bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of atrazine on growth, production of aflatoxin, and fatty acid and sterol biosynthesis by Aspergillus spp.
Authors: FERNANDO T. , BEAN G. , GLENN S.
Published: July 2006

Summary: Résumé: Zusammenfassung

The effects of atrazine were studied on growth, production of aflatoxin, and fatty acid and sterol biosynthesis by four isolates of Aspergillus in vitro. There was little effect of atrazine on Aspergillus spp. at concentrations up to 20 μg ml−1 but at 40 μg ml−1 or above, growth, production of aflatoxin, and fatty acid and sterol biosynthesis were remarkably reduced. Palmitic, stearic and linoleic acid synthesis were inhibited in three of the isolates tested at 60 μg ml−1. At 100 μg ml−1, except ergosterol, the cholesterol and 5, 7‐ergostadienol synthesis was totally inhibited in all isolates.

Effet de l'atrazine sur la croissance, la production d'aflatoxine, et la biosynthèse d'acides gras et de stérols par Aspergillus spp.

Chez quatre isolats d'Aspergillus, les effets de l'atrazine sur la croissance, la production d'aflatoxine, et la biosynthèse d'acides gras et de stérols ont étéétudiés in vitro. Jusqu'à des concentrations de 20 μg ml−1, l'atrazine n'a eu que peu d'effets, mais à 40 μg ml−1 et au‐dessus, la croissance, la production d'aflatoxine, et la biosynthèse d'acides gras et de stérols ont été nettement réduites. Les synthèses d'acides palmitique, stéarique et linoléique ont été inhibées chez trois des isolats, à 60 μg ml−1. A 100 μg ml−1, mis à part l'ergostérol, les synthèses de cholestérol et de 5, 7‐ergostanediol ont été totalement inhibées chez tous les isolats.

Die Wirkung von Atrazin aufdas Wachslum, die Bildung von Aflatoxin und die Fettsäuren‐ und Sterol‐Biosynthese von Aspergillus spp.

Bei vier Isolaten von Aspergillus wurde in vitro die Wirkung auf das Wachstum sowie auf die Bildung von Aflatoxin, Fettsäuren und Sterolen untersucht. Bei Atrazin‐Konzentrationen bis zu 20 μg ml−1 war keine Wirkung zu beobachten, aber ab 40 μg ml−1 wurden das Wachstum und die Bildung von Aflatoxin, Fettsäuren und Sterolen deutlich herabgesetzt. Bei 60 μg ml−1 war bei drei Isolaten die Bildung von Palmitin‐, Stearin‐ und Linolensäure gehemmt. Bei 100 μg ml−1 war bei alien Isolaten die Bildung von Cholesterol und 5, 7‐Ergostadienol, aber nicht Ergosterol, unterbunden.
Distribution of diclofop‐methyl and metabolites in oat (Avena sativa L.) protoplasts
Authors: HOLL F. B. , TRITTER S. A. , TODD B. G.
Published: July 2006

Summary: Résumé: Zusammenfassung

The metabolism of the herbicide diclofop‐methyl and the distribution of it and its metabolites have been investigated in a system utilizing isolated oat protoplasts (Avena sativa L. ‘Cascade’). Accumulations of 14C‐diclofop‐methyl were found in membrane fractions of the protoplasts. Diclofop‐methyl partitioned into the lipid phase of the protoplast plasma membrane. Comparatively small amounts of diclofop were found associated with the protoplasts. Diclofop‐methyl was converted to diclofop in the treatment solution by hydrolytic enzymes associated with the external surface of the protoplast. Approximately 78% of the radiolabel recovered from the treatment solution was diclofop. The two major accumulations of radiolabel were found in the water insoluble portion (membrane fraction) of the protoplast as diclofop‐methyl and in the treatment solution as diclofop.

Repartition du diclofop‐methyl et de ses métabolites dans les protoplastes d'avoine (Avena sativa L.)

Le métabolisme de l'herbicide diclofop‐methyl (DM) et la répartition du DM et de ses métabolites ont étéétudiés dans un système faisant appel à des protoplastes d'avoine isolés (Avena sativa L.) ‘Cascade’. Des accumulations de 14C‐diclofop‐methyl ont été trouvées dans la fraction membranaire des protoplastes. Le diclofop‐methyl est passé dans la phase pidique de la membrane plasmique du protoplaste. En comparaison, de petites quantités de diclofop ont été trouvées en association avec les protoplastes. Le diclofop‐methyl a été converti en diclofop par des hydrolases associées à la surface externe des protoplastes. Approximativement 78% des traces radioactives retrouvées dans la solution de traitement étaient du diclofop. Les deux principales accumulations de radioactivitéétaient trouvées dans la fraction insoluble dans l'eau des protoplastes (fraction membranaire) sous forme de diclofop‐méthyl et, dans la solution de traitement, sous forme de diclofop.

Verteilung von Diclofop‐methyl und Metaboliten in Hafer‐ (Avena sativa L.)‐Protoplasten

Der Abbau von 14C‐markiertem Diclofop‐methyl und die Verteilung des Wirkstoffs sowie eines Metaboliten wurden in isolierten Protoplasten von Hafer (Avena sativa L. ‘Cascade’) untersucht. Der Wirkstoff war in den Protoplastenmembranen angereichert, wobei eine Anlagerung an die Lipidphase der Plasmamembran festgestellt wurde. Von Diclofop waren vergleichsweise geringe Mengen an die Protoplasten gebunden. Diclofop‐methyl wurde in der Versuchslösung durch hydrolytische Enzyme, die an der Protoplastenaussenfläche lagen, zu Diclofop umgewandelt. Radioaktiv markierte Stoffe wurden hauptsächlich als Diclofop‐methyl am Protoplasten‐membransystem und als Diclofop (mit 78% der eingebrachten 14C‐Aktivität) in der Lösung gefunden.
Variation in Chrysanthemoides monilifera (Compositae) in eastern Australia
Authors: SIMMONS D. M. , FLINT P. W.
Published: July 2006

