Physiological Regulation Mechanism of Antioxidant Enzymes in Fruits and Leaves During Growth and Development of Navel Orange in Gannan Region

The navel orange of 10-year-old mature was used as the experimental material to detect the adaptability to high-temperature environment of 5 antioxidant enzymes (SOD, POD, CAT, APX and GR) in fruits and leaves at different growth and development stages. The results showed that the activity of the 5 antioxidant enzymes varied significantly, and there was a coordination mechanism among different antioxidant enzymes. SOD activity was the largest, followed by CAT and POD. The activity of the antioxidant enzymes in fruits was lower than that in leaves. The activity of SOD in fruits showed a 'decreased-increased' trend, contrary to the 'increased-decreased' trends of the activity of POD, CAT, APX and GR, among which the peaks of POD, CAT, APX activity and the valley of SOD activity all appeared in September. In leaves, there were peaks of activity of all antioxidant enzymes, with the peaks of SOD, CAT, APX and GR activity appearing in September. Therefore, the resistance to high temperature stress in fruits of navel orange was greater than that in leaves, and the resistance to high temperature stress in fruits from July to September was greater than that from October to November. SOD, CAT and POD constitute the key enzyme system against high temperature stress in navel orange.