Effect of Calcium Nitrate on Muskmelon (Cucumis melon L.) Softness and Relative Physiological Parameters

The effect of calcium nitrate on relative physiological parameters of muskmelon softness was studied.The regulation measures of prolong fruit shelf-life were explored to provide theoretical basis for calcium use to prolong the optimal edible phase and shelf-life,and to learn the mechanism of calcium delaying the process of ripening and senescence.Muskmelon discs taken at ripening stage were treated with different concentrations of calcium nitrate(1,3 and 5 mmoloL-1) and various time(4,8,12,16,20 and 24h) in order to investigate the fruit softness and the relative physiological parameters.The results showed that calcium nitrate treatment slowed apparently down the softness,elevated the flesh firmness,retarded the ethylene production and respiratory rate,and suppressed PG,PE and CMC-Na activities.However,different concentrations and time had various influences in the process of fruit softness.Compared with the control(6.09-6.81 kg·cm-2),the firmness of calcium treatments was 0.22-1.24 kg·cm-2 higher.Moreover,compared with 1 and 3 mmol·L-1,5 mmol·L-1 treatment could more significantly inhibited the flesh respiratory,ethylene production and PG,PE and CMC-Na activities,the inhibition of flesh softness was apparently enhanced.Similiarly,the former was higher with 0.02-0.34 kg·cm-2 higher than the latter.Calcium nitrate treatment for 4h enhanced flesh firmness,reduced ethylene production and respiratory rate,and suppressed PG,PE,CMC-Na activities.After the discs were treated by calcium nitrate for 12h,the above relative softness parameters were inhibited in the lowest level among different treating time.Under 24h treatments,the ethylene production,PE and CMC-Na activities increased slightly,but there were significant differences of the above parameters with control.5 mmol·L-1 calcium nitrate and treating for 12h could delayed the process of the muskmelon softness.