bluuebunny/crossref_metadata_2025 huggingface dataset:
Germination, emergence and seedling growth of Hypericum perforatum L.
Authors: CAMPBELL M. H.
Published: July 2006

Germination of new seeds (1–6 months old) of Hypericum perforation L. was restricted by high temperatures (16h/8h, 20/30°C), darkness and a chemical inhibitor in exudate from the capsule, whereas germination of old seeds (9 years) was only restricted by the inhibitor. The effect of the chemical inhibitor and high temperatures was overcome, respectively, by washing seeds in water and by reducing temperatures to constant 15°C. Calcium in solution from CaCO3 and from three different soils did not prevent the germination of new or old seeds or of seeds collected from five different locations. There were differences in the germination characteristics and dormancy mechanisms of seeds collected from different localities, Restriction of the emergence of seedlings by a covering of > 2 mm of soil appeared to be due to lack of seedling vigour rather than to lack of light. Seedling growth was much slower than in other pasture species. Thus the requirements for germination of H. perforatum of low temperature and moisture to wash away the chemical inhibitor favour its establishment but the slow growth of its seedling restricts its emergence and renders it extremely susceptible to competition from other plants.
Effect of mixed function oxidase inhibitors on the toxicity of chlortoluron and isoproturon to wheat
Authors: GAILLARDON P. , CABANNE F. , SCALLA R. , DURST F.
Published: July 2006

Growth responses of wheat plants to combined treatments of four mixed function oxidase (MFO) inhibitors and chlortoluron were determined. Analysis of interactions showed that piperonyl‐butoxide and especially ABT (1‐aminobenzotriazole) increased the toxicity of chlortoluron. Metyrapone and 2,4‐dichlorophenoxypropyne were phytotoxic and did not exert any clear interaction. ABT also increased the toxicity of isoproturon to wheat.

Our results suggest that ABT Strongly inhibits the breakdown of chlortoluron and isoproturon in wheat. Since ABT is known to act as a suicide substrate for plant cytochrome P‐450, wheat enzymes involved in the metabolism of these two herbicides are likely to belong to this class. It thus appears that compounds designed to inhibit plant cytochrome P‐450 enzymes may interact with herbicide metabolism and are potential synergists of herbicide activity.
Control of Sorghum halepense (L.) Pers. in cotton with post‐emergence herbicides and trifluralin
Authors: KURTZ M. E.
Published: July 2006

Summary: Résumé: Zusammenfassung

A field experiment was conducted in 1981 and 1982 to evaluate five post‐emergence herbicides applied alone or following a preplant incorporated application of trifluralin for the control of Sorghum halepense (L.) Pers. in cotton (Gossypium hirsutum). One application of the methyl ester of haloxyfop [methyl 2‐ (4‐ ((3‐chloro‐5‐trifluoromethyl)‐2‐pyridinyl)oxy)phenoxy)pro‐panoate], trifluralin plus the ethyl ester of DPX‐Y6202 [ethyl[2‐[‐4‐(6‐chloro‐2‐quinoxalinyl)oxy]phenoxy]propionate], the butyl ester of fluazifop and trifluralin plus haloxyfop resulted in over 90% control of S. halepense just prior to harvest in 1981 and 1982. Sorghum halepense control was similar whether the post‐emergence herbicides were applied alone or following preplant incorporated trifluralin at 0.8 kg ha−1.

La lutte contre Sorghum halepense (L.) Pers. en culture de cotonnier moyennant des herbicides de post‐levée et la trifluraline

Une expérience a été installée en plein champ en 1981 et 1982 dans le but d'évaluer cinq herbicides de post‐levée, appliqués seuls ou suite à la trifluraline incorporée avant le semis, dans la lutte contre Sorghum halepense (L.) Pers. en culture de cotonnier (Gossypium hirsutum). Une seule application de l'haloxyfop ester de méthyle [méthyle 2‐(4‐((3‐chloro‐5‐ (trifluorométhyle)‐2‐pyridinyle) oxy)phénoxy)propanoate], de trifluraline + DPX‐Y6202 ester d'éthyle (éthyle[2‐[4‐(6‐chloro‐2‐quinoxalinyle)oxy]phénoxy)propionate), de l'ester butylique du fluazifop et de trifluraline + haloxyfop a permis en 1981 et 1982 une bonne maîtrise (90%) de S. halepense juste avant la récolte. La maîtrise de Sorghum halepenseétait semblable, que les herbicides de postlevée aient été précédés ou non d'une application de trifluraline à 0,8 kg ha−1 incorporée avant le semis.

Bekämpfung von Sorghum halepense (L.) Pers. in Baumwolle mit Nachauflaufherbiziden und Trifluralin

In den Jahren 1981 und 1982 wurden Feldversuche zur Bekämpfung von Sorghum halepense (L.) Pers. in Baumwolle (Gossypium hirsutum) mit fünf Nachauflaufherbiziden durchgeführt. Die Herbizide wurden allein oder nach einer vor der Baumwollsaat erfolgten Einarbeitung von Trifluralin appliziert. Eine Applikation des Methylesters von Haloxyfop [Methyl‐2‐(4‐((3‐chloro‐5‐(trifluormethyl)‐2‐pyridinyl)oxy)phenoxy)propanoat]. Von Trifluralin + Aethylester von DPX‐Y 6202 [Aethyl[2‐[‐4‐(6‐chlor‐2‐quinoxalinyl)oxy)phenoxy)propionat], des Butylesters von Fluazifop und Trifluralin + Haloxyfop ergaben in beiden Jahren kurz vor der Ernte eine über 90 ige Kontrolle von S. halepense. Der Bekämpfungserfolg war ähnlich, gleichgültig ob die Herbizide allein oder nach der Einarbeitung von Trifluralin (0,8 kg ha−1) appliziert worden waren.
Diversité floristique et biologie des adventices de la région du Tadla (Maroc)
Authors: TANJI A. , BOULET C.
Published: July 2006

Résumé: Summary: Zusammenfassung

Dans le but d'inventorier les adventices des cultures de la région du Tadla (Maroc Central), 345 champs cultivés ont fait l'objet de relevés phytoécologiques. Trois cent trente espèces adventices appartenant à 50 familles botaniques ont ainsi pu être identifiées: 84% sont des dicotylédones (essentiellement Compositae, Leguminosae, Cruciferae, Caryophyllaceae, et Umbelliferae) et 73% sont des annuelles. Une brève étude agronomique a permis de distinguer 70 espèces ayant une nuisibilité non négligeable vis à vis des différentes cultures de la région. Inventory and biology of cropland weeds of the Tadla region (Morocco) An inventory of cropland weeds of the Tadla region (Central Morocco) was made, based on samples from 345 cultivated fields. Three hundred and thirty species were identified, belonging to 50 botanical families: 84% of the species were dicots (mainly Compositae, Leguminosae, Cruciferae, Caryophyllaceae, and Umbelliferae), and 73% were annuals. Seventy species are important cropland pests. Ueber die Floristik und Biologie der Unkräuter in der Region von Tadla (Marokko) Ziel dieser Studie war eine Inventaraufnahme der Ackerunkräuter in der Region Tadla (Zentral‐marokko); zu diesem Zweck wurden in 345 Feldkulturen phytoökologische Bestandesaufnahmen durchgeführt. Dabei wurden 330 Unkrautarten aus 50 Familien identifiziert; davon waren 84% Dikotyledonen (hauptsächlich Compositen, Leguminosen, Cruciferen, Caryophyllaceen und Umbelliferen) und 73% Anuelle. 70 Arten verursachten in verschiedenen Kulturen starke Schädigungen.
Abscisic acid as a protectant of Avena fatua L. against diclofop‐methyl activity
Authors: FIELD R. J. , CASELEY† J. C.
Published: July 2006

The imposition of water stress before or al the time of spraying diclofop‐methyl reduced efficacy against wild oat (Avena fatua L.). Similar reductions in herbicide performance were obtained by application of 20 μg of the methyl ester of abscisic acid (ABA) to plants with three to four leaves before spraying with I kg ha−1 diclofop‐methyl. Application of 40–100 μg ABA per plant effectively protected plants against damage from diclofop‐methyl applied at 1 5–2 0 kg ha −1. The application of 20 μg ABA induced rapid stomatal closure and a reduction in leaf extension rate, which were sustained for 7–8 days after treatment. These changes were associated with an overall reduction in shoot growth. ABA‐treated plants that were additionally sprayed with diclofop‐methyl sustained ABA symptoms, but no additional weight loss or leaf chlorosis. The mechanism of the protective action of ABA on diclofop‐methyl has not been determined.
Effects of drying and dl‐strigol on seed conditioning and germination of Striga asiatica (L.) Kuntze
Authors: HSIAO A. I. , WORSHAM A. D. , MORELAND D. E.
Published: July 2006

Seeds of Striga asiatica (L.) Kuntze required 7 and 14 days at 30°C to become conditioned when they were immersed in water and 10−8mdl‐strigol, respectively. At least 80% of seeds so conditioned germinated with 10−8mdl‐strigol as a terminal stimulation treatment. Seeds that were first immersed in water for 2 days, then subjected to one to three drying periods of 2 days each, either separately or continuously, required only 2 days of water immersion to become conditioned. Seeds first immersed in 10−8mdl‐strigol, then subjected to one or two drying periods, required only 3–4 days of water immersion as compared to a 14 days’requirement without drying treatments. The seeds first immersed in water or 10−8mdl‐strigol and then dried, plus one or two 10−8mdl‐strigol immersions, required 4 days of water immersion to become conditioned. However, the seeds immersed in various combinations of water or 10−8mdl‐strigol solutions plus one, two or three drying periods of 2 days each required 6 days of water immersion to become conditioned. The results indicate that the interaction of prolonged drying treatments and dl‐strigol immersions delay conditioning processes in the seeds. Both water immersion and short drying treatments, however, seem to enhance certain required processes that occur during conditioning, thereby reducing the time required for the seeds to become conditioned when re‐immersed in water.
Influence of environmental factors on the performance of sethoxydim against Elymus repens (L.)
Authors: COUPLAND D.
Published: July 2006

The performance of sethoxydim on Elymus repens (L.) Gould was studied under contrasting levels of humidity, light intensity, temperature, soil moisture and simulated rainfall using controlled environment chambers. Over a 24‐h post‐spraying period, increases in humidity and temperature markedly enhanced herbicide performance, while effects of light intensity were less pronounced. Soil moisture deficit significantly reduced herbicide performance, but there were no adverse effects of wet soil conditions (twice field capacity) on activity. The effects of simulated rain depended upon herbicide dosage, time interval between spraying and the onset of rain, and rain intensity. A low rain intensity of 0.5 mm h−1 did not reduce herbicide performance even when applied 10 min after spraying. The longer term studies, over 4 weeks, showed increases in herbicide activity with higher temperatures but lower light intensities.
Joint action of root‐absorbed mixtures of auxin herbicides in Sinapis alba L. and barley (Hordeum vulgare L.)
Authors: STREIBIG J. C.
Published: July 2006

