摘要:

Applying nitrogenous fertilizer (N) to wheat plants of different ages affected the incidence of powdery mildew,Erysiphe graminisDC, differently. When N was applied before the flag leaf had emerged, the infection‐index (number of pustules per 100 sq.cm. of leaf blade) increased to a maximum and then declined. If N was applied after the flag leaf had emerged, the infection‐index increased steadily without reaching a peak, and the increased susceptibility was not associated with an increased relative leaf growth rate as when N was applied earlier.The integral of the number of pustules per unit area with time, and the number of perithecia on the leaves of the main stem, both increased with increasing delay in the application of N. Plants given N in either April or May had at least three times as many pustules as those given N in January. The time when N was applied did not affect the date when perithecia appeared.After adding N to nitrogen‐deficient plants, the already mature leaves which had resisted mildew infection, became susceptible. This change is not associated with changes in the epidermal

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1954.tb01139.x

出版商:Blackwell Publishing Ltd    

年代:1954

数据来源: WILEY

摘要:

The effect of the presence ofErysiphe graminis triticion the reactions of each of five wheats, Malakoff, Democrat, Mediterranean, Hussar and Webster, toPuccinia triticinawas studied. Under normal environmental conditions, mildew increased the susceptibility to rust of Malakoff and Democrat, though not, except in isolated instances, that of Mediterranean or Hussar. High light intensities enhanced the effect of mildew on the reaction of Democrat toP. triticina.The susceptibility of Webster to rust was unaffected or decreased by the presence of mildew.In all varieties there was a decided tendency for rust and mildew to develop on different parts of the leaf, and when a leaf was heavily mildewed the development ofP. triticinawas sometimes almost entirely inhibited. The reason for this is obscure, since spores ofP. triticinaandE. g. triticigerminate well in each others presence, and cytological studies revealed several cases of the presence of both mildew and rust haustoria in a single living host cell. Anatomical investigations also showed that the effect of mildew on rust infection was confined to rust pustules within 1 mm. of mildew colonies.The results obtained are in accordance with Gassner's theory that susceptibility to rust is due to the presence of certain specific proteins in the host leaf.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1954.tb01140.x

出版商:Blackwell Publishing Ltd    

年代:1954

数据来源: WILEY

摘要:

Fifty‐three samples representing species of the genusArenawere tested for resistance to infection byUstilago avenaeandU. kollerifollowing artificial inoculation. Among the diploid and tetraploid species tested, eleven out of thirty‐seven samples ofArena strigosasubsp.strigosashowed complete resistance to all the cultures with which they were inoculated.Avena strigosasubsp.barbata(three samples), andAvena strigosasubsp.abyssinica(one sample), also proved to be resistant to all the available races.Variation in morphological and physiological characteristics within species and samples (varieties?) of the lower chromosome groups ofAvenawere observed and its consequences in breeding and race identification discussed.Race identification was carried out on the eightUstilagocultures and the existence of at least six races established. The tester varieties used in the present study proved inadequate for the complete separation of the smut ra

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1954.tb01141.x

出版商:Blackwell Publishing Ltd    

年代:1954

数据来源: WILEY

摘要:

Inoculation of wounded tubers at intervals throughout the storage season showed that, after harvesting, resistance to infection byF. avenaceumwas maintained for a longer period than resistance toF. caeruleum, although eventually the tubers became equally susceptible to both fungi. Tubers were less readily infected through clean‐cut than through scarified wounds. Resistance to infection was greater when an interval elapsed between wounding and inoculation than when the wound was inoculated immediately; this was related to an increase in the intrinsic ability of the cells near the wound to resist infection rather than to suberization of the wounded surface or wound periderm formation.Histological studies showed thatF. caeruleumgrew through the intercellular spaces and that the adjacent host cells remained alive, often for considerable periods, whereasF. avenaceumkilled and penetrated the cells with which it came into contact. Restriction of incipient or established lesions caused byF. caeruleumand of incipent lesions caused byF. avenaceumwas associated with suberin deposition on the host cell walls and in the intercellular spaces; in established lesions caused byF. avenaceum, restriction was attributed to an increase in the intrinsic resistance of the adjacent host cells, similar to that found near a wounded surfac

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1954.tb01142.x

出版商:Blackwell Publishing Ltd    

年代:1954

数据来源: WILEY

摘要:

Potato tubers dusted with a preparation containing 3% tetrachloronitrobenzene (TCNB) and kept in a nearly closed container in the laboratory showed reduced sprouting. The reduction was greater the lower the temperature and the earlier the application of the dust; it was less marked with tubers lying on a moist substratum. After long exposure, and especially at higher temperatures, sprouts of treated tubers tended to show a ‘witch's‐broom’ appearance. The repressive effect of TCNB on growth rate disappeared as soon as the tubers were brought into ordinary air. To a certain extent the action of TCNB was antagonized by treatment of the tubers with ethylene chlorhydrin.Replicated field experiments over three seasons, with four potato varieties, gave a measure of the check to bulking of the crop which is brought about by winter storage of seed tubers in presence of TCNB. This check was eliminated by airing the tubers before planting, the time necessary for this depending on conditions. An airing period of about 6 weeks, in an unheated greenhouse (apart from sun‐ heat) was found to be sufficient for this purpose.The speed of emergence of the variously treated batches was closely correlated with the yields produced, especially in the earlier liftings.The average number of shoots per plant was significantly increased by the dust treatment and this was reflected in a higher seed/ware ratio in the mature or late‐lifted crop.There was no evidence that the delay in sprouting brought about by TCNB was due to an effect on the respiration rate of the dormant tubers.The concentration of active principle was materially diminished in treated clamps after the period (c.5 months) of winter storage. Estimates were also made of the persistence of TCNB on exposed surfaces in still and in m

