Absorption, glyphosate

Sprankle, P., Meggitt, W.F., and Penner, D. Absorption action and translocation of glyphosate, Weed Sci., 23 235-240, 1975. Sprankle, P., Meggitt, W.F., and Penner, D. Absorption, mobility, and microbial degradation of glyphosate in soil, Weed Sci., 23 229-234, 1975a. 

Monquero, P.A., P.J. Christoffoleti, M.D. Osuna, R. De Prado Amian, A.J. Matas, and A. Heredia. (2004). Absorption, translocation, and metabolism of 14C-glyphosate and leaf surface and wax analysis. 4th International Weed Science Congress, p. 60, S15MT08P00. 

Ahmadi, M.S., L.C. Haderlie, and G.A. Wicks (1980). Effect of growth stage and water stress on bamyardgrass (Echinochloa crus-galli) control and on glyphosate absorption and translocation. Weed Sci., 28 277-282. 

Glyphosate is the active ingredient of several broad spectrum commercial herbicides marketed by Monsanto St. Louis MO, that act by foliar absorption. Roundup is the most generally familiar of these products others include Vision, a formulation used widely in silvicultural weed control in the Pacific Northwest, and Rodeo. These formulations are water soluble and under most conditions have negligible residual activity in soil (i). ... 

The phytotoxic effect of glyphosate can be increased by additives enhancing absorption and translocation. According to the investigations of Wills (1973) the addition of various salts and surfactants to glyphosate does not increase its initial phytotoxicity, but increases the duration of effectiveness from 2 to 8 months. Of the cations K, of the anions POJ had the best effect. 

Absorption and Translocation. Absorption and translocation of glyphosate is summarized and discussed in depth elsewhere... 

Not surprisingly, glyphosate absorption is also affected by species differences in cuticle structure and leaf morphology. Using the track sprayer method, foliar absorption of " C-glyphosate at field use rates with a flat fan nozzle ranged from 20 to 36% in velvetleaf, prickly sida, kochia and RR corn [10, 14]. These results indicated that studies on foliar absorption of glyphosate not only need to employ a relevant method (i.e., track sprayer) but also be conducted in the species of interest. 

Fig. 6.2.2. Comparison of foliar absorption of C-glyphosate with time (hours after treatment, HAT) in commercial formulations A, B, and C using over-the-top track spray application in young velvetleaf plants.

With the track sprayer method, systemic translocation of absorbed glyphosate among commercial formulations was measured in roots that were shielded from the spray in velvetleaf plants. Formulation A, which showed the highest absorption (28%, Fig. 6.2.2), showed 6% translocation to roots at 24 HAT (Fig. 6.2.3) [10]. Root translocation was proportional to foliar absorption and followed the ranking of formulation A > C > B, which is also the ranking of overall plant efficacy. These results showed that, even with efficient absorption, only about one-third of the applied dose was absorbed, and only a fraction of that was translocated to the roots at 24 HAT. Since the amount translocated was proportional to that absorbed, increasing absorption would increase overall efficacy as long as translocation is not hindered in the process. 

Much more sensitive and less time-consuming techniques such as mass spectrometry, atomic emission, and atomic absorption are needed for the analysis of pollutants. Detectors such as graphite furnace-atomic absorption spectrometer (GF-AAS), inductively coupled plasma-mass spectrometer (ICP-MS), or inductively coupled plasma-atomic emission spectrometer (ICP-AES) seem to be ideal candidates for the analysis of trace metals because of their very low detection hmits. The high temperatures used avoid the need for tedious digestions in many samples. FFF-gas chromatography-mass spectrometry could perhaps be used in the analysis of particular organic molecules. Another extremely sensitive technique applied in the study of adsorption behavior of pollutants is to add radiolabeled adsorbates (such as P04, " C-atrazine, and ""C-glyphosate ) to study the distribution of the pollutant as a function of size. 

Sprankle, R, W.F. Meggitt, and D. Petmer. Absorption, Mobility, and Microbial Degradation of Glyphosate in Soil, Weed Sci., 23 229-234 (1975a). 

Wester RC, Melendes J, Sarason R, McMaster J, Maibach HI. Glyphosate skin binding, absorption, residual tissue distribution, emd skin decontamination. Fundam Appl Toxicol. 1991 16 725-32. 

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