TRANSLOCATION OF 14C-ASSIMILATES AND 3-AMINO-1,2,4-TRIAZOLE AND ITS METABOLITES IN AGROPYRON REPENS

Summary. Translocation of 3-amino-1,2,4-triazole-5-¹⁴C (¹⁴C-aminotriazole) was compared to that of ¹⁴C-assimilates in couch grass ( Agropyron repens (L.) Beauv.) at three different growth stages.
Assimilates of ¹⁴CO₂ were translocated from the treated shoot to other shoots and rhizomes at the 2–3-leaf and 3–4-leaf stages of development. Much less labelled material was translocated into untreated shoots at the 5-leaf stage. More ¹⁴C-assimilates were translocated to the roots than to untreated shoots at all developmental stages. The translocation patterns of ¹⁴C-aminotriazole and ¹⁴C-assimilates were similar.
Two metabolites, A and B, were formed from ¹⁴C-aminotriazole, which chromatographed identically to previously described metabolites in Cirsium arvense (L.) Scop. A was further metabolized into B. Labelled aminotriazole and its two metabolites were translocated throughout the plants. Metabolite A was phytotoxic when concentrated and re-applied to couch grass, but its properties were not those of Unknown II from Cirsium arvense. They were the same as those of Unknown III. Whether or not metabolite A and Unknown III are identical was not established.
Migration des substances assimilables marquées au ¹⁴ C, du 3 amino-1,2,4-triazole et de ses métabolites chez Agropyron repens     

Herbicidal control of Cirsium arvense (L.) Scop,roots and shoots in no-till spring wheat (Triticum aestivum L.)*

Three herbicide treatments were applied each year over a period of 4 years to Cirsium arvense (L.) Scop, infestations in no-till spring wheat (Triticum aestivum L.) in North Dakota, USA. Both chlorsulfuron at 30 g ai ha^?1+a non-ionic surfactant and a mixture of clopyralid+2,4-D at 70+280 g ai ha^?1 gradually reduced Cirsium arvense shoot density, root biomass, and adventitious root buds over the 4-year treatment period in two trials. These two treatments did not merely induce adventitious root buds to become dormant. They virtually eliminated roots to a depth of 50 cm by year 4. Tribenuron methyl at 10 g ai ha^?1+ a non-ionic surfactant was less effective in reducing shoot density and root biomass. Lutte herbicide contre les racines et les tiges de Cirsium arvense (L.) Scop, dans du bli de printemps non laboure (Triticum aestivum L.) Trois traitements herbicides ont été appliqués chaque année pendant 4 ans, contre des infestations de Cirsium arvense (L.) Scop, dans du blé de printemps (Triticum aestivum L.) non labouré dans le Dakota Nord, USA. Tant le chlorsulfuron à 30 g m.a. ha^?+un surfactant nonionique qu'un mélange de clopyralide+2,4-D à 70+280 g m.a. h^? ont reduit progres-sivement la densité des pieds de Cirsium arvense, la biomasse racinaire, et les bourgeons racinaires adventices pendant les 4 années de traitements dans les 2 essais. Ces traitements ont à peu près éliminé les racines sur une profondeur de 50 cm en 4 ans. Ces deux traitements n'ont pas induit de dormance des bourgeons racinaires adventices. Le tribenuron methyl à 10 g m.a. ha^?+un surfactant non ionique a été moins efficace dans la réduction de la densité de plante et de la biomasse racinaire. Chemische Bekämpfung von Cirsium arvense (L.) Scop, in direktgesätem Sommerweizen (Triticum aestivum L.) In direktgesäter Sommerweizen (Triticum aestivum L.) wurdel in North Dakota. USA, Bestände von Cirsium arvense (L.) Scop, über 4 Jahre jährlich 3 Herbizidbehandlungen unterzogen. Sowohl Chlorsulfuron mit 30 g AS ha^?1 nichtionischem Netzmittel als auch eine Mischung von Clopyralid+2,4D mit 70+280 g AS ha^?1 verringerten die Sproßdichte der Acker-Kratzdistel, die Wurzelbiomasse und die Adventivknospen an den Wurzeln in 2 Ver-suchen graduell. Durch diese beiden Behand-lungen wurden nicht nur die Adventivknospen dormant, sondem auch die Wurzeln bis zu einer Tiefe von 50 cm bis zum 4. Jahr fast ganz elimi-niert. Tribenuron-methyl mit 10 g AS ha^?1 nichtionischem Netzmittel war hinsichtlich der Reduktion von Sproßdichte und Wurzelbiomasse weniger wirksam.     

