Effet des matières organiques ajoutées au sol sur l'adsorption des herbicides. Influence de la composition des matières organiques

Effect of orgunic matter added to soil on the adsrption of herhicides. Inffneuce of the composition of the organic matter By preliminary fractionation of two organic substrates (a wheat straw and a crushed lucerne hay) we tried to evaluate the adsorption capacity of their constituents (water-soluble and lipidic substances, hemicelluloses, cellulose and lignin) in soil. Terbutryne and diuron have different affinities with the constituents of the substrates. Lignin is more adsorbent than the other constituents. With regard to adsorption, isolated constitucents form heterogeneous and interacting classes. Consequently it is difficult to define the absorption capacity of non-decomposed organic materials on the basis of their composition. Mineralization, by modifying the composition, the variations in adsorptive power of carbon residues resulting from decomposition of the substrates in the soil.     

Influence of alkyl oleates on efficacy of phenmedipham applied as an acetone:water solution on Galium aparine

Galium aparine plants were treated at the two-whorl stage with technical-grade phenmedipham. The active ingredient was applied at 10 doses as an acetone:water solution, without emulsifier, alone or in mixture with an ester of oleic acid (methyl, butyl, octyl, dodecanyl, octadecanyl). The plant response was described by a log-logistic regression model. Phenmedipham applied alone did not kill the plants even at the highest dose (1621 g a.i. ha⁻¹). In contrast, addition of any alkyl oleate to phenmedipham killed the plants at the 200–400 g a.i. ha⁻¹ doses. The alkyl oleates differently affected activity of phenmedipham. Their effects could be ranked as follows: butyl ≥ methyl; octyl> methyl; dodecanyl ≤ methyl; octadecanyl < methyl oleate. Thus, butyl and octyl oleate promoted phenmedipham activity more than methyl oleate.     

Adsorption de quelques phénylurées herbicides par des acides humiques

L'adsorption de plusieurs phcnyluré (diuron, linuron. mtox- uron, isoproturon) par des acides humiques augmente lorsque le pH diminue, Lëtablissement de liaisons hydrogène entre les molécules herbicides el les groupements fonctionnels non disso- ciés des acides humiques pourrait expliquer cet effet, Compars au calcium, au mème pH, les cations Fe³⁺, Al³⁺, Cu²⁺ ne modifient pas l'intensité de l'adsorption mais, compte tenu de la composition ionique des acides humiques, on peut supposer l'existence d'interactions entre les molcules herbicides et ces cations fixs sur les acides humiques.     

Some effects of the herbicide EL-107 on cellular growth and metabolism

Effects of the herbicide EL-107 (N-[3-(1-ethyl-1-methylpropyl)-5-isoxazolyl]-2,6-dimethoxy-benzamide) on the growth of dicotyledonous plants are described. The herbicide did not inhibit germination but reduced the growth of rape (Brassica napus L.) by half at 0.0057 mg l^?1. The most characteristic symptom induced was a swelling of the apical regions, and histological observations of root tips of Polygonum persicaria and rape revealed a progressve disappearance of the meristematic zone, which was replaced by enlarged cells almost devoid of cytoplasm. Growth of cells of Acer pseudoplatanus L. and soybean (Glycine max L.) cultured in suspension was also inhibited by EL-107, which induced a characteristic change in the cell morphology to an enlarged, rounded shape. EL-107 apparently did not block cell division; at a high concentration it produced some inhibition of protein synthesis, but in Acer cells only. In both types of cell cultures it inhibited, to some extent, the incorporation of glucose into cell wall material.