Metabolic Regulation Profiling of Carbon and Nitrogen in Tea Plants [Camellia sinensis (L.) O. Kuntze] in Response to Shading

Manipulating
light transmission by shading is the most effective
method of improving the nutritional value and sensory qualities of
tea. In this study, the metabolic profiling of two tea cultivars (“Yulv”
and “Maotouzhong”) in response to different shading
periods during the summer season was performed using ultraperformance
liquid chromatography-tandem mass spectrometry (UPLC-MS) and gas chromatography-mass
spectrometry (GC-MS). The metabolic pathway analyses showed that the
glycolytic pathway and the tricarboxylic acid cycle (TCA cycle) in
the leaves and shoots of “Maotouzhong” were significantly
inhibited by long-term shading. The nitrogen metabolism in the leaves
of the two cultivars was promoted by short-term shading, while it
was inhibited by long-term shading. However, the nitrogen metabolism
in the shoots of the two cultivars was always inhibited by shading,
whether for short or long-term periods. In addition, the intensity
of the flavonoid metabolism in both tea cultivars could be reduced
by shading. These results revealed that shading could regulate the
carbon and nitrogen metabolism and short-term shading could improve
the tea quality to some extent.