摘要:

Summary:Batch adsorption Kocvalues of fluroxypyr‐methylheptyl ester (20000 1kg−1) and fluroxypyr (74 1kg−1) indicate increased mobility after hydrolysis of the ester to fluroxypyr. After 1 to 2 weeks incubation time in four soils, desorption Kocvalues of fluroxypyr were 100‐200 1kg−1but increased to 400‐700 1kg−1after 8 weeks. The increase in desorption Kocwas related to incubation time and not to concentration, and it was interpreted as an entrapment of the fluroxypyr within the soil organic matter. Similar increases in desorption Kocwith incubation time were noticed for pyridinol and methoxypyridine metabolites of fluroxypyr. Kocvalues also increased along the metabolic sequence fluroxypyr/pyridinol/methoxypyridine, with maximum Kocvalues of 3000‐4000 1 kg−1for the methoxypyridine metabolite. Hence mobility of the fluroxypyr aromatic ring strongly decreases with increased residence

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1990.tb01725.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Summary:Control ofAvena fatuawith tralkoxydim was significantly reduced in glasshouse experiments when the herbicide was tank‐mixed with either 2,4‐D amine or bentazone. Antagonism increased with increasing rates of these broadleaf herbicides in the tank‐mixture and it could, in turn, be decreased by increasing rates of tralkoxydim. When herbicide solutions were applied to single leaves with a micropipette applicator, bentazone was antagonistic only when mixed in the same droplet with tralkoxydim and not when the two herbicides were applied adjacently in separate droplets. In contrast, both separate and combined applications of 2,4‐D amine and tralkoxydim were antagonistic. There was no antagonism when mixtures with either 2,4‐D amine or bentazone were applied between the leaf sheath and culm. Antagonism could be circumvented by sequential applications of the herbicides. When tral‐oxydim was applied first, there was no loss ofA. fatuacontrol if bentazone application was delayed 0.5 h or if 2,4‐D amine was delayed 24 h. Results suggest that bentazone affects only cuticular penetration of tralkoxydim, whereas 2,4‐D amine also influences subsequen

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1990.tb01726.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Summary:The annual dormancy cycle was investigated in buried seeds ofPolygonum aviculareL. 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 potenti

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1990.tb01727.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Summary:We examined factors affecting conversion of light into dry matter of velvetleaf (Abutilon theophrasti) and soybean (Glycine max) grown in a replacement series near Ames, Iowa, U.S.A. in 1986 and 1987. Velvetleaf was taller than soybean over most of the growing season and had more branches, especially at the top of the canopy. Velvetleaf had greater light interception than soybean in the upper part of the canopy, particularly early and late in the day, although total light interception by canopies of the two species was similar on most sample dates. Velvetleaf had higher light utilization efficiency, or conversion of intercepted light into dry matter, in the middle and later part of the growing season. This combination of traits appears to give velvetleaf an advantage over soybean in competition for light.

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1990.tb01728.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

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

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1990.tb01729.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Résumé:Le stock semencier des mauvaises herbes a été analysé dans le sol de cinq parcelles agdcoles assolées, situées dans des zones géographiques éloignées. Une étude de la relation entre la moyenne et la variance d'échantillonnage obtenue à partir de l'analyse des prélévements isolés ou regroupés en composites a montré que cette relation existait et qu'elle était du mêeme type sur les cinq parcelles. Elle correspond à une loi de Taylor pour laquelle on a: log(variance) = a+b log(moyenne).Néanmoins, les droites de régression log (moyenne) ‐ log(variance) obtenues à partir des couples (moyenne; variance) fournis par les différentes espèces diffèrent selon les parcelles et à l'intérieur d'une même parcelle selon le nombre d'espèces retenues.Le même type d'étude réalisée à partir de simulations sur des composites variant en taille et en

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1990.tb01730.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Summary:A model system consisting of chemically isolated cuticular membranes placed on agar was used to study the penetration of various formulations of14C‐labelled clopyralid, fluroxypyr, triclopyr, picloram, and 2,4‐D into and through cuticular membranes. Clopyralid, commercially formulated as the acid, or 1‐decyl ester was rapidly absorbed after 12 h by isolated cuticles ofEuonymus fortunei. There was less absorption of the monoethanolamine and potassium salt formulations when compared to the acid and 1‐decyl ester. However, in terms of the absorbed14C‐activity that partitioned into the agar, there was no difference between the acid and salt formulations with approximately 90% being partitioned after 48 h. Conversely, the 1‐decyl ester formulation of clopyralid was retained in the cuticle; less than 5% of the absorbed fraction was recovered in the agar after 48 h. When the acid forms of clopyralid, fluroxypyr, triclopyr, picloram, and 2,4‐D were compared, there was little or no difference in absorption among the herbicides. However, the14C‐activity from clopyralid partitioned the most (90%) and triclopyr the least (50%) into the agar. When ester formulations of clopyralid, fluroxypyr, and triclopyr were compared, at least 95% of the14C‐activity was absorbed 24 h after application. However, of the amount absorbed, significantly more of the butoxyethyl ester of triclopyr (36%) partitioned into the agar than did the 1‐decyl ester of clopyralid (6%) or the 1‐methylheptyl ester of fluroxypyr (5%). Differential retention of various herbicide formulations in this model system may explain, in part, the differences in absorption and translocation among radiolabelled clopyralid formulations observed in previous research (Kl

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1990.tb01731.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Summary:Fluazifop‐butyl, haloxyfop and sethoxydim with adjuvant oil were applied for three successive growing seasons to established strawberries infested withElymus repens. The weed was virtually eradicated by three applications of haloxyfop (0.8 kg a.e. ha−1) in successive years. A similar effect was given by five applications of haloxyfop (0.4 kg a.e. ha−1) and fluazifop‐butyl (1.6 kg AI ha−1) in three growing seasons. Lower rates of haloxyfop and fluazifop‐butyl, and a high rate of sethoxydim (1.6 kg AI ha−1) applied five times were less effective, the ground cover ofE. repensshoots not being reduced by the end of the experiment although weight of living rhizome was only 10‐30% of that on untreated plots.Fruit yields on treated plots generally reflected the level ofE. repenscontrol, but there was some evidence of crop phytotoxicity from herbicide treatments. During the experimentE. repensuntreated plots increased from about 30‐100% ground cover and reduced yield 13, 28 and 68% in successive years compared wit

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1990.tb01732.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Summary:In seven field experiments in which the effect of MCPA onRanunculus acrissubsp.acrisin dairy pastures in New Zealand was studied, control varied between sites from 93% to 11% reduction in ground cover. To determine if the populations varied in resistance to MCPA, seedling progeny were sprayed with a range of doses of MCPA in a glasshouse. The LD50values ranged from 0.36 kg MCPA ha−1to 1.5 kg MCPA ha−1confirming the existence of genetic variability in resistance between the populations. Correlations between the LD50values and the control of the populations in the field, suggested that the differences in resistance contributed to the differences in control. A correlation between the LD50values and historical exposures of the populations to MCPA suggested that selection for resistance had occurred. No evidence of a difference in competitive ability between the least and the most susceptible biotypes was detected, suggesting that resistance would not decline if spraying cea

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1990.tb01733.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1990.tb01734.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY