With the increase of zinc treatment time and zinc concentration, the O₂^- content of each group is also increasing. The results showed that the longer zinc treatment time, the higher concentration, the greater stimulation to Dendrobium nobile , and the more O₂^- produced. At 14 days of treatment, when the zinc concentration was more than 800μmol/L, the content of O₂^-increased significantly compared with the low concentration zinc treatment group. But there was no significant difference between T5 (800 μmol/L) group and T6 (1000 μmol/L) group. When the zinc concentration is 2000μmol/L, it has a significant increase compared with 1000μmol/L. The results showed that zinc concentration of 2000 μmol/L and longtime treatment could make Dendrobium nobile produce more O₂^-.

It can be seen from Figure3a, on the 7th and 14th day, when the zinc concentration was 2000 μmol / L, the soluble sugar content reached the maximum. However, on the 21st day, when the zinc concentration was 400 μmol/L, the soluble sugar content reached the maximum. The results showed that zinc had a greater effect on the production of soluble sugar with the increase of zinc treatment time, and it could stimulate the production of more soluble sugar even at a lower concentration.

As shown as Figure3b, within 14 days after zinc treatment, the soluble protein of each group changed in varying degrees, but there was no regularity. After 21 days of zinc treatment, there was a regular trend of change, first increased and then decreased. When the zinc concentration was 800 μmol/L, the soluble protein content was the most, and there was a significant difference compared with the control group. This result shows that zinc treatment for a long time could stimulate the secretion of soluble protein.