bluuebunny/crossref_metadata_2025 huggingface dataset:
Interactions entre le cycloheximide et la 6-benzylaminopurine au cours du verdissement de cotylédons de concombre
Authors: Roussaux J. , Hoffelt M. , Farineau N.
Published: April 2011

Etiolated cotyledons of cucumber (Cucumis sativus L.) were isolated and incubated for 15 h in the dark and 48 h in the light in the presence of 10−6 g/mL 6-benzylaminopurine (6-BAP) or 3.10−6 and 10−5 g/mL cycloheximide (CHX). Cotyledons were permanently maintained on these compounds or transferred from one medium to the other after the dark period or after 6 h of the light. 6-BAP stimulates both chlorophyll synthesis and plastid differentiation. Chlorophyll synthesis is more affected than differentiation in the presence of CHX. Only some thylakoids are present in plastids treated permanently with CHX at 10−5 g/mL. At 3.10−6 g/mL, CHX inhibits the development of the stroma thylakoids and the granal stacks. The effect of CHX is particularly important during the 1st h of light; it is partially reversible. During the treatment with 6-BAP followed by CHX (or conversely), the ultrastructural effect of 10−5 g/mL CHX is removed if 6-BAP is given before the inhibitor. After 48 h the plastid ultrastructure depends particularly on the compound applied during the 1st h of light. 6-BAP and CHX are not competitive during chlorophyllogenesis. 6-BAP increases and CHX decreases the incorporation of 32P into cytoplasmic and etioplastic rRNA during the dark. During the light, 6-BAP increases the incorporation in chloroplastic rRNA only and CHX decreases the incorporation in cytoplasmic rRNA only. The modes of action of CHX and its relations with 6-BAP are discussed.
Erratum: On the promotion of senescence in Brassica oleracea var. capitata by Alternaria brassicicola and by Botrytis cinerea
Authors: Poapst P. A. , Ramsoomair B. Anne , Gourley C. O.
Published: April 2011

The caption to Table 5 should read "Carbon dioxide concentrations above cabbage leaf discs floated on distilled water, inoculated with Alternaria brassicicola, and retained in darkness at six temperatures."
An ecological approach to anatomical variation in Clathromorphum circumscriptum (Rhodophyta, Cryptonemiales)
Authors: Gendron L. , Cardinal A.
Published: April 2011

Anatomical variations in Clathromorphum circumscriptum collected at various levels and stations in the lower St. Lawrence Estuary were studied, using principal-component analysis performed on the correlation matrix of 12 morphometric characters. The first principal component, which accounted for 30.8% of total sample variance, was associated with variations following a bathymetric gradient. The continuous nature of the variations described could be attributable to a plastic response of the algae.The second principal component, which accounted for 20% of total variance, was not associated with variations following a geographic gradient as it may have been expected. However, samples from one station separated from others by having shorter cells. A causal relationship between the low spring and fall salinities recorded at this station and small cell size is suspected.With regard to the relation found between anatomical variations and the bathymetric gradient, interspecific relations within the genus Clathromorphum are examined.
A new species of Pterula (Aphyllophorales) with corticioid characteristics
Authors: McLaughlin David J. , McLaughlin Esther G.
Published: April 2011

Pterula echo sp.nov. is described from culture. It was isolated from Theobroma cacao L. from Trinidad. Fruitbodies formed on sterile cocoa twigs and on nutrient agar. Optimum temperature for fruiting and sporulation was 20 to 25 °C. Meiosis was normal and chiastic. Phenotypic plasticity of some taxonomic characters in Pterula is discussed.
Suppression of stem rust resistance in the hexaploid wheat cv. Canthatch by chromosome 7DL
Authors: Kerber E. R. , Green G. J.
Published: April 2011

