摘要:

Summary.Sugar beet are outstandingly tolerant to 3–methoxycarbonyIaminophenyl‐A′‐(3′‐methylphenyl) carbamate phenmedipham) and the difference in susceptibility between the main weeds prevalent in beet crops and the beet themselves can be used to obtain selective weed control. The herbicide is applied post‐emergence; action via the soil can be excluded as non‐existent.A test with twenty‐nine varieties of sugar beet and one variety of fodder beet showed no interaction between phytotoxicity and variety. No variety particularly susceptible to phenmedipham was found.Investigations on the mode of action and selectivity proved that phenmedipham is a strong inhibitor of the Hill reaction. There were no differences in the extent of inhibition of the Hill reaction in chloroplasts of a sensitive plant (mustard) as compared with a resistant species (sugar beet). Measurements of photosynthesis using infra‐red absorption methods and intact plants showed that it was inhibited in both sensitive and resistant species: the degree of inhibition, however, varied according to the species. In contrast to susceptible weeds, the resistant sugar beet and Amarantus relroflexus showed recovery in assimilation, and the recovery phases were significant. It can thus be concluded that sugar beet and A. retroftexus are able to inactivate phenmedipham.Sélectivité du phenmediphame, herbicide de post‐levée dans les cultures

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1968.tb01430.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

Summary.The herbicides studied were 2,4‐D, 2,4‐DB, dicamba and orthoarsenic acid. Herbicide content in the roots was taken as an overall measure of penetration into and absorption by the leaves, and of translocation to the roots.A significantly greater 2,4‐D content resulted from foliar application at pH 3–5 than at higher values, though at pH 8–5 the inclusion of triethanolamine significantly increased the 2,4‐D content. No evidence was obtained that a greater 2,4‐D content should result from foliage applications of 2,4‐DB than from 2,4‐D. Dicamba gave a greater herbicide content than 2,4‐D when applied at high concentration at 20° C but not at 25° C, probably because of less injury at the lower temperature.Concentrations of Tween 20 up to 2% had no deleterious effect on the 2,4‐D content; on the other hand 2,4‐D content was lowered by 0–25% or more of cetyltrimethyl‐ammonium bromide. Poor wetting is not the cause of the variable herbicide contents sometimes obtained.Orthoarsenic acid, which has given better control of the weed than 2,4‐D, was very poorly translocated; its effectiveness is due to its high intrinsic toxicity.Etudes sur la teneur en herbicide des racines de Chondrilla juncea L. á la suit

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1968.tb01431.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

Summary.The resistance to simazine of a range of varieties of wheat (Triticum aestivimL.), rape (Brassica napusL.) and mustard (Sinapis albaL.) was assessed in glasshouse tests Varietal differences in survival and final weight of survivors were found in all three crops Variability m the time for which individual plants survived was greatest in the two out‐breeding crops, rape and mustard. The 1 % of mustard plants that survived 10 oz/a csimazine were allowed to produce seed in a polycross. These progenies showed a very marked increase m resistance over the unselected controls.There is thus appreciable genetic variation in resistance to simazine both within and between varieties. This is readily available for selection, and could he valuable in extending the selectivity of herbicides.Variation génétique de la resistance á la simazine chez le blé, le colza et la mo

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1968.tb01432.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

Summary.The effects of sunlight and ultraviolet light (253.7 nm) on 4‐amino‐3,5,6‐trichloropicolinic acid (picloram) in a basic aqueous solution were investigated. Electron‐capture gas chromatography determinations showed that approximately 20% of a 2 × 10−2M concentration of picloram was degraded for each 48‐hr exposure to ultraviolet light of an intensity of 200 μW/cm2. Decomposition by sunlight was slower and more variable.Precipitation of the degradation products with AgNO3indicated that two chloride ions were liberated for each molecule of picloram that was degraded. Titrations indicated that acids were formed in the degradation process, and ultraviolet spectra showed that the pyridine nucleus was destroyed. Chromatograms of the methylated decomposition products showed that at least five products were formed.The effect of the addition of a free radical scavenger, hydroquinone, on the rate of decomposition was investigated but no definite conclusions could be drawn.La dégradation photolytiq

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1968.tb01433.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

Summary.A factorial experiment with couch grass (Agropyron repens(L.) Beauv.) grown in boxes examined the effects of rhizome fragmentation, planting depth and shoot removal on the survival of rhizome pieces, new rhizome growth and rhizome carbohydrate reserves.Burial to 4 in. depth in sandy loam soil led to the death of 54% of 1 in. long rhizome pieces and 28% of 3 in. pieces. With all the segment lengths tested deeper planting decreased the proportion of buds which produced shoots.Shoot removal every 14 days decreased the dry weight and carbohydrate content of the planted rhizomes and prevented new rhizome growth. Segments 1 or 3 in. long lost their carbohydrate reserves more quickly than 9 in. pieces. Rhizomes planted at 4 in. depth contained less carbohydrate after establishment than shallow‐planted material, and produced less new rhizome growth.IS Agropyron repens (L.) Beauv.–Quelques effets de la fragmentation et de l'enfouissement du rhizome et de la defolia