Summary: Résumé: Zusammenfassung

Populations of Chrysanthemoides monilifera ssp. monilifera and C. monilifera ssp. rotundata were sampled over their ranges on mainland eastern Australia, and the extent of geographic variation in some morphological characters determined, Both subspecies were morphologically relatively homogeneous over the populations sampled and no obvious patterns of phenotypic variation within them were detected. The subspecies were readily distinguished from each other and no intermediate forms were observed. However there was more phenotypic variation in ssp. monilifera than in ssp. rotundata. The subspecies have ranges in Australia broadly corresponding to their climatic ranges in South Africa, and ssp. monilifera occurs over a wider climatic range in Australia than ssp. rotundata. Further work on genotypic variation within the species is needed.

Variation chez Chrysanthemoides monilifera (Compositae) en Australie orientale

Des populations de Chrysanthemoides monilifera spp. monilifera et C. monilifera spp rotundata ont été prélevées dans leur site en Australie de l'Est et l'étendue de la variation géographique pour quelques caractères morphologiques déterminée. Les deux sous‐espèces étaient relativement homogènes pour les populations collectées et aucun exemple évident de variation phénotypique au sein d'entre elles n'a été mis en évidence. En revanche, les deux sous‐espèces étaient bien distinctes entre elles et aucune forme intermédiaire n'a été observée. Cependant, il y avait plus de variabilité phénotypique chez spp. monilifera que chez ssp. rotundata. Les sous‐espèces ont une répartition en Australie en relation avec leur répartition climatique en Afrique du Sud et ssp. monilifera est présente sur une plus large aire climatique en Australie que ssp. rotundata. Des travaux supplémentaires sur la variabilité génétique intra espèce s'avèrent nécessaires.

Variabilität von Chrysanthemoides monilifera (Compositae) in Ost‐Australien

Die geographische Variabilität der Unterarten monilifera und rotundata von Chrysanthemoides monilifera wurde an Pflanzen, die in ihren Verbreitungsgebieten in Ost‐Australien gesammelt worden waren, an einigen morphologischen Eigenschaften bestimmt. Beide Unterarten waren morphologisch recht einheitlich, wenn auch die ssp. monilifera eine grössere phänotypische Variabilität hatte. Die Unterarten liessen sich einfach unterscheiden, und es wurden keine intermediären Formen beobachtet. Die Verbreitung der Unterarten in Australien entspricht weitgehend ihren klimatischen Arealen in Südafrika, so dass die ssp. monilifera in Australien einen klimatisch weiteren Bereich besiedelt als ssp. rotunda. Die Art muss eingehender genotypisch untersucht werden.
Comparison of chlorsulfuron and metsulfuron for control of Allium vineale L.
Authors: LEYS A. R. , SLIFE F. W.
Published: July 2006

The response of natural and planted stands of Allium vineale L. to chlorsulfuron and metsulfuron was determined in field experiments in Illinois, U.S.A., in 1982 and 1983. In natural stands very low rates of either herbicide controlled A. vineale. Chlorsulfuron, applied in the spring at 20 g ha−1, reduced aerial bulblet production by 99% but when it was applied in the fall it reduced aerial bulblet production by only 59%. All rates of metsulfuron (5–20 g ha−1), at both times of application, effected better than 94% reduction in plant density and yield of aerial bulblets. In a glasshouse experiment, plants derived from aerial bulblets were more susceptible to chlorsulfuron than plants derived from soft offset bulbs. Soft offset bulbs were, therefore, used to establish a uniform stand of A. vineale in the field. In this experiment, non‐linear regression analysis showed that metsulfuron was two to three times more active than chlorsulfuron. GR95 values calculated from the computed regression equations show that metsulfuron and chlorsulfuron, applied in April at 5 and 15 g ha−1, respectively, reduced aerial and underground bulb production by 95%.
Joint action of Cochliobolus lunatus and atrazine on Echinochloa crus‐galli (L.) Beauv.
Authors: SCHEEPENS P. C.
Published: July 2006

The potential of the endemic fungus Cochliobolus lunatus as a biological control agent against Echinochloa crus‐galli was investigated. Under appropriate conditions the fungus produced leaf necrosis on E. crus‐galli resulting in death of young seedlings. However, plants with more than two leaves mostly recovered after some time. Bean, barley, maize, oat, rye, tomato and wheat were highly resistant to the fungus. In experiments in a climate room or in a glasshouse E. crus‐galli with more than two leaves could effectively be controlled by C. lunatus in combination with a sub‐lethal dosage of atrazine as low as 2.5 mg m−2 due to a positive interaction between fungus and herbicide.
Comparison of root‐ and shoot‐acting growth retardants on a grass/clover sward
Authors: PARR T. W. , MARRS R. H. , BOORMANR L. A. , PLANT R. A.
Published: July 2006

The effects of six grass growth retardants, maleic hydrazide (±2,4‐D), mefluidide, paclobutrazol, EL500 and a mixture of mefluidide with paclobutrazol on a grass/clover sward were compared over a 3‐year period. Maleic hydrazide, which is the most commonly used retardant, gave poor levels of growth control except when used with 2,4‐D. Greatest growth suppression, a 38% reduction in dry matter production from May to July, was obtained from a mixture of mefluidide and paclobutrazol. Differences were observed between the effects of the shoot‐acting retardants, maleic hydrazide and mefluidide and the root‐acting retardants, paclobutrazol and EL500. Shoot‐acting retardants were less effective in wet weather and lasted for a shorter period than root‐acting retardants. They also increased compensatory growth after a period of growth suppression, and increased the proportion of clover in the sward.
Dégradation catalytique de carbamates herbicides déposés sur bentonites homoioniques. V. Cas du CEPC
Authors: SABADIE J. , COSTE C. M.
Published: July 2006