The efficacy of some binary mixtures of MCPA, 2,4‐D dichlorprop, mecoprop and dicamba was evaluated in water culture experiments. Within each of seven assays, two dose‐response curves described the phytotoxicity of the herbicides administered separately and three curves described the phytotoxicity of mixtures in fixed ratios. A non‐linear regression model of dry matter on the logarithm of the dose, assuming the five response curves to be mutually parallel, was fitted and a reference model, the Additive Dose Model (ADM) to assess the efficacy of the mixtures, was also incorporated into the regression. The biological interpretation of ADM is often associated with mixtures of compounds having similar mode of action. Mixtures of dicamba with dichlorprop or 2,4‐D were more potent than expected under ADM in two Sinapis alba assays. In one assay with mixtures of MCPA and dichlorprop the parallel‐line model fitted somewhat better than did the ADM regression. This also applied to a barley assay with mixtures of dicamba and MCPA. On the basis of the results obtained it is suggested that the analogy between the implicit assumptions of the parallel‐line assay can be extended to the ADM. Parallel dose response curves are a necessary but not a sufficient condition for assuming similar mode of action Similarly, it can be argued that mixtures of compounds following ADM are a necessary but not a sufficient condition for assuming a similar mode of action for the herbicides in a mixture.
Persistence of GR7 and Striga germination stimulant(s) from Euphorbia aegyptiaca Boiss. in soils and in solutions
Authors: BABIKER A. G. T. , IBRAHIM NADIA E. , EDWARDS W. G.
Published: July 2006

The activity of GR7 and Striga germination stimulant(s) from Euphorbia aegyptiaca Boiss. showed adequate persistence (6–8 days) in acidic soils (pH 5·0–6·3), but residual activity was short (1–3 days) in alkaline soils. The compounds tended to lose activity at a faster rate in the alkaline clay Gezira soil (pH 7·8), than in its sandy equivalent (pH 8·1). In solution, pH had no influence on initial activity, but residual action was reduced more rapidly by alkalinity and high temperature. However, the rate of loss of activity in solution was slower than in soils.
Effects of some commercial herbicides on rhizobia and their symbiosis with peanuts
Authors: KISHINEVSKY B. , LOBEL RINA , LIFSHITZ N. , GURFEL DEBORA
Published: July 2006

Four herbicides commonly used in Israel for controlling weeds in peanuts were evaluated under field and screenhouse conditions. Terbutryn (Terbutrex 50, w.p.), ethalfluralin (Sonalan 333, e.c.), dinitramine (Cobex 240, e.c.) and alachlor (Alapaz 480, e.c.), used at recommended levels, had no adverse effect on nodulation rate, nitrogenase activity, total nitrogen of peanut tops or pod yield, compared with control (inoculated but herbicide non‐treated) plants. Studies were conducted to determine the relative toxicity in vitro of the herbicides on each of four Rhizobium strains used for commercial peat inoculant production. The results showed that at up to 94 μg g−1 the herbicides has no inhibitory effect on the growth of rhizobia. The sensitivity of Rhizobium strains to different rates of the chemicals decreased in the order: dinitramine>alachlor>ethalfluralin>terbutryn. It was found that various strains differ in their sensitivity to the herbicides tested.
Survival and growth of seedlings of Rumex obtusifolius L. and Rumex crispus L. in newly sown grassland
Authors: HONGO A.
Published: July 2006

The survival and growth of seedlings of Rumex obtusifolius L. and Rumex crispus L. were investigated from 1982 to 1984. A sward was established by the sowing of seeds of Dactylis glomerata and Trifolium repens and managed under two cutting frequencies. Five hundred seeds of each Rumex species were sown m−2. The total number of emergent seedlings of each Rumex species over two seasons was 230–360 m−2. About 85% of them emerged within 3 months of sowing. Both Rumex species showed the same pattern of survivorship. Survival was clearly enhanced by frequent cutting during the second season. About 20% of the emerged plants survived through to the third season. Plants that emerged during the first season only flowered during the second season. The flowering percentage of total surviving plants was significantly higher in R. obtusifolius than in R. crispus. Rumex obtusifolius was higher in dry matter of aerial parts defoliated during the second season and more individual plants survived through to the third season than for R. crispus. Moreover, dry matter production of grass and clover was depressed by 25–30% in mixtures with R. obtusifolius. compared with production in mixtures with R. crispus.
An equation to describe dose responses where there is stimulation of growth at low doses
Authors: BRAIN P. , COUSENS R.
Published: July 2006

An equation is presented lo describe the relationship of a plant response to herbicide dose where there is stimulation of response al low doses. Us properties are discussed and examples of its use are given. The equation includes the most commonly used sigmoidal curve as a special case.
On robust weed population models
Authors: MORTIMER A. M. , SUTTON J. J. , GOULD P.
Published: July 2006

Difference equation models incorporating density dependence are considered in the context of the description of the dynamics of weed populations over discrete generations. Their applicability is assessed in relation to modelling yield loss, two species and three species interactions and the influence of density independent control practices. Analysis indicates that whilst plant populations may show simple dynamical properties around equilibrium levels, convergent oscillations to equilibrium may result from the application of control measures. Such models are argued to have potential as robust qualitative predictors of weed species abundance.
Adsorption and degradation of chlorsulfuron and metsulfuron‐methyl in soils from different depths
Authors: WALKER A. , COTTERILL E. G. , WELCH SARAH J.
Published: July 2006

Adsorption and degradation rates of chlorsulfuron and metsulfuron‐methyl were measured in soil taken from depths of 0–20, 20–40 and 40–60 cm at eight sites. Adsorption of both herbicides was negatively correlated with soil pH, and positively correlated with soil organic matter content. When two soils with very high organic matter were excluded from the calculations, the correlations with organic matter content were no longer statistically significant but those with soil pH were affected only slightly. Degradation rates of both herbicides generally decreased with increasing depth in the soil and were positively correlated with microbial biomass and negatively correlated with soil pH. The possible significance of the results to persistence of the herbicides in the field is discussed.
Effects of the safeners CGA 154281, oxabetrinil and fenclorim on uptake and degradation of metolachlor in corn (Zea mays L.) seedlings
Authors: KREUZ K. , GAUDIN J. , EBERT E.
Published: July 2006

Summary. The influence of three crop safeners on the uptake and degradation of 14C‐metolachlor was investigated in two corn varieties. Following application of herbicide and safener together to seedling shoots the concentrations of non‐metabolized 14C‐metolachlor in the tissues was found to be lower in the tolerant variety LG 9 than in the susceptible variety 211A. The difference between varieties was due to differences in both uptake and degradation of 14C‐metolachlor.

