摘要:

Exposure of tobacco plants to phytotoxic solutions obtained from decomposing rye and timothy residues increased their susceptibility to black root rot caused byThielaviopsis basicola(Berk. & Br.) Ferraris. In greenhouse experiments 16 tobacco varieties, ranging from susceptible to highly resistant to black root rot in the field, were exposed to rye and timothy toxins and their relative resistance and severity of disease development were determined. Exposure to the toxins resulted in an apparent breakdown of resistance. There were no significant differences among the varieties and the disease was equally severe on roots of the resistant and the susceptible varieties after the toxin treatment. These results might explain in part, at least, the apparent breakdown of resistance that has at times been noted in the field with black root rot resistant varieties. The effect of the toxic compounds appears to be largely on the host rather than on the fungus. The precise biochemical and physiological changes which are induced in the root tissues by the toxins to make them more favorable for fungus invasion and colonization are at present not known. This study suggests, however, that phytotoxins may be important host-conditioning factors in the development of root diseases.

ISSN:0008-4026    

DOI:10.1139/b63-062

出版商:NRC Research Press    

年代:1963

数据来源: NRC

摘要:

Studies in the Maritime Provinces and Quebec showed thatStereum sanguinolentumbehaves as a primary invader of the heartwood of living balsam fir, becoming established in the trees only as a result of injuries to living stems and branches. These observations were largely confirmed by artificial inoculations. Other factors apparently influencing infection were the age of the wound, size of wounded part, and time of injury. The rate of decay was found to increase with increasing size of injury but was not influenced by the origin of the infection or the location of stands. Implications of the findings and the factors requiring additional study are discussed.

ISSN:0008-4026    

DOI:10.1139/b63-063

出版商:NRC Research Press    

年代:1963

数据来源: NRC

摘要:

Suspensions of wheat striate mosaic virus prepared with the sediments from high-speed centrifugation (105,000 g) of liquid extracts from viruliferous leafhoppers (Endria inimicaSay), infected 63%, 46%, 33%, 5.5%, 3.5%, and 1.6% of the leafhoppers into which they were injected after dilution to 10−0.7, 10−1, 10−2, 10−3, 10−4, and 10−5respectively. Suspensions of the virus were still infective after they were heated for 10 minutes at 45 °C, but not at 55 °C. Suspensions stored at 4 °C were highly infective after 3 days, but were toxic to the injected insects by the fourth day. Most infectivity was lost after 3 days at −10 °C. Wheat plants did not become infected when mechanically inoculated with suspensions which were infectious to leafhoppers. A specific particle was not correlated with infectivity when suspensions from viruliferous and healthy insects were compared in the electron microscope.

ISSN:0008-4026    

DOI:10.1139/b63-064

出版商:NRC Research Press    

年代:1963

数据来源: NRC

摘要:

The genusOedemiumLink (syn.DiplosporiumLink,DimeraFries,GongylocladiumWallr.,CladotrichumCorda) is revised. Two species are included,O. didymum(Schmidt) Hughes (syn.Botrytis didymaSchm.,Oedemium atrumLink,Cladotrichum polysporumCorda,C. scyphophorumCorda,C. uniseptatumCooke), andO. minus(Link) Hughes (syn.Helmisporium minusLink,Cladotrichum triseptatumBerk, and Br.). Both species are illustrated and described. An historical account of the relevant species and generic names is given and particular attention is paid to the misapplications of the namesOedemiumandDiplosporium.

