The experimental herbicide EMD-IT 5914 [difunon, 5-dimethyl-amino-methylene-2-oxo-4-phenyl-2,5-dihydrofurane-carbonitrile-(3)] was applied to unicellular algae and its effect on growth, oxygen evolution and photosynthetic electron transport measured. Inhibition of biosynthesis of chloroplast pigments was evaluated in relation to the activities of porphobilinogenase and δ-aminolevulinic acid dehydratase. The only direct effect of the herbicide was an inhibition of carotenoid biosynthesis but not of photosynthetic electron transport or enzymic activities connected with porphyrin biosynthesis. Chlorophyll bleaching is considered to be a secondary process.

Uptake, translocation, and metabolism of propham (isopropyl carbanilate) were ascertained for wheat (Triticum aestivum L., ‘Neepawa’) sugarbeet (Beta vulgaris L., ‘HH-10’), and alfalfa (Medicago sativa L., ‘Cherokee’) when grown in either liquid culture or in soil. Three-week-old wheat and 5-week-old sugarbeet and alfalfa plants were treated with 14C-propham in liquid culture for 1, 2, and 4 days. Other plants were placed in treated soil at 10 weeks after germination and grown for 15 weeks. Wheat absorbed 98%, sugarbeet 93%, and alfalfa 81% of the propham from solution after 4 days. Propham was translocated in all species. Under liquid culture, three polar metabolites of propham were isolated from wheat and alfalfa extracts and one was isolated from sugarbeet extracts. The agylcone moiety of the two most polar wheat metabolites was isopropyl-4-hydroxycarbanilate and that of the least polar metabolite was isopropyl-2-hydroxycarbanilate. The aglycone of all alfalfa and sugarbeet polar metabolites was isopropyl-4-hydroxycarbanilate. Only one polar metabolite was isolated from all soil-treated plants. The aglycone moiety was determined to be isopropyl-4-hydroxycarbanilate. Of the propham absorbed 95, 91, 89, and 36% was metabolized by sugarbeet roots, sugarbeet leaves, wheat leaves, and alfalfa leaves, respectively, after a 4-day liquid culture treatment. Propham was 100% metabolized when applied to plants via soil application.

The adsorption of atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] was measured on soil at water:soil ratio of 5:1 and 0.4:1. The adsorption isotherms for atrazine were described by the Freundlich equation. A decrease in water:soil ratio and in soil moisture content led to an increased adsorption of the herbicide. Increasing the concentration of electrolytes in the soil solution by adding solutions up to 0.1M CaCl2 increased atrazine adsorption. Greater amounts of atrazine were adsorbed at 30 than at 5 C on four soils at 0.1 bar moisture content. This indicates an endothermic reaction which was observed both before and after correction for differential atrazine solubility due to temperature. Thermodynamic quantities associated with the adsorption reaction were calculated to characterize the adsorption of atrazine on soil.