bluuebunny/crossref_metadata_2025_split huggingface dataset:
Herbicide‐resistant crops: yield penalties and weed thresholds for oilseed rape (Brassica napus L.)
Authors: FORCELLA F. 
Published: July 2006

SummaryAn expérimental procedure was designed to provide a simple model for types of analyses necessary to determine weed density thresholds for advantageous use of crop plants engineered for herbicide resistance. Oilseed rape (Brassica napus L., cv. Tower) biotypes resistant (RES) and susceptible (SUS) to atrazine were used as model crop plants, and wild oat (Avena fatua L.) was used as the model weed. Along a wild oat density gradient equivalent to 0–128 plants m−2, RES plants consistently experienced biomass and yield reductions of approximately 10–20% compared to SUS plants. When atrazine was applied at 1.5 kg ha−1 to control wild oats competing with RES plants, RES biomasses and yields were stabilized at the same level as that where 25–30 wild oats m−2 reduce yields of SUS plants. This implies that with wild oat densities of 25–30 plants m−2, it becomes agronomically advantageous to crop with RES plants plus atrazine rather than to crop with higher‐yielding SUS plants.
Competition between vegetative plants of wild oat (Avena fatua L.) and wheat (Triticum aestivum L.)
Authors: MARTIN M. P. L. D. , FIELD R. J. 
Published: July 2006

SummaryCompetition between wild oat (Avena fatua L.) and wheat (Triticum aestivum L.) was studied in two experiments; a replacement series model and a technique for separation of root and shoot systems. Wild oat and wheat in association resulted in a relative yield total very close to unity showing that the two species were‘crowding for the same space’(or competing for the same resources) and were‘mutually exclusive'. Wild oat was more competitive than wheat, as shown by its aggressivity relative to wheat, relative yields, shoot dry weights and other plant attributes. The greater competitive ability of wild oat was predominantly due to its greater root competitive ability, while the two species had similar shoot competitive ability. Root competition had a much greater effect on the relative performance of the two species than did shoot competition. The effects of root and shoot competition were additive.
Some effects of the herbicide EL‐107 on cellular growth and metabolism
Authors: LEFEBVRE A. , MAIZONNIER D. , GAUDRY J. C. , CLAIR D. , SCALLA R. 
Published: July 2006

SummaryEffects of the herbicide EL‐107 (N‐[3‐(1‐ethyl‐1‐methylpropyl)‐5‐isoxazolyl]‐2,6‐dimethoxy‐benzamide) on the growth of dicotyledonous plants are described. The herbicide did not inhibit germination but reduced the growth of rape (Brassica napus L.) by half at 0.0057 mg l−1. The most characteristic symptom induced was a swelling of the apical regions, and histological observations of root tips of Polygonum persicaria and rape revealed a progressve disappearance of the meristematic zone, which was replaced by enlarged cells almost devoid of cytoplasm. Growth of cells of Acer pseudoplatanus L. and soybean (Glycine max L.) cultured in suspension was also inhibited by EL‐107, which induced a characteristic change in the cell morphology to an enlarged, rounded shape. EL‐107 apparently did not block cell division; at a high concentration it produced some inhibition of protein synthesis, but in Acer cells only. In both types of cell cultures it inhibited, to some extent, the incorporation of glucose into cell wall material.
Comparison of the uptake, movement and metabolism of fluroxypyr in Stellaria media and Viola arvensis
Authors: SANDERS G. E. , PALLETT K. E. 
Published: July 2006

SummaryThe uptake, movement and metabolism of fluroxypyr* is compared in two contrasting weed species, Stellaria media (susceptible) and Viola arvensis (moderately resistant). Similar rates of uptake occurred in both species, with a rapid cuticular uptake of 50% of that applied within 4 h. Total uptake by the underlying leaf tissue reached 66.6% and 70.8% in S. media and V. arvensis after 7 days. In translocation studies, in which 14C‐fluroxypyr was applied to previously sprayed plants, 5.1% of applied 14C‐activity was translocated from the treated leaves of S. media after 1 day, which increased to 42.2% after 7 days, recovered mainly from the stem tissue. In V. arvensis translocation was similar after 24 h however, after 7 days over 40% of applied 14C‐activity remained in the treated leaves and only 9.7% was translocated, mainly to the developing leaves and apical tissue. 14C‐activity extracted from the cuticle was the methylheptyl ester of fluroxypyr in both species. In the treated leaves and apical tissue, 14C‐activity was the free acid of fluroxypyr and polar conjugates with a significantly greater proportion of the acid in S. media. It is concluded that the resistance or V. arvensis is partially due to reduced translocation and greater conjugation than in the susceptible S. media.
Temperature requirements for after‐ripening in buried seeds of four summer annual weeds
Authors: BASKIN J. M. , BASKIN CAROL C. 
Published: July 2006