THE EFFECTS OF DIFFERENT LEVELS OF NITROGEN UPON CIRSIUM ARVENSE (L.) SCOP. PLANTS GROWN FROM SEEDS AND ROOT FRAGMENTS

Summary. Growth of Cirsium arvense plants was little affected by nitrogen level for the first 3 weeks of treatment, but differences between levels became apparent later. Shoot dry weight increased more than root dry weight at nitrogen levels of 35 ppm or more. The growth responses to nitrogen were similar in pattern in plants grown from seed and from root fragments, but growth was greater in fragment-derived plants.
Effets de l'azote à diverses concentrations sur des plantes de Cirsium arvense (L.) Scop, issues de sentences ou de fragments de racines
Résumé. La croissance de plantes de Cirsium arvense fut peu affectée par la concentration en azote pour les trois premieres semaines de traitement mais des différences selon les concentrations se manifestérent par la suite. Le poids sec de la partie aćrienne s'accrut plus que le poids sec des racines a des concentrations en azote de 35 ppm ou plus. Les reactions de croissance provoquées par l'azote se déroulérent selon un processus analogue pour les plantes issues de semences et pour celles provenant de fragments de racines, mais dans ce dernier cas, la croissance fut plus importante.
Wirkung verschieden hoher Stickstoffgaben auf Cirsium arvense (L.) Scop, bei Aufwuchs aus Samen sowie aus Wurzelfragmenten
Zusammenfassung. Das Wachstum von Cirsium arvense zeigte wenig Abhangigkeit von der Höhe der Stickstoffgabe während der ersten drei Wochen nach der Applikation, wohl aber spater. Durch Stickstoffgaben von 35 ppm und mehr wurde das Spross-Trockengewicht stärker gefördert als das Wurzel-Trockengewicht. Die Reaktion auf Stickstoff entsprach bei atjs Samen gezogenen Pflanzen weilgehend derjenigen von Pflanzen, die aus Wurzelfragmenten hervorgegangen waren, doch war das Wachstum bei den vegetativ vermehrten Pflanzen allgemein stärker.     

Germination of Seeds of Cirsium arvense (L.) Scop.

Cirsium arvense (L.) Scop. is a persistent and troublesome weed which reproduces vegetatively. Establishment from seeds (achenes) is considered negligible under natural conditions in the United Kingdom (Bates, 1946), although germination under normal farm conditions was found to be good in America (Hansen, 1918). Korsmo (1930) in Norway and Hayden (1934) in Iowa found that the seeds had no dormancy period, but Niethammer (1934) and Zilke (1967) recorded seed dormancy in Germany and South Dakota respectively. An examination was therefore made of some of the factors which may regulate the germination of seeds of C. arvense in this country.     

Control of Cirsium arvense (L) Scop, by herbicides and mowing

The efficacy of mowing and of herbicides (applied by spot spraying or boom spraying) for the selective control of Cirsium arvense (L) Scop, in Victorian pastures was investigated. The pastures were based on Trifolium repens L. and Lolium perenne L. A general decline in the number of thistle shoots in untreated plots at three out of five sites was recorded.‘Tordon 50-d' (5% a.i. picloram and 20% a.i. 2,4-D as triisopropanolamine salts), MCPB, 2,4-DB and mowing resulted in suppression, but not eradication, during the experimental period. MCPB and 2,4-DB are the most suitable herbicides for selective control. The use of‘Tordon 50-d' is restricted by its effect on clovers, soil persistence and cost. Variable growth of C. arvense, associated with variable summer rainfall in Victoria, increases the difficulty in controlling this weed and necessitates a persistent long term approach.     

The allelopathic activity of Californian thistle (Cirsium arvense (L.) Scop.) in Tasmania

The phytotoxicity of extracts from the roots and foliage of Cirsium arvense (L.) Scop, was studied using seven test species. Water and alcohol extracts of C. arvense inhibited the germination of its own and Trifolium subterraneum L. seed, and inhibited the growth of its own seedlings, three annual thistles, and Lolium perenne L., T. subterraneum and Hordeum distichon L. The results are related to phytosociological patterns observed in the field, and it is suggest that the presence of phytotoxins in the soil may make the establishment of some pasture and crop species difficult in areas infested with C. arvense. Activité allélopathique du chardon Cirsium arvense L. Scop, en Tasmanie La phytotoxicityé d'extraits obtenus à partir des racines et du feuillage de Cirsium arvense (L.) Scop, a étéétudiée en tulisant sept espèces servant de tests. Des extraits aqueux et alcooliques de C. arvense inhibèrent sa propre germination et celle des semences de Trifolium subterraneum L. Ils inhibèrent également la croissance de ses propres plantules, de trois chardons annuels, de Lolium perenne L. de T. subterraneum et de Hordeum distichon L. Les résultats sont rapprochés des évolutions phytosociologiques observées au champ, et il est suggéré que la présence de phytotoxines dans le sol puisse rendre difficile l'implantation de certaines espèces fourragères ou autres dans les endroits infestés par C. arvense. Die allelopathische Aktivität von Cirsium arvense (L.) Scop. in Tasmanien Wurzel- und Blattextrakte von Cirsium arvense (L.) Scop. wurden auf ihre phytotoxische Wirkung mit sieben Test-pflanzen geprüft. Wasser- und Alkoholauszüge von C. arvense hemmten die Keimung der eigcnen und der Samen von Trifolium subterraneum L. Das Wachstum der eigenen Keimlinge, sowie von drei annuellen Distelarten, von Lolium perenne L., T. subterraneum und von Hordeum distichon L, wurde gehemmt. Die Ergebnisse zeigen einen Zusammenhang mit pflanzensoziologischen Feldbeobachtungen und es ist denkbar, dass die Gegenwart von Phytotoxinen im Boden den Aufwuchs von Grünlandpflanzen und Feldfrüchten in Fiächen, die mit C. arcense verseucht sind, erschweren kann.     