Le CEPC se dégrade lentement à 20 °C et en phase sèche au contact de divers supports minéraux: gel de silice et bentonites homoioniques (Bentonite Prolabo, MontmoriMonite K 10; Cu2+, Zn2+, Fe3+ et Ag+). L'hydroxylation de l'atome de chlore terminal est généralement prépondérante tandis que la cyclisation en oxazolidone ou l'hydrolyse de la fonction carbamate demeurent limitées. La formation intermédiaire d'isocyanate n'a pas été observée. La sélectivité de la conversion est principalement influencée par la nature et l'acidité du support, le métal de saturation et la méthode d'imprégnation.
Physiological activity spectra of existing graminicides and the new herbicide 2‐(2‐benzothiazolyl‐oxy)‐N‐methyl‐N‐phenylacetamide (mefenacet)
Authors: FEDTKE C.
Published: July 2006

inhibitory activities of existing graminicides on root regeneration from monocotyledonous (oat) and dicotyledonous (soybean) plant cuttings in the light, in the dark and on algal growth were compared with the respective inhibitory activities of the new herbicide 2‐(2‐benzothiazo‐lyl‐oxy)‐N‐methyl‐N‐phenylacetamide (mefenacet). The mefenacet activity spectrum resembled that of the α‐chloroacetamide herbicides. Herbicide groups of other structure‐activity can be distinguished by their distinct activity spectrum. The mono‐oxygenase inhibitors piperonyl but‐oxide (PBO) and 1‐aminobenzotriazole (ABT) were found to antagonize the inhibitory activities of herbicides from the thiolcarbamate, α‐chloroacetamide, and oxyacetic acid amide structure groups in the oat rooting and leaf growth tests. The critical evaluation of the presently available information on graminicide and safener mode of action suggests the concept that lipid biosynthesis on the physiological level and mono‐oxygenase type enzymes on the biochemical level may hold the target sites for many of the graminicides and safeners discussed.
Germination of proximal and distal seeds of Poa trivialis L. from contrasting habitats
Authors: FROUD‐WILLIAMS R. J. , FERRIS R.
Published: July 2006

Seeds of Poa trivialis L. were collected from one grassland and two arable habitats. Seeds from the grassland population were less dormant than the arable populations. Distal (upper) seeds were consistently more dormant than proximal (basal) seeds. Dry storage at 4°C and 15°C for 4 weeks after shedding resulted in a slightly greater loss of dormancy than storage at 23°C. Germination was enhanced by subjecting seeds stored at 15°C to repeated hydration and dehydration cycles. Germination of P. trivialis seeds was density‐dependent. Germination of distal seeds was particularly impaired at high densities. The ecological implications of these results are discussed in relation to seed survival strategies.
Establishment of Senecio jacobaea L. from seed in grassland and in boxed swards
Authors: WATT T. A.
Published: July 2006

The effects of a high or a low level of nitrogen fertilizer and the presence or absence of a grass‐suppressing herbicide (propyzamide) upon the establishment of Senecio jacobaea L. (common ragwort) in three sizes of bare soil patch in a perennial ryegrass sward (Lolium perenne L.) were investigated both in boxed swards and in the field.
Influence of tillage, straw disposal system and seed return on the population dynamics of Alopecurus myosuroides Huds. in winter wheat
Authors: MOSS S. R.
Published: July 2006

Alopecurus myosuroides Huds. was studied over a 2‐year period in winter wheat established after tine cultivations or direct drilling. Straw was removed by baling or spread and burnt. Seed production was either allowed or prevented by cutting and removing all vegetation at the end of the first year. Cultivation differences had no consistent effect on plant or seed populations. Straw burning destroyed about 50% of seeds and encouraged the germination of surviving seeds. Weed populations in the crop were lower on burnt than on baled areas. Where seed shedding was allowed, populations of seeds in soil and plants increased by up to nine‐fold per year. Straw burning resulted in smaller population increases. Seed decline in the soil averaged about 80% per year, so that less than 6% of the weed seeds sown were still viable after 2 years’burial in the soil. Most of the seed decline occurred between July and October and was slightly greater on burnt than on baled areas. Only part of this seed loss was accounted for by germination and emergence of seedlings during summer and autumn. Plants emerging in the crop represented less than 26% of viable seeds present in the soil at time of drilling the crop. Few seedlings emerged in spring. The viability of shed seeds varied with year and with weed density. High infestations were associated with lower seed viability and also fewer heads per plant.
Glyphosate effects on Canada thistle (Cirsium arvense) roots, root buds, and shoots
Authors: CARLSON S. J. , DONALD W. W.
Published: July 2006

Glyphosate† was sprayed at 0009–1·12 kg a.i. ha−1 on the foliage of large potted glasshouse‐grown Canada thistle [Cirsium arvense (L.) Scop.], which had extensive, well‐developed roots. Increasing the glyphosate rate progressively reduced the total number of visible adventitious root buds plus emerged secondary shoots per plant proportionately more than root biomass, 10 days after treatment. Cortical tissue of thickened propagative roots became soft, water‐soaked, darkened, and some regions decomposed, exposing strands of vascular tissue. Lateral roots completely decomposed. When thickened roots were segmented to stimulate secondary shoot emergence from root buds 10 days after foliar treatment, Fewer secondary shoots emerged than expected from the number of visible adventitious root buds present on both control and herbicide‐treated plants. Increasing the rate of glyphosate also reduced the regrowth potential of root buds proportionately more than root biomass. Regrowth potential was measured as the number of emerged secondary shoots 35 days after segmenting unearthed roots from plants that had been sprayed 10 days earlier. When foliar‐applied at 0·28 kg ha−1, glyphosate decreased the regrowth potential of root buds to zero in 2 and 3 days, as measured by secondary shoot dry weight and number, respectively, even though root fresh weight was unchanged 3 days after foliar treatment. These dose‐response and time‐course experiments demonstrate that glyphosate did not reduce root biomass as much as it decreased root bud numbers and secondary shoot regrowth potential from root buds.
Relations entre la vitesse de dégradation du propyzamide et les propriétés physicochimiques des sols
Authors: BARRERE C. , BASTIDE J. , COSTE C. M.
Published: July 2006

L'étude de la dégradation du propyzamide est réalisée dans 29 sols, dans des conditions de température et d'humidité constantes. Une relation est trouvée entre la vitesse de dégradation et la résistivité des sols. Un apport d'engrais dans les sols entraine une diminution de la résistivité qui se traduit par un ralentissement de la vitesse de dégradation.
Weeding and nitrogen effects on farmers' wheat crops in semi‐arid Morocco
Authors: TANJI A. , REGEHR D. L.
Published: July 2006

The effects of three weeding systems with and without top‐dressed nitrogen were examined in 40 experiments on bread wheat and durum wheat planted by farmers in the Chaouia (semi‐arid area of Morocco) in 1984–1985 and 1985–1986 growing seasons. In both years, hand‐weeding to simulate collection of forage reduced weed numbers by 30% and removed 63% of the weed dry weight. Treatment with 2, 4‐D removed 66% of the weeds and reduced weed dry weight by 82%, in 1985–1986. Hand‐weeding for forage produced 427 kg ha−1 weed dry matter in both years, but wheat grain yields were 179 kg ha−1 lower than with 2.4‐D treatments. Over both years, the cost of each kg weed forage was 0·43 kg grain yield loss. Without weeding grain yields were 130 kg ha−1 lower than 2, 4‐D treatments. Weed control with 2,4‐D increased wheat grain yields over both non‐weeded and hand‐weeded treatments by an average of 154 kg ha−1. Overall, there were no significant effects of nitrogen on wheat or weed yields nor interactions between top‐dressed nitrogen and weeding systems. A total of 157 weed species belonging to 29 botanical families were identified on the 40 experimental sites over both years; 89% were dicotyledons. Papaver rhoeas L. (common poppy), 2, 4‐D susceptible plant, was the most annual weed in wheat fields in Chaouia.
Influence of time of emergence of wild oat on competition with wheat
Authors: MARTIN M. P. L. D. , FIELD R. J.
Published: July 2006

The influence of time of emergence of wild oat (Avena fatua L.) on its competition with wheat (Triticum aestivum L.) was studied, using boxes that allowed separation of root and shoot competition. The relative yield total for mixtures of wild oat and wheat, grown under different forms of competition and with different wild oat sowing times, was very close to unity, indicating that the two species competed fully for limiting resources. Wild oat was more competitive than wheat when the two species were sown simultaneously, due largely to its greater root competitive ability; the two species had similar shoot competitive abilities. When wild oat was sown 3 or 6 weeks later than wheat, wheat was more competitive than wild oat and the production of wild oat panicles was prevented. This was mainly the result of greater root competitive ability of the wheat, although shoot competitive ability was also greater. The effects of root and shoot competition were additive. It is concluded that in order to prevent the return of wild oat seeds to the soil, and hence obtain long‐term benefit, it is necessary to control the wild oat seedlings emerging within the first 3 weeks after drilling a wheat crop.
Selectivity of 2,4‐D in Solanum ptycanthum Dun. and Lycopersicon esculentum Mill.
Authors: HALL J. C. , SWANTON C. J.
Published: July 2006

In controlled environmental studies, a marked difference was observed between the growth pattern of tomato and eastern black nightshade plants that received doses of 2,4‐D ranging from 28 to 952 g a.e. ha−1. The highest dose of 2,4‐D reduced the dry weight of eastern black nightshade and tomato by approximately 15 and 50%, respectively, when compared with controls. Although the height of both species was reduced by all doses of 2,4‐D, eastern black nightshade plants produced secondary shoots, which compensated for any potential loss in dry weight that otherwise may have occurred. Tomato plants did not produce secondary shoots. After application of 14C‐2,4‐D to tomato and eastern black nightshade, the pattern of 14C absorption and translocation was similar in both plant species. However, there was significantly more radioactivity recovered in tomato (72%) than in eastern black nightshade (52%) plants, 72 h after treatment. Assay radioactivity in the nutrient solution of hydroponically grown plants indicated that 7·0 and 27·9% of the applied radioactivity was exuded from the roots of tomato and eastern black nightshade, respectively, within 72 h after treatment. Assay of plant extracts by thin layer chromatography revealed that the amount of radioactivity that remained as unaltered 2,4‐D was 73 and 49% in tomato and eastern black nightshade, respectively, 72 h after treatment. Thus the greater tolerance of eastern black nightshade appeared to be due to greater rates of 2,4‐D metabolism and/or greater rates of herbicide elimination by root exudation.
Effect of narrow‐leaved hawk's‐beard (Crepis tectorum L.) on yield and quality of lucerne hay and seed yield of creeping red fescue
Authors: PESCHKEN D. P. , DARWENT A. L.
Published: July 2006