Following shoot application most of the radioactivity was retained in the coleoptile and the mesocotyl. Two hours after application 95% of the herbicide had been degraded in coleoptiles and mesocotyls, whereas approximately 20% of non‐metabolized 14C‐metolachlor was present in the enclosed developing shoot leaves. In both corn varieties the safener CGA 154281 caused a substantial lowering of tissue levels of parent 14C‐metolachlor. This was primarily due to an enhanced degradation. Glutalhione‐S‐transfer‐ase (GST) enzyme activity in shoot tissues was found to be enhanced in both varieties by CGA 154281. Oxabetrinil and fenclorim were less effective than CGA 154281 both in reducing tissue levels of non‐metabolized 14C‐metolachlor and in enhancing GST activity in either variety.
Interactive effects of diluent pH and calcium content on glyphosate activity on Panicum repens L. (torpedograss)
Authors: SHILLING D. G. , HALLER W. T.
Published: July 2006

Summary. Solutions of glyphosate containing 0–5 mM calcium, both with buffering (pH 4, 6 or 8) and without, were sprayed onto Panicum repens L. (torpedograss) foliage. Growth inhibition of the treated foliage was poorly correlated with inhibition of shoot regrowth from rhizomes. Therefore, when evaluating long term control of perennial grasses regrowth data should be utilized. Spray solution pH, calcium and glyphosate rate influenced herbicidal activity on torpedograss. Calcium affected glyphosate activity on torpedograss except at the highest herbicide rate (4·48 kg ha−1). Optimum herbicidal activity on torpedograss was achieved with soft water (i.e. no calcium), however, when calcium was present in the spray solution a pH of 6 reduced its antagonistic effects.
Abbau von Metsulfuron–methyl an verschiedenen Mineralien
Authors: SABADIE J. , BASTIDE J.
Published: July 2006

La dégradation chimique en phase séche du metsulfuron méthyle a étéétudiée à température ambiante au contact de trois solides minéraux (Kaolin, silice, Montmorillonite K10). L'acidité du support favorise l'activité. Deux grandes voies de dégradation ont été observées: hydrolyse directe de la fonction urée du metsulfuron méthyle; déméthylation du substituant méthoxy puis hydrolyse. La formation d'isocyanate intermédiaire est postulée dans tous les cas. La fonction carboxyméthyl demeure généralement inchangée.
Potentiel semencier et propriétés de sol des terres arables en Baviére
Authors: ALBRECHT H. , BACHTHALER G.
Published: July 2006

In der vorliegenden Arbeit wurden 140 Ackerfláchen aus 7 Regionen Bayerns auf ihr Samenpotential und ihre Bodeneigenschaften untersucht. Dabei zeigte sich, daß die Samendichte eng mit Faktoren der Bodenökologie korreliert ist. So fanden sich in basischen Substraten zumeist niedrige, in schluffigen und sandigen Böden mit mäßig saurer Reaktion mittlere und in stark sauren Sanden hohe Samengehalte. Sehr hohe Samenkonzentrationen wurden außerdem in saisonal vemäßten Äckern festgestellt. Diese Ergebnisse lassen sich dadurch erklären, daß sich unter bestimmten Bodenverhältnissen charakteristische Artenkombinationen entwickeln. Über eine artspezifische Samenproduktion entsteht somit auch ein für den Standort typisches Samenpotential.
Uptake, translocation and phytotoxicity of imazapyr and glyphosate in Imperata cylindrica (L.) Raeuschel: effect of herbicide concentration, position of deposit and two methods of direct contact application
Authors: TOWNSON JANE K. , BUTLER RUTH
Published: July 2006

The activity of imazapyr and glyphosate against Imperata cylindrica was studied in field and glasshouse experiments using two methods of direct contact application; a rope‐wick wiper and a cloth soaked in herbicide solution. The effect of concentration and position of application on herbicide uptake and translocation was also measured. At the lowest dose of imazapyr (5 mg acid equivalent (a.e.) per plant), phytotoxicity was greater from applications by a rope‐wick wiper than by a cloth. However, when the dose of imazapyr was increased, the cloth applicator was more effective than the rope‐wick wiper. At all doses of glyphosate, rope‐wick application was more effective than wiping with a cloth. Herbicide performance in the glasshouse was similar to that in the field. Radiotracer studies showed that increasing the concentration of imazapyr, while keeping herbicide dose constant, decreased uptake and translocation of radiolabel. In contrast, the rate of uptake of 14C‐glyphosate increased with increasing herbicide concentration. Position of application did not significantly affect the amount of uptake and translocation of radiolabel to the rhizomes. It is concluded that rope‐wick wipers are more effective than wiping with a cloth for applying imazapyr and glyphosate to I. cylindrica, provided that the concentration of imazapyr does not exceed 10 g a.e. l−1.
Phenological development and biomass allocation inSilene vulgaris(Moench) Garcke
Authors: WALL D. A. , MORRISON I. N.
Published: July 2006

Silene vulgaris (Moench) Garcke, grown from seed or from crown buds, exhibited three dis tinct growth phases; establishment, reproduc tive and post‐reproductive. The establishment phase was characterized by rapid accumulation of shoot biomass, high relative growth rates (RGRs) and leaf area ratios (LARs). The sexual reproductive phase was characterized by a rapid increase in floral and seed biomass, minimal root development, and declining RGRs and LARs. In the post‐reproductive phase, root and crown biomass increased rapidly concomitant with the development of regenerative buds; low RGR and LAR values occurred during this phase. Although similar growth phases were identified in both the first (grown from seed) and second years (grown from crown buds) of growth, LARs and RGRs were lower in the second than in the first year. In the second year of growth, plants exhibited a continual increase in below‐ground biomass throughout growth, including the flowering period, a feature which was absent in the first year of growth.
Characterization of the germination and emergence response to temperature and soil moisture of Avena fatua and A. sterilis
Authors: FERNANDEZ‐QUINANTILLA C. , ANDUJAR J. L. GONZALEZ , APPLEBY A. P.
Published: July 2006

Seeds of Avena fatua L. and )A. sterilis L. were germinated under a wide range of temperatures (5–30°C) and osmotic potentials (−25 to −1400 KPa) in order to characterize their responses to these two environmental factors. Although both species behaved similarly at moderate temperatures, different responses were observed at the two extremes. )A. sterilis germinated and emerged in a higher proportion than A. fatua at temperatures below 10°C but the opposite was true at temperatures above 20°C. Although the rates of these two processes were similar in both species up to 18°C, above this temperature the germination and emergence of )A. sterilis was considerably delayed in comparison with that of A. fatua. The effect of decreasing osmotic potentials in reducing the germination was more pronounced in A. sterilis than in A. fatua. However, no differences were observed in the emergence responses of either species. The adaptative advantages of these characteristics and their relationship with the geographic distribution of the two species is discussed.
Influence of environmental factors on the weed flora in crops in the Guadalquivir Valley
Authors: SAAVEDRA M. , GARCIA‐TORRES L. , HERNANDEZ‐BERMEJO E. , HIDALGO B.
Published: July 2006

The study was conducted on the weed flora of the main irrigated crops of the Guadalquivir Valley. The TWINSPAN (Two Way Indicator Species Analysis) method was applied for each crop separately to all the species present as well as to their degree of infestation. The results indicated that soil texture may markedly influence the flora, whereas the effects of pH and carbonate content were less important. The climatic differences found in the three areas studied were of little importance. The type of irrigation markedly influenced the flora, although it was always related to edaphic factors, especially texture and slope.

In general, the weed flora found in the crops can be divided into two communities. One is characterized by species such as Ridolfia segetum, Picris echioides, Phalaris brachystachys, Phalaris paradoxa and Chrozophora tinctoria and the second by Capsella bursa‐pastoris, Cyperus rotundus, Paspalum paspalodes, Digitaria sanguinalis, Sorghum halepense and Portulaca oleracea. The first community comprises weeds in the higher altitudes, further away from the riverbed, with a soil of clayey texture, a high slope and irrigated with sprinklers. The second community comprises the flora of flat areas, with sandy soils, located in the middle and low river terraces and furrow irrigated.
The role of light and alternating temperatures on germination of Polygonum aviculare seeds exhumed on various dates
Authors: BASKIN J. M. , BASKIN CAROL C.
Published: July 2006

The annual dormancy cycle was investigated in buried seeds of Polygonum aviculare L. exposed to natural temperature changes in Lexington, Kentucky, U.S.A. Seeds were exhumed monthly from December 1984 to February 1987 and tested in light (14‐h daily photoperiod) and continuous darkness at 12/12‐h daily alternating temperature regimes of 15/6, 20/10, 25/15, 30/15 and 35/20°C. During autumn and winter, seeds became non‐dormant, and in March 1985 they germinated to 95‐100% at all thermoperiods in light and to 7‐61% in darkness. Seeds remained non‐dormant during spring but became more specific in their germination requirements in early summer. During July and August 1985, seeds germinated to 17‐53% in light at 30/15 and 35/20°C but to 0‐10% at all other test conditions. By September, about 65% of the seeds were dormant, but the others were able to germinate under the higher alternating temperatures in light. A similar seasonal cycle was recorded in the following year through to the spring of 1987. The results confirm the seasonal pattern of dormancy in this species (Courtney, 1968) but indicate that alternating temperatures combined with light are important in determining germination potential in P. aviculare.
Orobanche ramosa L. (broomrape) control in tomato (Lycopersicon esculentum Mill.) with chlorsulfuron, glyphosate and imazaquin
Authors: KOTOULA‐SYKA E. , ELEFTHEROHORINOS I. G.
Published: July 2006

Chlorsulfuron, giyphosate and imazaquin were evaluated in pot and field studies for their efficacy in controlling broomrape (Orobanche ramosa L.) in tomato (Lycopersicon esculentum Mill.) in Northern Greece. All herbicides were applied four to five weeks after tomato transplanting, when the crop was at early flowering stage and broomrape had started to develop underground attachments. The number of emerged broomrape shoots and underground attachments were less affected by herbicide treatments than the dry weight, suggesting that the herbicides suppress the growth of broomrape rather than kill its underground organs. In the pot experiments, chlorsulfuron applied at 5 g AI ha−1 was the most effective treatment for broomrape control and the least toxic to the crop. Imazaquin and glyphosate applied at 37 and 180 g AI ha−1, respectively, controlled broomrape but imazaquin reduced crop yield. In the field, similar rates of glyphosate and higher rates of imazaquin were not toxic to the crop but were less effective on broomrape. Chlorsulfuron applied at 10 g AI ha−1 controlled broomrape emergence by 88%. When the herbicide was applied twice (5+10 g AI ha−1), it gave complete control of broomrape but delayed crop maturity. The yield of tomato was not increased as a result of these treatments because of low broomrape infestation and a short competition period.
Imazaquin, ein aussichtsreiches Herbizid für die Bekämpfung von Seiden–Arten (Cuscuta spp.) in Sojabohnen
Authors: LIU Z. O. , FER A. , LECOCO F. M.
Published: July 2006