REGENERATIVE CAPACITY OF ROOT FRAGMENTS OF CIRSIUM ARVENSE (L.) SCOP.

Summary. Root fragments less than 5 mm long were unable to form shoots. However, shoots were produced by fragments 10 mm long and 1 mm in diameter, unless originating from immature apical regions. The number of shoots per unit length of root was greater if the root was cut into many small pieces than into a few long ones. The ability to produce shoots was apparently unrelated to the presence or absence of visible buds.
Root fragments showed polarity; most of the shoots originated from the basal (proximal) end and the roots from the apical (distal) end. Soil moisture content had relatively little effect upon growth from a fragment unless the soil was waterlogged or very dry for prolonged periods. Growth from fragments was prevented by temperatures below 5°C; optimum growth occurred at 15°G. Shoots from fragments 25 mm long emerged successfully from depths of 50 cm.
Capacité de régenération de fragments de racines de Cirsium arvense (L.) Scop.     

Distribution and seed production of Cirsium arvense (L.) Scop, in Victoria, Australia

In 1971 the net area of Cirsium arvense in Victoria was 1300 ha in permanent pasture, 120 ha in cropping land and 40 ha in non-agricultural land. In ten farms in the most heavily infested parish (approximately 100 km²). C. arvense was present in 35 % of the fields and occurred in some highly productive legume-based pastures. The most common control practice on these farms was pasture slashing. It was considered that the weed had been on the farms for 40–80 years. At a constant temperature of 20°C, but not at alternating temperatures, the germination percentage of seed was enhanced by pre-chilling. At constant temperatures the germination percentage was higher at 30°C than at lower temperatures. Alternating temperatures that included 30°C also increased the germination percentage, but it was depressed at 15°/40°C. The germination percentage of seed from forty sites was 52%-97% and some seed was formed where male and female plants were separated by distances of up to 390 m. However, no seed was found in about a third of the parishes examined. Distribution et production de semences de Cirsium arvense (L.) Scop, dans I'etat de Victoria en Australie. En 1971, la surface nette occupée par Cirsium arvense dans pétat de Victoria était de 1300 ha dans les prairies permanentes, de 120 ha dans les terres cultivées et de 40 ha dans les terres non agricoles. Dans 10 fermes situées dans la partie la plus infestée (approximativement 100 km²) C. arvense était present dans 35% des champs et apparaissait dans quelques pâtures hautement productives â base de 1égumineuses. La méthode de lutte la plus fréquente dans ces fermes était la pâture intensive. 11 était admis que la mauvaise herbe était présente dans les exploitations depuis 40 à 80 ans. A la temperature constante de 20°C, maisnon à des tempértures alternées, le pourcentage de germination des semen-ces fut augmenté par une réfrigération préalable. A température constante, le pourcentage de germination fut plus élevé k 30°C quà des temperatures plus basses. Les températures alternées, qui comprenaient celle de 30°C augmentérent aussi le pourcentage de germination, mats celui-ci diminua à 15°/40°C. Les pourcentages de germination de semences de 40 provenances différences se situa entre 52% et 97%; quelques semences furent formées dans des cas où les plantes mäles et les plantes femelles étaient séparées par des distances atteign-ant 390 m. Toutefois aucune semence ne fut trouvée dans un tiers environ des localities examinées. Verbreitung und Samenproduktion von Cirsium arvense (L.) Scop, in Victoria, Australien Die mit Cirsium arvense verseuchte Flfiche in Victoria im Jahre 1971, gliedert sich auf in: 1 300 ha Daucrweide. 120 ha Ackerland und 40 ha nicht-landwirtschafllich genutzte Fläche. In 10 Betrieben des am stftrksten verseuchten Bezirks (ca. 100 km²), war C. arvense in 35% der Felder vorhanden und kam in einigen hochproduktiven Leguminosenweiden vor. Die gebräuchlichste Bekämpfungsmassnahme in diesen Betrieben war das Abmiihen mit Schlegelhilckslem. Es wird angenommen, dass dieses Unkraut seit 40 bis 80 Jahren in den Betrieben vorhanden ist. Bei einer konstanten Temperatur von 20°C, nicht aber bei Wecheseltemperaturen, wurde durch vorheriges Einfrieren die Keimungsrate erhöht. Bei konstanten Temperaturen war sie bei 30°C hSoUher als bei niedrigeren Temperaturen. Wechseltemperaturen die 30°C einschlossen, erhöhten auch die Keimungsrate; bei 15°C/40°C war sie aher geringer. Die Keimung der Samen von 40 Siandorten betrug 52% bis 97%. Wenn weibliche und mflnnliche Pfianzen his zu 390 m von einander entfernt waren. wurden noch einige Samen gebildet. In etwa einem Drittel der untersuchten Bezirke wurden jedoch keine Samen gefunden.     

