乙烯诱导西瓜果实的水渍化败坏

为了研究乙烯在西瓜(Citrullus lanatusThunb.Mansfeld)果实水渍化败坏过程中的作用,先将果实在5μL/L 1-甲基环丙烯(1-MCP)气体中处理18 h,然后在50 μL/L乙烯和20℃温度下贮藏.西瓜果实对乙烯处理的最初反应表现为胎座组织的电导率和游离汁液增加,同时出现组织软化和水渍化.水渍化的症状最初在靠近花萼端的内果皮中发生,在乙烯处理的第2天开始出现,ACC合成酶(ACS)和ACC氧化酶(ACO)的活性明显提高.1-MCP单独处理不产生任何明显的作用,但是会完全抑制外源乙烯诱导的水渍化败坏.没有经过乙烯处理的西瓜果实,贮藏2 d以后出现呼吸强度和乙烯释放量的高峰,10 d以后水渍化现象也零星出现.这些结果和1-MCP的预防效果说明,西瓜果实的水渍化败坏是一种由乙烯诱导的衰老现象.

Induction of Water-soaking Deterioration in Watermelon Fruit by Ethylene

Watermelon (Citrullus lanatus Thunb. Mansfeld) fruit were held in 50 microL/L of ethylene at 20 degrees C following 18 h application with 5 microL/L of 1-methylcyclopropene (1-MCP) to investigate the involvement of ethylene in the regulation of water-soaking. The early responses of watermelon fruit to ethylene were increased electrolyte leakage and free juice content, accompanying softening and water-soaking of placental tissue. Early evidence of water-soaking appeared in the inner pericarp near the calyx end after 2 d of ethylene treatment, and was accompanied by increased activities of ACC synthase (ACS) and ACC oxidase (ACO). While the application of 1-MCP showed no significant effects by itself, it completely suppressed water-soaking induced by exogenous ethylene. Water-soaking also developed in fruit stored over 10 d in air, and the affected fruit exhibited climacteric respiration and ethylene production peaks after 2 d of storage. These results, along with the observed prophylactic effects of 1-MCP, suggest that water-soaking in watermelon fruit is an ethylene-induced senescence phenomenon.