ISHS Acta Horticulturae 179: V International Symposium on Growth Regulators in Fruit Production
ETHYLENE-INDUCED CHANGES IN INDOLE-3-ACETIC ACID METABOLISM IN CITRUS LEAF TISSUES DURING ABSCISSION AND SENESCENCE |
| Authors: | J. Riov, O. Sagee, R. Goren |
| Abstract:
The effect of ethylene on [14C]-indole-3-acetic acid (IAA) metabolism was studied in leaf discs and midrib sections cut from citrus (Citrus sinensis (L.) Osbeck var. Shamouti) leaves. IAA metabolites were fractionated into 80% ethanol-soluble, H2O-soluble NaOH-soluble, and insoluble components. Chromatographic analysis indicated that the ethanol and H2 0 extracts contained low molecular weight conjugates, whereas the NaOH extracts contained high molecular weight conjugates. Pretreatment of leaves with 25 microliters per liter ethylene induced abscission and increased the amount of IAA conjugates in all the above fractions. Ethylene pretreatment particularly enhanced the formation of an IAA- glucose ester and the macromolecular conjugates. A close positive correlation was found between accumulation of these conjugates and abscission of ethylene-treated leaves. Analysis of the macromolecular conjugates indicate that they consist of various cell-wall components. Similar changes in IAA metabolism were found in senescing leaves which produced large amounts of ethylene. Ethylene did not cause a significant reduction in endogenous level of free IAA whereas IAA level in senescing leaves was much lower compared to matured leaves. | |
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