Uptake, translocation, metabolism and selectivity of glyphosate in Canada thistle and leafy spurge

The uptake, translocation and metabolism of glyphosate [N-(phosphonomethyl) glycine] by Canada thistle (Cirsium arvense (L.) Scop.) (susceptible) and leafy spurge (Euphorbia esula (L.)) (resistant) were examined in an attempt to elucidate the nature of the differential sensitivity. The pattern of uptake and translocation was similar in both species. Glyphosate moved readily in the apoplast and the symplast. High humidity and/or surfactant greatly increased the amount of ¹⁴C-glyphosate absorbed and translocated over that in low humidity and/or without surfactant. No ¹⁴Cmetabolites were detected in either species 1 week after treatment with ¹⁴C-glyphosate. More of a glyphosate spray solution containing a fluorescent dye was received and retained on Canada thistle by virtue of its growth habit than on leafy spurge. More glyphosate should therefore be available for uptake by Canada thistle and this may account for the differential sensitivity of these two species.     

Cirsium arvense (L.) Scop. competition with winter wheat (Triticum aestivum L.)

A series of field experiments was conducted to evaluate the competitive effect of Cirsium arvense (L.) Scop. on winter wheat (Triticum aestivum L. ‘Norstar’) yield. Grain yield at the centre of dense C. arvense patches ranged from 28–71% of the yield in adjacent weed-free plots, based on measurements made at 11 experimental sites over a 2-year period. The mean reduction in yield was 49%. Two models were used to describe grain yield reduction in terms of C. arvense shoot density: (a) linear regression of percentage yield reduction on the square root of shoot density, and (b) non-linear regression, based on a rectangular hyperbola. Both models give similar yield loss estimates at commonly occurring shoot densities of C. arvense, but the non-linear model accounted for more of the observed variation in grain yield. The major yield component affected by C. arvense competition was spikes per unit area, with kernel weight affected to a lesser extent.     

UNTERSUCHUNGEN ÜBER AUFNAHME UND TRANSLOKATION VON 14C-MARKIERTEN HERBIZIDEN IN AGROSTEMMA GITHAGO L. UND TUSSILAGO FARFARA L.

Studies of the uptake and translocation of ¹⁴C-labelled 2, 4-D, MCPA and aminotriazole in Agrostemma githago L. and Tussilago farfara L. clarified the behaviour of the herbicides in both species. In A. githago, MCPA was more freely mobile than 2,4-D after application to the leaf; it was distributed in the plant more rapidly and in greater quantity. Similarly, following root uptake MCPA was transported in the shoot in greater amounts than was 2,4-D. There is a clear relationship between the susceptibility of A. githago to MCPA and the mobility of the herbicide in the plant. In T. farfara, 2,4-D and aminotriazole applied to the leaves were equally well absorbed and relatively rapidly translocated. During the period up to 72 h the amounts of herbicide in the plant increased to similar levels; after that, ¹⁴C activity in plants treated with 2,4-D fell slightly whereas there was further accumulation of aminotriazole. Following uptake through the roots, translocation and accumulation in the leaves were considerably greater with aminotriazole than with 2,4-D. The lack of accumulation of 2,4-D could be a factor in the resistance of T. farfara to this herbicidie. Recherches sur l'absorption et la migration d'herbicides marqués au ¹⁴ C dans Agrostemma githago L. et Tussilago farfara L.     

