摘要:

The Natural Sciences and Engineering Research Council of Canada (NSERC) recently announced a plan to undertake a "reallocations exercise" designed to provide support for new initiatives and emerging fields of research in a period of fiscal restraint. NSERC's Grant Selection Committees (GSC) were instructed to establish committees charged with preparing reports that respond to the question "Why is it important for Canada that your research community should receive some of the funds available for reallocation?" The Plant Biology and Food Science Grant Selection Committee (GSC03) responded by striking a committee representing the breadth of research it supports. Extensive input was obtained from the scientific community through a web site and electronic discussion group. A discussion document was then prepared and distributed to 34 "consultants" representing NSERC-funded researchers and leaders in the agricultural, food, and forest industries. After refining the report, a second draft was circulated to more than 90 scientists for further review. This process provided us with a collective "vision" of our discipline that focuses on the importance of fundamental research, guided by excellence, innovation through multidisciplinary approaches, international leadership potential, and relevance to Canada and Canadians. To achieve this vision, NSERC must introduce a strategy to attract, train, and retain our best young minds, establish a broad, realistic funding base, and create opportunities for more interaction among disciplines. Six specific recommendations were put forward to achieve these goals with a total request for $15.3 million in reallocated and new money. If funded, this initiative will provide GSC03 researchers with the support required to generate the ideas, communicate the insights, develop the skills, and educate the personnel that will be essential for Canada's participation in the biotechnology revolution that is transforming global agriculture, food, and forest industries. Moreover, fundamental knowledge of the interaction between plants and their environment will also help Canada play a leading role in the effective, responsible stewardship of planetary resources in the 21st century.Key words: Natural Sciences and Engineering Research Council of Canada, reallocations exercise, plant biology, food science, biotechnology, fundamental research.

ISSN:0008-4026    

DOI:10.1139/b98-028

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Diplolepis nodulosa(Beutenmüller) induces small, single-chambered, prosoplasmic galls in stems ofRosa blandaAit. Gall initiation begins when adult females deposit a single egg into the procambium ofR. blandabuds. Pith cells at the distal pole of the egg lyse forming a chamber into which the hatching larva enters. Cells lining the chamber differentiate into nutritive cells, which serve as the larval food. Gall growth is characterized by the proliferation of parenchymatous nutritive cells causing gall enlargement. A separate gall vasculature does not form, but instead, gall tissues are irrigated by the existing stem vasculature. Maturation begins when gall tissues cease proliferating and differentiate into distinct layers concentrically arranged around the larval chamber. The innermost layer is composed of cytoplasmically dense nutritive tissue, followed by parenchymatous nutritive tissue, sclerenchyma, cortex, and epidermis. Parenchymatous nutritive tissue differentiates into nutritive tissue and is consumed by the larva. Galls ofD. nodulosaare susceptible to anatomical modification by the phytophagous inquilinePericlistus pirata(Osten Sacken). Galls attacked byP. piratabecome enlarged and multichambered, with little resemblance to inducer-inhabited galls.Periclistus piratakill the larva ofD. nodulosaat oviposition and deposit several eggs per host gall. Inquiline-occupied galls may contain the eggs of several females. Nutritive tissue induced byD. nodulosadisintegrates. Growth of attacked galls occurs prior to hatching ofP. pirataeggs. At egg hatch, the gall appears as an enlarged hollow sphere and larvae disperse over the chamber surface and feed on parenchymatous tissue. Feeding induces tissue proliferation, which surrounds each larva within its own chamber. As galls mature, cells surrounding each larval chamber lignify forming a sclerenchyma sheath. Cells inside the sclerenchyma sheath differentiate into nutritive cells and are consumed by the inquiline larvae.Key words:Rosa, Cynipidae, gall, developmental morphology, inquiline.

ISSN:0008-4026    

DOI:10.1139/b98-001

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

The genusThlaspiL. s.l. comprises numerous segregate lineages, which have been recognized as single genera. One of these,Microthlaspi, represents one such segregate. It consists of morphologically similar annual species. The species have different ploidy levels (2x, 4x, 6x) and are usually summarized under the designationThlaspi perfoliatumagg. The assumed ancestral diploid members of the species complex,Microthlaspi granatense(Boiss. & Reut.) F.K. Meyer,Microthlaspi umbellatum(Steven ex DC.) F.K. Meyer, andMicrothlaspi natolicum(Boiss.) F.K. Meyer, are restricted to northwestern Africa, southeastern Spain and Turkey, northern Iran, and Lebanon.Microthlaspi perfoliatum(L.) F.K. Meyer is widely distributed all over Europe and shows three ploidy levels. DiploidM. perfoliatumis restricted to Middle Europe, whereas tetraploid and hexaploidM. perfoliatumare distributed all over Europe. Individual plants from 125 natural populations throughout the geographic range were analysed using chloroplast DNA (cpDNA) and nuclear ribosomal DNA (nrDNA) restriction site analysis. WithinMicrothlaspi, 31 cpDNA restriction site mutations, six nrDNA restriction site variations, and two length mutations in the IGS region of the nrDNA were found, and a molecular phylogeny of the species complex has been derived. Polymorphisms in molecular data partitioned cytotypes ofM. perfoliatum. The geographical distribution patterns apparently reflect ancient speciation processes and postglacial vegetation history.Key words: chloroplast DNA, nuclear ribosomal DNA,Microthlaspiperfoliatumpolyploid complex, molecular phylogeny, biogeography.

ISSN:0008-4026    

DOI:10.1139/b98-006

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

In those regions of Europe where they coexist, the F and S intersterility groups (ISGs) ofHeterobasidion annosum(Fr.) Bref. are primarily found onAbiesspp. andPicea abies(L.) Karst., respectively. Eighty-three isolates ofH. annosumwere collected fromAbies albaMill. from 19 sites in Italy, including 10Abies-Piceamixed conifer stands in the eastern Alps. The ISGs of a subsample of 34 isolates were determined by ISG-diagnostic arbitrary-primed (AP) PCR primers. For a subsample of 16 isolates, including two S isolates from Norway and one S isolate from California, nuclear markers generated by AP-PCR analysis, and mitochondrial markers generated by restriction fragment length polymorphisms and sequencing of the ML5-ML6 region of the mitochondrial large ribosomal RNA gene indicated that, in Europe, (i) the F and S ISGs can be found in the same forest stand but they are two genetically distinct units with restricted gene flow between them; (ii) each of the two ISGs is monophyletic and may lack strong genetic substructuring in subpopulations; and (iii) the two ISGs are closely related to each other and their nearest common close relative is the allopatric S ISG from North America. By combining these results with paleobotanical information and results from previous studies, we postulate a recent sympatric divergence of these two groups driven by differential host specificity and mating barriers.Key words: species complex, protospecies, sympatric, mating barriers, host specificity.

ISSN:0008-4026    

DOI:10.1139/b97-185

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

A new plant from the Los Ahuehuetes locality, near Tepexi de Rodríguez, Puebla, Mexico, is described based on its leaves. They are characterized by being ovate to elliptic, 4.5 cm long by 2.1 cm wide, having an entire margin, eucamptodromous venation, a midvein that is slightly curved and attenuated towards the leaf apex, seven pairs of secondary veins diverging at an acute angle from the midvein, percurrent tertiary veins forking or sometimes reticulated forming areoles, and having a petiole 1.3 cm long and 0.3 cm wide. An agglomerative nonhierarchical analysis with average linkage, based on the definition of 41 character states in 18 operational taxonomic units allows distinction betweenKarwinskia,Berchemia, andRhamnus; the recognition of an extinct monotypic genus,Berhamniphyllum; and the identification of two fossil species ofKarwinskia, among which the new plant from Puebla,Karwinskia axamilpenseVelasco de León et al., is well defined. This new fossil leaf not only adds to the recently known Tertiary plants of the Los Ahuehuetes locality, but it gives new insights into the past flora of tropical North America and further supports the long history of some neotropical endemics, suggesting that, during the Tertiary, at least some areas in southern latitudes of North America could have been important for the origin and radiation of some taxa.Key words: Oligocene, Mexico, paleobotany, Rhamnaceae,Karwinskia.

ISSN:0008-4026    

DOI:10.1139/b97-186

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

The length of time that pollen remains viable after being removed from the anther may be subject to species-specific selection pressures, e.g., when the average transit time between anther and stigma is long, long-lived pollen may be favoured. Flowering plants that provide no reward to pollinators are predicted to have relatively long-lived pollen, because pollinators are less likely to immediately revisit flowers of a nonrewarding species. I studied the effect of pollen age on fertilization success in three species of orchids that provide little or no reward. Pollen was aged 0, 1, 2, 4, or 8 days outside of the anther and then placed on the stigmas of conspecific flowers. I collected and weighed all resultant fruits and used a subsampling technique to determine the number of embryonated seeds per fruit and the percentage of all seeds that had embryos. There was no evidence that pollen age affected fruit set, fruit weight, embryonated-seed number, or percentage of embryonated seeds in two species (Calopogon tuberosus(Linn.) Britton andPogonia ophioglossoides(Linn.) Ker.). In the third,Cypripedium reginaeWalt., 8-day-old pollen produced significantly lighter fruits with fewer embryonated seeds; however, the percentage of embryonated seeds was not affected. Although the pollen of these nonrewarding orchids appears to have an impressive life-span, it is difficult to make comparisons with other species because most previous studies have relied on laboratory tests of viability that appear to have little relation to performance of pollen in the field.Key words: pollen longevity, Orchidaceae, reproductive success.

