The leaves and tubers were treated with UV-A, UV-B and UV-C for 1 h, 1L/23D h, 3 h and 3L/21D h (D represents darkness treatment). High-performance liquid chromatography (HPLC) analysis showed that the content of many flavonoids decreased significantly during UV-A treatment, increased after UV-B and UV-C irradiation and accumulated again after darkness treatment.
In the root tubers of the UV-A group, naringin content in the 3L/21D h group (0.069 μg/g) was 16.30 times higher than that of 3 h group (0.0042 μg/g). The rutin content was elevated after UV irradiation but was not detected in the CK group. The test results of the enzyme-linked kit indicated that the activities of many enzymes were higher in the UV-A and UV-B irradiation groups than those in the CK group, but the results were reversed in the UV-C treatment. After darkness treatment, the activities of most enzymes were higher than those with UV irradiation alone; F3’5’H activity in the 3L/21D h group (97.25 U/L) was 1.24 times higher than that in the 3 h group (78.12 U/L) in the UV-A-treated group.
The study results suggest that appropriate UV-B and UV-C irradiation, as well as darkness supplementation, had a promotive effect on flavonoids in the leaves and root tubers of