摘要:

The natural vegetation of southern Saskatchewan prior to settlement has been reconstructed from 2500 township plats compiled during the Dominion Lands Survey of the 1880's. The north–south section lines within each township were used as transects from which percent cover of grassland, woodland, scrub, brulé, marsh, and open water was calculated and compiled in map form. Although directly comparable modern data are not available, it is concluded that woodland areas have increased over the last 80 or 90 years.

ISSN:0008-4026    

DOI:10.1139/b80-236

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Five collections of modernPicea glaucapollen, four ofP. mariana, and two ofP. rubenswere examined in an attempt to distinguish the pollen of the species. Three morphological variables were recorded for individual grains in each collection. The sculpturing of the furrow membrane is not diagnostic, but the presence of an undulating margin to the cap and of irregular reticulation in the sacci characterizeP. rubenspollen. Seven size variables were also measured for each grain. No simple combination of morphological and size criteria provides effective discrimination betweenP. glaucaandP. marianapollen.Linear discriminant analysis was applied to the size data forP. glaucaandP. mariana. The mathematical assumptions of the method were tested, and to satisfy them, the discriminant analysis was confined to six of the seven variables measured. The discriminant analysis resulted in 91.5% of the pollen being correctly distinguished.The same six variables were measured on fossilPiceapollen from two Late Wisconsin sites in Minnesota and one Holocene sequence in Labrador. The individual fossil grains were assigned to eitherP. glaucaorP. marianaby means of discriminant analysis. The Late Wisconsin spectra consist of both species, a result supported by macrofossil evidence.Picea glaucapredominates in the early Holocene spectra from Labrador. It is replaced byP. marianaafter about 5000 years before present, reflecting paludification and the spread of muskeg.The limitations of the procedure are discussed, and its potential is emphasized.

ISSN:0008-4026    

DOI:10.1139/b80-237

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Seven types of chalazal modifications have been reported to occur as normal developmental changes in angiosperm ovules. Among them is the hypostase, a group of usually lignified cells. InOrnithogalum, hypostase differentiation becomes evident during the meiotic–mitotic interphase. Differentiation proceeds toward the micropylar end of the ovule at first but later becomes bidirectional. Differentiation is usually completed after the third mitotic division of the megagametophyte has occurred. One to three hypostase cells per ovule have what appears to be a nonstarch carbohydrate storage product. The greatest proportion of starch reserves in the mature ovule occurs in the chalazal end of the nucellus and, although the hypostase does not seem to be an important storage tissue, it probably has an integral function in the translocation of nutrients into the megagametophyte and, after fertilization, into the embryo sac.

ISSN:0008-4026    

DOI:10.1139/b80-238

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

A detailed morphological comparison was made betweenDichodontium pellucidum(Hedw.) Dix. andD. olympicumRen. & Card, in search for new taxonomic features. The two species are found to differ distinctively in cellular details of the ventral surface of the leaf costa, exothecial cells, and in sexuality. A distribution map is prepared forD. olympicum, a western North American endemic. Comparisons of anatomical features are also made between the two taxa ofDichodontiumand European specimens ofOreoweisia serrulate(Funck) DeNot. The results support the assertion that all North American specimens ofOreoweisia serrulatashould be referred toDichodontium pellucidum.

