Effects of ethephon pre-treatment on the response of Elymus repens to fluazifop-butyl

Growth inhibition of pot-grown Elymus repens (L.) Gould by fluazifop-butyl was occasionally enhanced by pre-treatment with ethephon. Studies with ¹⁴C-labelled fluazifop-butyl showed that ethephon increased the accumulation of ¹⁴C in basal buds and proximal parts of the rhizome system. This potential modification in the distribution of fluazifop-butyl within E. repens rhizomes may have reduced regeneration and recovery of the E. repens, particularly from the basal buds, although there was no increase in the proportion of ¹⁴C translocated into the rhizome. Also, ethephon not only activated the sinks in the rhizome but in the foliage of E. repens as well, and could initiate buds without sinks. The effects of ethephon on fluazifop-butyl phototoxicity were irregular in their occurrence and degree, and possible reasons for this are discussed. Effets depré-traitements à I'étéphon sur la réponse de Elymus repens au fluazifop-butyl Lors d'expériences en pots, des pré-traitements & 1'étéphon augmentaient occasionnellement 1'inhibition de croissance d'Elymus repens (L.) Gould traité au fluazifop-butyl. Des etudes avec du fluazifop-butyl marqué au ¹⁴C ont montré que l'éléphon augmentait l'accumulation de ¹⁴Cdans les bourgeons de la base et dans les parties proximales des rhizomes. Bien que la proportion de ¹⁴C transportée dans le rhizome ne soit pas accrue, cette modification de la distribution du fluazifop-butyl à l'intérieur des rhizomes d'E. repens pourrait limiter la régénération et la reprise de croissance, en particulier à partir des bourgeons de la base. En outre, l'étéphon activait des puits métaboliques non seulement dans le rhizome mais aussi dans le feuillage d'E. repens et pouvait initier des bourgeons qui ne se comportaient pas comme des puits métaboliques. Tant 1'existence que 1'intensité des effets de 1'étéphon sur la phytotoxicité du fluazifop-butyl étaient irréguliers et les raisons possibles en sont discutées. Wirkung einer Vorbehandlung mit Ethephon auf die Reaktion von Elymus repens (L.) Gould auf Fluazifop-butyl In Gewächshausversuchen war die Wuchshem-mung von Elymus repens durch Fluazifop-butyl gelegentlich durch eine Vorbehandlung mil Ethephon verstärkt. Untersuchungen mil ¹⁴C-Fluazifop-butyl ergaben, daß Ethephon die Ak-kumulation von ¹⁴C in basalen Knospen und proximalen Teilen des Rhizoms förderte. Die so mögliche Veränderung der Verteilung von Fluazifop-butyl in den Quecke-Rhizomen kann zu der reduzierten Regeneration der Pflanzen geführt haben, vor allem aus den basalen Knospen, obwohl insgesamt keine groBere ¹⁴C-Menge im Rhizom gefunden wurde. Ethephon aktivierte nicht nur die Sinks im Rhizom, son-dern auch in den oberirdischen Teilen und kon-nte zur Ausbildung von Knospen ohne Sinks führen. Die Wirkungen des Ethephons auf die herbizide Wirkung des Fluazifop-butyls war unregelmaßig, und die moglichen Grunde dafiir werden diskutiert.     

Effects of repeated applications of fluazifop-butyl, haloxyfop and sethoxydim on Elymus repens in strawberries

Fluazifop-butyl, haloxyfop and sethoxydim with adjuvant oil were applied for three successive growing seasons to established strawberries infested with Elymus repens. The weed was virtually eradicated by three applications of haloxyfop (0.8 kg a.e. ha^?1) in successive years. A similar effect was given by five applications of haloxyfop (0.4 kg a.e. ha^?1) and fluazifop-butyl (1.6 kg AI ha^?1) in three growing seasons. Lower rates of haloxyfop and fluazifop-butyl, and a high rate of sethoxydim (1.6 kg AI ha^?1) applied five times were less effective, the ground cover of E. repens shoots not being reduced by the end of the experiment although weight of living rhizome was only 10-30% of that on untreated plots. Fruit yields on treated plots generally reflected the level of E. repens control, but there was some evidence of crop phytotoxicity from herbicide treatments. During the experiment E. repens untreated plots increased from about 30-100% ground cover and reduced yield 13, 28 and 68% in successive years compared with weed-free plots.     

Some factors affecting the performance of fluazifop-butyl against Elymus repens (L.) Gould (=Agropyron repens (L.) Beauv.)

In this series of glasshouse experiments, several factors influencing the foliar activity of fluazifop-butyl, butyl-2-[4-(5-trifluoromethyl-2-pyridylox-y)phenoxy] propionate, against Elymus repens (L.) Gould (=Agropyron repens(L.) Beauv.) were investigated. The growth stage of the weed even up to about 16 weeks of age was not found to be a major factor affecting the performance, if a dose of 1.0 kg ai ha^?1 is used. The activity of fluazifop-butyl was affected by low temperature, low humidity and water stress, all of which reduced the herbicide performance to varying extents. High post-treatment temperature or humidity favoured the activity of the herbicide, as measured from the regrowth ability of treated plants. Moderate water stress did not affect the activity significantly, but severe stress led to the plants becoming more tolerant of the herbicide. The effect of light/shade on foliar activity was not clear, bin showed a tendency of decreasing with increasing shade. Adverse effects of rain, probably due to wash-off of the retained spray droplets, reduced the performance of fluazifop-butyl, if rain fell within 6 h of spraying. Certains facteurs qui touchent à la performance du fluazifop-butyle contre Elymus repens (L.)Gould. (= Agropyron repens (L.) Beauv.) Cette expérimentation en serre a porté sur plusieurs facteurs qui influent sur l'activité foliaire du fluazifop-butyle, butyle-2–4-(5-trifluorométhyl-2-pyridyloxy)phénoxy proprionate, contre Elymus repens (L.) Gould (Agropyron repens (L.) Beauv.). Il en résulte que, même jusqu'à l'âge de 16 semaines, le stade végétal de l'adventice ne paraît pas jouer un rôle important dans la performance de l'herbicide à une dose de 1,0 kg ma ha^?1. L'activité du fluazifop-butyle se trouve altérée en conséquence de température faibles, d'une faible humidité et de carence d'eau; tous ces facteurs ont amené une réduction plus ou moins grande dans la performance de l'herbicide. A en juger part la croissance nouvelle des plantes traitées, une température élevée, de même qu'une forte humidité suivant l'application, favorisent l'activité herbicide. La carence d'eau n'a exercé une influence significative sur l'activité herbicide que lorsqu'elle est devenue sévère; alors les plantes ont fait preuve d'une moindre tolérance. L'influence de la lumière sur l'activité foliaire est restée imprécise mais celle-ci a eu tendance à dimineur à mesure qu'augmentait l'ombre. Les effets néfastes de la pluie, grâce sans doute au lessivage des gouttelettes retenues sur les feuilles, ont diminué l'efficacité du fluazifop-butyle lors d'une précipitation moins de 6 heures après la pulvérisation. Einflüsse auf die Wirkung von Fluazifop-butyl auf Elymus repens (L.)Gould. (= Agropyron repens (L.) Beauv.) Verschiedene Einflüsse auf die Blattwirkung von Fluazifop-butyl Butyl-2-[4-(5-trifluormethyl-2-pyridiloxy)phenoxy]propionate auf die Gemeine Quecke wurden in einer Reihe von Versuchen im Gewächshaus untersucht. Das Entwicklungsstadium des Unkrauts war auch bei bis zu 16 Wochen alten Pflanzen ohne Einfluss auf die Wirkung, solange 1,0 kgAS ha^?1 angewandt wurden. Niedrige Temperatur und Luftfeuchtigkeit sowie Wassermangel setzen die Wirkung des Herbizids, die am Wiederaustrieb gemessen wurde, herab. Hohe Temperatur und Luftfeuchtigkeit nach der Behandlung begünstigten die Wirkung. Schwacher Wassermangel beeinflusste die Wirkung nicht signifikant, aber bei starkem Wassermangel waren die Pflanzen widerstandsfähiger. Die Wirkung einer Beschattung der Pflanzen auf die Wirksamkeit des Herbizids war undeutlich, aber tendenziell zeigte sich eine Abnahme der Wirkung mit Zunahme der Beschattung. Regen innerhalb 6 Stunden nach der Behandlung verminderte die Wirkung von Ftuazifop-butyl, vermutlich wegen des Abwaschens des Spritzbelags von den Blättern.     

Effects of fluazifop-butyl on shoot growth and rhizome buds of Elymus repens (L.) Gould

A series of glasshouse experiments was conducted to evaluate the activity of fluazifop-butyl, butyl 2-[4-(5-trifluoromethyl-2-pyridyloxy)phenoxy] propionate, against Elymus repens. Foliar applications of doses 0·25–1·0 kg ha^?1 consistently gave better control than did soil applications. The most obvious phytotoxic symptoms were chlorosis and necrosis, beginning with the youngest leaves 5–6 days after spraying, which spread to all leaves within 2 weeks. Translocation was measured by defoliating plants at different times after spraying and assessing regrowth and by evaluating rhizome-bud viability. At low doses (0·125 and 0·25 kg ha^?1) translocation to rhizomes occurred mainly between 6 and 48 h. When fluazifop-butyl was sprayed at a dose range of 0·125–1·0 kg ha^?1, at least 90% of the rhizome buds had accumulated a lethal dose within 72 h of spraying. In another experiment, with a dose of 0·25 kg ha^?1, 31, 72 and 92% of rhizome buds were found to be non-viable when sampled 2, 24 and 48 h respectively after spraying. At 1·0 kg ha^?1 all the buds had accumulated sufficient herbicide to prevent sprouting 48 h after spraying.     

Influence of environmental factors on the performance of sethoxydim against Elymus repens (L.)

The performance of sethoxydim on Elymus repens (L.) Gould was studied under contrasting levels of humidity, light intensity, temperature, soil moisture and simulated rainfall using controlled environment chambers. Over a 24-h post-spraying period, increases in humidity and temperature markedly enhanced herbicide performance, while effects of light intensity were less pronounced. Soil moisture deficit significantly reduced herbicide performance, but there were no adverse effects of wet soil conditions (twice field capacity) on activity. The effects of simulated rain depended upon herbicide dosage, time interval between spraying and the onset of rain, and rain intensity. A low rain intensity of 0.5 mm h^?1 did not reduce herbicide performance even when applied 10 min after spraying. The longer term studies, over 4 weeks, showed increases in herbicide activity with higher temperatures but lower light intensities.     

Influence of light, temperature and humidity on the translocation and activity of glyphosate in Elymus repens (=Agropyron repens)

The effects of light, température and humidity on the performance and translocation of glyphosate in Elymus repens (L.) Gould (=Agropyron repens L. (Beauv.)), during the period of 48 h after treatment, were studied in controlled-environment cabinets. Increases in the levels of all three factors resulted in increases in herbicide performance. In general, these differences were statistically significant at all treatment periods except the longest when almost full control was achieved. The results highlight the important influence of environmental factors on herbicide performance during the short-term, post-spraying period. The application of ¹⁴C-labelled glyphosate to the adaxial leaf-sheath surface resulted in very rapid uptake and was used as a method of treating plants to study herbicide translocation under different environmental conditions. Increased light levels and temperatures enhanced basipetal translocation to the crowns and rhizomes but increased humidity had no significant effect with this form of application.     

Effect of fluazifop-butyl on the chlorophyll content, fluorescence and chloroplast ultrastructure of Elymus repens (L.) Gould. leaves

Some aspects of the action of fluazifop-butyl on the chlorophyll content, chloroplast functioning and chloroplast ultrastructure of Elymus repens are reported. Over a period of 0–12 days after spraying with 0.25 or 1.0 kg ha^?1 of the herbicide, chlorophyll a and b contents of this susceptible plant decreased, progressing from the youngest to the more mature leaves. Newly formed tillers and the youngest expanding leaves exhibited a more severe type of chlorosis and were often found to be devoid of chlorophyll. A similar progressive decline of the chlorophyll content was observed in an experiment where leaf segments were floated in fluazifop-butyl. Evidence of a rapid and significant alteration of the normal chlorophyll fluorescence of E. repens leaves treated with fluazifopbutyl was obtained. The herbicide, at a concentration range of 0.25–1.0 μg μ1^?1, caused a significant loss of the fast fluorescence rise, fluorescence yield and, after 24 h, caused a total abolition of the fluorescence decay (PS decas). These results are discussed. Ultrastructural damage to chloroplasts was seen within 24 h after treatment with fluazifop-butyl. This damage ranged from a partial to total disruption of the outer chloroplast envelope and a disorganization of the internal thylakoid system. Such Ultrastructural effects on chloroplasts were found to intensify up to about 6–7 days after spraying, by which time nearly all chloroplasts in tissue sections were affected to some degree.     

The uptake,translocation and metabolism of epronaz in selected species

The absorption, translocation and metabolism of the selective pre- or early post- emergence herbicide epronaz (N-ethyl-N-propyl-3-propylsulphonyl-1,2,4-triazole-1-carboxamide) were investigated using selected crop and weed species. The pattern of tolerance to epronaz of both germinating seeds and 10-day-old plants grown in nutrient solution, was found to be soybean (Glycine max L.) > maize (Zea mays L.) > cotton (Gossypium hirsutum L.) > rice (Oryza sativa L.) > barnyard grass [Echinochloa crus-galli (L.) Beauv.]. In all species, absorption and translocation of ¹⁴C from a nutrient solution containing [¹⁴C]epronaz (0.02 μCi ml^?1) increased with time. Autoradiographic and liquid scintillation analysis indicated the presence of radioactivity in the apical regions of all species after 4 h. Interspecies variation in uptake and distribution did not appear to be a major factor explaining selectivity, although the resistance of cotton may be partly due to compartmentalisation of ¹⁴C in the lysigenous glands in stem and leaves. Analysis of extracts from plants treated with [¹⁴C]epronaz indicated the presence of epronaz, its major degradation product [3-propylsulphonyl-l,2,4-triazole (BTS 28 768)] and certain unknown radio-labelled compounds. The major metabolite (Unknown I) was believed to be a conjugate of certain plant components with either epronaz or BTS 28 768. The rate of formation of Unknown I corresponded to the relative resistance and susceptibility to epronaz of soybean, rice and barnyardgrass. The level of the herbicide remained much higher in cotton than in the other species, possibly reflecting compartmentalisation and inactivation of epronaz in the lysigenous glands. For maize, high levels of uptake, exudation and degradation in the nutrient solution were recorded.     

Translocation, metabolism and residues of fluazifop-butyl in soybean plants

Translocation of fluazifop-butyl in soybean plants and hydrolysis of the ester to fluazifop-acid were investigated in a field experiment. The herbicide was translocated rapidly from the leaves to the roots, but the concentration in the leaves remained about 10-fold higher than that in the roots. Rapid hydrolysis of fluazifop-butyl to fluazifop-acid was observed, and residues of the metabolite were found to persist much longer in the plant than the active compound. Increased temperatures resulted in more rapid hydrolysis. No traces of active compound or of its main metabolite were found in the seeds after harvest. A reversed-phase HPLC method for simultaneous détérmination of fluazifop-butyl and fluazifop-acid residues in soybean plants was developed. Transport, metabolisme et residus du fluazifop-butyl chez les plantes de soja Le transport du fluazifop-butyl dans les plantes de soja et l'hydrolyse de Tester en fluazifop-acide ont étéétudiés dans une experimentation de plein champ. L'herbicide a été vehiculé rapidement des feuilles vers les racines, mais la concentration dans les feuilles est demeurée 10 fois plus haute que celle dans les racines. Une hydrolyse rapide de la forme ester en acide a été observee, et les residus du metabolite se sont reveles beaucoup plus persistants dans la plante que le composé actif. Une augmentation des températures a accéléré l'hydrolyse. Aucunes traces de la matière active ou de son principal métabolite n'ont été trouvées dans les graines après la récolte. Une methode HPLC en phase inverse pour la détérmination simultanée des residus de fluazifop-butyl et de fluazifop-acide chez le soja a été développée. Translokation, Metabolismus und Ruckstande von Fluazifop-butyl in Sojabohnen-Pflanzen Die Translokation von Fluazifop-butyl in Sojabohnen-Pflanzen und die Hydrolyse des Esters zu Fluazifop-Saure wurden in einem Freilandversuch untersucht. Das Herbizid wurde von den Blattern in die Wurzein schnell transloziert, doch in den Blattern blieb die Konzentration etwa 10mal großer als in den Wurzein. Es wurde eine schnelle Hydrolyse des Fluazifop-butyls zu Fluazifop-Saure beob-achtet, und die Ruckstande des Metaboliten in den Pflanzen erwiesen sich als viel bestandiger als der Wirkstoff. Bei hoheren Temperaturen lief die Hydrolyse schneller ab. In den Samen wurden nach der Ernte keine Ruckstande des Wirkstoffs oder seiner Hauptmetaboliten gefunden. Eine Reversed-Phase-HPLC-Methode zur gleichzeitigen Bestimmung von Ruckstanden von Fluazifop-butyl und Fluazifop-Saure in Sojabohnen-Pflanzen wurde entwickelt.     

