Effects of magnesium on quality and aroma composition of Wuyi Rougui tea (Camellia sinensis L.) leaves

In hydroponic conditions, we investigated the effects of applied magnesium (Mg) on quality of leaf and aroma of seedlings of Wuyi Rougui tea (Camellia sinensis L.). Different concentrations of Mg [0.4 mM (Mg1), 0.6 mM (Mg2) and 0.8 mM (Mg3)] were added into the hydroponic solution. Control treatment did not contain Mg (Mg0). With the increasing availability of Mg, the polyphenols content were significantly increased. The lowest free amino acid content (2.44 %) was observed in the Mg1 treatment. The Mg treatments significantly influenced the caffeine level, except in Mg2 and Mg3. Maximum total flavone content (9.30 mg/g) was in Mg2 treatment followed by Mg1, Mg3 and Mg0, respectively. The highest content of soluble sugars (9.30 %) was observed in the Mg2 treatment followed by Mg1, Mg3 and Mg0. Principal component analyses of quality indicators showed that PCoA1 and PCoA2 differed in samples treated with various Mg concentrations and the total variability was 97.73 %. Caffeine and catechin contents showed a negative correlation to increasing Mg concentrations. The last ones displayed a positive correlation (r = 0.945) with (E,E)-2,4-heptadienal levels and were inversely correlated (r = - 0.967) with decanal content.