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1954.tb01143.x

出版商:Blackwell Publishing Ltd    

年代:1954

数据来源: WILEY

摘要:

When grown in an atmosphere saturated with tetrachloronitrobenzene (TCNB) vapour,Botrytis cinereashowed retarded germination and colony growth and its sporulation was completely suppressed. Retardation of growth was greater on dilute or acidified media and at lower temperatures.Similar effects were shown byBhizoctonia solani, Phytophthora parasitica, Mucor hiemalisandTrichoderma viridebut none of these was as sensitive asBotrytis cinerea, especially as regards linear growth. Of two strains ofFusarium caeruleum, one was much more sensitive than the other, both in linear growth and sporulation.Pythium deBaryanumwas unaffected in its growth rate.TCNB, as a growth repressant, is fungistatic without being fungicidal.With fungi which are sensitive, tetrachloronitrobenzene was more effective than the penta‐derivative, except forTrichoderma viridewhere the converse applie

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1954.tb01144.x

出版商:Blackwell Publishing Ltd    

年代:1954

数据来源: WILEY

摘要:

Protection experiments carried out in the greenhouse showed that preparations of thiram, zineb, ferbam and ziram were superior to cuprous oxide and copper oxy‐chloride preparations, in controlling downy mildew of lettuce and in lack of phytotoxic effect.Tests made in winter on lettuce seedlings grown in Dutch lights, showed thatBremia lactucaeattack reduced the stand of seedlings, diminished their size and weight, and, when the crop was planted out into the open ground, reduced survival in the field and slightly delayed the date of reaching maturity. The best overall results in protecting foliage against downy mildew were given by thiram and zineb preparation

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1954.tb01145.x

出版商:Blackwell Publishing Ltd    

年代:1954

数据来源: WILEY

摘要:

Virus‐free plants were produced from parents systemically infected with the following five viruses: tomato bushy stunt, carnation ring spot, cucumber mosaic, tomato aspermy andAbutilonvariegation. The leaves formed while the infected plants were kept at 36°C. were free from symptoms, and test plants inoculated from these remained uninfected. When cuttings were taken from the infected plants at the end of the treatment most grew into healthy plants. The treated plants themselves usually developed symptoms after varying lengths of time at 20°C, but some that before treatment were infected with tomato aspermy, cucumber mosaic or Abutilon variegation viruses, remained permanently healthy.The same method failed to cure plants infected with tomato spotted wilt, potato virusXand tobacco mosaic virus, although it decreased their virus content. Heat‐therapy seems not to be correlated with the thermal inactivation end point of the virusin

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1954.tb01146.x

出版商:Blackwell Publishing Ltd    

年代:1954

数据来源: WILEY

摘要:

The methods of propagation of plant material for experimental use, the procedure for preparing the radioactive solution, and its application to leaves either by dipping or spraying are described.A description is given of the conditions under which the plants were kept, the procedure adopted at sampling involving leaching of the treated leaves, subdivision of the plant and preparation of samples for determination of ‘schradan’ and ‘schradan equivalent’ by liquid counting.The methods of compiling results to determine the distribution and status of the applied schradan in or on the leaves at harvest, are o

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1954.tb01147.x

出版商:Blackwell Publishing Ltd    

年代:1954

数据来源: WILEY

摘要:

When32P‐labelled schradan was sprayed on the leaves of apple stocks and seedlings, broad and runner beans,Coleusand chrysanthemums, some was absorbed, some evaporated and the rest remained for a considerable time on the leaf surface as a residue removable by aqueous leaching. Absorbed material is defined as that present on or in the plant and not removable by aqueous leaching at the time of harvest.Evaporation losses even from glass slides were lower than theoretical expectation, from leaves they were much less.It is possible that some breakdown of the schradan occurs within the cuticular layer. Comparisons of the absorption rates of upper and lower surfaces of leaves support the theory that absorption proceeds through the cuticle in preference to vapour phase entry through the stomata.Temperature and illumination have important effects on absorption.Young leaves have been shown to be generally more absorptive than the older leaves. Comparisons have also been made of the absorption by different species. Such data must be accepted with caution as, although physical conditions were the same for all the species within an experiment, the physiological stage of development of the different plant species will not be strictly comparabl

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1954.tb01148.x

出版商:Blackwell Publishing Ltd    

年代:1954

数据来源: WILEY