ALBERT

Notes: Summary. Studies were conducted to determine the influence of pyrazon (5-amino-4-chloio-2-phenyl-3(2H)-pyridazinone) on photosynthesis. A strong inhibiting effect on O2 evolution from leaf discs of several species was recorded. For most species a concentration of 5 × 10−5 M caused a reduction of about 50% in the rate of photosynthesis. Photosynthesis of sugar beet, highly resbtant to pyrazon, was reduced to 50% by a concentration of 7–5 × 10−5 M. Since these differences cannot account for the great divergence in susceptibility to pyrazon, it is suggested that the selectivity of this herbicide results from degradation and differential accumulation in the foliage.Pyrazon was phytotoxic to plants of tomato and pigweed (Amaranthus retrofiexus L.) kept in the light but not when kept in the dark, after foliage application. The conclusion that pyrazon inhibits the mechanism of photosynthesis and causes starvation for carbohydrates, was strengthened by the fact that external feeding of glucose overcame the toxicity of the compound in tomato plants. These results and a possible mode of selectivity are discussed.

Notes: Summary. 3,4,3′,4′-Tetrachloroazobenzene (TCAB) and TCAB-14C were supplied to the roots of rice (Oryza sativa L.) plants in nutrient solution. An analysis of the shoots indicated that the TCAB was absorbed and translocated to the shoots. The translocated material was characterized by gas-liquid chromatography and mass spectrometry. Roots were exposed to saturation concentrations of TCAB-14C in liquid culture to determine the translocation and distribution of the compound. Only 5′6% of the total azobenzene present in the nutrient solution was absorbed by the intact rice plants and only 3′2% of the absorbed TCAB-14C was translocated to the shoots after 12 days of treatment. No TGAB was isolated from plants treated with propanil or 3,4-dichloroaniline after 14 days of treatment.

Notes: Summary. The herbicides studied were 2,4-D, 2,4-DB, dicamba and orthoarsenic acid. Herbicide content in the roots was taken as an overall measure of penetration into and absorption by the leaves, and of translocation to the roots.A significantly greater 2,4-D content resulted from foliar application at pH 3–5 than at higher values, though at pH 8–5 the inclusion of triethanolamine significantly increased the 2,4-D content. No evidence was obtained that a greater 2,4-D content should result from foliage applications of 2,4-DB than from 2,4-D. Dicamba gave a greater herbicide content than 2,4-D when applied at high concentration at 20° C but not at 25° C, probably because of less injury at the lower temperature.Concentrations of Tween 20 up to 2% had no deleterious effect on the 2,4-D content; on the other hand 2,4-D content was lowered by 0–25% or more of cetyltrimethyl-ammonium bromide. Poor wetting is not the cause of the variable herbicide contents sometimes obtained.Orthoarsenic acid, which has given better control of the weed than 2,4-D, was very poorly translocated; its effectiveness is due to its high intrinsic toxicity.Etudes sur la teneur en herbicide des racines de Chondrilla juncea L. á la suite d'applications sur les feuilles

Notes: Summary. The adsorption of simazine from, and subsequent desorption into, 0–01 M calcium chloride solution was investigated using twenty-three Rothamsted soil samples from sites differing greatly in cropping history and manurial treatment. Organic carbon content was the only factor related to the ability of the soils to sorb simazine; this accounted for 90% or more of the variation between soils Equilibrium was attained during adsorption in from fewer than 2 to more than 24 hr. Equilibrium during desorption was only occasionally attained within 24 hr. Differences between theoretically predicted and measured concentrations of simazine in solution following desorption were least for soils that attained equilibrium fastest during adsorption. Differences in adsorption and desorption kinetics between soils could not be related to soil pH, organic carbon content or cropping and manuring history. Comparisons of unlimed and limed soils suggested that no simnazine was lost by acid hydrolysis during the experiments.Adsorption et désorption de la simazine par quelques sols de Rothamsted

Notes: Résumé. L'absorption initiale et la migration du 14G-métobromuron se produisirent avec une vitesse identique dans Sinapis arvensis L. et Veronica persica Poir., mais, avec un traitement plus prolongé, [‘accumulation par unité de surface foliaire fut plus importante chez Veronica persica. II n'y eut pas d'accumulation ultérieure dans les racinrs, les tiges, les pétioles ou les nervures foliaires principales des deux espèces après le début de diminution de la radioactivité. II y eut toutefois une accumulation continue sur le bord des feuilles. Aucune relation ne peut être êtablie entre l'absorption et la migration d'une part, et les différences de sensibilityé des deux especes vis-i-vis du mitobromuron d'autre part.L'absorption et la migration du 14C-métobromuron apparurent légèment plusrapides chez Solanum tuberosum, variété Isola que chez la variété Delos. Ceite différence disparut rapidement et la concentration finale par unité de surface fut plus élevée chez Delos que chez Isola. L'accumulation de métobromuron dans les racines, les tiges, les petioles el les nervures des feuilles cessa lorsqu'une concentration particulièere fut alteinte. Dans les portions du limbc entre les nerures et au bord des feuilles, l'accumulation of poursuivit durant toutc I'expérience. Aucune relation ne peut être e'tablie entre l'absorption et la migration d'une part et la sensibilité des deux cultivars d'autre part.Les autoradiogrammes montrèrent que, dans les expériences où le 14C-metoéromuron fut applique sur les racines et sur les feuilles de Sinapis arvensis, de Veronica persica et des deux variétés de pomnies de terre, le métobromuron est, dans des conditions normales, ohligatoirement transporté dans le xylème.Summary. Initial uptake and transport of 14C-metobromuron occurred equally rapidly in Sinapis arvensis L. and Veronica persica Poir., but with longer treatment, accumulation per unit leaf area was greater in V. persica. There was no further accumulation in the roots, stems, petioles or main leaf veins of either species after the initial increase in radioactivity. There was, however, continued accumulation in the leaf margins. No relation was found between uptake and translocation and the differential susceptibility of the two species to metobromuron.Uptake and translocation of 14C-metobromuron was rather more rapid in Solanum tuberosum L. cv. Isola than in cv. Delos. This difference soon disappeared and the final content per unit leaf area was greater in cv. Delos than in cv. Isola. Accumulation of metobromuron in the roots, stems, petioles and leaf veins ceased when a particular concentration had been reached; in the interveinal areas of the legal margins accumulation continued throughout the experiment period. No relation was found between uptake and translocation and the differential susceptibility of the two cultivars.Evaluation of the autoradiograms from experiments with root- and leaf-applied 14C-metobromuron in Sinapis arvensis, Veronica persica and the two potato varieties indicated that under normal conditions metobromuron is obligatorily translocated in the xylem.