Activity Enhancement and the Mechanism of Glyphosate Action in Common Cocklebur

Common cocklebur (Xanthium pensylvanicum Wallr.) root tips were used to investigate the mechanism of glyphosate {N-(phosphonomethyl)glycine} action. The incorporation but not the uptake of ('14)C-leucine was significantly decreased by 2 h after treatment. The incorporation declined steadily over a 32 h time course. The uptake of ('33)P by the roots was temporarily stimulated by glyphosate and, as a percent of total ('33)P taken up, there was decreased incorporation into RNA and DNA fraction by 8 h. The endogenous cytokinin content was measured in root tips at 4 and 12 h after glyphosate application. Glyphosate does not alter cytokinin accumulation by 12 h. Our results indicate that glyphosate may rapidly inhibit protein synthesis. Successive application of the cytokinin N('6)-((DELTA)('2)-isopentenyl) adenosine to the first leaf of cocklebur increased the uptake and altered the distribution of ('14)C-glyphosate that was applied 24 h later on the second cocklebur leaf. The results indicate that the exogenously applied cytokinin is taken up and may be transported to other areas in the plant. At 12 h after application there was significantly more ('14)C-glyphosate in the most rapidly expanding leaves, leaves three and four. To determine if cytokinins increased transpiration thereby increasing the uptake and altering the movement of glyphosate, leaf diffusive resistance was measured. At 24, 36 and 48 h after cytokinin application, there were no diffusive resistance differences in any leaf.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Agronomy

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2014

Author dc:creator

• Foley, Michael Edward

• Agriculture, Agronomy

Identifier

(UMI)AAI8218468

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/71572