UPTAKE, TRANSPORT AND METABOLISM OF THE ETHYLENE RELEASING COMPOUND CGA-15281 IN THE PEACH AND METABOLISM IN THE SOIL

S.J. Kays, S.D. Seeley, G.A. Couvillon
[14C-ethyl] labeled (2-chloroethyl)methylbis(phenylmethoxy)silane [CGA-15281] was applied to fruits and leaves of 4-year-old 'Bicentennial' peach trees [Prunus persica (L.) Batsch]. Virtually none of the parent material moved into the fruit or was taken up and transported in vegetative tissue. Of the small amount found within the vegetative tissue, there was equal distribution between acropetal and basipetal movement. The compound appears to act through the release of ethylene which penetrates the tissue rather than uptake of the parent molecule and subsequent release. CGA labeled with [14C] in the chloroethyl, methyl or methoxy position was applied to peach fruitlets to label and trace metabolites. Benzyl alcohol, benzylglucoside, benzylmethylglucoside and a CGA impurity were isolated and identified by GLC-mass spectroscopy. CGA metabolism was rapid. After 35 days, 98.9% of the original 14C, when labeled in the chloroethyl position, could be accounted for: 89% as ethylene, 0.22% as CO2, 0.32% as structural carbohydrates and 9.04% in extractable residue. Substantially lower recoveries were obtained when the molecule was labeled in the methoxy or methyl position due to volatilization and/or breakdown and volatilization of these molecular segments. Headspace analysis showed similar volatile hydrocarbons (e.g. methane, ethane, ethylene, propylene, butane and benzyl alcohol) as found in the headspace over benzyl alcohol. Less than 1% of the methyl or methoxy label was given off as [14C]-ethylene. Evolved [14C]-C02 accounted for less than 0.5% of the label applied with each of the labeling positions. The decomposition and metabolism of CGA labeled in the chloroethyl, methyl or methoxy position, was studied over a 14-month period in 3 peach orchard soil. The molecule decomposed rapidly when exposed to a soil environment. Major decomposition products were ethylene, benzyl alcohol and low levels of what have been identified by GLC/MS analysis as (2-chloroethyl)- methyl (phenylmethoxy)chlorosilane and (dichloromethyl)(chloroethyl-methylphenylmethoxy) disiloxane which appear to be formed in side reactions of CGA breakdown. A number of insoluble silicon compounds appear to also be present. The methoxy positions on the parent molecule were largely metabolized to C02 while the ethyl group was primarily liberated as ethylene. The methyl group on the parent molecule remained bound to the silicon atom forming insoluble organosilicates; little was metabolized by soil microorganisms to C02. Soil type had a small but statistically significant effect on the degree of release of ethylene from the chloroethyl position, however, did not affect the metabolism of the methoxy group or degree of partitioning of the methyl group into insoluble compounds. This difference in ethylene release could not be explained by differences in the pH, % organic matter or cation exchange capacity of the soils
Kays, S.J., Seeley, S.D. and Couvillon, G.A. (1983). UPTAKE, TRANSPORT AND METABOLISM OF THE ETHYLENE RELEASING COMPOUND CGA-15281 IN THE PEACH AND METABOLISM IN THE SOIL. Acta Hortic. 137, 29-54
DOI: 10.17660/ActaHortic.1983.137.2
https://doi.org/10.17660/ActaHortic.1983.137.2

Acta Horticulturae