Absence of 3-(2,4-dichlorophenoxy)propionic acid in plants treated with 2,4-dichlorophenoxyacetic acid‡

Experiments were conducted to establish if the formation of 2.4-dichlorophenol (DCP) from 2.4-dichlorophenoxyacetic acid (2,4-D) in plants proceeds via 3-(2,4-dichtorophenoxy) propionic acid (2,4-DP) as an intermediate. Soybean (Glycine max (L.) Merr.), kidney bean (Phaseolus vtitgaris L.), pea (Pisum. sativum L.), smooth bromegrass (Bromus inermis Leyss.), wild oat (Avena fatua L.), yellow foxtail (Setaria glauca(L.) Beauv.), barley (Hordeum vulgare L.), timothy (Phleum pratense L.). and orchardgrass (Dactylis glomerata L.) were treated with equal weights of 2,4-D and 2,4-DP. After 3 days, all plants contained DCP; however, amounts were larger in plants treated with 2.4-DP than in those treated with 2,4-D. The 2.4-DP was absorbed from the leaf surface more efficiently than 2,4-D. No evidence was found for formation of 2,4-DP from 2,4-D in any of the plant species studied. L'absence de l'acide3-(2,4 dichlorophénoxy) propionique dans les plantes traitées avec I'acide 2,4-dichlorophénoxyacétique Des experiences ont été effectuées pour rechercher si la formation de 2,4-dichlorophénoI (DCP) dans les plantes, à partir de l'acide 2.4-dichlorophénoxy acétique (2,4-D) se produit par l'intermêdiaire de l'acide 3-(2,4-dichlorophenoxy) propionique. Le soja (Glycine max(L.) Merr.). le haricot (Phaseolus vuigaris L.), Ic pois (Pisum sativum L.), le brome (Bromus inermis Leyss.), la folle avoine (Avena fatua L.), la sétaire (Setaria glauca(L.) Beauv.). I'orge (Hordeum vulgare L.), la fléole (Phleum pratense L.) et le dactyle (Dactylis ghmerata L.) ont été traités par des poids égaux de 2.4-D et de 2,4-DP. Trois jours aprés, les plantes contenaient du DCP; toutefois, les quantités trouviés furent plus importantes dans les plantes traitées avec le 2,4-DP que dans celles traitées avec le 2,4-D. Le 2,4-DP a été absorbéà partir de la surface foliaire plus efficacement que le 2,4-D. La formation du 2,4-DP à partir du 2,4-D n'a pu être prouvée dans aucune des plantes étudiécs. Die Abwesenheit von 3-(2,4′Dichlorphenaxy)-propionsäure irt mil 2,4-Dichlorphenoxytesäure behandelten Pflanzen Es wurden Versuche durchgeführt um herauszufinden. ob die Bildung von 2,4-Dichlorphenol (DCP) aus 2.4-Dichlor-phenoxyessigsäure (2,4-D) in Pflanzen über 3-(2,4-Dichlor-phenoxy)-propionsaure (2,4-DP) als Zwischcnprodukt ver-läufl. Sojabohnen (Glycine max(L.) Merr.), Gartenbohnen (Phaseolus vutgaris L.), Erbsen (Pisum sativum L.), Wehrlose Trcspe (Bromus inermis Leyss.), Flughafer (Avena fama L.), Gelbe Borsienhirse (Setaria glauca(L.) Beauv.), Gerste (Hordetim vidgarc L.), Wiesenlieschgras (Phleum pratense L.) und Knaulgras (Dactylis ghmerata L.) wurden mit gleichen Mengen an 2,4-D und 2,4-DP behandelt. Nach drei Tagen enthielten alle PHanzen DCP; aber die Menge an DCP war in den mit 2,4-DP behandelten Pflanzen grosser als in den mit 2,4-D behandelten. 2,4-DP wurde von der Blatt-oberflache besser absorbiert als 2.4-D. In keiner der untersuchten Pflanzenarten konnte ein Hinweis für die Bildung von 2,4-DP aus 2,4-D gefunden werden.     

Absorption and translocation of 14C-3,6-dichloropicolinic acid in Cirsium arvense (L.) Scop.

Experiments were conducted in a growth cabinet to investigate the absorption and translocation of ¹⁴C-3, 6-dichloropicolinic acid by Cirsium arvense (L.) Scop. (Canada thistle, creeping thistle), a sensitive species. Applications were made, either to the middle four leaves of 12-cm-tall vegetative plants grown under low (40%) and/or high (>95%) relative humidity (r.h.), or to four upper or lower leaves of 30-cm-tall flowering plants grown under low r.h. Following application to vegetative plants, absorption and translocation of ¹⁴C-3,6-dichloropicolinic acid was rapid and was approximately doubled by high r.h. High r.h. increased the amount of radioactivity retained by the treated leaves or translocated to the shoots but did not affect greatly the amount retained in the roots. The herbicide was highly mobile, with over half of that absorbed, translocated out of the treated leaves after two days. The apex accumulated most of the radioactivity, while approximately 8% was recovered from the roots. The absorption and translocation patterns were similar to those reported in the literature for picloram in C. arvense. Absorption of 3,6-dichloropicolinic acid was greater in vegetative than in flowering C. arvense plants, and placement of herbicide on lower leaves tended to decrease the amount of radioactivity recovered from shoot apex and increase the amount recovered from the roots. Approximately 15% of the applied radioactivity could not be recovered from treated plants by 2 days after treatment.     

