Effect of Putresine and Methyl Jasmonate on Antioxidant Responses in Peel and Pulp of Orange (Citrus sinensis L. var. Valencia) Fruit

This experiment was carried out to determine the effects of putrescine and methyl jasmonate on lipid peroxidation and altering the peroxide hydrogen of peel and pulp of Valencia orange fruit. Orange fruits were treated with 0 (control), 2.5 and 5 mM putrescine, and 0 (control), 10 and 20 μM methyl jasmonate, then stored at 5±1 °C, 85-90% relative humidity for four months. Oranges treated with 5 mM putrescine and 10 μM methyl jasmonate had significantly lower lipid peroxidation and peroxide hydrogen of peel and pulp and lower chilling injury percentage than the non-treated fruits. Polyphenol oxidase (PPO) activity was considerably increased in the treated and non-treated fruits but, the treated fruits exhibited significantly lower activity of PPO. Peroxidase (POD) activity increased at first and then decreased. However, the treated fruits exhibited significantly higher activity of POD than the control fruits during the storage period. In conclusion, fruits treated with 5 mM putrescine combined with 10 μM methyl jasmonate showed the best effect.