摘要:

Foliar phenologies of forest understory plants were categorized, and the distribution pattern of leaf habit was examined among different forest environments. Various patterns of foliar phenology were found, especially in herbaceous plants. In addition to the seasonal light regime controlled by the phenology of canopy trees, differences in the length of period with snow cover led to the divergence. Perennial-leaved plants predominate in intensely shaded habitats while annual-leaved plants are more abundant in less shaded habitats. The shade tolerance of perenniel-leaved plants can be considered a preadaptation to snow tolerance. In contrast with the perennial-leaved plants, biennial-leaved plants with leaves overwintering 1 year appear to be favored in euphotic habitats with high insulation both in spring and in autumn. These species are effective competitors in spring because of rapid emergence of current leaves, probably through retranslocation of resources accumulated in the previous year. Another adaptive trait is found in heteroptic plants simultaneously having summer-green leaves and overwintering leaves; these types of leaves seem to function in predictable and quite different environments in a year.Key words: foliar phenology, growth form, light resource, overwintering leaf, snow cover.

ISSN:0008-4026    

DOI:10.1139/b94-055

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

The intrathalline variability of several physical and anatomical parameters of two lichens,Lasallia hispanicaandLasallia pustulatawithin the family Umbilicariaceae, was studied. In each thallus three zones or concentric rings were considered: the central zone, which includes the umbilicus, the intermediate zone, and the marginal zone. The study focussed on the thickness of the thallus and its layers, the increase of surface area and volume with hydration, the sample densities in dry and wet states, several stereological parameters (especially the volume and surface density of both symbionts related to each layer and to the thallus as a whole), and the chlorophyll content. Only slight differences were revealed between the two species, but significant intrathalline variation was observed. A marked decrease in the total chlorophyll content coincided with the thickening of the thallus from the periphery to the centre. The chlorophyll content of individual algal cells, however, presented an inverse gradient. The results suggest that the main role of the dense central zone would be as a water-holding zone while the active growth in the intermediate zone could counteract the continuous erosion of the marginal zone of these umbilicate lichens.Key words:Lasallia, intrathalline variability, mycobiont, photobiont, stereology, thallus density.

ISSN:0008-4026    

DOI:10.1139/b94-056

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Vallisneria americanaMichx. (wild celery), a submerged plant ubiquitous in the fluvial lakes St. Louis and St. Pierre of the St. Lawrence River, Quebec, shows potential as a bioindicator species for trace metals in its environment. The Cd, Cr, Cu, Ni, Pb, and Zn concentrations inV.americanaleaves reflect spatial variations in environmental contamination and represent bioavailable trace metals potentially transferable through the food chain to higher organisms. With the exception of Pb,V.americanaconcentrates trace metals to higher levels in its aboveground tissues than doesPotamogeton richardsonii(A. Bennett) Rydb., another abundant species in the studied lakes, although the two species show the same trend to higher trace metal concentrations at the more contaminated stations.Vallisneria americanafrom Lake St. Pierre shows higher concentrations for all trace metals studied than does the same species from Lake St. Louis (mean concentrations in μg/g dry wt. for Lake St. Pierre versus Lake St. Louis: Cd, 1.62 vs. 0.89; Cr, 3.9 vs. 2.5; Cu, 20.0 vs. 16.5; Ni, 13.1 vs. 5.6; Pb, 3.3 vs. 2.0; Zn, 130 vs. 91). Mean concentrations of Cd, Cr, Ni, and Zn exceed median values of these concentrations for aquatic plants from contaminated sites, as reported in the literature.Key words:Vallisneria americana,Potamogeton richardsonii, bioindicator, trace metals, St. Lawrence River.

ISSN:0008-4026    

DOI:10.1139/b94-057

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Restriction fragment length polymorphism (RFLP) markers were used to study genetic variation in the basidiomycete fungusPhellinus weirii(Murr.) Gilbertson, the cause of laminated root rot of conifers. In an initial study, three isolates each from the Douglas-fir type and the cedar-type biological species were surveyed with 12 restriction enzymes and 20 random, mitochondrial, and nuclear-ribosomal gene probes. The two biological species were distinct with most probe–enzyme combinations (91%). Variation within biological species was detected for the random and ribosomal DNA probes but not for the mitochondrial DNA probes. In a subsequent study 65 probe–enzyme combinations (13 × 5) that had detected variation within the Douglas-fir type biological species were used to analyze 27 isolates derived from six infection centers, two host species, and two geographic areas in western Oregon. Infection centers differed from one another in numerous probe–enzyme combinations but were nearly genetically uniform within. Isolates from the two host species, Douglas-fir (Pseudotsuga menziesii(Mirb.) Franco) and mountain hemlock (Tsuga mertensiana(Bong.) Carr.), showed few RFLP differences. Initiation of infection centers, and subsequent vegetative or basdiospore initiated immigration, appear to be rare events.Key words: ribosomal DNA, mitochondrial DNA, RFLP, root rot, conifer.

ISSN:0008-4026    

DOI:10.1139/b94-058

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

This paper introduces a method for examining the scales of segregation or aggregation of two kinds of plants. It uses the mapped positions of plants but is based on methods originally designed for contiguous quadrat data and may be referred to as two-dimensional local quadrat covariance. A complementary randomization procedure makes it possible to test whether observed aggregation is merely the result of overall patchiness. These methods are applied to analyze the spatial pattern ofSolidago canadensisL. plants in an old hayfield, with and without insect galls. In many of the 12 plots sampled, the galled and nongalled plants were found to be aggregated at scales around 0.7 m. The randomization test showed, however, that this apparent aggregation was often due to the overall patchiness of the plants' dispersion, and that in some cases, within the patchiness the two kinds of plants were actually segregated at a similar scale.Key words: aggregation, galls, patchiness, pattern, scale, segregation,Solidago canadensis.

ISSN:0008-4026    

DOI:10.1139/b94-059

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

A thin layer chromatography bioassay was used to detect antifungal compounds in tissue culture plantlets and potted seedlings of aspen. Catechol and the phenolic glycosides salicin and salicortin were identified as inhibitory compounds; a fourth compound was observed but was not identified. Inhibitory compound levels were estimated in eight tissue culture clones grown on unamended media and media amended with 0.22 M mannitol to induce water stress. Aspen tissue culture plantlets grown under water stress conditions had significantly lower levels of catechol, salicortin, and salicin. Significant clonal variation in levels of catechol, salicin, and the unidentified compound was also observed. Catechol, salicortin, and salicin were inhibitory toHypoxylon mammatumwhen tested at levels similar to those employed in the thin layer chromatography bioassay. These results suggest that a reduction in the levels of inhibitory compounds in water-stressed aspen may be a factor in the water stress induced susceptibility of aspen toH.mammatum.Key words:Populus tremuloides,Hypoxylon mammatum, water stress, tissue culture.

ISSN:0008-4026    

DOI:10.1139/b94-060

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

A single nuclear gene controls nonsporulation in a novel isolate of the Dutch elm disease fungusOphiostoma ulmi(Buism.) Nannf. This has been clearly demonstrated through segregation of the nonsporulating phenotype-in meiotic products recovered from crosses between a mutant nonsporulating isolate (WRB2-1) and wild-type sporulating isolates, between F1progeny and their parents, and between F1progeny. All crosses between nonsporulating and sporulating isolates yielded a 1:1 ratio for these two phenotypes in the meiotic products, whereas all crossings between isolates of the same phenotype produced meiotic products of that phenotype. The genetic stability of the nonsporulating phenotype was clearly shown when no disease symptoms were observed following artificial inoculation of the nonsporulating progeny into white elm,Ulmus americanaL. Exposure to trifluoperazine, a calmodulin inhibitor, did not shift the nonsporulating isolates to the yeast phase, which supports our findings that nonsporulation is under genetic control rather than metabolic control.Key words: nonsporulation,Ophiostoma ulmi, mutant, single nuclear gene, meiotic products.

ISSN:0008-4026    

DOI:10.1139/b94-061

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

The Land Institute is developing perennial grains to be grown in prairie-like mixtures. One approach involves the development of a perennial grain sorghum by crossing tetraploidSorghum bicolorwith wildS.halepenseto combine high seed yield with overwintering ability via rhizome production. We grew tetraploidS.bicolor, F1hybrid (BC0), and two backcross generations (BC1and BC2) in a randomized block design to examine total biomass, seed yield, and allocation to plant parts within and across generations. Root, rhizome, stem and leaf, and total biomass decreased from the BC0to BC2toS.bicolorgenerations, whereas panicle mass, seed mass, and reproductive allocation were lowest in the BC0generation (p < 0.05, ANOVA). Mean seed mass (g ∙ plant−1) was 39.1 in the BC0, 107.3 in the BC1, 84.1 in the BC2, and 92.7 for theS.bicolorparent, which translated into yields of 171.9, 471.6, 396.7, and 407.5 g ∙ m−2, respectively. Reproductive allocation varied from 14.7% in BC0to 28.9% in BC2compared with 33.5% in S.bicolor. Mean allocation to rhizomes was 2.71% in BC0but negligible in BC1and BC2. There was no relationship between rhizome mass and seed mass within any generation, but there was a positive correlation between total plant mass and rhizome mass in BC0. We divided the BC0population into four groups with respect to rhizome production and found no significant differences among the groups in plant size or seed yield. Within each generation, reproductive allocation was inversely related to culm mass. The lack of an apparent trade-off between allocation to rhizome versus allocation to seed within any generation supports the possibility of combining within a population high seed yield and production of perennating belowground organs.Key words: backcross, hybrid, perennial grains, reproductive allocation, rhizome, seed mass,Sorghum bicolor,Sorghum halepe

ISSN:0008-4026    

DOI:10.1139/b94-062

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Seed germination and early seedling growth ofAtriplex griffithiivar.stocksiifrom seeds collected from a saline desert habitat in Karachi, Pakistan, were studied. The seeds ofA.griffithiidid not germinate under high salt stress (516 mM NaCl). Best germination percentages were obtained in distilled water. Seed germination was stimulated in light at cooler alternating temperature (25:10 °C) and inhibited at warmer temperature (30:15, 30:20, and 35:25 °C) regimes. Early seedling growth showed responses towards salinity and temperature that were similar to the germination responses. Both GA3and kinetin alleviated salinity-induced germination inhibition, and in most cases germination was stimulated by growth regulator treatments. A low concentration of kinetin (0.46 μM) and a high concentration of GA3(28.9 μM) significantly promoted early seedling growth at all salinity treatments.Key words:Atriplex griffithiivar.stocksii, seed germination, early seedling growth, salinity, temperature, growth regulators.

ISSN:0008-4026    

DOI:10.1139/b94-063

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Three antibiotic substances strongly inhibitory toPhytophthora capsiciorMagnaporthe griseawere isolated from the broth culture ofStreptomyces violaceonigerstrain A50. A butanol-soluble mixture of antibiotics from the broth were partially purified by XAD-2 column chromatography. The XAD-2 eluates inhibited the mycelial growth ofP.capsiciandM.griseaand the development of Phytophthora blight on pepper (Capsicum annuumL.) plants. The antibiotics were separated by silica gel column chromatography and then purified on a Sephadex LH-20 column to yield three peaks of antifungal activity: SF1A, SF1B, and SF2A. The pure antibiotic SF2A was further purified by preparative HPLC and identified as the pyrrolo[2,3-d]-pyrimidine nucleoside tubercidin based on the UV,1H, and13C NMR spectral data and other chemical evidence. The antibiotic SF2A and authentic tubercidin showed a high antifungal activity against the plant pathogenic fungiP.capsici,Botryosphaeria dothidea, andRhizoctonia solani.Key words:Streptomyces violaceoniger, tubercidin, antifungal activity.

ISSN:0008-4026    

DOI:10.1139/b94-064

出版商:NRC Research Press    

年代:1994

数据来源: NRC