SummaryFreshly matured, seeds of the four summer annuals Ambrosia artemisiifolia, Polygonum pensylvanicum, Amaranthus hybridus and Chenopodium album were buried in soil at (12/12 h) daily thermoperiods of 15/6, 20/10, 25/15, 30/15 and 35/20°C and at a constant temperature of 5°C. After 0, 1, 3 and 5 months, seeds of each species at each temperature were exhumed and tested at a 14‐h daily photoperiod at all six temperatures. Fresh seeds of A. artemisiifolia and P. pensylvanicum did not germinate at any temperature, those of A, hybridus germinated to 4 and 64% at 30/15 and 35/20°C, respectively, and those of C. album to 11–20% at 25/15, 30/15 and 35/20°C. Seeds of A. artemisiifolia and P. pensylvanicum, which germinate only in spring, required exposure to low (5, 15/6°C) temperature to after‐ripen completely (i.e., to gain the ability to germinate over a wide range of temperatures), and little or no after‐ripening occurred at high (25/15, 30/15 and 35/20°C) temperatures. Seeds of A. hybridus and C. album, which germinate in spring and summer, required exposure to low temperature to after‐ripen completely, but at high temperatures they rapidly gained the ability to germinate at high temperatures. Regardless of the burial temperatures and species, when after‐ripening occurred, seeds firs germinated at high and then at low temperatures. The minimum germination temperature for a species decreased with after‐ripening temperature and with an increase in the length of the burial period.
Studying the population dynamics of weeds
Authors: FERNANDEZ‐QUINTANILLA C. 
Published: July 2006

SummaryStudies of weed population dynamics may be conducted at various levels of complexity. The simplest level involves monitoring a single component of the population throughout several seasons, determining population trends and rates of change. This approach is highly descriptive and, therefore, has a low predictive value. However, it may be useful to evaluate the long‐term effects of various control techniques. In demographic studies, the life‐cycle of the species is divided into various functional stages and the number of individuals present in each stage is monitored throughout the season. From these data, various demographic parameters can be calculated. Population changes through time can be predicted by simulation techniques. This approach offers a practical compromise between the simplicity of long‐term studies and the high analytical and predictive power of more complex analyses. In mechanistic analysis, the population is broken down into a large number of components connected by various physiological und ecological processes. Detailed studies are conducted on each of these individual processes, determining their relationships with environmental factors. The data obtained are integrated into computer models in order to predict the dynamics of the population under various situations. Often the inquirer is confronted by the problem of choice of level of complexity at which it is necessary to study the populations concerned. This choice may depend on the goal of the study, the resources and experience of the people etc. Making the right choice is not always easy, but is essential for the success of any research programme.
Herbicide bioassay
Authors: STREIBIG J. C. 
Published: July 2006

SummaryOne of the most commonly used techniques to assess the efficacy of herbicides is to apply to the principle of bioassays. A bioassay is defined as an experiment for estimating the potency of a herbicide by analysis of the reaction that follows its application to living organisms. The analysis of variance is central to most applications of statistical methods in the analysis of experiments. This is true for bioassay, but perhaps the fundamental importance of regression and related concepts is here particularly apparent. The purpose of this presentation is to quantify herbicidal effects of applying non‐linear regression models to herbicide bioassays, and to demonstrate how some general hypotheses about the mode of action of the assayed herbicides can be incorporated into the regression models. The validity of herbicide bioassay data is discussed in view of the general principles used in bioassay in other biological sciences.
Broomrape (Orobanche spp.) control with ethylene dibromide and chloropicrin
Authors: JACOBSOHN R. , KELMAN Y. , SHARED RACHEL , KLEIN L. 
Published: July 2006

