Abstract:

Three-year-old ‘Zaozhong No. 6’ loquat ( Eriobotrya japonica, Fujian Province) seedlings were foliar-sprayed with 0.2, 0.5 and 1.0 mmol·L^-1 of sodium nitroprusside (SNP, as NO donor). They were then subjected to low temperature (-3 ℃) stress in a phytotron. The effects of SNP on some physiological and biochemical indexes of young loquat fruits were studied. The indexes include malondialdehyde (MDA), proline (Pro), hydrogen peroxide (H₂O₂), ascorbic acid (AsA), dehydroascorbic acid (DHA), glutathione (GSH), oxidized glutathione (GSSG) content and the activities of catalase (CAT, EC 1.11.1.6), peroxidase (POD, EC 1.11.1.7), superoxide dismutase (SOD, EC 1.15.1.1) and ascorbate peroxidase (APX, EC 1.11.1.11). This study was to explore the regulation mechanism of exogenous nitric oxide (NO) on cold resistance of young loquat fruits under low temperature stress. The results showed that SNP treatment decreased levels of MDA and H₂O₂ in young loquat fruits after low temperature stress. Moreover, activities of CAT, POD, SOD and APX and Pro concentration of Pro were enhanced to some extent. Ratios of AsA/DHA and GSH/GSSG were increased, respectively. It is concluded that the exogenous NO could enhance the protective enzyme activity and reduce membrane lipid peroxidation, and increase the osmoregulation substance content of young loquat fruits after low temperature stress, resulting in an increase of the cold temperature resistance of young loquat fruits. In this study, we found that the desirable concentration of SNP was 0.5 mmol·L^{- 1}.

Key words: nitric oxide (NO), young loquat fruit, low temperature stress, anti-oxidation capacity