A comparison of reactive oxygen species production and scavenging in muskmelon fruits during storage under three low temperatures

Muskmelon fruit( cv.Jinhongbao) was used as material to study the effect of three low storage temperatures( 3,7,9℃) on the production rate of superoxide anion( O-2·),accumulation of hydrogen peroxide( H2O2) and the activities of superoxide dismutase( SOD),catalase( CAT),glutathione reductase( GR) and ascorbate peroxidase( APX) during storage.The results showed that the production rate of O-2·was increased at the early stage( 4d) of storage at 7℃ and 9℃,but significantly enhanced at the late stage( 12d) of storage at 3℃.The accumulation of H2O2 was significantly increased at the early stage of storage at 3℃.However,it was gradually increased in the mid( 8d) and late( 12d) stage of storage at 7℃ and 9℃.At the early stage of storage,the activities of SOD,GR and APX in muskmelons stored at 7℃ were higher than that stored at 3℃ and 9℃,and the activity of CAT in fruit was the lowest at 3℃.These results indicated that a large accumulation of H2O2 and the lower activities of the antioxidant enzymes in fruit stored at 3℃ may lead to chilling injury of muskmelons. The fruit stored at 7℃keep the balance of reactive oxygen species production and scavenging,indicating 7℃ is suitable temperature for storage of muskmelons.