Effects of Se, Zn and their interaction on polyphenol oxidase activity of tea leaves in summer season

Different levels of Na2SeO3 (0, 100, 200 and 400 μg/mL) and (CH3COO)2Zn·2H2O (0, 0.4%, 0.8% and 1.2%) was applied by foliar spraying to determine the effects of Se, Zn and the their interaction on polyphenol oxidase (PPO) activity of tea leaves in summer season. The result showed that: (1) The PPO activity of tea leaves was higher when spraying apply Se at 100–200 μg/mL and Zn was 0.4%–0.8% compared to other treatments. Applying high-concentration of Se (400 μg/Ml) or Zn (1.2%) alone did not significantly improve PPO activity. Higher PPO activity was observed at 16 days after Se or Zn spraying application. (2)Combined applying middle-concentration of Se (100–200 μg/mL) and Zn (0.4%–0.8%) increased PPO activity, but combine applying high-concentration of Se and Zn had no significant effects on PPO activity. The PPO activity after 16 days of spraying became stable. When applying high concentration of Zn combined with different concentration of Se, the temporal effect on PPO activity was not significant，but when low concentration of Zn was combined with different concentrations of Se, the temporal effect on PPO activity was significant.