| Summary: | The influence of light and darkness incubation on ethylene forming activity from 1-aminocyclopropane-1-carboxylic acid (ACC) in citrus (Citrus sinensis L. Osbeck cv. 'Salustiana) mature leaf discs was studied. Leaf discs incubated 48 hours inlight produced 20 times greater ethylene than in darkness. Twenty-four hours light and darkness alternative incubations were carried out. In any case, transference of discs from the light to the dark resulted in inhibition of ethylene forming activity. Effects of DCMU (3-(3,4-
dichlorophenyl)-1,1-dimethylurea, inhibitor of photosynthetic electron flow) and KCN (inhibitor of cytochrome oxidase) were studied,, DCMU at 0.1 mM concentration inhibited ethylene forming activity after 48 h incubation in light at 95%.However, ethylene forming activity was not affected by DCMU in the dark. On the other hand, 1mMKCN stimulated considerably ethylene forming activity both in the light and dark. Incubation in a CO, enriched atmosphere did not affect ethylene forming activity in light. Therefore, respiratory CO, release could not be the responsible of ethylene forming activity inhibition in the dark. Increase on ethylene production in light from ACC in mature leaf discs is related with the ethylene forming enzyme (EFE) because of CO, + ion
(inhibitor of EFE activity) reduced highly ethylene production from ACC both in the light and dark. Likewise mannitol (stimulator of EFE activity and ACC synthesis) enhanced ethylene production from ACC both in the light and in the dark. Cycloheximide (inhibitor of protein synthesis) also inhibited ethylene production from ACC. Therefore, enzyme synthesis could be required for the ethylene forming activity from ACC.
|
|---|