Summary: Résumé: ZusammenfassungEthylene dibromide effectively controlled Orobanche crenata Forsk. and O. cernua Loefl. but was not effective against O. aegyptiaca Pers. and O. mutelii F. Schultz. Chloropicrin was considerably less effective than ethylene dibromide. Mixtures of both compounds did not result in improved broomrape control but nonetheless had a positive effect on crop yield. Destruction des Orobanches avec du dibromure d'ethylène et de la chloropicrineLe dibromure d'éthylène a été efficace contre Orobanche crenata Forsk et O. Cernua Loefl, mais non efficace contre O. aegyptiaca Pers, et O. mutelii F. Schultz. La chloropicrine est beaucoup moins efficace que le dibromure d'ethylène. Les mélanges des deux matières actives n'ont pas amélioré l'efficacité sur orobanches mais néanmoins ont eu un effet positif sur le rendement de la culture.Bekämpfung von Orobanche‐Arten mit Ethylendi‐bromid und ChlorpikrinMit Ethylendibromid konnten Orobanche crenata Forsk. und O. cernua Loefl., aber nicht O. aegyptica Pers. und O. mutelii F. Schultz bekämpft werden. Chlorpikrin war beträchtlich weniger wirksam. Mischungen der beiden Wirkstoffe ergaben keine bessere Wirkung, beeinflussten aber den Ertrag der Kulturpflanzen positiv.
Transplant survival of Rumex obtusifolius L. and Rumex crispus L. in three old reseeded grasslands
Authors: HONGO A. 
Published: July 2006

SummaryA transplant experiment was performed to compare the survivorship of Rumex obtusifolius L. and Rumex crispus L., and also to determine the environmental characteristics of grasslands seriously colonized with R. obtusifolius. One‐month‐old seedlings of each Rumex species were transplanted into three old reseeded swards with different infestation levels of R. obtusifolius plants. Rumex crispus was absent from all swards. Their survival was monitored at monthly intervals for 4 years (May 1982 to May 1986). The mortality of R. obtusifolius was greater in the third and fourth years in all swards, less than 2% of the phytometers being alive in the fifth spring. The number of R. crispus transplants declined more gradually in the course of the experiment and 4–24% of the phytometers still survived by the end of the experiment. This suggests that R. obtusifolius plants colonized in sown grasslands in the cool‐climate region have a comparatively short life expectation of 3–4 years. Mortality rate, growth in size and flowering percentage tended to vary significantly between sites: higher in more productive swards. In years 2 and 3 there were seven‐fold differences in mean dry matter weights of plants that produced an inflorescence and those that remained in a vegetative phase. The mortality of transplants was not size dependent in either Rumex species. Phytometers died at random irrespective of the individual sizes.
Dicotyledonous weeds of spring cereal crops in north‐east Scotland
Authors: SIMPSON M. J. A. , CARNEGIE HAZEL M. 
Published: July 2006

SummaryA survey of dicotyledonous weeds of spring cereals was conducted prior to herbicide application in 1985 in six districts of north‐east Scotland, which involved a total of 113 fields. Results were similar to those from an earlier survey in 1973. The main species remained the same but in four of the six districts, total weed densities were lower. Stellaria media was the most common species except in Upper Banffshire and Morayshire where Galeopsis spp. and Polygonum aviculare, respectively, were predominant. The main changes apparent were a decline of Spergula arvensis and Polygonum persicaria, and an increase in Matricaria perforata and Viola arvensis in several districts.
Quantitative bioassays for determining residues and availability to plants of sulphonylurea herbicides
Authors: GÜNTHER P. , RAHMAN A. , PESTEMER W. 
Published: July 2006

