摘要:

A 3-min pulse of11CO2was fed to leaves of various plant species to allow us to compare the patterns of movement of11C translocate over 90 min. Three groups of profiles were found. (1) InHelianthus, Nymphoides, Tropaeolum, Ipomoea, andFraxinus, a mass flow passed successive detectors, rising steadily over a 90-min period. (2) InZeaandTriticum, the mass flow remained at a peak for 5–10 min and fell steadily thereafter. (3) InPiceaandPinus, no obvious mass-flow pattern was detected in 90 min but rather a series of waves or packets. In every case, the activity opposite certain positions accumulated faster than others, suggesting that points of local buildup of translocate occur along a stem or petiole.By using high activity11CO2counting times of 5 s or 1 s, and the five-point mean technique of analysis of data, we have been able to detect aberrations in the tracer profile opposite each detector. These aberrations are due in part to the movement of tracer at different speeds in parallel veins, in part to the superposition of reverse flow of tracer, and in part to apparent discontinuities of flow or small waves of tracer. We conclude that some pulsatory sucrose loading mechanism is possible in the leaves, but a nonsteady-state translocatory mechanism is also possible. We have developed techniques for detecting the points of time of the onset of mass flow and the method of following small peaks of tracer activity past successive detectors. Waves of translocate moved at 0.2 cm min−1in pine and spruce and 0.5–10 cm min−1in ash and the angiosperms. Some synchrony of flow causes activity reinforcement or interference to occur in transient fashion.

ISSN:0008-4026    

DOI:10.1139/b79-106

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Chromosome numbers are reported for 88 accessions of grasses from western Zaïre belonging to 31 genera and 65 species. First chromosome counts are reported for the generaParatheria, Robynsiochloa, andYstiaand for the following species:Phragmites mauritianus, Sporobolus congoensis, Sporobolus sanguineus, Brachiaria kotschyana. Digitaria polybotrya, Entolasia oliracea, Panicum brazzavillense, Panicum spongiosum, Paratheria prostrata, Setaria thollonii, Andropogon brazzae, Andropogon patris, Robynsiochloa purpurascens, Schizachyrium platyphyllutn, Schizachyrium thollonii, andYstia stagnina. Chromosome numbers that differ from previously reported records are given forSporobolus festivus, Digitaria diagonalisvar.hirsuta, Digitaria longiflora, Panicum griffonii, Panicum sadinii, andRhynchelytrum repens.

ISSN:0008-4026    

DOI:10.1139/b79-107

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The annual smartweedsPolygonum lapathifoliumL.,P. pensylvanicumL., andP. persicariaL. are weeds of cereal crops, waste places, and wet ground in Canada. Their ‘weediness’ is attributed, in part, to the production of large numbers of achenes which are capable of lying dormant in the soil for several years or until suitable conditions arise for germination.Dormancy–germination characteristics of achenes from Ontario plants were examined in the laboratory and in the field. Three types of dormancy have been identified, each of which prevents germination under a different set of unfavourable conditions. An innate dormancy prevents germination in fresh achenes immediately prior to winter. An enforced dormancy prevents germination during the winter and in achenes which are deep in the soil. An induced dormancy is caused by hot or dry periods (at least inP. persicaria). Germination occurs as a series of flushes whenever achenes are brought to the soil surface and (or) whenever rainy spells occur.

ISSN:0008-4026    

DOI:10.1139/b79-108

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

A newHarposporiumis described which produces branching chains of arthroconidia at the apex of phialide-bearing conidiophores. Phialoconidia are crescent shaped in lactophenol but tend to coil to form part of a helix in water. Phialoconidia are very variable in size and have a mucoid secretion at the proximal end. Arthroconidia germinate in the presence of nematodes to produce phialoconidia from short, cylindrical conidiogenous cells. Infection of a nematode host is initiated by lodging of a phialoconidium in the oesophagus.

ISSN:0008-4026    

DOI:10.1139/b79-109

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The large kelpMacrocystis integrifoliaandNereocystis luetkeanaoff the coast of British Columbia have light saturation points at about 200 foot candles (1 foot candle = 10.76391 lx); however, photosynthetic rates remain unimpeded through mugh higher light intensities, up to 7000 foot candles. Short-term labelling experiments indicate that the Calvin cycle is operational in these plants, but, in addition, and particularly in the young growing parts, relatively high activities of phosphoenolpyruvate carboxykinase (PEP-CK)and correspondingly high rates of14C fixation in the dark are observed. In older, mature parts, the activity of PEP-CK as well as the ability for light-independent14C assimilation are lower. These observations are supported by data from a variety of other Pacific Laminariales. Pulse–chase experiments in the light and in the dark reveal characteristic differences between young and mature parts of the fronds: apart from qualitative difference in the soluble fraction of assimilates, the young parts show a significantly large proportion of radiocarbon confined to the ethanol-insoluble fraction.

ISSN:0008-4026    

DOI:10.1139/b79-110

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Papillae were deposited in barley epidermal cells directly beneath appressoria ofErysiphe graminisf. sp.hordeiand appeared as hemispherical, internal wall appositions. The papilla response began shortly after the formation of a rapidly moving cytoplasmic aggregate beneath the appressorium. As documented in coleoptile tissue by time-lapse light microcinematography, the papillae grew rapidly for 20–30 min after becoming visible, their radii increasing by 0.1 μm/min. For small papillae, deposition continued for about 30 min; for larger papillae, deposition continued for 120–180 min. Results with transmission electron microscopy on leaf epidermal cells suggested that papilla deposition by host cytoplasmic aggregates can be divided into four sequential stages: (i) the deposition of osmiophilic (lipidic) materials, (ii) the deposition and partial compaction of nonosmiophilic, amorphous material (probably insoluble polysaccharides), (iii) compaction of nonosmiophilic, amorphous material, and (iv) the incorporation of osmiophilic material into the host wall and into the compacted nonosmiophilic, amorphous material. At maturity, the papillae are hardened, electron-opaque wall appositions that may be effective in preventing fungal penetration and development. Failure of papillae to prevent fungal penetration and development may be related to the inability of the epidermal cells to complete the entire sequence of events in papilla deposition before attempted fungal penetration.

ISSN:0008-4026    

DOI:10.1139/b79-111

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Patterns of bryophyte community characteristics, including absolute cover and alpha diversity, and the response patterns of important bryophyte species are described in relation to complex gradients of elevation and moisture in the Canadian Rocky Mountains east of the Continental Divide. Thirty stands including grasslands, wetlands, forests, rock outcrops, and tundra were quantitatively sampled for bryophytes using 50 10 × 100 cm quadrats in larger 10 × 50 m macroplots. Direct gradient analysis, using elevation as the first axis and synthetic moisture index derived from moisture indicator values of vascular species as the second axis, was used to depict the similarity relationships among stands and the response patterns of bryophyte communities and species. Bryophyte community cover is low in xeric sites and high in mesic and hygric sites, reaching a maximum of 70% inPieea engelmannii – Abies lasioearpaforests of the subalpine zone. Bryophyte species richness of stands is positively correlated with the number of substratum types per stand; on the most abundant substratum per stand, it is positively correlated with elevation. Habitat breadth and overlap were measured for important species. Most species habitats are narrow along the moisture gradient and broad along the elevation gradient. Species with similar habitats are usually different in their substratum affinities, but notable exceptions occur.

ISSN:0008-4026    

DOI:10.1139/b79-112

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The aqueous extract of air-dried roots ofBoerhaavia diffusashows broad-spectrum antiviral activity and no phytoxic effects. Infection by four viruses was completely prevented, at treated and nontreated sites, when the extract was applied on two basal leaves of host plants 24 h prior to virus inoculation. This inhibition was completely reversed by the application of actinomycin D on treated leaves within 6 h of extract treatment and partially reversed within 18 h. The crude extract from resistant leaves contained an inhibitor of virus infection.The inhibitor in the root extract was partially active up to a dilution of 1:500, was completely inactivated at 95 °C for 10 min, and survived at room temperature for 20 days. The expression of inhibitory activity was prevented when the treated plants were exposed to temperatures beyond 35 °C. The inhibitory principle in the extract was nondialyzable and insoluble in organic solvents, viz., petroleum ether, solvent ether, chloroform, and benzene. It was adsorbed by animal charcoal, wood charcoal, and celite, and was precipitated by ammonium sulphate (90%), ethanol (50%), and cold trichloroacetic acid (10%). The inhibitor was not sedimented at 120 000 × g for 120 min. Further characterization is being done for positive identification of the inhibitor.

ISSN:0008-4026    

DOI:10.1139/b79-113

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

In a 20-year-old abandoned surface coal mining area in eastern Ohio, concentrations of B, Sr, and Ba were determined for plant species commonly found in strip-mined and unstripped habitats. Where significant differences between elemental values of plants from strip-mined and unstripped habitats were observed, species from strip-mined areas exhibited higher values of B and lower values of Sr and Ba.Element loss during the 1st year of leaf litter decomposition was determined for leaves of 10 dominant tree species collected in the study area in late October 1975. Loss of boron was found to be greatest during the 1st year of leaf litter decomposition, followed by that of strontium. Some litter types exhibited accumulation of Ba during litter decomposition, whereas other types exhibited slight losses of Ba after 12 months.Leaching experiments using ovendried leaves and acidified distilled water to simulate rainfall revealed that boron was readily leached from all leaves studied except those ofFraxinus americana. A significant correlation was observed between amounts of B remaining after leaching and amounts remaining after 12 months of litter decomposition, which indicated that B loss during this interval was due to leaching losses. Strontium and barium exhibited little mobility as a result of leaching.Strip mining results in edaphic changes with concomitant increases in plant accumulation of boron. However, rapid losses of boron from decomposing leaf litter result in little accumulation of boron in litter with time.

ISSN:0008-4026    

DOI:10.1139/b79-114

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Xylaria magnoliaesp. nov. is described from fruits ofMagnoliaspecies from eastern United States.Xylaria magnoliae, formerly considered to beX. ianthino-velutina, is compared and contrasted with that species and withX. carpophila, X. culleniae, andX. persicaria.

ISSN:0008-4026    

DOI:10.1139/b79-115

出版商:NRC Research Press    

年代:1979

数据来源: NRC