Surfactant‐enhanced foliar uptake of some organic compounds: Interactions with two model polyoxyethylene aliphatic alcohols

Abstract

Interactions occurring during the surfactant‐enhanced foliar uptake of seven model organic compounds were examined using two homogeneous surfactants, hexaethylene glycol monotridecyl ether (C13E6) and hexadecaethylene glycol monododecyl ether (C12E16). Surfactant–compound and compound–surfactant interactions were detected by measurement of their relative uptake rates following application of c. 0·2 μl droplets of the corresponding radiolabelled formulations. The magnitude of surfactant–compound interaction was found to vary according to the physicochemical properties of both the compound and the surfactant, and was influenced by surfactant concentration and target plant species. Interactive and non‐interactive mechanisms, both leading to substantial enhancement of compound uptake, could be identified, but their precise nature could not be elucidated. Although penetration of C13E6 into the site of application appeared to be essential in order to activate the uptake of a compound, substantial absorption of C12E16 was not always required to produce the same effect. The results are discussed in the light of possible sites and modes of action for activator polyoxyethylene surfactant adjuvants.

Polydisperse ethoxylated fatty alcohol surfactants as accelerators of cuticular penetration. 2: Separation of effects on driving force and mobility and reversibility of surfactant action

“…WL 110547 slightly decreased penetration, but this effect occurred only immediately after application, because later (after the ®rst sample at 2 h) rates of penetration (slopes) were identical to those of the control. The decrease in penetration after one day was about 10% and a similar effect was observed by Stock and Holloway 3 and Stock et al 29 who reported a decrease of surfactant (C13E6) uptake into bean leaves of 15 to 60% in the presence of various amounts of WL 110547.…”

“…The negative effect of phenylurea on penetration of C12E8 across Pyrus CM agrees with the results obtained for its effects on the penetration of C12E16 into leaves of other species. 29 We suggest that the effect of phenylurea is related to the free amide group, since even more inhibiting effects on surfactant penetration were observed for an excess amount of urea (Baur, unpublished results). It is known that urea interacts with ethoxy groups and slightly with aliphatic chains and it is sometimes included in pure surfactants to solidify them for better transport properties.…”

“…29,32 Although differences in the time course of penetration existed among species, penetration after one day was at least 63% (Citrus aurantium). Penetration was most rapid with Pyrus CM (b80% within one day).…”

Surfactant-Increased Glyphosate Uptake into Plasma Membrane Vesicles Isolated from Common Lambsquarters Leaves

“…Cationic polyoxyethylene tertiary amine surfactants are more effective than nonionic surfactants at promoting glyphosate phytotoxicity (Wyrill and Bumside, 1977;Riechers, 1992). Although several studies have examined surfactant mode of action in promoting glyphosate phytotoxicity (O'Donovan et al, 1985;Sherrick et al, 1986aSherrick et al, , 1986bde Ruiter et al, 1988;Gaskin and Holloway, 1992;Rdyneberg et al, 1992;Stock et al, 1992), the precise mechanism(s) of surfactant interaction has not been deduced. Surfactants promoting greatest glyphosate phytotoxicity are required at higher concentrations than necessary for maximum reduction of the spray solution surface tension, indicating that their mode of action is not limited to increasing the spreading characteristics of the spray droplet (Sherrick et al, 1986b).…”

The use of adjuvants to improve uptake of phosphorous acid applied to Pinus radiata needles for control of foliar Phytophthora diseases

“…There was no additional benefit from using a higher concentration of 0.2% (Treatment 6; Table 1). This class of adjuvant is known to improve the adhesion and spreading properties of sprays, and has been shown to promote increased uptake of a range of compounds on a variety of species (Stock et al 1992). These authors also showed that the magnitude of increased penetration varied according to properties of both the compound and the adjuvant and was influenced by surfactant concentration and target plant species.…”