The uptake, translocation and metabolism of dichlobenil in selected aquatic species

The mode of action of dichlobenil (2.6-dichlorobenzonitrile) was investigated using three species of aquatic weeds, namely: water-cress (Rorippa nasturtium-aquaticum L. Hayek), narrow-leaved water parsnip (Berula erecta, Huds. Coville) and reed-grass (Phragmites communtis Trin.). An attempt was made to relate the selective activity of dichlobenil to differences in the absorption, translocation, evaporation and metabolism of the herbicide. B. erecta was found to be resistant to dichlobenil while P. communis was susceptible and R. nasturtium-aquaticum moderately susceptible. Ten days after root treatment of the species with 5 ppm ¹⁴C-dichlobenil in a vapour-trapping device, the amount of ¹⁴C absorbed and translocated by P. communis was approximately 4-6 times greater than that for B. erecta and R. nasturtium-aquaticum. the loss of ¹⁴C-dichlobenil vapour from the leaves of R. nasturtium-aquaticum was 6-11 times greater than with the other two species. The distribution of radioactivity in the roots, stems and vapour of R. nasturtium-aquaticum was uniform though movement of ¹⁴C from the roots appeared to be restricted in B. erecta; in the case P. communis the ¹⁴C accumulated to the highest degree in the stems (rhizomes) and leave. An initial lag phase of 24-28 h was evident in the rates of loss of ¹⁴C-dichlobenil vapour from the leaves of R. nasturtium-aquaticum and P. communis but the rate of loss from the leaves of B. erecta was uniformly low. After ¹⁴C-dichlobenil lost as vapour from the leaves was taken into account the highest concentration of radioactivity in leaves was recorded for P. communis, and the highest stem/root concentration for B. erecta: the highest loss of ¹⁴C-dichlobenil vapour from the leaves was noted for R. nasturtium-aquaticum. While the loss of ¹⁴C-dichlobenil vapour from the leaves significantly reduced the in vivo concentration (μg/g dry weight) of the herbicide in the leaves of each species, the balance between ¹⁴C-dichlobenil and its ethanol-soluble and ethanol-insoluble metabolites in the leaves was only affected significantly in the case of R. nasturtium-aquaticum. Qualitative examination of the ethnol-soluble metabolites produced by each species indicated that they consisted, in part, of the phenolic derivatives of ¹⁴C-dichlobenil and their conjugates. The major proportion of the metabolites was, however, unidentified. Absorption, migration et métabolisme du dichlobénil dans quelques espèces aquatiques Le mode d'action du dichlobénil (2.6-dichlorobenzonitrile) a étéétudié en utilisant trios espéces de mauvaises herbes aquatiques: du cresson de fontaine (Roripa nasturtium-aquaticum) L. Hayek). de la berle (Berula erecta. Huds. Coville) et du roseau commun (Phragmites communis Trin.). Les auteurs ont tenté d'établir ne relation entre l'activité sélectíve du dichlobénil et des differences dans l'absorption, la migration, l'évaporation et le métabolisme de l'herbicide II a été constaté que B. erectaétait résistante au dicholbénil, alors que P. communisétait sensible et R. nasturtium-aquaticum modérément sensible. Dix jours aprés le traitement des racínes de ces espéces avec 5 ppm de ¹⁴C-dichlobénil dans un dispositif á captage de vapeur, la quntitié de ¹⁴C absorbée et transportée chez P. communisétait environ 4 á 6 fois plus grande que chez B. erecta et R. nasturtium-aquaticum: la perte de ¹⁴C dichlobénil sous forme de vapeur par les feuilles de R. nasturtium-aquaticum a été 6 á 11 fois plus élevée que pour les deux autres espéces. La distribution de la radio-activité dans les raciness, les tiges et les feuilles de R. nasturtium-aquaticum a été uniforme alors que la migration de ¹⁴C depuis les racines est apparue réduite chez B. erecta: le cas de P. communis, le ¹⁴C s'est accumulé au plus haut degré dans les tiges (rhizomes) et les feuilles. Une phase initiale de retard de 24 h á 48 h s'est manifestée dans les taux de perte de vapeur de ¹⁴C-dichlobénil par les feuilles de R. nasturtium-aquaticum et de P. communis mais le taux de perte par les feuilles chez B. erectaété uniformément bas. Aprés avoir tenu compte des pertes de ¹⁴C-dichlobénil sous frome de vapeur par les feuilles, la concentration de radio-activité la plus forte dans les feuilles a été relevée chez P. communis et la plus forte concentration dans les tiges et les raciness chez B. erecta: la perte la plus élevé de ¹⁴C-dichlobénil sous forme de vapeur par les feuilles a été notée chez R. nasturtium-aquaticum. Alors que perte de ¹⁴C-dichlobénil sous forme de vapeur par les feuilles a significativement réduit la concentration in vivo en μg/g de poids sec, de l'herbicide dans les feuilles de chacune des espéces, la balance dans les feuilles, entre le ¹⁴C-dichlobénil et ses métabolites solubles ou insolubles dans l'éthanol a été affectée significativement seulement dans le cas de R. nasturtium-aquaticum. L'examen qualitative des métabolites solubles dans l'éthanol produits par chaque espéce a montré qu'ils étaient constitués en partie par des dérivés phénoliques du ¹⁴-C dichlobénil et par leurs composés d'addition. La plus grande partie de ces métabolites n'ont toutefois pas pu être identifiés. Aufnahme, Translokation und Metabolismus von Dichlobenil bei ausgewählten Wasserpflanzen. Unter Verwendung dreier Arten von Wasserunkräutern, nämlich Rorippa nasturtium-aquaticum (L.) Hayek. Berula erecta Huds. Coville und Phargmites communis Trin., wurden Untersuchungen zum Wirkungsmechanismus von Dichlobenil (2.6-Dechlorbenzonitril) angestellt. Es wurde vesucht, die selective Wirkung von Dichlobenil mit Unterschieden in Absorption, Translokation, Verdampfung und Metabolismus des Herbizids in Beziehung zu bringen. B. erecta erwies sich als resistant gegen Dichlobenil, während P. communis empfindlich und R. nasturtium-aquaticum mässig empfindlich waren. Zehn Tage nach einer Wurzelbehandlung der Pflanzen mit 5 ppm ¹⁴C-Dichlobenil in einer Apparatur, die mit einer Absorptionsvorrichtung für Dämpfe vesehen war, war die von P. communis absorbierte und translozierte Menge an ¹⁴C etwa 4-6 mal grösser als bei B. erecta und R. nasturatium-aquaticum; die über die Blätter in Dampfform abgegebene Menge an ¹⁴C-Dichlobenil war bei R. nasturtium-aquaticum 6-11 mal grösser als bei den beiden anderen Arten. Bei R. nasturtium-aquaticum war die Radioaktivität auf Wurzel. Stengel und Dampfhase gleichmässig veteilt; bei B. erecta hingegen schien der Abtransport von ¹⁴C aus Wurzeln gehemmt zu sein; bei P. communis war das meiste ¹⁴C in Stengeln (Rhizomen) und Blättern angereichert. Bei der Abgabe von dampfförmigem ¹⁴C-Dichlobenil aus den Blättern trat bei R. nasturtium-aquaticum und P. communis zu Anfang eine lag-Phase von 24-28 h auf, dagengen war bei B. erecta die Verdamp-fungsrate aus den Blättern gleichmlässig niedrig. Unter Berücksichtigung des Verlustes an ¹⁴C-Dichlobenil, das in Damofform über das Blattwerk abgegeben worden war, wurde die höchste Konzentration an Radioaktivität in den Blättern bei P. communis und die höchste Konzentration in Stengel und Wurzel bei B. erecta festgestellt; der höchste Verdampfungsverlust an ¹⁴C-Dichlobenil via Blattwerk wurde bei R. nasturtium-aquaticum gefunden. Während durch den Verlust an dampfförmig über das Blattwerk augeschiedenem ¹⁴C-Dichlobenil die in vivo-Konzentration (μg/g Trgw.) des Herbizids in den Blättern aller Pflanzenarten significant verringert wurde, wurde das Verhältnis von ¹⁴C-Dichlobenil und scinen in Äthanol löslichen und unlöslichen Metaboliten nur bei R. nasturtium-aquaticum deutlich beeinflusst. Eine qualitative Untesuchung der in den einzelnen Pflanzenarten entstandenen äthanollöslichen Metaboliten deutet darauf hin, dass es sich bein ihnen um die phenolischen Derivate von ¹⁴C-Dichlobenil und ihre Konjugate handelte. Der grössere Teil der Metaboliten wurde jedoch nicht identifiziert.     

Modelling the effects of Elymus repens (L.) Gould competition on yield of cereals, peas and oilseed rape

Effects of Elymus repens (L.) Gould competition on yield of winter rye (Secale cereale L.), winter wheat (Triticum aestivum L.), spring barley (Hordeum vulgare L.), peas (Pisum sativum L.), and spring oilseed rape (Brassica napus L.) were studied in field trials conducted on the same location through 3 years. The competitiveness of the five crops against E. repens could be ranked as follows, with the most competitive crop mentioned first: rye wheat, barley rape, peas. Yield losses ranged from 8% in rye to around 35% in peas and rape at a density level of 100 primary shoots m^?2 in spring. The different prevailing climatic conditions in the growing seasons had no effect on the yield-density relationships in rye, peas, and barley, whereas significant interactions were found in wheat and rape. The cumulative emergence patternsof primary shoots were described in the spring-sown crops, and models were derived to simulate the sensitivity of competition parameters to the actual time of shoot recording. The importance of choosing the right time for shoot emergence counts in relation to threshold recommendations and other aspects is discussed. Modélisation de l'effet de la concurrence de Elymus repens (L.) Gould sur les rendements de céréales, de pois et de colza Nous avons étudié au champ les effets de la concurrence de Elymus repens (L.) Gould sur le rendement du seigle d'hiver (Secale cereale L.), du blé d'hiver (Triticum aestivum L.), de l'orge de printemps (Hordeum vulgare L.), du pois (Pisum sativum L.) et du colza de printemps (Brassica napus L.). Les essais ont été conduits durant trois ans sur le même site. L'aptitude à la concurrence des cinq cultures à l'égard de E. repens peut être classée ainsi, en ordre décroissant: seigle blé et orge colza et pois. Les pertes de rendement allaient de 8% chez le seigle à environ 35% chez le pois et le colza, à un densité de pousses primaires 100 m^?2, mesurée au printemps. Les différentes conditions météorologiques ayant régné lors des périodes de croissance n'ont eu aucun effet sur les relations densité-rendement chez le seigle, le pois et l'orge, alors que des interactions significatives ont été observées chez le blé et le colza. Le patron cumulatif de l'émergence des pousses primaires a été décrit pour les cultures de printemps, et des mode les en ont été déduits pour simuler la sensibilité des paramètres de concurrence à la date à laquelle les levées sont enregistrées. L'importance est discutée du choix d'une date correcte pour les comptages de levées dans l'optique de recommandations de seuils de densité. Modellierung der Wirkung der Konkurrenz von Elymus repens (L.) Gould auf den Ertrag von Getreide, Erbse und Raps Die Wirkung der Konkurrenz der Gemeinen Quecke (Elymus repens) auf Winterroggen (Secale cereale L.), Winterweizen (Triticum aestivum L.) Sommergerste (Hordeum vulgare L.), Saat-Erbse (Pisum sativum L.) und Sommerraps (Brassica napus L.) wurde in Feldversuchen über drei Vegetationsperioden am selben Ort untersucht. Für die Konkurrenzkraft der fünf Kulturen gegenüber der Quecke ergab sich folgende Reihenfolge: Roggen Weizen, Gerste Raps, Erbse. Die Ertragsverluste lagen bei einer Dichte von 100 Queckenhalmen m² im Frühjahr zwischen 8 % beim Roggen und rund 35 % bei Erbse und Raps. Die verschiedenen Witterungsbedingungen in den Versuchsjahren blieben ohne Einfluß auf die Ertrags-Dichte-Beziehungen bei Roggen, Erbse und Gerste, während bei Weizen und Raps eine signifikante Beeinflussung gefunden wurde. Das Austriebsverhalten der Queckentriebe wurde in den Sommerkulturen festgehalten, und es wurden Modelle entwickelt, um die Empfindlichkeit der Konkurrenzparameter in Abhängigkeit vom Zeitpunkt der Zählung der Triebe zu simulieren. Die Bedeutung der Wahl des richtigen Zeitpunkts für die Erfassung des Austriebs der Quecke hinsichtlich der Empfehlung von Schwellenwerten und anderen Aspekten wird diskutiert.     

The impact of uptake, translocation and metabolism on the differential selectivity between blackgrass and wheat for the herbicide pyroxsulam

BACKGROUND: Wheat shows selectivity to pyroxsulam, a new broad‐spectrum herbicide with high activity on blackgrass. Studies were performed to establish whether uptake, translocation or metabolism were responsible for the differential activity in wheat compared with blackgrass. In addition, the effect of the safener cloquintocet‐mexyl on metabolism was evaluated in wheat and blackgrass shoots. RESULTS: Root uptake of pyroxsulam in blackgrass was significantly higher than in wheat, suggesting a possible activity enhancement in blackgrass owing to root uptake. Translocation to foliage from root uptake as well as translocation out of treated foliage following foliar applications was low in wheat compared with blackgrass, likely owing to the rapid metabolism of pyroxsulam in wheat. Wheat metabolized pyroxsulam significantly faster than blackgrass to the less active O‐dealkylation product. Wheat shoots metabolized pyroxsulam faster when the safener cloquintocet‐mexyl was present, but cloquintocet‐mexyl did not increase the rate of metabolism in blackgrass. CONCLUSIONS: The selectivity of pyroxsulam to wheat relative to blackgrass was connected primarily with differences in the rate of metabolism and generation of an inactive metabolite. Metabolism in wheat restricted subsequent movement of radioactivity out of the treated leaf. The rapid metabolism in wheat was increased by the addition of cloquintocet‐mexyl. Copyright © 2010 Society of Chemical Industry     

Safener effects on acetochlor toxicity, uptake, metabolism and glutathione S-transferase activity in maize

