Foliar Absorption

Plant interception, retention, coverage Foliar absorption 

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. 

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Cataldo DA, Garland TR, Wildung RE, et al. 1980. Foliar absorption of transuranic elements Influence of physicochemical form and environmental factors. J Environ Qual 9(3) 364-369. 

Stevens, P.J.G., Baker. E.A., and Anderson. N.H. Factors affecting the foliar absorption and redistribution of pesticides. 2. Physicochemical properties of the active ingredient and the role of surfactant, Pestic. Sci., 24(l) 31-53,1988. 

Ohori, Y., Ihashi, Y. (1987) Foliar absorption of pesticides using an isolated cucumber membrane. Res. Dev. Rev.-Mitsubishi Chem. 1(2), 22-26. 

Fig. 7-2. Summary of environmental pathways by which terrestrial plants may become contaminated with radionuclides. In the case of an input from atmosphere, or as a result of the process of resuspension , any external radionuclide burden may be reduced by field loss mechanisms conversely, an initially external radionuclide deposit (Rat) may become internalised (i int) following foliar absorption and translocation. Radioactive contaminants of soils may be derived either from atmospheric inputs or from seepage in ground waters. Partitioning of radionuclides in soil—soil water systems controls their availability for root absorption, which normally occurs exclusively from the liquid phase. The chemical speciation of the nuclide in this phase, however, provides a further control on bioavailability which is highly radionuclide specific.

In the case of particles, it is physical form rather than chemical characteristics which controls the velocity of deposition to vegetation, although the latter is important with respect to the subsequent processes of foliar absorption, translocation or... 

The foliar absorption coefficient k ranges from 0.3 to 1.3 for most plants. Light penetrates the vertically oriented blades of grasses rather easily in such cases, k can be near 0.4. What cumulative leaf area per ground area reduces the incident PPF by 95% for grasses with such a foliar absorption coefficient By Equation 9.5, the accumulated leaf area per unit ground area in this case is... 

Such a high foliar absorption coefficient applies to horizontal leaves with at least 0.5 g chlorophyll m-2, which can occur for crops such as potato, soybean, sunflower, and white clover (Fig. 9-6). 

Figure 9-6. Attenuation of PPF down through a plant community with erect leaves having a low foliar absorption coefficient of 0.4 and another plant community with horizontal leaves having a high k of 1.0.

Figure 9-7. Variation in leaf angle and hence foliar absorption coefficient with distance above the ground for (a) various idealized plants and (b) sugar beet measured at various canopy positions (Hodariova, 1979). Hie greater erectness of the uppermost leaves leads to a lower k for them and hence to better penetration of PPF down to the lower leaves.

Suppose that the foliar absorption coefficient is 0.7 for trees with an average... 

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). ... 

Porter, L. K., F. G. Viets, Jr., and G. L. Hutchinson (1972). Air containing nitrogen-15 ammonia Foliar absorption by corn seedlings. Science 175, 759-761. 

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. 

Certain species of plants have been found to accumulate very high concentrations of certain trace elements and these are referred as hyperaccumulator species. Plants can also intercept significant amounts of some elements through foliar absorption. Foliar absorption of solutes depends on the plant species, its nutritional status, the thickness of its cuticle, the age of the leaf, the presence of stomata guard cells, the humidity at the leaf surface, and the nature of the solutes. 

Plummer, G. L., and J. B. Kethley. 1964. Foliar absorption of amino acids, peptides, and other nutrients by the pitcher plant, Sarracenia flava. Bot. Gaz. 125(4) 245-260. 

Charnel A. Foliar absorption of herbicides study of the cuticular penetration using isolated cuticles. Physiol Veg 1986 24 491-508. 

Likewise, most physiological disturbances observed could be related to an excessive ammonium supply from rainfall and subsequent foliar absorption ... 

A bentazon-induced reduction in the foliar absorption of sethoxydim by goose grass Eleusine indica L.) has been proposed by Rhodes and Coble as a likely mechanism for the observed antagonism between these two herbicides. However, Retzlaff et aV suggested that the site of the antagonistic interaction between bentazon and sethoxydim is located in biomembranes such as the chloroplast envelope or the plasmalemma. The... 

In these experiments, the amount of herbicide distributed on the plant surface (SRF), beneath the plant cuticle (PEN), and in the air (AIR) was monitored at 7-9 time points over a 24-48-h period. The values of and fcpen, the rate constants for volatilization and penetration of the cuticle, respectively, were obtained from the compound distribution versus time data using a kinetic model and mathematical modeling. The simplest model for foliar absorption of a volatile compound is given in Eq. (8.5) ... 

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