Bentazone selectivity between soybean and Canada thistle*

Postemergence applications of bentazone [3-iscpropyl-1H-2,1,3-benzothiadiazine-4-(3H)-one-2,2-dioxide] have shown promise for weed control in soybean [Glycine max (L.) Merr.]. A high soil moisture regime reduced soybean tolerance to bentazone. Covering the soil with vermiculite prior to spraying avoided the loss in tolerance and suggested that bentazone absorption by roots can occur under conditions of flooding at time of application. Bentazone was more inhibitory to photosynthesis 3 h after application and to respiration 1 day after application to the susceptible Canada thistle [Cirsium arvense (L.) Scop.] than to the tolerant soybean. The retention of less spray on leaf surfaces and faster metabolism of absorbed bentazone by soybean appear lo contribute to the observed selectivity. Movement of the ¹⁴C-label from the site of ¹⁴C-bentazone application in either species was primarily acropetal within the treated leaf. Sélectivité de la hentazone vis-á-vis du soja et du chardon Des applications en postlevée de bentazone (3-isopropyl-1H-2,1,3-benzothiadiazine-4-(3H)-one,2,2-dioxyde) se sont nion-trées prometteuses pour de désherbage du soja (Glyeine max (L.) Merr.). Un taux élevé d'humidité du sol a réduit la résistance du soja á la bentazone. Le recouvrement du sol avec de la vermiculite avant le traitement a évité la perte de resistance, de qui suggere que rabsorption de la bentazone par les racines peut se produire lorsqu'il y a submersion au moment du traitement. La bentazone s'est montré e plus inhibitrice pour la phclosynthé se 3 heures apré s l'application, et pour la respiration, 1 jour apré s Tapplication, pour le chardon, (Cirsium arvense (L.) Scop.) plante sensible, que pour le soja, plante risistante. La retention plus faible du liquide pulvérisé sur les surfaces foliaires et le métabolisme plus rapide de la bentazone par le soja semble contribuer á la sélectivité observé e. La migration du ¹⁴C depuis le site d'application de la ¹⁴C-bentazone dans les deux espéces a ite au début acropétale á l'intérieur des feuilles traitées. Selektivität von Bentazon zwisehen Sojabohne und Acker-Kratzdistel Die Verwendung von Bentazon [3-Isopropyl-1H-2,1,3-benzothiadiazin-4-(3H)-one-2,2-dioxid] im Nachauflaufver-fahren zur Unkrautbekämpfung in Sojabohnen [Glyeine max. (L.) Merr.] ist vielversprechend. Hohe Bodenfeuch-tigkeit verminderte die Toleranz von Bentazon gegenüber der Sojabohne. Bedecken des Bodens mit Vermikulit vor der Spritzung bewirkte, dass die Kultur nicht geschSdigt wurde und lässt daher vermuten, dass Bentazon über die Wurzeln aufgenommen wird. wenn zur Zeit der Anwendung der Boden sehr feucht ist. Bentazon hemmte 3 h nach der Applikation die Photosynthese und einen Tag nach der Anwendung die Atmung bei der Acker-Kratzdistel (Cirsium arvense (L.) Scop.] stärker als bei der toleranten Sojabohne. Die geringere Rentention auf der Biattobertiäche und der raschere Metabo-lismus des aufgenommenen Bentazons scheint zur Selektivitat bei der Sojabohne beizutragen. Aktivität von ¹⁴C-Bentazon wurde im Blatt beider Arten hauptsachlich akropetal transloziert.     

Influence of pasture grass and legume swards on seedling emergence and growth of Carduus nutans L. and Cirsium vulgare L.

