Characteristics of Free Amino Acids (the Quality Chemical Components of Tea) under Spatial Heterogeneity of Different Nitrogen Forms in Tea (Camellia sinensis) Plants

Abstract

Nitrogen (N) forms are closely related to tea quality, however, little is known about the characteristics of quality chemical components in tea under the spatial heterogeneity of different N forms. In this study, a split-root system, high performance liquid chromatography (HPLC), and root analysis system (WinRHIZO) were used to investigate free amino acids (FAAs) and root length of tea plants under the spatial heterogeneity of different N forms. Uniform. (U.) ammonium (NH4+) (both compartments had NH4+), U. nitrate (NO3−) (both compartments had NO3−), Split. (Sp.) NH4+ (one of the compartments had NH4+), and Sp. NO3− (the other compartment had NO3−) were performed. The ranking of total FAAs in leaves were as follows: U. NH4+ > Sp. NH4+/Sp. NO3− > U. NO3−. The FAA characteristics of Sp. NH4+/Sp. NO3− were more similar to those of U. NO3−. The contents of the important FAAs (aspartic acid, glutamic acid, and theanine) that determine the quality of tea, increased significantly in U. NH4+. The total root length in U. NH4+ was higher than that in the other treatments. More serious root browning was found in U. NO3−. In conclusion, NH4+ improved the accumulations of FAAs in tea leaves, which might be attributed to the root development.