SummaryA bioassay procedure for quantitative determination of sulphonylurea herbicides is described. Turnips (Brassica rapa) were found very suitable as test plants and gave results within 10 days. Six sulphonylurea compounds were investigated for their activity in three widely differing soils. The potential availability to plants was calculated from the dose‐response curves of vermiculite (non‐sorptive substrate) and the corresponding ED50‐values of the soils. The dose‐response relationship (logistic curve) was described by a computer model by a position parameter, the slope of the curve and the minimum and maximum fresh weights of plants. The limit of quantitative detection in the range of ED30 in vermiculite was 0·06 μg 1−1 for sulfometuron and 1·03 μg 1−1 for DPX‐L5300, methy12‐([4‐methoxy‐6‐methyl‐1,3,5‐triazin‐2‐yl (methyl)carbamoyl]‐sulphamoyl) benzoate. Results with turnips showed that sulfometuron was the most active compound in all substrates (ED50 in vermiculite 0·12 μg 1−1) followed by chlorsulfuron, metsulfuron‐methyl, triasulfuron, DPX‐M6316, methyl 3‐([(4‐methoxy‐6‐methyl‐1,3,5‐triazin‐2‐yl)aminocarbamoyl]‐aminosulphaphamoyl)‐2‐thiophenecarboxylate, and DPX‐L5300 which had ED50 or 1·98 μg 1−1, The Horotiu sandy loam soil showed the highest ED50‐values and the lowest plant availability for all compounds compared to the other soils. Probit and logistic evaluation methods for deriving dose‐response relationships are compared and their applicability is discussed.
Weed flora in the Middle Valley of the Guadalquivir, Spain
Authors: SAAVEDRA M. , GARCIA‐TORRES L. , HERNANDEZ‐BERMEJO E. , HIDALGO B. 
Published: July 2006

SummaryA floristic study of the weeds in irrigated crops in the Guadalquivir River Valley (southern Spain) revealed a total of 284 species in the 267 fields surveyed, of which about 100 can be considered highly harmful. The families with the highest numbers of species were Compositae, Gramineae, Leguminosae, Cruciferae and Umbelliferae. Although 77·8% of the species were therophytes, geophytes were important in spring‐sown crops. Most species were of Mediterranean origin, especially in autumn‐sown crops; Cosmopolitan and Neotropical species were more important in the spring‐sown crops. At the early and late crop growth stages 7% and 10%, respectively, of the fields had severe or very severe infestations.The relationships between the main weed species and crops were studied by cluster analysis, using the corrected frequency of each species in each crop as the reference parameter. This allowed classification of the species into subgroups and hierarchical groups according to their agro‐ecological preferences. A close relationship was found between a given crop, its cycle and the usual soil management practices and the phenology of certain species, reflecting the influence of these factors in restricting the germination period. The analysis differentiated the typically winter, summer and intermediate weed floras.
The effect of nitrogen fertilizers on the germination and seedling emergence of wild oat (A. fatua L.) seed in different soil types
Authors: AGENBAG G. A. , de VILLIERS O. T. 
Published: July 2006

SummaryAmmonium‐containing fertilizers such as granular limestone ammonium nitrate (LAN) and liquid ammonium nitrate (AN) proved to be most effective in stimulating germination and emergence of wild oat in sandy and loamy soil. In pot experiments, rates as low as 25 kg N ha−1, significantly increased seedling emergence of wild oat. In sandy soil percentage emergence increased with increasing levels of LAN‐fertilizer up to 125 kg N ha−1 which gave 76·1 % emergence after 60 days. In control pots where no nitrogen was applied, only 21·6% of seeds planted emerged after 60 days, In loamy soil, as for AN in both soil types, high levels of LAN initially delayed seedling emergence. This negative effect disappeared approximately 15 days after seeding, resulting in no significant difference in emergence of wild oat where 25 to 125 kg N ha−1 was applied as LAN or AN. All these rates, however, increased seedling emergence between 25 and 35% compared to the no‐nitrogen treatments. Since the same rate of ammonia gas is not equally effective in breaking dormancy of semi‐ and deeply dormant wild oat seed, results of these experiments are not necessarily applicable to wild oat seeds differing in dormancy status.
Diclofop‐methyl antagonism by broadleaf weed herbicides: the importance of leaf expansion rate
Authors: ANDREWS M. 
Published: July 2006

