Abstract:

A study on effects of salicylic acid (SA) treatment on enzymes of ascorbate-glutathione cycle in young loquat (Eriobotrya japonica cv.'Zaozhong No.6’) fruits was conducted to explore the mechanism of SA in promoting the chill-resistance of young loquat fruits to low temperature. Results indicated that 40 and 70 mg·L^-1 SA treatments increased the reduced glutathione (GSH) contents, and decreased the oxidized glutathione (GSSG) content. Therefore, the treatment resulted in elevating the ratio of GSH/GSSG in young loquat fruits under low temperature stress. Meanwhile, SA treatment also promoted the activities of GSH-dependent glutathione reductase (GR), glutathione-S-transferases (GST), and glutathione peroxidase (GPX) in young loquat fruits, which could activate its cell detoxification function by degrading peroxides caused by low temperature stress. Furthermore, SA treatment increased ascorbate peroxidase (APX), dehydroascorbate reductase(DHAR), monodehydroascorbate reductase (MDAR) activities and ascorbate (AsA) contents,and decreased the contents of dehydroascorbate (DHA), super hydrogen (H₂O₂), malondialdehyde (MDA) contents and relative electric conductivity (REC), which led to an increase of AsA/DHA ratio, and ultimately resulted in alleviating the oxidative damage caused by low temperature stress. It is concluded that SA could significantly improve oxidation resistance and chill-resistance of young loquat fruits. SA concentration at 70 mg·L^-1 was preferable for young loquat fruits.

Key words: young loquat fruit, salicylic acid, low temperature stress, ascorbate-glutathione cycle