Strawberry (Fragaria ananassa Duch.) seedlings were pretreated with hexanoic acid 2-(diethylamino)ethyl ester (DA-6) in concentrations of 0, 10, 20 and 40 mg dm -3 and then subjected to chilling and rewarming. The effects of applied DA-6 on the generation of reactive oxygen species (O 2 -, H 2 O 2 ), lipid peroxidation, proline accumulation and photosynthesis were evaluated. Pretreatment with DA-6 alleviated the inhibition of superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) activities caused by chilling stress thus reducing O 2 -and H 2 O 2 production and lipid peroxidation in pretreated plants. DA-6 pretreatment also accelerated accumulation of proline and reduce the decrease in proline content after rewarming. DA-6 pretreatment increases maximum quantum yield of photosystem 2 (F v /F m ), actual photochemical efficiency of photosystem 2 (Φ PS2 ), photochemical quenching coefficient (qP) and net photosynthetic rate (P N ) and decreases non-photochemical quenching coefficient (qNP) of the seedlings under chilling stress. DA-6 pretreatment also increased the recovery rate of photosynthesis after rewarming.Additional key words: ascorbate peroxidase, catalase, chlorophyll fluorescence, Fragaria ananassa, net photosynthetic rate, superoxide dismutase.
To determine the effect of transportation vibration on the nutritional quality and antioxidant activity of sweet cherry fruits in the process of cold chain transportation. Two kinds of sweet cherry "Summit" and "Nanyang" with different storage and transportation resistance were used as experimental materials. The results showed that the content of soluble solids, titratable acids and vitamin C in sweet cherry fruits were significantly reduced, while the content of superoxide anion radical, malondialdehyde and the antioxidant enzyme activities of CAT, APX, POD and PPO increased significantly, At the same time, the content of total phenols and flavonoids were increased under transport vibration stress, but the ability of DPPH and ABTS + free radical scavenging of sweet cherry were reduced significantly. In particular, transportation vibration stress had a greater impact on the nutritional quality and antioxidant activity of "Nanyang", a sweet cherry with poor storage resistance. The results of this study indicated that transportation vibration has a great impact on the nutritional quality of sweet cherry, and that there is a strong correlation between antioxidant activity and nutritional quality. This study confirmed that transportation vibration during cold chain transportation can significantly reduce the nutritional quality and antioxidant activity of sweet cherry.
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