bluuebunny/crossref_metadata_2025 huggingface dataset:
Phenology and growth of Orobanche crenata Forsk (broomrape) in four legume crops
Authors: ARJONA‐BERRAL A. , MESA‐GARCIA J. , GARCIA‐TORRES L.
Published: July 2006

Studies were conducted in the field in 2 years comparing the phenology and growth of Orobanche crenata (Forsk) (crenate broomrape) in lentils (Lens esculenta L.) cv. Castellana, peas (Pisum sativum L.) cv. Orix, vetch (Vicia sativa L.) cv. comun and broadbean (Vicia faba L. cv. Alameda. First attachment of O. crenata to these crops took place 9–14 weeks after mid‐November planting and earlier after later plantings, Differences in the first O. crenata attachment dates and in the duration of the underground growth period of O. crenata were much greater between years for any given crop than between crops in a given year: both attributes were apparently affected more by seasonal climatic conditions than by crop species, Furthermore, there was no consistent relationship found between crop growth stages and time after first attachment of the parante. This occurred in lentils and vetch while they were vegetative, in peas at late vegetative‐early flowering stages, and at widely varying growth stages in broadbean, depending on planting dates and years. The maximum number of O. crenata plants successfully attached to each individual crop plant decreased in the order: peas > broadbean > lentil > vetch, with 21, 14, 10 and 8 per plant, respectively, averaged over the two seasons. Similarly, plant parasites: host dry weight ratio were 1.0, 0.7, 0.3 and 0.2 For each of these crops, respectively.
Seed detachment in Avena fatua L.
Authors: YEUNG E. C. , CHINNAPPA C. C. , CHEN F. S. C.
Published: July 2006

Summary: Résumé: Zusammenfassung

Soon after the development of the inflorescence and prior to anthesis, the future detachment point of the floret of Avena fatua L. is formed. This zone is denoted initially by files of cells that will eventually become the future break‐point where a scar is formed. The edge of the future scar (at the articulation zone) is composed of small cells, which, despite the retention of prominent primary wall material, have highly lignified secondary walls. The grain will break from the rachilla in the region of these small cells. The centre of the future scar is composed mainly of thin‐walled parenchyma cells with large intercellular air spaces. Underneath the future break‐point, the stalk is composed of a solid core of vascular elements and lignified cells. These features are absent in the cultivated out (Avena sativa L.).

Le détachement de graines d' Avena fatua L.

Sitôt après le développement de l'inflorescence avant l'anthèse, le point de détachement de la fleur d'Avenu fatua L. est formé. Cette zone est marquée au départ par des rangées de cellules qui deviendront le futur point d'abscission où une cicatrice se forme. Le bord de la future cicatrice (à la zone d'articulation) est composé de petites cellules qui. malgré le maintien d'une première barrière saillante, ont lignifié des parois secondaires. Le centre de la future cicatrice est composé principalement de parenchyme à cloisons fines avec des espaces intercellulaires larges. A proximité du futur point d'abscission, la tige est composée d'un noyau solide d'éléments vasculaires et de cellules lignifiées. Les caractéristiques énoncées ci‐dessus sont absentes chez l'avoine cultivée (Avenu sativa L.).

Ueber die Ablösung der Samen bei Avena fatua L.

Bei Avena fatua L. wird bald nach der Entwicklung der Infloreszenzen, aber vor ihrer vollen Ausbildung, die spätere Ablösungsstelle der Blüte angelegt. Diese Zone ist anfänglich durch Zellreihen gekenntzeichnet, welche sehliesslich die Bruchstelle darstellen und wo eine Narbe gebildet wird. Der Rand der zukünftigen Narbe besteht aus kleinen Zellen, welche, obwohl noch auflällig viel primäres Zellwandmaterial enthaltend, stark verholzte sckundäre Zellwände aufweisen. Der Same bricht im Bereiche dieser kleinen Zellen aus der Aehrchenachse (Rachilla). Das Zentrum der zukünftigen Abbruchnarbe besteht aus dünn wandigem Parenchym mit grossen Interzellularräumen. Unterhalb der späteren Abbruchstelle ist die Aehrchenachse aus einem dichten Gewebe aus Gefässelementen und verholzten Zellen aufgebaut. Beim Kulturhafer (Avena sativa L.) fehlen die oben beschriebenen Elemente.
Spread of proso millet (Panicum miliaceum L.) in Ontario, Canada. I. Rate of spread and crop susceptibility
Authors: McCANNY S. J. , BOUGH MARGUERITE , CAVERS P. B.
Published: July 2006

The infestations of two biotypes of Panicum miliaceum L. were monitored over a 5‐year period (1981–1985) as they occurred in two townships in southwestern Ontario, Canada. On average, 16·5% of the cultivated fields in Hullett township were infested with the black‐seeded biotype while 12·9% of the fields in North Norwich township were infested with the golden‐seeded biotype. Neither population showed clear signs of increasing. The two biotypes were similar in their ability to persist as adult infestations. The black‐seeded biotype showed a greater potential for colonizing uninfested fields. The crops grown in this region showed different susceptibilities to infestation by P. miliaceum. Corn (maize) fields were susceptible while most grain fields were resistant to infestation. White beans were susceptible to infestation by the black‐seeded biotype. Wheat and oat crops were more resistant to infestation by the golden‐seeded biotype than to those of the black‐seeded biotype.
Carrot microtubules are dinitroaniline resistant. I. Cytological and cross‐resistance studies
Authors: VAUGHAN M. A. , VAUGHN K. C.
Published: July 2006