L'imazaquine, un herbicide systémique, appliqué sur les feuilles de Phaseolus aureus parasité par Cuscuta lupuliformis est transporté dans la cuscute et fortement accumulé dans la partie apicale des tiges de ce parasite. Des résultats similaires sont obtenus avec le couple soja—Cuscuta australis. L'herbicide est rapidement dégradé dans le soja, mais actif sur la cuscute dont il inhibe la division cellulaire. La systémie phloémienne de l'imazaquine, sa sélectivité physiologique vis à vis du soja ainsi que son efficacité sur la cuscute font que cet herbicide est un produit prometteur pour la lutte curative contre la cuscute dans le soja, comme le montrent les essais préliminaires réalisés en serre.
Vegetative Bestimmungsmerkmale für Eragrostis‐Arten, die als einjährige Unkrautarten in Nordkamerun auftreten
Authors: LE BOURGEOIS T. , KAMGA F.
Published: July 2006

Neuf espfèces d'Eragrostis annuelles, adventices des cultures du Nord Cameroun sont différenciées à partir de quelques critères de l'appareil végétatif: E. viscosa, E. namaquensis, E. gangetica, E. turgida, E. pilosa, E. tremula, E. aspera, E. ciliaris, et E. cilianensis.
Soil metabolism of the herbicide napropamide in cereals, maize, sugar beet and vegetable field replacement crops
Authors: ROUCHAUD J. , GUSTIN F. , VAN HIMME M. , BULCKE R. , BENOIT F.
Published: July 2006

The metabolism of the herbicide napropamide has been studied in the field in the soil of replacement crops (cereals, corn, sugar beet, potato and several vegetables). Napropamide was soil applied in the autumn and the soil left fallow during the winter. Crops were sown in April of the following year and simulated the replacement crops that are grown in the event of failure of the first autumn‐sown crop. Trials were made twice, i.e. during the 1987‐1988 and 1988‐1989 crop seasons. The soil metabolism of napropamide was also studied in a rose nursery. Napropamide was transformed by microbiological processes in the soil into the corresponding monoethylamide and acid. These compounds did not generally accumulate in the soil, and their individual concentrations did not exceed that of residual napropamide during the observed growing seasons. The kinetics, metabolic pathways and agricultural implications of the herbicide are briefly discussed.
A review of the ecology and control of thistles in Australia
Authors: SINDEL B. M.
Published: July 2006

Studies on the ecology and control of thistles in Australia, particularly those related to pasture improvement, are reviewed, and the results used to interpret increases and changes in thistle dominance. Several hypotheses, based on ecological differences in the thistles, their life cycles and changes in the soil/seed environment may explain the changing species incidence in the field, and it is postulated that, within a restricted group of competing thistle species, it may be more meaningful to interpret these ecological differences in terms of ‘tolerance of unfavourable conditions’ than in terms of ‘optimal requirements’.

Alternative strategies for the control of thistles, including pasture competition, grazing management, the utilization of high soil fertility, and chemicals, are also assessed. It is re‐emphasized that the aim of any long‐term programme to control thistles, with or without the release of biological agents, should be the establishment and/or maintenance of a vigorous perennial pasture. The relative importance of different thistle species in Australian pastures and the ecology and dynamics of soil seed banks are identified as important areas for future thistle research.
Dynamics of competition between wild oats (Avena fatua L.) and winter cereals
Authors: COUSENS R. D. , WEAVER S. E. , MARTIN T. D. , BLAIR A. M. , WILSON J
Published: July 2006

This study examined the effects of competition on the growth of Avena fatua, winter wheat and winter barley. Plants were sampled at frequent intervals from replacement series experiments at two contrasting sites in the U.K. A. fatua was much slower to establish than the two cereals, but thereafter exhibited a faster rate of growth. In monoculture, it took a considerable time for A. fatua to reach a size equal to that of the cereals, but by the end of the experiments it was the largest of the three species. The change‐over from cereal dominance in mixtures to A. fatua tiominance was rapid, and in three cases coincided with cereal flag leaf emergence. In the fourth case, it appeared to coincide with the art of canopy height extension. At one site the rder of competitiveness at anthesis was A. fatua= barley>wheat, and at the other site the order was A. fatua>wheat>barley. In order to explain and predict differences between years and sites, more studies are required on morphological development in relation to abiotic variables.
An in‐vitro growth system for studying the parasitism of cowpea (Vigna unguiculata) by Striga gesnerioides
Authors: LANE J. A. , BAILEY J. A. , TERRY P. J.
Published: July 2006

An in‐vitro growth system for investigating the behaviour of S. gesnerioides on cowpea has been developed. The roots of young cowpea plants were spread over glass fibre filter paper in a shallow plastic tray, and a known number of germinated Striga seeds were placed on the cowpea root surface. This allowed the infection process of the parasite to be quantified. Good access to the host‐parasite association enabled the entire infection process to be easily monitored and tissue removed for cytological studies. Observations revealed for the first time that contact of S. gesnerioides radicles with host roots stimulated the development of radicular hairs and swelling of the tip of these radicles. Furthermore, penetration of cowpea roots by Striga was shown to be localized and to cause very little damage to the host roots. Swollen parasite tubercles developed on the surface of the roots only after the host stele had been penetrated by invading Striga cells. This growth system is suitable for in‐vestigating the mechanisms of host resistance. and also for rapidly screening cowpea germplasm for new sources of resistance to the Parasite. Resistant cowpea cultivars offer the best potential solution for control of this Parasite.
Study of diuron in soil solution by means of a novel simple technique using glass microfibre filters
Authors: GAILLARDON P. , FAUCONNET F. , JAMET P. , SOULAS G. , CALVET R.
Published: July 2006

Retention by a glass fibre filter of the liquid phase of a clay loam soil treated with 14C‐diuron provides a novel method for analysis of the herbicide in soil solution. At 26.3% (w/w) soil moisture content, less than 10% of the applied diuron was found in solution, and this percentage decreased slightly with diuron dose. The herbicide was rapidly adsorbed on soil during the first day, but adsorption continued and the concentration of diuron in solution could be further reduced by 36–50% during the following 6 days. Drying the soil after treatment, with possible crystallization of herbicide applied at high doses, tended to fix the solution concentrations. Ethanol (3% v/v) in soil water favoured herbicide dissolution. Increasing soil moisture to 36.3% (w/w) slightly decreased the concentration of the herbicide in solution, but increased the percentage held in solution. Frost and a drying‐rewetting cycle had little or no subsequent effect on diuron concentration in soil solution.
A model for prediction of yield response in weed harrowing
Authors: RASMUSSEN J.
Published: July 2006

A model is presented to describe crop yield response in weed harrowing. The selectivity of harrowing, crop yield response to soil covering, and the competitive strength of the weeds are all variables in the model, which is derived from the hyperbolic yield‐density relationship, and therefore accounts for the effects of weed density. An advantage of the modelling approach is that the yield response can be separated into two parts, one derived from the positive weed‐killing effect of harrowing, and the other derived from the negative crop‐covering effect. Simulation runs based on experimental data showed that crop damage, when it occurs, cannot be ignored, and may sometimes even dominate the positive weed‐killing effect. Possible scientific and practical applications of the model are discussed.
Induction of Striga seed germination by thidiazuron
Authors: BABIKER A. G. T. , PARKER C. , SUTTLE J. C.
Published: July 2006

Summary: Résumé: Zusammenfassung

Thidiazuron at 0.1 to 10 mg 1−1 induced concurrent germination and haustorium initiation in Striga asiatica (L.) Kuntze and S. hermonthica (Del.) Benth, but it had no effects on S. gesnerioides (Willd.) Vatke. Both millet and sorghum strains of S. hermonthica were equally responsive. The response of Striga seeds to thidiazuron increased with conditioning. Early applications of the compound induced some germination, but had adverse effects on the conditioning process.

Induction de la germination des graines de Striga par le thidiazuron

Le thidiazuron de 0,1 à 10 mg 1−1 a induit de façon conjointe le germination et l'initiation d'haustoria chez Striga asiatica et S. hermonthica, mais n'a pas eu d'effet sur S. gesnerioïdes. Les souches de S. hermonthica liées au millet et au sorgho ont un comportement équivalent. La réponse des graines de Striga au thidiazuron a augmenté par conditionnement préalable. Des applications précoces de produit ont induit quelques germinations, mais ont eu des effets contraires sur Ie processus de conditionnement.

Einleitung der Samenkeimung bei Striga‐Arten durch Thidiazuron

Mittels Thidiazuron‐Lösungen von 0,1 bis 10 mg 1−1 konnten eine gleichzeitige Keimung und Ausbildung der Haustorien bei Striga asiatica (L.) Kuntze und S. hermonthica (Del.) Benth. herbeigeführt werden, nicht jedoch bei S. gesnerioides (Willd.) Vatke. Der Rispenhirsen‐und der Sorghum‐Typ von S. hermonthica reagierten in gleichem Maße. Konditionierung der Striga‐Samen förderte die Wirkung von Thidiazuron. Frühe Anwendung des Wirkstoffs führte zu einer geringen Keimung, beeinträchtigte jedoch die Konditionierung.
Soil degradation of flumetsulam at different temperatures in the laboratory and field
Authors: LEHMANN R. G. , FONTAINE D. D. , OLBERDING E. L.
Published: July 2006

Summary: Résumé: Zusammenfassung

The degradation rate of the herbicide flumetsulam was examined in Hoytville clay soil at five temperatures and optimal moisture. Half‐lives were 246 days at 7.5°C, 115 days at 15.0°C, 49 days at 26.1°C, 34 days at 35.9°C, and 27 days at 44.0°C. Construction of an Arrhenius diagram (In k = ‐Ea/RT+In A) allowed the rate constant k to be calculated for any temperature T. When k was inserted into the first order rate equation (c = c0‐kt), the concentration of flumetsulam could be calculated on a monthly basis for any soil.

Predictions from this theoretical model were compared with data from three US field locations and found to accurately predict soil residues of flumetsulam under favourable moisture conditions, but not during periods of drought.

Degradation dans le sol du flumetsulam à differentes temperatures au laboratoire et en plein champ

Le taux de dégradation de l'herbicide flumetsulam a étéétudié dans un sol argileux de Hoytville à 5 temperatures et à l'humidité optimale. Les demi‐vies ont été de 246 jours à 7,5°C, 115 jours à 15°C, 49 jours à 26,1°C, 34 jours à 35,9°C et 27 jours à 44°C. L'établissement d'un diagramme d'Arrhenius (In k= Ea/RT+ln A) a permis de calculer le taux constant k à chaque température. Quand k est inserré dans la première partie de l'équation (c = c0e_kt), la concentration de flumetsulam peut être calculée sur une base mensuelle dans n'importe quel sol. Les prévisions de ce modèle théorique ont été comparérs avec des données de plein champ américaines, et on a noté que ces prévisions étaient correctes sous humidité favorable mais non pendant les périodes de sécheresse.

Abbau von Flumetsulam im Boden bei ver‐schiedenen Temperaturen unter Labor‐und Freilandbedingungen

Die Abbaurate des Herbizids Flumetsulam wurde bei 5 Temperaturstufen und optimalem Feuchtigkeitsgehalt in einem Hoytville‐Ton‐boden untersucht. Die Halbwertszeiten waren 246 Tage bei 7,5 °C, 115 Tage bei 15,0 °C, 49 Tage bei 26,1 °C, 34 Tage bei 35,9 °C und 27 Tage bei 44,0 °C. Die Anwendung der Ar‐rhenius‐Gleichung ermöglicht die Bestimmung der Abbau‐Konstante k bei jeder Temperatur T. Wenn k in die Abbaugleichung nach Kinetik 1. Ordnung eingefügt wird, können Flumet‐sulam‐Konzentrationen auf einer monatlichen Basis für jeden Boden abgeleitet werden. Vorhersagen nach diesem Modell wurden mil Rückstandswerten von 3 Standorten in den USA verglichen, wobei sich eine gute Übereinstimmung der beobachteten und simulierten Werte unter günstigen Feuchte‐bedingungen ergab, nicht jedoch fur Trocken‐perioden.
Aspects floristico‐agronomiques des mauvaises herbes de la région du Loukkos (Maroc)
Authors: BOUHACHE M. , BOULET C. , CHOUGRANI A.
Published: July 2006

