摘要:

SummaryThe influence of broomrape (Orobanche crenataForsk) infection levels on commercial broad bean (Vicia fabaL.) crops was investigated and an equation relating yield losses toO. crenatadensity was derived.O. crenatagrowth was weakly and negatively related to the final height or shoot number of the broad bean plant.O. crenatadecreased seed yield mainly by reducing the number of pods. The number of seeds per pod was also decreased byO. crenatainfection when competition occurred at late‐crop growth stages when most of the pods had already developed. Bean unit seed weight was only weakly affected by infection. Correlation coefficients betweenO. crenatanumber and broad‐bean seed yield per plant were significant atP=0·05 and greater than 0·70 in most locations. On average, about fourO. crenataper broad‐bean plant decreased seed yield by half. An estimation of the percentage of losses in any field can be calculated from the equation:%loss = 100 × 0·124 × OcN.where OcN is the average final number of emergedO. crenat

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1984.tb00600.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SummaryEpicuticular wax synthesis by the primary leaf ofSorghum bicolorseedlings is inhibited when the germinating seeds are treated with 5 ppm metolachlor before germination. The composition of the free and esterified primary alcohols plus free and esterified fatty acids and aldehydes have been analysed. The predominant alcohol (75%) had 32 carbons while the 28‐ and 30‐carbon homologues accounted for 78% of the fatty acids. Treatment of the germinating seeds with metolachlor strongly inhibited formation of the C28, C30and C32alcohols. Synthesis of C30and C32fatty acids was decreased while that of the C26homologues was somewhat elevated. Simultaneous treatment of the germinating seed with metolachlor and the herbicide protectant CGA 43089 (α‐[cyanomethoximino]‐benzacetonitrile) resulted in normal wax synthesis. The results lead to the conclusion that the protectant prevents metolachlor from inhibiting synthesis of the dominating C28to C30chain‐length constituents of the sorghum epicut

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1984.tb00601.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

RésuméNous avons réalisé un inventaire phytoécologique de 122 stations sur les parcelles de betterave à sucre dans la région du Gharb (Maroc Occidental). Deux cent cinquante‐six espèces adventices ont été recensées, appartenant à quarante‐cinq familles botaniques, 80% des taxons environ étant des thérophytes, L'analyse différentielle de Czekanowski a permis de dégager quatre groupements phytosociologiques. Des groupes écologiques différentiels ont été distingués selon les caractères édapho‐climatiques (texture fine du sol, pH,

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1984.tb00602.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

RésuméSolanum elaeagnifoliumCav. infeste actuellement 100 000 ha de cultures irriguées dans le périmètre du Tadla (Maroc Central). Sa forte capacité de reproduction végétative est liée d'une part à l'intensité des facons culturales et d'autre part, à son type biologique géophyte. Par ailleurs, elle se reproduit également bien par la voie sexuée: les graines produites en grand nombre germent dès le mois de Février date à laquelle les rejets apparaissent ce qui ne fait qu'accentuer son agressivité. Au Maroc, l'espèce fleurit en Mai et fructifie dès le mois de Juillet, l'hiver correspondant au repos végétatif. En conséquence, sa nuisibilité est généralisée et elle est plus particulièrement forte dans toutes les cultures de printemps

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1984.tb00603.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SummarySodium hypochlorite (NaOCl) can release dormancy of imbibed wild oat(Avena fatuaL.) seeds. Treatments found effective included (i) immersing intact seeds in 800 mmNaOCl for 1 h followed by incubation on 5 × 10−4mgibberellin A3(GA3); (ii) immersing dehulled seeds in 800 mmNaOCl for 1 min followed by incubation on 5 × 10−4mGA3; (iii) immersion of dehulled seeds in much lower concentrations of NaOCl, e.g. 13 4 mmfor 3 h followed by incubation on water; or (iv) incubating dehulled seeds on a low concentration of NaOCl. Based on the concentrations of each of the reagents required to produce equivalent responses, NaOCl is approximately 4–6 times more effective than hydrogen peroxide (H2O2) in triggering the onset of germination, and 6 times as effective in causing growth inhibition in the roots. These results suggest the modes of action of NaOCl and H2O2in the termination of dormancy reside in a modification of the properties of the hull and seed coat membranes, and in the provision of additional oxygen to t

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1984.tb00604.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SummaryThe regenerative response of the rhizomes ofAchillea millefoliumL. to fragmentation and burial was studied in field experiments on three different soils. The percentage of buds producing shoots (estimated from surviving rhizome fragments) from 4 cm (1·6 nodes), 8 cm (3·8 nodes) and 16 cm (6·7 nodes) rhizome fragments was 63, 44 and 32 respectively averaged over all soils and depths of 5, 10 and 15 cm. The depth at which 50% of the fragments failed to produce an emerged shoot (LD50depth) was 9·3, 12·4 and 17·9 cm for 4‐, 8‐ and 16‐cm fragments respectively averaged over all soils. No fragments survived on the soil surface. The time of emergence of the first shoots was delayed and the rate of emergence and ultimate shoot population reduced with increasing depth of burial. Dry‐matter production by aerial shoots and new rhizomes decreased linearly with depth of burial of the rhizome fragments. Soil type had no effect on the regeneration of the fragments. The significance of the results for the control ofA. millefoliu

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1984.tb00605.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SummaryA 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 ofSenecio jacobaea, infestations ofS. aqua

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1984.tb00606.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SummaryThe influence of no‐tillage and conventional tillage on the outcome of early weed interference in maize (Zea maysL., cv. TZB), cowpea [Vigna unguiculata(L.) Walp, cv. VITA‐5] and their intercrop at populations of 40000, 50 000 and 30 000 + 40 000 plants ha−1was investigated on a loamy sand Oxic Ustropept in a subhumid tropical environment between April and July 1980. Both tillage treatments received 60 kg N, 30 kg P2O5and 30 kg K2O ha−1. Although the weed spectrum was wider under no‐tillage, weed weight was only 52% of the weight recorded under conventional tillage 6 weeks after sowing and the average food energy yield reductions caused were 28 and 65%, respectively. Cropping pattern had no effect on plot weediness. With minimum or no weed interference, maize performance was better in conventional than no‐tillage but worse with prolonged weed interference. Cowpea responded more to weed interference than to tillage practice. Regardless of tillage practice and weed interference duration (up to 6 weeks) after sowing, maize monoculture produced the highest food energy yield, followed by maize/cowpea intercrop and cowpea monoculture in

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1984.tb00607.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1984.tb00608.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1984.tb00609.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY