Study On 2,4-D Residue And Preservation In Citrus Fruits

In this thesis, study on 2,4-D residue in citrus( fruit coat, flesh), the activity of 2,4-dichlorophenol hydroxylase and the attribute change of citrus treated with 2,4-D were carried out. The purpose of the study was to realize residue and degradation of 2,4-D in citrus, to know whether the citrus was safe, and to improve fruits attribute with 2,4-D.Ministry of Agriculture China made the law that 2,4-D residue tolerance was 2mg/kg in citrus. The results showed that the content of 2,4-D was ranged from 28.5 ng/g to 8.1 ng/g in citrus from market, which showed that the citrus from market was safe.Mandarin fruits treated with 200mg/L, 100mg/L and 50mg/L 2,4-D, were detected residue of 2,4-D in citrus flesh after storage for 12 hours, 24 hours and 48 hours respectively. The results showed that residue of 2,4-D in flesh was from 50ng/g to 400ng/g, which less than residue tolerance. So the flesh was safe. The rate of bad-fruit of Mandarin fruits treated with 200mg/L 2,4-D was lowest. It showed that the best content of 2,4-D was 200mg/L.Mandarin fruit treated with 2,4-D, the content of it was 2.5% and 6.3% more than residue tolerance in fruits coat after storage for 12 hours and 20 days. Storage less than 20 days, the content of 2,4-D was more than residue tolerance in fruits coat of orange cv. luogan; it was less than residue tolerance when the orange stored more than 20 days. A month later, it was 13.9% less than residue tolerance. Compared with the control, the content of 2,4-D was less than residue tolerance in Mandarin flesh treated with 2,4-D; at the 5th day, the content of 2,4-D in flesh was 31.5% more than residue tolerance in orange cv. luogan treated with 2,4-D. It showed that thesafety of citrus flesh was high.The content of 2,4-D in fruit coat was higher than that in flesh, the content of 2,4-D in Mandarin fruits was less than that in orange cv. luogan.The content of 2,4-D in Mandarin fruits or orange cv. luogan decreased slowly (30 days). After 60 days of storage, the content of 2,4-D in Mandarin fruits or orange cv. luogan was lower which compared with the content after 30 days of storage. 2,4-D residue in fruit coat reached its maximum at the 20th day, 2,4-D residue in flesh reached its maximum at the 5th day. It showed that citrus absorbed 2,4-D gradually, in the same time, 2,4-D degraded gradually in the fruit.2,4-dichlorophenol hydroxylase is an enzyme during 2,4-D degradation. For 1-30 days of storage the activity of it was from 13.0x1000 U min-1.mg"1 Protein to 69.0x1000 U min-1mg"1 Protein.Treated with Sportak and 2,4-D could decrease the rate of bad-fruit in citrus, could inhibit decrease during storage.