Aharoni N, Yang S F
Department of Fruit and Vegetable Storage, Agricultural Research Organization, The Volcani Center, Bet Dagan 50250, Israel.
Plant Physiol. 1983 Nov;73(3):598-604. doi: 10.1104/pp.73.3.598.
Exogenously supplied indole-3-acetic acid (IAA) stimulated ethylene production in tobacco (Nicotiana glauca) leaf discs but not in those of sugar beet (Beta vulgaris L.). The stimulatory effect of IAA in tobacco was relatively small during the first 24 hours of incubation but became greater during the next 24 hours. It was found that leaf discs of these two species metabolized [1-(14)C]IAA quite differently. The rate of decarboxylation in sugar beet discs was much higher than in tobacco. The latter contained much less free IAA but a markedly higher level of IAA conjugates. The major conjugate in the sugar beet extracts was indole-3-acetylaspartic acid, whereas tobacco extracts contained mainly three polar IAA conjugates which were not found in the sugar beet extracts. The accumulation of the unidentified conjugates corresponded with the rise of ethylene production in the tobacco leaf discs. Reapplication of all the extracted IAA conjugates resulted in a great stimulation of ethylene production by tobacco leaf discs which was accompanied by decarboxylation of the IAA conjugates. The results suggest that in tobacco IAA-treated leaf discs the IAA conjugates could stimulate ethylene production by a slow release of free IAA. The inability of the exogenously supplied IAA to stimulate ethylene production in the sugar beet leaf discs was not due to a deficiency of free IAA within the tissue but rather to the lack of responsiveness of this tissue to IAA, probably because of an autoinhibitory mechanism existing in the sugar beet leaf discs.
外源供应的吲哚 - 3 - 乙酸（IAA）刺激了烟草（烟草）叶圆片的乙烯生成，但对甜菜（甜菜）叶圆片却没有这种作用。在培养的最初24小时内，IAA对烟草的刺激作用相对较小，但在接下来的24小时内作用增强。发现这两个物种的叶圆片对[1 - （14）C]IAA的代谢方式有很大不同。甜菜叶圆片中的脱羧速率远高于烟草。烟草中游离IAA含量少得多，但IAA结合物水平明显更高。甜菜提取物中的主要结合物是吲哚 - 3 - 乙酰天冬氨酸，而烟草提取物中主要含有三种极性IAA结合物，这些结合物在甜菜提取物中未发现。未鉴定结合物的积累与烟草叶圆片中乙烯生成的增加相对应。重新施用所有提取的IAA结合物会极大地刺激烟草叶圆片的乙烯生成，同时伴随着IAA结合物的脱羧。结果表明，在烟草经IAA处理的叶圆片中，IAA结合物可通过缓慢释放游离IAA来刺激乙烯生成。外源供应的IAA不能刺激甜菜叶圆片乙烯生成，并非由于组织内游离IAA缺乏，而是由于该组织对IAA缺乏反应性，这可能是因为甜菜叶圆片中存在一种自抑制机制。