Treatment of both tolerant and susceptible species with dinitroaniline herbicides results in root swelling typical of mitotic disrupters, however, no root swelling was observed in carrots treated with saturated solutions of all the dinitroaniline herbicides tested, with the exception of oryzalin treatments at ≥ 10−5 M. These levels of treatment are 100–1000 times the levels that caused root‐tip swelling, even in tolerant plants. This properly classifies carrot as dinitroaniline‐resistant rather than merely tolerant. Cross‐resistance was noted to the structurally related mitotic disrupter, hexanitrodiphenylamine, and to the structurally unrelated herbicide, amiprophos‐methyl. No resistance was noted to a number of other mitotic‐disrupting herbicides. Both immunofluorescence and electron microscopy indicate that the microtubules of carrot roots were unaffected by dinitroaniline treatment. All organized microtubule configurations (cortical, pre‐prophase bands, spindle, and phragmoplast) were observed in the treated material.
Ecological implications of traditional weeding and other imposed weeding regimes under slash‐and‐burn agriculture (jhum) in northeastern India
Authors: SWAMY P. S. , RAMAKRISHNAN P. S.
Published: July 2006

Traditional weeding in slash‐and‐burn agriculture (jhum) in northeastern India involves the retention of a certain proportion of weed biomass in situ. By comparing this weed management practice with total weeding and no weeding, the economic and ecological efficiency of this agroecosystem has been assessed. It is concluded that traditional weeding has little effect on the yield potential of the crop mixture compared with total weeding but it could lead to conservation of soil resources by up to about 20%. Indeed, harvested weed biomass put back into the system is an efficient way of recycling resources under stress.
Les principales mauvaises herbes des vergers dans la région maritime de Syrie
Authors: SOUFI Z.
Published: July 2006

A partir de 51 relevés effectués au printemps 86 dans les vergers de la région maritime syrienne, une liste exhaustive de 370 espèces de mauvaises herbes a étéétablie. Les notions d'abondance et de fréquence ont permis de dégager 54 espèces considérées comme les principales. Plusieurs aspects concernant ces principales mauvaises herbes sont représentés: analyse floristique, spectre biologiques et appartenance biogéographique.
Multivariate analysis in weed science
Authors: POST B. J.
Published: July 2006

Weed species in arable ecosystems are adapted to the conditions produced by agricultural management. In order to give preventive and curative guidelines to weed management one needs to predict the composition of the weed vegetation after certain (soil) cultivation measures. Dormancy mechanisms of seeds in the seedbank and the environmental conditions in the furrow before and after cultivation are usually such that the vegetation composition is heterogeneous. Multivariate analyses enable us to describe and classify weed vegetation and to analyse its relationship to environmental factors.
Experimental methods in plant competition research in crop‐weed systems
Authors: CONNOLLY J.
Published: July 2006

The implications of recent studies on the inappropriatness of replacement series and additive methods in competition studies, and some possible alternatives, are discussed in the context of weed research, Replacement series are usually inadequate to assess competitive interactions and can be misleading. In particular they may be biased in favour of the larger species. Many of the criticisms of replacement series also apply to additive experiments. Response models relating yield per individual to the densities of the species in the mixture provide methodology for answering many questions about mixtures. This paper proposes a framework for using these models to: (i) measure the effect of weed species on yield per individual and yield per unit area for the crop and weed species; (ii) develop methods of biological control of weeds both within a seaons and over seasons, based on the interference between crop and weed species and the population biology of the weed species; (iii) establish a cost‐benefit analysis of certain of the biological weed‐control programmes. The inclusion of the effect of relative emergence time and management practices in response models is considered as well as experimental design for crop‐weed experiments.
Modelling the effects of weeds on crop production
Authors: KROPFF M. J.
Published: July 2006

In most quantitative studies on interplant competition, static regression models are used to describe experimental data. However, the generality of these models is limited. More mechanistic models for interplant competition, which simulate growth and production of species in mixtures on the basis of the underlying physiological processes, have been developed in the past decade. Recently, simulation models for competition between species for light and water were improved and a detailed version was developed for sugarbeet and fat hen (Chenopodium album L.). The model was validated with data sets of five field experiments, in which the effect of fat hen on sugarbeet production was analysed. About 98% of the variation in yield loss between the experiments (which ranged from –6 to 96%) could be explained with the model. Further analysis with the model showed that the period between crop and weed emergence was the main factor causing differences in yield loss between the experiments. Sensitivity analysis showed a strong interaction between the effect of the variables weed density and the period between crop and weed emergence on yield reduction. Different quantitative approaches to crop‐weed competition are discussed in view of their practical applicability. Simulations of experiments, where both the weed density and the period between crop and weed emergence were varied over a wide range, showed a close relation between relative leaf cover of the weeds shortly after crop emergence and yield loss. This relation indicates that relative leaf cover of the weeds accounts for both the effect of weed density and the period between crop and weed emergence. This relation has the potential to be developed into a powerful tool for weed‐control advisory systems.
Effects of tropical weeds on yield in white yam (Dioscorea rotundata Poir)
Authors: UNAMMA R. P. A. , AKOBUNDU I. O.
Published: July 2006

The effects of tropical weeds on the yield of while yam were studied outdoors in wooden boxes. When the foliage and roots of weeds were in physical contact with the crop until harvest (full interference), tuber yield of yam was reduced by 76–79% of that obtained under weed‐free conditions over 3 years of study. When there was no physical contact between roots of crop and weeds, the leachate from the weed zone caused tuber yield reductions of 42, 40 and 38% in 1978, 1979 and 1980, respectively, when it was applied to the yam zone. This leachate also reduced leaf area index (LAI) in the yam crop but the adverse effects on yam root and shoot biomass were less pronounced. This technique made it possible to separate competitive interference from allelopathic interference of tropical weeds with the yam crop.
Chemical control of nodding thistle (Carduus nutans L.) in New Zealand pastures
Authors: POPAY A. I. , BUTLER J. H. , MEEKLAH F. A.
Published: July 2006

Broadcast sprays of several herbicides were applied at different times of the year at several sites in Hawkes Bay, Canterbury and Otago. For good thistle control, date of application was more important than types of herbicide. In Hawkes Bay, applications made in April, May and June tended to be the most effective. Under slightly cooler Canterbury conditions, April, September and October were the best application dates. In the Otago trials, spring emergence of thistle seedlings meant that the most consistent results came from September or October applications. At all sites, applications made in July or August were relatively ineffective, probably because of low winter temperatures and slow thistle growth rates. MCPA (potassium salt) at 1·0 kg ha−1 was the standard herbicide used in all experiments. MCPA at 0·5 kg ha−1, MCPB (sodium salt) at 0·5 and 1·0 kg ha−1 and 2,4‐D at 0·5 kg ha−1 did not kill as many thistles as MCPA at 1·0 kg ha−1. MCPA at 1·5 kg ha−1 and MCPB (butyl) ester + clopyralid at 0·5 + 0·015 or 1·0+0·03 kg ha−1 gave consistently better control than MCPA at 1·0 kg ha−1 2,4‐D at 1·0 or 1·5 kg ha−1, MCPB at 1·5 or 2·0 kg ha−1, and MCPA + MCPB at 0·33 + 1·0 or 0·67 + 0·5 kg ha−1 gave results very similar to MCPA at 1 kg ha−1. Thistle control varied between sites and years. Some of the variation may have been due to different proportions of first and second year thistles present at spraying, and to variation in genetically determined herbicide susceptibility. Chemical control of thistles was short term only, because of dormant seeds in the soil.
Field persistence of chlorsulfuron and DPX‐L5300 in relation to rotational crops
Authors: ELEFTHEROHORINOS I. G. , KOTOULA‐SYKA ELENI
Published: July 2006

A pot bioassay procedure, based on root growth of pre‐germinated maize was used to study residual phytotoxicity of chlorsulfuron and DPX‐L5300 methyl‐([4‐methoxy‐6‐methyl‐1,3,5‐triazin‐2‐yl(methyl) carbamoyl]sulphamoyl)benzoate under field conditions. The results indicate that residual bioactivity of both herbicides, applied either pre‐or post‐emergence at 5, 10, 20 and 40 g a.i. ha−1, was increased with increasing rate of application. Chlorsulfuron persisted longer than DPX‐L5300, and both herbicides, when applied pre‐emergence, persisted longer than when applied post‐emergence. Pot bioassay did not detect any residues eight months after either application. Maize and sunflower, planted as rotational field crops eight months after pre‐emergence application, were not injured by either herbicide. Also, these crops were not affected when planted four months after post‐emergence application of any of the DPX‐L5300 rates or 5 or 10 g a.i. ha−1 of chlorsulfuron, but their fresh weight was significantly reduced where 20 or 40 g a.i. ha−1 of chlorsulfuron were applied.
Physiological studies of mecoprop‐resistance in chickweed (Stellaria media L.)
Authors: BARNWELL P , COBB A. H.
Published: July 2006

Glasshouse experiments have confirmed that resistance to mecoprop is present in a biotype of Stellaria media. Resistant plants were less vigorous than the susceptible population and ED50 values were calculated as 3·92 and 0·18 kg a.i. ha−1 respectively. The physiological basis of mecoprop resistance was investigated by studying the responses of each biotype in two experimental systems, namely explant stem elongation and ethylene evolution. These studies have discounted differential ethylene evolution as the basis of resistance but have indicated altered elongation growth in resistant plants. This observation suggests the possibility of reduced mecoprop binding in resistant plants, although the role of mecoprop metabolism remains to be elucidated.
Role of temperature in regulating timing of germination in soil seed reserves of Thlaspi arvense L.
Authors: BASKIN J. M. , BASKIN CAROL C.
Published: July 2006

Summary. Most freshly‐matured seeds of Thlaspi arvense L. (Brassicaceae) were dormant at maturity in May. Seeds sown on soil germinated in autumn and spring, but mostly in autumn. Buried seeds exhumed at monthly intervals and tested in light and darkness over a range of thermoperiods exhibited annual dormancy/non‐dormancy cycles. However, the dormant period was short, usually only in April, but sometimes May, and in some years 1–6% of the seeds remained conditionally dormant. After‐ripening occurred during summer, and seeds were non‐dormant during autumn. Seeds entered conditional dormancy in winter and dormancy in late winter or early spring. When buried dormant seeds were kept at 25/15, 30/15 or 35/20°C for 12 weeks, they gained the ability to germinate to 95–100% at 15/6, 20/10, 25/15, 30/15 and 35/20°C. After burial for 12 weeks at 15/6 and 20/10°C, seeds germinated to 80–100% at 15/6, 20/10 and 25/15°C. but to only 11–64% at 30/15 and 35/20°C. After 4 weeks at 5°C, initially‐dormant seeds germinated to 100% at all thermoperiods except 35/20°C, where only 15% of them germinated. However, after 18 weeks at 5°C, only 0–1% of the seeds germinated at all thermoperiods. Most non‐dormant seeds exposed to 1, 5 and 15/6°C for 16 weeks were induced into dormancy; 1–15% entered conditional dormancy and thus germinated only at 15/6, 20/10 and 25/15°C. This study indicates that seeds of winter annual plants of T. arvense are non‐dormant in autumn and enter dormancy in winter, while those from summer annuals are dormant in autumn and become non‐dormant during winter.
Apical dominance in the shoot and its possible rôle in the survival of Paspalum distichum L.
Authors: HSIAO A. I. , HUANG W. Z.
Published: July 2006

Summary. When sequential single‐node shoot segments (third to fifteenth node, counting from the apex) of the perennial grass weed Paspalum distichum L. were buried in soil, new shoot growth was significantly correlated with initial segment length. Growth from the youngest segment (third), which was about 2 cm long, was only half as great as that from segments 8 to 15, which were initially 2–3·5 times longer. When 14‐node shoot segments were buried in soil, the apical bud exerted a dominating influence on shoot emergence and new shoot growth of axillary buds. The degree of suppression increased gradually up to node 8 and then decreased as the distance from the apex increased. A similar result was obtained in these shoot segments following decapitation. However, the degrees and patterns of apical and bud dominance varied in shoots collected during different seasons and also in shoots with different node numbers, node position, cutting and chilling treatments. A possible role of apical and bud dominance in P. distichum in keeping aerial shocks in reserve under adverse conditions, thus providing a survival mechanism for this weed, is discussed.
A comparison of techniques for estimation of arable soil seedbanks and their relationship to weed flora
Authors: BALL D. A. , MILLER S. D.
Published: July 2006

Summary. Post harvest soil samples taken during the autumn of 1985 and 1986 were split and estimates made of the weed seedbank using two methods: (1) a physical separation of seed from the soil mineral fraction by a sieving/flotation procedure and (2) by placing soil in shallow containers in a greenhouse where seeds could germinate and be periodically counted over a period of eight months. Seedbank estimates derived from each procedure were analysed to determine the suitability of each technique for detecting treatment differences from an experiment evaluating tillage/herbicide effects on weed populations. Both techniques were suitable for determination of seedbank changes due to different tillage treatments and herbicide inputs. The two techniques also proved effective for detection of individual species in the seedbank and the two techniques provided comparable estimates of the relative density of individual weed species in the seedbank. Weed seedbank estimates obtained by the physical extraction procedure from the autumn 1985 soil samples were correlated with weed seedling counts made in the spring of 1986. In most cases, weed seedlings represented less than 10% of the number of seeds estimated by physical extraction the preceding autumn. Individual species seed estimates and subsequent weed counts were poorly correlated which indicated that the seed count estimates alone were poor predictors of weed flora.
Effects of formulation and environment on absorption and translocation of clopyralid in Cirsium arvense (L.) Scop. and Polygonum convolvulus L
Authors: KLOPPENBURG D. J. , HALL J. C.
Published: July 2006

The patterns of absorption and translocation of 14C clopyralid commercially formulated as the acid, monoethanolamine salt, potassium salt, 2‐ethylhexyl ester and 1 ‐decyl ester were compared in Cirsium arvense and Polygonum convolvulus grown under three environmental regimes. Plants were grown under a 35% or 65% RH regime in silica sand maintained at 33% w/w moisture or under a water stress regime at 65% RH. Approxi mately 26,39,86,93 and 100% of the applied 14C‐activity from the 2‐ethylhexyl ester, acid, monoethanolamine salt, 1‐decyl ester and potas sium salt, respectively, were recovered 72 h after application to glass cover slips placed in the growth room. However, loss of applied 14C‐activity after application of the five formulations to both plant species was significant only for the 2‐ethylhexyl ester. Regardless of environmental regime, the acid was the most readily absorbed formulation. In contrast to the acid, the salts and esters were less readily absorbed. When the data were expressed as a percentage of absorbed radioactivity, there was no significant difference in translocation when the acid, monoethanolamine salt and potassium salt were compared. However, significantly smaller quantities of the absorbed 2‐ethylhexyl and 1‐decyl ester were exported from the treated leaf. These results indicate that once absorbed, the esters do not readily partition out of the cuticle, whereas the acid and two salts move into the symplast for subsequent translocation. When the results of the three environmental regimes were compared, the absorption of the monoethanolamine and potas sium salts were greatly reduced under low humi dity or water stress, whereas the acid and esters were not affected.
Temperature effects on dormancy release and germination rate in Sorghum halepense (L.) Pers. seeds: a quantitative analysis
Authors: ARNOLD R. L. BENECH , GHERSA C. M. , SANCHEZ R. A. , INSAUSTI P.
Published: July 2006

Seed dormancy in Sorghum halepense is overcome by exposure to fluctuating temperatures and the effect is determined both by the diurnal amplitude and the maximum temperature. It was found that repeated cycles of particular regimes were additive, each cycle resulting in release from dormancy of a further proportion of the population. The range of regimes having this additive effect was wider in seeds which had after‐ripened in the soil during winter than in those which were freshly dispersed. The temperature‐dependent germination rate of seeds whose dormancy had been removed by the effect of fluctuating temperatures was analysed using a ‘thermal time’ approach, and estimates obtained of base and optimum temperatures and the required ‘thermal time’ for the germination of different fractions of the population. The results provide a basis for developing a model to predict seedling recruitment in the field using soil temperature data.
La resistance atix herbicides en relation avec la structure infraspecifique deChenopodium albumL
Authors: ARLT B. , JÜTTERSONKE K.
Published: July 2006

Zasammenfassung:

Chenopodium albumL. gehört zu den Un‐krautarten, bei denen sich Resistenz gegen Herbizide, vor allem Triazine, häufiger entwic‐kelt. Um eine frühzeitige Erkennung herbi‐zidresistenter Populationen zu ermöglichen, wurden die Beziehungen zwischen den Sippen der polymorphen Art und ihrer Reaktion auf Herbizide ermittelt. Als grundlegende Vor‐aussetzung mußte die bestehende infraspezi fische Systematik vonCh. albumL. ssp.albumvar.album (sensuAellen, 1960) kritisch unter‐sucht und eine neue Gliederung auf Grund der Ergebnisse mehrjähriger Kulturversuche vorge‐nommen werden. Die genetische Stabilität mehrerer Merkmale wurde überprüft und die Infloreszenzformen als grundlegendes Merkmal verwendet. Bei Tests auf die Herbizidemp‐findlichkeit der Sippen ergab sich eine größere Toleranz bzw. Resistenz gegen Triazine bei dem Taxon mit trugdoldig‐scheinrispigen In‐floreszenzen. Die seit 1985 in der DDR nachge‐wiesenen triazinresistenten Biotypen vonCh. albumaus landwirtschaftlichen Kulturen gehörten ebenfalls zu dieser Sippe. Die mitCh. albumoft gemeinsam vorkommende und sehr ähnliche ArtCh. suecicumJ. Murr war hochempfindlich gegen Triazine. Versuche zur Kreuzresistenz ergaben eine allgemeine Resistenz gegen Triazine und Chloridazon, während Methazol, Pyridate, Bentazon, Meto‐bromuron und Bromuron voll wirksam waren. Die Wirkung von Metribuzin erschien abge‐schwächt. Ebenso reduzierte die Kombination von Bromuron und Fenuron mit Triazinen den Bekampfungserfolg. Triazinresistente Biotypen vonCh. albumreagierten langsamur auf das insgesamt gut wirksame Bromuron als empfind‐liche Pflanzen.
The influence of temperature, humidity and simulated rain on the performance of thiameturon‐methyl
Authors: KUDSK P. , OLESEN T. , THONKE K. E.
Published: July 2006

The influence of temperature, humidity and simulated rain on thiameturon‐methyl activity was examined on white mustard (Sinapis albaL.) plants grown in controlled environment cabinets or in a glasshouse. The performance of thiameturon‐methyl was markedly improved with increasing temperature and humidity. Addition of a non‐ionic surfactant increased the activity of thiameturon‐methyl, reduced the in fluence of humidity on herbicide performance but had no effect on the influence of tempera ture on herbicide activity. Increasing the amount of simulated rain from 0.11 to 3 mm reduced the activity of thiameturon‐methyl. However, reduction in activity by 3 mm rain became less pronounced as the interval between herbicide application and rain treatment was in creased from 0.5 to 6 h. With a 6‐h interval 3 mm rain had little effect. Rain intensity was found only to have a minor influence on the rainfast‐ness of thiameturon‐methyl.
Untersuchungen der Dynamik einer Unkraut gemeinschaft: II. Der langfristige Einfluß der Bodenbearbeitung auf den Samen vorrat
Authors: DESSAINT F. , CHADOEUF R. , BARRALIS G.
Published: July 2006

L'évolution du potentiel semencier a été suivie pendant huit années sur quatre parcelles ex périmentales assolées (orge et pois de prin temps, blé d'hiver) différant par le type de travail du sol (profond ou superficiel) et de désherbage chimique (absent ou sélectif). Nos résultats montrent que la répartition verticale des semences dans le sol (exprimée en pour centage) n'est pas modifiée par le travail du sol pour les parcelles désherbées alors que des différences apparaissent dès la cinquième année pour les parcelles non désherbées. Globalement le stock semencier augment sur les parcelles non désherbées alors qu'il reste relativement stable sur les autres parcelles, cette augmenta tion étant plus importante sur la parcelle travaillée superficiellement. Néanmoins, une analyse plus détaillée de l'évolution des dénombrements selon trois niveaux d'enfouisse ment permet de nuancer ces observations et de définir trois types de comportement de l'évolu tion des semences dans la couche arable. Enfin, la richesse spécifique du potentiel semencier reste stable mais la structure de la commun auté se modifie par augmentation ou diminution de l'abondance de certaines espèces selon l'absence ou non de traitements herbicides.
EWRS‐Ringuntersuchung zur Bestimmung der Samenbank im Boden: I. Untersuchungen über die Beziehungen zwischen dem Mittelwert und der Varianz bei der Probenahme
Authors: DESSAINT F. , BARRALIS G. , BEURET E. , CAIXINHAS M. L. , POST B. J. , ZANIN G.
Published: July 2006

Le stock semencier des mauvaises herbes a été analysé dans le sol de cinq parcelles agdcoles assolées, situées dans des zones géographiques éloignées. Une étude de la relation entre la moyenne et la variance d'échantillonnage obtenue à partir de l'analyse des prélévements isolés ou regroupés en composites a montré que cette relation existait et qu'elle était du mêeme type sur les cinq parcelles. Elle correspond à une loi de Taylor pour laquelle on a: log(variance) = a+b log(moyenne).

Néanmoins, les droites de régression log (moyenne) ‐ log(variance) obtenues à partir des couples (moyenne; variance) fournis par les différentes espèces diffèrent selon les parcelles et à l'intérieur d'une même parcelle selon le nombre d'espèces retenues.

Le même type d'étude réalisée à partir de simulations sur des composites variant en taille et en nombre conduit aux memes conclusions.
Variation in MCPA‐resistance in Ranunculus acris L. subsp. acris and its correlation with historical exposure to MCPA
Authors: BOURDOT G. W. , HURRELL G. A. , SAVILLE D. J.
Published: July 2006

In seven field experiments in which the effect of MCPA on Ranunculus acris subsp. acris in dairy pastures in New Zealand was studied, control varied between sites from 93% to 11% reduction in ground cover. To determine if the populations varied in resistance to MCPA, seedling progeny were sprayed with a range of doses of MCPA in a glasshouse. The LD50 values ranged from 0.36 kg MCPA ha−1 to 1.5 kg MCPA ha−1 confirming the existence of genetic variability in resistance between the populations. Correlations between the LD50 values and the control of the populations in the field, suggested that the differences in resistance contributed to the differences in control. A correlation between the LD50 values and historical exposures of the populations to MCPA suggested that selection for resistance had occurred. No evidence of a difference in competitive ability between the least and the most susceptible biotypes was detected, suggesting that resistance would not decline if spraying ceased.
A replacement series evaluation of competition between velvetleaf (Abutilon theophrasti) and soybean (Glycine max)
Authors: AKEY W. C. , JURIK T. W. , DEKKER J.
Published: July 2006

We examined relative competition abilities of velvetleaf (Abutilon theophrasti) and soybean (Glycine max) grown in a replacement series near Ames, Iowa, U.S.A. in 1986 and 1987. Relative above ground dry weight of soybean in mixtures was higher than expected from mono culture values early in the growing season but lower than expected later in the season, whereas velvetleaf had higher than expected values later in the season. Velvetleaf depressed seed yield of soybean in all mixtures; relative seed yield of velvetleaf was greater in all mixtures than in monoculture. Relative growth rate (RGR), leaf area ratio (LAR) and net assimilation rate (NAR) of soybean did not differ significantly among mixtures and generally decreased over the growing season. Velvetleaf exhibited no consistent differences among mixtures in RGR, LAR, and NAR. Net assimilation rate of velvetleaf was constant over most of the growing season. Relative growth rate and LAR of velvetleaf were highest early in the season and then progressively declined. Velvetleaf had higher NAR and higher RGR than soybean early in the season; LAR of velvetleaf was lower than LAR of soybean over most of the season. Velvetleaf and soybean did not significantly interfere with each other early in the growing season, but velvetleaf gained resources at the expense of soybean during the middle and later parts of the season.
Dégradation chimique ou microbiologique des sulfonylurées dans le sol. II. Cas du metsulfuron méthyle
Authors: VEGA D. , BASTIDE J. , POULAIN C.
Published: July 2006

Résumé: Summary: Zusammenfassung

La vitesse de dégradation du metsulfuron méthyle a étéétudiée dans un sol sablolimoneux en faisant varier différents paramètres: concentration, température, stérilisation du sol et réinoculation par du sol. Cette vitesse ne depend pas de la concentration initiale d'herbicide; elle est diminuée par la stérilisation et augmente avec la température même au‐delà de 60°C. Les produits formés lors de la dégradation de 14C metsulfuron méthyle dans un sol, et dans ce sol stérilisé sont partiellement différents. Ces résultats sont en faveur d'une hydrolyse à la fois chimique et microbiologique, même si différents essais pour isoler des micro‐organismes dégradants n'ont pas été fructueux.

Chemical or microbial degradation of sulfonylureas in the soil. II. Metsulfuron methyl

The rate of metsulfuron methyl degradation in a sandy loam soil was studied in relation to herbicide concentration, temperature and different soil treatments, i.e. sterilization and reinoculation by soil. This rate is not dependent on the initial concentration of herbicide; it is reduced by sterilization, and greatly increased by an increase in temperature. In soil and sterilized soil, 14C metsulfuron methyl gives different degradation products. These results demonstrate that chemical hydrolysis and microbial breakdown play a role in soil degradation, although attempts to extract degrading micro‐organisms from the soil were unsuccessful.

Chemischer oder mikrobiologischer Abbau von Sulfonylharnstoffen im Boden. II. Metsulfuronmethyl

Die Abbaurate von Metsulfuron‐methyl war in einem sandigen Lehmboden von der ursprünglichen Konzentration des Herbizids unabhängig, sie nahm mit steigender Temperatur bis über 60°C zu und war in sterilisiertem Boden herabgesetzt. Die Metaboliten von 14C‐metsulfuron‐methyl im belebten und im sterilisierten Boden waren teils unterschiedlich. Demnach unterliegt das Herbizid chemischer Hydrolyse und mikrobiellem Abbau, wenn auch verschiedene Versuche, die abbauenden Mikroorganismen zu isolierten, fehlschlugen.
Dégradation chimique ou microbiologique des sulfonylurées dans le sol. III. Cas du thifensulfuron méthyle
Authors: CAMBON J. P. , BASTIDE J.
Published: July 2006

Résumé: Summary: Zusammenfassung

La dégradation du thifensulfuron méthyle a étéétudiée dans un sol acide et un sol basique. La vitesse et le processus primaire de dégradation sont les mêmes dans les deux sols. Par contre, le produit de dégradation, le thifensulfuron se dégrade plus vite dans le sol acide. La première étape est essentiellement microbiologique, car la dégradation dans les sols stérilisés est beaucoup plus lente. Dans ce cas, les voies de transformation sont différentes dans les deux sols.

Chemical or microbial degradation of sulfonylureas in soil. III. Thifensulfuron‐methyl

The degradation of thifensulfuron‐methyl was studied in a basic and an acidic soil. The rate and major pathway of degradation were similar in the two soils. However, the primary degradation product, thifensulfuron, was broken down more rapidly in the acidic soil. The rate of the first stage of degradation was slower in sterilized soils, indicating that a microbiological process is involved. With this chemical, the products of transformation in the two soils are different.

Chemischer oder mikrobiologischer Abbau von Sulfonyl‐Harnstoffen im Boden. III. Thifensulfuron‐methyl

Der Abbau von Thifensulfuron‐methyl wurde in einem basischen und einem sauren Boden untersucht. Abbaurate und ‐weg waren in beiden Böden ähnlich. Das erste Abbauprodukt, Thifensulfuron, wurde aber im sauren Boden schneller abgebaut. Die Rate des ersten Abbauschritts war in sterilisiertem Boden langsamer, worin sich zeigt, daβ mikrobiologische Prozesse beteiligt sind. Bei diesem Wirkstoff waren die Abbauprodukte in den beiden Böden verschieden.
Dégradation de l'herbicide chlorosulfuron déposé sur divers supports minéraux
Authors: SABADIE J.
Published: July 2006

Résumé: Summary: Zusammenfassung

La dégradation chimique sur supports minéraux secs du chlorsulfuron a étéétudiée à 25°C au contact de quatre solides différents (kaolin, silice, bentonite H+, montmorillonite K10). L'acidité du support favorise l'activité. Deux grandes voies initiales de dégradation ont été observées. A: hydrolyse directe de la fonction urée du substrat; B: déméthylation du substituant méthoxy. Un schéma général d'hydrolyse est proposé.

