Growth of Cultured Carrot Cells as Affected by Glyphosate, Asulam and Various Plant Metabolites
Killmer, John Louis
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Permalink
https://hdl.handle.net/2142/68463
Description
Title
Growth of Cultured Carrot Cells as Affected by Glyphosate, Asulam and Various Plant Metabolites
Author(s)
Killmer, John Louis
Issue Date
1980
Department of Study
Agronomy
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
Garden carrot (Daucus carota L. cv. Danvers) root cells were grown in flasks containing 100 ml defined medium following inoculation with 0.5 g fresh weight of cells. Cells were grown in the presence or absence of the herbicides glyphosate {N-(phosphonomethyl) glycine}, asulam {methyl (4-aminobenzensulphonyl carbamate)} and various plant metabolites and were harvested for fresh weight determinations by filtering on miracloth under vacuum. Glyphosate was autoclaved with the medium, but asulam and other additions to the culture medium were filter sterilized.
Various cytokinins and purines were ineffective in reversing glyphosate (0.25 mM) induced growth inhibition of carrot cell suspension cultures. Aspartate was particularly effective in reversing glyphosate inhibition. The effectiveness of reversal corresponded to the aspartate concentration. Asparagine and various combinations of lysine, methionine, threonine and homoserine (eventual products of aspartate metabolism) were not effective in reversing glyphosate inhibition. When organic acids of the tricarboxylic acid cycle were added to the medium, particularly good reversal of inhibition could be obtained with (alpha)-ketoglutarate, succinate and malate. Citrate provided only moderate reversal but the reversal given by glutamate was comparable to that of aspartate and the more effective tricarboxylic acid cycle intermediates.
Pyruvate was somewhat toxic to cells when added early in the cell cycle but was most effective at reversing glyphosate inhibition when added at this time. If pyruvate addition was delayed, it was less toxic but was also a less effective reversing agent for glyphosate inhibition.
All of the effective reversing agents for glyphosate inhibition have previously been shown to be effective detoxifying agents for ammonia in similar cell systems. The results of this study suggest that glyphosate inhibition of growth in this system may be at least partially due to ammonia toxicity.
Growth inhibition by asulam of carrot cell suspension cultures can be antagonized with p-aminobenzoic acid or folic acid supplements to the media. Double reciprocal plots of growth and antagonist concentration indicate inhibition to be competitive. The reversal by p-aminobenzoic acid and folic acid fit the structural relationship of asulam to p-aminobenzoic acid and the substituted sulfonamides.
These studies indicate that asulam, like sulfanilamide, inhibits plant growth by interfering with folate synthesis either by producing inactive or inhibitory folate analogs or by inhibiting the synthesis of folate.
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