Optimization of nutrient management improves productivity, quality and sustainability of albino tea cultivar Baiye-1

Proper nutrient management is crucially important to the sustainable development of tea production. Compared to normal green-leaf cultivars, albino tea cultivars produce green tea of superior quality characterized by high contents of amino acids as a result of the hydrolysis of chloroplast proteins at albinism. However, the advantage of albino tea cultivars was offset by inferior growth and yield performance because of low contents of chlorophylls and limited photosynthesis capacity. Our understanding about the nutrition characteristics of albino tea cultivars was very limited. A four-year field experiment was conducted to develop proper nutrient management for Baiye-1 to overcome its weakness of low productivity without a tradeoff in tea quality and environmental risks. The nutrient management schemes were formulated by optimizing the rate and ratio of nitrogen (N), phosphorus, potassium and magnesium together with substitution of chemical fertilizers with organic manures. The total amounts of nutrients in the optimized schemes were reduced by 25% compared to the local farmers’ practice (FP). Results showed that optimized rates and ratio of nutrients together with partial substitution of chemical fertilizers with rapeseed cake manure more considerably improved albino tea yield, the contents of free amino acids, total polyphenol and catechins relative to FP. Partial substitution of chemical fertilizers with commercial livestock manure decreased tea quality, which was likely caused by a dilution effect of increasing tea yield and decreasing N status of tea plants. Full organic substitution of chemical fertilizers by rapeseed cake manure improved tea yield and quality but had relatively low agronomic efficiency and profit. The effect of optimized nutrient management schemes was associated with the improvement of nutritional status in tea plants. The present work demonstrated that the optimization of nutrient management considerably improved albino tea yield, quality and profit while decreased the application rate of fertilizers and the intensity of greenhouse gas emissions

Nitrogen transport and assimilation in tea plant (Camellia sinensis): a review

Nitrogen is one of the most important nutrients for tea plants, as it contributes significantly to tea yield and serves as the component of amino acids, which in turn affects the quality of tea produced. To achieve higher yields, excessive amounts of N fertilizers mainly in the form of urea have been applied in tea plantations where N fertilizer is prone to convert to nitrate and be lost by leaching in the acid soils. This usually results in elevated costs and environmental pollution. A comprehensive understanding of N metabolism in tea plants and the underlying mechanisms is necessary to identify the key regulators, characterize the functional phenotypes, and finally improve nitrogen use efficiency (NUE). Tea plants absorb and utilize ammonium as the preferred N source, thus a large amount of nitrate remains activated in soils. The improvement of nitrate utilization by tea plants is going to be an alternative aspect for NUE with great potentiality. In the process of N assimilation, nitrate is reduced to ammonium and subsequently derived to the GS-GOGAT pathway, involving the participation of nitrate reductase (NR), nitrite reductase (NiR), glutamine synthetase (GS), glutamate synthase (GOGAT), and glutamate dehydrogenase (GDH). Additionally, theanine, a unique amino acid responsible for umami taste, is biosynthesized by the catalysis of theanine synthetase (TS). In this review, we summarize what is known about the regulation and functioning of the enzymes and transporters implicated in N acquisition and metabolism in tea plants and the current methods for assessing NUE in this species. The challenges and prospects to expand our knowledge on N metabolism and related molecular mechanisms in tea plants which could be a model for woody perennial plant used for vegetative harvest are also discussed to provide the theoretical basis for future research to assess NUE traits more precisely among the vast germplasm resources, thus achieving NUE improvement

Quality-related constituents in tea (Camellia sinensis (L.) O. Kuntze) as affected by the form and concentration of nitrogen and the supply of chloride

Free amino acids, polyphenols and caffeine are particularly important groups of compounds for taste and quality of green tea infusions. The influence of nutrient supply on their accumulation in tea plants was investigated under controlled conditions. Plants supplied with NO3- grew much slower than those receiving NH4+ or NH4++NO3-. Concentrations of free amino acids in young tea shoots were considerably larger in NH4+- than in NO3--fed plants, attributing to the larger absorption rate of NH4+ than NO3- and their compartmental assimilation. Biosynthesis of catechins was reduced by the highest N supply due to more carbon resources were allocated to N metabolism. With the highest N supply, relatively more absorbed N was allocated to synthesis of arginine and glutamine with low C : N ratios to improve carbon economy. Application of Cl reduced the concentrations of total free amino acid and theanine in young shoots but did not affect theanine in roots, NH4+ uptake rate and GS activity. It is suggested that Cl might influnce translocation of theanine from root to shoot and its further catabolism in the young shoots

Aluminium absorption by intact roots of the Al-accumulating plant Camellia sinensis L.

Tea (Camellia sinensis L.) is an Al-accumulating plant, taking up a large amount of aluminium (Al). However, information about Al transport into the roots is limited. In the present study, the absorption of Al by intact roots of young tea plants as well as the effects of fluoride, and solution pH were investigated. The absorption of Al by intact tea roots can be described by two phases, a rapid phase in the first 60 min followed by a slower phase for at least 24 h, which is not different from those observed in non-Al-accumulating plants. This pattern remained more or less the same after citric acid desorption for 30 min, being non-linear until the end of the initial 60 min. Absorption of Al was significantly influenced by solution pH, increasing remarkably from pH 3.2 to 4.8. A combined supply of Al and F in the nutrient solution significantly reduced the uptake of Al

Accumulation of phenolic compounds as influenced by N supply: a case study on catechins in green tea (Camellia sinensis)

Concentration of free amino acids (AA) and polyphenols (PP) represent important components of green tea quality. As the accumulation of AA and PP, representing primary and secondary metabolites in tea plants, respectively, is governed interactively by the nitrogen (N) supply and carbon (C) status, providing an ideal system for studying the impact of C/N allocation on green tea quality. Saplings were cultivated hydroponically with 0.3, 0.75, 1.5 or 4.5 mmol L-1 N. Activities of glutamine synthetase (GS), phenylalanine ammonia lyase (PAL), and phosphoenolpyruvate carboxylase (PEPC) were determined, as were the concentrations of AA, PP and soluble sugars. Concentrations of free amino acids increased with enhancing N supply, but the AA profile was shifted towards AA characterised by low C/N ratios (arginine, glutamine) instead of theanine, a unique non-protein AA dominating in C. sinensis. High N supply significantly reduced the concentrations of PP in young shoots, which was accompanied by decreasing availability of carbohydrates (soluble sugars). Analysis of the C and N status and selected enzyme activities, combined with path coefficient analysis of variables associated with C and N metabolism, demonstrated increasing deviation of C flux to AA under abundant N supply. Accumulation of AA and PP strongly depended on the N status and the balance was shifted toward increasing synthesis of AA associated with enhanced growth, while investment of C in secondary metabolites is not changing proportionally under the condition of ample N supply. While the resulting higher AA/PP ratio is principally associated with improved green tea quality, the increasing fraction of AA of low C/N ratio, namely arginine, is counterproductive in this respect

Accumulation of phenolic compounds as influenced by N supply: a case study on catechins in green tea (Camellia sinensis)

Concentration of free amino acids (AA) and polyphenols (PP) represent important components of green tea quality. As the accumulation of AA and PP, representing primary and secondary metabolites in tea plants, respectively, is governed interactively by the nitrogen (N) supply and carbon (C) status, providing an ideal system for studying the impact of C/N allocation on green tea quality. Saplings were cultivated hydroponically with 0.3, 0.75, 1.5 or 4.5 mmol L-1 N. Activities of glutamine synthetase (GS), phenylalanine ammonia lyase (PAL), and phosphoenolpyruvate carboxylase (PEPC) were determined, as were the concentrations of AA, PP and soluble sugars. Concentrations of free amino acids increased with enhancing N supply, but the AA profile was shifted towards AA characterised by low C/N ratios (arginine, glutamine) instead of theanine, a unique non-protein AA dominating in C. sinensis. High N supply significantly reduced the concentrations of PP in young shoots, which was accompanied by decreasing availability of carbohydrates (soluble sugars). Analysis of the C and N status and selected enzyme activities, combined with path coefficient analysis of variables associated with C and N metabolism, demonstrated increasing deviation of C flux to AA under abundant N supply. Accumulation of AA and PP strongly depended on the N status and the balance was shifted toward increasing synthesis of AA associated with enhanced growth, while investment of C in secondary metabolites is not changing proportionally under the condition of ample N supply. While the resulting higher AA/PP ratio is principally associated with improved green tea quality, the increasing fraction of AA of low C/N ratio, namely arginine, is counterproductive in this respect

Effect of Integrated Use of Rapeseed Cake, Biochar and Chemical Fertilizers on Root Growth, Nutrients Use Efficiency and Productivity of Tea

