摘要:

The applicability of a model describing the relationship between species richness and standing crop and litter was tested in each of four lakeshore habitats within Wilsons Lake, Nova Scotia. The shapes of the curves describing the species richness – standing crop relationships in the four habitats were significantly different. Standing crop and litter values were positively correlated with measured indices of soil fertility (loss on ignition and silt and clay content) and negatively correlated with disturbance as determined by the location of the shrub zone and overwinter damage to wooden pegs. Sites with high standing crop had a lower proportion of biomass composed of evergreen and isoetid species than the proportion in sites where standing crop was low. The among habitat variation observed in this study, and the variation in published values of standing crop values yielding maximum species richness, limit the accuracy of predictions from this model. Steps for refinement are suggested.

ISSN:0008-4026    

DOI:10.1139/b89-203

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Seedlings of six outcrossed jack pine (Pinus banksianaLamb.) families from a diallel cross of jack pine were mainly larger than those of three selfed families at the time they were transplanted to the field in Ontario. Outcrossed families also exhibited a greater absolute and relative (percent) growth in total dry matter at the end of the first growing season. Outcrossed families exhibited a higher net photosynthesis, a lower transpiration rate, and a higher water use efficiency on hot, but not mild, days in mid-August. Stomatal conductance, transpiration rate, and net photosynthesis were greater in outcrossed families in September. There were significant, positive correlations between stomatal conductance, transpiration rate, and shoot and root growth in August and September. The results suggest that maintenance of a higher stomatal conductance and net photosynthesis until late in the growing season may contribute to the faster growth rates observed in outcrossed families.

ISSN:0008-4026    

DOI:10.1139/b89-204

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Terminal meristem ontogeny of matureFraxinus pennsylvanicavar.subintegerrima(Vahl) Fern, (green ash) was investigated by bud dissection, histological analysis, and scanning electron microscopy. The shoots were completely preformed and bud-scale initiation for the next bud began in the spring shortly before any visible sign of swell. Foliage-leaf initiation began in May and ceased in late June or early July, but there were certain differences in primordium production patterns between the two trees investigated and between the years of the study. Although temperature, as measured by heat-unit accumulation, played a significant role in the onset of shoot expansion and primordium initiation, its importance in controlling these processes diminished as the season progressed. Buds formed in the axil of every leaf primordium, but those in the axils of scales remained small. There was evidence of axillary bud initiation as early as the P1, stage. By P2or P3there was a clearly discernable shell zone of elongated cells. Such cells had relatively large vacuoles concentrated at each end, in contrast with the essentially nonvacuolate cells of the incipient bud meristem. In the terminal resting bud, there were well-developed scale-axil buds and protruding axillary meristems associated with foliage-leaf primordia.

ISSN:0008-4026    

DOI:10.1139/b89-205

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Possible phytogeographic boundaries within the Gulf of St. Lawrence region are examined using the moss floras of 29 smaller geographic units. Principal coordinates analysis (PCoA) shows floristic change in the Gulf to be gradual and to follow two major gradients, a north–south gradient and an east–west gradient. These are positively correlated to the distributions of temperate and arctic species, respectively. PCoA ordinations also show no evidence of distinct boundaries between adjacent units, but indicate that Cape Breton Island and Gaspé Peninsula have floras of intermediate composition to those of the Maritimes and Newfoundland. Randomly generating floras for adjacent units using Monte Carlo simulation supports the results obtained from PCoA. The real Jaccard similarities between adjacent units are found to be greater than those expected from simulation. The lack of distinct boundaries in the Gulf of St. Lawrence region is attributed to the high diversity of species distributions possible in a region with complex environmental gradients.

ISSN:0008-4026    

DOI:10.1139/b89-206

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Haptoglossa intermediasp.nov., recovered from woodland soil, is described as a new endoparasite of rotifers. The species is distinguished from others by the shape and size of the gun cell, the fusiform infection sporidia, and the shape of the thalli. This species, along withH.zoospora,H.mirabilis, andH.humicola, can attack and complete its life cycle on both rotifers and nematodes. Tardigrades (water bears) may be alternative hosts forHaptoglossaspecies.

ISSN:0008-4026    

DOI:10.1139/b89-207

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Twenty chrysophycean stomatocysts were described from the postglacial sediments of a Mid Arctic lake (Tasikutaaq Lake, Baffin Island, N.W.T.). The description guidelines of the International Statospore Working Group were followed. Elements of both High Arctic and temperate cyst floras were present, and approximately one-third of the cysts were described as new. Stomatocyst degradation was common and may be related to the degree of ice cover on the lake.

ISSN:0008-4026    

DOI:10.1139/b89-208

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Resting spores ofErynia radicansgerminate after storage for over 2 months at 4 °C or by natural overwintering. Percent germination increases with spore age to a maximum of 77% after 8 months at4 °C. During this period, the temperature limits for germination changed from 8–20 °C at 3 months to 4–32 °C after 8 months at 4 °C. Germination time (mean and variance) decreases with spore age. Maximum percent germination and mean germination time decrease as poststorage temperature increases. Variance is stable from 12 to 20 °C, but increases at poststorage temperature extremes. No differences in mean germination time were found in isolates, although differences in maximum percent germination and variance in mean germination time were observed. The resting spore population responses to temperature during storage (overwintering) and at post-storage temperatures (spring and summer) act to synchronize the presence of an active inoculum with that of the insect host when conidia are most infective. Entomophthorales mycosis and epizootics occur during fifth and sixth larval instars ofChoristoneura fumiferana. The timing of events in the life cycle of entomophthoralean fungi with respect to that of host populations is discussed for the spruce budworm,E.radicans, and other fungal parasite – insect systems.

ISSN:0008-4026    

DOI:10.1139/b89-209

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

In developing leaflets ofStylosanthes guianensis(Aubl.) Sw., twin prismatic calcium oxalate crystals form in adaxial and abaxial epidermal crystal idioblasts. These cells eventually die and collapse, leaving the crystals embedded in a matrix of cutin and cell-wall materials. Adaxial crystal idioblasts develop above large conical cells that, in turn, are interspersed among smaller, multiple-layered palisade parenchyma. Abaxial crystal idioblasts develop beneath a uniseriate layer of large horizontally branched cells abutting the abaxial epidermis. Spongy parenchyma occupies the middle mesophyll above the layer of branched cells. The abaxial crystals and the branched cells of the lowermost mesophyll develop simultaneously. Adaxial crystals and the conical cells develop later and in conjunction with each other. In mature leaflets, the adaxial and abaxial crystals and their associated collapsed crystal idioblasts form networks, the interstices of which are occupied by either single stomates and accompanying epidermal cells (adaxial) or clusters of stomates and accompanying epidermal cells (abaxial). Epidermal crystals are known from other Leguminosae; however, to our knowledge this is the first report where epidermal crystal development involving cell death and collapse is correlated with two types of specialized mesophyll cells.

ISSN:0008-4026    

DOI:10.1139/b89-210

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

In the wheat plants infected with dwarf bunt, sporulation occurs only in developing kernels. The dikaryon was isolated from infected kernels and from the rachis of infected spikes. The development of pathogenic hyphae and teliosporogenesis in vivo and in vitro is described. Ultrastructural studies indicated that in vivo teliospore primordia detach from sporogenous hyphae in the hymenium layer and develop into mature teliospores. Teliospores were borne terminally on sporogenous hyphae in vitro. Substances that stimulate hyphal branching and inhibit teliospore formation of the dikaryon were isolated from vegetative wheat tissues but not from bunt-infected spikes containing the sporulating dikaryon. The dikaryon resumed sporulation only when transferred to rich nutrient media without extracts. Extracts from infected wheat spikes containing the sporulating dikaryon induced the vegetative dikaryon to sporulate. The bioregulators involved in these phenomena were not identified. Bioactive extracts had no apparent effect on the growth of the monokaryon. A fluorochrome, mithramycin, was used to detect nuclei in monokaryotic and dikaryotic hyphae. New approaches to bunt control are discussed.Key words:Tilletia caries,Tilletia controversa, monokaryon, teliospores, bioregulators.

ISSN:0008-4026    

DOI:10.1139/b89-211

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Organic solute concentrations of five hybrid poplar cultivars were compared to determine the relationship between water-stress tolerance, tissue solute concentration, and growth rate under field conditions. In the expanding foliage of the faster growingPopulus deltoidesBartr. ×P.balsamiferaL. (Jackii 4), the saturated osmotic potential and turgor loss point osmotic potential were 0.18 MPa and 0.47 MPa lower, respectively, than in the slower growingP.deltoides×P.balsamifera(Jackii 7). The expanding foliage of Jackii 4 had higher (ca. 50%) concentrations of organic solutes, attributable mainly to salicyl alcohol, salicin, sucrose, and an unidentified compound. The coupling of high productivity and stress tolerance in Jackii 4 suggests that these may be compatible rather than competing attributes. Water-stress studies onP.deltoidesBartr. ×P.nigraL. (DN 22) under greenhouse conditions demonstrated that stressed trees accumulated 4 times the soluble sugar concentrations of well-watered trees, lowering the saturated osmotic potential by 0.55 MPa and turgor loss point osmotic potential by 1.0 MPa. Leaves were the primary site of osmotic adjustment to water stress and roots showed no adjustment. The use of repeated drying cycles in planting stock may aid survival of postplanting stress in species capable of osmotic adjustment. The relationship between stress tolerance and solute concentrations in the greenhouse water-stress study paralleled that of the field study.

ISSN:0008-4026    

DOI:10.1139/b89-212

出版商:NRC Research Press    

年代:1989

数据来源: NRC