ISSN:0008-4026    

DOI:10.1139/b80-239

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The results of a survey of the element content of saxicolous and terricolous lichens collected from the Northwest Territories, Canada, are summarized. Fourteen lichen species were collected from 45 sites and the lichens were analysed for 20 elements by instrumental neutron activation and X-ray fluorescence.An enrichment factor (EF) was calculated for each element analysis. The elements aluminium, chromium, iron, sodium, titanium, and vanadium had mean EF values of 1–5 for all species. These low EF values indicated that, relative to average values for crustal rock, there was no enrichment of these elements in the lichens concerned. For other elements (chlorine, lead, and sulphur) consistently higher EF values were obtained. These higher values were interpreted in terms of (a) differing methods of element accumulation, (b) sources of elements both natural and anthropogenic other than crustal rock and (or) soil, and (c) marked deviations of the actual substrate concentrations from the average crustal-rock concentrations used.The underlying structure of the data from some species was investigated using ordination techniques. These techniques provided some description of the element associations within the lichen thallus. These element associations were examined in relation to sources external to the plant. A principal component analysis was carried out on the data for each of three species,Cetraria cucullata, C. nivalis, andCladina stellaris. In all cases, the first five principal components explained 81–89% of the variation in the data. One component which had high weightings for aluminium, scandium, and vanadium (with or without iron, nickel, and titanium) was common to all three species. Similarly, a second component with high weightings for calcium (with or without magnesium and potassium) was a consistent feature of each analysis. These and other components were considered in the context of lichen enrichment from crust-derived particulates, the marine aerosol, and certain anthropogenic sources. The high percentage of variation explained by the first five components strongly indicated that the major element sources contributing to this variation were considered. Nonmetric multidimensional scaling supported the principal component solution.There was considerable interspecific variation in the element content of the lichens. Univariate analysis of variance did not show any significant differences between the element content ofCladina arbuscula, C. rangiferina, andC. stellarisor any differences betweenCetraria cucullataandC. nivalison the basis of any single element. However, multiple discriminant analysis did show that the species mentioned could be distinguished (~ 90% discrimination) when all the elements were compared simultaneously. The discrimination between theCladinaspp. was based on the relative efficiency of these lichens in the accumulation of iron, scandium, titanium, and vanadium.

ISSN:0008-4026    

DOI:10.1139/b80-240

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The fine structure of theHarpochytrium hediniiWille zoospore is reexamined using serial sections. All of the major organelles are located in the posterior two-thirds of the zoospore; the anterior region contains only a few vacuoles and a network of filaments. The basal body complex is located at the center of the posterior end of the zoospore. The nucleus and "nuclear cap" are located directly anterior to the basal body complex on one side of the zoospore. All of the microbodies, lipid globules, and mitochondria are arranged into a complex associated with the rumposome along the opposite side of the zoospore. A spore-wide system of cisternae, the vesicular system, is continuous throughout the posterior region of the zoospore. The overall arrangement of organelles in theH. hediniizoospore most closely resembles the internal morphologies of certain chytridialean zoospores. This suggests thatHarpochytriummay be more closely related to the chytrids than has been previously assumed.

ISSN:0008-4026    

DOI:10.1139/b80-241

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The ultrastructure of the zoospores ofOedogoniomyces lymnaeaeandMonoblepharellasp. are reexamined using serial sections. The relative molecular weights of the ribosomal RNA of various chytridiomycetous fungi are also determined and compared. The fine structure of each of these zoospores is very similar. The nucleus and "nuclear cap" are centrally located in the zoospores. The anterior region contains lipid globules, a few large, empty vacuoles and numerous, small vesicles. The posterior region is filled with an electron-translucent material throughout which are scattered spherical mitochondria and large vacuoles with electron-opaque inclusions. The basal body complex is located at the center of the posterior end, and the rumposomal complex is adjacent to the plasmalemma in the posterior region of these zoospores. A system of cisternae that are associated with microbodies appears to connect the lipid globules in the anterior region with the rumposomal complex in the posterior region of these zoospores. Small differences in the structure and distribution of certain organelles are considered minor compared with the overall similarities between these two zoospores. It is suggested thatOedogoniomycesbe transferred to the Monoblepharidales. The fine structure of theHarpochytrium hediniizoospore is not only similar to that of the zoospores studied herein, but also resembles the zoospores of chytrids. The possible relationship ofHarpochytriumto the Chytridiales is supported by zoospore ultrastructure and the relative molecular weights of ribosomal RNA. The data available at the present time suggest that the order Harpochytriales be abandoned and thatHarpochytriumbe considered either a genus of nematosporangial, operculate, eucarpic chytrids or a monoblepharidalean genus withOedogoniomyces. It is recommended that speculation concerning the taxonimic relationship betweenHarpochytriumand other Chytridiomycetes be delayed until more data concerning other species ofHarpochytriumand monoblepharidalean fungi are available.

ISSN:0008-4026    

DOI:10.1139/b80-242

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

CO2exchange (CER) and transpiration (TR) rates of flag leaves, penultimate leaves, and the ear of two winter wheat cultivars (cv. Fredrick and cv. Bezostaya-1), were measured at intervals during the life of the flag leaf. These were grown at two levels of nitrogen (N), 105 and 210 mg L−1, supplied from the double ridge stage of apical development. Nitrogen concentrations and dry weights of the flag and penultimate leaves, and of various other plant parts, were also measured.CER of main culm flag leaves of both cultivars declined more slowly from ear emergence to approximately 2.5 weeks postanthesis than either before or after this period. Similarly, the CER pattern of main culm penultimate leaves of Fredrick showed a plateau during this same period. By contrast, CER of the penultimate leaves of Bezostaya declined more uniformly overtime. CER of illuminated ears declined steadily from anthesis, whereas CER in the dark decreased to a maximum negative value approximately 2 weeks postanthesis. Nitrogen treatment had little effect on these CER patterns, with the exception of Bezostaya penultimate leaves, in which the rate of decline was slower for the higher N treatment.Nitrogen concentrations of the flag and penultimate leaves, and in the nongrain ear component, decreased steadily during the grain-filling period for both cultivars and N treatments. Leaf N concentration also decreased during the preanthesis period in Fredrick at both N treatments, and in Bezostaya at the lower N treatment. The time – course of N concentration in the leaves was not closely mirrored by CER, indicating that factors other than the N concentration of the leaves were important in determining the pattern of CER.TR of the flag and penultimate leaves declined from full flag leaf expansion until anthesis and then rose during a 2- to 2.5-week-postanthesis period for both cultivars and N treatments, with the exception of Bezostaya at the lower N treatment. The increase in TR during the filling period suggests that the reduced rate of decline in CER at that time may have resulted, at least partly, because a reduction in gas phase resistance offset an increase in residual resistance.

ISSN:0008-4026    

DOI:10.1139/b80-243

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Factors and procedures found to increase the quantity and consistency of axenic zoospore production in a selected isolate ofPhytophthora cinnamomiwere (i) the use of single-zoospore cultures of uniform size that were between 48 and 72 h old; (ii) thorough washing of mycelial mats at the time of sporangium induction to remove nutrients; (iii) agitation of the sporulation medium (mineral salt solution) 24 h after the initial induction; (iv) standardization of the volume of the sporulation medium; (v) adequate removal of the sporulation medium and replacement with distilled water before triggering zoospore release; and (vi) placement of colonies that had been induced to sporulate under light. The addition of a purified sporangium stimulatory substance to mycelial mats which had been induced to sporulate enabled the fungus to sporulate under conditions which normally suppressed sporulationin vitro. In the presence of this stimulatory substance, the fungus sporulated prolifically in darkness and with limited quantities of added nutrients. Other isolates ofP. cinnamomiresponded in a similar manner to many of these factors and procedures.

ISSN:0008-4026    

DOI:10.1139/b80-244

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Forest communities were quantitatively analyzed along a south-southeast transect from a large, 70- to 80-year-old smelter complex near Sudbury, Ontario. None currently exist within 3 km SSE of this smelter. At distances of up to 8 km, pockets of remnant forest communities of various sizes occur, mainly on protected slopes and in valley bottoms. Most hilltops are bare of vegetation, denuded of soil, and blackened from the effects of sulfur dioxide fumigations. Beyond this distance, the forests are more or less continuous, although there are still some bare hilltops as far as 15 km from the smelter. The forests which do occur are relatively depauperate in terms of tree diversity and biomass at the closer sites. Similar effects on the ground flora are also documented, although the forest canopy appears to be more greatly affected than the ground flora. Certain species are widely distributed in the inner polluted areas, while others, notably conifers and such ground flora components as bracken fern and most lichens and bryophytes, are absent from sites closer to the smelter.Some changes in the plant communities close to the Copper Cliff smelter have occurred subsequent to the building of a tall (380 m) smokestack in 1972. These have mainly occurred at sites where soils remain, where residual soil toxicity is not excessive, and where midsummer drought is not severe. Colonization has largely involved the spread of such pioneer grasses asAgrostis hyemalisvar.tenuis, A. stoloniferavar.major, andDeschampsia caespitosa, and more vigorous growth of certain surviving woody species. The recovery of denuded, blackened hilltops, essentially a primary succession on naked Precambrian bedrock, will be a much slower process.

ISSN:0008-4026    

DOI:10.1139/b80-245

出版商:NRC Research Press    

年代:1980

数据来源: NRC