摘要:

The dimension of soil augers needed to sample a seed bank ofChenopodiumspp. (lamb's-quarters) was determined by randomly sampling a 1.35-ha area within a cornfield in Oxford County, Ontario. Sampling units of three different auger sizes (1.9, 2.7, and 3.3 cm in diameter) were collected. On a per volume basis, there were no significant differences between the three sizes of auger in estimating the number of lamb's-quarters seeds in the soil. Three sampling methods, systematic, stratified random, and cluster, were compared with random sampling in their capacity to minimize the sampling variance. Soil cores of 1.9 cm diameter and 15 cm deep were taken systematically at 3.5-m intervals to form a 32 × 32 matrix. Repeated sampling within the matrix using Monte Carlo techniques indicated that the estimate of sampling variance decreased with increasing sample size, regardless of the sampling method used. No fewer than 60 sampling units should be collected to quantify the seed bank of an abundant weed such as lamb's-quarters. The estimates of sampling variance of systematic and cluster sampling were clearly influenced by the sampling interval and the cluster's shape, respectively. This was attributed to the underlying seed distribution of lamb's-quarters in the soil that was clustered with patterns of high and low seed density parallel to corn rows. There were no significant differences between the estimate of sampling variance of random and stratified random sampling with a fixed sample size of 64 units.

ISSN:0008-4026    

DOI:10.1139/b89-364

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

The soybean ovule is bitegmic with the megasporocyte three to four cell layers beneath the nucellar epidermis. The megasporocyte is much larger than the surrounding nucellar cells, is connected to the nucellus by plasmodesmata, and at this stage exhibits a cytoplasmic density comparable with cells of the nucellus. After meiosis, the chalazal megaspore becomes functional in megagametogenesis. It alone retains plasmodesmatal connections to the nucellus. Chalazal megaspore expansion is accompanied by development of many small vacuoles having a uniform distribution. The first megaspore mitosis results in two nuclei lying on an axis parallel to the longitudinal axis of the embryo sac. Ultimately, these two nuclei are separated by a large vacuole. Numerous Golgi vesicles and proteinlike bodies are observed along the periphery of vacuoles in the 1-, 2-, and 4-nucleate embryo sacs. As the contents of vesicles and proteinlike bodies are observed deposited in vacuoles, it is probable that they both add osmotica to the vacuoles, thus promoting a water flux. We believe that the production of Golgi vesicles and putative protein bodies may be important in the formation and expansion of the large vacuole that appears to drive embryo sac expansion during early megagametogenesis in soybean. It is also believed that the timing to this vacuole's development has important developmental consequences.

ISSN:0008-4026    

DOI:10.1139/b89-365

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Electrophoretic analysis of sorghum (Sorghum bicolor(L.) Moench) seed prolamines in the presence of sodium dodecyl sulfate reveals major proteins of 27 and 25 kDa and two other proteins of 18 and 12 kDa. Antibodies were raised against this prolamine fraction and used to examine the subcellular distribution of the proteins in developing sorghum seeds. Protein bodies in the starchy endosperm and subaleurone cells usually are round in cross section and contain darkly staining materials arranged in concentric rings. Protein bodies in the first two layers beneath the aleurone layer are irregular in shape and contain discrete pockets of light and dark staining inclusions. Prolamines were detected in both types of protein bodies by immunolabeling. Other oganelles, including Golgi complexes, mitochondria, and amyloplasts, were not labeled. The protein bodies, which have ribosomes attached to their surfaces, are directly connected to the rough endoplasmic reticulum. In some instances, this endoplasmic reticulum was specifically labeled with protein A – gold particles. Based on these observations, we suggest that the rough endoplasmic reticulum serves as the site of both synthesis and accumulation of sorghum prolamines.

ISSN:0008-4026    

DOI:10.1139/b89-366

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Two life histories have been established forRhodophysema elegansfrom the North Atlantic Ocean by field and culture studies. These are entirely distinct and occur, respectively, in (i) sexual, tetrasporangial and (ii) asexual, bisporangial populations. In tetrasporangial isolates, a sexual life history was unequivocally indicated by chromosome numbers ofn = 18 in vegetative cells and 18 pairs during meiotic tetrasporocyte division. Bisporangial plants, interpreted as polyploid gametophytes (2x = 36), undergo a direct, mitotic bispore to bisporophyte life history and also produce diploid spermatia. The sexual life history in North AtlanticR.elegansdiffered in several respects from that reported in a Californian isolate. A taxonomic study of crustoseRhodophysemaspecies from the Pacific Ocean in comparison with type material ofR.elegansfrom France indicated that two entities have been reported from Pacific North America under this name, but neither corresponds with the type. (i) Crusts epiphytic on the seagrassPhyllospadixand algal fronds are identified asRhodophysema odonthaliae, described from Japan. Evidence of both sexual and direct, mitotic tetrasporangial life histories has been observed in field collections of this species, (ii) Larger plants, with much larger spermatangia, collected on pebbles and brown algal stipes are considered as being growth forms of the monostromatic Californian speciesRhodophysema minus.

ISSN:0008-4026    

DOI:10.1139/b89-367

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Seedlings ofGymnostoma papuanum(Casuarinaceae) andShepherdia argentea(Elaeagnaceae) were grown in water culture and inoculated withFrankiastrain HFPGpI1. Root nodule initiation and early nodule development were examined using light microscopy.Gymnostoma papuanumwas infected by penetration ofFrankiainto deformed root hairs, followed by development of a prenodule region and one to several nodule lobe primordia in the root cortex.Frankiahyphae grew directly through cell walls from cell to cell, colonizing cells of the prenodule prior to invading nodule lobe cells.Shepherdia argentearoots were infected byFrankiavia intercellular penetration of the root epidermis and cortex with direct infection of cells of the nodule lobe primordia. No prenodule region was formed. Thus far, the mode of infection appears to be characteristic for each of the plant families. Subsequent to nodule initiation, plants were assayed at 4-week intervals (up to 12 or 16 weeks) for acetylene reduction activity. Low and variable activity was observed. The presence of symbiotic vesicles inG.papuanumnodules is reported as the first instance of vesicles seen in nodules taken from a member of the family Casuarinaceae.

ISSN:0008-4026    

DOI:10.1139/b89-368

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

The partitioning of dry matter and nutrients into component plant parts was determined for a weedy population of Jerusalem artichoke (Helianthus tuberosusL.). The annual allocation pattern, studied over two growing seasons, was characterized by a relatively large distribution of energy to structural increases in height, leaf number, and lateral spread. Biomass and nutrient allocation to clonal growth (rhizomes and tubers) was much greater than to reproductive organs (flowers and seeds). Reproductive and clonal allocation of nutrients showed a different pattern than allocation of biomass. Plants severely defoliated by hail in 1984 redistributed available nutrients and generated new leaves. Although rhizome and tuber size and number were reduced after the hail storm, the overall strategy of Jerusalem artichoke appears to involve a constancy of nutrient allocation to clonal structures. In contrast with previous reports for cultivated populations of Jerusalem artichoke, we found that the leaves, not the stem, constituted the primary temporary sink for assimilates that were later distributed to developing rhizomes and tubers.

ISSN:0008-4026    

DOI:10.1139/b89-369

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

The pathways of glucose catabolism were examined in aB.cinereastrain isolated from grape. Respirometric and enzymatic studies indicated that this plant parasite catabolized glucose through the Embden–Meyerhof and hexose monophosphate shunt pathways. Data also suggested functioning of an active tricarboxylic acid cycle and presence of the glyoxylate cycle. Direct oxidation of glucose by means of glucose oxidase led to gluconic acid accumulation in the medium during the stationary phase of growth. Part of the glucose oxidase was extracellular and could have technological consequences in wine making.

ISSN:0008-4026    

DOI:10.1139/b89-370

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Isozyme electrophoresis has potential for assisting in cultivar identification of the grape (Vitis). However, past studies have suffered from problems with extraction and resolution of enzymes because of high tannin concentrations in the tissues. In addition, many extraction procedures require expensive, elaborate, and time-consuming protocols. A practical and inexpensive procedure that allows for rapid extraction and the resolution of a large suite of enzymes is presented. Using our procedure, 40 enzymes were tested for their resolvability on numerous gel buffer systems and their usefulness for discriminating cultivars. Fourteen of the enzymes we tested were consistently resolvable and showed variation among cultivars on three gel–electrode buffer systems.

ISSN:0008-4026    

DOI:10.1139/b89-371

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Lodgepole pine (Pinus contortaLoudon) and white spruce (Picea glauca(Moench) Voss) seedlings were grown at three densities (900, 2200, and 4000 stems/m2) in fertilized and unfertilized soil. Pine was grown for 111 days and spruce for 120 days. For both the pine and spruce, the mean weight of shoots, roots, and total plant was significantly greater and the root to shoot ratio was lowest in the fertilized and low density treatments. For the spruce, the fertilized treatment had significantly higher size inequality (as measured by the Gini coefficient) for shoot, root, and total mass. For lodgepole pine, only the inequality in root size was greater with fertilization. For the spruce, inequality in shoot, root, and total mass was lowest in the high-density conditions. In the pine, there was little relationship between size inequality and stem density. Compared with the spruce, the pine had greater biomass allocation to roots in poor growing conditions.

ISSN:0008-4026    

DOI:10.1139/b89-372

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Field experiments and survey methods were used to assess competition and interaction betweenLemna minorL. andLemna trisulcaL. at Delta Marsh, Manitoba. Sites were dominated by one or the other species or codominated by both. Replacement series experiments predicted codominance ofL.minorandL.trisulcain an unshaded eutrophic site but predictedL.minordominance when run for a longer time. Similar experiments conducted in a shaded eutrophic site predictedL.minordominance. Addition series experiments showed that intraspecific and interspecific competition occurred in the unshaded site. In a eutrophic unshaded ditch, high densities ofL.minorsuppressedL.trisulca. In a eutrophic shaded site, high densities ofL.minorand green algae inhibitedL.trisulca, and in a sunny, less eutrophic site high density of each species inhibited the other. In a transplant experiment,L.minorbiomass in shaded enclosures approached that found naturally in two shaded sites.Lemna trisulcapersisted when shaded. Vegetative biomass trends in an unshaded eutrophic marsh ditch indicated spring and fallL.trisulcadominance and summerL.minordominance. Shaded eutrophic sites were dominated byL.minor, whereas a less eutrophic site was dominated byL.trisulca. A model is developed to explain dominance patterns, and seasonal life-history responses are considered.Key words:Lemna, duckweed, competition, interaction, resources, light, nutrients.

ISSN:0008-4026    

DOI:10.1139/b89-373

出版商:NRC Research Press    

年代:1989

数据来源: NRC