Dégradation of the herbicide chlorsulfuron on various dry minerals

The chemical degradation of chlorsulfuron on various dry minerals (kaolinite, silica, bentonite H+, montmorillonite K10) was investigated at 25°C. Reactivity was increased with increasing acidity of the support. Two pathways of degradation were initially observed. A: direct hydrolysis of the urea function; B: demethylation of the methoxy substituent. A general degradation pathway is proposed.

Chemischer Abbau des Herbizids Chlorsulfuron auf verschiedenen Mineralien

Der chemische Abbau von Chlorsulfuron auf trockenen Mineralen (Kaolin, Silikat, Bentonit H+, Montmorillonit K10) wurde bei 25°C untersucht. Mit steigender Azidität des Substrats nahm die Reaktion zu. Es wurden 2 erste Abbauschritte beobachtet. A: direkte Hydrolyse der Harnstoffgruppe, B: Demethylierung der Methoxygruppe. Ein allgemeiner Abbauweg wird beschrieben.
Caractérisation phytoécologique des peuplements de mauvaises herbes des champs de canne à sucre et des bananeraies de la Basse Terre (Guadeloupe)
Authors: FOURNET J.
Published: July 2006

Résumé: Zusammenfassung: Summary

Les peuplements de mauvaises herbes de la Basse Terre sont étudiés selon les techniques phytoécologiques (constitution de groupes écologiques d'espèces et de groupements de relevés, ou communautés, reliés aux conditions de milieu). L'échantillonnage est stratifié en fonction de la pluviométrie et de la culture en place. Seuls les résultats concernant les bananeraies et les champs de canne à sucre sont rapportés ici, et comparés. Cinq groupes écologiques bien individualisés portent la plus grande part de 1'information écologique dans cette étude. Les peuplements des bananeraies sont beaucoup plus complexes et diversifiés que ceux des champs de canne, en raison principalement de la diversité de leurs conditions et systèmes de culture, opposée a runiformité relative de ceux de la canne.

Vegetationskundliche Untersuchungen an Unk‐rautgemeinschaften in Zuckerrohr‐ und Ba‐nanenplantagen von Basse Terre (Guadeloupe)

Die Unkrautpopulationen von Basse Terre wur‐den hinsichtlich ökologischer Artengruppen und Verteilung der Pflanzengemeinschaften nach den Umweltbedingungen vegetationskundlich untersucht. Die Aufnahmen wurden nach den Kulturen und der Niederschlagshäufigkeit geordnet. Hier wird nur über die Vegetation in Zuckerrohr und Banane berichtet. Es wurden 5 gut definierte ökologische Gruppen unter‐schieden, die weitgehend die Informationen über die Umweltfaktoren umfaßten. Die Assozia‐tionen der Bananenplantagen sind aufgrund der gröBeren ökologischen Diversität dieser Kultur viel komplexer und vielfältiger als in den relativ einförmigen Zuckerrohrplantagen.

Phytoecological characteristics of weed populations in sugar cane and banana plantations in Basse Terre (Guadeloupe)

Populations of weeds in Basse Terre were studied by phytoecological techniques (species composition of ecological groups and grouping of communities related to environmental conditions). Sampling was stratified on the basis of rainfall and crop. Only the results relating to banana and sugar cane plantations are reported here. Most of the weeds observed belonged to five well‐defined ecological groups. The associations in banana plantations were much more complex and diverse than those in sugar cane, mainly because of the diversity of conditions and growing systems in comparison with the relative uniformity of cane fields.
Physiological investigations into the resistance of a wild mustard (Sinapis arvensis L.) biotype to auxinic herbicides
Authors: PENIUK M. G. , ROMANO M. L. , HALL J. C.
Published: July 2006

Summary: Résumé: Zusammenfassung

Possible mechanism(s) of resistance to auxinic herbicides in wild mustard (Sinapis arvensis L.) were investigated by characterizing responses of susceptible and resistant biotypes to 2,4‐D, di‐camba or picloram. No differences between bio‐types were observed in absorption, translocation, or metabolism of foliar‐applied radiolabelled herbicides. In contrast, the levels of ethylene production varied between biotypes. The susceptible biotype produced twofold and sixfold more ethylene than the resistant biotype within 4 h and 44 h of herbicide application, respectively. These results suggest that the mechanism of resistance in wild mustard is not due to differences in absorption, translocation, or metabolism. Ethylene production studies imply that resistance to auxinic herbicides may be attributed to altered target site(s) of action.

Bases physiologiques de la résistance aux herbicides auxiniques d'un biotype de moutarde des champs (Sinapis arvensis L.)

Les mécanismes possibles de la résistance aux herbicides auxiniques chez la moutarde des champs (Sinapis arvensis L.) ont été recherchés en caractérisant les réponses de biotypes résis‐tants et sensibles au 2,4‐D, au dicamba et au pi‐clorame. Aprés application des herbicides radioactifs sur le feuillage, aucune différence d'absorption, de migration ou de métabolisme n'a été observée. Par contre, la production d'éthylene différait entre les biotypes. Le biotype sensible produisait 2 et 6 fois plus d'éthylène que le biotype sensible, respectivement 4 et 44 heures après l'application d'herbicide. Ces résultats sug‐gèrent que la résistance aux herbicides auxiniques chez la moutarde des champs n'est pas due à des différences d'absorption, de migration ou de métabolisme mais pourrait provenir d'une altération du site d'action.

