Study On Effect Of Nitric Oxide And Gibberellicacid On Cottony Softening Of Postharvest Wax-apple

In this paper,‘Black Pearl’wax-apple fruits（Syzygium samarangense Merr.et Perry）were used as materials.The storage condition was 25±0.5°C,RH 85±2%.The effects of postharvest treatments with different concentrations of nitric oxide（NO）(0²0μL·L^-1)and gibberellic aid（GA₃）(0²0mg·L^-1)on physiological changes,sugar metabolism,energy metabolism and cell wall metabolism were investigated.The mechanism of NO and GA₃ treatments on cottony softening process of postharvest wax-apple fruits was discussed.Furthermore,the effect of10μL·L^-1NO in combination with 20mg·L^-1 GA₃ on delaying cottony softening process of postharvest wax-apple was also assessed.All above were expected to provide theoretical bases for the development and application of wax-apple preservation technique.The results were as follows:During postharvest storage,the cottony softening process of wax-apple intensified.The cottony softening index was negatively correlated with sugar content,ATP content,energy charge and proto pectin content in cells.And the cottony softening index was significantly correlated with weight loss and soluble pectin in cells.The intensification of cottony softening process was related to material loss,energy deficiency and cell wall disintegration.The treatment with 10μL·L^-1NO or 20mg·L^-1GA₃ could significantly inhibit moisture loss,the increase of weight loss and the decrease of total sugar content and total soluble sugar.The combined treatment could delay the peak of total sugar content and total soluble sugar.High activity of AI,NI and SS in disintegration could promote the disintegration of sugar,accelerate senescence.The effect of combined treatment on inhibiting the disintegration of sugar was much better than 10μL·L^-1NO and 20mg·L^-1GA₃ treatment.The ATP content in cells decreased during postharvest storage,and wax-apple fruits were in energy deficiency status.The treatment with 10μL·L^-1NO or 20mg·L^-1GA₃ could maintain higher ATP content and energy charge,delay the process of energy deficiency.Furthermore,the effect of combined treatment was much better.Besides,combined treatment could significantly inhibit the decrease of CCO activity,maintain higher activity of SDH and Ca²⁺-ATPase,slow down the increase of cell membrane permeability and delay senescence.The activity ofβ-Gal was negatively correlated with proto pectin content,and significantly correlated with cottony softening index.It means thatβ-Gal was directly involved in the disintegration of cell wall,and might be involved in the cottony softening process.The treatment with 10μL·L^-1NO or 20mg·L^-1GA₃ and combined treatment could significantly inhibit the decrease of proto pectin content and the increase ofβ-Gal activity,delay the activity peak of PG and Cx,and slow down the disintegration of cell wall.The effect of combined treatment was the best.