Incidence of water-soaking and phospholipid catabolism in ripe watermelon (Citrullus lanatus) fruit: induction by ethylene and prophylactic effects of 1-methylcyclopropene
Linchun Mao, Yasar Karakurt and Donald J. Huber
Postharvest Biology and Technology Volume 33, Issue 1 , July 2004, Pages 1-9
2004
บทคัดย่อ
Watermelon (Citrullus lanatus Thunb. Matsum and Nakai) fruits were held in 50 μl l−1 ethylene at 20 °C following an 18-h exposure to 5 μl l−1 1-methylcyclopropene (1-MCP) to investigate the involvement of ethylene perception in the regulation of placental tissue water-soaking through phospholipase-mediated phospholipid (PL) degradation. Water-soaking was accompanied by increase in phospholipases C (PLC, EC 3.1.4.3) and D (PLD, EC 3.1.4.4), and lipoxygenase (LOX, EC 1.13.11.12) activities, decreases in phosphatidylcholine (PC) and phosphatidylinositol (PI), and increases in phosphatidic acid (PA). These changes were evident within 2 days of ethylene exposure, coincident with accelerated softening, increased electrolyte leakage and extractable juice, and appearance of water-soaking. Air-stored fruits did not exhibit water-soaking, and the activities of lipid-degrading enzymes and PL levels remained constant throughout the 8-day storage period. Treatment of fruit with 5 μl l−1 1-MCP prior to ethylene exposure reduced ethylene-induced increases in the activities of lipid-degrading enzymes, and PL degradation, and completely prevented water-soaking and the attendant increases in electrolyte leakage and extractable juice. The results demonstrated that water-soaking in watermelon fruit requires competent ethylene responsiveness and is associated with ethylene-inducible PL degradation. This represents the first report wherein 1-MCP imparts to a fully ripe fruit complete protection against deleterious effects of exogenous ethylene. Watermelon fruit maintained under simulated commercial storage conditions (up to 3 weeks at 13 °C ) without exposure to exogenously provided ethylene also benefited significantly from prior exposure to 1-MCP.