摘要:

Seasonal protein changes were followed in seedlings of interior spruce (a mixture ofPicea glaucaandP.englemannii) and Douglas-fir (Pseudostuga menziesii) by sodium dodecylsulfate – polyacrylimide gel electrophoresis. A 30-kDa protein in seedlings of Douglas-fir and a 30- and 27-kDa protein in interior spruce that were not detected in the late summer accumulated in seedling tissues during the fall. These proteins remained present throughout the winter but declined rapidly in seedlings during the initial flush of spring growth. There was an increase in the total protein content of interior spruce seedling tissues during the fall; however, the accumulation of the 30- and 27-kDa protein was tissue specific, since it increased in the apical bud, shoot, and root tissue but not in the leaves. By late fall these proteins represented approximately 15% of the total seedling protein. Measurements of variable chlorophyll fluorescence indicated that the accumulation of these overwintering proteins was associated with the seasonal decline in photosynthetic capacity. These results suggest that conifer seedlings may utilize these proteins as a storage reserve during overwintering.Key words: conifers, electrophoresis, overwintering, proteins, seasonal, seedlings.

ISSN:0008-4026    

DOI:10.1139/b91-060

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Data on reproductive and vegetative weights of individuals from five species of agricultural weeds (Apera spica-ventiL.,Datura stramoniumL.,Abutilon theophrastiMedic.,Sorghum halepense(L.) Pers., andPanicum miliaceumL.) were used to test Weiner's (1988) model of linear size-dependent reproductive output in plants. In general, the populations showed strong evidence (P < 0.001) of linear relationships between reproductive and vegetative weight. Linearity was most pronounced in cases where size differences were primarily due to competition. Generally, the linear relationships were consistent from population to population within a species. Many of the populations also showed positivex-intercepts, indicating a threshold size for reproduction. However, there were a number of populations with no apparent relationship between reproductive and vegetative weight, with departures from linearity, or with positivey-intercepts (negativex-intercepts).Key words: reproductive weight, vegetative weight, agricultural weeds, size-dependent reproduction.

ISSN:0008-4026    

DOI:10.1139/b91-061

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Arabidopsis thalianahas a seven-celled eight-nucleate megagametophyte of thePolygonumtype; each cell type displays a different form of structural specialization. The egg apparatus cells are highly polarized; the egg has a large micropylar vacuole and chalazally sited nucleus, whereas the opposite is true for the synergids. At the chalazal region of the egg apparatus cells there are no cell wall boundaries, although their plasmalemmas are in intimate contact. The common wall between the two synergids is thin and irregular and contains plasmodesmatal connections. The synergid cytoplasm is rich in organelles; profiles of rough endoplasmic reticulum appear in masses of parallel stacked cisternae, and large accumulations of mitochondria occur adjacent to the filiform apparatus. The egg cell cytoplasm is quiescent; ribosome concentration and frequencies of dictyosomes and endoplasmic reticulum are noticeably lower and plastids are poorly differentiated. The central cell is long and vacuolate with a large diploid nucleus; fusion of the polar nuclei occurs prior to embryo sac maturity. The cytoplasm contains numerous starch-containing plastids accumulated in a shell around the nucleus. A high ribosome concentration and the absence of vacuoles and dictyosomes typifies the antipodal cell cytoplasm. All antipodal cells are interconnected by plasmodesmata as well as being connected to the nucellus and central cell.Key words:Arabidopsis, embryo sac, embryogenesis, cell specializations, stereology.

ISSN:0008-4026    

DOI:10.1139/b91-062

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Embryo differentiation inArabidopsis thalianafollows the classicalCapsellavariation of the Onagrad type. Fertilization occurs approximately 3 h after flowering, whereupon vacuolar organization in the zygote changes and the cell elongates rapidly to approximately three times its original length. Cytoplasmic polarization is maintained. During the first two division steps there is very little increase in total cell volume, and during subsequent divisions vacuole number increases, with a concomitant decrease in size. Plastids remain undifferentiated up to the late globular stage, after which grana begin to develop. Ribosomal concentration increases significantly after fertilization. Differences between embryo proper cells become evident by the heart stage; vacuole, plastid, and mitochondrial abundance, size, and complexity vary within the embryo. There are no plasmodesmatal connections with the endosperm or integuments. Suspensor development is complete by the early globular stage, when it consists of seven to nine highly vacuolate cells, each linked by end wall plasmodesmata. Ribosome and volume densities of plastids and mitochondria are significantly lower than in the embryo proper organelles, and dictyosomes are infrequent. Embryo sac wall projections proliferate throughout the micropylar chamber, especially adjacent to the filiform apparatus and zygote base, and ingrowths form on the basal cell proximal wall.Key words:Arabidopsis, embryogenesis, embryo differentiation, wall ingrowths.

ISSN:0008-4026    

DOI:10.1139/b91-063

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

The development and morphology of the stomatal complex inPhaseolus vulgariswas examined by light microscopy, scanning electron microscopy, and transmission electron microscopy (TEM). The outer aperture formed between the stomatal guard cells was bordered by cuticular ledges, 1.2–5.3 μm wide. These were composed of a matrix of electron-dense fibrils supporting an autofluorescent amorphous outer layer, homologous to the cuticle. This layer of cuticle lined the ventral walls of the guard cells and extended into the substomatal chamber. During stomatal development, as the guard cells separated, the outer cuticular layer covering the incipient aperture stretched and split, forming stomatal lips. These lips, 0.2–1.4 μm wide, were oriented horizontally, upright, and folded back from the ledge in TEM thin sections. In cryopreserved stomata, the lips were generally oriented upright regardless of whether the outer aperture was open or closed. Previous studies have implicated that stomatal lips may function to signal appressorium formation in urediniospore germlings ofUromyces appendiculatus. This study indicated that dimensions of the lips were within the parameters required to induce appressorium formation on artificial membranes. Other components of the stomatal architecture may also be involved in the induction of appressorium formation.Key words:Uromyces appendiculatus,Phaseolus vulgaris, stomata, cuticle, appressoria.

