Biology of Commelina benghalensis L. in south-eastern Queensland. 1. Growth, development and seed production   总被引：2，自引：0，他引：2  

S. R. WALKER  J. P. EVENSON 《Weed Research》1985,25(4):239-244

Experiments conducted at Kingaroy in southeastern Queensland, investigated growth, development and seed production of Commelina benghalensis L. a weed of field crops, which produces aerial and underground flowers. Plants were grown from four seed types (large and small seeds from the two types of flowers) in pots exposed to the weather and in the field. Development was faster, and growth and seed production were greater in the field than in pots. Plants grown from aerial seeds were smaller, developed aerial flowers earlier, and produced more aerial fruits than plants grown from underground seeds. Rhizomes and underground flowers began to develop 6 weeks after emergence on plants from all seed types, prior to the development of aerial flowers. Seed production in the field was 8000 m^?2 for plants grown from underground seeds and 12000 m^?2 for plants grown from aerial seeds. Small aerial seeds represented 73–79% of the total seed production, large aerial seeds 19–22%, and underground seeds only 1–3%.  相似文献   

Weeds resistant to chlorsulfuron and atrazine from the north-east grain region of Australia     

S. W. ADKINS  D. WILLS  M. BOERSMA  S. R. WALKER  G. ROBINSON  R. J. MCLEOD  J. P. EINAM 《Weed Research》1997,37(5):343-349

The resistance of weeds to triazine and sulfonylurea herbicides has been recorded in several countries. The extent of the problem in the north-east grain region of Australia is uncertain. In an initial study, resistance to chlorsulfuron and atrazine in 15 weed species was investigated. The study showed that at least six of them have evolved resistance to one or other of these herbicides. Two collections of Rapistvum rugosum L., three of Sisymbrium orientale L., five of Sonchus oleraceus L., one of Fallopia convolvulus (L.) A. Love and one of Sisymbrium rhellungii O. Schultz were resistant to the recommended rate of chlorsulfuron (15 g a.i. ha^-1). Resistance to chlorsulfuron was not discovered in three collections of Sisymbrium L., two of Brassica tournefortii Gouan. three of Emex australis Steinh. and 11 of Phalaris paradoxa L. Two collections of Urochtoa panicoides Beauv. were resistant, and three collections possibly resistant, to the recommended rate of atrazine(1.8 kg a.i. ha^-1). Resistance to atrazine was not found in 12 collections of Hibiscus urionum L., nine of Salvia reflexa L., two of Parthenium hysterophorus L., two of Amaranthus viridis L. and 14 of Echinochloa colona (L) Link. The resistance status of four weeds ( R. rugosum. F. convolvulus, S. thellungii and U. panicoides was confirmed using a multiple dose-response screen and is the first report of resistance for these species. Herbicide usage records show that resistance has developed after 3-10 years of selection with chlorsulfuron and 2-15 years of selection with atrazine, with no correlation between the frequency of use and the degree of resistance for any of the species where eight or more collections were made.  相似文献   

Adsorption of isoproturon,diuron and metsulfuron-methyl in two soils at high soil:solution ratios     

WALKER  JURADO-EXPOSITO 《Weed Research》1998,38(3):229-238

Rates of degradation of isoproturon, diuron and metsulfuron-methyl were measured in two soils incubated at two temperatures (5 and 25 °C) with soil moisture at a matric potential of ?5 kPa. Rates of change in soil solution concentration were also measured after extraction of water from the soil using a centrifugation technique. The data, in general, indicated a more rapid rate of decline in aqueous-phase concentrations of herbicide than in total soil concentrations, and hence a progressive increase in partition coefficient in favour of the adsorbed phase^. In all of the incubations, however, adsorption of the herbicide was initially less than that measured using standard equilibration techniques that involved shaking with large volumes of solution relative to weights of soil. This may be explained by the ready availability of more adsorption sites in the shaken systems. With isoproturon and diuron, the changes in adsorption with time were similar at the two incubation temperatures. This indicates that the apparent changes in adsorption with these two compounds were not caused by preferential degradation in the soil solution, but by a slow equilibration with adsorption sites. The results with the weakly adsorbed compound metsulfuron-methyl, however, suggested the possibility of preferential degradation in the solution phase because, when degradation was slow, the absolute amounts adsorbed remained constant or increased slightly, even although solution concentrations declined. Implications of the results for pesticide behaviour in soils in the field are discussed.  相似文献   

