Oxidation stress and antioxidant levels in tangerine pericarp

Tangerine peel is a common traditional Chinese medicine and an herb for Chinese food preparation. In order to study the influence of oxidative stress, ozonated water, gaseous ozone and UV radiation were applied to potted tangerine plants and the antioxidant levels in fruit pericarp were compared. After being watered daily with 500 mL ozonated water (0.84 mg/L dissolved ozone) for two weeks; a 19.5% increase in pericarp antioxidant level was detected. After plant samples were exposed to 6 ppm ozone, 2.88 KJ/m2 UV or a combination of both for 30, 60 and 120 min daily for the same period; decreases in antioxidant level were found and were generally in proportion to the time course of treatment. The results indicated that the oxidants depleted the antioxidant in the pericarp of mature tangerine. Ozonated water application to soil, however, as a systemic response increased the antioxidant level in the pericarp.