Swards of 10 pasture species (six grasses and four legumes) were established and planted with seeds of either of the thistle species Carduus nutans L. or Cirsium vulgare L., and emergence and growth of the thistle seedlings were subsequently monitored. Emergence of C. nutans seedlings was inhibited by ryegrass (Lolium perenne L.) and Yorkshire fog (Holcus lanatus L.) swards, while C, vulgare emergence was inhibited by Yorkshire fog relative to some of the other treatments. Speed of emergence of C. nutans and absolute emergence of C. vulgare seedlings were significantly negatively correlated with pasture cover density, presumably as a consequence of alteration of light quality by the pasture swards. All pasture species inhibited seedling shoot and root growth of both thistle species, although the grasses were the most effective inhibitors. The seedling emergence and growth data for C. nutans in the swards of the 10 species were significantly correlated with the results of a previous study on residual allelopathic effects of the same 10 species on nodding thistle root growth. It is concluded that inhibitory (including allelopathic) influences of pasture species on thistle seedlings have considerable potential as a mechanism for managing problematic thistle populations. Influence de converts de pature de graminees et de legumineuses sur la levée et la croissance de Carduus nutans L. et Cirsium vulgare L. Des couverts de 10 espèces fourrageres (6 graminées et 4 légumineuses) ont étéétablis et infestés avec des graines de 1'une ou 1'autre des espèces de chardon, Carduus nutans L. et Cirsium vulgare L.; la levée et la croissance des plantules de chardon ont été ensuite suivies. La levée des plantules de C. nutans a été inhibéee par les couverts de ray-grass (LoliumperenneL.) et de houlque laineuse (Holcus lanatus L.) tandis que la levée de C. vulgareétait inhibée par la houlque laineuse en comparaison de quelques-unes des autres modalites. La vitesse de levée de C. nutans et la levée globale de C. vulgare ont été corrélées négativement de façon significative avec la densité du couvert, probablement en conséquence de 1'altération de la qualité de la lumière par les tapis, fourragers. Toutes les espèces de fourrages ont inhibé la croissance des tiges et des racines des plantules des 2 espèces de chardon, bien que les graminèes aient été des inhibiteurs plus efficaces. La Ievée des plantules et les chiffres de la croissance de C. nutans dans les couverts des 10 espéces étaient correlées de façon significative avec les résultats d'une étude antérieure sur les effets allélopathiques résiduels de quelques-unes des 10 espèces sur la croissance racinaire du chardon. II est conclu que les effets inhibiteurs (y compris I'allélopathie) des espèces fourragères sur les plantules de chardon ont un potentiel considèrable pour gérer le problème des populations de chardon. Einfluβ von Weidegräser- und Leguminosen-Beständen auf Samenkeimung und Wachstum von Carduus nutans L. und Cirsium vulgare L. In Beständen von 10 Weide-Pflanzenarten (6 Gräser und 4 Leguminosen) wurden Samen der Disteln Carduus nutans L. und Cirsium vulgare L. ausgebracht und deren Keimung und Wachstum beobachtet. Die Keimung von Carduus nutans wurde in Beständen von Weidelgras (Lolium perenne L.) und Wolligem Honiggras (Holcus lanatus L.) gehemmt, während die Keimung von Cirsium vulgare in Wolligem Honiggras genauso wie in einigen anderen Beständen gehemmt war. Die Keimungsgeschwindigkeit von Carduus nutans und die gesamte Keimung von Cirsium vulgäre waren signifikant negativ mit der Dichte der Weide-Pflanzenbestände korreliert, vermutlich wegen Änderung der Lichtqualität durch die Pflanzendecke. Alle Weide-Pflanzenarten, besonders jedoch die Gräser, hemmten das Sproß- und Wurzelwachstum der Keimpflanzen der beiden Disteln. Keimung und Wachstum der Carduus-nutans-Keimpflanzen in den Beständen der 10 Arten entsprachen ganz den Befunden einer früheren Untersuchung über allelopathische Wirkungen derselben 10 Arten auf das Wurzelwachstum der Nickenden Distel. Den Hemmwirkungen (einschließlich allelopathischen) von Weide-Pflanzenarten auf Distel-Keim-pflanzen kommt offenbar eine erhebliche Bedeutung für die Unterdrückung problematischer Distelpopulationen zu.     

SHOOT ZONE UPTAKE OF SOIL-APPLIED HERBICIDES IN PISUM SATIVUM L.

Summary. The effects of localized herbicide placement at different internodes of pea ( Pisum sativum L. cv. Alaska) shoots below the soil surface after plant emergence were studied by removing the soil from around the shoots and replacing with herbicide-treated soil. The first internode proved insensitive to linuron, diuron, atrazine and simazine at 4·5 kg/ha, while treatment of the second and third internodes markedly reduced plant growth 4–6 days after treatment. Separate exposure of the first internode alone, and the second and part of the third together to ¹⁴C-labelled atrazine indicated no difference in herbicide metabolism. However, a two- to threefold increase in ¹⁴C uptake and movement to the foliar parts occurred when the second and part of the third internode was treated, as compared to first internode treatment. Thus the differential sensitivity of the internodes to atrazine, and possibly to the other herbicides, may be because the more mature first internode allows less uptake and subsequent movement to the foliar parts.
Absorption dans la zone des tiges des herbicides appliqués dans le sol chez Pisum sativum L.     