Narrow‐leaved hawk's‐beard (Crevis tectorum L.) occurs in all provinces of Canada, but is particularly abundant in the northern portions of the agricultural regions of the three prairie provinces and British Columbia. The losses in yield in terms of quantity and quality due to narrow‐leaved hawk's‐beard were investigated in fields of lucerne (Medicago sativa L.) used in the dehydration industry and in experimental plots. The effect of hawk's‐beard on creeping red fescue (Festuca rubra L.) seed yield in the Peace River Region of British Columbia was also investigated. In the lucerne, the average percentage of hawk's‐beard in the total biomass over the 3 years of the study was only 2⋅5%, with a minimum of 1⋅2% in one year and a maximum of 5⋅5% in another year. In the lucerne vs hawk's‐beard plots, yields on plots free of hawk's‐beard were not significantly higher than on those with hawks'‐beard. Although excellent control was achieved in creeping red fescue (Festuca rubra L.) by the use of the herbicide 2, 4‐DB, yields of seed were not significantly increased. Therefore, narrow‐leaved hawk's‐beard seems to be an excellent colonizer but a weak competitor and contributed little to crop losses in lucerne and creeping red fescue.
Efficacy of chemical weed control in spring cereals in Finland
Authors: SALONEN J. , ERVIÖ L.‐R.
Published: July 2006

A national survey was conducted in Finland from 1982 to 1984 to determine the main weed species in spring cereals and the efficacy of herbicides on Finnish farms. The most common dicotyledonous weeds producing the highest biomass in spring cereals were Chenopodium album L., Galeopsis spp. L., Stellaria media (L.) Vill. and Lapsana communis L. The main grass weed was Elymus repens (L.) Gould. The average reduction of weed biomass by herbicide treatment was 75%. More reliable efficacy was obtained with herbicide mixtures than with MCPA alone.
Influence of glumes, soil and environmental conditions on germination of Ischaemum afrum (J.F. Gmel.) Dandy seeds
Authors: TAYALLA O. E. , BABIKER A. G. T. , MANSI M. G. , BESHIR N. H. H.
Published: July 2006

Studies on the germination of Ischaemum afrum seeds showed that low temperature, presence of glumes and both low and excessive soil moisture contents were conducive to delayed and low germination. The inhibitory effect of the glumes was more pronounced in freshly harvested seeds. Germinability of seeds on the soil surface was poor, but shallow burial in soil increased germination.
Dynamique de quelques dicotylédones adventices en culture de céréale. I. Relation flore levée—stock semencier
Authors: INRA P. DEBAEKE
Published: July 2006

La connaissance du rapport flore levée/stock de semences du sol est nécessaire à la prévision des infestations de mauvaises herbes. Des travaux antérieurs ont montré que ce rapport (ou taux de levée) est en moyenne faible mais pourtant variable entre espèces, années et sites expérimentaux. Cette étude tente d'expliquer la variabilityé du taux de levée annuel, pour quelques dicotylédones à stock assez persistant, au sein de cultures de céréales d'hiver ou de printemps, labourées ou non. La dynamique de la levée et le stock de semences viables sont enregistrées à partir de populations adventices naturelles au cours de deux années successives et sur 26 parcelles cultivées, appartenant an champ d'essai de Grignon, situé dans le Bassin Parisien. Les résultats montrent une relative constance intra‐ et inter‐annuelle du taux de levée pour des conditions voisines d'implantation de la céréale. La variation résiduelle est expliquée pour une même espèce par la distribution verticale des semences dans la couche labouré et peut‐être par l'âge moyen du stock. La variabilityé inter‐spécifique du taux de levée est à relier à la taille de la semence, à la période de germination de l'espéce mais aussi au mode d'estimation de la viabilité des semences; cependant l'utilisation de la radiographie industrielle aux rayons X a permis de compenser l'insuffisance des tests de germination et de réduire partiellement cette variabilité. De très faibles taux de levée sont observés enfin en l'absence de labour. Un modèle statistique simple est proposé pour rendre compte de la variabilité de ce taux, pour la flore dicotylédone annuelle, en culture d'hiver labourée.
Analysis of growth and resource allocation
Authors: HUNT R.
Published: July 2006

At UCPE we are exploring high‐level, ecologically based models of growth and resource allocation in herbaceous plants, including weed species. In them, allocation is driven by variables from Plant Strategy Theory, such as below‐and above‐ground‘environmental stress'. A‘hyperbolic’model is described in which the allocation of resources into above‐and below‐ground plant parts is jointly controlled by (i) the absolute amounts of below‐and above‐ground stress that the plant‘perceives'; (ii) the ratio of below‐ground to above‐ground stress; and (iii) by the maximum growth potential of the plant itself. The inputs to the model are the fraction of its maximum potential that the plant attains and its root‐shoot allometric growth coefficient. The outputs from the model are indices of the above‐and below‐ground stresses‘perceived’by the plant. The latter arc otherwise particularly difficult to estimate when growth and allocation are being controlled simultaneously by several suboptimal environmental variables, as happens in many crop weed systems.
Quantitative determination of broomrape (Orobanche spp.) seeds in vetch seeds
Authors: JACOBSOHN R. , MARCUS RUTH
Published: July 2006

Summary: Résumé: Zusammenfassung

A method was developed by which the presence of broomrape (Orobanche spp.) seeds in vetch seeds was determined quantitatively. The broomrape seeds are washed out of the vetch seeds by a combination of two sieves. The vetch seeds remain on the top sieve and the broomrape seeds are collected on the lower sieve with square openings of 100 μm, which do not permit passage of the broomrape seeds. An appropriate statistical method for estimating the true mean number of broomrape seeds per sample in a large vetch seeds lot is presented and discussed.

Détermination quantitative des graines d' orobanche dans des graines de vesce.

Une méthode permettant de dénombrer la présence de graines d'orobanche dans un lot de graines de vesce a été mise au point. Les graines d'orobanche sont séparées de celles de vesce par une succession de deux tamis. Les graines de vesce sont maintenues sur le tamis supérieur et les graines d'orobanche sont collectées sur le tamis le plus bas avec une maille de 100 μm qui ne permet pas le passage des graines d'orobanche. Une méthode statistique appropriée pour estimer la quantité réelle d'orobanches dans un grand lot de semences de vesce est présentée puis discutée.

