Uptake and Distribution of N-Phosphonomethylglycine in Sugar Beet Plants

Document Type

Article

Publication Date

9-1-1981

Publication Source

Plant Physiology

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.

Inclusive pages

668-672

ISBN/ISSN

0032-0889

Publisher

American Society of Plant Biologists

Volume

68

Peer Reviewed

yes

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