The mechanism of selectivity and site of action of clomazone in tolerant-soybean and susceptible-cotton photomixotrophic cell suspension cultures
Norman, Michael Alex
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https://hdl.handle.net/2142/19294
Description
Title
The mechanism of selectivity and site of action of clomazone in tolerant-soybean and susceptible-cotton photomixotrophic cell suspension cultures
Author(s)
Norman, Michael Alex
Issue Date
1990
Doctoral Committee Chair(s)
Liebl, Rex A.
Department of Study
Crop Sciences
Discipline
Agronomy
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Agriculture, Agronomy
Language
eng
Abstract
Clomazone (2-(2-chlorophenyl)methyl-4,4-dimethyl-3-isoxazolidinone) is a selective preplant incorporated herbicide for use in soybean (Glycine max (L.) Merr.). Studies were conducted to determine the unknown mechanism of selectivity and site of action of clomazone in tolerant soybean (SB-M) and susceptible-cotton (Gossypium hirsutum (L.), COT-M) photomixotrophic cell suspension cultures.
The mechanism of soybean tolerance to clomazone could not be attributed to differential absorption, translocation, and metabolism. SB-M cells absorbed more clomazone than COT-M cells and nearly identical levels of parental clomazone were recovered from both cell lines for all treatments. Assuming parental clomazone is the active form of the herbicide, these observations implicate differences at the site of action as the mechanism of selectivity. Although pooled metabolite fractions from both cell lines did not significantly reduce the leaf chlorophyll (chl) content of soybean seedlings, the pooled metabolite fraction from COT-M cells significantly reduced the leaf chl content of velvetleaf seedlings. Consequently, conversion of clomazone to an active form (bioactivation) by susceptible species may also account for soybean tolerance to clomazone.
Clomazone did not inhibit terpene synthesis in SB-M cells but significantly reduced the quantity and the level of MEV incorporation into chl, carotenoid, tocopherol, and plastoquinone of COT-M cells. Consequently, the site of clomazone action is after MEV and before GGPP within chloroplasts, the site of chl, carotenoid, tocopherol, and plastoquinone synthesis. Sequestration of clomazone from the chloroplast does not account for soybean tolerance to clomazone.
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