| 摘要： 本研究探討乙烯作用抑制劑1-MCP (1-methylcyclopropene)處理對省所產之’台農二號’番木瓜果實後熟之影響。試驗用番木瓜果實採收之成熟度依其果皮轉色程度，可分為綠熟-M1，20%果皮轉黃-M2，20-40%果皮轉黃-M3，並以果皮轉色hue angle值達80o為完熟標準。結果顯示以1 ppm 1-MCP處理採收成熟度越低之果實，延緩果皮轉色之效果越大；M1，M2，M3果實分別延後12，3，1天到達完熟。番木瓜為更年性果實，未處理1-MCP之果實的乙烯生成速率皆於第2天開始增加，以1 ppm 1-MCP處理成熟度越高之果實，延後乙烯生成開始上升的天數越短，M1，M2，M3果實分別延後乙烯生成上升達12，6，4天。成熟度M1與M2之番木瓜果實處理1-MCP最低有效濃度為0.3 ppm，分別以1與3 ppm處理效果達到飽和。延緩果實軟化速率之效果則隨著1-MCP處理濃度增加而增加，但3 ppm 1-MCP處理M1果實其完熟後果肉硬度偏高。以0.3-3 ppm 1-MCP處理之果實，隨著處理濃度增加，激發出現乙烯自動催化生成所需之果腔內生乙烯濃度隨之提高，乙烯濃度由0.1 ppm提高至0.4 ppm。 經1-MCP處理之番木瓜其果肉圓片之受傷乙烯生成比對照組慢到達高峰，且其最大乙烯生成速率為對照組之兩倍，此一現象表示1-MCP處理可能抑制番木瓜果實受傷乙烯生成之回饋調控機制。正常之番木瓜果實在果皮開始轉黃後，聚半乳糖醛酸酶活性與內部乙烯濃度會迅速上升，果肉亦迅速軟化。番木瓜以1 ppm以上1-MCP處理會使果肉無法正常軟化，在到達相同轉色階段時，其內部乙烯濃度與聚半乳糖醛酸酶活性分別受到抑制，此現象可能與果實無法正常軟化有關。This study investigated the effect of the ethylene action inhibitor — 1-methylcyclopropene(1-MCP) on the ripening of ‘Tainon No.2’ papaya fruit of Taiwan. According to the degree of coloration of fruit skin, as a index of maturity, the papaya fruit used in this study was separated into the following stages: Mature green (M1 stage), 20% turning yellow (M2 stage) and 20-40% turning yellow (M3 stage). The papaya fruit was considered fully ripe when the hue angle value of fruit skin, as measured by a colormeter, reached 80. Treatment of papaya fruit with 1 ppm 1-MCP delayed the coloration of fruit skin. The effect was more pronounced in less matured fruit. For M1, M2, and M3 fruits, the days to reach fully ripe were delay for 12, 3 and 1 day respectively. Papaya is a climacteric fruit. The ethylene production rate of untreated fruit started to increase on the 2nd day and 1 ppm 1-MCP treatment delayed this increase. For M1, M2 and M3 fruits, the days to increase in ethylene production were delayed for 12, 6 and 4 days respectively. The minimum effective 1-MCP concentration for M1 and M2 papaya was 0.3 ppm, and saturated at 1 ppm and 3 ppm respectively. Fruit softening rate was also reduced by 1-MCP treatment, the effect was in parallel with the concentration of 1-MCP. However, 3 ppm 1-MCP treatment resulted in fruit with ripe color but hard flesh. The internal ethylene concentration to initiate autocatalytic ethylene production in the fruit cavity was 0.1 ppm, and this concentration was raised to 0.4 ppm in fruits treated with 3 ppm 1-MCP. The peak of wound ethylene production of papaya fruit discs was delayed by 1-MCP treatment, and the maximum value of wound ethylene production was twice as much as the control. This result suggested that 1-MCP treatment inhibited the feed-back regulation of the wound induced ethylene production in papaya fruit. During normal ripening of papaya fruits, an increase in the polygalacturonase activity and internal ethylene concentration was observed when the fruit turned yellow and the fruit’s flesh softened rapidly. However, 1-MCP treatment at concentrations greater than 1 ppm resulted in papaya fruits with firm flesh after fruit reached ripe color. In this study, it was observed that in 1-MCP treated fruits, the increase in internal ethylene concentration and polygalacturonase activity was inhibited as the fruit turned yellow. These results may bear some relationship to the abnormal flesh firming of 1-MCP treated papaya fruit. |
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