bluuebunny/crossref_metadata_2025 huggingface dataset:
Comportement germinatif des graines d'Amaranthus retroflexus L. recoltées dans les conditions naturelles
Authors: CHADOEUF‐HANNEL RÉGINE , BARRALIS G.
Published: July 2006

L'influence de l'époque de levée des plantes porte‐graines et de la période climatique de dissémination sur la dormance des graines d'Amaranthus retroflexus L. prélevées uniquement au niveau de l'inflorescence principale a étéétudiée.

Dans les conditions favorables de germination (30 C), les graines récoltées le plus tardivement (mois de novembre) sont, à leur dissémination, les moins donnantes et celles produites très tôt (mois d'août) les plus dormantes. Mais après conservation au sec pendant 60 jours, les graines ont une capacité germinative voisine de 100%, quelle que soit leur origine.

Dans les conditions moins favorables de germination (20 C), les graines récoltées sur les plantes qui se sont développées très tard (juinjuillet) germent miex que celles prélevées sur les plantes apparues très tôt (mars‐avril). Ces différences ne sont pas supprimées par la conservation au sec.

A la lumière de ces données, les auteurs discutent des interactions des effets entre les facteurs climatiques et l'état physiologique des plantes sur l'aptitude à germer des graines disséminées naturellement.
The production and shedding of Alopecurus myosuroides Huds. seeds in winter cereals crops
Authors: MOSS S. R.
Published: July 2006

Seed shedding from heads of Alopecurus myosuroides occurred from late June to late August at most locations. Most seeds were shed before winter wheat (Triticum‐aestivum L.) was harvested hut at two winter barley (Hordeum sativum L.) sites, only 50% of seed was shed prior to harvest. The viability of seeds shed at the start and end of the shedding period tended to be lower than that at peak shedding time in late July and early August. There were large differences between sites in the viability of the total amount of seed shed. The results of viability tests based on the presence of full caryopses and germination in pots of sterile soil were similar. Assessments of head numbers and head length were significantly correlated with total seed production. Head length, but not head number assessments, were also significantly correlated with viable seed production.
Grass weed control with herbicide‐treated crop seeds
Authors: DALE J. E.
Published: July 2006

Fluazifop‐butyl applied in lung oil at rates of 4.4 to 0.5 g a.i. kg−1 soybean seeds was evaluated in the glasshouse for control of Eleuisine indica. Soybean seeds pretreated with herbicide at 4.4 to 2.1 g a.i. kg−1 gave 100% control of E. indica at the highest sowing rate of four seeds per pot and 90 to 80% control when sowed at one seed per pot. Soybeans were not injured by the seed treatment. Cotton seeds pre‐treated with fluazifop at 2.2 g a.i. kg−1 seeds and sown 4 cm apart in a row across a 20 ± 20cm tray of soil containing seeds of Echinochloa crus‐galli produced a weed‐free band 12 cm wide centred on the row of cotton, without injury to cotton. CGA‐82725 (2‐propynyl 2‐(4‐((3, 5‐dichloro‐2‐pyridinyl)oxy)phenoxy) propanoate) at 2–3 g a.i. kg−1 seeds was as effective as 4–4 g fluazifop‐butyl in controlling E. indica. but growth of soybean was retarded. Sethoxydim gave less control than fluazifop butyl at comparable rates and did not injure soybeans.
Interference between velvetleaf (Abutilon theophrasti Medic.) and soybean (Glycine max (L.) Merr.) II. Population dynamics
Authors: DEKKER J. , MEGGITT† W. F.
Published: July 2006

Two field experiments were conducted to determine the effect of changes in Abutilon theophrasti and soybean population numbers through the growing season on soybean dry weight and seed yields. Whether in mixtures or monoculture, the rate of mortality of both species was constant through the growing season. In general, the greater the initial population of either species the greater the rate of mortality through the growing season. Evidence presented supports the hypothesis that A. theophrasti has the adaptive ability of differential mortality at different populations when in mixed stands with soybean and when grown alone and that soybean lacks this ability when mixed with A. theophrasti. This results in smaller, less productive, individual soybean plants.
Basis for antagonism of paraquat phytotoxicity to barley by MCPA dimethylamine*
Authors: O'DONOVAN J.T. , O'SULLIVAN P. A. , CALDWELL C.D.
Published: July 2006

Summary: Résumé: Zusammenfassung

MCPA dimethylamine in a mixture with paraquat reduced the disruptive effects of paraquat on leaf cell membrane integrity in excised barley (Hordeum vulgare L.) leaf segments. Uptake or translocation of 14C‐paraquat over 24 h was not affected when mixed with either MCPA dimethy‐lamine or MCPA mixed butyl ester. In treatments followed by a period of dark, uptake and translocation of 14C‐paraquat was increased compared to treatments followed by a period of light. A mixture of technical paraquat dichloride and technical MCPA dimethylamine in aqueous solution yielded a dark brown precipitate. All of the paraquat ion was present in the supernatant. The absorption spectrum of the supernatant exhibited a strong maximum of 390 nm and a lesser one at 610 nm. The spectrum was close to that produced by aqueous mixtures of paraquat and dimethylamine. In greenhouse studies the phytotoxicity of the supernatant to barley was less than an equivalent amount of paraquat alone and equal to that of the complete paraquat‐MCPA dimethylamine mixture. The presence of dimethylamine alone resulted in an early enhancement of paraquat activity. Spot application of an aqueous suspension of the precipitate to rapeseed (Bras sica campestris L.) resulted in slight epinastic effects but these were considerably less than when an equivalent amount of MCPA acid was applied. The effects of the precipitate were restricted to the treated leaf whereas the effects of MCPA acid were evident throughout the plant. The results suggest a chemical interaction between the dichloride salt of paraquat and the dimethylamine salt of MCPA with the production of two compounds with comparatively less biological activity.
Influence of glyphosate on selected plant processes
Authors: COLE D.J. , CASELEY J.C. , DODGE A. D.
Published: July 2006

