Metabolomics Reveals the Mechanism of Browning Inhibition by Transient Light Quality in Tea Plant Tissue Culture

The absence of a high-efficiency and stable genetic transformation system has been a critical bottleneck, impeding both functional gene characterization and precision breeding efforts in <i>Camellia sinensis</i> (tea), and browning is the first problem encountered in tissue culture of tea. In this paper, to identify optimal spectral conditions for minimizing browning in tissue culture, we subjected three tea plant cultivars to distinct light quality treatments and conducted comprehensive metabolomic profiling of their phytochemical contents. This study demonstrates that wavelength-specific light treatments can induce reversible modifications in the physicochemical characteristics of tea leaves, effectively reducing the accumulation of flavonoid compounds, including polyphenols, in plant tissues. Notably, tissues subjected to optimized wavelength conditions exhibit superior performance as explant sources for in vitro culture systems, demonstrating significantly lower browning rates. Comparative analysis of 460 nm, 660 nm, and 730 nm irradiation treatments revealed consistent suppression of polyphenol biosynthesis across all examined cultivars. However, the wavelength eliciting maximal reduction showed significant cultivar-dependent variation, indicating genotype-specific photoresponsive regulation of secondary metabolism.