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

乙烯在番茄果实的成熟过程中起着关键作用。乙烯的生产始于绿色成熟的水果，并通过自催化作用增加，从而产生红色成熟的水果。然而，它不知道的因素(s)触发乙烯生产成熟的绿色水果。我们发现成熟受损突变体Nr-2的番茄植株表现出生长特性，这可能是由于ABA缺乏引起的。本研究研究了Nr-2种子的萌发情况，测定了叶片、未成熟果实和成熟果实中ABA的含量，并尝试通过外源ABA对成熟绿色果实进行催熟。Nr-2种子萌发时间早于番茄种子，具有正常成熟特征。Nr-2番茄青熟果实中ABA含量低于正常成熟特征的番茄果实。在一个成熟的青果中，外源ABA可以诱导成熟。由此，我们认为ABA可能是乙烯产生的启动因素之一，其在Nr-2果实中的缺乏可能导致果实成熟失败。

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.