摘要:

Soils collected from seven sample plots in a burned mixed-wood area in northern Saskatchewan were held at optimum laboratory conditions to determine the number of viable seeds and latent underground buds. A total of 270 plants developed, representing a rate of emergence of 426 plants/m2of which 372 plants (87%) originated from seed and 54 (13%) came from remnant roots or rhizomes. In addition, 19 birch seeds were extracted from the soil following the germination tests giving a total count of 456 propagules/m2. Tree species accounted for 42.9% of this total.

ISSN:0008-4026    

DOI:10.1139/b79-011

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Experiments are reported which demonstrate characteristic differences among pure lines of wild oats in the degree to which seed dormancy is influenced by temperature during seed development. In some lines, high temperature during seed maturation greatly reduced the duration of primary dormancy; in others, this effect was relatively slight. Evidence is discussed that two temperature-sensitive physiological processes influence the duration of dormancy in this species.

ISSN:0008-4026    

DOI:10.1139/b79-012

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Pigmentation mutants ofGracilaria tikvahiaethat differed in several ways from the brownish colour of wild type were characterized genetically by complementation and recombination. Thirty cistrons with multiple alleles at several loci were identified. Many of the cistrons were genetically linked with one or more other loci, and the beginnings of a linkage map is presented. Examples of intragenic recombination between noncomplementing mutants were also encountered.

ISSN:0008-4026    

DOI:10.1139/b79-013

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

White clover (Trifolium repensL.) andStemphylium sarciniforme(Cav.) Wilt. each produced a β-glucosidase which hydrolyzed linamarin and cyanogenic glucosides in crude extracts of white clover. The relative activities of these β-glucosidases were determined at 0, 48, and 96 h after inoculation of three white clover selections that differed in the presence or absence of cyanogenic β-glucosides (G) and β-glucosidase (E), i.e., G+E+, G+E−, and G−E−. The β-glucosidase from white clover precipitated from aqueous solution at 50% saturation with ammonium sulfate was cationic at pH 5.0 and had equal activity on linamarin and amygdalin. The β-glucosidase fromS. sarciniformeprecipitated from solution at 75% saturation with ammonium sulfate was anionic at pH 7.1 and was three times more active on amygdalin than on linamarin. The amount of host β-glucosidase activity in the G+E+white clover inoculated withS. sarciniformedecreased 39% in the interval 48 to 96 h. β-Glucosidase with activity on white clover substrates was not extracted from either the G+E−or G−E−selections before or after inoculation. Pathogen β-glucosidase was detected first in all selections at 48 h and had increased by 96 h to 160, 290, and 260%, respectively, in the G+E+, G+E−, and G−E−selections.

ISSN:0008-4026    

DOI:10.1139/b79-014

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The haploid stage ofPuccinia reconditainThalictrum speciosissimumwas established by basidiospore infection. Haploid hyphae were inter- and intra-cellular. Intracellular structures arose from intercellular hyphae without prior formation of specialized mother cells. They gained entrance into host cells via wide-diameter penetration sites; they were hyphal-like and formed abundantly in both mesophyll and epidermal cells. Commonly, they exited host cells to become intercellular hyphae or intracellular hyphae in adjacent host cells. Numerous, globose pycnia were borne in wart-like humps on the leaf tissue. Paraphyses and flexuous hyphae extended through the ostiole, initially aggregated into a column, but later become radiate. Globose to oblong aecia developed one to three cells below the lower epidermis of humped leaf tissue. Aeciospore initials arose from a stroma of sporogenous tissue at the base of the aecia. Successive divisions of aeciosporophores produced catenulate aeciospores separated by intercalary cells. The first appearance of aeciospore wall ornaments (verrucae) was associated with the division of aeciospore initials into aeciospores and intercalary cells. The electron-lucent verrucae were contiguous with the spore plasmalemma and enlarged to full size (ca. 0.5 × 0.3 μm) in the primary cell wall. During maturation aeciospores underwent a two- to three-fold increase in diameter and the intercalary cells disintegrated. Simultaneously, the primary wall of the aeciospores broke down, exposing the verrucae. The secondary wall formed centripetal to the disintegrating primary wall to provide the major portion of the mature spore wall. The verrucose, mature aeciospores were globose to elliptical (ca. 16.5 × 19 μm). Germ pores were locally thickened areas within the secondary cell wall and contained small electron-lucent interspersions. The peridial cells which delimit the aecia were differentially thickened. The thick outer cell wall contained dagger-shaped, electron-lucent processes and the relatively thin inner wall was ornamented with smooth, knob-like, electron-lucent clavae.

ISSN:0008-4026    

DOI:10.1139/b79-015

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Conidia ofHelminthosporium turcicumPass, trapped on water agar below diseased sweet corn seedlings were germinated under different conditions of illumination and their development was studied after 10 h of incubation. Variations in light intensity and quality affected neither the ability of conidia to germinate nor total germ-tube length. However, blue light of low intensity protected the fungus against germ-tube abnormalities as did daylight of higher light intensity.

ISSN:0008-4026    

DOI:10.1139/b79-016

出版商:NRC Research Press    

年代:1979

数据来源: NRC