Study On Effect Of Nitric Oxide Treatment On Cottony Softening Of Postharvest Wax Apple And Their Acting Mechanisms

In this paper, the effects of postharvest treatment with NO on respiration rate, the rate ofethylene production, fruit quality, cottony softening, and active oxygen metabolism relatedenzymes of ‘Black Pearl’ wax apple fruit during storage at temperature20±2℃and humidity85±2%were investigated. The relationship of nitric oxide and wax apple senescence, thephysiological and biochemical mechanism of cottony softening of wax apple were also discussed.All above were expected to provide theoretical bases for NO applying to fruit storage. Theresults show that:During storage period, the firmness of wax apple decreased, the weightlessness rate keptincreasing, the total sugar and titratable acid content didn’t chang significantly, and themembrance permeability showed a rising trend. Respiration rate of wax apple kept rising,ethylene release ascended firstly and declined finally.60and200μL·L-1NO enhancedrespiration rate and weightlessness rate, showed the toxicity of NO.10and20μL·L-1NO couldmarkedly inhibit the respiratory rate and the weightlessness rate, delay the decline of fleshfirmness and the rise of relative membrane permeatility. However, there were not much effectson titratable acid content of wax apple fruits by the treatment of10and20μL·L-1NO.20μl·L-1NO delayed the appearing time and degraded the height of ethylene peak in wax apple fruits.The protopectin and cellulose metabolism had an important relationship to cottonysoftening of wax apple fruits.10and20μL·L-1NO delayed the onset of polygalacturoneses (PG),β-galactosidase (β-Gal) and cellulase (Cx) activity peaks, inhibited the increase of flesh firmness,protopectin and cellulose content of wax apple fruits.Pectinmethylesterase (PME) could play a key role in cottony softening of wax apple fruits,but PME activity was not facilitated by NO. PG and β-Gal affected the cottony softening of waxapple fruits, but it didn’t play a key role. Cx could play more roles at early cottony softening ofwax apple fruits. NO achieved regulation of cottony softening of wax apple fruits by affectingthe activity of PG, β-Gal and Cx.Throughout the storage period, peroxidase (POD) and catalase (CAT) activity of wax applefruits, presented the first decline after rising trend. The activity of superoxide dismutase (SOD)showed a decreasing trend.10and20μL·L-1NO reatment maked the POD, CAT and SODactivities of wax apple fruits increase during storage period, delayed the arrival of superoxideanion (O2-·) production rate rapid increase, inhibited the accumulation of hydrogen peroxide(H2O2) and the rise of malondialdehyde (MDA) content.10and20μL·L-1NO miantain wax apple with higher quality during storage. But NO can’textend storage life of wax apple fruits, mainly dealing with there were not much effects onmildew rate.10and20μL·L-1NO achieved regulation of cottony softening of wax apple fruits byaffecting the activity of PG, β-Gal and Cx. However, PME as a key role of cottony softening ofwax apple fruits is not sensitive to NO.