Floral attractants for the female soybean looper, Thysanoplusia orichalcea (Lepidoptera: Noctuidae)

BACKGROUND: The soybean looper, Thysanoplusia orichalcea (F.), is a polyphagous insect pest of vegetable crops. Indonesian in origin, it has spread to Europe, India, Africa, Australia and New Zealand. The identification of an attractant for female T. orichalcea could enable the development of alternative pest management strategies to those provided by insecticides or sex pheromones, which are often only attractive to males. RESULTS: Traps baited with synthetic lures derived from Canada thistle, Cirsium arvense (L.) Scop., floral volatiles attracted female T. orichalcea. Phenylacetaldehyde, a floral compound attractive to many Lepidoptera and present in C. arvense, was tested alone as an attractant for the soybean looper and caught significantly more female than male T. orichalcea. Trap catch was greatest when phenylacetaldehyde was combined with five prevalent volatiles present in C. arvense headspace collections: 2‐phenylethyl alcohol, methyl salicylate, dimethyl salicylate, benzaldehyde and benzyl alcohol. Twice as many female moths as males were collected. CONCLUSION: Successful trapping of female T. orichalcea in either a lure‐and‐kill or a mass trapping system may offer an effective way to manage its population size. Copyright © 2008 Society of Chemical Industry     

TRANSLOCATION OF AMINOTRIAZOLE AND DALAPON IN AG ROPY RON REPENS (L.) BEAUV.

Summary. Tracer studies using single drops of solutions containing 3–amino-1,2,4–triazole-5–¹⁴C (aminotriazole-¹⁴C) or 2,2–dichloropropionic acid-2–¹⁴C (datapon-¹⁴C) revealed that in couch plants (Agropyron repens (L.) Beauv.) growing under field conditions in the autumn and at the stage where the aerial shoots were 40–50 cm long, both compounds moved in both symplast and apoplast. Dalapon was less mobile in the symplast than aminotriazole and only negligible amounts of dalapon were translocated to the rhizomes. The nodes of the treated shoots appeared to act as barriers to translocation, a phenomenon more pronounced for dalapon than for aminotriazole.
Application to a basal green leaf led to a more uniform distribution of the compounds within plants and rhizomes than when the application was made to the youngest fully-expanded leaf.
In couch plants with aerial shoots 10–15 cm long treated in the stubble, the distribution of both aminotriazole and dalapon was mainly restricted to the treated shoots. Even 15 days after application only trace amounts of radioactivity could be found in the rhizomes and untreated shoots.     

Growth and regenerative capacity of plants of Cirsium arvense

The undisturbed growth and regenerative capacity of the root system of Cirsium arvense (L.) Scop, were studied in one glasshouse and one field experiment. In the glasshouse experiment, two lengths of root fragment from the same clone, previously grown at two nitrogen levels, were planted in boxes. Plants that developed from these fragments were inspected on eight occasions to assess their undisturbed development and growth, above and below ground, and their regenerative capacity after disturbance by burial at different points of development. The initial nitrogen content of the roots had no effect on growth measurements, but longer root fragments produced greater masses of primary shoots, new roots and shoots from the new roots than did shorter ones. After disturbance at early stages (4-7 leaves with a minimum length of 5 cm), plants originating from shorter root fragments did not regrow at all. Plants originating from longer root fragments exhibited a minimum regenerative capacity when disturbed at the eight-leaf stage. In the field experiment, root fragments of length 12 cm. from the same clone, were planted in October 1991 at 5 cm or 20 cm depth. Plants that developed from these fragments were studied on 12 occasions, from April to July 1992. Plants emerging from a depth of 20 cm reached a point of positive net assimilation 28 days (380 day degrees) later than those developing from a depth of 5 em. The plants exhibited a minimum regenerative capacity when their primary shoots had. on average. 10 (plants from 5-cm root fragments) or seven (plants from 20-cm root fragments) expanded leaves.     

TRANSLOCATION AND PERSISTENCE OF 2,4-D IN POPULUS TREMULA L.

Summary. Treatment of aspen ( Populus tremula L.) with 2,4-dichlorophenoxyacetic acid (2,4-D), using a leaf spray, basal bark spray or a stem injection method of application, resulted in some reduction of stump regrowth although downward translocation of 2,4-D was slight. Persistence of 2,4-D in dead leaf tissue and in woody tissue near the injection sites was observed. This persistence could in certain circumstances be noted 6 years after treatment.
Migration et persistance du 2,4-D chez Populus tremula L.