摘要:

SUMMARYUsing a point‐quadrat, measurements were made of the frequency of the weeds in the stubbles of winter wheat grown after various 3 1/2‐year leys and after two four‐course arable rotations barley, fodder‐beet and barley undersown with a 1‐year ley. The most frequent broad‐leaved weeds wereMatricaria maritimavar.inodora, Stellaria mediaandPolygonum aviculare.The total frequency of broad‐leaved weeds was 10% after the arable rotations and 18% after the 3 1/2‐year leys. The corresponding figures forPoa annuawere 16 and 25%. These differences probably occurred because the weeds were abundant and set seed during the years of establishment of the 3 1/2year leys.Some grasses and clovers sown in the leys were common weeds of the wheat.Lolium multiflorum, Trifolium pratenseandT. repensshowed frequencies of 14–30% after leys in which they had seeded.Lolium perennere‐established vegetatively; its average frequency was 15% after ryegrass leys.Dactylis glomeratawas more easily killed by ploughing.Defoliation and nitrogen manuring treatments of the leys affected the control ofS. media, P. aviculare, T. repens, L. perenne, P. annuaandAgropyron repens.The frequency ofA. repenswas 15% after the arable rotation, whereas after 34‐year leys it was 15% after hayed leys and only 4% after cut leys not receiving nitrogen and a

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1963.tb03740.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

SUMMARYKale and swedes were grown together either in alternate drill rows, or as alternate singled plants within the row. In 2 years' experiments neither of these spatial arrangements gave an increase in total dry‐matter yield over that of either kale or swedes in pure stand. The yield of both kale and swedes when grown together was generally adversely affected by the presence of the other species. It is tentatively concluded that there was competition for light, for nitrogen and possibly for wate

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1963.tb03741.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

SUMMARYThe errors involved in determining leaf area of intact potato plants by rating, i.e. by visual comparison with pictorial standards, are considered.The true area was consistently underestimated but, while the error in estimating areas of single leaves may be large, it is only about 7% for the total area of a large sample of leaves.It is shown that errors may arise from peculiarities in the standard pictures.The standards increased in size logarithmically but further work is necessary to see if this is the best arrangement.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1963.tb03742.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

SUMMARYCarnation plants were grown from shoot apices ranging from 200 μ to 1 mm. in length, derived from plants of different ages, at all times of the year. Tips grew best in small tubes on a simple nutrient medium, supported on wicks of ashless filter paper. The presence of rooting hormone in the medium was essential during the early stages of culture. Rooting was affected by the size of the tips and the time of year at which they were excised. Rooting of tips after heat treatment of the parent plants differed with variety, and virus infection also affected the rooting of some varieties

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1963.tb03743.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

SUMMARYAlthough stem‐pitting inCoffea arabicaresembles conditions caused by virus infection in some other trees, experiments suggest that in coffee it is not caused by a virus but may be induced by factors that favour rapid growt

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1963.tb03744.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

SUMMARYTwo brief field trials in Western Nigeria compared the effects of infection by a virulent strain of swollen‐shoot virus on growth of West African Amelonado cacao with those on other types. These included hybrid progenies from crosses with Upper Amazon cacao. Within each progeny, severity of leaf symptoms was correlated with growth rate, but the Amelonado showed more severe symptoms than the Amazon progenies, although infection decreased its growth rate proportionally less. However, most of the Amazon progenies are so much more vigorous that some infected ones grew more rapidly than the uninfected Amelonado. Three progenies were exceptionally tolerant and their growth rate was little affected by infection: such types may prove valuable in areas where attempts to eradicate swollen‐shoot disease have been abando

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1963.tb03745.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

SUMMARY10% Teepol, 2% citric acid, 1% tannic acid, 3% NaH2PO4, 3% Na2HPO4, 0·1%, 0·5%, 1 and 3% Na3PO4and Diversol (a chlorinated Na,PB, plus bromine) solutions were mixed with tomato sap infected with tomato mosaic virus (TMV) and inoculated toNicotiana glutinosa, after standing for different lengths of time. Fewest lesions were caused by mixtures with tri‐sodium orthophosphate or Diversol at concentrations over 1%.It was found difficult to free sap‐cngrained hands from TMV: the best treatment was to wash in a 3% solution of tri‐sodium orthophosphate and then to scrub well with soap and water, but this did not always free under the nails from virus.The best way to prevent contamination from TMV‐infected tools, other than heat sterilization, was to dip them in 3% tri‐sodium orthophosphate solution and not to rin

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1963.tb03746.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

SUMMARYTomato plants were easily infected with tomato mosaic virus (TMV) by contact with infective clothing. TMV persisted for over 3 years on clothing stored in a dark enclosed space, but was inactivated within a few weeks in daylight. Dry‐cleaning, or washing clothing with detergents in hot water, decreased its content of TMV to a low level. A survey of clothes worn by workers on tomato‐growing nurseries showed that men's outer clothing is seldom cleaned and is often worn from one season to the next.Tests of TMV persistence on painted, heated, wooden glasshouses and on cool structures, and on glass and metalwork in them, were done by wiping tomato leaf sap or brushing tomato leaves over them, and then trying to recover TMV by wiping the structures with damp cotton swabs. Virus was rapidly inactivated in daylight, often being undetectable after a month, but sometimes persisting at low concentrations for over 2 months. A survey of commercial glasshouse structures showed that TMV seldom overwintered on them but sometimes TMV persisted in dry tomato leaf debris. Such debris should be removed from structures by wash

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1963.tb03747.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

SUMMARYField experiments on three soil types in southern Britain showed that applying dichloropropane‐dichloropropene (D‐D) or methyl bromide at 2 lb./100 sq.ft. in summer killed over 99% ofX. diver sicaudatumin soil and almost stopped the infection of strawberry crops with arabis mosaic virus (AMV). Both chemicals killedX. diversicaudatumdown to 28 in., the greatest depth sampled. D‐D at 1 lb./100 sq.ft. gave variable results when applied in summer but was more effective when left in the soil through the winter. At the doses used, dazomet, methyl isothiocyanate, metham‐sodium, dibromochloropropane and tetramethyl thiuram disulphide killed too fewX. diversicaudatumto control the spread of AMV.Incidence of AMV in crops planted on treated land was closely related to the number of survivingX. diversicaudatum.Larvae and adults seemed equally susceptible to the chemicals. In some experiments, other species of plant‐parasitic nematodes were sometimes less affected by D‐D thanX. diversicaudatum.In untreated soil planted with strawberries, numbers ofX. diversicaudatumtripled in 2 years, most of the increase coming in the second year. In D‐D treated soil, the few survivors appeared to increase even more slowly than this. A nematicidal treatment that brings theX. diversicaudatumpopulation to fewer than one nematode per 2 1. of soil should not need repeating for

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1963.tb03748.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

SUMMARYThe aerial parts of tomato varieties showing low and high (monogenic) resistance toFusariumwilt were inoculated, either directly into stems or through the roots of low resistance Bonny Best rootstocks on to which they had been grafted. Symptom development was recorded and the distribution of the fungus within the plants was determined by isolation.From stem inoculations the fungus invaded Bonny Best stems and leaves (although much less readily than from root inoculations) and caused mild symptoms. Little or no invasion of Jefferson (high resistance) stems occurred and there were no symptoms. It was concluded that the stems of the two varieties differed in resistance to invasion.When invaded from infected Bonny Best rootstocks, scions of five varieties of low resistance showed normal wilt development with considerable leaf flaccidity. Vascular browning in the leaves was often associated with the presence of the fungus. Scions of six monogenic high‐resistance varieties invaded from Bonny Best rootstocks showed symptoms more quickly and of a different type (severe yellowing and necrosis with less leaf flaccidity). Vascular browning was extensive in the leaves but was produced far in advance of fungal invasion, which was normally restricted to the lower part of the stem. It appeared that the scions were highly sensitive to toxins produced in the lower part of the plant. These differences were apparent when scions of the two types were invaded from a common rootstock.The results confirm the observations of other workers that the stems as well as the roots of monogenic resistant varieties of tomato show greater resistance to invasion byFusariumthan corresponding organs of tomato varieties of low resistance. They also provide an explanation for the apparently conflicting results of previous grafting experiment

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1963.tb03749.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY