Abstract

Changes in the metabolism of 1-aminocyclopropane-l-carboxylic acid (ACC) during senescence in the light in turgid, water-stressed, and ABA-treated, excised rice leaves were examined. The decreases in levels of Chl and protein were more rapid in the water-stressed and in the ABA-treated leaves than in the turgid leaves. In turgid leaves, levels of proline remained very low, but they increased considerably as a result of water stress or treatment with ABA. The production of ethylene was strongly inhibited by water stress and by ABA through the inhibition of the synthesis of ACC and/or the conversion of ACC to ethylene. In turgid leaves, the level of 1-(malonylamino)cyclopropane-l-carboxylic acid (MACC) increased with time during incubation in the light. Water stress resulted in a pattern of accumulation of MACC similar to that in the turgid control. However, ABA blocked the malonylation of ACC.

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