The uptake of surfactants into wheat

Abstract

The time course of uptake has been determined for seven poly(oxyethylene) surfactants, and one anionic surfactant (sodium dodecyl sulphate), into the leaves of wheat plants grown in a phytotron. Uptake was relatively rapid during an initial period of 24 h for six of the eight surfactants; after this period, the uptake rate was lower, and total uptake after 48 h was in the range 80‐91% for those six surfactants. The other two compounds, sodium dodecyl sulphate and cetostearyl alcohol‐22EO condensate (hexadecan‐1‐ol/octadecan‐1‐ol ethylene oxide condensate; average number of ethylene oxide units 22) were barely taken up at all. The observed time course for uptake was consistent with a complex process based on more than one rate‐determining process. The physical properties of the surfactants are discussed in relation to their observed uptake behaviour. The surfactant deposit areas, measured by microscopy, were concluded to be not particularly relevant in interpreting the uptake results. Uptake was not related to surfactant chain length, but the physical form of the hydrated surfactant on a leaf surface appeared to influence uptake behaviour.

Co-penetration of Actives and Adjuvants and Its Significance for the Matched Pair Liaison

“…Similar findings were reported by others for other radiolabelled ethoxylates and plant species like wheat, oat or field bean, i.e. C12E16 was found to be slightly behind C13E6 (24) but a C16-18E22 did not show measurable penetration (25). Figure 2 shows also that a radiolabelled alkylglucosid did not penetrate at all within 24 hours.…”

Influence of Formulation and Adjuvants on the Foliar Location and Physical Form of the Active Ingredient

“…De Ruiter et al (1988) mentioned in their study on the mode of action of a nonionic and cationic surfactant that hydrated Renex 688 [polyoxyethylene (8) nonylphenol] exists as a gel whereas hydrated Ethomeen T25 (polyoxyethylene 15 tallow amine) exists as a soft solid form, and that the differences in uptake and physical form of these two surfactants support the conclusion of Anderson and Girling (1983) that the uptake of surfactants is at least partly related to their physical form.…”

Influence of Physicochemical Properties on Uptake and Loss of Pesticides and Adjuvants from the Leaf Surface

“…This is humidity dependent. The data of Anderson and Girling (1983) and Stevens and Bukovac (1987) indicate that at 80% relative humidity water retention is approximately 1 mol H20 for a 5E chain, 5 for lOE, 12 for 15E and 20 for 20E; these values increasing two-to three-fold at 90% humidity. The short chain ethoxylates (to ca.…”

“…The data of Anderson and Girling (1983) indicate that crystallisation of sodium dodecyl sulphate occurs at 90% relative humidity. Calcium salts are generally much less soluble than sodium salts, in part because they have much higher melting points.…”