A Comparison between Glyphosate and Assimilate Translocation Patterns in Tall Morningglory (Ipomoea purpurea)

Abstract

Translocation of14C-glyphosate [N-(phosphonomethyl) glycine] in tall morningglory [Ipomoea purpurea(L.) Roth., ‘Heavenly Blue’] was compared with movement of14C-photosynthate. The flow of photosynthate was manipulated by creating assimilate sinks in mature leaves and cotyledons using combinations of stem girdling, leaf shading, and localized cytokinin application. Comparisons of14C distribution patterns indicated minor differences between glyphosate and assimilate sink partitioning when14C-glyphosate or14CO2were applied to a single leaf. Labeled glyphosate moved upward through stem girdles in greater proportions than14C from photosynthate, suggesting a greater capacity for glyphosate to transfer from symplast to apoplast. When14C-glyphosate was applied to the stem,14C still moved symplastically to natural and artificial sinks, but apoplastic movement into all transpiring tissues above the site of application greatly increased. Results support the classification of glyphosate as an ambimobile rather than a phloem-mobile herbicide.

Causes of uneven desiccation of flax by glyphosate: poor penetration of the canopy and variable spray deposition

“…Glyphosate is generally considered to be ambimobile. Applied to the base of the stem, it was found to be transported in the xylem and distributed throughout the plant in cotton (Gossypiurn hirsururn) and tall morning glory (Ipornoea purpurea) (Wills, 1978;Dewey & Appleby, 1983). The pattern of activity of glyphosate applied to the lower stem of flax is consistent with these reports.…”

Non-target-site glyphosate resistance inConyza bonariensisis based on modified subcellular distribution of the herbicide

“…Applied glyphosate penetrates the plant tissue and is translocated, through the symplast or diffusely through the apoplast, to the root and shoot meristems . The transport of this herbicide is associated with the assimilate pathway, and glyphosate accumulates mainly in the youngest, most active plant parts, where it affects the target enzyme . Although the target enzyme is present in all plant tissues, it is expressed most in meristem tissues.…”

Comparisons Between X-ray Film- and Phosphorescence Imaging-Based Autoradiography for the Visualization of Herbicide Translocation

“…2,4-DB is characterized by limited translocation in both sensitive and tolerant species (Wathana et al 1972). Glyphosate is noted for extensive apoplastic and symplastic translocation following foliar application (Dewey and Appleby 1983). Spray solutions were prepared assuming a 140 L/ha spray volume, and that paraquat, 2,4-DB (dimethylamine formulation) and glyphosate (isopropylamine formulation) were to be applied at 0.13 kg ai/ha, 0.28 kg ae/ha and 0.45 kg ae /ha, respectively.…”