Quantitative Bestimmung von Orobanche‐Samen in Wicken‐Saatgut

Es wurde eine Methode entwickelt, mit der Orobanche‐Samen in Wicken‐Saatgut quantitativ erfasst werden können. Zum Trennen der Samen wurden 2 Siebe verwendet, wobei die Wicken‐Samen im oberen, die Orobanche‐Samen im unteren mit einer Maschenweite von 100 μm gesammelt wurden. Eine statistische Methode für die Schätzung der Orobanche‐Samenmenge in grossen Wicken‐Saatgutpartien wurde vorgestellt und diskutiert.
Photosynthetic capacity of intact leaves of resistant and susceptible cultivars of Brassica napus L. to atrazine
Authors: van OORSCHOT J. L. P. , van LEEUWEN P. H.
Published: July 2006

The rate of photosynthesis in intact leaves attached to plants of an atrazine‐resistant cultivar of Brassica napus L. was compared with that in leaves of an atrazine‐susceptible, rather isogenic cultivar, in a number of irradiance series. The resistant cultivar had been obtained from the susceptible cultivar by crossing the resistant biotype of Brassica campestris L. with the susceptible cultivar of B. napus, and using the fourth back‐cross for comparison. At a natural CO2 concentration (360 cm3 m−3) the rate of photosynthesis of leaves of the atrazine‐resistant cultivar was significantly (17–21%) less than that of leaves of the susceptible cultivar, over the whole range of irradiances up to 250 W m−2 At the enriched CO2 concentration of 1500 cm−3 m−3 this reduction in rate amounted to 9–12%.
Effect of time of weed removal on growth and yield of potato
Authors: THAKRAL K. K. , PANDITA M. L. , KHURANA S. C. , KALLOO G.
Published: July 2006

The effects of weed removal at five dates after planting the crop were examined and compared with weed‐free and unweeded controls. The results revealed that the total weed population increased up to 6 weeks after planting and then decreased drastically in both the years. Total dry weight of weeds (at weeding and at haulm‐cutting) was greatest in the unweeded control, followed by weeding at 10 weeks after planting. In both years, maximum yield was obtained where plots were kept weed‐free, followed by weeding at 4 and 6 weeks after planting. The remaining treatments, including weeding at 2 weeks after planting, resulted in significant reductions in tuber yield. In unweeded control plots the tuber yield of potato was reduced by 40–43%.
Absorption, translocation and metabolism of pyridate in a tolerant crop (Zea mays) and two susceptible weeds (Polygonum lapathifolium L. and Chenopodium album L.)
Authors: GAILLARDON P. , GUICHAOUA J. C. , GASQUEZ J. , SCALLA R.
Published: July 2006

Absorption, translocation and metabolism of 14C‐pyridate were compared in tolerant maize. moderately susceptible Polygonum lapathifolium and susceptible Chenopodium album. Foliar absorption was limited in all species, but comparatively higher penetration levels were observed in younger leaves of dicotyledonous species. The absorbed radioactivity was not very mobile and translocation appeared mainly sym‐plastic. Herbicide selectivity could not be explained on the basis of absorption and transport. Chenopodium and P. lapathifolium degraded pyridate and formed unstable water‐soluble conjugates that easily released a phytotoxic metabolite. By contrast, more stable unidentified water‐soluble metabolites were found in maize. That metabolic difference could explain the selectivity of pyridate.
Relative importance of crop seed, manure and irrigation water as sources of weed infestation
Authors: DASTGHEIB F.
Published: July 2006

Three possible sources of field contamination by weed seeds were studied during 1983–86 in two areas of Fars Province, Iran. These sources were crop seed, irrigation water and sheep manure. Manure was found to be the most important, adding almost 10 million seeds ha−1 at each application. Farmer‐saved seed of wheat, the main crop of the area, added an average of 182,000 weed seeds ha−1. Irrigation water added no more than 120 seeds ha−1, but was able to carry seeds over long distances without affecting viability.
Interaction between diclofop‐methyl and 2,4‐D in wild oat (Avena fatua L.) and cultivated oat (Avena sativa L.), and fate of diclofop‐methyl in cultivated oat
Authors: KAFIZ B. , CAUSSANEL J. P. , SCALLA R. , GAILLARDON P.
Published: July 2006

Influence of 2,4‐D on toxicity of diclofop‐methyl to Avena sativa (cv. Selma) and Arena fatua at 2·5 leaf stage has been evaluated under controlled conditions. Effects of 2,4‐D on the fate of diclofop‐methyl in cultivated oat have also been studied. Mixture with 2,4‐D reduced the toxicity of diclofop‐methyl to both species. When applied immediately after diclofop‐methyl treatment, 2,4‐D still reduced herbicide toxicity to wild oat. This reduction was smaller in cultivated oat. and was only observed at higher phytotoxicity. No interaction was observed when a 10‐day period separated the two applications. In mixture, 2,4‐D enhanced diclofop‐methyl penetration and diclofop acid conjugation in cultivated oat, and it slightly increased conjugation when applied separately. None of these effects clearly explain the reduction of diclofop‐methyl toxicity by 2, 4‐D in cultivated oat. Other processes are possibly involved and could be connected with the site of action of diclofop‐methyl.
Effect of eight herbicides from five different chemical groups on nitrogen fixation and grain yield in Lupinus albus L. grown in semi‐arid zones
Authors: POZUELO J. M. , FERNANDEZ‐PASCUAL M. , LUCAS M. M. , DE FELIPE M. R.
Published: July 2006

Summary. The effects of five different chemical groups of herbicides: dinitroanilines, 1, 3, 5‐triazines, 1, 2, 4‐triazinones, α‐chloroacetamides and carbamates on N2‐fixation & yield in Lupinus were compared. Cyanazine, simazine and trifluralin caused a significant increase in acetylene reduction activity (ARA), whereas the rest had no effect on ARA. Cyanazine and simazine significantly increased the grain yield and the weight of lupin seeds. The percentage of nitrogen in the seeds was significantly increased by cyanazine. An inventory of the weeds resistant to the herbicides in the treated subplots was also carried out. The dinitroaniline group mainly controlled Galium tricorne, Lolium multiflorum, Papaver rhoeas, and Avena sterilis whereas the 1, 3, 5‐triazine and dinitroaniline herbicides. Carbamates and α‐chloroacetamides were less effective Papaver rhoeas, Scandix pecten‐veneris and Avena sterilis. Avena sterilis was controlled by both triazine and dinitro‐aniline herbicides. Carbamates and α‐chloroacetamides were less effective on the weeds growing with the lupinus plants.
Weed management strategies for the control of Rottboellia cochinchinensis in maize in Trinidad
Authors: BRIDGEMOHAN P. , BRATHWAITE R. A. I.
Published: July 2006

Summary. A weed management strategy for the control of Rottboellia cochinchinensis (Lour.) W.D. Clayton in maize, based on reducing the level of spikelet germination from the seedbank and reducing the intensity of weed‐crop interference, was conducted over two seasons. The management practices evaluated included chemical control (atrazine, metolachlor, pendimethalin, EPTC), cultural control (straw mulch), mechanical control (inter‐row cultivation) and biological control (living mulch). The results indicated that the various management practices had no effect on the growth and development of the crop but significantly affected the weed. The pendimethalin (1°5 kg a.i. ha−1) and inter‐row cultivation (14 and 28 days after planting) treatments gave satisfactory control of the weed in the crop over the duration of the critical period of weed competition. All other treatments were ineffective. All management practices made significant contributions to the weed seedbank, thus ensuring the predominance of the weed.
The influence of the herbicide mefenacet on cell division and cell enlargement in plants
Authors: HESS F. D. , HOLMSEN J. D. , FEDTKE C.
Published: July 2006

The herbicide mefenacet has recently been developed for pre–emergence control of graminaceous and some dicotyledonous weeds in rice. Whereas mefenacet is known to inhibit root growth, its effect on the components of growth, cell division and cell enlargement, have not been determined. The purpose of this study was to evaluate the influence of mefenacet on growth, cell enlargement and cell division in Chlamydomonas (a green alga) and oats. Cell division in Chlamydomonas was completely inhibited and cell enlargement was inhibited by an average of 18% during the first cell cycle period when cells were treated with 6–7 μM mefenacet. The rate of oat root growth in sand culture between 12 and 24 h after initiation of treatment was reduced 90% at 10 μM mefenacet. Cell enlargement of oat coleoptile sections in culture solution was inhibited 25% at 10 μM. Mefenacet inhibited mitotic entry rather than disrupted the mitotic sequence. Cell division in oat roots was inhibited 54% by 10 μM mefenacet. This shows cell division inhibition occurs in G1, S, or G2 of the cell cycle. The action of mefenacet is most like that of the chloroacetamides among the herbicide classes known to inhibit growth.
The effect of chemical and heat treatments on germination of Commelina benghalensis L. aerial seeds
Authors: KIM S. Y. , DE DATTA S. K. , MERCADO B. L.
Published: July 2006

The effects of concentrated sulphuric acid, dry heat, hot water and NaOCl treatments on the germinability of dormant large and small aerial Commelina benghalensis L. seeds were evaluated. Concentrated sulphuric acid and NaOCl treatments were more effective than the dry heat and hot water treatments in breaking the dormancy of C. benghalensis aerial seeds. Treatments increased germination of both seed types due to its effect on the seed coat integrity. A scanning electron microscope revealed that changes as a result of scarification occurred in the hilum region of the seed and in the seed coat surface. The large aerial seeds were affected by all treatments more than the small aerial seeds. Difference in germinability between the two seed types was related to the difference in their seed vigour.
Output and dispersal of propagules of Carduus acanthoides L
Authors: FELDMAN SUSANA R. , LEWIS J. P.
Published: July 2006

Propagules of Carduus acanthoides are pappus‐bearing achenes. Flower production, potential achene output, seedbank and wind dispersal of propagules of Carduus acanthoides were analysed. Flower production was measured in four cohorts in 1986–87 and three cohorts the following reproductive season, when the potential achene output was estimated. Achene output was very large in all cases but early cohorts had a longer fruiting period and produced more flowers and fruits per plant. The seedbank was small and results from autumn and spring samples showed a low seed persistence in soil. In laboratory experiments greater landing and dispersion distances were reached at higher wind speeds, the major wind effect being that on the movement of propagules after landing. Barriers simulating vegetation almost completely stopped this movement after landing and the final distances reached were almost the same at all wind speeds. In field experiments achenes recovered in seed traps and seedling emergence show the same pattern of distribution around the parent plant. The implication of these results for the behaviour of thistle populations are discussed.
Growth of Emex australis out‐of‐season: relevance to biological control of an annual weed
Authors: PANETTA F. D.
Published: July 2006

Populations of the winter annual Emex australis were established by initiating irrigation at monthly intervals, beginning in mid‐summer. Natural seedling densities varied from 100 m−2 when irrigation was begun during late January to almost 700 m−2 when it began at the end of March. Densities were increased by sowing non‐dormant seeds, but most sown seeds became dormant when introduced before autumn. Plants which emerged after the earliest irrigation grew most rapidly. Those originating from the latest irrigation grew most slowly, in association with vigorous growth of other annual species. Because it minimizes interspecific competition, early commencement of irrigation, coupled with sowings of nondormant seeds is the best method for establishing E. australis during summer. Maintenance of such populations may enhance the persistence of non‐aestivating biological control agents and/or boost their numbers prior to the onset of mass germination. This approach could also prove useful for other winter annuals which are targeted for biological control.
Utilisation de l'isoproturon seul ou en association avec d'autres matières actives, en post‐levée en hiver et au printemps sur blé et orge d'hiver
Authors: BERGER B. , HEITEFUSS R.
Published: July 2006

In einem zweijährigen Versuch auf zwei Standorten (Sand‐ und Lehmboden) wurde Isoproturon allein und in Kombination mit Dinoseb‐acetat und Bifenox zum Nachauflauf Winter (NA‐W) Termin und zum Nachauflauf Frühjahr (NA‐F) Termin in Wintergerste und Winterweizen eingesetzt. Obwohl nach einer Nachauflauf‐Winter Behandlung die anfänglichen Herbizidbelastungen im Böden höher waren, sind nach unseren Ergebnissen im Vergleich zu einer Nachauflauf‐Frühjahr Behandlung am Ende der Vegetationsperiode keine erhöhten Rückstände von Isoproturon zu erwarten. Die DT‐50‐Werte von Isoproturon in den beiden Versuchsjahren und Böden lagen zwischen 12 und 33 Tagen, die DT‐90‐Werte schwankten im Bereich von 34 bis 68 Tagen. Ein Einfluß der mit Isoproturon kombinierten Wirkstoffe auf dessen Abbau im Boden war nicht festzustellen. Eine bessere Unkrautwirkung der NA‐W‐Behandlung führte besonders bei starker Verunkrautung zu höheren Erträgen.
Untersuchungen der Dynamik einer Unkrautgemeinschaft: III. Der langfristige Einfluß der Bodenbearbeitung auf die Artenzusammensetzung des Samenvorrats
Authors: DESSAINT F. , CHADOEUF R. , BARRALIS G.
Published: July 2006

L'évolution de la composition spécifique du stock semencier a été suivie pendant huit années sur quatre parcelles expérimentales différant par le type de travail du sol (profond ou superficiel) et de désherbage chimique (absent ou sélectif). Nos résultats montrent que la composition spécifique du stock n'est pas modifiée sur les parcelles désherbées et que seuls des change‐merits d'ordre quantitatif interviennent au sein de la communauté: certaines espèces, comme Euphorbia exigua et Anagallis arvensis, augmentent ainsi leurs dominances dans le stock sans accroissement de leurs abondances. A l'opposé, sur les parcelles non désherbées, on observe des modifications qualitatives et quantitatives de la composition spécifique avec l'arrivée d'espèces ‘opportunistes’, comme Thlaspi arvense et Sinapis arvensis, qui augmentent considérablement leurs abondances alors qu'elles étaient pratiquement absentes du stock en début de suivi. Le type de travail du sol nuance un peu ces phénomènes en permettant une meilleure homogénéisation sur la couche arable des apports annuels et du stock existant.
Einfluß der Bestandesdichte und der Konkurrenzdauer von Solanum nigrum L. auf die Tomate bet Direktsaat
Authors: CAUSSANEL J. P. , BRANTHÔME X. , MAILLET J. , CARTERON A.
Published: July 2006

Les effets de la densité et de la période de concurrence de Solanum nigrum L. ont été déterminés dans des cultures de tomate en semis direct, en relation avec les techniques de désherbage utilisées dans le Sud‐Est de la France. Des S. nigrum levant après une application de diquat au stade 2–3 feuilles de la plante cultivée et éclaircies à de faibles densites (entre 0 et 12,8 plantes par m2) au stade 5–6 feuilles de la plante cultivée, ont entraîné des pertes significatives de rendement lorsqu'elles concurrençaient la culture jusqu'à la récolte. Les rendements de tomate ont subi de plus faibles réductions lorsque de telles densités étaient présentes jusqu'au début de la floraison. Les courbes de régression ‘rendement de la culture × densité de la mauvaise herbe’ ont été différentes selon les conditions climatiques de l'année affectant la date de semis et la croissance des plantes; une comparaison entre années a été faite d'après la relation l'rendement de la culture × rapport de biomasses adventice/plante cultivée. Des interactions significatives entre la densite de l'adventice et sa période de concurrence ont été constatées pour quelques variables de rendement (fruits verts) ou composantes du rendement (poids moyen d'un fruit rouge). Dans le cas d'un semis direct tardif et pour de faibles densités de S. nigrum en concurrence avec la culture, deux désherbages au stade 5–6 feuilles et debut floraison ont été suffisants pour empêcher le rendement de diminuer.
Fate of fluroxypyr in soil
Authors: LEHMANN R. G. , MILLER J. R. , LASKOWSKI D. A.
Published: July 2006

Batch adsorption Koc values of fluroxypyr‐methylheptyl ester (20000 1kg−1) and fluroxypyr (74 1kg−1) indicate increased mobility after hydrolysis of the ester to fluroxypyr. After 1 to 2 weeks incubation time in four soils, desorption Koc values of fluroxypyr were 100‐200 1kg−1 but increased to 400‐700 1kg−1 after 8 weeks. The increase in desorption Koc was related to incubation time and not to concentration, and it was interpreted as an entrapment of the fluroxypyr within the soil organic matter. Similar increases in desorption Koc with incubation time were noticed for pyridinol and methoxypyridine metabolites of fluroxypyr. Koc values also increased along the metabolic sequence fluroxypyr/pyridinol/methoxypyridine, with maximum Koc values of 3000‐4000 1 kg−1 for the methoxypyridine metabolite. Hence mobility of the fluroxypyr aromatic ring strongly decreases with increased residence time in the soil.