Translocation of¹⁴C-Glyphosate and¹⁴CO₂-Labeled Photoassimilates in Canada Thistle (Cirsium arvense)

Abstract

Translocation of14CO2-labeled photoassimilates was compared to movement of14C-glyphosate [N-(phosphonomethyl)glycine] in Canada thistle [Cirsium arvense(L.) Scop. ♯ CIRAR] under field and controlled-environment conditions. Field-grown Canada thistle plants were treated on mature upper leaves at the midflower stage in mid-June and harvested 8 days later. No differences were found in glyphosate and assimilate distribution, and movement was primarily basipetal. Of the glyphosate and photoassimilates translocated from the treated leaves, 25 and 31%, respectively, were recovered from the roots, while 59 and 58%, respectively, were found in the shoot tissue below the treated leaf. Concentration of labeled glyphosate in the roots as much as 95 cm from the treated shoot was as high as at the base of the treated shoot. Photoperiods that induce flowering (15 h) or maintain vegetative growth (13 h) did not differentially affect the distribution of photoassimilates or glyphosate in 7-week-old Canada thistle plants in the growth chamber. In growth chamber-grown plants equivalent amounts of glyphosate and assimilates were translocated out of treated leaves; however, relatively more glyphosate than photoassimilates accumulated in the roots.

Modelling interactions between herbicide and nitrogen fertiliser in terms of weed response

“…A few studies have indicated a correlation between herbicide and assimilate translocation (e.g. McAllister & Haderlie, 1985), with an increased nitrogen application increasing the quantity of assimilate and its translocation, thus resulting in an increased herbicide translocation. However, these mechanisms may differ between herbicides and weed species.…”

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.…”

Modeling Xenobiotic Uptake and Movement: A Review

“…With regard to xenobiotic molecules such as herbicides, little is known about their loading into the phloem. However, it is generally assumed that xenobiotic transport in the phloem follows the direction of sucrose flow (118,119). Hence, in species where sucrose molecules are loaded through the apoplastic pathway, it is conceivable that xenobiotic molecules may be loaded similarly.…”