摘要:

A comparison is made of the changes in the lengths of the vegetative and frost-free seasons in the Prairie Provinces and the Northwest Territories, based on a mean daily temperature of 42° F. for growth and a minimum temperature of 32° F. for frost damage. Figures are included that show the broad details of the beginning and of the ending for both seasons. From these figures the lengths of the seasons may be deduced for various districts. A comparison is made of the average daily temperatures for the vegetative seasons at a number of representative places. The variability in the beginning and the ending of the frost-free season for a number of places is indicated by a table giving extreme, 25-percentile, 50-percentile, and 75-percentile dates. These values are shown graphically by a unique type of diagram that also shows the median length of the frost-free season.

ISSN:1923-4287    

DOI:10.1139/cjr48c-001

出版商:NRC Research Press    

年代:1948

数据来源: NRC

摘要:

An investigation of the salt requirements for pyocyanin production byPseudomonas aeruginosahas been carried out, and the mineral balance for maximum pyocyanin production determined. By employing a medium containing the required salt balance, it has been possible to obtain a fourfold increase in pyocyanin production over that obtained on other media usually employed for that purpose.The ions, Mg, SO4, K, PO4, and Fe have been found essential to the formation of the pigment. Optimum production of pyocyanin was obtained by the use of 0.04% dipotassium hydrogen phosphate, 2.0% magnesium sulphate septahydrate, and 0.001% ferrous sulphate septahydrate in a medium containing glycerol, glycine, and leucine. In the presence of minimum amounts of Mg and SO4, maximum pyocyanin production can be obtained by the addition of increased amounts of either Mg or SO4.

ISSN:1923-4287    

DOI:10.1139/cjr48c-002

出版商:NRC Research Press    

年代:1948

数据来源: NRC

摘要:

A method for determining seed size of flax by a volumetric measurement was devised as an alternative to weighing the seed. The volumetric or 'displacement' measurement can be expressed by means of a factor, in terms of 1000 kernel weight in grams. The 'displacement' method is more rapid than weighing the seed.

ISSN:1923-4287    

DOI:10.1139/cjr48c-003

出版商:NRC Research Press    

年代:1948

数据来源: NRC

摘要:

A heretofore undescribed isolate ofStreptomyces, capable of producing actinomycin in submerged culture, has been studied. The antibiotic substance has been identified chemically and biologically as actinomycin.

ISSN:1923-4287    

DOI:10.1139/cjr48c-004

出版商:NRC Research Press    

年代:1948

数据来源: NRC

摘要:

A method has been described for the isolation of a crystalline fluorescent compound that occurs in Green Mountain potato tubers during the first year of infection with leaf roll virus. The substance was identified as 7-hydroxy-6-methoxy 1:2 benzopyrone (scopoletin), previously isolated by Best from tobacco plants, infected with tomato spotted wilt virus.

ISSN:1923-4287    

DOI:10.1139/cjr48c-005

出版商:NRC Research Press    

年代:1948

数据来源: NRC

摘要:

The complication of a tomato breeding project by the occurrence, in lines carrying immunity fromCladosporium fulvumCooke physiologic races 1 to 4, of a spontaneous and destructive necrosis, chiefly of the foliage, has been described.The autogenous nature of this necrosis has been established thoroughly and the simple Mendelian nature of its inheritance determined. Immune plants, possessing the factor, are potentially necrotic if they are homozygous with respect to the factorne, found inLycopersicon esculentumMill., but remain non-necrotic if homozygous or heterozygous with respect to its dominant allele,Ne, found inL.pimpinellifolium(Jusl.) Mill. Plants susceptible toC.fulvumare invariably non-necrotic.The visible expression of the gene combination,nehas been shown to vary widely according to the environmental conditions, seasonal variations in the severity of necrosis being particularly striking.The factornehas been located on Chromosome I by three-point experiments.Necrosis appeared in derivatives of crosses betweenL.pimpinellifoliumand all the varieties ofL.esculentumtested.The data indicate the presence, inL.pimpinellifolium, of modifying factors that reduce the severity of necrosis occurring in the presence of the gene combination,ne. Evidence has also been presented that one or more factors on Chromosome VII, closely associated with the factorH(smooth stem), which occurs inL.pimpinellifolium, may prevent the development of necrosis in immune plants of genotypene/ne, but the analysis of this phase of the problem is incomplete.Necrosis is considered to be the visible expression of an incompatibility betweenand a chromosome complex derived very largely fromL.esculentum. Speculations concerning the possible evolution, inL.pimpinellifolium, of immunity fromC.fulvumphysiologic races 1 to 4 and of freedom from necrosis are outlined.The bearing of the results of these studies upon projects for the breeding of tomatoes resistant toC.fulvumis discussed, particularly in the light of the discovery of races of this fungus that are capable of infecting such varieties as Vetomold, which is immune from races 1 to 4.

ISSN:1923-4287    

DOI:10.1139/cjr48c-006

出版商:NRC Research Press    

年代:1948

数据来源: NRC

摘要:

Experiments were carried out at Winnipeg in 1944, 1945, and 1946 to ascertain the effects of leaf rust (Puccinia triticinaErikss.) on the yield, grade, and quality of wheat. Infection in the rusted plots ranged from 22% on some varieties to 87% on others. In these tests, reductions of as much as 26% in yield of straw 40% in yield of seed, 27% in kernel weight, and 3.5 lb. in bushel weight were caused by infections ranging from 78% to 87%. Lighter infection caused smaller but important reductions. Heavy infection generally reduced grades by one commercial grade while light to moderate infection caused no grade reduction. With but one exception, leaf rust decreased the percentage protein content of the seed, although in the majority of cases it increased baking strength as measured by loaf volume. The carotinoid content of the seed was invariably increased by leaf-rust infection.

ISSN:1923-4287    

DOI:10.1139/cjr48c-007

出版商:NRC Research Press    

年代:1948

数据来源: NRC

摘要:

Winter crown rot or snow mold of alfalfa, clovers, and grasses, caused by an unidentified low-temperature basidiomycete, is widespread and often of major importance in the central and northern areas of Alberta and Saskatchewan. For example, during a six year period an average of 62% of the alfalfa stands examined in west-central Alberta were affected, and the average estimated damage was 10%. Severe damage also occurs in alsike and white Dutch clover, and in timothy, red top, and creeping red fescue. The disease is less prevalent in red clover, Kentucky bluegrass, and meadow fescue, and seldom occurs in brome grass, crested wheat grass, and slender wheat grass. Iris and other garden perennials, as well as dandelion, quack grass, and various wild plants are also damaged.The pathogen attacks the dormant plants beneath the snow during the first thaw in the late winter or early spring. The plants are killed or weakened in irregular patches as the result of rotting of the crown buds and tissues. These symptoms are distinct from those of true winter killing, with which the damage has been confused. The pathogen is difficult to isolate, except at a temperature near freezing from superficial mycelium or freshly infected tissues.The results of infection experiments in the field and under controlled conditions indicate that the development of the disease is associated with physiological changes in the host. Inoculated alfalfa plants brought inside at weekly intervals became susceptible at dates varying from late November to late December in different seasons. Infection was most severe under the conditions provided by a slowly melting snow cover and was also influenced by soil temperature, soil moisture, and growth of the pathogen.The pathogen appears to spread mainly by means of mycelium, since no sporulating stage has been found. The mycelium spreads both above and below ground at the time of the first spring thaw. The distance of radial spread, as measured by killing of the plants, varied in different years from 2.7 to 7.5 in. in dense alfalfa stands, and from 0. 5 to 6.0 in. in bare land.

ISSN:1923-4287    

DOI:10.1139/cjr48c-008

出版商:NRC Research Press    

年代:1948

数据来源: NRC

摘要:

The decomposition of wheat, oat, or barley straw in soil caused a marked increase in the microflora, as indicated by plate counts. The oat straw compost yielded significantly more colonies of fungi than either the wheat or barley straw composts. The population of bacteria and actinomycetes was increased to about the same degree by all three of the composts.In another laboratory experiment, wheat, oats, barley, and beans were planted in various rotations in pots of soil from field plots known to be heavily infested with the root-rotting pathogensHelminthosporium sativumP. K. and B.,Ophiobolus graminisSacc., andFusariumspp. Fungi, mostlyPenicilliumspp. andMucorspp., were up to 15 times more abundant from the rhizosphere of wheat roots than from the rhizosphere of oat, barley, or bean roots, regardless of crop sequence. It is assumed that the higher counts of saprophytic fungi obtained from the rhizosphere of wheat seedlings were directly correlated with the greater amount of dead root tissue on this crop, since disease on the wheat seedlings was more severe than on the other hosts. In a duplicate experiment in fallow soil, the rhizospheres of wheat, oats, barley, and beans yielded about equal numbers of fungi.

ISSN:1923-4287    

DOI:10.1139/cjr48c-009

出版商:NRC Research Press    

年代:1948

数据来源: NRC

摘要:

The type of apparatus designed by Dingle and Pryce for determining the concentration of carbon dioxide in air by non-spectroscopic measurement of its absorption of infrared has been modified so as to increase its accuracy greatly. Less than one part by volume of carbon dioxide in a million of air can now be measured at speeds ranging from 10-min.-interval to continuous readings. Water vapor can also be measured accurately and continuously.Examples are given of the use of the technique in following the time course of photosynthesis and transpiration, including a correlation of the courses of these processes with leaf temperature and stomatal movement during rapid wilting of a detached leaf ofPelargonium.

ISSN:1923-4287    

DOI:10.1139/cjr48c-010

出版商:NRC Research Press    

年代:1948

数据来源: NRC