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.
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