Biochemical effects of glyphosate have been examined with a variety of plant materials using mostly merislematic or actively growing tissues. The accumulation of chlorophyll was severely retarded and photosynthetic CO2 uptake was inhibited to a lesser extent. These inhibitory effects could not be alleviated by the simultaneous admixture of divalent cations. Glyphosate enhanced the initial substrate‐induction of nitrate reductase, but repressed induction of nitrite reductase, in Ihe latter case correlating with both inhibition of chlorophyll accumulation and CO2 uptake. Inhibition of macromolecule synthesis in single node buds of Agropyron repens(L.) Beauv. was due partly to inhibition of 14C‐precursor uptake. The specific activity of soluble acid phosphatase was enhanced as was the evolution of ethane. Ethylene production was not greatly affected. A marked decrease in microsomal protein was observed but the specific activities of several microsomal enzymes did not decline. Glyphosate had little inhibitory effect on the activity of microsomal ATPases in vitro.
The effect of substituted urea herbicides on the growth of excised tomato roots
Authors: GAUVRIT C. , ROUGétéT E.
Published: July 2006

The action of 23 herbictdal substituted ureas on the growth of excised tomato roots was studied in order to détérmine whether there is a link between the effects of these herbicides on oxidative phosphorylation and on the growth of non‐photosynthetic tissues. Fourteen of these herbicides were inhibitory; chlortoluron and TBU were stimulatory but only in the light. Substituted ureas known to affect plant mitochondria inhibited root growth but to a lesser extent than some which had no action on mitochondria. No clear relationship was found between actions on mitochondria and on root growth. It is suggested that targets other than photosynthesis and oxidative phosphorylation exist for some substituted ureas.
Effect of heat‐treating soil and straw on the subsequent adsorption of chlortoluron and atrazine
Authors: EMBLING S.J. , COTTERILL E.G. , HANCE R.J.
Published: July 2006

The adsorption of chlortoluron and atrazine was measured on a range wheat straw residues that had been heated for periods of 1–5 min at temperatures up to 700°C and and on three soils that had been heated at up to 250°C for 1–5 min.

Adsorption of both compounds by straw ash increased with increasing temperature of pretreatment. Atrazine adsorption by any of the soils was not changed markedly chlortoluron absorption was increased with two of the three soils. The results are discussed in terms of the changes in organic functional groups, that are likely to have been produced by the treatment, in relation to the adsorption mechanisms thatmay operate on the two compounds.

Adsorption of chlortoluron by mixtures of ash and soil was less than the sum of the adsorption capacities of each component on its own in the cases of two out of three soils.

It is concluded that the effect of straw burning on herbicide performance in the field will be variable but could be substantial.

Le chauffage du sol et du chaume: influence sur l’adsorption ultérieure de chlortoluron et de l'atrazine
Changes in the incidence of ragwort (Senecio jacobaea L.) infestation of grassland over a 4‐year period in NE Scotland
Authors: FORBES J. C.
Published: July 2006

A roadside survey of 4749 fields in eight areas of NE Scotland was conducted annually from 1979 to 1982. The proportion of grass fields infested with ragwort remained steady at 18–19% from 1979 to 1981 but fell to 13·5% in 1982. This fall resulted from fewer fields becoming newly infested and from more fields that had remained in grass ceasing to be infested. The proportion of infested fields remaining in grass that showed a reduction of two or more points on a 0–5 logarithmic scale of ragwort density (a possible indication of the frequency of control measures) was 24·0% in 1979–1980, 21·7% in 1980–1981 and 36·3% in 1981–1982.

The incidence of ragwort infestation was consistently higher in some areas than in others and was not related to the proportion of arable crops. The change in incidence of infestation varied greatly between different areas, as did the proportion of infested fields whose score on the 0–5 scale fell by two or more points. In 1979–1980 and 1980–1981 this proportion had to exceed 22% to effect a net decrease in the incidence of infestation in an area, but in 1981–1982 no relationship was evident between these two measures of change. The incidence of infestation in all areas increased with increasing sward age but one area (Moray and Nairn) had a much higher proportion of young grass infested than any of the others. Over 99% of ragwort infestations consisted of Senecio jacobaea, infestations of S. aquatints Huds. being rare.
Weed competition and control in sugarcane
Authors: IBRAHIM A.A.S.
Published: July 2006

Losses of about 40% in cane yields due to natural stands of weeds were found in experiments conducted in sugarcane var. Co 527 in the year of planting at Guneid Sugarcane Research Station, Sudan. Weed competition lowered millable stalks per metre row by 32%, stalk height by 24%, stalk thickness by 15% and number of nodes per stalk by 14%. Tillering was the growth phase most affected by weed competition.

Cane yields were increased as number of hand weedings increased, but four weedings were not markedly better than three. The average yield (67·04 t ha−1) obtained from four weedings was not significantly (P= 0·05) better than that of three weedings carried out at 3, 6 and 9 weeks after cane planting.

Juice analysis components were also affected by weeds and a 15% reduction in sucrose recovery was recorded. Reductions in the other components were only 4–7%.

Atrazine and diuron (3·3 kg ha−1), metribuzin (2·4 kg ha−1) and metribuzin (1·3 kg ha−1) in tank mixture with diuron (1·5 kg ha−1) gave excellent residual weed control of the dominant weed species, Ipomoea cordofana Choisy., Brachiaria eruciformis (Sm.) Griseb., Corchorus fascicularis Lam., Ocimum basilicum L. and Dinebra retroflexa (Vahl) Panz., for most of the first growing season. Excellent control of weeds achieved by the herbicide treatments resulted in comparable yields to frequently‐weeded cane. These herbicides were not phytotoxic to sugarcane var. Co 527.
Potential safeners for protecting sorghum (Sorghum bicolor (L.) Moench) against chlorsulfuron, fluazifop‐butyl and sethoxydim*
Authors: HATZIOS KRITON K.
Published: July 2006

In greenhouse studies, the efficacy of the herbicide safeners NA(1,8‐naphthalic anhydride), R‐25788 (N,N‐diallyl‐2,2‐dichloroacetamide), cyometrinil and CGA‐92194 [N‐(1,3‐dioxolan‐2‐yl‐methoxy)imino‐benzeneaceto‐nitrile] in protecting grain sorghum (Sorghum bicolor (L.) Moench, cv. ‘Funk G623’) against injury from pre‐emergence or early post‐emergence applications of the herbicides chlorsulfuron, fluazifop‐butyl and sethoxydim was examined. NA as a seed dressing at 0·5 or 1·0% (w/w) was the most effective of the four safeners and offered partial to good protection to sorghum against injury from the lower rates of pre‐emergence applications of all three herbicides. R‐25788 was totally ineffective as a sorghum protectant against fluazifop‐butyl injury but it did antagonize partially the injurious effects of the lower rates of sethoxydim and chlorsulfuron on sorghum. Cyometrinil and CGA‐92194 offered partial protection to sorghum against injury from the lowest rate of all herbicides but their efficacy against higher rates of the three herbicides was very limited. None of the four safeners was effective in protecting grain sorghum against injury from post‐emergence applications of the three herbicides tested.
Etat actuel de l'infestation parSolanum elaeagnifoliumCav. pour les différentes cultures du périmètre du Tadla (Maroc)
Authors: TANJI A. , BOULET C. , HAMMOUMI M.
Published: July 2006

Les auteurs présentent l'état actuel de l'infestation des cultures parSolanum elaeagnifoliumCav. dans l'ensemble de la région agricole du Tadla (Maroc Central). En utilisant la méthode des profils écologiques, il apparaît d'une part, que le périmètre des Béni Amir (Nord du Tadla) est beaucoup plus infesté que celui des Béni Moussa (Sud du Tadla) et d'autre part, que les cultures les plus envahies sont celles de printemps (coton, maïs, sésame). Une carte adjointe au texte permet de préciser la répartition de l'espèce au niveau de cette région.
Use of electricity to control bolters in sugar beet (Beta vulgaris L.): a comparison of the electrothermal with chemical and mechanical cutting methods
Authors: DIPROSE M. F. , FLETCHER R. , LONGDEN P. C. , CHAMPION M. J.
Published: July 2006

A machine was built to kill reproductive plants (‘bolters’) in sugar beet by high‐voltage electricity. A generating system producing 10, 13 or 17 kV each at 54 kW was connected to a set of guarded electrodes spanning twelve rows, suspended 5–15 cm above the top of a sugar‐beet crop. With 13 kV the system travelling at 5 km h−1 could clear a light‐to‐moderate infestation of bolters at a rate of 2·4 ha h−1 with the tractor's diesel‐fuel consumption at 3·51 ha−1. In 1979, the electrothermal machine, used twice, reduced viable seed returns by 83%; the flail mower used once or twice by 44 and 76–84%; the wire reel mower used once or twice by 45 and 80–87%; and the roller chemical applicator used once by only 13%. Further trials were made in 1981 with an improved electrothermal machine, a rope wick applicator and a flail mower when all gave over 90% control of viable seeds. The electrothermal machine killed between 38 and 41% of bolters compared with 65% for the chemical applicator. The flail mower did not kill any plants.

Although possessing many advantages, the electrothermal machines are heavy and more expensive than alternative methods. Development has ceased in the U.K. on electrical weed control but one company in the U.S.A. is selling such equipment.
Dégradation catalytique de carbamates herbicides deposés sur bentonites homoioniques. I. Cas du barbane
Authors: SABADIE J. , BASTIDE J. , COSTE C. M.
Published: July 2006

Rásumá

La dégradation chimique en phase sèche du barbane a étéétudiée après dèpôt à température ambiante sur diverses bentonites homoioniques (Cu2+; Ag+). La bentonite Ag+ présente une réactivité particulièrement intéressante. Le schéma général de cette dégradation a étéétabli.
Effect of CGA 123407 as a safener for pretilachlor in rice (Oryza sativa L.). Recordings of elongation rates of single rice leaves
Authors: CHRIST R. A.
Published: July 2006

The elongation rates of single attached leaves of rice (Oryza saliva L.) were recorded. The effect of pretilachlor on the elongation rates and the safening effect of CGA 123407 [4, 6‐dichloro‐2‐phenyl‐pyrimidine] were evaluated. Both chemicals were applied to the roots in a nutrient solution.

Pretilachlor reduced leaf elongation in concentrations as low as 300 μg−1 (9–6 × 10−7 M) but. for combination trials with the safener, 3 mg 1−1 (9–6 × 10−6 M) was used. in combination with pretilachlor the safener prevented damage in very low concentrations. The ratio of pretilachlor to safener, 30:1, was sufficient when both chemicals were given to roots in nutrient solution, although for field work the ratio of 3:1 is recommended. The safener alone did not influence the elongation rate of rice leaves in the concentrations used. When pretilachlor was given to the roots and CGA 123407 to the shoot, some delay in the herbicidal action was recorded but even with high concentrations of the safener no continuous safening effect was achieved.

CGA 123407 was also effective when given previous to the herbicide. This proved true even with a 2‐day interval between safener uptake and application of the herbicide. When pretilachlor was given first, the safener effected recovery to various degrees when given 1–4 days after the herbicide application.

When pretilachlor was given for a limited period of time only (1–3 days) and was subsequently removed from the nutrient solution, recovery of the plant occurred. It is speculated that the safener either helps this recovery or else competitively prevents the herbicide from occupying the sites of action or from keeping them occupied for a long period of time.
Competition between annual weeds and vining peas grown at a range of population densities: effects on the weeds
Authors: LAWSON H. M. , TOPHAM P. B.
Published: July 2006

Linear regression of dry weight of weeds against crop density, together with the use of diversity indices and principal component analysis were used to derive information about changes in the behaviour of annual weeds over the growing season and in response to a wide range of crop densities in vining peas Pisum sativum L. Using linear regression it was possible to quantify reductions in weed dry weights per unit increase in crop plant density The ‘weed losse’ factor was acceptably consistent between experiments. Indices examining richness and evenness showed that numbers of weed species declined with increasing crop density and as the season progressed, but although species evenness became less at successive sampling dates the presence of a pea crop, whatever its density, did not radically alter the composition of the weed flora. Principal component analysis demonstrated that although there was competition within the weed flora, the crop did not replace the dominant weed species on high density plots, but reduced growth of all weed species alike.
Temperature requirements for germination of buried seeds of Aethusa cynapium L.
Authors: ROBERTS H. A. , BODDRELL J. E.
Published: July 2006

Freshly‐collected mature mericarps of Aethusu cynapium were dormant, but some germinated at alternating (16 h low/8 high) temperatures when the seed coverings were removed. Burial during winter increased percentage germination and the temperature range over which it took place. In late spring the range narrowed, first at low and then at higher temperatures, widening again in autumn. Moist storage at both low (4°C) and high (30°C) temperatures overcame dormancy, but exposure to 30°C inhibited subsequent germination at low temperatures. Germination of intact mericarps was consistently lower than that of de‐coated seeds. The cyclic change in dormancy status of the seeds appears to interact with the restricting effects of the seed coverings and perhaps other factors in determining the consistent pattern of spring emergence in A. cynapium.
Tolerance of spring wheat (Triticum aestivum L.) to trifluralin deep‐incorporated in the autumn or spring
Authors: O'SULLIVAN P. A. , WEISS G. M. , FRIESEN D.
Published: July 2006

Field experiments at Lacombe on a Ponoka loam soil (9·6% organic matter) during 1982 and 1983 investigated the tolerance of spring wheat (Triticum aestivum L.) cv. Neepawa in a weed free situation to trifluralin applied at 0·0–3·0 kg ai ha−1 in the autumn or spring and incorporated to a depth of 10 cm. Rates of trifluralin above 1·0 kg ai ha−1 applied in the autumn or spring reduced the percent stand of wheat compared to an untreated control. Two weeks after emergence the crop showed 37 or 47% injury indicated by delayed growth, following application at 1·0 kg ai ha−1 in the autumn or spring, respectively. The wheat recovered throughout the course of the growing season. At harvest, trifluralin applied in the autumn or spring at rates below 1·0 kg ai ha−1 caused a yield increase while higher rates caused a yield decrease compared to the untreated control. Spring application caused a greater yield loss than autumn application. The tolerance of spring wheat to trifluralin at rates required for weed control (1·1 kg ai ha−1 or higher) on this soil type is marginal.
Improved control of Stellaria media (L.) Vill in leys with Trifolium repens, using bentazone and benazolin with additives
Authors: TURNER D. J.
Published: July 2006

In pot experiments, mixtures of ammonium sulphate with surfactants or oil additives increased the phytotoxicity of commercially formulated bentazone (‘Basagran’) to Stellaria media (chickweed). Ammonium sulphate with a proprietary oil adjuvant Actipron had similar effects with benazolin potassium salt, but not with an ethyl ester formulation of benazolin. The phytotoxicity of bentazone and benazolin salts to Trifolium repens (white clover) and Lolium perenne (perennial ryegrass) was almost unaffected by these additives. In a field experiment, a mixture of ammonium sulphate with Actipron improved the control of S. media by bentazone and benazolin salts.

Oils and surfactants markedly increased rates of entry of 14C bentazone into leaves of S. media, white clover and Chrysanthemum segetum. Ammonium sulphate sometimes had similar effects but on other occasions reduced uptake. In some circumstances the additives apparently interacted synergistically, to increase uptake of labelled herbicide into the leaf or to enhance its transport within the plant. In these test species, differential absorption of bentazone could not explain differences in species susceptibility, suggesting that the main cause of resistance was the ability of plants to degrade the herbicide.
Population studies on Pennyroyal Mint (Mentha pulegium L.) I. Germination and seedling establishment
Authors: PANETTA F. D.
Published: July 2006

