Summary: Résumé: Zusammenfassung Field studies were conducted over a 4‐year period to determine whether weed emergence could be increased by incorporating germination stimulants into the soil. Sodium azide (4.5–36 kg azide ha−1), ammonium nitrate (34–67 kg nitrate ha−1), and butylate (0.2–0.4 kg ai ha−1) were used. Sodium azide was the most consistent stimulant of indigenous weed emergence over all experiments and seasons, but there was great variability in its effects and the highest application rate sometimes inhibited emergence. Consistent stimulation of broad‐leaf weed emergence occurred following September applications of 4–5 kg azide ha−1 of sodium azide. Sodium azide at 4.5 kg azide ha−1 increased grass plus broad‐leaf weed emergence 43% based on summer applications in three growing seasons. No general recommendation for stimulating the emergence of weeds can be made because stimulation was a function of rate of application, season of the year, and post‐treatment environment. Influence de traitments chimiques sur la levée des mauvaises herbes Des études portant sur une durée de quatre ans ont été conduites afin de déterminer si l'incorporation dans le sol de stimulants de germination pouvait augmenter la levée des mauvaises herbes. Les produits essayés ont été le nitrure de sodium (4, 5–36 kg de nitrure ha−1), le nitrate d'ammonium (34–67 kg nitrate ha−1), et le butylate (0, 2–0, 4 kg ma ha−1). C'est avec le nitrure de sodium que la stimulation de la levée des graines en place a été observée le plus régulièrement, au cours de plusieurs expériences effectuées en différentes saisons; cependant, une grande variabilité de l'effet de ce produit a été notée, et les doses d'application les plus élevées ont parfois inhibé les levées. Appliqué en septembre à la dose de 4, 5 kg nitrure ha−1, le nitrure de sodium stimule d'une manière régulière la levée des dicotylédones. Des traitements d'été opérés durant trois années ont montré qu'à cette dose, il augmente la levée des mono et des dicotylédones de 43%. Il n'est cependant pas possible de donner des recommandations générales pour la stimulation des levées de mauvaises herbes, car cette stimulation dépend de la dose appliquée, de la saison pendant laquelle elle est opérée, et des conditions qui régnent après le traitement. Chemische Beeinflussung des Auflaufens von Unkräutern In einer über vier Jahre laufenden Feldstudie wurde untersucht, ob durch das Einarbeiten von Keimungsstimulatoren das Auflaufen von Unkräutern beschleunigt werden kann. Zu die‐sem Zweck wurden Natriumazid (4, 5–36 kg azid ha−1), Ammoniumnitrat (34–67 kg nitrat ha−1) und Butylat (0, 2–0, 4 kg ai ha−1) verwendet. Natriumazid war in allen Versuchen das am regelmässigsten wirksame Auflaufstimulans für die an den verschiedenen Standorten vorkommenden Unkräuter, wobei die höchsten Applikationsraten hin und wieder das Auflaufen hemmten. Applikationen von 4, 5 kg azid ha−1 Natriumazid im September erhöhten die Auflaufrate regelmässig; sie wurde in drei Vegetations‐perioden bei grasartigen und breitblätt...

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Abstract. Nastic responses in bean plants (Phaseolus vulgaris L. var. Black Valentine) occur rapidly when very low ooncentrations of picloram (4-amino-3,5,6-trichloropicolinic acid) are applied to the root systems. The distribution of pioloram associated with nastic responses was quantitatively determined in root-treated plants.Sixty-seven micrograms of 14C-labeled picloram and 72 sg of unlabeled picloram in 300 ml of nutrient solution were applied to roots of 9-day old bean plants growing in an environmental growth chamber at 240 and 56 % relative humidity. Plants were removed from the treatment solution after uptake periods of 3, 6, and 11 hr. Sections were excised from 10 locations on each plant and 14C content was determined by liquid scintillation techniques. As a qualitative indication of picloram mobility, additional plants were treated for 3 hr and subjected to autoradiographic analysis.The accumulation of picloram within various parts of the plant increased with treatment time. After 3 hr of picloram uptake, a curvature of 60 to 80°from vertical in the upper 50 to 60 mm of stem corresponded to an accumulation in that part of the plant of 0.300 (second internode sample) to 1.065 (terminal bud sample) ng of picloram per mg fresh weight. The appearance of hyponasty in the trifoliolate leaflets after 6 hr of treatment corresponded to a picloram concentration in the leaf of 0.803 to 0.855 ng per mg fresh weight.As evidenced by the 14C count data, the translocation of picloram from the roots to the apical part of the plant was very rapid. Picloram was preferentially accumulated in the terminal bud and first trifoliolate leaflets. Very little picloram was transported to the primary leaves and only at the longer treatment periods. Autoradiographs of plants treated for 3 hr showed a qualitatively similar distribution of ;4C in the plant.The herbicide picloram (4-amino-3,5,6-trichloropicolinic acid) has been characterized as comparable to 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxvacetic acid (2,4,5-T) in absorption anid translocation by plants and leachability from soils, but as more effective oni many broad-leaved plants (6). Distortions in growing tissue, growth promotion in stem sections, and other morphogenetic effects caused by picloram have also been reported (4, 5,6,12 Materials and MethodsBean plants (Phaseolus vulgaris L. var. Black Valentine) were germinated in sand, transferred to aerated half-strength Hoagland and Arnon's nutrient solution (7) and grown in a controlled environment growth chamber. Uniform plants in which the first trifoliolate leaf had just opened (9 days old) were selected for use. Experiments were conducted at 24 + 0.50°56 ± 4 % relative humidity and a 16-hr photoperiod of 1460 ft-c of illumination at plant top level provided by a mixture of fluorescent and incandescent lighting.Plants were treated by immersing the root systems in foil-covered pint jars containing 300 ml of 1 ptNi picloram in half-strength nutrient solution. PLANT PHYSIOLOGY were obtaine...

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Combinations of 4-amino-3,5,6-trichloropicolinic acid (picloram) and 5-bromo-3-sec-butyl-6-methyluracil (bromacil) pellets applied to the soil gave antagonistic responses on oats(Avena sativaL. ‘Clintland 64′) with either 5.6 plus 11.2 kg/ha or 11.2 plus 11.2 kg/ha of picloram plus bromacil. In nutrient culture a significant antagonistic response occurred over a 15-day period with a picloram to bromacil ratio of 30 to 1. Of the ratios evaluated, picloram appeared to interfere with the phytotoxic effect of bromacil. The uptake of14C-bromacil alone by oats from nutrient solution was nearly double that of14C-bromacil when combined with picloram. Thin layer chromatographic analyses revealed that 47% of the14C activity from bromacil in the oat was intact bromacil and that 70% of the labeled activity from picloram was unaltered picloram. The loss of nutrient solution by evapotranspiration was less from containers with picloram and bromacil than from those with bromacil alone. Picloramtreated roots were shorter than untreated or bromacil-treated roots.