摘要:

Membranes in cabbage root hairs infected byPlasmodiophora brassicaeWor. and in non-infected cabbage root hairs were investigated by the freeze-etching technique after glutaraldehyde fixation and glycerination. Non-infected root hair membranes were characterized for the first time by freeze etching, and their features were generally similar to those of membrane systems in other cell types. Plasmalemmasomes were observed in infected and in non-infected root hairs to have particle-free fracture faces. Similar fracture faces occurred in the outermost membrane of the envelope surrounding young amoebae in the root hairs; but, the plasma membranes of parasite cysts bore particles, and these showed an unusually strong tendency to adhere to the inner fracture face. In view of this new evidence the possible origin of the amoebal envelope is discussed. Striking developmental changes which occur in the interfacial membranes during the first 21 h of parasite growth are described and discussed.

ISSN:0008-4026    

DOI:10.1139/b74-189

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Colonies of the perennialHieracium floribundumWimm. and Grab, had four zones, identified by the density of the rosettes. Belts of sod were analyzed to determine the characteristics of these zones in a pasture which had not been grazed for 5 years. The advancing outer zone consisted of widely spaced rosettes that were less than 2 years old. These rosettes had short rhizomes and large leaves, reproduced by stolons, and flowered abundantly, producing numerous heads per inflorescence. In the central zone, which had the highest density, the rosettes were more than 2 years old, had long rhizomes and small leaves, and did not flower. Seedling numbers were insignificant in all zones. In this species stolons are produced only on plants that have flowered. At high densities curtailment of population growth resulted from reduced flower production and the number of associated stolons initiated per flowering plant.

ISSN:0008-4026    

DOI:10.1139/b74-190

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The apical thickening of the ascus is composed predominantly of a relatively homogeneous and granular ground material laid down between the outer and inner wall layers of the ascus. A cylindrical pore with a central pore plug passes through the apical thickening. The cylinder is continuous with the outer ascus wall layer and extends into the lumen of the ascus. The plug, which obstructs the pore cylinder, consists of a material similar to or identical with the ground material in appearance. There is no outer ascus wall layer overlying the top of the pore plug but at the bottom the inner ascus wall layer separates the pore plug from the ascus lumen beneath. As a result of ascospore dispersal, the pore cylinder becomes everted.

ISSN:0008-4026    

DOI:10.1139/b74-191

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The scanning electron microscope and the freeze-etch technique were used to demonstrate the presence of corrugated cell walls in cotyledon mesophyll cells from dry squash seeds. These wavy cell walls straightened out during imbibition. In the scanning electron micrographs no wavy cell walls were observed in the smaller epidermal cells. Tissue imbibed for 2 h and then air-dried contained corrugated cell walls, whereas similar imbibed tissue dehydrated in ethanol and propylene oxide contained smooth cell walls. Thus the method of seed dehydration is important in determining the appearance of wavy cell walls. Glutaraldehyde fixation during the 2-h imbibition process did not alter the conditions under which wavy cell walls reappear.

ISSN:0008-4026    

DOI:10.1139/b74-192

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The uptake and translocation of42K deposited on corn leaves (Zea maysL.) decrease significantly when the osmotic potential of culture solutions is lowered to –8.2 atm with polyethylene glycol (PEG 1000),before the application of42K. The effect of this water stress on the translocation and distribution of42K was not completely reversible in plants temporarily growing on the solution of smaller osmotic potential. After a 25-h period of recovery on a solution without PEG, there was always a difference between plants either not treated or treated previously with PEG. It appears clearly that the rates of translocation vary directly with the water content of plants.

ISSN:0008-4026    

DOI:10.1139/b74-193

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The incidence of Hypoxylon canker, caused byHypoxylon mammatum(Whal.) Miller, on ramets of 80 pole-sizedPopulus iremuloidesclones was determined on three sites near Pellston, Michigan, and two sites near Iron River, Michigan. Variation in the incidence of canker within clones was slight. No significant difference (P >.05) in canker incidence was found among NE, SE, SW, and NW quadrants of 47 clones on the Pellston Plain site. Significant differences (P <.005) were found among clones in the incidence of canker in four of the five sites studied. In some cases, nearby or adjacent pairs of clones showed significant and striking differences in the incidence of canker infection. The range in canker incidence (percentage of living and dead ramets with stem or branch cankers) for all clones was 9 to 90%; the range was wide on all sites. Low stand density and light bark color of ramets were both significantly (P <.01 andP <.05, respectively) correlated with high canker infection.Although genetic differences between clones in the incidence of canker were not proven, the marked phenotypic differences among clones and other findings suggested moderate genetic control on four of the five sites investigated. In studies relating the incidence of canker to site and biotic factors, the clonal structure of aspen stands should be recognized, and the clone should be used as the basic unit of sampling.

ISSN:0008-4026    

DOI:10.1139/b74-194

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Variations in the amounts of auxins, gibberellins, and inhibitors in vegetative buds ofPopulus balsamiferaL. with the passage from winter dormancy to the spring flush of growth were examined using bioassay techniques. The patterns of change found for gibberellins and inhibitors and for the ratios between them were similar to the patterns reported earlier (Bachelard and Wightman 1973, unpublished) in the physiology and biochemistry of the buds.These results, and others reported in the literature, suggest a possible mechanism of dormancy release and subsequent growth from the buds. This mechanism involves gibberellins, inhibitors, and cytokinins and focusses attention on the coordination of growth in the whole plant.

ISSN:0008-4026    

DOI:10.1139/b74-195

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Microinjection of solutions of14C-sucrose,14C-aspartic acid, K332PO4,42KCl, and3HHO have all been made into living sieve elements of displaced, isolated, phloem strands ofHeracleum. The profile of tracer movement is reported in experiments between 1 min 40 s and 8 min in duration in strands prepared both with and without callose-reducing buffer under conditions where lateral transfer of tracer is restricted. Two types of translocation patterns are discernable, a mass flow near the origin and a type of pulse flow superimposed on it and extending along the strands in both directions simultaneously. Some42K and32P has been detected with the14C in the pulses, but14C-sucrose also appears to move independently of the other tracers.

ISSN:0008-4026    

DOI:10.1139/b74-196

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

New data or amended descriptions are given forPuccinia aberrans, P. arabicola, P. dentariae, P. drabae, P. eutremae, P. oudemansii, andP. utahensis. P. dentariaevar.sublevisvar. nov., onDentaria tenella, andP. drabicolasp. nov., onDraba incertaandDrabaspp., are named.

ISSN:0008-4026    

DOI:10.1139/b74-197

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The banks of many of the hot springs in Yellowstone National Park (U.S.A.) are populated almost exclusively by the wild flowerMimulus guttatus. Studies were undertaken to attempt to determine the nature of the adaptations this species possesses to enable it to survive in this thermophilic environment. Measurements of the heat stabilities of cytoplasmic proteins from this plant provide no evidence to indicate any unusual thermostable properties at the biochemical level. Similarly, the temperature optimum for growth of this species in tissue culture is not dramatically different from that of tissue taken from related or unrelated plants. Since this species has no obvious detectable differences in thermostability at the biochemical and cellular level, it is concluded that its ability to populate these areas may be primarily due to its hydrophytic nature as well as its ability to reproduce vegetatively.

ISSN:0008-4026    

DOI:10.1139/b74-198

出版商:NRC Research Press    

年代:1974

数据来源: NRC