摘要:

The ultrastructure of the interfacial zone which separates the intracellular structures of vesicular-arbuscular mycorrhizal fungi from host cytoplasm has been described in a variety of ways by recent investigators. Evidence is presented here which suggests that previous interpretations of the ultrastructure of the interfacial zone have been based on an artifact of fixation. Using an improved procedure, a dense, granular material was found in the interfacial zone. This material was preserved by simultaneous glutaraldehyde-osmium fixation but not by conventional prefixation and postfixation in glutaraldehyde and osmium, respectively.

ISSN:0008-4026    

DOI:10.1139/b77-011

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

A new species of dasycladacean alga is present in the upper Thumb Mountain and in the overlying Irene Bay Formations of the Cornwallis Group on Cornwallis Island, Northwest Territories. The alga is associated with the 'Arctic Ordovician' fauna, which is of considerable biogeographical and biostratigraphical importance. This fauna is believed to be of early Late Ordovician (Caradocian) age.The new alga is a member of the cyclocrinitid tribe and clearly is to be referred to the genusCyclocrinites. It is distinguished from all other cyclocrinitid species by the exceptionally small size, the unusual bilobate form, and the mode of calcification of its thallus. It is believed to have lived in tropical waters which were quiet and shallow, to have been anchored to the seabed by means of rhizoids. and to have grown only in areas in which fine-grained carbonate sediment was accumulating.

ISSN:0008-4026    

DOI:10.1139/b77-012

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Nitrogen deficiency increases the initial saturated rate of ammonium and urea uptake by three green and three blue-green algae. The increase caused by N deficiency is greater in darkness than in the light. Nitrogen deficiency also increases the size of the N debt in these algae. The green algaScenedesmus quadricaudaand the blue-green algaPseudoanabaena catenatawere selected for more detailed study of some factors affecting the rate of ammonium and urea uptake. The uptake of both ammonium and urea by these algae is light-stimulated; that of urea is sensitive to an uncoupler but not to the urease inhibitor acetohydroxamic acid. Ammonium and urea uptake resemble each other in being dependent on the presence of a chelator, but they differ in their pH dependence. They also differ in their dependence on substrate concentration, ammonium uptake showing half-saturation values of 0.1 to 0.3 μg atom N l−1, and urea uptake, 0.4 to 1.4 μgatom N l−1. While ammonium depresses the uptake of urea and urea depresses that of ammonium, the two substrates do not appear to compete for the same site.

ISSN:0008-4026    

DOI:10.1139/b77-013

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

InMimosa pudicaL., the geotropic movement (a slow variety of leaf movement) induced by inverting plants in the gravific field is reversibly inhibited by diethyloxide used in a range of concentrations producing, reversibly, in the same plant, inhibition of the seismonastic leaf movement (a quick variety of leaf movement) and in other organisms, inhibition of various cellular functions such as photosynthesis, caryocinesis, and bacterial luminescence.The degree of inhibition of geotropic leaf movement is dependent upon the concentration of ether, the duration of etherization, the time of anaesthetic admission, and the sequence of the motor organs. Results led to the following conclusions: preliminary etherization of plants, in vertical position, decreases rate of the geotropic movement; etherization occurring during the course of this movement can stop it in certain conditions; geotropic movement is more inhibitedin primary than in secondary motor organs, whereas the opposite occurs in seismonastic movement.The discussion deals with the contribution of these results to the knowledge of leaf geotropism.

ISSN:0008-4026    

DOI:10.1139/b77-014

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Three new species ofArniumare described and illustrated. These areA. calymmatosporumfound on burro dung from Venezuela;A. ditremumon cow and horse dung from U.S.A. and Venezuela; andA. sexdecimsporumon horse dung from Venezuela. Additional records are provided for a number of other species. In several instances additions or corrections are made to previously published information.

ISSN:0008-4026    

DOI:10.1139/b77-015

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Two oat cultivars, Clintland 60 and Garry, were grown to maturity in controlled environments under two temperature regimes with daylength held constant and under two daylengths with a constant temperature pattern. Plants were moved between environments at panicle initiation and at anthesis, dividing the growth period into three phases.Growth and development were hastened by warm temperature and by long days. Temperature treatments caused greater variation in the duration of growth phases in Garry than in Clintland 60, but Clintland 60 was affected more by daylength. Higher plant dry weights were obtained from cool temperature treatments; response to daylength was inconsistent.Grain yield was not closely associated with duration of growth phases. The effect of temperature and daylength on yield components was markedly different in the two cultivars. The greatest grain yield response in Clintland 60 resulted from cool temperature during panicle initiation to anthesis, attributable to increased fertile tiller development. Daylength had limited effect on components. In Garry the greatest yield response was from cool temperatures during anthesis to maturity, with increases in all components. Short days before anthesis increased grain size and number.Implications of observed responses relative to cultivar performance in the field are discussed.

ISSN:0008-4026    

DOI:10.1139/b77-016

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The regeneration patterns for protoplasts ofEntomophthora egressaMacLeod and Tyrrell grown on modified Grace's insect tissue culture medium supplemented with fetal calf serum (a highly modified version of Grace's medium lacking serum and more closely approximating the hemolymph of the eastern hemlock looper), Müller-Kögler's coagulated egg yolk medium supplemented with Tristearin, and water agar are documented. Protoplasts on liquid and egg yolk media had varying degrees of common developmental patterns. On liquid media, development involving prophyphal spheres and fusion spheres predominated. Hyphae emerged from the prohyphal spheres; however, the fusion spheres did not develop further. On the coagulated egg yolk medium, the individual, non-chain, cells coalesced and developed into pleomorphs which later developed into osmotic shock-resistant postprotoplasts. A postprotoplast gave rise to a hypha which produced a terminal conidium. Later resting spores were detected. Water agar supported scant mycelial growth as compared with that on coagulated egg yolk but more than that on the liquid media. Solid substrates appeared to favor mycelial development. Regeneration could be avoided by the addition of fresh Grace's modified medium to either coagulated egg yolk plates or to cultures with Grace's modified medium. Obtaining protoplasts from hyphae and the reversion of these protoplasts to form hyphae appeared to be a fixed property ofE. egressa.This report is believed to be the first for reversion of protoplasts initially produced by non-enzymic means.

ISSN:0008-4026    

DOI:10.1139/b77-017

出版商:NRC Research Press    

年代:1977

数据来源: NRC