摘要:

The distribution of nitrogen fractions in the organs of King Edward potato plants harvested at intervals during the growing season has been determined. A general picture of the nitrogen distribution is presented and certain problems suggested by the data are discussed.Each organ of the plant shows a uniformity in its nitrogenous composition during the whole season of active growth. The seed tubers are characterized by their high content of non‐protein nitrogen. This fraction yields the greater part of the nitrogen withdrawn from the seed tubers; the amide, amino and ‘other nitrogen’ fractions all being markedly depleted. The severely depleted tubers retain some 20% of their initial nitrogen content.The roots are rich in non‐protein nitrogen, in which nitrate nitrogen is an important fraction. The roots from ammonium sulphate‐treated plots had a higher total nitrogen content than those from untreated plots, due to accumulation of ammonia nitrogen.The ‘tops’ have a higher nitrogen content and a higher proportion of protein than the roots. There is an increase in protein content and a decrease in non‐protein nitrogen in passing from stems, to petioles, to leaf laminae. The depleted tubers and roots and stems have a uniform low‐protein content of the order 0.4‐0.6 mg. protein nitrogen per g. fresh weight.Asparagine and glutamine occur in approximately equal amounts in the seed tubers and roots. Glutamine is more completely withdrawn than asparagine from the tubers, and in the ‘tops’ it constantly exceeds asparagine in amount.A study of the concentration gradients, from leaves to petioles, to stems, to stem bases and new tubers, of the fractions of the non‐protein nitrogen focuses attention upon the ‘other nitrogen’ as containing the organic nitrogen most actively involved in translocation.The concentration and total content of the glycoside solanine in the different organs has bee

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1946.tb06267.x

出版商:Blackwell Publishing Ltd    

年代:1946

数据来源: WILEY

摘要:

The symptoms and characteristics of two virus and one fungus disease and four nutritional disorders of sugar beet which cause chlorosis and necrosis of the foliage are described. The causes of the diseases and methods of distinguishing between them have been investigated by analytical, pathological and field experimental methods.Experiments in which diagnosis was confirmed by serological and spectrochemical methods show that the two often easily confused diseases, sugar‐beet yellows virus and magnesium deficiency, can be visually distinguished.Sugar‐beet yellows virus reduces the potassium, but slightly increases the magnesium content of the leaves.Magnesium deficiency symptoms are associated with a low magnesium content of the foliage, but may be induced by salt applications without greatly affecting the magnesium analysis.‘Potash’ deficiency symptoms are often, but not necessarily, associated with a low potassium analysis and may actually be caused solely by a deficiency of sodium. In the field, symptoms are induced by sulphate of ammonia and phosphate applications and may be prevented in some cases by the application of either salt or muriate of potash, in others by salt only. Some interchangeability of the functions of potassium and sodium in the plant is suggested.Manganese deficiency symptoms are associated with a low manganese content of the leaves, which can be readily increased by spraying or injection with manganese sulphate solution, but a high concentration of manganese in the foliage, such as sometimes occurs naturally on acid soils, has a toxic

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1946.tb06268.x

出版商:Blackwell Publishing Ltd    

年代:1946

数据来源: WILEY

摘要:

A wilt disease of sainfoin caused byVerticillium DahliaeKleb. is described, and it is shown that the fungus can penetrate sainfoin seedlings through unwounded roots as well as through ruptures caused by the emergence of lateral rootlets.V. Dahliaewas isolated from naturally infected soil only in June, July and August, although another species,V. nigrescens, was obtained throughout the year.Comparative studies of the longevity of cultures ofV. Dahliae, V: albo‐atrumandV. nigrescensproved that all are viable for at least 3 years on agar media. On sterilized wheat grainsV. Dahliaedies within 8 weeks after inoculation,V. albo‐atrumandV. nigrescenswithin 12 weeks, while the hyaline variants of the first two remain viable for 6 months.Evidence was obtained that in artificially inoculated soilV. Dahliaepersists mainly as microsclerotia. The fungus may also exist in the soil as hyaline mycelium or conidia, but only for a relatively short time.The incidence of this disease in sainfoin is reduced by an increase in soil‐water content, but is unaffected by the application of lime to the

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1946.tb06269.x

出版商:Blackwell Publishing Ltd    

年代:1946

数据来源: WILEY

摘要:

In August 1944, eyespot (Cercosporella herpotrichoidesFron.) was found in ninety out of 121 autumn‐sown wheat crops distributed over twelve Scottish counties. It was abundant enough in forty fields to be likely to harm subsequent crops, and was causing obvious loss in eleven crops. The disease was found in seventeen out of eighteen spring‐sown barley crops, more than half the straws being infected in seven of them. About 4 % of the wheat inspected was lodged mostly by eyespot and about 38 % of the barley mostly non‐parasitically. Eyespot increased with the frequency of wheat and barley in the two preceding years, but a few infected crops occurred on fields where no wheat or barley had been grown for many years. In Scotland, where the atmosphere is more humid, eyespot tends to increase more rapidly than in similar rotations in England; lesions are found higher up the straw and the disease is much more prevalent on spring‐sown barley. The long rotations practised in Scotland prevent more extensive damage by

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1946.tb06270.x

出版商:Blackwell Publishing Ltd    

年代:1946

数据来源: WILEY

摘要:

In the extreme south‐west of EnglandNarcissus tazettagrown for the outdoor flower crop is regularly attacked by narcissus fire (Sclerotinia polyblastis). A randomized strip experiment on the variety Soleil d'Or laid down in 1937, in which half the plots were sprayed each season, gave data on the effect of controlling this disease on the number and quality of flowers produced in 1939, 1940 and 1941, and on the weight and grade of bulbs lifted in 1941.There was an average increase of 26 % in the number of flowers produced on sprayed plots, and a 35% increase in weight of bulbs. There was no evidence of a cumulative improvement because most of the gain in one year appears to have been immediately expended in increased flowers in the following season, but the sprayed plots maintained a higher general level throughout. The quality was improved by spraying, mainly by the addition to the inflorescence of an average of one extra ‘bell’. Although not cumulative, there was a residual effect shown by the increased yield of bulbs in 1041 after a season in which only one post‐flowering spray had been applied.The effect of treatment on the date of flowering (anthesis) was negligible and its direction depended on the season. In this respect Soleil d'Or differs from Golden Spur, in which spraying induced the marked retardation of flowering noted in 1938 a

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1946.tb06271.x

出版商:Blackwell Publishing Ltd    

年代:1946

数据来源: WILEY

摘要:

In addition to giving different kinds of symptoms when infected with potato virusY, individual potato varieties also differ in their susceptibility to infection, in the concentration of virus attained in their sap, and in their efficiency as sources of virus for aphides. Their relative susceptibility in the open when exposed to equal chances of infection is correlated with the ease with which they become infected when colonized with infective aphides, and can be assessed from tests made under glass. Methods for making such tests are described; these need few tubers and give reproducible results. It is considered that they could be applied in studying the inheritance of this type of resistance and to test the behaviour of new seedlings. The American variety Katahdin was the most resistant of those tested, but there were significant differences between commercial British varieties.In the open, all varieties were equally colonized by aphides and resistance to infection with virusYwas not correlated with resistance to leaf roll.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1946.tb06272.x

出版商:Blackwell Publishing Ltd    

年代:1946

数据来源: WILEY

摘要:

Aphides (Capitophorus fragariae) were fed for periods of up to 24 hr. on strawberry plants infected with mild crinkle, severe crinkle or yellow‐edge and then transferred to plants of the wild strawberry,Fragaria vesca, or of the cultivated strawberry, variety Royal Sovereign. OnF. vescathe symptoms produced were chlorotic speckling, distortion and dwarfing of the leaves, varying in intensity', and on Royal Sovereign scattered, inconspicuous, diffuse, chlorotic spots.The symptoms from all three sources of infection were similar and were indistinguishable from those of mild crinkle of Harris&King. The virus thus selectively transmitted is tentatively concluded to be the mild crinkle virus.The virus was transmitted after feeding periods of 1 hr. or more and did not generally persist in the vector for more than 3 h

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1946.tb06273.x

出版商:Blackwell Publishing Ltd    

年代:1946

数据来源: WILEY

摘要:

Spray‐retention estimations were made during four seasons at Dartington in south Devon, on maincrop potatoes, twice‐sprayed, as in farm practice, with about 120 gal./acre for the first application and 160 gal. for the second.Evidence is given concerning the limits of reliability of the disk method of leaf sampling; and an alternative method, batten.' washing, is described.With from 2,1/2 to 3,1/2 in. of rain over test periods of 3‐4 weeks, 1% Bordeaux mixture showed about 40 % spray retention. Cuprous oxide and copper oxychloride sprays at the same copper dosage but compounded with sulphite lye or other water‐soluble dispersing agent showed less than 20% retention. Compounding of these materials with an insoluble sticker (bentonite) improved the adhesion.The percentage retention of 1/2% Bordeaux mixture was found to be less than that of the usual 1 % mixture, but adequate spray deposits could be maintained with this and other low‐copper fungicides by more frequent applications.A rapid method for determining total expanse of foliage in the field is described, and the importance of such determinations in connexion with spray‐retention trials, and practical spray timing, is stressed.Experiments were made to determine whether any copper is absorbed by potato leaves from the spray deposits. Absorption, or acid‐resistant adsorption, of the order of 0.02 mg. Cu/120 sq.cm. of leaf area

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1946.tb06274.x

出版商:Blackwell Publishing Ltd    

年代:1946

数据来源: WILEY

摘要:

The cereals root eelwormHeterodera major(O. Schmidt) is shown to be locally distributed in North Wales, the most heavily infested centres being in the arable districts of the eastern counties of the province. The most severe attacks occurred on oats where the crop had been grown too frequently; wheat and barley were apparently unaffected at the cyst populations encountered.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1946.tb06275.x

出版商:Blackwell Publishing Ltd    

年代:1946

数据来源: WILEY

摘要:

A new species of aphis,Myzus ascalonicusDoncaster, is briefly described, and compared withMyzus persicaeSulz., which it resembles superficially. It has been found on shallots in storage and on onions and other species of plants both in glasshouses and in the open between October and June. Its summer habits and hosts are unknown. In comparative virus transmission tests withM. persicaeit was found thatMyzus ascalonicustransmits dandelion yellow mosaic virus, which is not transmitted byMyzus persicae; and also cucumber virus I,Hyoscyamusvirus III and sugar‐beet yellows virus, all of which are transmitted byM. persicae. Myzus ascalonicusdoes not transmit the viruses of potatoYsevere etch, lettuce mosaic and sugar‐beet mosaic which are transmitted byMyzus persi

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1946.tb06276.x

出版商:Blackwell Publishing Ltd    

年代:1946

数据来源: WILEY