, which increased by 27.98%, 27.35%, and 26.21%, respectively. The contents of tea polyphenol and caffeine were lower under loquat and citrus intercropping in spring. These findings indicated that intercropping fruit trees, specifically loquat and citrus, have immense potential in promoting the green and sustainable development of tea plantations. • Intercropping fruit trees increase soil total available nutrients, AMN and AP. • Intercropping loquat and citrus significant increase >2 mm soil large aggregate. • Intercropping waxberry showed a better distribution of soil aggregates. • Intercropping loquat and citrus increase AMN and AP in different aggregate sizes. • Intercropping enhanced tea quality, especially intercropping loquat and citrus in spring. [ABSTRACT FROM AUTHOR]

To understand the effects of geographic locations, cultivation altitude, slope, and aspect on secondary metabolites in tea leaves, 78 tea samples were randomly collected from Southern Jiangsu region, China, and catechins, caffeine, and free amino acids were examined. The results showed that samples from the farther north had higher contents of TC, EGCG + GCG, ECG + CG and the ratios of ETC to NTC, while had lower contents of free amino acids, leading to more bitterness and astringency taste in tea. Furthermore, more free amino acids were accumulated in tea cultivated in hilly areas due to shorter sun exposure time and lower intensity than plain areas with the rotation of the earth formed a natural shade management effect, whereas more TC in plain areas. Principal Component Analysis (PCA) grouped the 78 tea samples into three clusters and further confirmed that tea samples from a similar geographical environment exhibited a similar constituent of major secondary metabolites. These results might be useful for providing references to regional tea plantation planning, tea plantations location selection and geographical environment management. • Catechins and free amino acids contents in tea are affected by cultivation location. • Tea cultivated in hilly areas gets more free amino acid due to topographic shading. • Tea cultivated in plain areas gets more TC due to longer sun exposure time. • Tea cultivated in similar geographical environment gets similar secondary metabolites. [ABSTRACT FROM AUTHOR]