Comprehensive Analysis of Fresh Tea (Camellia Sinensis Cv. Lingtou Dancong) Leaf Quality Under Different Nitrogen Fertilization Regimes

This study examined fresh leaves from Lingtou tea plants to assess non-volatile and volatile substances, as well as gene expression, affected by fertilization with nitrogen at rates of 0, 150, 300, and 450 kg/ha. Results showed that applying nitrogen at 450 kg/ha increased total polyphenols (TPs) and free amino acids (AAs) while reducing the TP to AA ratio (TP/AA). However, it decreased total catechins (TC). Chlorophyll, caffeine (CAF) and theanine accumulated to a greater degree at nitrogen application rates of 150, 300, and 450 kg/ha, respectively. Moreover, TP, CAF, TC, WE, EGC, and AA significantly influenced taste (VIP＞1). Eight key volatile compounds (VIP＞1, OAV≥1) crucial for the overall aroma of fresh tea leaves were identified, with linalool and cis-linalool oxide (furanoid) being the most significant. Moreover, applying 300 kg/ha nitrogen upregulated the dihydroflavonol reductase (DFR)gene, which may explain the decrease in catechin content observed in that treatment group.