ISSN:0008-4026    

DOI:10.1139/b63-065

出版商:NRC Research Press    

年代:1963

数据来源: NRC

摘要:

This study deals with the relationships between length of wood cells, width of annual rings, and frequency of multiplicative (pseudotransverse) divisions in fusiform cambial cells ofPicea. Species investigated wereP. engelmanni, P. glauca, P. mariana, andP. sitchensis. Observations were based on the recent growth of trees 10–20 in. in diameter, and in the case ofP. sitchensisincluded trees up to 7 ft in diameter. In general, maximum cell length was associated with a ring width of 1–2 mm. Cell length declined with increase in ring width, and also decreased slightly when ring width fell below the optimum level. The frequency of pseudotransverse divisions in the cambium remained at a more or less uniform rate in trees with rings 2–8 mm wide, but rose sharply as ring width dropped below 1 mm. The slight reduction in cell length in narrow rings was apparently associated with the rise in frequency of multiplicative divisions in the cambium. Maximum cell length was observed inP. sitchensis. The shortest cells and lowest frequency of multiplicative divisions were noted inP. engelmanni. As ring width decreased a higher proportion of the pseudotransverse divisions occurred during the late seasonal growth. The orientation of the partition in pseudotransverse division tended to be unidirectional, but reversals in direction of tilt occurred after varied intervals.

ISSN:0008-4026    

DOI:10.1139/b63-066

出版商:NRC Research Press    

年代:1963

数据来源: NRC

摘要:

Leaf disks ofNicoliana tabacumvar. Delcrest synthesize sugars from phenylpropanoid substrates. Appreciable incorporation of radioactivity into glucose, fructose, and sucrose occurs when C14-labelledL-phenylalanine,L-tyrosine, and cinnamic,p-coumaric, caffeic, and ferulic acids are supplied for 40 hours. In each case, incorporation in the light exceeds that in darkness. WhenL-phenylalanine orL-tyrosine are supplied, free glucose becomes labelled more rapidly than fructose or sucrose. Unlike the other substrates,L-tyrosine is not utilized in polyphenol metabolism. In terms of sugar production, however, comparable incorporation of activity occurs from each substrate.

ISSN:0008-4026    

DOI:10.1139/b63-067

出版商:NRC Research Press    

年代:1963

数据来源: NRC

摘要:

Continuous records of bioelectric stem potentials have been made throughout a season for three kinds of tree:Ulmus americanaL.,Pinus resinosaAit., andAcer saccharumMarsh. Daily measurements of potential and resistance for a 15-month period have also been made on a maple and some direct measurements of current are also given. A yearly rhythm was clearly visible, also daily cycles, and during the growing season cycles of 5-minute frequency. The yearly and daily rhythms have been interpreted in terms of electro-osmosis or streaming potential and seem to be correlated with the transport within the tree. The 5-minute oscillations have been related to cambial growth.

ISSN:0008-4026    

DOI:10.1139/b63-068

出版商:NRC Research Press    

年代:1963

数据来源: NRC

摘要:

Leaf length and dry weight measurements indicated that vernalization accelerated all stages of leaf development although the maximum leaf size was unaffected. Vernalization caused a great increase in meristematic activity of the root tip.

ISSN:0008-4026    

DOI:10.1139/b63-069

出版商:NRC Research Press    

年代:1963

数据来源: NRC

摘要:

A ringspot virus that occurs in raspberry was graft-transmitted to 5 strains ofFragaria vescaand to 11 commercial varieties of strawberry. Shock symptoms onF. vescawere similar to those of the strawberry viruses, mottle, and vein-banding, but were followed by mild chronic symptoms that were diagnostic. Most of the commercial varieties were killed by the virus but British Sovereign and Sparta appeared to be immune. The virus was transmitted through a large proportion of the seed from infected plants but not through the pollen.

ISSN:0008-4026    

DOI:10.1139/b63-070

出版商:NRC Research Press    

年代:1963

数据来源: NRC

摘要:

Certain soybean varieties flowered, but did not set fruit under 20-hour photoperiods. Three short (12-hour) photoperiods applied 1 or more weeks after the beginning of flowering induced fruitset which continued throughout the flowering period. One short day was not sufficient. Three short days given to vegetative plants before flowering induced earlier flowering but not fruitset. Short-day treatments applied at the first sign of flowering were also ineffective. Flowering but non-fruiting long-day plants did not produce normal anthers of viable pollen. Individual flowers set fruit if fertilized with viable pollen from plants grown continuously under short days.

ISSN:0008-4026    

DOI:10.1139/b63-071

出版商:NRC Research Press    

年代:1963

数据来源: NRC