ISSN:0008-4026    

DOI:10.1139/b98-010

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Red heather (Phyllodoce empetriformis(Sw.) D. Don) recovery after experimental fires and wildfires was studied at five subalpine sites in Washington State, U.S.A. Experimental burn treatments showed that fire had a neutral to positive effect on stem numbers but generally a short-term negative effect on aboveground biomass production. Although there were no differences in effects between experimental burn and clip treatments, long-duration smoldering beyond that documented in our experiments may have more damaging effects. On three wildfire sites, sprouting was vigorous after fire except at one site adjacent to forest cover where significant litter consumption occurred. The duration of fire, rather than its presence or absence, may be an important character of the fire regime in predicting post-fire response of red heather.Key words: red heather,Phyllodoce empetriformis, fire, subalpine meadows, Pacific Northwest.

ISSN:0008-4026    

DOI:10.1139/b98-005

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Work from the 1970s indicated that, relative to either parent species, crosses between red spruce (Picea rubensSarg.) and black spruce (Picea mariana(Mill.) B.S.P.) were inferior with respect to both growth and photosynthesis. We re-examined the hypothesis that there is negative heterosis in hybrids of red and black spruce using 22-year-old trees in a common garden study planted on two sites. The trees were the product of controlled crossings and represent a continuum from hybrid class 0 (pure black spruce) to hybrid class 1 (pure red spruce). Progeny of all controlled crosses were measured for height and diameter. A subset of families were measured for gas exchange and were assessed using a hybrid index based on needle color, needle configuration, twig ridges, twig bark color, vegetative bud color, and cone scale morphology. Tree growth rate linearly declined with the increasing proportion of red spruce germplasm (increasing hybrid index). In 1994, intermediate hybrid index classes did not differ in gas exchange from either pure black spruce (hybrid index class 0) or pure red spruce (hybrid index class 1), and in 1996, hybrids displayed slightly higher rates of gas exchange. Thus, negative heterosis was not apparent in 22-year-old trees. Individual tree hybrid index generally agreed with expectation based on midparent means, although the relationship was stronger on the higher productivity site (r2= 0.91) than the poorer productivity site (r2= 0.54).Key words: black spruce, heterosis, hybrid, photosynthesis, red spruce.

ISSN:0008-4026    

DOI:10.1139/b98-002

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

The genusRhynchospora(Cyperaceae) is a widely distributed Brazilian group, with approximately 150 species. We have studied mitosis and (or) meiosis of 16 species of four sections (Dichromena,Longirostres,Polycephalae, andPluriflorae). The results showed high frequencies of chromosome number multiples ofx= 5, which is the probable basic number. Polyploidy, in contrast to agmatoploidy and (or) symploidy, seems to be the predominant cytogenetic mechanism in the evolution of the karyotype. Primary constrictions were not visible in the chromosomes, suggesting a holocentric condition, as observed in other genera of this family. Karyotype interspecific differences were useful in the cytotaxonomic analysis in three sections. Our data propose (i) the separation ofRhynchospora ciliata(Vahl.) Kükenth. fromRhynchospora nervosa(Vahl.) Böckeler (sectionDichromena), (ii) the inclusion ofRhynchospora legrandiiKükenth. ex Barros as a subspecies ofRhynchospora corymbosa(L.) Britton (sectionLongirostres), and (iii) a suggestion for the organization of sectionPluriflorae.Key words:Rhynchospora, Cyperaceae, holocentric chromosomes, polyploidy.

ISSN:0008-4026    

DOI:10.1139/b98-013

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Plant responses to defoliation were examined usingSolidago altissimaand a leaf-chewing beetle (Trirhabdasp.). Plants were exposed to five intensities of defoliation (ranging from 0 to 85% leaf area loss) and effects on carbon gain, vegetative growth, and flowering were determined. Defoliated plants partially restored their capacity for carbon gain in the following ways: (i) activity of damaged leaves remaining after defoliation was increased via delayed senescence and enhanced photosynthetic rates and (ii) regrowth leaves on damaged plants had higher specific leaf area (leaf area per leaf mass) than comparable leaves on undamaged plants, but photosynthetic rates per unit area were equivalent to controls; thus, these leaves covered more area for a given investment in biomass with no loss in activity per unit area. Delayed leaf senescence and compensatory photosynthesis are commonly observed following defoliation, but increased specific leaf area is not generally recognized as a mechanism contributing to plant regrowth. In spite of these changes, total carbon gain capacity of defoliated plants was still less than that of controls after 3 weeks of regrowth. Overall plant performance was reduced by defoliation. Defoliated stems grew at a slower rate early in the season, added fewer new leaves in the first few weeks after defoliation, and had fewer lateral stems throughout the season. Damaged plants delayed flowering and maintained height growth later into the season than undamaged plants. Damaged stems reached heights comparable with undamaged stems by the end of the season, but they were thinner and their flower production was lower. Declines in plant growth and flowering were linear functions of the percentage leaf area loss, suggesting that even low levels of insect feeding are likely to affect plant performance.Key words:Solidago altissima,Trirhabda, defoliation, compensatory photosynthesis, insect herbivory, herbivore damage, plant compensation.

ISSN:0008-4026    

DOI:10.1139/b98-004

出版商:NRC Research Press    

年代:1998

数据来源: NRC