Study on hot water treatments for inducing cold tolerance of postharvest Cucurbita pepo L.during low temperature stress

The effects of hot water treatment on chilling tolerance of Cucurbita pepo L.were investigated.Cucurbita pepo L.were used as the object of this research.The fruits were fully immersed in hot water of 45 ℃ and 35 ℃ for 5 min and 10 min, fruits without hot water treatment as the control, and then stored at 4 ℃ for 0, 3, 6, 9, 12, 15 d.The chilling injury index, soluble sugar content, H₂O₂ content, activities of catalase activity (CAT) , superoxide dismutase (SOD) and peroxidase (POD) , malondialdehyde (MDA) content and electric conductivity were measured as related indicaters during the storage period. The results showed that, compared with the control, soluble sugar content was increased (p < 0.05) , the content of H₂O₂ in heattreated fruits was higher than the control fruits within the first 3 d, and the treatment reduced the H₂O₂ accumulation at middle and later period of storage (from the 6thto the 15^th) (p < 0.05) .The activities of CAT and SOD were increased at pre-storage (from the 0thto the 6th) , and decreased at middle and later period of storage (from the 9thto the 15^th) .Especially POD activity was increased significantly at the late stage of storage (from the 6thto the 15^th) (p < 0.01) .The increase of MDA content and conductivity were inhabited, and chilling injury index was controled (from the 6thto the 15^th) (p < 0.05) .These results suggested that the chilling tolerance of zucchini fruit can be induced by hot water treatment under low temperature stress, and chilling injury was reduced effectively, and in this experiment, 35 ℃, 10 min was the better hot water treatment.