Abstract
Glyphosate (N-phosphonomethylglycine) was readily transported in sugar beet plants (Beta vulgaris L., Klein E type, monogerm). Concentrations in sink leaves reached 2.5 to 13.7 micromolar in 10 hours from a 15 millimolar solution supplied to one mature leaf. Distribution of glyphosate followed that of [3H]sucrose used as a marker for materials transported by phloem, indicating that this is the primary means for distribution of glyphosate. Possible mechanisms of entry into the sieve tubes were evaluated using isolated leaf discs. Concentration dependence of uptake and kinetics of exodiffusion from tissue indicate a passive, nonfacilitated mechanism. Uptake was not affected by pH, eliminating the passive, weak acid mechanism. Permeability of the plasmalemma to glyphosate was calculated as 1.7 × 10−10 meters per second. This characteristic would allow slow entry and exit from the phloem, and together with other physiological parameters of the plant, is postulated to allow accumulation and transport in the phloem.
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- Brecke B. J., Duke W. B. Effect of Glyphosate on Intact Bean Plants (Phaseolus vulgaris L.) and Isolated Cells. Plant Physiol. 1980 Oct;66(4):656–659. doi: 10.1104/pp.66.4.656. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Christy A. L., Ferrier J. M. A Mathematical Treatment of Munch's Pressure-Flow Hypothesis of Phloem Translocation. Plant Physiol. 1973 Dec;52(6):531–538. doi: 10.1104/pp.52.6.531. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Fife J. M., Price C., Fife D. C. Some properties of phloem exudate collected from root of sugar beet. Plant Physiol. 1962 Nov;37(6):791–792. doi: 10.1104/pp.37.6.791. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Tyree M. T. A simple theory regarding ambimobility of xenobiotics with special reference to the nematicide, oxamyl. Plant Physiol. 1979 Feb;63(2):367–374. doi: 10.1104/pp.63.2.367. [DOI] [PMC free article] [PubMed] [Google Scholar]