Role of Abscisic Acid in the Onset of Ripening of Tomato Fruits-- An Investigation with Ripening impaired Mutant Nr-2

乙烯在番茄果实成熟过程中起着关键作用。乙烯的产生始于绿色成熟的果实，并自催化地增加，导致红色成熟的果实。然而，它是未知的因素（S）触发乙烯生产成熟的绿色水果。本研究通过对Nr-2种子萌发特性的研究，测定了叶片、未成熟绿色果实和成熟绿色果实中阿坝含量，并对Nr-2成熟绿色果实进行了外源阿坝诱导成熟的研究。Nr-2种子萌发早于番茄种子，具有顺熟特性。Nr-2番茄成熟绿色果实中阿坝含量低于正常成熟特性的果实。在一个成熟的绿色果实中，应用外源阿坝可以诱导果实成熟，由此我们认为阿坝可能是乙烯产生的启动因子之一，而Nr-2果实中ABA的缺乏可能是其果实成熟失败的原因。

Ethylene plays a pivotal role in the onset of ripening of tomato fruits. Ethylene production starts in green-mature fruits and increases autocatalytically, resulting in red-ripened fruits. However, it is not known about factor (s) which trigers ethylene production in mature-green fruits. We had found that the tomato plants of ripenig-impaired mutant Nr-2 showed growth characteristics, which were tought to be caused by the deficiency of abscisic acid (ABA).In the present study we investigated the germination profile of Nr-2 seeds, measured ABA contents in leaves, immature-green fruits and mature-green ones and tried to induce ripening by the application of exogenous ABA to mature-green Nr-2 fruits. Nr-2 seeds germinated earlier than those of tomato seeds with ordinal ripening characteristics. Mature-green fruits of Nr-2 tomato contained less ABA than those of tomato fruits of ordinal ripening charcteritics. In one mature-green fruit we could induce ripening by the application of exogenous ABA.Form these results we thought that ABA might be one of the factors for the onset of ethylene production and that its deficiency in Nr-2 fruits might cause the failure of ripening of their fruits.