## 3 Results
### Tea Nutritional Quality under Different Concentrations of ZnO-NPs  
The application of ZnO-NPs caused significant effects on soluble sugar, soluble protein, and tea polyphenol contents. As a fast-acting nutrient, they have more beneficial to the vegetative growth of tea trees in a short time.  
As can be seen in Figure 2A, there were significant differences in soluble sugar content on 1 April. Soluble sugar content under the 10 mg\(\cdot\)L\({}^{-1}\) ZnO-NPs treatment (47.89 mg\(\cdot\)g\({}^{-1}\)) was significantly higher than that in all other ZnO-NPs treatments, but had no significant difference with that of CK. Under 50, 150, 200 mg\(\cdot\)L\({}^{-1}\), the soluble sugar content was close with no significant difference on 1 April. The difference of soluble sugar content in the fresh tea leaves increased with the increasing of the ZnO-NPs concentrations. The 50 mg\(\cdot\)L\({}^{-1}\) treatment caused the lowest content in two sampling periods. Samples which were picked on 8 April had the similar trend, but the contents at 0, 50, and 100 mg\(\cdot\)L\({}^{-1}\) were all lower than those of the samples which were picked on 1 April.  
Figure 1: Effect of zinc oxide nanoparticles on chlorophyll a (**A**), chlorophyll b (**B**) and total chlorophyll (**C**) content of tea leaves. Different lowercase letters indicated significant differences at the 0.05 level.  
Figure 2: Effect of zinc oxide nanoparticles on soluble sugar (**A**), soluble protein (**B**) and polyphenol (**C**) content of tea leaves. Different lowercase letters indicated significant differences at the 0.05 level.  
Significant differences were found in soluble protein content in the fresh tea leaves which were picked on 1 April. The soluble protein content in the fresh tea leaves at 50 mg\(\cdot\)L\({}^{-1}\) and in the CK was higher in the first sampling period (4.66 mg\(\cdot\)g\({}^{-1}\) and 4.67 mg\(\cdot\)g\({}^{-1}\), respectively), which was significantly higher than that under the 10 mg\(\cdot\)L\({}^{-1}\) treatment. The soluble protein content in the fresh tea leaves which were collected on 8 April did not have significant differences with that of the other treatments. In this period, the soluble protein content in the CK was 3.68 mg\(\cdot\)g\({}^{-1}\), and the contents under the 50 mg\(\cdot\)L\({}^{-1}\) and 100 mg\(\cdot\)L\({}^{-1}\) treatments were much higher than those in the CK.  
Figure 2C shows the effects of different ZnO-NPs treatments on the content of tea polyphenols in the tea leaves. In general, the ZnO-NPs use brought about a limited effect on the content of tea polyphenols, and there was no significant difference among the treatments in both periods. Among the tea samples picked in the two periods, the CK tea samples had the highest content of tea polyphenols, which was 192.13 mg\(\cdot\)g\({}^{-1}\) and 184.81 mg\(\cdot\)g\({}^{-1}\), respectively. Then the content of tea polyphenols decreased generally with the increasing of ZnO-NPs concentrations. The content of tea polyphenols in the tea leaves treated with 100 mg\(\cdot\)L\({}^{-1}\) was lower in the two periods, while the content of tea polyphenols in leaves treated with 10 mg\(\cdot\)L\({}^{-1}\) and in the CK was the opposite.