摘要:

The variation of 52 morphological and anatomical characters was analysed in 32 populationsof Festuca rubraL.sensu latofrom salt marshes, coastal rocks, coastal sands, and anthropogenic sites in eastern Quebec. The results show that the variation of characters is essentially continuous within and between populations, that some populations are much more variable than others, and that on the whole, character variation patterns are mainly related to ecological rather than geographical factors. The weak structure revealed by a similarity analysis of populations is the source of the classification problems within this species.

ISSN:0008-4026    

DOI:10.1139/b87-148

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Two-dimensional electrophoretograms of detergent-soluble polypeptides extracted from dormant urediospores were used to compare interspecific and intraspecific relationships among nine races of rye stem rust (Puccinia graminisf.sp.secalis) and a hybrid between rye stem rust and wheat stem rust (P.graminisf.sp.tritici) and its parents. More than 280 polypeptides were detected in each race of rye stem rust. The nine races differed by one to five genes for virulence and by five to seven polypeptides, but these differences were not correlated. The rye–wheat stem rust hybrid, rye stem rust parent, and wheat stem rust parent differed by 12 polypeptides. The polypeptide patterns of the rye stem rust races were similar to those previously found for wheat and oat stem rusts. Rye stem rust and wheat stem rust had 270 polypeptides in common and differed by 17 polypeptides. In contrast, 92 polypeptides separated rye and oat stem rusts. The considerable homology in polypeptide patterns is consistent with the view that these three cereal stem rusts are related and that rye stem rust and wheat stem rust have the closest genetic relationship.

ISSN:0008-4026    

DOI:10.1139/b87-149

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

The role and regulation of proteolytic enzymes in protein mobilization from seed storage tissues is not fully understood. Surgical removal of the shoots of 5-day-old pea seedlings was found to double the longevity of the cotyledons remaining attached to the roots. Despite the healthy appearance of these cotyledons (green, turgid), their protein content decreased rapidly. After 14 days of seedling growth, the protein level decreased, but remained about 3 to 4 times greater than the amount present in normally senescing cotyledons of untreated seedlings. Specific differences in the cotyledonary albumin and globulin complement of 14-day-old de-shooted and control seedlings were revealed by electrophoresis. Proteolytic (casein degrading) activity was present in dry and senescing cotyledons. The need to purify this enzyme prior to a further characterization of its role in the senescence of cotyledons was demonstrated.

ISSN:0008-4026    

DOI:10.1139/b87-150

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

The mating system in five northern Ontario populations of tamarack (Larix laricina(Du Roi) K. Koch) was investigated using five allozyme marker loci (Aat3,G6p,Mdh3,Pgi2, and6pg2). The mean multilocus outcrossing rate was 0.729, lower than estimates reported for most other conifers. The one population with a much higher stand density than the others had the highest outcrossing rate (0.908). Significant heterozygote deficiencies, relative to Hardy – Weinberg expectations, were observed at most loci in all five embryo populations. In contrast, there appeared to be few cases of heterozygote deficiencies in the adult populations, indicating that many inbred seedlings do not survive to the adult stage.

ISSN:0008-4026    

DOI:10.1139/b87-151

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Seed dispersal, predispersal and postdispersal seed predation, seed dormancy, and germination were followed for four cone-bearing eastern red cedar trees (Juniperus virginianaL.), a predominantly avian-dispersed plant species, in pastures in southwest Virginia from June 1981 through May 1982. Within 12 m from the source trees, 34.7% of the total cone crop was recovered. Recovered material consisted of unripe cones, ripe cones, parasitized cones, and pulpless seeds evacuated by birds, averaging 17.9, 11.6, 1.0, and 4.2%, respectively, of the cone crop. Predispersal avian predation of seeds accounted for 3.1% of the cone crop. After 1 year 0.9% of the cones remained on the trees. The remaining 61.3% of the cone crop was dispersed at least 12 m from the source trees. Less than 3% of the cone crop is likely to germinate within 12 m of the source trees, while about 25% is likely to germinate at greater distances. Red cedar seeds passed unharmed through the digestive tract of avian dispersers and showed greater total germination than manually depulped seeds. Red cedar seed banks were not found under a chronosequence of red cedar stands; seeds generally lost their viability within one growing season. Seed shadows decreased exponentially with distance from cone-bearing trees. A similar distribution function was reflected in the spatial distribution of red cedar cohorts colonizing pastures near source trees. The large cone crop, diverse avian disperser assemblage, physiological adaptation of red cedar to open, xeric sites, and availability of seed sources in fence rows contribute to the successful invasion of pastures by this species.

ISSN:0008-4026    

DOI:10.1139/b87-152

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Growth and development of two closely related rust fungi,Uromyces appendiculatusandU.vignae(uredospore infections), were compared in several American and African species of thePhaseolus–Vignaplant complex and inLablab purpureus. In plants inoculated withU.appendiculatusthe frequency of formation of both primary and secondary haustoria generally decreased with evolutionary distance from the American host species.Uromyces appendiculatusformed primary haustoria at a high frequency of infection sites in most American and many African species, and also sustained a limited haustorium – plant cell metabolic relationship (as determined by the amount of secondary fungal growth) in one group of African species.Uromyces vignaegenerally formed very few haustoria in both American and African species not known as hosts of the fungus; however, growth ofU.vignaecolonies occasionally continued for some time at a few infection sites in nonhost species without sporulation. The implications of these results are discussed with respect to the coevolution of the two fungi with their hosts.

ISSN:0008-4026    

DOI:10.1139/b87-153

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

The distribution of starch granules between infected and uninfected cells in the central and cortical regions of alfalfa (Medicago sativaL.) nodules was investigated by morphometry of light micrographs of semithin sections of resin-embedded specimens. Nodules were collected from greenhouse-grown plants at early anthesis. The influences of symbiotic development on starch granule distribution were also investigated. In the early infection zone, infected cells had 1.7 times more starch granules and 1.5 times more starch per cell than uninfected cells. In the middle and late infection zones no significant differences in granule numbers or starch per cell occurred between cell types. Uninfected cells had greater starch density and smaller cell size than infected cells. Starch quantity and density in both cell types decreased from early infection to onset of senescence, with infected cells losing starch more rapidly. Comparisons between nodules from plants placed in darkness for 48 h and nodules from plants grown in light–dark cycles showed that starch depletion (starch area per cell and starch density) occurs more rapidly in infected cells than in uninfected cells. We conclude (i) that starch metabolism does not occur exclusively or even primarily in one cell type and (ii) that during prolonged periods of reduced photosynthesis infected cells deplete starch reserves faster than uninfected cells.

ISSN:0008-4026    

DOI:10.1139/b87-154

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

A model is developed to study the dynamics of carbon and nitrogen in decomposing substrates that contain different organic compounds: (i) lignin, (ii) carbohydrates "masked" by lignin compounds, and (iii) free carbohydrates. Under conditions both of carbon limitation and of nitrogen limitation the model predicts a negative linear relationship between lignin concentration and rate of mass loss. The coefficients of this relationship are determined by microbial properties and by the ratio (ac) between the amount of "masked" carbohydrates and the amount of lignin in the litter. Litter decomposition data of three different ecosystems are used to obtain estimates of the ratioac. The calculated values are in the same range as values estimated on the basis of the course of the cellulose/lignin ratio during the decomposition process. When nitrogen limits microbial growth, the model predicts a positive linear relationship between rate of mass loss and initial lignin concentration.

ISSN:0008-4026    

DOI:10.1139/b87-155

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Direct and indirect effects of acidic precipitation on the rates of CO2exchange of bean plants (Phaseolus vulgarisL., cv. Tendergreen) were measured. Solutions of HCl, HNO3, H2SO4, and artificial acid rain at pH values from 2.7 to 5.0 sprayed on leaves at intervals (varying from 1 to 5 days in different experiments) for 3 weeks had no effect on rates of CO2exchange. Some lesions appeared on leaves where chlorophyll was destroyed; apparently undamaged areas of the leaf compensated by increasing the rate of photosynthesis. Application of acidic solutions to pot soil in which the plants were growing or growing plants in nutrient solutions at pH 3.0 caused serious effects in the leaves, resembling Ca or Mg deficiency symptoms, but no obvious deleterious effects to the roots. Effects of acid were greater when Ca, Mg, P, or N were supplied at reduced concentration. Reducing the concentration of K, Fe, or the mixture of trace elements normally supplied did not influence the effect of acidity of the nutrient solution. The uptake and distribution of Ca, Mg, P, and N throughout the plant was not affected by the acid treatments. It is concluded that acidic soil water or nutrient solutions interfere with the metabolism of calcium, magnesium, phosphorus, and nitrogen in the leaves.

ISSN:0008-4026    

DOI:10.1139/b87-156

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

The interface established betweenAlnus crispaand the basidiomyceteAlpova diplophloeusinvolves structural modifications of host cell walls and hyphal walls in the Hartig net region of the ectomycorrhizae synthesized in pouches. Indirect labelling of cell wall carbohydrates by using colloidal gold conjugated with the lectinsUlex europaeusagglutinin, wheat-germ agglutinin, and concanavalin A was applied to these mycorrhizae and to nonmycorrhizal roots. Significantly more binding of the lectins was observed in the mycorrhizal roots than in control roots. In the Hartig net region of mycorrhizal roots, the lectins bound intensely to the host cell wall, particularly the wall ingrowths, and to adjacent fungal walls, whereas in nonmycorrhizal roots, a sparse labelling was recorded in the cell wall. Possible explanations for this pattern of lectin binding include the following: the sugar residuesL-fucose, mannose, andN-acetylglucosamine may be utilized in the synthesis of the elaborate epidermal wall ingrowths andN-acetylglucosamine may be utilized in the synthesis of the labyrinthine wall branchings of the fungus; the sugar residues are bound to a proteinaceous fraction in the host and hyphal walls; the sugar residues bound by the lectins may be components of defense reaction elicitors released from the host wall and hyphal wall by wall-degrading enzymes; the sugar residues may simply be the result of enzymatic degradation of walls but not involving elicitors of defense reactions.

ISSN:0008-4026    

DOI:10.1139/b87-157

出版商:NRC Research Press    

年代:1987

数据来源: NRC