ABSTRACT
116Foliar uptake experiments with a number of 14C-labeled linear alcohol and alkylphenol poloxyethylene surfactants have demonstrated that considerable quantities of such compounds can enter plants following droplet applications of dilute aqueous solutions. The rates and total amounts of uptake varied greatly according to plant species, and both were influenced by the chemical nature of the surfactant. The surfactants examined had hydrophile-lipophile balance (HLB) values in the range 10 to 14, and maximum foliar absorption was observed for compounds having a Cl 2/C 13 alkyl chain as the hydrophobic moiety. There was little movement of any of the surfactants following penetration into leaves, but they were subsequently metabolized within the treated areas, the rate and products of metabolism again differing with plant species. On Vicia faba leaves, surfactant uptake was altered greatly in the presence of a number of different water-soluble agrochemicals, anionic compounds slowing absorption to a greater extent than cationic ones. The intimate relationship between surfactant and chemical during foliar penetration was confirmed by further experiments on the same plant with the 14C-labeled herbicide difenzoquat. The implications of our findings in terms of elucidating the possible mode of action of surfactants as spray adjuvants are discussed.