Effects of incorporation and rainfall on the activity of some soil-applied herbicides     

A. WALKER  H. A. ROBERTS 《Weed Research》1975,15(4):263-269

Eight herbicides which are normally applied to the soil surface were incorporated on different occasions to a depth of 3 cm in a sandy loam. Variability in percentage weed kill was reduced when propachlor, propyzamide, aziprotryne and prometryne were incorporated, but the benefits from incorporation of simazine, lenacil and chlorpropham were small. The activity of linuron was consistently less with little reduction in variability. In further field experiments with propachlor. propyzamide, aziprotryne and prometryne, variability in weed control was reduced by incorporation but the activity of propachlor was less except when surface applications gave poor results. There was no damage to carrot, lettuce or cabbage respectively when prometryne. propyzamide and propachlor were incorporated, but cabbage was sometimes damaged following incorporation of aziprotryne. The differences in weed kill between surface and incorporated treatments were related to the delay between application and the accumulation of 5 mm rainfall, and the activity of surface applications of prometryne, aziprotryne and propyzamide could be correlated with rainfall after application. No significant correlation was found between the activity of surface-applied propachlor and rainfall. Effets de l'incorporation et des chutes de pluie sur l'activité de quelques herbicides appliqués sur le sol Huit herbicides qui sont normalement appliqués k la surface du sol ont été incorporés, a différentes occasions, à une pro-fondeur de 3 cm dans un limon sableux. La variabilité du pourcentage de mortalité des mauvaises herbes a été réduite lorsque le propachlore, le propyzamide, l'aziprolryne et la prométryne ont été incorporés. mais les effets bénéfiques de l'incorporation ont été faibles en ce qui concerne la simazine, le lénacile et le chlorprophame. L'activité du liruron a été sensiblement moindre, avec une faible réduction de la variabilité. Dans des essais au champ uliérieurs avec le propachlore, le propyzamide, l'aziprotryne et la prométryne, la variabilité de l'effet herbicide a été réduite par l'incorpora-tion, mais l'action du propachlore a été moindre sauf dans le cas oil les applications en surface ont donne de médiocres résultats. Les carottes, les laitues et les choux n'ont pas été endommagés aprés un traitement avec incorporation, respectivement avec la prométryne, le propyzamide et le propachlore, mais le chou a parfois soufTert d'une application d'aziprotryne avec incorporation. La différence de mortalité des mauvaises herbes entre les traitements en surface et les traitements incorporés a été rapportée au délai écoulé entre le traitement et l'accumulation de 5 mm de pluie, ce qui a montré que l'activité d'applications en surface de prometryne. d'aziprotryne et de propyzamide pourraient présenter une corrélation avec la hauteur de pluie tombée après Ie traite-ment. Aucune corrélation significative n'a été décelée entre l'activité du propachlore appliqué en surface et la pluviosité. Die Wirkung von Einarbeitung utid Regen auf die Aktivitat einiger Bodenherbizide Acht Herbizide. die normalerweise auf den Boden appliziert werden, wurden 3 cm tief in einen sandigen Lehmboden eingearbeilet. Wurden Propachlor, Propyzamid, Aziprotryn und Prometryn eingearbeitet, dann war ihre Wirkung gleichmassiger. Bei Simazin, Lenacil und Chtoropropham brachte die Einarbeitung jedoch weniger Vorteile. Die Aktivität von Lenacil war durch Einarbeitung stets ge-minderl und die Schwankungen in der Herbizidwirkung gingen nur geringfügig zurück. In weiteren Feidversuchen mit Propachlor. Propyzamid, Aziprotryn und Prometryn wurden die Schwankungen im Bekämpfungserfolg durch Einarbeitung reduziert, bei Propachlor ging jedoch die Aktivität zurück. ausgenommen in den Fällen, in dcnen Bodenapplikationen unbefricdigend wirkten. Wurden Prometryn. Propyzamid und Propachlor eingearbeitet. traten an Möhren, Kopfsalat und Kohl keine Schäden auf, nach Einarbeitung von Aziprotryn wurde jedoch Kohl manchmal geschädigt. Die Unterschiede in der Unkrautbekämpfung zwisehen den Bodenapplikationen und der Einarbeitung der Herbizide waren darauf zurückzuführen, dass zwisehen Applikation und Regen (5 mm) ein zu grosser zeitlichcr Abstand war. Die Wirkung der Bodenapplikationen von Promelryn, Aziprotryn und Propyzamid waren mit dem Niederschlag nach der Behandlung korreliert. Zwisehen Regen und Propachlorwirkung konnte für die Bodenapplika-tion keine gesicherte Beziehung gefunden werden.  相似文献   

Variability of bioassays with metsulfuron-methyl in soil     

J. C. STREIBIG  A. WALKER  A. M. BLAIR  G. ANDERSON-TAYLOR  D. J. EAGLE  H. FRIEDLÄNDER  E. HACKER  W. IWANZIK  P. KUDSK  C. LABHART  B. M. LUSCOMBE  G. MADAFIGLIO  P. C. NEL  W. PESTEMER  A. RAHMAN  G. RETZLAFF  J. ROLA  L. STEFANOVIC  H. J. M. STRAATHOF  E. P. THIES 《Weed Research》1995,35(4):215-224

A total of 74 independently run bioassays with soil incorporated metsulfuron-methyl from 12 different laboratories was analysed by a logistic dose-response curve to assess the precision of regression parameters and relate ED₅₀ to soil properties. The potency in terms of ED₅₀ of metsulfuron-methyl in Brassica rapa L., which was used by all laboratories, varied between 0.05 and 3.9 g a.i. ha^-1. ED₅₀ was negatively correlated with pH and positively correlated with organic matter. The majority of laboratories had ED₅₀ within the interval 0.1-1.0 g a.i. ha^-1. At one laboratory using three test species, the most sensitive species was Beta vulgaris L. followed by Brassica rapa L. and Lepidium sativum L. The coefficients of variation were smallest for the ED₅₀ and ED₉₀ response levels and largest for the ED₁₀. The slope of the response curves had considerably lower coefficients of variation than the EDs. The results are discussed in relation to a previous collaborative bioassay study. Finally it is suggested that standardization of bioassays with herbicides could be achieved in the same way as standardization of chemical analyses.  相似文献   

Adsorption and degradation of chlorsulfuron and metsulfuron-methyl in soils from different depths   总被引：5，自引：0，他引：5  

A. WALKER  E. G. COTTERILL†  SARAH J. WELCH 《Weed Research》1989,29(4):281-287

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.  相似文献   

Simulation of the persistence of eight soil-applied herhicides     

A. WALKER 《Weed Research》1978,18(5):305-313

The effects of soil temperature and soil moisture content on the rates of degradation of simazine, atrazine, propyzamide, linuron, metamitron, trifluralin, metribuzin und chlorthaldimethyl were measured in a sandy loam soil under controlled laboratory conditions, Atrazine degradation was the least dependent on soil moisture and metamitron degradation the most. Linuron degradation was the least affected by temperature and degradation of chlorthal-dimethyl was the most temperature-dependent. In the field, trifluralin, linuron and chlorthal-dimethyl were the most persistent herbicides with over 40% of the amounts applied remaining 5 months after application in spring, Simazine and propyzamide were intermediate with residues between 20 and 30% of the initial dose. Atrazine, metamitron and metribuzin were the least persistent with residues generally less than 20% of the amounts present initially. Weather records for the periods of the field experiments were used in conjunction with the appropriate constants derived from the laboratory data in a computer program to simulate persistence in the field. The model predicted with reasonable accuracy the relative order of persistence of the different herbicides, with the exception of metribuzin. With simazine, atrazine, propyzamide and in particular, metribuzin, there was a tendency to underestimate rates of loss. It is suggested that herbicide mobility in the soil was responsible for the poor agreement in some experiments. ASimulation de la persis tanee de huit herbicides appliqués sur le sol Les effets de la lempérature du sol et de sa teneur en eau sur les laux de dégradation ont étéétudiés pour les herbicides suivants:simazine, atrazinc, propyzamide, linuron, métamitrone, trifluraline, métribuzine et chlorthal-diméthyle. Ces taux de dégradation ont été mesurés dans un sol limono-sableux, dans des conditions contrôlés au laboratoire. La dépendance de la dégradation vis-á-vis de l'humidité du sol a été minimale pour I'atrazine et maximale pour la métamitrone. La dégradation du linuron a été Ia moins affectée par la température et celle du chlorthal-diméthyle la plus affectée. Au champ, la trifluraline, le linuron et le chlorthal-diméthyle ont été les herbicides les plus persistants, plus de 40% des quantités appliquées au printemps persistant encore 5 mois après. La simazine et le propyzamide se sont comportés de f açon intermédiaire, avec des résidus situés entre 20 et 30% de la dose initiale. L'atrazine, la métamitrone et la métribuzine ont été les moins persistants avec des résidus généralement inférieurs à 20% de la quantité initialement présente. L'enregistrement des conditions climatiques pendant la période des expériences au champ a été utilisé, avec les constantes appropriées provenant des résultats au laboratoire, dans le programme d'un ordinateur pour simuler la persistance au champ, Le modéle obtenu a permis de prévoir avec une précision raisonnable I'ordre relatif des pcrsistances des différents herbicides, à I'exception de la métribuzine. II s'est manifesté une tendance à la sous-estimation des taux de pertes pour la simazine, Tatrazine, le propyzamide et en particulier pour la métribuzine, II est suggéré que la mobilité des herbicides dans le sol a été responsable de la médiocre concordance observée dans quelques expériences. Simulation der Persistenz von acht Bodenherbiziden Es wurde die Wirkung der Bodentemperatur und der Bodenfeuchtigkeit aut die Abbaurate folgender Herbizide unter kontrollierten Laborbedingungen festgestellt: Simazin, Atrazin, Propyzamid, Linuron, Metamitron, Trifluralin, Metribuzin und Chlorthal-dimethyl. Der Abbau von Atrazin war am wenigsten, der Abbau von Metamitron am stärksten von der Bodenfeuchtigkeit abhängig. Der Abbau von Linuron wurde am geringsten durch die Temperatur beeinflusst, während der Abbau von Chlorthal-dimethyl am stärksten temperaturabhängig war. Unter Feldbedingungen wurden Trifluralin. Linuron und Chlorthal-dimethyl am langsamsten abgebaut - von der im Frühjahr ausgehrachten Menge waren nach fünf Monaten noch 40% vorhanden. Simazin und Propyzamid nahmen mit 20 und 40% eine miltlere Stellung ein. Alrazin, Metamitron und Metribuzin waren am wenigsten persistent: bei ihnen waren nur noch weniger als 20% des Anfangsgehalts festzustellen. Mit Hilfe der Klimadaten für die entsprechenden Perioden der Feldversuche und den entsprechenden Konstanten aus den Laborversuchen wurde mit einem Computerprogramm die Herbizidpersistent für Feldbedingungen simuliert. Mit dem Modell konnte die relative Rangfolge der Herbizidpersistenz mit hinreichender Genauigkeit vorhergesagt werden; Metribuzin machte jedoch eine Ausnahme. Für Simazin, Atrazin, Propyzamid und besonders für Metribuzin wurden die Abbsuraten etwas unterschätzt. Es wird angenommen, dass die mangelnde Übereinstimmung bei einigcn Versuchen auf den Transport der Herbizide im Boden zurückzuführen ist.  相似文献   

FOCAL SKELETAL MUSCLE UPTAKE OF 99mTECHNETIUM‐HYDROXYMETHYLENE Diphosphonate FOLLOWING PERONEAL NERVE BLOCKS IN HORSES     

JOHN F. GRIFFIN IV  BENJAMIN D. YOUNG  GEOFFREY T. FOSGATE  MICHAEL A. WALKER  JEFFREY P. WATKINS 《Veterinary radiology & ultrasound》2010,51(3):338-343

We have observed focal skeletal muscle uptake of ^99mTechnetium‐hydroxymethylene diphosphonate (Tc‐HDP), which could mimic a tibial lesion, in horses following peroneal nerve blocks. To characterize this observation further, 45 bone phase scintigrams were performed in 12 horses undergoing peroneal nerve blocks. Scans were performed before, and 1, 3, 7, and 14 days postblock. The superficial and deep branches of the peroneal nerve were blocked by injecting 10 ml of 2% mepivacaine in one limb and 20 ml in the other. Images were evaluated for uptake at the block site and uptake likely to mimic a tibial lesion. Regions of interest were placed over the block site and distal tibia. Count density ratios were used to estimate change in uptake intensity over time. The overall proportion affected was 0.52 (95% confidence interval [CI], 0.36–0.68; P<0.001) 1 day postblock and 0.24 (95% CI, 0.13–0.40; P=0.005) 3 days postblock. The overall proportion likely to mimic a tibial lesion was 0.19 (95% CI, 0.09–0.33; P<0.001) 1 day postblock and 0.21 (95% CI, 0.09–0.40; P=0.005) 3 days postblock. Focal skeletal muscle uptake was seen in only one horse 7 days postblock. Increased uptake intensity was associated with higher local anesthetic dose (P=0.042). Peroneal nerve blocks cause focal skeletal muscle uptake of ^99mTc‐HDP on bone phase scintigraphy. This occurs in approximately 50% of blocked limbs and can mimic a tibial lesion on the lateral view in approximately 20% of blocked limbs.  相似文献   

Competition of sorghum cultivars and densities with Japanese millet (Echinochloa esculenta)     

HANWEN WU  STEVEN R. WALKER  VIKKI A. OSTEN  GEOFF ROBINSON 《Weed Biology and Management》2010,10(3):185-193

Field studies were conducted at two locations in southern Queensland, Australia during the 2003–2004 and 2004–2005 growing seasons to determine the differential competitiveness of sorghum (Sorghum bicolor L. Moench) cultivars and crop densities against weeds and the sorghum yield loss due to weeds. Weed competition was investigated by growing sorghum in the presence or absence of a model grass weed, Japanese millet (Echinochloa esculenta). The correlation analyses showed that the early growth traits (height, shoot biomass, and daily growth rate of the shoot biomass) of sorghum adversely affected the height, biomass, and seed production of millet, as measured at maturity. “MR Goldrush” and “Bonus MR” were the most competitive cultivars, resulting in reduced weed biomass, weed density, and weed seed production. The density of sorghum also had a significant effect on the crop's ability to compete with millet. When compared to the density of 4.5 plants per m², sorghum that was planted at 7.5 plants per m² suppressed the density, biomass, and seed production of millet by 22%, 27% and 38%, respectively. Millet caused a significant yield loss in comparison with the weed‐free plots. The combined weed‐suppressive effects of the competitive cultivars, such as MR Goldrush, and high crop densities minimized the yield losses from the weeds. These results indicate that sorghum competition against grass weeds can be improved by choosing competitive cultivars and by using a high crop density of >7.5 plants per m². These non‐chemical options should be included in an integrated weed management program for better weed management, particularly where the control options are limited by the evolution of herbicide resistance.  相似文献   

The effect of collection and extension on tarsal flexion and fetlock extension at trot     

V. A. WALKER  J. M. WALTERS  L. GRIFFITH  R. C. MURRAY 《Equine veterinary journal》2013,45(2):245-248

A recent epidemiological study indicated that various factors may be related to injury in dressage horses, but the mechanism by which these injuries occur has yet to be determined. The suspensory ligament (SL) is a frequent site of injury, and it is assumed that greatest strain is placed on this structure in collected trot; this has yet to be proved conclusively. The study aimed to investigate the effect of collected and extended trot on the hindlimb movement pattern. Four dressage horses were fitted with markers and inertial motion sensors (IMS). High‐speed video was obtained for 2 strides on each rein in collected and extended trot on 3 different surfaces: waxed outdoor; sand/plastic granules; and waxed indoor. Maximal tarsal flexion during stance and distal metatarsal coronary band ratio (MTCR), representing fetlock extension, were determined. Inertial motion sensor data determined stride duration, speed and stride length. Data were compared between collection and extension within horses on each surface, and compared between surfaces. Collected trot had significantly lower speed and stride length but longer stride duration than extended trot on all surfaces. All horses had less tarsal flexion and fetlock extension in collected compared with extended trot (P<0.05), which is likely to increase SL loading. The study findings indicate that extended trot may increase SL strain, providing a possible explanation for the high incidence of SL injury in horses trained for extravagant movement. It is possible that substantial use of extended trot could be a risk factor for development of suspensory desmitis, which might be one contributory factor in the prevalence of suspensory desmitis in young horses repeatedly undertaking extravagant movement.  相似文献