Physiologische Untersuchung der Resistenz eines Acker‐Senf‐(Sinapis arvensis‐) Biotyps gegenüber Wuchsstoffherbiziden

Der mögliche Mechanismus der Resistenz gegenüber Wuchsstoffherbiziden beim Acker‐Senf (Sinapis arvensis L.) wurde unhand der Reaktion von empfindlichen und resistenten Biotypen gegenüber 2,4‐D, Dicamba oder Picloram untersucht. Hinsichtlich Absorption, Translokation oder Metabolismus der auf die Blätter applizierten, radioaktiv markierten Her‐bizide wurden keine Unterschiede beobachtet. Die Ethylenbildung variierte jedoch zwischen den Biotypen. Der empfindliche produzierte in‐nerhalb 4 oder 44 Stunden nach der Herbizid‐applikation 2‐bzw. 6mal mehr Ethylen als der resistente. Aus den Ergebnissen läßt sich schließen, daß beim Acker‐Senf der Resisten‐zmechanismus nicht in der Absorption, der Translokation oder dem Metabolismus liegt, sondern die Ethylenbildung daran beteiligt ist, wo die Wirkorte fur die Wuchsstoffherbizide liegen.
Response of Xanthium strumarium populations to sublethal applications of bentazone
Authors: ZHANG J. , CAVERS P. B. , JASIENIUK M.
Published: July 2006

Summary: Résumé: Zusammenfassung

Responses of 10 natural or agricultural populations of Xanthium strumarium to sublethal rates of bentazone applied post‐emergence were examined under field conditions. Both vegetative growth and reproduction of sprayed plants were affected by the herbicide. Some populations were more tolerant of bentazone than the others, but the degree of herbicide tolerance did not depend on the previous herbicide experience of a population. Bentazone treatment significantly reduced the weight per fruit in some populations, which in turn could affect the survival and growth of the subsequent seedlings.

La réponse depopulations de Xanthium strumarium à des doses sublétales de bentazone

Nous avons étudié au champ la réponse de dix populations naturelles ou agricoles de Xanthium strumariumà des doses sublétales de bentazone appliquée en post‐levée. L'herbicide affectait la croissance et la reproduction des plantes traitées. Quelques populations étaient plus tolérantes à la bentazone que d'autres, mais le degré de tolérance ne dépendait pas de l'exposition préalable des populations à l'herbicide. La bentazone réduisait significativement le poids des fruits dans quelques populations, ce qui pouvait affecter ensuite la survie et la croissance des jeunes plantes qui en étaient issues.

Wirkung subletaler Dosen von Bentazon auf Xanthium strumarium

Zehn Herkünfte von Xanthium strumarium wurden im Nachauflauf mit subletalen Dosen von Bentazon unter Feldbedingungen behandelt. Sowohl das vegetative Wachstum als auch die Samenbildung der behandelten Pflanzen wurden durch das Herbizid beeinträchtigt. Einige Herkünfte waren weniger empfindlich, doch der Grad der Herbizidempfindlichkeit stand nicht im Einklang mit früheren Erfahrungen über die Wirkung des Herbizids. Durch die Bentazon‐Be‐handlungen nahm das Gewicht der Samen bei einigen Herkünften signifikant ab, so daß ihre Lebensfähigkeit und das Wachstum der Keimpflanzen beeinträchtigt sein könnten.
Implementation of a herbicide simulation model in a geographical information system with an example of a site‐specific application
Authors: LÜCKE A. , GÜNTHER P. , DIEKKRÜGER B. , PESTEMER W. , RICHTER O.
Published: July 2006

Summary: Zusammenfassung

A Geographical Information System (GIS) was combined with a model for simulating leaching and degradation of herbicides. The model uses first–order kinetics to simulate degradation, and a cascade model to simulate transport. This system was tested with data from a 16 km2 research catchment in northern Germany. Geometrical, topological, and soil data of this area were stored in a GIS. For the whole area, divided into small homogeneous sites (ecotopes), model runs were carried out. The system is able to handle data for all ecotopes automatically and to present calculated results on the behaviour of herbicides as distributed over time and depth for the area. An application of ethofumesate made in sugar–beet in spring and recropping of winter wheat after beet harvest was modelled. Degradation/sorption parameters were estimated from similar soils. Simulation results showed slower degradation in the sandy sites of the catchment, compared to the more loamy regions. Residues of herbicide remaining after beet harvest were greater than 20% of the applied dose in the sandy soils after 150 days. Hence, high risk of damage to the following crop of winter wheat was predicted. At the other sites residues remaining were between 2% and 20% of the applied dose.

Einbindung eines Simulationsmodells zum Herbizidverhalten in ein Geographisches Informationssystem–Beispiel zur schlagspezifischen Anwendung

Ein Geographisches Informationssystem (GIS) wurde mit einem Simulationsmodell für Herbizidabbau und –einwaschung kombiniert. Grundlage der Abbausimulation ist eine Kinetik 1. Ordnung, der Transport im Boden wird mit Hilfe eines Kaskadenmodells berechnet. Das System wurde in einem Intensiv–Untersuchungsgebiet (16 km2) in Norddeutschland getestet. Geometrische und topologische Daten der Fläche sowie Bodendaten sind im GIS gespeichert. Für die gesamte Fläche, die in kleine homogene Teilflächen (Ökotope) aufgeteilt wurde, wurden Simulationsberechnungen durchgeführt. Das System ist in der Lage, Daten für alle Ökotope automatisch bereitzustellen und die Ergebnisse zum Einwaschungs– und Abbauverhalten für die gesamte Fläche in ihrer Verteilung über Zeit und Tiefe darzustellen. Als Szenario wurde die Applikation von Ethofumesat in Zuckerrüben im Frühjahr mit einem Nachbau von Winterweizen nach der Rübenemte gewählt. Abbauund Sorptionsparameter waren in ähnlichen Böden ermittelt worden. Die Simulationsergebnisse zeigten einen langsameren Abbau in den sandigen Böden verglichen mit den lehmigen. In den sandigen Böden lagen die Rückstandsgehalte nach 150 Tagen übe 20 % der Ausgangskonzentration, wodurch ein hohes Nachbaurisiko für Winterweizen prognostiziert wurde. Für den Rest der Fläche lagen die Rückstände zwischen 2% und 20% der Ausgangskonzentration.