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1968.tb01434.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

Summary.Dalapon–sodium at 3.3–7.5 Ib ac/a.e. was applied in early, mid– and late July 1964 to anAgrostis/Loliumpasture for selective control of the weed grassesAgrostis stolonifera, Poa trivialisandHolcus lanatus.These species were significantly more susceptible thanLolium perenneto dalapon at all doses regardless of the time of spraying. The most promising treatment was 33 lb/ac applied on 4th July, which increased the ground cover ofL. perenneand substantially reducedAgrostis stoloniferaandPoa trivialis.The total yield of herbage 12 weeks after spraying was only 50% of that from the unsprayed control, but the yield ofLolium perennewas not affected. When cut on 21st May and 5th August 1965, total yield was only slightly reduced and that ofL. perennewas increased by 60–90%. The successful practical utilization of this selectivity is likely to depend largely on the spacing of the plants ofL. perennein the pasture. Simazine at 0.75 Ib/ac applied to half of each plot 3–4 weeks alter dalapon treatment had no lasting beneficial effect on the composition of

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1968.tb01435.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

Summary.Plants of Potamogeton nodosus, a submersed aquatic, were treated with the di‐sodium salt of 7‐oxabicyclo(2,2,l)heptane‐2,3‐dicarboxylic acid‐14C (endothal‐14C). Gross radioautographs showed that the14C label moved from mature photosynthesizing leaves and accumulated in the apices and developing secondary plants. Similar results were obtained with mid‐leaf, stem (internode) and winter‐bud applications. No move‐ment of radioactivity occurred following root treatment. The results indicate symplastic translocation of endothal‐14C when applied to the leaf, stem or winter bud. It is suggested that endothal can cause the death of plants by direct injury to root tissues subsequent to absorption.Recherches sur la migration de l'endothal‐14C dans le Pot

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1968.tb01436.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

Summary.The adsorption of simazine from, and subsequent desorption into, 0–01 M calcium chloride solution was investigated using twenty‐three Rothamsted soil samples from sites differing greatly in cropping history and manurial treatment. Organic carbon content was the only factor related to the ability of the soils to sorb simazine; this accounted for 90% or more of the variation between soils Equilibrium was attained during adsorption in from fewer than 2 to more than 24 hr. Equilibrium during desorption was only occasionally attained within 24 hr. Differences between theoretically predicted and measured concentrations of simazine in solution following desorption were least for soils that attained equilibrium fastest during adsorption. Differences in adsorption and desorption kinetics between soils could not be related to soil pH, organic carbon content or cropping and manuring history. Comparisons of unlimed and limed soils suggested that no simnazine was lost by acid hydrolysis during the experiments.Adsorption et désorption de la simazine par quelques sols de Rotha

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1968.tb01437.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

Summary.Diquat and sodium monochloroacetate (SMA) were used to desiccate seed crops of red beet in experiments from 1963 to 1965. The seed plants became brown and dry about 7 days after spraying and were then judged suitable for combine harvesting, although this was not done in these experiments. Yields of seed 7 days after spraying were as good as those from the control plants, but were lower than the control yields when harvested 14 days after spraying. In laboratory tests in moist sand at 20° C the percentage of the embryos which germinated was not markedly affected by diquat or SMA treatment. The emergence of seedlings in the field, however, was affected adversely by treatment of the seed crop with 11 and 22 oz/ac of diquat ion in 1963 and by SMA at 20 lb/ac in 1964 and 1965. Diquat at 6·6 oz/ac in 120 gal/ac water in 1964 and 1965 had no serious adverse effects on embryo emergence. Residues of diquat ion in seed varied from 2 to 4 ppm, but the impairment of embryo emergence by diquat was believed to be due to the premature arrest of growth of the seed on the desiccated plants.It is concluded that when harvesting conditions are poor, desiccants could be valuable.Influence des traitements dessicants et de la date de récolte sur le rendement et la qualité de la sentence de betterave r

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1968.tb01438.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

Summary.Oat seedlings were grown by two different methods in various concentrations of bensulide. Root growth was inhibited, the roots were sometimes curved and root hairs were often present close to the root tip. Structural features of the treated roots included epidermal cells which were greatly elongated radially; short, pitied trachcary elements differentiated close to the root tip; and occasional lesions. One of the primary effects of bensulide appears to be inhibition of root growth, though it does not completely inhibit mitosis.

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1968.tb01439.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY