摘要:

SUMMARYThe effect of gibberellic acid, CCC (2‐chloroethyltrimethylammonium chloride) and B 9 (N‐dimethylaminosuccinamic acid) was studied on growth of potato plants in pots. Growth was analysed on four occasions and changes in habit defined in terms of internode lengths, leaf areas and growth of lateral branches.Soaking seed pieces for 1 hr. in GA solution caused six internodes to elongate greatly, an effect not prevented by CCC applied when the shoot emerged from the soil. The effects on internode extension were determined by the length of the interval between GA treatment and CCC treatment.Treatment at emergence with CCC shortened all internodes and more CCC applied 4 weeks later had no effect. Late application of CCC or B9 shortened the top two lateral branches, usually very long in untreated plants.The regulators affected leaf growth differently from internode growth: usually growth regulators had less effect on leaf growth.Effects on growth depended on when the regulators were applied. Treatment with GA alone inhibited bud development at higher nodes than in untreated plants; when followed by late treatment with CCC, lateral growth at higher nodes was also less. CCC retarded development of lateral branches especially when applied early. B9 had a similar effect to CCC applied late. When regulators retarded growth of lower laterals, upper laterals often grew more than in untreated plants. Treatments did not affect the number of leaves on the main stem at first but later GA hastened senescence. GA increased the number of leaves on lateral stems, and the effect was enhanced by CCC. CCC alone increased the number of first‐ and second‐order lateral leaves. GA lengthened and CCC shortened stolons. The effect of CCC persisted throughout the life of the plant. CCC or B 9 shortened stolons whenever applied. CCC hastened tuber initiation but slowed tuber growth.CCC at first retarded formation of lateral tubers but had no effect on the ultimate numbers of lateral and terminal tubers.The value of E (net assimilation rate) did not alter with time. CCC applied at emergence increased E, probably because it hastened tuber initiation and temporarily increased sink capacity. Although tubers formed earlier with CCC, their growth was slower and their demand for carbohydrate was also less. The increase in second‐order laterals in CCC‐treated plants indicates that they utilize carbohydrate that would normally go to tubers.This experiment also demonstrates that crowding leaves by shortening stems did not diminish E, possibly because another over‐riding process (bigger sinks) offsets the effe

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1966.tb04376.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

SUMMARYThe growth‐regulating activities of four auxins were assessed in the wheat cylinder and pea segment tests, and the capacity of certain inactive analogues to act as auxin antagonists was examined. 2,4‐Dichlorophenylthioisobutyric acid was found to antagonize the auxin activity of 2,4‐dichlorophenylthioacetic acid and was more effective than the established antagonist α‐(i‐naphthylmethylsulphide)propionic acid in interaction experiments with 2,4‐D. Two auxins were studied with their respective sulphonamide analogues as antagonists and only slight reduction in growth‐regulating activity was observed. Interaction experiments with an auxin and its corresponding arsonic acid revealed no evidence of true competitive antagonism. The implications of these findings

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1966.tb04377.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

SUMMARYCut blooms of narcissus Soleil d'Or were subjected to constant temperatures ranging from 1.2° C. to 18.3° C. both in darkness and under illumination. The rate of opening of successive florets, the rate and final degree of colour development of the corona and subsequent display life were observed.Opening was negligible at 1.2° C. and 38 days were taken to open to five florets at 4.5° C. Full opening occurred in 4 days at 15.6° C.The change of colour of the corona from yellow to orange was negligible at 15.6° C, but final intensity of orange colour increased with decreasing temperatures. Temperature affected colour development both of opened and unopened florets, and after treatment at low temperature colour continued to develop when the blooms were removed to 18.3° C. The period of low‐temperature treatment giving maximum colour development was 8 days.Artificial illumination of intensity 200 ft.‐candles had little effect at 18.3° C. but it increased orange colouring at the lower temperatures.Increased orange colour whether at intermediate or low temperature was shown to be associated with a slight increase in the concentration of the total carotenoids, but more especially with greatly increased content of β‐carotene which constituted approximately 10–20% of the t

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1966.tb04378.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

SUMMARYThe distribution of diosgenin inDioscorea deltoideaWallich andD. sylvaticaEcklon at successive stages of growth is described. Diosgenin occurs in the cotyledon‐endosperm of the dormant seeds, and in the tubers, roots, stems and leaves of plants from the seedling stage onwards. It accumulates in the tubers of seedlings grown in daylight, but not in those of seedlings grown in darkness. Actively growing aerial tissues such as leader shoots appear to be the sites of formation from which the diosgenin is translocated to the tubers. The diosgenin is evenly distributed throughout the tuber

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1966.tb04379.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

SUMMARYOf the eleven cultivated species of Umbelliferae heavily attacked in the field byCavariella aegopodiiScop., chervil (Anthriscus cerefolium) attracted so many alates that it was killed before a population of alienicolae developed. Carrot was next in order of alate preference and coriander (Coriandrum sativum) and caraway (Carum carvi) were last. Despite its lack of attraction, caraway proved more lastingly suitable as a host and eventually supported the largest population of alienicolae.Of the wild umbellifers tested, wild carrot,Daucus carotassp.carota, was the species most preferred by the incoming alates and hemlock (Conium maculatum) the least. On hemlock, also, there was little colonization.Although a sequence of wild umbellifers supportedC. aegopodiithrough most of the year, few were suitable winter hosts; the apterae hibernated largely on carrot crops.In spring, cow parsley (Anthriscus sylvestris) was one of the hosts first colonized by immigrantC. aegopodiiand carried winged alienicolae before the end of June. The main development of winged alienicolae onAnthriscusand other wild Umbelliferae, however, was in July.The possible role of the wild umbelliferous hosts ofC. aegopodiiin the spread of motley dwarf virus to carrots is discussed.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1966.tb04380.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

SUMMARYIn two experiments the spread of reversion virus from a row of systemi‐cally infected black currant bushes heavily infested by the gall mite vector (Phytoptus ribisNal.) was predominantly in the direction of the winds prevailing during the dispersal period. On each side of the sources there was a curvilinear decrease of galled buds and of virus infection as distance increased.In another experiment a central source of mites and virus was surrounded by concentric hexagons comprising alternate rows of healthy and virus‐infected bushes. At leaf‐fall, galls were forty times more numerous on virus‐infected than on healthy bushes; plants in the sector downwind developed the most galls and those upwind the least. On both healthy and virus‐infected bushes in each sector, the incidence of galls decreased with increasing distance from the source. The gradients of infestation were steeper on healthy than on virus‐infected bushes, especially in sectors upwind from the source. In some sectors the infestation gradients were distorted because many of the virus‐infected bushes were so heavily infested that most of the buds became galled. The spread of virus to initially healthy plants decreased from 100 to 75% near the source, to zero at the periphery. More bushes became infected downwind from the source than upwind.In each experiment more bushes developed galls than later produced symptoms of virus infection, the incidence of which was positively correlated with the number of galls recorded the pr

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1966.tb04381.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

SUMMARYTwenty‐five white clover plants were collected along a transect in each of twenty‐six old permanent pastures in Britain and tested for sap‐transmissible viruses. Viruses were identified by the symptoms they caused, by electron microscopy and by serological tests. Of the 683 plants tested 23 % were infected. In order of decreasing incidence the viruses found were: red clover vein mosaic (in 12% of all the plants tested, and in sixteen of the fields); clover yellow vein (9 % of plants, eighteen fields); white clover mosaic (4 % of plants, eleven fields); arabis mosaic (4 % of plants, eight fields); strawberry latent ringspot (1 % of plants, two fields); and tomato black ring (0.1 % of plants, one field). The three most common viruses occurred in all parts of Britain, and were most prevalent in fields where white clover was most abundant; white clover mosaic seemed more prevalent in fields that were both cut and grazed than in those only grazed. Arabis mosaic virus was obtained only from plants in the west and north of Br

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1966.tb04382.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

SUMMARYVerticillium albo‐atrumwas apparently eradicated from soil in which dicotyledonous plants were suppressed. In one field experimentV. albo‐atrumwas not recovered after 4 years of weed‐free grass cover; in the same period soil infectivity reduced to very low levels under two bare fallow treatments. Where weeds developed after single annual cultivations soil infectivity declined from the initially high level but finally increased. In three observation trials in which hop plants were used to detectV. albo‐atrumafter grass‐cover treatments, soil infectivity was very low after 2 years and apparently nil after 3–5 years.Grass cover effectively stabilizes infested soil; it may be used for limiting spread from primary disease outbreaks, and also as a short‐term treatment to reduce the infectivity of soil to be re‐planted with resistant varieties.The frequent incidence ofV. dahliaehop infections in one trial indicated that this fungus was not amenable to control by grass cover treatment and hence may be ecologically distinct fr

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1966.tb04383.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

SUMMARYNew varieties of hop resistant to progressiveVerticilliumwilt are now widely grown and generally give acceptable disease control in commercial plantations, but on a few farms their normal high level of resistance is not maintained. The incidence of wilt on one such farm is analysed in detail. At this site wilt was not directly associated with plant death, as it is in a sensitive variety. In a discussion on etiological aspects of wilt in resistant varieties it is concluded that while seasonal fluctuations in disease incidence are influenced by climatic conditions, high mean incidence is related to undefined, intrinsic soil factors. Attention is directed to the analogous forms of disease resulting from host/pathogen interactions in which resistance and virulence are either both high or both low.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1966.tb04384.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

SUMMARYA close relationship was established between the virulence in the field of six isolates ofVerticilliumand their ability to penetrate and colonize sterile tomato seedlings grown in culture. The highly pathogenic speciesV. albo‐atrumandV. tricorpusrapidly colonized host tissue in culture, host reactions being absent or only slight.V. nigrescensandV. nubilum, mild pathogens, penetrated sterile roots more slowly and caused host reactions. The variation in pathogenicity in the field between two isolates ofV. dahliaesuggests that they are different physiological strains, but they induced no difference during the first stages of invasion‐reaction of sterile seedlings. Hyaline variants of all these isolates were less pathogenic than the original parent types.Variations in temperature from 25° C. (near optimum for the growth of both tomato plants and the fungi) caused changes in host reactions. Ability to penetrate was not affected within the pH range 4.0–8.0, but at extreme values (3.2, 9.4 and 10.0) all isolates entered without any host reaction. Variations in nitrogen supply to the pathogens induced modifications in their ability to penetrate, whereas changes in supply of nitrogen to the seedlings had no apparent effect upon host/parasite relations.The effects of simultaneous contact of non‐pathogenic and pathogenic isolates with seedling roots suggested that resistance of host tissue was controlled by the gro

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1966.tb04385.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY