摘要:

The contribution of yellow devil hawkweed (H. floribundum) to the total standing crop of an abandoned pasture in southern Ontario increased from approximately 8% to 70% asH. floribundumcolonized the pasture by forming patches containing as many as 3400 rosettes/m2. Within the hawkweed population, there was a significant (P < 0.05) shift in the distribution of standing crop from reproductive to vegetative structures and within the vegetative structures from leaves to roots and rhizome during the process of patch formation. These shifts presumably occurred in response to changing environmental conditions (i.e., increasing light availability, reduced soil moisture levels, greater intraspecific competition). The mechanism by which the allocation pattern changed was more likely phenotypic plasticity than genetic change sinceH. floribundumis an apomict and vegetative reproduction accounted for most recruitment into the population.The frequency distribution of population members in dry weight classes became more negatively skewed during the process of patch formation, but the distribution did not approach log-normality as predicted in some studies. Significant (P < 0.05) differences were observed in the allocation patterns of individuals belonging to different weight classes in the population. Only the largest plants in the population allocated dry weight to reproductive structures.

ISSN:0008-4026    

DOI:10.1139/b78-001

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Laminated sediment (presumed varved) from Greenleaf Lake was examined for evidence of forest fires. A 500-year section dating approximately 770–1270 A.D. was analysed for influx of pollen, charcoal, aluminum, and vanadium using decadal samples. Intervals showing concurrent peaks in charcoal, aluminum, and vanadium influx, varve thickness, and charcoal:pollen ratio were interpreted as representing major fires within the drainage basin of Greenleaf Lake. By these criteria, six fires occurred within 500 years, or one fire approximately every 80 years. The pollen diagram indicates a stable forest composition for the past 1200 years. This, coupled with abundant charcoal fragments in all sediment samples, suggests that fire has been a frequent, natural phenomenon affecting the landscape during this period. There is a significant positive correspondence between peak charcoal influxes and peak influxes of aluminum and vanadium, indicating that increased soil erosion is responsible for their deposition.

ISSN:0008-4026    

DOI:10.1139/b78-002

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The external force method for measuring hydraulic conductivity and elastic coefficients in higher plants cells (Ferrier and Dainty, 1977, Can. J. Bot. 55: 858–866) is applied to multilayer tissue sections, and the theoretical analysis further developed. Measurements on storage tissue cells of red beet (Beta vulgaris) and artichoke (Helianthus tuberosis) give values for the water potential equilibration time constant (τ) of between 1 and 2 min, and values for cell membrane hydraulic conductivity (Lp) between 2 × 10−7and 4 × 10−6 cm s−1 bar−1. Measurements on leaves of the aquatic plantPotamogeton lucensgive similar values for τ, and lower values forLp. Some limitations of the external force method are discussed.

ISSN:0008-4026    

DOI:10.1139/b78-003

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The paper reports on a study that consists of various numerical taxonomic analyses of genera of Triticeae aimed at finding intergeneric relationships based on maximum information and proposing a classificatory scheme. The data consist of morphological features, genetic relationships expressed in terms of successful crosses, and relationships assessed from the occurrence of intergeneric hybrid 'genera.' The morphological data were analysed separately in order to find out if they reflect by themselves the relationships between the genera before the data were combined with the information on crosses and on parentages of intergeneric hybrid 'genera.' The morphologic data consist of a set of 35 characters and one of 45 characters, both with equidistant states, and a set of 35 characters with weighted states. The combinations of data (morphology, crosses, and parentages) were effected through the merging of dissimilarity matrices using a few approaches such as squaring of elements of the matrices, adding the squares and taking their averages, and then taking the square roots of these averages. The relationships between the various matrices (original and combined) were assessed with Gower's technique of comparison of multivariate analyses. To find classifications, the various matrices were processed through cluster analyses. Admissible phenograms and admissible classifications were selected on the basis of a set of criteria. Subsequently, the admissible classifications were assessed using Estabrook's information theory model; a best classification was chosen. A new system of Triticeae is presented even though the data indicate clinal relationships among its members.

ISSN:0008-4026    

DOI:10.1139/b78-004

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Dead needles ofAbies alba, Pinus sylvestris, P. leucodermis, andSequoia giganteawere immersed in a stream for 28 days and then examined for conidiophores of aquatic hyphomycetes. Contrary to statements in the literature, these fungi were found to colonize untreated needles. However, numbers of species and conidiophores were significantly higher on needles treated with steam before immersion than on untreated needles; both values were also higher on cut surfaces (mesophyll) than on intact surfaces (epidermis with cuticle) of longitudinally halved needles.Addition of untreated needle powder (Sequoia, P. leucodermis) to malt extract agar depressed linear growth of pure cultures of five aquatic hyphomycetes. The inhibition persisted when a 0.2-μm membrane filter was placed between medium and fungal cultures. On water agar, by itself unsuitable for fungal growth, low doses of needle powder allowed growth of the same fungi. At higher doses, inhibition again became predominant. Steam distillation of needle powder yielded three fractions: solid residue, soluble residue, and steam distillate. Steam distillate did not influence fungal growth on the two media, while the other two fractions supported growth on water agar but did not lead to a clear dosage–effect curve on malt extract agar.

ISSN:0008-4026    

DOI:10.1139/b78-005

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Panicum virgatumis considered a relatively cold-tolerant C4species to low night temperature from analysis of top growth, photosynthesis, dark respiration, and day–night fluctuation of nonstructural carbohydrate concentration in leaf blades grown under temperature regimes of 30–30, 30–20, and 30–10 °C. There was little influence of night temperature of 10 to 30 °C on top growth, although 20 °C night temperature was optimum. Plants grown under low night temperature (10 °C) showed a slightly reduced rate of photosynthesis early in the photoperiod, while plants at 30 °C night temperature had the highest rates of dark respiration. The time required for the plants to reach maximal photosynthetic rate from the beginning of the photoperiod was prolonged with decreased night temperature, being 1.0, 1.5, and 2.5 h for plants grown at 30–30, 30–20, and 30–10 °C regimes, respectively. Photosynthetic rates progressively declined during the rest of the photoperiod. The change in photosynthetic rate during the photoperiod and influence of night temperature on photosynthesis was highly correlated with the change in stomatal resistance to CO2transfer (r = −0.9). Starch and total sugars in leaves accumulated slightly with time after initiation of the photoperiod and then were reduced to low levels during the night at all temperatures. Night temperature had no effect on the accumulation of these nonstructural carbohydrates during the day or on depletion from the leaves during the night.

ISSN:0008-4026    

DOI:10.1139/b78-006

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The general distribution of the brown algaMacrocystis integrifoliaBory in British Columbia is related to seasonal seawater temperatures and salinities. This species is restricted to regions having little seasonal variation of seawater temperature and salinity or regions where the lower salinities occur during the winter. Locally,Macrocystisdistribution is restricted to moderately wave-exposed areas or areas subjected to appreciable tidal currents, provided solid substrate is available. The vertical distribution is usually determined by substrate availability and sea urchins.Macrocystisblade morphology varies regularly with wave exposure. However, transplant studies indicate that this may, in part, be genetically determined and thus may not be a plastic phenotypic response.

ISSN:0008-4026    

DOI:10.1139/b78-007

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

A centre of genetic diversity for white spruce,Picea glauca(Moench) Voss, is suspected in and around a refugial region in the Yukon Territory. Seed from the refugium (30 samples), a neighbouring region (42 samples) and from southern Ontario (50 samples) was examined for isoenzymes of formic (FDH), glutamic (GDH), and lactic (LDH) dehydrogenases and cationic peroxidases (CP). FDH patterns were uniform. There were three GDH bands which appeared in five patterns. Eleven isoenzymes of LDH were detected in 21 patterns. There were 25 CP bands and the pattern from each collection (containing 7–13 bands) was unique.The results from GDH, LDH, and CP analyses revealed differences between seed from the refugium and the adjoining regions. The patterns for LDH supported the hypothesis that the refugium was a centre of diversity but the GDH and CP patterns were more diverse outside the refugium. The LDH and CP analyses showed that the genetic resources of the two regions in the Yukon were more diverse than those in southern Ontario. Analysis of divergence showed that these differences were significant at the 1% level of probability.

ISSN:0008-4026    

DOI:10.1139/b78-008

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Zygosporangium and zygospore formation inPhycomyces nitenswas followed by correlative light microscopy and scanning and transmission electron microscopy. Compatible multibranched zygophores became interlocked by the interdigitation of their lobes. Progametangia grew up from the substratum in pairs and then differentiated into gametangia and tongs-shaped suspensors. Plasmogamy was deferred until the gametangia were delimited. Development of rings of hyaline appendages on the suspensors was concomitant with plasmogamy. The appendages originated from the tertiary suspensor wall layer and ruptured the outer primary and secondary wall layers prior to development of their terminal thornlike processes.Developing zygosporangia contained a large central vacuole and some organelle zonation; however, these features were not discernible in more mature zygosporangia. A reticulum of electron-opaque fluted warts developed within the secondary zygosporangial wall layer. Cryofractured zygosporangia revealed a smooth hyaline zygospore with truncate ends. Wall layer relations of mature zygosporangia and zygospores were presented. Information obtained was correlated with existing ultrastructural observations on zygosporangiogenesis in the Mucorales.

ISSN:0008-4026    

DOI:10.1139/b78-009

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Apothecial ontogeny inPulvinula tetraspora, an operculate Discomycete (Pezizales, Pyronemataceae), was followed by correlative light microscopy and scanning electron microscopy. Hymenial development was paragymnohymenial; opening occurred in the prohymenial phase. A functional ascogonium gave rise to ascogenous hyphae which by sympodial and centrifugal growth, produced typical croziers. Developmental aspects of the sterile and fertile portions of the apothecia were described and illustrated.

ISSN:0008-4026    

DOI:10.1139/b78-010

出版商:NRC Research Press    

年代:1978

数据来源: NRC