Résumé: Summary: Zusammenfassung

Cent vingt champs de céréales, légumineuses et betterave à sucre de la région du Loukkos (Nord Quest du Maroc) ont été prospectés selon un échantillonnage stratifié. Ainsi, 244 espèces de mauvaises herbes appartenant à 37 families botaniques ont été inventoriées. Trois families, Asteraceae, Fabaceae et Poaceae ont fourni 41.8% de l'effectif spécifique. Les dicotylédones (82.3%), les annuelles (82.8%) et l'élément floristique méditerranéan (63.9%) sont prépondérants et caractérisent cette flore. L'étude agronomique nous a permis de distinguer 45 espéces ayant une nuisibilite non négligeable vis à vis des cultures prospectées. Les espèces communes à ces derniàres représentent 51.5, 56.6 et 60.7% de 1'effectif des espèces problématiques relevées pour la betterave à sucre, les céréales et les légumineuses, respectivement.

Floristic‐agronomic aspects of weeds in the Loukkos region of Morocco

One‐hundred and twenty fields of cereals, legumes and sugar beet were surveyed by stratified sampling in the Loukkos region (north‐west Morocco). In total, 244 weed species belonging to 37 plant families were recorded. Three families, the Asteraceae, Fabaceae and Poaceae accounted for 41.8% of the species. Dicotyledons (82.3%), annuals (82.8%) and the mediterranean floristic element (63.9) were predominant and characterized the weed flora. The agronomic study made it possible to distinguish 45 species causing appreciable problems to the crops surveyed. The weeds common to the three types of crop comprised 51.5%, 56.6% and 60.7% of the problem species in sugar beet, cereals and legumes, respectively.

Floristisch‐agronomische Aspekte der Verbreitung von Unkräutern in der Umgebung von Loukkos, Marokko

In der Umgebung von Loukkos in Nordwest‐marokko wurde die Unkautflora von 120 Getreide‐Gemüse‐und Zuckerrübenfeldern mit insgesamt 244 Arten aus 37 Familien erfaßt. 41.8 % der Arten gehörten zu den Asteraceae, Fabaceae und Poaceae. Dikotyle (82.3 %), Annuelle (82.8 %) und mediterrane Florenelemente (63.9 %) dominierten und charakterisierten die Flora. Landwirtschaftlich betrachtet konnten 45 Arten fü die untersuchten Kulturen als deutlich problematisch eingruppiert werden. In den 3 Kulturengruppen kamen 56.6, 60.7 bzw. 51.5% der Arten allgemein vor.
A comparison of herbicide bioassays in cell cultures and whole plants
Authors: OLOFSDOTTER M. , OLESEN A. , ANDERSEN S. B. , STREIBIG J. C.
Published: July 2006

Summary: Résumé: Zusammenfassung

Dose‐response curves were established for the herbicides chlorsulfuron, metsulfuron‐methyl, ethametsulfuron‐methyl, imazamethabenz and glyphosate. The plant species wereDaucus carota L. and Triticum aestivum L. in cell culture assays, and D. carota L., T. aestivum L., Stellariamedia L., Chenopodium album L. and Avena sativa L., in whole plant assays. Potency ranking of herbicides were similar in the two assays. Low doses of herbicide stimulated growth in both assays, but stimulation was greater in cell cultures. Image processing measured growth in cell cultures and was more sensitive to small differences in responses than manual counts of cell colonies. Dose‐response curves had the same shape in both assays, but cell cultures were more sensitive than were whole plants.

Comparaison d'essais biologiques d'herbicides effectués sur cultures de cellules et sur plantes entiéres

Des courbes dose‐effet ont étéétablies pour les herbicides metsulfuron‐methyl, ethametsulfuron‐methyl, imazamethabenz et glyphosate. Les espèces végétales étaientDaucus carota L. et Triticum aestivum L.en cultures de cellules, etD. carota L., T. aestivum L., Stellaria media L., Chenopodium album L. et Avena sativa L.dans les essais sur plantes entières. Le classement d'efficacité des herbicides était le meme dans les deux types d'essais. Les faibles doses d'herbicides stimulaient la croissance dans les deux essais mais la stimulation était plus importante en cultures de cellules. La mesure par analyse d'image de la croissance des cultures de cellules était plus sensible à de faibles différences que le comptage manuel des colonies. Les courbes dose‐effet avaient la meme forme dans les deux essais mais les cultures de cellules étaient plus sensibles que les plantes entières.

Vergleich von Herbizid‐Biotests mit Zellkulturen und ganzen Pflanzen

Fur die Herbizide Chlorsulfuron, Metsulfuronmethyl, Ethametsulfuron‐methyl, Imazamethabenz und Glyphosat wurden Dosis/Wirkungs‐Kurven erstellt. Die in den Zellkulturen verwendeten Pflanzenarten warenDaucus carota L. und Triticum aestivum L., und bei den Tests mit ganzen Pflanzen D. carota L., T. aestivum L., Stellaria media L., Chenopodium album L. und Avena sativa L.Die Reihenfolge der Herbizide hinsichtlich ihrer Wirksankeit war in beiden Tests ahnlich. Niedrige Herbiziddosen steigerten in beiden Tests das Wachstum, in den Zellkulturen jedoch deutlicher. Bei den Zellkulturen war die Bildanalyse‐Messung fur das Erkennen geringer Unterschiede empfindlicher als das Auszahlen der Zellkolonien. Die Dosis/Wirkungs‐Kurven hatten fur beide Testmethoden den gleichen Verlauf, aber auch hier erwiesen sich die Zellkulturen empfindlicher als die ganzen Pflanzen.