The Regulatory Effect of Nitrogen on the Formation and Accumulation of Secondary Metabolites in Different Genotypes of Camellia Sinensis (L.) Kuntze

Abstract

Soil N deficiency is one of the main constraints limiting high tea yields worldwide, particularly in Russia. In addition, high dosages of N fertilizers are widely applied for tea plantations, resulting in agrogenic transformation of soils, environmental pollution, and a decrease in tea quality. One of the ways to reduce dosages of N fertilizers is the development of new cultivars with high efficiency of N use. In this regard, the effect of genotype on biosynthesis and accumulation of valuable secondary metabolites in tea leaves was studied under optimal N supply and its deficiency in a potted experiment. The study was conducted on the most promising local tea cultivars (Kolkhida and Karatum) grown on brown forest acidic soils in the humid subtropics of Russia. Using high-performance liquid chromatography, the contents of catechins, flavanols, alkaloids, and theanine were evaluated in tea leaves. Our results showed that N availability stimulated the biosynthesis of theanine more than one order of magnitude and alkaloids (caffeine by three to five times and theobromine by two to three times) in both tea genotypes; however, it decreased the accumulation of several catechins and flavanols by on average 1.5–2 times. Under optimal N supply, the Kolkhida cultivar displayed higher accumulation of theanine (by 30–60%) and gallated catechins (by 50%) in the leaves; however, higher accumulation of alkaloids (caffeine and theobromine) was observed in the Karatum cultivar (by 10–20%). N deficiency resulted in greater accumulation of simple and gallated catechins, as well as rutin in the Kolkhida cultivar, as compared to the Katarum cultivar. However, the content of the studied metabolites in the Katarum cultivar was more stable under different nitrogen levels, indicating its lower susceptibility to N deficiency.