The tea root system plays a key role in the uptake of nutrients and water from the soil. The effect of integrated fertilizers (Control (CK) (no fertilizers), 100% NPK, 100% NPK withbiochar (NPK + B), 50% NPK with 50% rapeseed cake (NPK + RC), and 100% rapeseed cake (RC))on alterations in root growth characteristics and soil physical properties, nutrient uptake, NUE, and biomass production of tea (Longjing 43) was studied in an Alfisol at the greenhouse of the China Tea Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou, during 2020–2021. The results showed that the conjunctive application of mineral fertilizers with rapeseed cake (NPK + RC) resulted in significant (p < 0.05) reductions in soil penetration resistance (14.8%) and bulk density (8.7%) and improvement in porosity (9.9%) compared to the control. NPK + RC recorded significantly higher (p < 0.05) root surface area, root volume, root tips, root length, and root CEC of tea than NPK (15%, 20%, 27%, 6%, and 11%) and control (40%, 165%, 49%, 68%, and 12%). The combinedapplication of RC and NPK fertilizer significantly decreased the specific root surface area (137%) and specific root length (66.8%) compared to the control. Root, stem, leaves, and total biomass were improved by integrated fertilization compared to the control and mineral fertilization. The nutrient content (N,P,K), nutrient uptake, NUE, nutrient uptake per root length, volume, and surface area of tea plants under NPK + RC and NPK + B were significantly (p < 0.05) higher than RC and CK. Therefore, the integrated use of rapeseed cake with mineral fertilization in Alfisol should be practiced in tea plantations to improve soil physical environment, root proliferation and root CEC, nutrient uptake, and NUE and achieve higher tea biomass production through the efficient exploitation of nutrients

Response of Nutritional Status and Tea Quality to the Rate and Substitution of Chemical Fertilizers with Organic Manure

Proper fertilization is important to sustainable tea production. A field experiment was conducted to investigate the response of quality components in a chlorotic tea variety (Zhonghuang-2) to rates of fertilizers and the substitution ratio of chemical fertilizers by organic manure based on rapeseed cake. Chlorotic tea varieties have unique metabolic characteristics and produce superior tea containing high contents of free amino acids. Results showed that fertilization significantly increased yield and contents of free amino acid (TFAA) but reduced contents of total polyphenol (TP) and the ratio of TP/TFAA. Contents of TFAA and TP and the TP/TFAA ratio were closely related to nitrogen (N) concentrations in plant tissues in response to the rate of N fertilizers. The results suggest that the quality-related components in the chlorotic tea variety respond to fertilizers in a similar way as normal tea varieties. The optimal rates of N, phosphorus (P), and potassium fertilizers were discussed and recommended based on the response of quality components of tea and the contents of nutrients in plants and soil. The full substitution of chemical fertilizers by organic manure showed no special benefit on tea quality and had lower N and P agronomic use efficiency due to a low bioavailability of nutrients. The partial substitution of chemical fertilizers by organic manure significantly improved tea yield, quality, profit, and economic and environmental sustainability

Characterization of Young Shoot Population, Yield, and Nitrogen Demands of Tea (Camellia sinensis L.) Harvested under Different Standards

The quality of green tea is greatly influenced by the harvest standards for young shoots. The present field experiment was conducted to characterize the young shoot populations, yields, and nitrogen (N) demands of tea plants subjected to four different harvest standards, i.e., buds with one, two, or three young expanding leaves (referred to as B1L, B2L, and B3L, respectively) and a combination of B1L and B3L (B1L/B3L) throughout the year. Weight per shoot was closely related to the number of expanding leaves and was greater in B3L than B1L and B2L, and also greater in summer and autumn than in spring, whereas B1L revealed the greatest young shoot density and highest N concentration. Annual shoot yield and shoot N content were largest in B3L and decreased in the following order: B3L > B2L ≈ B1L/B3L > B1L. However, in the early spring the shoot density, yield, and shoot N content of B1L were much higher than those of B3L. The harvest of B3L significantly reduced the biomass of brown roots and its ratio against the above-ground biomass compared to other harvest standards, suggesting a decreased allocation of carbon to the root system due to seasonal removal. The N dilution curve (Nys = a × Yysb, where Nys is the shoot N content and Yys is the shoot yield) of spring tea differed markedly from those of summer and autumn teas, suggesting different coordination properties for shoot growth and N supply among the seasons. The annual harvest index (NHI) measured by 15N traces ranged between 0.18 and 0.23, indicating relatively low N allocation to young shoots, whereby large proportions (58.2–66.9% of the total 15N absorption) remained in the plant at the end of the experiment. In conclusion, the seasonal distribution of the shoot density, weight per shoot, yield, and N demands vary with harvest standards and highlight the importance of N precision management in tea production to be finely tuned to meet the changes in harvest season and requirements