Very few seeds of M. pulegium germinated in the absence of light, but relatively high levels of germination were attained over a wide range of temperatures when seeds were exposed to light. This response to temperature was reflected in patterns of seedling appearance in several field sites, where new plants were recorded between autumn and early summer. Initial mortality rates differed between cohorts which occurred within and outside a pasture community, and were higher in the presence of pasture species. Seedlings survived prolonged periods of inundation and new plants were detected under water to a depth of 10 cm. The capacity for growth under water is considered to be an important aspect of the ability of M. pulegium to invade and persist in sites which are flooded seasonally.
Population studies on Pennyroyal Mint (Mentha pulegium L.) II. Seed banks
Authors: PANETTA F. D.
Published: July 2006

An investigation of seed banks found under populations of M. pulegium located within and outside pasture systems revealed that seed densities were sixteen times greater when this species occurred in pastures. The sizes of seed banks were not positively related to current seed production, but larger seed banks appeared to be associated with higher levels of soil disturbance arising from trampling by grazing stock. Densities of buried seed were very high under pasture populations (range 55 000–176 000 m−2), which illustrates the impracticality of attempts to eliminate M. pulegium from this type of community.
Unrestricted growth, tuber formation and spread of Cyperus esculentus L. in Zimbabwe
Authors: LAPHAM J.
Published: July 2006

The unrestricted growth and clonal spread from individual tubers of Cyperus esculentus L. were studied in Zimbabwe. Clonal material, collected from the Trelawney area, was grown in a square arrangement in the field with a 5 m spacing between original tubers. Growth was recorded at approximately monthly intervals for 2 years. The natural logarithm of clonal spread (m per month) was positively correlated to temperature and rainfall. Most growth occurred from November to March, a period of optimal moisture and temperature conditions. There was little growth during the remainder of the year. The changes in clonal spread during the year are expressed mathematically and incorporate two parameters of growth; one describes the rate of growth and the other predicts the radius once growth ceases

Tuber numbers increased exponentially from December‐April, the rate of tuber production being greater in the first than in the second year of growth. Tuber production was greatest during March, April and December, 1980. Dormancy of the tubers decreased during the cooler months from May to August. The value of describing unrestricted clonal growth, and conditions favouring tuber production, are discussed.
Influence of temperature on the activity of AC 222,293 against Avena fatua L. and Alopecurus myosuroides Huds.
Authors: PILLMOOR J. B.
Published: July 2006

Foliage applications of AC 222,293 were more active against Alopecurus myosuroides Huds. plants growing at high (26/16°C day/night) compared to either medium (16/10°C) or low (11/7°C) temperatures. Soil activity was unaffected by temperature. Enhanced activity against A. myosuroides required exposure to the high temperatures for only 24 h immediately post spraying and correlated with the accumulation of greater levels of the biologically active acid in the apical meristem region during this period.

Both foliage and soil activity of AC 222,293 were greatest against Avena fatua L. plants growing at medium (16/10°C) compared to either high (26/16°C) or low (11/7°C) temperatures. Foliar activity decreased slowly with increasing periods of high temperatures post spraying and then only at doses lower than those recommended for field use. Reduced performance at the high temperatures correlated with lower levels of the biologically active acid in the meristem region, despite greater uptake and translocation. This was due to increased metabolism of the parent herbicide and formation of metabolites other than the free acid.
Germination of Chromolaena odorata (L.) K. & R. achenes: effect of temperature, imbibition and light
Authors: ERASMUS D. J. , VAN STADEN J.
Published: July 2006

Summary: Résumé: Zusammenfassung

Chromolaena odorata (L.) K. & R. (= Eupatorium odoratum L.) has invaded large areas of the coastal belt of Natal province in South Africa. Propagation is predominantly by means of windborne achenes. The germination of these achenes was investigated. Of the temperatures tested, alternating 15/30°C was optimal for germination. These achenes are positively photoblastic and an imbibition period prior to exposure was required to sensitize the achenes to light. The promotive effect of red light on the germination of imbibed achenes could be reversed by subsequent exposure to far‐red light while the inhibitory effect of far‐red light could be nullified by a subsequent red light treatment. This is typical of a phytochromemediated germination response.

Germination d'akènes de Chromolaena odorata (L.) K. & R.: effets de la température, de l'imbibition el de la lumière

Chromolaena odorata (L.) K. & R. (= Eupatorium odoratum L.) a envahi de grandes superficies dans le littoral de la province de Natal en Afrique du Sud. La plante se répand surtout par moyen d'akènes portés par le vent. La germination de ces akènes a fait l'objet d'une étude. Parmi les températures essayées, 15/30°C s'est révélée optimale pour la germination. Les akènes font preuve d'une photoblasticité positive et pour les sensibiliser à la lumière, il leur faut une période d'imbibition avant de les y exposer. La promotion de germination provoquée par la lumière rouge chez les akènes imbibés a pu etre inversée par une exposition ultérieure à la lumière extrême‐rouge (700 à 750 nm) tandis que l'effet inhibiteur de celle‐ci s'est trouvé annulé par un traitement ultérieur à la lumière rouge. Cette réaction est caractéristique d'une germination réglée par le phytochrome.

Die Keimung von Achaenen von Chromolaena odorata (L.) K. & R.: der Einfluss von Temperatur, Quellung und Licht.

Chromolaena odorata (L.) K. & R. (= Eupatorium odoratumL.) hat sich auf grossen Flächen des Küstengürtels der Provinz Natal (Südafrika) ausgebreitet. Durch den Wind verbreitete Achaenen sind hauptsächlich für die Vermehrung verantwortlich. Thema der vorliegenden Untersuchung war die Keimung dieser Achaenen. Alternierende Temperaturen von 15° und 30°C waren optimal für die Keimung. Die Achaenen waren positiv photoblastisch; eine Quellungsperiode war notwendig um die Achaenen für die Lichtreaktion zu sensibilisieren. Der die Keimung vorgequollener Achaenen fördernde Einfluss von Rotlicht konnte durch eine nachfolgende‘Fern‐Rot'‐Exposition rückgängig gemacht werden. Hingegen wurde der Hemmungseffekt von ‘Fern‐Rot’ durch eine darauffolgende Rotlicht‐Exposition aufgehoben. Dieser Befund ist charakteristisch für eine phytochromregulierte Samenkeimung.
Quelques aspects de la germination des caryopses de Leersia oryzoides (L.) Sw.
Authors: ROSA MARIA L. , CORBINEAU FRANÇOISE
Published: July 2006

Résumé: Summary: Zusammenfassung

Les semences de Leersia oryzoides (L.) Sw. germent mal au moment de leur récolte parce qu'elles sont dormantes. Leur germination exige des températures élevées, mais une alternance de températures fraîches et de températures élevées est plus favorable. La dormanee résulte en partie de l'action inhibitrice des glumellcs qui sont capables de fixer de l'oxygène, ce qui réduit la quantité de ce gaz disponible pour le grain. Elle s'élimine très lentement au cours de la conservation au sec ou pendant un prétraitement au froid humide. A 20°C, les caryopses nus germent mieux en hypoxie (3 à 15% d'02) qu'à l'air et un excès d'oxygène est très nocif. A 30°C, par contre, leur germination reste possible dans des atmosphères enrichies en ce gaz (50 à 100%d'02). Les caractéristiques physiologiques de la dormance et de la germination de ces semences sont discutées en relation avec l'adaptation de la mauvaise herbe à son environnement.

Some aspects of the germination of caryopses of Leersia oryzoides (L.) Sw.

Freshly harvested seeds of Leersia oryzoides (L.) Sw. show low germination as a result of dormancy. Germination requires high températures but is improved at a diurnal alternation between high and low temperature. Dormancy is partially due to inhibition by the glumes which are capable of oxygen uptake and thus reduce the amount of oxygen available to the grain. This dormancy is gradually reduced during dry storage, or low temperature incubation. Germination of naked caryopses at 20°C is higher at sub‐aimospheric 02 (3–15%) than in normal air, while excess oxygen is noxious. At 30°C, however, germination takes place even in 02‐enriched atmospheres (50–100%), The physiological characteristics of dormancy and of germination of this species are discussed in relation to the adaptation of this weed to its environment.

Uber die Keimung der Karyopsen von Leersia oryzoides (L.) Sw.

Die Samen von Leersia oryzoides (L.) Sw. befinden sich zur Zeit der Ernte in einer Ruhephase; sie keimen deshalb zu diesem Zeitpunkt Schlecht. Zur Keimung sind höhere Temperaturen erforderlich. Ein Wechsel zwischen niederen und höheren Temperaturen ist jedoch noch günstiger. Diese Ruhezeit wird z.T. durch eine Hemmwirkung der Deckspelzen, welche Sauerstoff fixieren können, verursacht, wodurch die für das Korn zur Verfügung stehende Sauerstoffmenge reduziert wird. Während einer Kühllagerung oder einer Vorbehandlung in feucht‐kalter Athmosphäre verschwindet die Ruheperiode langsam. Bei 20°C keimen die nackten Karyopsen in Gegenwart geringer Sauerstoffmengen (3–15% 02) besser als in normal zusammengesetzter Luft, während ein erhöhter 02 Gehalt sogar schädlich wirkt. Bei 30°C hingegen, ist die Keimung auch in mit Sauerstoff angereicherter Athmosphäre (50–100%) möglich. Die physiologischcn Grundlagen von Samenruhe und Keimung werden in Beziehung mit der Anpassung dieses Unkrautes an seine Standorte diskutiert.
Chloroform‐soluble fraction from soyabean (Glycine max (L.) Merr.) leaves following herbicide applications
Authors: SOUZA I. F. , WILLIAMS J. L.
Published: July 2006

Summary: Résumé: Zusammenfassung

The research reported here had the objective of evaluating the effect of trifluralin (2,6‐dinitro‐N,N‐dipropyl‐4‐trifluoromethylaniline), bifenox (methyl‐5‐(2,4‐dichlorophenoxy)‐2‐nitrobenzoate) and vernolate (S‐propylN,N‐dipropyl‐(thiocarbamate)) on soyabean (Glycine max (L.) Merr.) leaf wax production. The applications of vernolate at 3.36 and 5.4 kg ai ha−1 reduced the chloroform‐soluble extraction of the soyabean leaves to 90% and 88%, respectively, under glasshouse conditions and to 83% and 81%, respectively, under field conditions, when compared to the untreated control taken as 100%. Trifluralin, bifenox and vernolate at 1.68 kg ai ha−1 did not reduce leaf wax production.

Effet de traitements herbicides sur la fraction soluble dans le chloroforme des feuilles de soja (Glycine max. (L.) Merr.)

Le présent travail a pour but d'évaluer l'effet de la trifluraline (2,6‐dinitro‐N,N‐dipropyl‐4‐trifluor‐omethylaniline), du bifénox (méthyl‐5‐(2,4‐dichlorophenoxy)‐2‐nitrobenzoate) et du vernolate (S‐propyl‐N‐N‐dipropyl thiocarbamate) sur la production des cires foliaires chez le soja (Glycine max (L.) Merr.). L'application de vernolate à 3,36 et 5,04 kg m.a. ha−1 a réduit l'extrait chloroformique foliaire à 90 et 88%, respectivement, chez des plantes cultivées en serre, et à 83% et 81%, respectivement, chez des plantes cultivées au champ, par rapport aux 100% trouvées chez les téemoins non traités. La trifluraline, le bifénox et le vernolate à la dose de 1,68 kg/ha n'ont pas réduit la production de cires foliaires.

Ueber die chloroformlösliche Fraktion von Sojabohnenblättern nach Herbizidapplikationen

In den hier publizierten Versuchen wurde der Einfluss von Trifluralin (2,6‐dinitro‐N,N‐dipropyl‐4‐trifluoromethylaniline), Bifenox (Methyl‐5‐(2,4‐dichlorphenoxy)‐2‐nitrobenzoate) und Vernolat (S‐propyl N,N‐thiocarbamate) auf die Ausbildung der Wachsschicht auf den Blättern von Soyabohnen (Glycine max (L.) Merr.) untersucht. Die Anwendung von 3,36 und 5,04 kg ai ha−1 Vernolat verminderte die durch Chloroform extrahierbaren Anteile von Soyablättern im Gewächshaus auf 90 resp. 88%, in Freilandversuchen auf 83 resp. 81%, im Vergleich zu den mit 100% eingesetzten Extrakten aus unbehandelten Pflanzen. Trifluralin, Bifenox und 1, 68 kg ai ha−1 Vernolat verursachten keine Verringerung der Wachsproduktion der Blätter.
The demography of Datura ferox (L.) in soybean crops
Authors: BALLARÉ C. L. , SCOPEL ANA L. , GHERSA C. M. , SÁNCHEZ R. A.
Published: July 2006

The emergence, survival, seed production and seed dispersal of Datura ferox was studied in soybean fields in 1982–1983 and 1984–1985. Most seedling emergence occurred within one month of crop sowing. Later germination, associated with inter‐row cultivation, represented 4–26% of the total seedlings, and none survived to seed production. Only 5% of the first cohort in 1982–1983, and 7% in 1984–1985, survived to seed production; it was independent of initial density. Although weed density was greatly reduced by control measures, negative relationships were observed between peak seedling density and plant height, stem diameter, number of ramifications, number of reproductive structures and seed production per plant. Only a small proportion of seeds (about 1%) were shed prior to soybean harvest. Combine harvesters collected more than 90% of capsules, but between 7% and 40% of the seeds were returned to the field. Seed viability was unaffected by passing through the machine. The patterns of seed dispersal varied depending on the design of the combine harvester. Two models shed seeds between 0 m and 21 m from their source, but another shed seeds between 0 m and 98 m. Calculations, based in life history parameters, showed that weed seed production would increase more rapidly if the seeds were dispersed during crop harvesting than if they arc not, even when the return of seeds to the soil by the combine is not large.
Evaluation of a simulation model for prediction of herbicide movement and persistence in soil
Authors: WALKER A.
Published: July 2006

The movement and persistence of residues of propyzamide, linuron, isoxaben and R‐40244 were measured in a sandy loam soil in field experiments prepared in spring and autumn. None of the herbicides moved to depths greater than 12 cm in the soil during the winter period, following application in autumn, and none moved more than 6 cm in the soil, following application in spring. The general order of persistence of total soil residues was isoxaben > linuron = R‐40244 > propyzamide. Appropriate constants to describe the moisture and temperature dependence of degradation were derived from laboratory incubation experiments and used with measurements of the strengths of adsorption of the different herbicides by the soil, in a computer model of herbicide movement. The model, in general, gave good predictions of total soil residues, but overestimated herbicide movement, particularly in winter. Measurements of herbicide desorption from the soil at intervals, during a laboratory incubation experiment, demonstrated an apparent increase in the strength of adsorption with time. When appropriate allowance was made for these changes in adsorption in the computer model, improved predictions of the vertical distribution of the herbicide residues were obtained.
Retention, absorption, translocation and distribution of sethoxydim in monocotyledonous and dicotyledonous plants*
Authors: CAMPBELL J. R. , PENNER D.
Published: July 2006

Quackgrass [Elymus repens (L.) Gould =Agropyron repens (L.) Beauv.] and barnyardgrass [Echinochloa crus‐galli (L.) Beauv.] were more than one hundred times more susceptible to sethoxydim than alfalfa (Medicago sativa L. 'Saranac') or navybean (Phaseolus vulgaris L. 'Seafarer'). Uptake of sethoxydim From soil following post‐emergence applications caused negligible reduction in E. crus‐galli fresh weight. More than 80% of foliar‐applied 14C‐sethoxydim was absorbed within 6 h in all species. Translocation occurred in all species with accumulation of 14C in rapidly growing plant tissues. Translocation to the roots was less than 8% of total in all species. Most of the extracted 14C initially partitioned into an ethyl acetate‐soluble fraction. The proportion of 14C in the ethyl acetate‐soluble fraction decreased with time with a concomitant increase of that in the insoluble fraction. Differences in the quantity of 14C in the ethyl acetate‐soluble fraction did not account for the observed selectivity.
A survey of weeds of oilseed rape in central southern England
Authors: FROUD‐WILLIAMS R. J. , CHANCELLOR R. J.
Published: July 2006

Weeds in a total of 450 fields of winter oilseed rape in nine areas of central southern England were surveyed, just prior to harvest during summer 1985, to identify those that had survived herbicide treatment or had not been sprayed and, thus, were capable of re‐infestation or contamination of the harvested crop. Sixty‐two species were identified; their levels of infestation were scored and distribution within the field noted. The most frequent species was Galium aparine, which occurred in 57% of fields. Mayweeds (Tripleurospermum inodorum, Matricaria recutita and Anthemis cotula) occurred in 23% of fields and Papaver rhoeas in 21%. All other species occurred in less than 20% of fields, the most prevalent being Sonchus asper(18%). Grassweeds were relatively infrequent, reflecting the widespread use of effective graminicides; the most prevalent was Arena spp., found in 9% of fields. Although most species were distributed throughout the field, Geranium dissection (13%) and Sisymbrium officinale (7%) were virtually confined to field margins (extending 1 m into the crop) and headlands (10m into the crop), respectively. Several species exhibited a well‐defined regional distribution; Silene alba was virtually restricted to the most southern counties surveyed, whilst Papaver rhoeas and Viola arvensis were conspicuously absent from the eastern area.
Population dynamics of Eupatorium adenophorum Spreng. and Eupatorium riparium Regel in relation to burning
Authors: TRIPATHI R. S. , YADAV A. S.
Published: July 2006

The population dynamics of Eupatorium adenophorum Spreng. and E. riparium Regel was studied in the field for 2 years, in relation to burning, by following the fate of individuals in permanent quadrats at short and regular time intervals. Both species showed increased population density and longevity of individuals on the burnt site. Adult and seedling populations of both species showed greater survival in the burnt plot. Eupatorium riparium survived better than E. adenophorum adults after burning. In the unburnt plot, however, the seedling survival of both species was nil. The heavy juvenile mortality of both species in the unburnt situation is attributed to the accumulation of a thick layer of pine needles and the growth of herbaceous vegetation. Moisture stress and low temperature in winter months also seem involved in the regulation of seedling population of these two weeds.
Germination response of Galium spurium L. to light
Authors: MALIK N. , BORN† W. H. VANDEN
Published: July 2006

The effects of intensity, duration and spectral quality of light were investigated on the germination of Galium spurium L. Light inhibited germination and the degree of this inhibition was related to the intensity and duration of exposure to light beyond the initial 36‐h imbibition period. Subsequent dry storage for up to 7 weeks and reincubation in the dark did not remove this inhibitory effect, indicating that a secondary dormancy was induced by continuous exposure to light. Germination was completely inhibited with intermittent 1‐h exposures of light every 3, 7 or 11 h for 8 days. Red, far‐red and blue light inhibited germination and the degree of inhibition was related to the duration of exposure. Far‐red light was more inhibitory than red or blue light. Green light promoted germination slightly. Nitrate salts in the medium during light exposure did not prevent the onset of light‐induced dormancy. In subsequent dark incubation, light‐induced dormancy was overcome by the addition of nitrates and, to a lesser extent, by kinetin and GA3.
Use of activated carbon to protect tomato against metribuzin
Authors: TOTH J. , MILHAM P. J. , HILLIAR G. R. , KALDOR C. J.
Published: July 2006

Protection of tomato (Lycopersicon esculentum Mill., cv. UC 134) against metribuzin was increased by placing a small quantity of activated carbon near each seed position before pre‐emergent application of the herbicide. The most protective location of the carbon was the surface of the soil, immediately above the seed. In this location, 0.10 g of activated carbon protected tomatoes from the phytotoxic effects of 0.700 kg metribuzin ha−1 whereas, without the activated carbon, 0.175 kg metribuzin ha−1 killed both tomato and blackberry nightshade (Solanum nigrum L.). Placing plastic discs in this location did not reduce the phytotoxicity; however, a barrier that prevented lateral invasion by the herbicide, of the zone of soil through which the plumule emerged, partially protected the plains from 0.350 kg metribuzin ha−1, showing that metribuzin entered the plants in substantial quantities via the plumule as well as the roots. This result suggests that activated carbon maintained a lower metribuzin concentration in the plumule/root zone than the bulk concentration. It also explains way the soil surface was the most protective carbon location. These findings provide the basis for extending the use of preemergent herbicides to situations in which previously they could not be used safely or economically.
Influence of herbicide treatments on the population dynamics of Avena stériles ssp. ludoviciana (Durieu) Nyman in winter wheat crops
Authors: FERNANDEZ‐QUINTANIllA C. , NAVARRETTE L. , TORNTER C. , ANDUJAR J. L.
Published: July 2006

A long‐term study was conducted during 4 consecutive years to determine the effects of herbicides on the major demographic parameters and on the dynamics of the populations of Avena sterith ssp. ludoviciana (Durieu) Nyman growing in winter wheat crops in Central Spain. The three herbicides tested bad different effects on the life cycle of the plant. Tri‐allate was moderately effective in reducing seedling recruitment and seedling survivorship, but it resulted in adult fecundities similar to or higher than, those of the check plots. Difenzoquat was highly effective in reducing plant survivorship and it consistently reduced the reproductive capacity of the survivors. Flamprop‐isopropyl L was not very effective in reducing plant survivorship, but it had the largest influence on adult fecundity. Overall, although the three herbicides were able to reduce substantially (59–95%) the production of new seeds, large numbers of seeds were returned annually to the soil in all the treatments. The annual application of any of the three compounds during 4 consecutive years had a marked effect on the long‐term evolution of the populations of buried seeds in the soil, emerged seedlings, mature plants and new seeds produced. Continuous herbicide application resulted in a gradual depletion of the seed bank of A. sterilis in the soil. At the end of the 4‐year period, buried seed populations in the herbicide‐treated plots were (61–81%). lower than those at the beginning of the experiment, and 92–95% lower than those of the check plots at the same lime. However, the seed reserves present in the treated plots were Mill high enough to require some type of control programme.