Summary: Avena saliva cv. Amuri and A. fatua were sprayed with diclofop methyl (1.0 kg a.i. ha−1) alone and in combination with 2,4‐D (1.1 kg a.i. ha−1), bentazone (1.0 kg a.i. ha−1), chlorsulfuron (15 g a.i. ha−1) or dicamba (0.3 kg a.i. ha−1). Effects of the herbicides on leaf extension rate during the first 8 to 10 days after spraying and subsequent growth (dry weight) after 57–75 days were determined by comparison with unsprayed plants. Diclofop‐methyl applied alone did not cause a decrease in leaf extension rate of A. saliva or A. fatua until at least 4 days after spraying. All broadleaf weed herbicides in combination with diclofop‐methyl caused a decrease in leaf extension rate of both species within 2 days of spraying. Ten days after spraying, leaf extension rates for plants sprayed with a broadleaf weed herbicide plus diclofopmethyl (all combinations) were lower than for unsprayed plants but greater than for plants sprayed with diclofop‐methyl alone. With the exception of A. fatua sprayed with bentazone, long‐term growth of plants sprayed with a broadleaf weed herbicide plus diclofop‐methyl (all combinations) was lower than for unsprayed plants but greater than for plants sprayed with diclofop‐methyl alone. Bentazone applied with diclofop‐methyl caused a substantial decrease in leaf extension rate of A. fatua within 24 h of spraying but at harvest, dry weight of plants from this treatment was similar to or less than that for plants sprayed with diclofop‐methyl alone. Application of diclofop‐methyl with bentazone at a rate of 0.3 kg a.i. ha−1 also caused a reduction in leaf extension rate of A. fatua within one day of spraying. At this rate of bentazone, dry weight of plants at harvest was intermediate to that of unsprayed plants and those sprayed with diclofop‐methyl alone. It is proposed that decreased leaf expansion rate during the first few days afte spraying is the cause of broadleaf weed herbicide antagonism of diclofop‐methyl.
Saure Hydrolyse von Metsulfuron‐methyl
Authors: SABADIE J. 
Published: July 2006

Résumé:Deux voies de dégradation sont observées au cours de l'hydrolyse du métsulfuron méthyle en solution aqueuse acide: hydrolyse de la fonction urée et hydrolyse du substituant méthoxy. L'abaissement du pH (6 à 1) accélère fortement le processus sans en modifier la sélectivité. L'augmentation de la température (25 à 55°C) favorise la vitese (EA= 84 kj mol−1) et l'hydrolyse de la fonction urée, Les effets d'autres facteurs (cations de métaux de transition, acides humiques, argiles) généralement limités ne concement que la vitesse de la transformation.
Weed size hierarchies in Denmark
Authors: JENSEN P. K. 
Published: July 2006

Summary:In 962 field trials in different crops, the size of a number of weed species was investigated. The weeds were ranked according to their size on a single occasion. The ranks of the species were examined relative to two weed species, Viola arvensis and Matricaria inodora. The ranking was, however, independent of which of the two species were used as standard. The correlation between the rankings with Viola arvensis as standard, and the rankings with Matricaria inodora as standard were r= 0‐93 for spring sown crops, and r= 0.84 for autumn sown crops. Sinapis arvensis was the largest weed species in spring sown crops, with a weight of 14.5 times that of Viola arvensis, followed by Brassica napus, Galeopsis spp., Thlaspi arvense and Amsinckia spp. Viola arvensis. Veronica spp. and Lamium spp. were the smallest weed species in spring sown crops. Galium aparine was the largest species in autumn sown crops, whereas spring germinating species such as Polygonum spp. were among the smallest. The ranks of Viola arvensis, Myosotis arvensis, Lapsana communis, Matricaria inodora and Lamium spp. were almost identical in spring sown crops and in autumn sown crops.
Räumliche Verteilung der Samenbank–ein Vergleich statistischer Methoden
Authors: DESSAINT F. 
Published: July 2006

Résumé:La répartition spatiale du potentiel semencier a été analysée à partir de données simulées et de données réelles provenant d'une parcelle expérimental. Trois types d'approches statistiques ont été comparés quant à leur capacitéà déterminer la structure spatiale de populations: (1) l'ajustement de la distribution des fréquences observées à une distribution théorique (Poisson et Binomiale négative); (2) le calcul d'indices basé sur la moyenne (m) et la variance (V) d'échantillonnage (rapport V/m, la ‘mean crowding’ et l'indice d'agrégation de Lloyd); (3) le calcul d'un coefficient d'autocorrélation (le I de Moran) permettant de prendre en compte la position géographique des prélèvements. Au vue des résultats obtenus à partir des données simulées, il apparait que seul le coefficient d'autocorrélation est adaptéà la description des structures spatiales. Appliqué aux données réelles, il a permis de définir la répartition spatiale des principales espèces.