The effect of five herbicide safeners on preventing maize (Zea mays L.) injury by acetochlor [N-(2-ethyl-6-methyl-phenyl)-N-(ethoxymethyl)-chloroacetamide], their influence on herbicide uptake and metabolism to a glutathione (GSH) conjugate as well as on GSH content and glutathione S-transferase activity (GST) in untreated and herbicide with/without safener-pre-treated 4-day-old seedlings were determined. The safeners studied were: AD-67 (N-di-chloroacetyl-1-oxa-4-azaspiro-4-5-decane), BAS-145138 [1-dichloroacetyl-hexahydro-3,3,8a-trimethyl-pyrrolo(l,2-a)pyrimidin-6(2H)-one], dichlormid (N, A,-diallyl-2,2-dichlo-roacetamide), DKA-24 (N, N²-diallyl-N²dichloroacetylglycineamide) and MG-191 (2-dichloromethyl-2-methyl-1,3-dioxolane). All safeners significantly increased [¹⁴C]acetochlor uptake and metabolism rate, maize GSH content and GST activity. Seedlings receiving BAS-145138 pre-treatment metabolized almost 70% of the absorbed [¹⁴C]acetochlor within 10 min. Safener-enhanced GST activity was always found to be higher when [¹⁴C]acetochlor was used as the substrate compared with CDNB (1-chloro-2,4-dinitrobenzene). Although DKA-24 had a significantly lower influence on both herbicide metabolism and GST activity, it was nearly as effective a safener as BAS-145138, while the others provided no or poor protection to maize from acetochlor injury when they were not incorporated in the soil. Effets d'antidotes sur la toxicité, la pénétration et le métabolisme de I'acétochlore chez le mats etsur l'activité glutathion S-transférase Cinq antidotes d'herbicides diminuaient la toxicité de 1'acétochlore [N-(2-éthyl-6-méthyl-phényl)-N-(éthoxyméthyl)-chloroacétamide] à I'égard du maïs (Zea mays L.). Lew effet sur l'absorption de l'herbicide et sur son métabolisme en un conjugué avec le glutathion (GSH), de même que leur effet sur la teneur en GSH et 1'activité glutathion 5-transférase (GST) ont étéétudiés sur des maïs âgés de 4 jours. Les antidotes étaient: l'AD-67 (N-dichloroacétyl-1-oxa-4-azaspiro-4,5-décane), le BAS-145138 [1 -dichloroacétyl-hexahydro-3,3,8a-triméthyl-pyrrolo(l,2-a) pyrimidine-6(2H)-one], le di-chlormide (N, N-diallyl-2,2-dichloracétamide), le DKA-24 (N, N²-diallyl-N²-dichloracétylgly-cineamide] et le MG-191 (2-dichlorométhyl-2-méthyl-l,3-dioxolane). Tous les antidotes augmentaient de manière significative 1'absorption et le métabolisme de I'acétochlore ¹⁴C, ainsi que la teneur du maïs en GSH et son activité GST. Les jeunes plantes prétraitées avec le BAS-145138 métabolisaient en 10 min près de 70% de I'acétochlore ¹⁴C absorbé. L'activité GST stimulée par 1'antidote était toujours plus élevée avec I'acétochlore ¹⁴C comme substrat qu'avec le CDNB (1-chloro-2,4-dinitrobenzène). Le DKA-24 avait un effet significativement plus faible que le BAS-145138 sur le métabolisme de l'herbicide et sur l'activité GSH, mais son action antidote était presque aussi importante. Les autres produits n'apportaient au maïs qu'une protection faible ou nulle contre l'acétochlore quand ils n'étaient pas incorporés au sol. Wirkung von Safenern auf die Phytotoxizität, Aufnahme und Metabolismus von Acetochlor und die Glutathion-S-Transferase-Aktivität in Mais Die Wirkung von 5 Safenern (AD-67, BAS-145138, Dichlormid, DKA-24 und MG-191; chemische Bezeichnungen s.o.) auf die Phytotoxizität von Acetochlor für Mais (Zea mays L.) und ihr Einfluß auf die Aufnahme des Herbizids und Metabolismus zu einem Glutathion-(GSH-) Konjugat und auf die Glutathion-S-Transferase-(GST-)Aktivität wurde an 4 Tage alten Keimpflanzen untersucht. Durch die Vorbehandlung mit den Safenern wurden die [¹⁴C]-Acetochlor-Aufnahme- und -Metabolierungsrate, der GSH-Gehalt und die GST-Ak-tivität signifikant erhöht. Mit BAS-145138 vorbehandelte Keimpflanzen metabolisierten fast 70% des absorbierten [¹⁴C]-Acetochlor innerhalb von 10 min. Die durch die Safener erhöhte GST-Aktivität bei [¹⁴C]-Acetochlor als Substrat war im Vergleich zu Chlordinitroben-zen immer höher. Obwohl DKA-24 einen signifikant geringeren Einfluß sowohl auf den Herbizidmetabolismus als auch auf die GST-Aktivität hatte, war es fast so wirkungsvoll wie BAS-145138, während die anderen ohne Einarbeitung in den Boden für den Mais keinen oder geringen Schutz gegen Schäden durch Acetochlor boten.     

Absorption,translocation and metabolism of the herbicide naproanilide in tobacco

Naproanilide [2-(2-naphthyloxy)propionanilide] has a high activity against dicotyledonous weeds in rice fields, but is very safe to rice. This study was designed to clarify the absorption and translocation of radiolabelled naproanilide in tobacco plants and the metabolism in tobacco callus. The results indicated that naproanilide is translocated easily to the upper part of tobacco plants. Distribution of radioactivity in tobacco plants at the 7th day was shown to be 0.88, 0.24 and 0.03%, and at the 14th day 1.71, 1.86 and 2.32% of the total activities of [¹⁴C]naproanilide in root, stem and leaf, respectively. When compared to earlier results obtained with rice, the translocation rate in tobacco is much higher and might therefore contribute a possible mechanism of herbicidal selectivity. Metabolites including NOP [2-(2-naphthyloxy)propionic acid], NOPM [methyl 2-(2-naphthyloxy)propionate], 2-naphthol, 2,3-naphthalenediol, 2,6-naphthalenediol, 2,7-naphthalenediol and 2-hydroxy-1,4-naphthoquinone were identified in tobacco callus by co-chromatography.     

作物从土壤中吸收、传递和累积农药的研究进展

农药是保障粮食安全的重要农业投入品,施用后部分农药会沉积在土壤中,甚至会被作物根部吸收,进入作物体内并累积于可食部位,从而导致潜在农产品质量安全问题。研究表明,土壤中的有机质含量、农药的辛醇-水分配系数和作物脂质含量是影响作物吸收非离子型农药的关键因素,作物各部位的脂质含量是影响该类农药累积的关键因素,借助蒸腾作用向上传递是作物根部吸收传导农药的主要动力。本文重点综述了农药被作物的根部吸收、传递和累积及其主要影响因素,结合植物吸收模型的发展及运用,展望了该领域未来发展方向,为农药归趋及应用风险研究提供参考。     

Seasonal restrictions of bud growth on roots of Cirsium arvense and Sonchus arvensis and rhizomes of Elymus repens

Brandsæter LO, Fogelfors H, Fykse H, Graglia E, Jensen RK, Melander B, Salonen J & Vanhala P (2010). Seasonal restrictions of bud growth on roots of Cirsium arvense and Sonchus arvensis and rhizomes of Elymus repens. Weed Research 50 , 102–109.

Summary

The success of weed management aimed at depleting the regenerative structures of perennial weeds depends largely on the sprouting activity of rhizome and root buds. Seasonal variation in sprouting of these buds on Cirsium arvense, Sonchus arvensis and Elymus repens was studied for plants collected from Denmark, Finland, Norway and Sweden. At 2‐week intervals from July to October, 5‐cm fragments of roots or rhizomes were cut from plants grown in buckets and planted into soil in pots, half of which were placed immediately into growth chambers at 18°C for 4 weeks. The other half of the pots were initially placed in a dark room at 2°C for 4 weeks before being transferred to the same growth chamber, also for 4 weeks. During the growth chamber period, the numbers of emerged shoots in each pot were counted weekly. The sprouting activity of C. arvense and E. repens was relatively uniform during this period and bud dormancy was not apparent. In all ecotypes of S. arvensis, innate bud dormancy developed during the latter part of the growing season. For all three species, differences in sprouting readiness were found among ecotypes. The results imply that C. arvense and E. repens are more likely to be controlled by mechanical measures in autumn than S. arvensis.     

Absorption, translocation and metabolism of metamitron in Chenopodium album

BACKGROUND: In recent years, common lambsquarters (Chenopodium album L.) populations from sugar beet fields in different European countries have responded as resistant to the as‐triazinone metamitron. The populations have been found to have the same D1 point mutation as known for atrazine‐resistant biotypes (Ser₂₆₄ to Gly). However, pot experiments revealed that metamitron resistance is not as clear‐cut as observed with triazine resistance in the past. The objectives of this study were to clarify the absorption, translocation and metabolic fate of metamitron in C. album. RESULTS: Root absorption and foliar absorption experiments showed minor differences in absorption, translocation and metabolism of metamitron between the susceptible and resistant C. album populations. A rapid metabolism in the C. album populations was observed when metamitron was absorbed by the roots. The primary products of metamitron metabolism were identified as deamino‐metamitron and metamitron‐N‐glucoside. PABA, known to inhibit the deamination of metribuzin, did not alter the metabolism of metamitron, and nor did the cytochrome P450 inhibitor PBO. However, inhibition of metamitron metabolism in the presence of the cytochrome P450 inhibitor ABT was demonstrated. CONCLUSION: Metamitron metabolism in C. album may act as a basic tolerance mechanism, which can be important in circumstances favouring this degradation pathway. Copyright © 2011 Society of Chemical Industry     

五种杀菌剂在水稻上的吸收与传导性能研究

茎叶喷雾是当前化学农药最常用的施药方式,但是存在着农药蒸发飘移、弹跳碎裂、因过度铺展而脱靶流失等缺陷,导致农药利用率低。通过研究农药在植物体内的吸收及传导性能,选择合适的农药研发根部施药的剂型与技术,能够降低环境因素对农药有效成分的不利影响,并通过农药的缓慢释放与剂量调控维持更长时间的药效,从而有效提高农药利用率。本研究以室内营养土和营养液两种模式培育的水稻为模式作物,研究了三环唑、噻呋酰胺、己唑醇、氟环唑和嘧菌酯5种不同类型的杀菌剂在水稻苗期植株中的吸收与传导行为。结果表明,这5种杀菌剂均可以被水稻幼苗根系吸收并向上传导,但效率存在差异。在营养土和营养液培养条件下,水稻幼苗根部的三环唑含量在4 h~2 d内明显高于茎叶部,施药5 d后三环唑在水稻中的转运因子值均大于1,说明三环唑具有良好的向上传输性能,而其他农药向上传输的能力较差。相比其他4种农药,三环唑更适合加工成根部施用的剂型,更易于通过水稻根部吸收后向上传输与分布,以有效防控茎叶部病害。该结果可为根部施用的药剂研发提供思路,为农药根部施药技术的发展提供指导。     

Control of Elymus repens by rhizome fragmentation and repeated mowing in a newly established white clover sward

Control of perennial weeds, such as Elymus repens, generally requires herbicides or intensive tillage. Alternative methods, such as mowing and competition from subsidiary crops, provide less efficient control. Fragmenting the rhizomes, with minimal soil disturbance and damage to the main crop, could potentially increase the efficacy and consistency of such control methods. This study's aim was to investigate whether fragmenting the rhizomes and mowing enhance the control of E. repens in a white clover sward. Six field experiments were conducted in 2012 and 2013 in Uppsala, Sweden, and Ås, Norway. The effect of cutting slits in the soil using a flat spade in a 10 × 10 cm or 20 × 20 cm grid and the effect of repeated mowing were investigated. Treatments were performed either during summer in a spring‐sown white clover sward (three experiments) or during autumn, post‐cereal harvest, in an under‐sown white clover sward (three experiments). When performed in autumn, rhizome fragmentation and mowing reduced E. repens shoot biomass, but not rhizome biomass or shoot number. In contrast, when performed in early summer, rhizome fragmentation also reduced the E. repens rhizome biomass by up to 60%, and repeated mowing reduced it by up to 95%. The combination of the two factors appeared to be additive. Seasonal differences in treatment effects may be due to rhizomes having fewer stored resources in spring than in early autumn. We conclude that rhizome fragmentation in a growing white clover sward could reduce the amount of E. repens rhizomes and that repeated mowing is an effective control method, but that great seasonal variation exists.     

Uptake,translocation and metabolism of the herbicide molinate in tobacco and rice

Molinate, a selective herbicide, is used for the control of annual and perennial weeds in rice paddy fields. This study was designed to assess the basis of the selective action of molinate between a susceptible broadleaf crop, tobacco, and a resistant graminaceous plant, rice. Experiments were conducted comparing plant growth under different concentrations of molinate, determining the absorption and translocation of the herbicide in the plant and identifying the metabolites in suspension cells. Rice showed greater tolerance to molinate than tobacco. Leaves of tobacco showed retarded and distorted growth at 10 mg liter^-1 of molinate 14 days after treatment, but rice leaves were unaffected at this concentration. Higher concentrations of molinate accumulating in the root of tobacco seedlings may inhibit root development and represent a significant factor in the herbicide's selective action. Seven and eight metabolites were found in tobacco and rice cells, respectively, with molinate sulfoxide and molinate sulfone present in both species. © 1998 SCI