摘要:

SummaryField experiments were carried out from 1990 through 1992 to study the effect of propaquizafop application rate and application timing of fluazifop, haloxyfop, propaquizafop, quizalofop, and hoeing onSorghum halepense(L.) Pers. control and seed cotton yield. Control ofS. halepensewith propaquizafop applied to plants 20–35 cm tall was not affected by rate of application and was similar to that obtained with fluazifop applied at the recommended rate. Cotton yield following all herbicide treatments was greater than that of the weedy control, but lower than that of the weedfree control.S. halepensecontrol with fluazifop, haloxyfop, propaquizafop, and quizalofop applied to plants 20–35 or 35–80 cm tall was greater than that obtained with their application to plants 5–15 or 10–25 cm tall. Ho‐eing, applied once at anyS. halepensegrowth stage, provided less control than any herbicide treatment on the same date. Cotton yield was increased by all herbicide treatments and hoeing compared to that of the weedy control, but the highest yield was obtained after herbicide appli‐cation toS. halepenseplants 10–25 cm tall. However, none of the herbicide treatments or hoeing increased cotton yield to the level of the w

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1995.tb02009.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryWe present a nondestructive, easy to handle, cheap, fast and efficient assay to score wheat responses to herbicides. The application of the assay is illustrated by the reactions of the bread wheat cultivars ‘Castan’ and ‘Recital’ to the urea her‐bicide, chlorotoluron. The results not only confirm the presence of a major tolerant allele controlling the differences in response between the two cultivars, but also, show the contributions of modifier genes present in ‘Castan’, ‘Recital’ and other

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1995.tb02010.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryWitloof chicory (Cichorium intybusL.) is tolerant to propyzamide and common amaranth (Amaranthus retroflexusL.) is sensitive. The absorption, translocation, and metabolism of propyzamide was studied in seedlings of witloof chicory and common amaranth to determine if differences in these processes cause the differential sensitivity. At 24,48, and 72 h after root treatment, there was no difference in the concentration of14C (g−1plant dry wt) in com‐mon amaranth and witloof chicory. Approximately 50% of the absorbed14C was translocated out of the roots to shoots of both species at 24 and 48 h after treatment. After 72 h about 55 and 74% of the absorbed14C was translocated to shoots of witloof chicory and common amaranth, respectively. Distribution of14C (g−1plant dry wt) in plant parts of witloof chicory and common amaranth seedlings was similar. Roots of both species accumulated the highest concentration of total14C, whereas shoots contained the lowest. Thin layer chromatography revealed that the herbicide was metabolized in neither species 48 h after treatment. No differences were found in absorption, translocation, or metabolism between witloof chicory and common amaranth with regard to propyz

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1995.tb02011.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryA sulfonylurea resistant biotype of common chickweed (Stellaria mediaL. Vill.) was found in a field treated with chlorsulfuron or metsulfuron for eight consecutive years. In pot experiments the biotype was resistant to postemergence treatments with the following acetolactate synthase (ALS) inhibitors: chlorsulfuron, metsulfuron, tribenuron, triasulfuron, rimsulfuron, sulfometuron, flumetsulam and imazapyr. The level of resistance to chlorsulfuron and sulfometuron was higher than to the other sulfonylurea herbicides. Whereas the level of cross resistance to the triazolopyrimidine herbicide, flumetsulam was comparable to that of metsulfuron, that of imazapyr was significantly lower. In contrast to imazapyr the biotype was not resistant to imazethapyr, an other imidazolinone herbicide. ALSin vitroassays revealed that resistance was due to an ALS enzyme that was less sensitive to ALS inhibiting herbicides. Herbicides with different modes of action were equally effective on the susceptible and resistant biotypes.

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1995.tb02012.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Summary: RésuméTwo species of the parasitic genusStriga, S. hermonthica(Del.) Benth. andS. gesnerioidesWilld., cause severe damage to graminaceous and leguminous crops, respectively, in tropical and semi tropical areas.Strigaseed germination requires the presence of germination stimulants exuded by the roots of host plants. After attachment to the host root, the young parasite exhibits a subterranean stage of development during which it already induces considerable damage in the crop. Then, the parasite emerges from the soil, develops chlorophyllous shoots and, after flowering, produces a large number of minute seeds.Many field experiments performed in the USA to control another species (S. asiatica) have shown that application of chlorthaldimethyl, di camba or dinitroanilines preventedStrigaemergence. Nevertheless the phenological stages of the parasite which are sensitive to the herbicides, as well as the mode of action of these products, are still unknown.Our experiments, performedin vitro, clearly show that chlorthal‐dimethyl, dicamba or pendimethalin inhibit germination ofS. hermonthicaandS. gesnerioidesseeds in the presence of natural germination stimulants. Moreover dicamba, clopyralid and linuron are able to induce the germination ofS. gesnerioidesseeds in the absence of stimulants (suicidal germination). Even if the mode of action of these herbicides in inhibition or induction ofStrigaseed germination has yet to be studied, such products can be useful to controlStrigabefore attachment, thus preventing the crop from suffering the early damaging effect of the parasite.Moreover bromoxynil, ioxynil, bentazone and pyridate are potent inhibitors of photosynthesis inS. hermonthica, while they do not affect the hosts (maize and sorghum). Linuron also inhibits photosynthesis in the parasite, but it may affect these crops according to the rate applied. All these inhibitors of photosystem II could be used to controlS. hermonthicaafter emergence, thus preventing seed production.Nouvelle approche expérimentale pour la recherche de méthodes de lutte chimique contre les Striga: utilisation de modelès simplifiés in vitroLes Striga sont des Scrophulariacées hémi‐parasites de racine. Deux espèces,S. hermonth‐ica(Del.) Benth. etS. gesnerioidesWilld. provoquent des pertes de rendement très importantes respectivement dans les céréales et les légumineuses, notamment dans la zone inter tropicale de l'Afrique. La germination des graines deStriganécessite la présence de stimulants de germination exsudés par les racines de l'hôte. Après fixation sur les racines de son hôte, le jeune parasite présente une phase de vie souterraine hétérotrophe au cours de laquelle il inflige déjà de sévères dommages à la culture. Après émergence le parasite développe un ap‐pareil aérien chlorophyllien fleurit et fructifie, produisant des milliers de graines minuscules.De nombreux essais, réalisés en plein champ aux USA pour lutter contre une autre espèce (S. asiatica) ont montré que l'application de chlorthal‐diméthyle, de dicamba ou de diverses dinitroanilines inhibe partiellement l'émergence du parasite. Le stade phénologique du parasite sur lequel ces produits agissent, de même que leur mode d'action sont inconnus.Nos expériences, réaliséesin vitro, montrent chlorthal‐diméthyle, le dicamba et la pendiméthaline inhibent la germination des graines deS. hermonthicaetS. gesnerioidesen présence des stimulants de germination. En outre, le dicamba, le clopyralid, et surtout le linuron, sont capables d'induire la germination des graines deS. gesnerioidesen l'absence des stimulants (germination suicide). Tous ces produits, dont le mode d'action dans l'inhibition ou l'induction de la germination reste èétudier, ouvrent des perspectives prometteuses pour la lutte préventive—la plus efficace—contre lesStriga.En outre le bromoxynil, l'ioxynil, la bentazone et le pyridate, sélectifs du Maïs et du Sorgho, sont d'excellents inhibiteurs de la photosynthèse deS. hermonthica. Le linuron inhibe également la photosynthèse du parasite, mais il est moins sélectif des céréales. Ces herbicides inhibiteurs du photosystème II pourraient être utilisés dans le cadre d'un programme de lutte pour détru

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1995.tb02013.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Summary: RésuméLa coupure de la fonction urée est seule observée au cours de 1'alcoolyse (méthanol ou éthanol) et de l'hydrolyse (pH8) du chlorimuron éthyle à 30°C ou 50°C. La pyrimidinamine est quantitativement formée dans tous les cas accompagnée des carbamates correspondants (alcoolyse) ou du phénylsulfonamide (hydrolyse) quise cyclise facilement en saccharine (pH6). L'hydrolyse du substituant carbéthoxy porté par le noyau aromatique de l'herbicide devient prépondérante en solution alcaline. Les constantes de vitesse du premier ordre cinétique ont été précisées. La déméthylation du chlorimuron éthyle n'a pas été détectée.Alcoholysis and chemical hydrolysis of chlorimuron ethylAlcoholysis (methanol or ethanol) and hydrolysis (pH8) of the herbicide chlorimuron ethyl at 30°C or 50°C involved only the breakdown of the urea function. The pyrimidinamine is always obtained in high yield along with the corresponding carbamate (alcoholysis) or phenylsulfonamide (hydrolysis). This compound was easily cyclized to saccharin (pH6). In alkaline solution, the carbethoxy substituent of the aromatic ring was preferentially hydrolysed. The first order kinetic constants were characterized. No formation of desm

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1995.tb02014.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryThe allelopathic effect ofAmaranthus retroflexusL.,Amaranthus blitoidesS. Wats, andAmaranthus gracilisDesf. on wheatTriticum durumL. was investigated under laboratory, glasshouse and field conditions. Laboratory experiments showed that fresh shoot or root extract of the three weed species reduced germination, coleoptile length, root length and root dry weight of wheat seedlings. The inhibitory effects were rate dependent, with low concentrations of shoot extract promoting shoot growth of wheat. Fresh plant extracts were more phytotoxic than dried plant extracts and shoot extracts had higher detrimental effects than root extracts. In pot experiments, dried shoot extract ofA. gracilisincreased shoot and root dry weights of wheat seedlings. ForA retroflexusandA. blitoidesthe extracts of these and dried shoots (8 g kg−1), which had been added to soil mixtures significantly reduced ger‐mination and growth of wheat seedlings. Addition of up to 16 g kg−1ofA. gracilisresidues promoted shoot growth of wheat and had no significant harmful effect on root growth. Roots appeared more sensitive to allelopathic effect than shoots. Under field conditions, incorporation ofA. retroflexusorA. blitoidesresidues in the soil reduced height, grain and straw yield of wheat, whereasA. gracilisresidues stimulated plant height and increased

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1995.tb02015.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryField experiments were conducted in 1989 and 1990 to determine the relationship between yield loss in fibre flax and the density of volunteer barley. At volunteer densities of 50–100 plants m−2, plants which emerged 7 days before those emerging synchronously with the flax produced a significantly greater reduction in stem height (1990), stem dry weight (DW) at flowering (1989 and 1990) and seed boll DW (1990). The relationships between flax stem and boll DW and volunteer density were described at two growth stages (flowering and maturity) using a linear model. The 1990 model indicated that where volunteer tiller densities ranged from 0 to 350 m−2, interference by 90 volunteer tillers m−2(30 plants m−2) reduced stem DW by 2–9% at the flowering stage. These losses increased to 9–18% for stem DW plus 7–18% for seed boll DW when plants were grown to seed maturity. Due to the high value of flax fibres and seed it is concluded that an economic threshold based on the control of volunteer barley can be reached at low volunteer densities (30 plants m−2) especially if both fibre and oilseed wer

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1995.tb02016.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryThe dynamics of early root growth and dry matter partitioning were compared in spring wheat (Triticum aestivumL.) and wild oat (Avena fatuaL.) grown in solution culture. Total root length was greater in wheat than wild oat throughout the experiment; a result of a greater number of seminal axes and greater production of lateral root length per axis. The final number of adventitious roots was greater in wheat than in wild oat, but their length was similar. Relative growth rates were also similar as was shoot:root dry weight ratio and rate of root respiration. However, wheat used the dry matter partitioned to its roots more efficiently, producing a greater specific root length (SRL, length per unit weight). Caution must be exercised when relating these results to plants growing and compet‐ing in the field, but three general points are raised. First, the initial number of seminal axes can have a profound effect on the rate of early root development; second, the adventitious root system of wild oat is not inherently more vigorous than that of wheat; and third, future studies should compare SRL of wheat and wild oat in the field. If differences similar to those in the present study are found they may contribute to the greater competitive ability of whea

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1995.tb02017.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1995.tb02008.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY