摘要:

Prior to 1940 the botanical surveys of Anticosti were restricted to the coast and seldom further inland than the lower parts of a few rivers. Following an initial visit to the center of the island in 1940, the author crossed the inland on foot from the mouth of the Vaureal to the mouth of Chaloupe creek in 1942. The present paper first describes the vegetation of the sector surveyed. Then follow a discussion on its economic importance in relation to wildlife, the description of new varieties, forms and hybrids, the complete list of species collected in the surveys of 1940 and 1942,—the main purpose of which was to supplement the documentation amassed by Prof. Marie-Victorin in preparation for his monograph on the Anticosti and Mingan flora,—and the author concludes with views on the phytogeography of Anticosti. Contrary to Prof. Marie-Victorin's hypothesis, no preglacial refuge exists in the center of the island and the presence of arctic and cordilleran relicts there may be postulated by the hypothesis of arctic and alpine outposts.

ISSN:1923-4287    

DOI:10.1139/cjr50c-013

出版商:NRC Research Press    

年代:1950

数据来源: NRC

摘要:

F2progeny fromF1plants monosomic for chromosome IX of Hymar obtained from the cross of chromosome IX deficient Chinese Spring × Hymar, a variety of club wheat, were studied for spike type segregation and chromosomal constitution. Spikes from plants with two members of chromosome IX from Hymar were club, intermediate, or common-type. Spikes from plants monosomic for chromosome IX were likewise club, intermediate, or common type but all had typical speltoid characteristics. When the spike type segregates were combined, there resulted an almost perfect fit to a 1:2:1 ratio of club, intermediate, and common spike type plants, respectively, indicating that chromosome IX was not associated with inheritance of spike type. It is suggested that subcompactoidy and compactoidy resulting from an increase in the dosage of chromosome IX is caused by an increase in the dosage of the gene for square-headedness carried by this chromosome. The shortening of plants having higher dosages of chromosome IX is probably caused by abnormal chromosomal constitution resulting in genetic unbalance.

ISSN:1923-4287    

DOI:10.1139/cjr50c-014

出版商:NRC Research Press    

年代:1950

数据来源: NRC

摘要:

In a search for suitable material for a cytological study of plant tumors, pure and virulent cultures ofAgrobacterium tumefacienswere inoculated into stems of youngVicia fabaplants without result. On the other hand, a bacterium isolated from Himalaya blackberry produced large tumors. A comparison of the two forms as to their virulence on other plant species showed that the blackberry organism would not attack tomato,Nicctiana glutinosa, andDatura medeloides, all highly susceptible toA.tumefaciens. Sunflower proved to be a common host to the two pathogens, but the host responses showed significant differences. The tumors caused by the blackberry organism were smaller and were not accompanied by epinasty of the leaves immediately above the tumor, a characteristic feature associated with tumor formation induced byA.tumefaciens. From cultural characters and differences in host range, it was decided that the blackberry organism belongs toAgrobacterium rubi(Hildebrand) Starr & Weiss., a species considered as confined toRubusspecies. Its host range is obviously much wider than this and, as it embraces plants only slightly or not at all susceptible toA.tumefaciens, it is likely to prove an important addition to this species in providing material for the study of plant tumors.

ISSN:1923-4287    

DOI:10.1139/cjr50c-015

出版商:NRC Research Press    

年代:1950

数据来源: NRC

摘要:

In experiments in which nonviruliferous colonies (25 to 50 individuals per plant) ofMyzus persicaeSulc. were caged from 7 to 10 days on healthy potato vines growing under field conditions, the tubers failed to develop phloem necrosis. Under comparable conditions, the tubers from healthy plants caged with leaf-roll-infective colonies of this vector developed severe phloem necrosis. When planted, these tubers produced leaf-roll-infected plants.

ISSN:1923-4287    

DOI:10.1139/cjr50c-016

出版商:NRC Research Press    

年代:1950

数据来源: NRC

摘要:

The natural infection of radish seed withA.Raphanimay result in a lack of germination, a pre- or postemergence blight, a distinctive lesioning of cotyledons and hypocotyls, the presence of scablike lesions on table radish, and in the spotting and blighting of leaves, stalks, and siliques. The fungus was isolated from the internal tissues of all parts of dormant radish seed. Although the pathogen has been reported only on radish in Canada and the United States, the present investigation shows that Canadian isolates are capable of causing a severe leaf blight of stocks and wallflowers. Under field conditions at St. Catharines, Ont., most rapid progress of the disease occurred at temperatures within the optimum range for the fungus, i.e., 22° to 26 °C. Experimental evidence suggests thatA.Raphanidoes not establish an overwintering inoculum in the soil by means of diseased plant debris. Increased soil moisture was associated with increased seedling disease. At a high soil moisture content, infection was lowest at 18 °C.; at medium soil moisture, it was lowest at 18 °C. and also at 23 °C., the next highest experimental temperature.Monosporous isolations showed the presence of numerous wild type strains ofA.Raphaniwhich were closely related culturally. Five of these studied intensively differed widely in virulence and sporulation, but had similar growth rates and nutritional requirements for maximum growth. Although most isolates ofA.Raphaniproduced only a few spores in ordinary agar cultures, abundant sporulation was obtained by wounding plate cultures and removing the lids of the culture plates. In agar culture, the wild types readily produced mostly appressed variant strains also showing close cultural relations. These variants exhibited wide differences in pathogenicity, rate of growth, and nutritional requirements, but all showed practically complete loss of sporulation either in normal or wounded cultures. The effects of cultural variation of wild type strains on cultural habit, pathogenicity, rate of growth, sporulating capacity, and nutritional requirements were random and unrelated. These data, as well as the spontaneous origin and irreversibility of the variants, favored the view that they arose in culture by mutation in the naturally occurring strains.A.Raphaniwas shown to be capable of surviving at least 18 months in dry soil cultures with no loss of cultural habit, virulence, or sporulation.Appreciable increase in emergence and decrease in seedling infection was obtained by seed treatments with some of the common fungicidal dusts.

ISSN:1923-4287    

DOI:10.1139/cjr50c-017

出版商:NRC Research Press    

年代:1950

数据来源: NRC

摘要:

The adaptation of the genusChrysomyxato a short growing season is discussed. Keys are given to the aecial and to the uredinial or telial stages of species that occur in North America. Range extensions are given, particularly for northern Canada.C.Rhododendri, newly reported in North America, andC.Cassandraeare shown to be barely distinguishable fromC.Lediand are made varieties of it.C.Woroniniis reported for the first time in North America.

ISSN:1923-4287    

DOI:10.1139/cjr50c-018

出版商:NRC Research Press    

年代:1950

数据来源: NRC

摘要:

Studies of serial tangential sections of the secondary xylem indicated that increase in girth of the cambium was accomplished not by regulated divisions spaced merely to bring about the required increase in circumference, but by such rapid multiplication of initials as to produce a great superfluity if all survived. Owing to the rapid production of new initials and the associated high ratio of disappearance, the pattern of cells in the cambium changed quickly. This necessitated extensive intercellular adjustments which apparently were of rapid completion. No support was found for Priestley's theory that cell adjustments in the cambium are gradual and of a "symplastic" nature.

ISSN:1923-4287    

DOI:10.1139/cjr50c-019

出版商:NRC Research Press    

年代:1950

数据来源: NRC

摘要:

Studies of the secondary xylem and phloem indicated that after their origin in anticlinal division, sister fusiform initials usually elongated rapidly, particularly at their overlapping tips. After this first phase, rate and amount of extension varied, both along the overlap and at the opposite ends. Often elongation proceeded in a somewhat periodic fashion, being determined in part by inherent factors and in part by position and behavior of the adjoining cells. Sometimes elongating tips were temporarily stalled at blocking rays, while at other times very rapid extension occurred in association with loss of a neighboring initial from the cambium. Growth appeared to be apical, "intrusive" in the sense that the elongating tips thrust between other cells. No evidence was found to support the theory of simultaneous elongation of considerable portions of adjoining walls by "symplastic" growth.

ISSN:1923-4287    

DOI:10.1139/cjr50c-020

出版商:NRC Research Press    

年代:1950

数据来源: NRC

摘要:

Lemna minorL. was grown aseptically in darkness for 189 days in a modified Hoagland's solution, containing 1% sucrose, acid-hydrolyzed casein 800 mgm., and yeast extract 40 mgm. per liter as essential ingredients. Etiolated fronds, with root primordia that failed to elongate, were produced at about one-sixth of the rate in light.Lemnacould not utilize nitrate, ammonium, or urea as heterotrophic nitrogen sources, nor were supplements of acetate, pyruvate, malate, fumarate, succinate, or citrate beneficial in the presence of sucrose. No single amino acid, of 23 tested in a medium containing sucrose plus yeast extract, was as effective as casein hydrolyzate. At suitable concentration, DL-phenylalanine, β-alanine, DL-isoleucine, DL-methionine, and DL-aminobutyric acid were utilized for growth without harmful effects, but other amino acids were either injurious or without effect. Frond development was more normal at low nitrate concentration, but potassium concentration had to be proportionately reduced to avoid inhibition. Growth was not limited by the concentration of other major elements, minor elements, or the degree of aeration. Sucrose feeding and increased photosynthesis had additive rather than competitive effects upon accumulation of growth factors in plants transferred from light to darkness.Spirodela oligorrhizaKurtz, utilized nitrate heterotrophically to a limited extent. Albino maize was grown to the stage of ear formation by feeding sucrose to the leaves and nitrate to the roots. Growth was not promoted, however, by corn seed diffusate, coconut milk, or ammonium plus casein hydrolyzate supplied to the leaves. Albino barley fed sucrose through the leaves did not grow beyond the seedling stage. The heterotrophic requirements reported for various plants, plant organs, and tissues are compared, and the existence of two mechanisms of nitrate assimilation, one of which requires light, is discussed.

ISSN:1923-4287    

DOI:10.1139/cjr50c-021

出版商:NRC Research Press    

年代:1950

数据来源: NRC

摘要:

Previous cytological studies of plant tumors have been carried out on unsuitable material, and on the assumption that the normal tissues in which tumors are induced are exclusively diploid. The present study investigates the condition in normal stem cortex and pith ofVicia faba, in which tumors can be regularly induced through inoculation with pure cultures ofAgrobacterium rubi. Mitoses were induced by treatment with indole-3-acetic acid, and it was found that a very considerable degree of polyploidy exists in both tissues. In the pith the percentage of polyploid mitoses increases with some regularity from the nodal to the mid-internodal region, where it may be as high as 50% of the total. In the cortex, the difference in this regard is less striking, but still exists. Both tetraploid and octoploid cells were found, the latter being less than 10% of the total. In both cases, there was usually close association of homologues in both pro- and metaphase, but in the cortex a considerable number of nuclei did not show this association. The pairing is at times accompanied by chiasma formation. These findings must be taken into account in studying the relation of polyploidy to tumor development.

ISSN:1923-4287    

DOI:10.1139/cjr50c-022

出版商:NRC Research Press    

年代:1950

数据来源: NRC