摘要:

Pragmopycnis pithyagen. et sp. nov. is introduced for the conidial state ofPragmopora pithya(Fr.) Groves and is characterized by simple, solitary, brown pycnidia, integrated polyphialides, and hyaline, allantoid, aseptate conidia. A comparison is made withSirodothisClements, which provides an earlier name forPleurophomellaHöhnel, a name currently adopted for the conidial states ofTympanisTode ex Fr.Sirodothis populnea(Thüm.) comb, nov.,S. saligna(Höhn.) comb, nov.,S. inversa(Fr.) comb, nov., andS. columnaris(Wallr.) comb. nov. are proposed for the named conidial states of fourTympanisspecies.

ISSN:0008-4026    

DOI:10.1139/b75-064

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Comparative rates of nitrogen fixation in the lichenPeltigera caninafrom subarctic and temperate habitats have been examined using the acetylene reduction method. Maximum acetylene reduction at thallus saturation and with 20000 lx illumination takes place at 16 °C in subarctic material and at 21 °C in temperate material. This adaptation of nitrogenase activity to temperature inP. caninais discussed in relation to low levels of soil nitrogen in arctic systems.

ISSN:0008-4026    

DOI:10.1139/b75-065

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Soil water extract (SWE) has been used for decades to supplement certain algal and fungal cultures, but its active components remain essentially unknown.Cladophora glomerata, an attached green alga which has become a problem in several of the Laurentian Great Lakes and elsewhere, is one species that grows well on synthetic media supplemented with SWE. Unialgal cultures were used to investigate the nature of the active components in SWE with the hope that insight of the nutritional requirements of this alga would be gained.Analysis of SWE showed that an organic heat-labile component was significant, and when thiamine was substituted for SWE, it was found to provide 80% of the stimulation induced by SWE. The presence of thiamine in two samples of SWE was verified, and concentrations of 3 and 10 μg/litre were determined using thePhycomycesbioassay. Subsequent investigations of the requirement of thiamine byC. glomeratademonstrated that 1 μg/litre, provided either by SWE or as the pure vitamin, stimulated satisfactory growth, while 10 μg/litre is the apparent optimum concentration.

ISSN:0008-4026    

DOI:10.1139/b75-066

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

This paper describes a few cytological and ultrastructural modifications during the hardening process of two varieties of winter wheat differing in frost resistance. In leaf cells of the hardier variety, Kharkov, subjected to hardening conditions, the quick and complete disappearance of starch grains in chloroplasts, the undulation of nuclear and chloroplast membranes, and an increase in osmiophilic granules have been observed. In the less-hardy variety, Selkirk, after a month of hardening, starch grains persist in chloroplasts, osmiophilic granules diminish in number and intensity, and vesicles are formed between the double membrane surrounding the chloroplasts. These vesicles are finally liberated in the ground cytoplasm. Their role could be the elimination of substances such as denatured proteins of the chloroplasts.

ISSN:0008-4026    

DOI:10.1139/b75-067

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Teliospores of the cedar-apple rustGymnosporangium juniperi-virginianaewere examined using transmission electron microscopy. Each ellipsoid spore is divided into two cells by a transverse septum. A second septum separates the basal cell of the teliospore from a long, hyaline, cylindrical pedicel. The fine structure of these septa is considered. The cytoplasm of the teliospore is very dense and contains a complement of cellular structures including ribosomes, vacuoles, mitochondria, and a large number of structures thought to be lipid bodies. Each cell of the teliospore contains a single nucleus, in which the chromatin is often considerably condensed. Two germ pore regions are present in each cell. The spore wall is thinnest in these regions and is different in structure than elsewhere around the spore.

ISSN:0008-4026    

DOI:10.1139/b75-068

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

not available

ISSN:0008-4026    

DOI:10.1139/b75-069

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Triangularia backusiin. sp. was isolated from a soil sample collected in Ohio, U.S.A., and was subjected to alcohol treatment.Triangularia backusiiis characterized by oval to pyriform perithecia, elongate-clavate asci, and obovoid ascospores with hyaline, gelatinous appendages. The ascospores are two-celled with a transverse septum; the upper cell is obovoid with a truncate base and brownish black to black and the lower cell is triangular and pale brown to brown. The conidial state is assignable to the genusPhialophora. The new species differs from other knownTriangulariaspecies in having the largest ascospores.

ISSN:0008-4026    

DOI:10.1139/b75-070

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

The African cereal streak disease (ACS) was further characterized as to transmissibility and cytological changes produced in cells of affected plants. Virus-like particles were regularly associated with diseased plants grown under field conditions, but no similar particles could be found in diseased plants of wheat, triticale, rice,Harpachne schimperi, Chloris pycnothrix, orEragrostis tenuifoliagrown in a growth cabinet set on an 18-h–6-h light–dark cycle and a corresponding 24 °C–17.5 °C temperature cycle. The efficiency of continuous transmission byToya catilinaFenn. under growth-cabinet conditions was low, at 5%, 3%, and 5% for females, males, and nymphs, respectively.Except for the absence of recognizable virus-like particles in infected plants grown in the growth cabinet, the symptoms and cytological features of diseased plants grown under growth-cabinet and field conditions were similar. The main cytological features of diseased plants were as follows. (1) A dense, fine ground substance which filled many of the phloem cells was developed. (2) Large numbers of inclusion bodies, which were of globular and hexagonal-elongated forms, were formed. These forms are probably related. Virus-like particles were occasionally associated with the inclusions in diseased field-grown plants (3) Non-specific changes, such as may be induced by various types of pathogens, or are associated with senescence, e.g. phloem cell necrosis, abnormal callose-like cell wall deposits, and degenerative changes in the chloroplasts, were observed.

ISSN:0008-4026    

DOI:10.1139/b75-071

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Pollen of 18 of the 19 species ofEupatorium(sensu stricto) was examined with the scanning electron microscope (SEM). The species studied included the three dog fennels with dissected leaves and 14 species with undissected leaves. All species had echinate tricolporate pollen. One dog fennel,E. capillifolium, was found to have reduced spines relative to the other species. This one had other anemophilous characters, such as a longer stigma and greater stigma exposure, lax inflorescence branches, and smaller floral heads, suggesting an anemophilous pollinating system.Eupatorium compositifolium, another dog fennel, showed characteristics indicative of anemophilous ancestry, such as a long, greatly exposed stigmatic surface and lax inflorescence, but it had showy flowers as well as autecological features conducive to entomophily. All other species had reduced stigma lengths and exposure, stiffly upright inflorescence, and showy heads, all features indicative of entomophily. The advantage of acropetal over basipetal development of the inflorescence for anemophily is discussed. The dog fennels have acropetal, indeterminate development and the undissected leaf species have basipetal, determinate development; the latter of which is the basic pattern of inflorescence development in the Compositae.

ISSN:0008-4026    

DOI:10.1139/b75-072

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

In a recent paper, Purohit and Tregunna (7) concluded that plants with low carbon dioxide compensation values are either short-day or day-neutral in their photoperiodic requirement for flowering. Although many plants with the C4pathway of photosynthesis are short-day plants, there are also several Gramineae in which the C4pathway of photosynthesis is known to be combined with a requirement for, or response to, long days for flowering, such asPaspalum dilatatum, Hyparrhenia hirta, Themeda australis, andSaccharum spontaneum. Consequently, response to short days for flowering is not a constant feature of the C4pathway, and C4plants could be selected for a long-day response in areas where this is advantageous.

ISSN:0008-4026    

DOI:10.1139/b75-073

出版商:NRC Research Press    

年代:1975

数据来源: NRC