摘要:

Ascospores were found to be the principal cause of primary infection in the disease of oats caused byLeptosphaeria avenariaf. sp.avenaria. Macrospores produced in the leaf lesions on oat plants were responsible for the secondary spread of the fungus and the subsequent development of the black stem phase of the disease. Viable ascospores were present throughout the growing season and provided the means for widespread development of the disease. The purpose of the microspores is not clearly understood but they would appear to be of little importance in the initiation and subsequent spread of the disease. Seed-borne infection was found to be of no importance in the epidemiology of this disease.

ISSN:0008-4026    

DOI:10.1139/b60-009

出版商:NRC Research Press    

年代:1960

数据来源: NRC

摘要:

All isolates ofSeptoria avenaeFrank f. sp.avenaestudied were pathogenic on selected varieties of oats and there was no evidence of a differential reaction. The virulence of the isolates varied greatly and this variability was inherent in all groups of isolates. The dimensions, septations, and numbers of macrospores produced by the isolates on oat-leaf agar also varied greatly but there was no correlation between these variable characters and the disease rating of the isolates.

ISSN:0008-4026    

DOI:10.1139/b60-010

出版商:NRC Research Press    

年代:1960

数据来源: NRC

摘要:

The results of experimental applications of whole milk and whey to stripe mosaic virus inoculum or to barley plants prior to inoculation in the greenhouse established that contact transmission of stripe mosaic of barley was strongly inhibited by both milk and whey. Similarly, both skim milk and whey reduced the spread of field infection when applied as a spray. The low cost of whey suggests its possible economic utilization in the commercial control of virus diseases of plants.

ISSN:0008-4026    

DOI:10.1139/b60-011

出版商:NRC Research Press    

年代:1960

数据来源: NRC

摘要:

Chromosome numbers and voucher specimens are recorded for some collections of the tribe FESTUCEAEDumort., mainly collected in Canada. The somatic chromosome numbers of the following are recorded: (1a)Arctagrostis arundinacea(Trin.) Beal var.arundinacea, 2n = 28, 2n = 29, and 2n = 30; (1b)Arctagrostis arundinacea(Trin.) Beal var.crassispicaBowden, 2n = 56; (1c)Arctagrostis latifolia(R.Br.) Griseb., 2n = 56. (2)Beckmannia syzigachne(Steud.) Fern., 2n = 14. (3)Brachyelytrum erectum(Schreb.) Beauv., two vars., 2n = 22. (4a)Bromus ciliatusL., 2n = 14; (4b)Bromus inermisLeyss., two subspecies and two vars., 2n = 56; (4e)Bromus kalmiiA. Gray, 2n = 14; (4d)Bromus porteri(Coult.) Nash, 2n = 14; (4c)Bromus tectorumL., 2n = 14. (5)Catabrosa aquatica(L.) Beauv. var.laurentianaFern., 2n = 20. (6)Dactylis glomerataL., 2n = 28. (7)Distichlisstricta(Torr.) Rydb., 2n = 40. (8a)DupontiafisheriR.Br, subsp.fisheri, 2n = 132; (8b)Dupontia fisheriR.Br, subsp.psilosantha(Rupr.) Hultén, 2n = 44. (9)Eremopoa persica(Trin.) Roshev., 2n = 28. (10a)Festuca altaicaTrin., 2n = 28; (10b)Festuca baffinensisPolunin, 2n = 28; (10c)Festuca brachyphyllaSchultes, 2n = 42 and one collection, 2n = 44; (10d)Festuca elatiorL., 2n = 14; (10e)Festuca obtusaBieler, 2n = 42; (10f)Festuca prolifera(Piper) Fern. var.lasiolepisFern., 2n = 50; (10g)Festuca rubraL., 2n = 42; (10h)Festuca saximontanaRydb., 2n = 42; (10i)Festuca scabrellaTorr. ex Hook., two vars., 2n = 56 and 2n = 28. (11a)Glyceria borealis(Nash) Batchelder, 2n = 20; (11b)Glyceria canadensis(Michx.) Trin., 2n = 60; (11c)Glyceria grandisS. Wats., 2n = 20; (11d)Glyceria melicaria(Michx.) Hubb., 2n = 40; (11e)Glyceria pulchella(Nash) K. Schum., 2n = 20; (11f)Glyceria striata(Lam.) Hitchc, 2n = 20; (11g)Glyceria×gatineauensisBowden (G. melicaria×G. striata), 2n = 30; (11h)Glyceria×ottawensisBowden (G. canadensis×G. striata), three nothomorphs, 2n = 42, 2n = 46, and 2n = 48. (12)Lolium rigidumGaud., 2n = 14. (13a)Phippsiaalgida(Sol.) R.Br., 2n = 28; (13b)Phippsia concinna(Th. Fries) Lindeb., 2n = 28. (14)Pleuropogon sabineiR.Br., 2n = 42. (15)Schizachnepurpurascens(Torr.) Swallen, 2n = 20. (16)Torreyochloa fernaldii(Hitchc.) Church, 2n = 14.

ISSN:0008-4026    

DOI:10.1139/b60-012

出版商:NRC Research Press    

年代:1960

数据来源: NRC

摘要:

A number of barley and wheat varieties from different geographical areas were tested for cold hardiness in the sprouted seed stage. The young plants were subjected to a hardening process for varying periods and at different temperatures. Under appropriate conditions of hardening and freezing nearly all of the varieties of winter wheat and winter barley showed a similar hardening pattern, that is, a relatively high degree of hardiness and ability to harden in young stages of germination (up to 1 week of growth at 1.5 °C), a minimum hardiness at 2 or 3 weeks of hardening at 1.5 °C, and a second maximum of hardiness at about 6 weeks of hardening at 1.5 °C. Spring varieties and some West European winter wheats with low winter hardiness did not show the second maximum of hardiness after 6 weeks at 1.5 °C. In general, additional hardening for 1 week at −4 °C produced a striking increase in hardiness. For barley this increase was produced at all stages of development whereas for wheat there was a large increase only after 1 to 5 weeks of prehardening at 1.5 °C. Hardening at −4° C for longer than 1 week did not produce additional hardiness. Possibilities of testing for cold hardiness at different growth stages of sprouted seeds under various conditions of hardening are discussed.

ISSN:0008-4026    

DOI:10.1139/b60-013

出版商:NRC Research Press    

年代:1960

数据来源: NRC

摘要:

Needle blight of eastern white pine (Pinus strobusL.) is characterized by an orange-red discoloration of the distal portions of current year needles. At Chalk River, Ontario, 600 seedlings and saplings of white pine were examined repeatedly throughout the 1957 and 1958 growing seasons for the appearance and development of needle blight symptoms. The first of these were faint pinkish spots on the stomata-bearing faces of needles in semimature (about four-week-old) tissue. These developed rapidly into orange-red bands which within a few days spread to the needle tips. Mature tissue was not susceptible to attack, so lesions which developed subsequently were always proximal, on younger tissues derived from basal meristems. Attacks which occurred in the early summer killed only limited areas at the tips of needles, whereas those that occurred when the needles were nearly full-grown involved most of their length. Needle blight incidence was confined to a few major outbreaks during one season and in each of these many trees developed typical symptoms at essentially the same time. Each of these major outbreaks of the disease occurred after 1 or more days of wet weather which was followed suddenly by a continuous sunny period. No microorganisms were isolated from tissues displaying the initial needle blight symptoms.The data with respect to the nature and occurrence of needle blight are believed to suggest that susceptibility to the unfavorable conditions which incite it is inherent in the individual and that differences in response among members of a local population depend on variations in susceptibility, rather than on a varying local predisposition among uniformly susceptible individuals. The blight is initiated in semimature leaf tissues only but then spreads distally throughout adjacent, more mature tissues with a similar pattern of breakdown.

ISSN:0008-4026    

DOI:10.1139/b60-014

出版商:NRC Research Press    

年代:1960

数据来源: NRC

摘要:

Fungitoxicity, in terms of inhibition of mycelial growth, was demonstrated with eight chlorinated hydrocarbon insecticides by the culture plate bio-assay method. All of the dosage–response curves thus derived were bimodal rather than linear. Evidence is presented to show that the shape of these curves is governed by two physical properties of the compounds: water solubility (which was determined experimentally) and vapor pressure. The concentration of insecticide in solution governs the initial rise of each dosage–response curve which is extended to a peak because of supersaturation and is followed by a decline as normal saturation is regained. The concentration of toxicant vapor in contact with the organism governs the second rise in the curve to a level dependent on the vapor pressure of the compound. Lindane has a high degree of fungitoxicity because of its relatively high water solubility. Heptachlor, chlordane, and aldrin are also highly toxic because of their vapor pressures. DDT, methoxychlor, dieldrin, and endrin are weakly fungitoxic because of both low water solubility and low vapor pressure.

ISSN:0008-4026    

DOI:10.1139/b60-015

出版商:NRC Research Press    

年代:1960

数据来源: NRC

摘要:

The relationship between ring width and length of wood cells was studied by reference to mature white cedar trees of various growth patterns. These included trees of similar diameter but diverse growth rates, trees with transition from wide to narrow rings or from narrow to wide rings in their peripheral growth, and trees with rings varying in width in different radii. Although much fluctuation occurred among individuals there was in general an inverse relationship between cell length and ring width. On the other hand, the variations in frequency of pseudotransverse divisions in the cambium, which might be expected to have a profound influence on cell length because of their involvement in cambial cell multiplication, were not obviously related to the growth rate. The frequency of pseudotransverse divisions in the fusiform initials apparently is geared neither to circumferential expansion nor to number of periclinal divisions in the cambium but rather seems to be related simply to linear radial increment.

ISSN:0008-4026    

DOI:10.1139/b60-016

出版商:NRC Research Press    

年代:1960

数据来源: NRC

摘要:

Based on the findings of one season of field work, an account is given of the vegetation and flora (vascular plants) of the immediate vicinity of Caribou Lake in northeast Manitoba. The plant communities are grouped according to physiographic position. Their chorology is presented in the form of a map which was compiled from interpretation of vertical aerial photographs of the area. The appearance of the various vegetation types on the aerial photographs is described.The prevalent vegetation of mesic sites is a tundra community dominated by ericoid shrubs. There is strong evidence that much of this treeless vegetation occupies sites where trees once grew; they have been removed by fires. Recent alluvium bears stands ofPicea glauca(white spruce) which shows good growth. Shallow wet peats are covered by black spruce stands with shrubs and mosses, chieflySphagnum. Deeper peats, usually with shallow active layers, bear heath or sedge–cottongrass tundra.

ISSN:0008-4026    

DOI:10.1139/b60-017

出版商:NRC Research Press    

年代:1960

数据来源: NRC

摘要:

Extension growth of the chlorophyll-containing roots ofHydrocharis morsusranaewas inhibited by 0.5 p.p.m. of 3-(4-chlorophenyl)-1,1-dimethylurea (monuron) whereas concentrations close to the water saturation point of 230 p.p.m. were required to inhibit extension growth of the non-chlorophyll-containing attached roots ofZea maysandPhleum pratenseand the detached roots ofPisum sativum.A total of 15–20 μg of monuron per gram fresh leaf applied through the cut petiole of detached primary leaves ofPhaseolus vulgarisinhibited the increase of dry matter by 90% and suppressed transpiration 40–50%. Internal concentrations of 1–2 μg/g of monuron produced simultaneous enhancement of dry matter increase and of transpiration but concentrations of 5–10 μg/g produced a suppression of dry matter increase concurrently with an enhancement of transpiration. Age of leaf and the time of year in which the plants were grown altered the critical internal concentration levels required to affect dry matter increase and transpiration.Analysis of detached leaves treated with 15–20 μg/g monuron indicated a marked suppression of the formation of non-water-soluble carbohydrate, a slight suppression of the formation of water-soluble nitrogen, but little or no effect on water-soluble carbohydrate or on non-water-soluble nitrogen.In detached leaveso-phenanthroline, 3-phenyl-1,1-dimethylurea, and 3-(3,4-dichlorophenyl)-1,1-dimethylurea resembled monuron closely in symptom development and in their effect on dry matter production and transpiration. Iodoacetamide, 2,4-dinitrophenol, and 8-hydroxyquinoline each produced some effects similar to monuron but differed from it in certain respects; Thiourea, sodium diethyldithiocarbamate, sodium fluoracetate, ethyl-NN-diphenylcarbamate, and hydroxylamine hydrochloride were without noticeable effect.

ISSN:0008-4026    

DOI:10.1139/b60-018

出版商:NRC Research Press    

年代:1960

数据来源: NRC