ISSN:0008-4026    

DOI:10.1139/b91-064

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Linear furanocoumarins (psoralens) were present both inside and on the surface of dry fruits of seven species of Umbelliferae and one species of the Leguminosae and on seeds of three of Rutaceae examined. Surface concentrations varied between traces and 40 μg/g of the mature fruits or seeds, amounting to 0.38–43% of the total. In the whole fruits concentrations were very high inAngelica archangelica,Heracleum lanatum,Pastinaca saliva, andPsoralea bituminosa, reaching levels of milligrams per gram fresh weight of fruits. This high concentration inside the fruit may be the cause of poor germination of embryos inA.archangelicaandH.lanatum. Seeds of the Rutaceae had much smaller concentrations of furanocoumarins both on the surface and within the seed.Key words: fruits, seeds, surface, furanocoumarins, Umbelliferae, Rutaceae, dermatitis, plant defense.

ISSN:0008-4026    

DOI:10.1139/b91-065

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Leaf size and shape, long used to differentiate taxa inHaenianthus, were found to be less useful than previously believed. Nevertheless, two species can be recognized on the basis of leaf shape,H.incrassatusandH.salicifolius. The former species has long petioles, attenuate leaf bases, and thin laminas and is endemic to cloud forests of Jamaica. The latter species, with short petioles, acute to acuminate leaf bases, and thick laminas, has two varieties,H.salicifoliusvar.salicifoliusof Cuba and Haiti, andH.salicifoliusvar.obovatusof Cuba, Hispaniola, and Puerto Rico.Key words: Caribbean,Haenianthus, morphometric analysis, Oleaceae.

ISSN:0008-4026    

DOI:10.1139/b91-066

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

The species ofDiheterosporaattacking bdelloid rotifers have been compared withDiheterospora chlamydosporiaand found to be different in a number of important characteristics. These include the consistent presence of aphanophialides, proliferation of phialides and aphanophialides to form polyphialides, containment of the conidial mass in a hydrophobic membrane, reduction or elimination of the verticillate arrangement of the conidiogenous cells, and presence of a large oil droplet in each conidium. It is considered that these differences are sufficient to separate the rotifer parasites from bothDiheterosporaandVerticillium. Accordingly, a new genus,Rotiferophthora, is erected to accommodate the 17 species recognized in this group of fungi. Thirteen rotifer parasites previously described underDiheterospora,Verticillium, orAcrostalagmusare transferred toRotiferophthora, and four new species ofRotiferophthoraare described.Key words:Diheterospora,Rotiferophthora, endoparasite, rotifer.

ISSN:0008-4026    

DOI:10.1139/b91-067

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Haptosporais described as a new genus of the Hyphomycetes endoparasitic in rotifers. The genus is distinguished by conidia that have a doughnut-shaped modification at the base. This structure appears to have a function in lodging the conidium in the mastax of the host. The conidiogenous cells are phialides, each with a membranous collarette. Two species of Hyphomycetes, described previously asPhialophora endoparasiticaandP.tribrachispora, are transferred toHaptospora, and a third species,Haptospora appendiculata, is described as new.Key words:Phialophora,Haptospora, endoparasite, rotifer.

ISSN:0008-4026    

DOI:10.1139/b91-068

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

One-month-oldPinus contortaDougl. seedlings were inoculated with mycorrhizal fungi (Wilcoxina mikolaeisolate R947), plant growth promoting bacteria capable of fixing nitrogen (Bacillusstrain L6), or coinoculated with a combination ofWilcoxinaandBacillus. Seedlings were grown with 0.35 mM Ca(15NO3)2(5%15N atom excess) as the only nitrogen source. Fungal inoculation alone resulted in the synthesis of ectendomycorrhizae but decreased shoot biomass. Bacterial inoculation alone did not affect seedling biomass or foliar nitrogen content. Coinoculation of seedlings withWilcoxinaandBacillusresulted in a similar degree of ectendomycorrhizal infection compared with fungal inoculation alone, but shoot biomass was greater than that of seedlings receiving the fungus alone. Root biomass and stem height were not altered by coinoculation. Total foliar nitrogen was lower in seedlings inoculated withWilcoxina, and coinoculation withBacillusdid not reverse this trend. Based on the15N to14N ratio of foliage, associative nitrogen fixation byBacilluscontributed 4% (P < 0.05) of seedling foliar nitrogen whether or not seedlings were mycorrhizal. However, coinoculated seedlings had lower foliar nitrogen (percentage basis) compared with uninoculated controls. These results suggest that growth of mycorrhizal pine can be stimulated by inoculating with beneficial bacteria. Growth promotion does not result from increased formation of ectendomycorrhizae and may, only in part, result from associative nitrogen fixation.Key words:Pinus, microorganisms, growth promotion, nitrogen fixation.

ISSN:0008-4026    

DOI:10.1139/b91-069

出版商:NRC Research Press    

年代:1991

数据来源: NRC