The nullisomic for chromosome 7D (2n = 40) of the hexaploid wheat cv. Canthatch (Triticum aestivum L., 2n = 42) was found to be resistant in both the seedling and adult-plant stages to several races of stem rust (Puccinia graminis Pers. f. sp. tritici Eriks. and E. Henn) to which normal disomic Canthatch (2n = 42) was susceptible. Since ditelosomic 7DL (2n = 40 + tt) reacted in the same manner as Canthatch, it appears that a gene(s) is present on the long arm of chromosome 7D that suppresses resistance determined by other genes, probably on chromosomes of the A and B genomes. Evidence indicated that the suppressor was derived from the ancestral, diploid progenitor of common wheat, Aegilops squarrosa L., rather than by mutation at the hexaploid level. The results provide a genetic explanation for apparent failures of some attempts to transfer stem rust and leaf rust resistance to hexaploid wheat from diploid and tetraploid relatives.
Light and electron microscopy studies on the infection of tomato fruits by Botrytis cinerea
Authors: Rijkenberg F.H. J. , Leeuw G. T. N. De , Verhoeff K.
Published: April 2011

A light microscopy study of the host–parasite relationship of Botrytis cinerea on immature tomato fruits was combined with an electron microscopy examination. Both techniques indicate that the cuticle is dissolved enzymatically rather than ruptured mechanically. Inter- and intracellular hyphae have no apparent effect on the cuticle, but do break down wall material. If the penetration tube development is arrested after emerging from the cuticle into the wall, wall discolouration and wall thickening become evident and a considerable increase in host cell organelles below the penetration site is observed. A papilla is also apposited. At successful penetration, when the hypha emerges from the cell wall into the host cell, little cell wall discolouration at the infection site is evident, but the cytoplasm becomes degenerate. Further hyphal extension then occurs in the epidermis, killing more epidermal cells, and leading to collapse, but not penetration, of underlying tissue.
Changes in electroosmotic measurements in Nitella translucens when turgor pressure of cells is reduced by solutions of sucrose and mannitol
Authors: Fensom D. S. , Silverberg A.
Published: April 2011

Water-ion coupling as measured by electroosmotic efficiency across the plasma membrane of Nitella translucens, was found to increase when the turgor pressure of the cells was reduced by adding 0.1 M or more mannitol or sucrose to the water outside the cells. It is thought that reduction in turgor causes an increase in thickness of the membrane, and that this increased thickness is associated with the increase in ion-water coupling.
Intraseasonal variation in chlorophyll content and chloroplast ultrastructure of selected plant species in a deciduous forest
Authors: Floyd B. W. , Noble R. D.
Published: April 2011

Chlorophyll content and chlorophyll a – chlorophyll b ratios were determined at regular intervals over a 3-month period for eight forest species selected from different levels in a deciduous forest. Chloroplast ultrastructure and starch content were investigated in five of the eight species, chosen to be representative of each level.Chlorophyll a – chlorophyll b ratios for Quercus alba L., Liriodendron tulipifera L., Acer rubrum L., Cornus florida L., Desmodium nudiflorum (L.) DC., and Sassafras albidum (Nuttall) Nees reached a peak at the time of canopy closure whereas total chlorophyll content reached a maximum 1–3 weeks later. The number of thylakoids per granum in all species increased after canopy closure. Chlorophyll content and variations in thylakoid number per granum were found to be related to light intensity variations.Starch content, based on size and number of starch grains, remained stable prior to and after closure in Q. alba, D. nudiflorum, and S. albidum, where a decrease in the number of starch grains was observed after closure. The number of starch grains in D. nudiflorum appeared to decrease during the period 6 weeks after closure. The variations in starch grain number were an indication of photosynthetic activity in these species.The disorganization of grana thylakoids and the development of electron dense and transparent bodies in the chloroplast stroma of all species sampled, 6 weeks after closure, was a preliminary indication of leaf senescence. Electron transparent bodies were considered to be by-products of grana thylakoid degradation.
Seed bank size and distribution of seeds in cottongrass tussock tundra, Eagle Creek, Alaska
Authors: McGraw J. B.
Published: April 2011

Soil from cottongrass (Eriophorum vaginatum) tussock tundra at Eagle Creek, Alaska, was analyzed with respect to the distribution, abundance, and germination patterns of buried viable seeds. Seeds of Carex bigelowii, Eriophorum vaginatum, and Ledum palustre were abundant. Smaller amounts of Empetrum nigrum and Betula spp. were also present. Buried seeds were found to 21 cm below the soil surface. Germination was rapid in the first 3 weeks of exposure to greenhouse conditions and continued at a slower rate for 5 more weeks. The ecological importance of seed banks in arctic regions and their possible implications for management of cotton-grass tussock tundra vegetation are discussed.
A taxonomic revision of Crataegus (Rosaceae) in Ontario
Authors: Phipps J. B. , Muniyamma M.
Published: April 2011

This taxonomic revision of Ontario Crataegus (Rosaceae) indicates the presence of 39 good species in 14 series in the province. This appears to represent about one-third of the taxa of North American Crataegus. Additionally, six "little-known" species are briefly described. The reasons for taxonomic difficulty in Crataegus in eastern North America are fully discussed and attention is drawn to the care with which specimens must be collected and the characteristics known to be of diagnostic value. A key to and descriptions of the series are provided. A key to species is followed by descriptions of each. Line drawings of 25 species at anthesis are provided to indicate the range of variation in Ontario Crataegus and to underline discriminating features. This is the only pictorial record of this detail for Ontario Crataegus. Thirty-two colour figures emphasize the differences among fruiting Crataegus, which have hitherto caused much confusion to collectors. Thirty-five species are mapped for their Ontario distribution and exemplar specimens are cited for all taxa. Seven new combinations have been made. Our species concepts are not consistent because of the range of variation patterns found in the genus, from ordinary sexual outbreeders through polytypic forms with various cytotypes to situations where hybrid swarms may be suspected. The taxonomic situation is known to be complicated by apomixis and polyploidy.
Effects of smelter pollutants on forest leaf litter decomposition near a nickel–copper smelter at Sudbury, Ontario
Authors: Freedman B. , Hutchinson T. C.
Published: April 2011

Forest soils and litter in the vicinity of a large nickel–copper smelter at Sudbury, Ont. are known to be contaminated with a variety of heavy metals. In view of this, studies were carried out to determine if forest litter decomposition processes have been affected. The effects of nickel and copper on the decomposition of forest litter were investigated using a variety of techniques in which contaminated and control sites were compared. At contaminated sites an increase in litter standing crop was found. This was related to lower rates of litter decomposition at these sites, as evidenced by reduced rates of breakdown of litter in mesh bags, compared with uncontaminated sites. Lower rates of CO2 flux and acid phosphatase activity were also found at the contaminated sites. In a laboratory experiment, the addition of copper and (or) nickel to a homogenate of leaf litter was shown to depress the rate of dry weight loss and CO2 flux. Negative effects commenced at metal concentrations comparable to those observed in litter at contaminated sites in the field.
Effects of nitrogen fertilizer, shade, and the removal of new growth on longevity of overwintering bog ericad leaves
Authors: Reader R. J.
Published: April 2011

Bog ericads, such as Labrador tea (Ledum groenlandicum), bog laurel (Kalmia polifolia), and leatherleaf (Chamaedaphne calyculata), retain individual leaves for two growing seasons in southern Ontario, presumably to facilitate nutrient movement between overlapping leaf cohorts. The objective of this study was to evaluate the effects of nutrient availability, shade, and the removal of new growth on the longevity of leaves during their second growing season. Longevity was extended significantly (p < 0.05) by removing new growth, but not by shading leaves (p > 0.05). The addition of nitrogen fertilizer increased only C. calyculata longevity. Interspecific variation in treatment effects appeared to be related to the positions occupied by the three species on environmental gradients. None of the experimentally treated leaves survived past the end of their second growing season, with the magnitude of treatment effects ranging from a reduction in longevity of 10 days to an increase of 25 days.
Nuclear pore structure in quiescent buds of Tilia europaea
Authors: Willison J. H. M. , Cragg F. J.
Published: April 2011

Quiescent shoot apical tissue from buds of the linden tree (Tilia europaea L.), collected during winter months, was frozen without pretreatment and freeze-fractured for electron microscopy. A proportion of the nuclear envelopes bore unusually large nuclear pores, having diameters up to 175 nm. Results from cross-fractured nuclear envelopes were consistent with results from envelopes fractured in the membrane plane, indicating that the larger pores are unlikely to be artefacts of fracturing. In these large pores, it was not possible to determine the relationship between the annulus (the material contained within the membranous pore) and the membranous periphery of the pore. Particularly, it could not be determined whether the annulus expanded concomitantly with the pore. It is proposed that variations in nuclear pore diameter may arise as a result of pulsatory activity occurring in all pores, rather than representing static differences between individual pores.
A contribution to the taxonomy of the Oxytropis campestris complex in northwestern North America
Authors: Elisens Wayne J. , Packer John G.
Published: April 2011

The Oxytropis campestris complex in northwestern North America is a polyploid series comprising at least seven morphologically and geographically distinct taxa. In light of the data of the present study, the authors propose that five taxa be reelevated to species status: O. cusickii Greenm., O. monticola Gray, O. columbiana St. John. O. jordalii Porsild, O. varions (Rydb.) K. Schum.; and that two taxa be recombined as subspecies: O. monticola Gray ssp. dispar (A. Nels.) Elisens & Packer and O. jordalii Porsild ssp. davisii (Welsh) Elisens & Packer.Three different chromosome numbers are present in the complex and represent the tetraploid (2n = 32), hexaploid (2n = 48), and dodecaploid (2n = 96) condition. Three species have uniform chromosome numbers (O. cusickii, 2n = 48; O. jordalii, 2n = 32; and O. columbiana, 2n = 48), two taxa, O. varians and O. monticola ssp. monticola, exhibit two different chromosome numbers. No attempt to subdivide O. varians was undertaken as; with the exception of guard cell size, no differences were observed between hexaploid and dodecaploid representatives. At least two distinct entities appear to be present in O. monticola ssp. monticola, for, while morphologically, cytologically (2n = 32), and ecologically uniform east of the continental divide, it is quite variable in appearance and has a different chromosome number (2n = 48) west of the divide.
Effects of environmental factors on growth and sclerotium formation in Aspergillus ochraceus
Authors: Paster N. , Chet I.
Published: April 2011

The effects of carbohydrates, amino acids, sulphur-containing compounds, temperature, pH, and light on growth and sclerotium production in Aspergillus ochraceus were studied. The maximal number of sclerotia was formed on medium containing sucrose at a concentration of 2 × 10−1 M, while on the lactose, galactose, and arabinose media no sclerotia were formed and poor mycelial growth was observed. Among the amino acids tested, glutamic acid (10−2 M) enhanced sclerotium formation, whereas there was complete inhibition when methionine (10−2 M) and ethionine (10−2 M) were added. Good production of sclerotia occurred on medium containing glutathione in all concentrations tested. Among the other sulphur-containing compounds tested, only sodium thiosulphate at a concentration of 10−1 M inhibited sclerotium formation without inhibition of mycelial growth. The pH at which sclerotia were formed ranged from 4.0 to 9.0. There was no growth at pH 3.0, and normal mycelial growth without sclerotium production occurred at a pH range of 11.0 to 13.0. Optimal temperatures for mycelial growth and sclerotium formation were 28 and 32 °C, while less growth and no sclerotium production occurred at 20 and 24 °C. Extensive production of sclerotia was observed when cultures were grown in the dark, while under continuous white, red, or blue light sclerotium production was sparse. It is suggested that sulphur-containing compounds can serve as a tool for studying the mechanism of sclerotium production in A. ochraceus.
Association of vesicular–arbuscular mycorrhizal fungi with the moss Funaria hygrometrica
Authors: Parke Jennifer L. , Linderman R. G.
Published: April 2011

Reports on the mycorrhizal status of mosses have been scanty and inconclusive. We observed hyphae and vesicles resembling structures of vesicular–arbuscular (VA) mycorrhizal fungi within the moss Funaria hygrometrica Hedw. growing on the soil surface of asparagus – Glomus epigaeus pot cultures. Controlled-environment experiments to determine whether moss is a potential host for VA fungi were conducted by inoculating moss cultures, asparagus plants, or combinations of moss and asparagus plants with chlamydospores of G. epigaeus. Examination of cleared and stained asparagus roots and moss plants 10 weeks after addition of G. epigaeus spores revealed typical arbuscules, vesicles, and hyphal coils in roots of asparagus grown alone or in combination with moss; hyphae, vesicles, and spores were seen in moss plants, but only in those grown with asparagus "companion" plants. Glomus epigaeus colonization was widespread in moss stem and leaf tissue, and spore production was most prolific in senescent tissues. Similar endophytic structures and abundant sporulation occurred in the moss layer of G. mosseae and G. fasciculalus moss-companion plant pot cultures. Although the Funaria–VA fungus association is apparently not a mutualistic one, the system may have ecological significance as well as potential for production of VA inoculum.
Archegonial opening in Psilotum
Authors: Whittier D. P. , Peterson R. L.
Published: April 2011

The opening of archegonia was observed in Psilotum gametophytes from axenic culture. Contrary to earlier proposals that the outer neck cells break off, archegonial opening in Psilotum is similar to that of other pteridophytes. The rows of neck cells split apart to release the contents of the neck canal which clears a passageway from the egg to the outside. The movement of the rows of neck cells is unusual in that after separation they reflex and almost touch the gametophyte surface.
The incompatibility relationships of tristylous species of Oxalis section Ionoxalis of southern Mexico
Authors: Weller Stephen G.
Published: April 2011

Ancestral incompatibility relationships occur in populations of tristylous species of Oxalis section Ionoxalis in southern Mexico. Legitimate pollinations lead to substantial seed production; illegitimate pollinations result in complete failure of seed production in most cases. Modifications of trimorphic incompatibility which have led to the evolution of distyly in northern populations of O. alpina were not detected in populations of the southern Mexican species. Rapid genomic changes which have occurred during the northward migration of Oxalis species apparently have been accompanied by the spread of incompatibility modifiers favoring the evolution of distyly.
Association of xylem-limited bacteria with elm, sycamore, and oak leaf scorch
Authors: Hearon Suzanne S. , Sherald James L. , Kostka Stanley J.
Published: April 2011

Ultrathin sections of leaves from American elms (Ulmus americana L.), sycamores (Platanus spp.), and two red oak species (Quercus spp.) that exhibited leaf scorch were examined by transmission electron microscopy. Rod-shaped, ripple-walled bacteria resembling the Pierce's disease organism were found consistently in tracheary elements of the primary and secondary veins of diseased plants. Smaller, ripple-walled, densely stained, irregular-shaped bodies (SDB) were found also in a matrix that lined the inner walls or filled the lumina of the tracheary elements. In leaf scorch affected American elms the bacteria were 0.3–0.4 μrn × 0.9–2.4 μm, with rounded ends. Fimbriae-like structures radiated from a few organisms. Bacteria were frequently embedded in a matrix. Pit cavities and the ends of tracheary elements were often filled with the bacteria–matrix complex. Rod-shaped bacteria were not as numerous in the diseased sycamore and oak as in diseased elm; however, SDB's were more numerous. Bacteria in sycamore (1.0–1.8 μm) and oak (1.0–2.0 μm) were slightly shorter than those in elm, many had numerous fimbriae-like hairs, and some were tapered at one end. Indirect fluorescent antibody staining showed a serological relationship between bacteria extracted from elm and oak and the Pierce's disease bacterium.
The effect of aerial insecticide spraying for spruce budworm control on the fecundity of entomophilous plants in New Brunswick
Authors: Thaler G. R. , Plowright R. C.
Published: April 2011

Eight entomophilous plants, Aralia nudicaulis L., Clintonia borealis (Ait.) Raf., Cornus alternifolia L., Cornus canadensis L., Cornus stolonifera Michx., Kalmia angustifolia L., Maianthemum canadense Desf., and Viburnum trilobum Marsh., all of which bloom shortly after forest spray application in New Brunswick, were shown by bagging experiments to be dependent on insect visitation for seed set. All species showed significantly lower fecundity in fenitrothion-treated than in unsprayed areas. No depression of fecundity in Clintonia borealis or Kalmia angustifolia was found associated with aminocarb (Matacil) spraying.
An analysis of the element content of lichens from the Northwest Territories, Canada
Authors: Puckett K. J. , Finegan E. J.
Published: April 2011

The results of a survey of the element content of saxicolous and terricolous lichens collected from the Northwest Territories, Canada, are summarized. Fourteen lichen species were collected from 45 sites and the lichens were analysed for 20 elements by instrumental neutron activation and X-ray fluorescence.An enrichment factor (EF) was calculated for each element analysis. The elements aluminium, chromium, iron, sodium, titanium, and vanadium had mean EF values of 1–5 for all species. These low EF values indicated that, relative to average values for crustal rock, there was no enrichment of these elements in the lichens concerned. For other elements (chlorine, lead, and sulphur) consistently higher EF values were obtained. These higher values were interpreted in terms of (a) differing methods of element accumulation, (b) sources of elements both natural and anthropogenic other than crustal rock and (or) soil, and (c) marked deviations of the actual substrate concentrations from the average crustal-rock concentrations used.The underlying structure of the data from some species was investigated using ordination techniques. These techniques provided some description of the element associations within the lichen thallus. These element associations were examined in relation to sources external to the plant. A principal component analysis was carried out on the data for each of three species, Cetraria cucullata, C. nivalis, and Cladina stellaris. In all cases, the first five principal components explained 81–89% of the variation in the data. One component which had high weightings for aluminium, scandium, and vanadium (with or without iron, nickel, and titanium) was common to all three species. Similarly, a second component with high weightings for calcium (with or without magnesium and potassium) was a consistent feature of each analysis. These and other components were considered in the context of lichen enrichment from crust-derived particulates, the marine aerosol, and certain anthropogenic sources. The high percentage of variation explained by the first five components strongly indicated that the major element sources contributing to this variation were considered. Nonmetric multidimensional scaling supported the principal component solution.There was considerable interspecific variation in the element content of the lichens. Univariate analysis of variance did not show any significant differences between the element content of Cladina arbuscula, C. rangiferina, and C. stellaris or any differences between Cetraria cucullata and C. nivalis on the basis of any single element. However, multiple discriminant analysis did show that the species mentioned could be distinguished (~ 90% discrimination) when all the elements were compared simultaneously. The discrimination between the Cladina spp. was based on the relative efficiency of these lichens in the accumulation of iron, scandium, titanium, and vanadium.
Factors influencing zoospore production by Phytophthora cinnamomi in axenic cultui
Authors: Schoulties Calvin L. , Baker Kenneth F. , Sabersky-Lehmann Carol
Published: April 2011

Factors and procedures found to increase the quantity and consistency of axenic zoospore production in a selected isolate of Phytophthora cinnamomi were (i) the use of single-zoospore cultures of uniform size that were between 48 and 72 h old; (ii) thorough washing of mycelial mats at the time of sporangium induction to remove nutrients; (iii) agitation of the sporulation medium (mineral salt solution) 24 h after the initial induction; (iv) standardization of the volume of the sporulation medium; (v) adequate removal of the sporulation medium and replacement with distilled water before triggering zoospore release; and (vi) placement of colonies that had been induced to sporulate under light. The addition of a purified sporangium stimulatory substance to mycelial mats which had been induced to sporulate enabled the fungus to sporulate under conditions which normally suppressed sporulation in vitro. In the presence of this stimulatory substance, the fungus sporulated prolifically in darkness and with limited quantities of added nutrients. Other isolates of P. cinnamomi responded in a similar manner to many of these factors and procedures.
Modifications ultrastructurales de graines d'Allium cepa, hydratées ou non, soumises à de basses températures (−196 °C)
Authors: Colson Monique
Published: April 2011

Osmic fixation was used in an ultrastructural study of Allium cepa seeds, both in the quiescent state and at the beginning of imbibition, in order to complete earlier observations made after glutaraldehyde fixation. In embryonic radicles, various groups of weakly stained lamellar structures looked like endoplasmic reticulum profiles. In these quiescent tissues, osmic fixation revealed many vesicles which appeared to be atypical elements of endoplasmic reticulum.In the first few hours of imbibition, reactive structures were more numerous and more diverse. Cisternae and vesicles of endoplasmic reticulum became typical looking, such as classically described in active tissues of other species.When Allium cepa seeds were treated with liquid nitrogen (−196 °C), induced structural alterations depended on the initial state of hydration. Lamellar systems underwent morphological changes. Osmic fixation showed the presence of numerous opaque globules throughout the cytoplasm. These globules seemed to derive from cisternae that appeared to have become fragmented during freezing. [Journal translation]
Localisation cellulaire du calcium chez le champignon Ascomycète Sphaerostilbe repens par analyse directe à la microsonde électronique
Authors: Botton B. , Fourcy A. , Bossy J. P.
Published: April 2011

In the Ascomycete Sphaerostilbe repens, where calcium is necessary for the differentiation of aggregated organs, microlocalization of calcium was determined both in undifferentiated mycelium and in rhizomorphs. In every case cell walls contained high calcium concentrations. Mucilaginous compounds around cells also contain this cation but at a lower level.In the vegetative mycelium, Woronin bodies and particularily mitochondria accumulated calcium. In the vacuoles of rhizomorph cells, calcium concentration was low.Calcium location in cell walls suggests that this element could play a role in cell-to-cell adhesion.
Induction de l'organogénèse sur des cals de Vicia faba minor provenant d'apex
Authors: Galzy Rose , Hamoui Mahmoud
Published: April 2011

In vitro cultivated plants of Vicia faba minor were propagated by microcutting and used as the initial material for these experiments. Shoot tips were first cultivated on callus-inducing media. The transfer of calluses to media containing lower levels of growth substances resulted, in some instances, in the neoformation of roots and shoots. Rooted plantlets were then obtained from these shoots.Auxins (α-naphthaleneacetic acid (NAA) and 2,4-dichlorophenoxyacetic acid (2,4-D)) and cytokinins (6-benzylaminopurine (6-BAP) and 6-furfurylaminopurine (kinetin)) clearly influenced the rate of callus growth and the capacity for organogenesis. They were mixed together to give four callus-inducing media, each containing an auxin (1 mg/L) and a cytokinin (5 mg/L). The media tested for organogenesis contained in each case the same growth substances as the initiation medium but the concentration of auxin and cytokinin was reduced and their ratio modified. Shoot differentiation occurred only when the auxin used was NAA. The most effective combination for shoot formation was the following: 0.1 mg/L NAA and 0.5 mg/L 6-BAP.
Fusarium moniliforme var. intermedium, a new variety in the Liseola section
Authors: Neish G. A. , Leggett M.
Published: April 2011

Fusarium moniliforme var. intermedium var.nov. characterized by the production of both catenate microconidia and polyphialides is described and some nomenclatural problems concerning the Liseola section of Fusarium are discussed.
Effect of cambial dormancy state on the transport of [1-14C]indol-3-ylacetic acid in Abies balsamea shoots
Authors: Little C. H. A.
Published: April 2011

Dormant attached or detached shoots of balsam fir were naturally or artificially chilled to induce different states along the rest–quiescence continuum. At the end of the chilling pretreatment, the shoots either were left intact or were debudded and treated with indol-3-ylacetic acid (IAA). The shoots were placed under controlled-environment conditions favorable for growth, and at intervals thereafter, a pulse of [1-14C]IAA was applied to the shoot apex. Measured at the end of the chilling pretreatment, [14C]IAA velocity and flux decreased with increasing duration of chilling (i.e., as rest graded into quiescence). The time required to commence cambial growth and to attain maximum rates of cambial activity and [14C]IAA transport also decreased as rest changed to quiescence. Transport in actively growing shoots exceeded that in quiescent shoots, but was similar to that in resting shoots. The [14C]IAA pulse moved basipetally as unchanged IAA, was blocked by a bark + cambium girdle, and was inhibited by abscisic acid and long-term application of exogenous IAA. The results indicate that: (1) the long-distance, cambium-located, IAA transport system demonstrated in dicotyledonous species also operates in conifers, (2) during the dormant period changes occur in [14C]IAA transport and in the cambial response to exogenous IAA, (3) the change in [14C]IAA transport is the result of change in the transporting capability of cells in the cambial zone, and (4) the change in [14C]IAA transport is not the cause of the differential response of quiescent and resting cambia to exogenous IAA.
A North American isolate of Coprinus kubickae associated with a superficial fairy ring
Authors: Redhead S. A. , Smith J. Drew
Published: April 2011

Coprinus kubickae is reported from North America for the first time. The fungus was associated with a superficial fairy ring on turf of Agrostis stolonifera in Saskatchewan but proof of pathogenicity was not definite.
Problems arising from a Münch-type pressure flow mechanism of sugar transport in phloem
Authors: Fensom D. S.
Published: April 2011

This, paper reviews five premises which underlie the simple Münch-type pressure-flow mechanism of sugar transport in plants from source to sink. The validity of each of these has been found experimentally to be in doubt in functioning sieve tubes, but at least four of the five should pertain if the simple pressure-flow theory is valid. A brief survey of alternate suggestions of mechanisms for sugar transport is given in the light of recent findings; in particular, models which reconcile ATP-assisted flow with pressure flow are discussed.
Physiological factors affecting the accumulation of L-citrullinyl-L-arginine in Chondrus crispus
Authors: Laycock M. V. , Morgan K. C. , Craigie J. S.
Published: April 2011

Experiments in tank cultures with Chondrus crispus Stackh. have shown that the dipeptide citrullinyl-arginine can accumulate to high concentrations when plants are supplied with nitrate or ammonia at low temperatures. With nitrate only, low light intensity can limit the rate of accumulation of the dipeptide which, in the natural habitat, can affect plants in midwinter or in shade. In nature, citrullinyl-arginine accumulates throughout the winter months when nitrate is available and growth is restricted by low temperatures. Nitrate levels in the sea fall rapidly in the spring at a time when conditions for growth are improving with increasing irradiance and temperatures. Nitrogen reserves sustain the plants and allow them to take advantage of favorable growth conditions.
Physiological studies on some isolates of Phytophthora palmivora and P. megakarya
Authors: Zoberi M. H. , Fessehatzion B. , Umebuani E. O. , Ugbu S. U.
Published: April 2011

Physiological studies were made of six isolates of Phytophthora from cocoa, three of the A2 mating type of P. palmivora (71, 78, and 29) and three of the A1 mating type of the recently described P. megakarya (9A, 75, and 10B). Many of these studies revealed a clear differentiation between the two species. In all experiments the growth rate of the isolates of P. palmivora was higher than that of P. megakarya. Sporulation was also found to be more efficient in P. palmivora. Sporangial initials appeared in cultures after a 24-h incubation at 25 °C in P. palmivora isolates and after a 72-h incubation in P. megakarya isolates. The period required for the full development of sporangia in all isolates was 48 h. Of the seven carbon compounds tested, glucose was best utilized by all the isolates. Phytophthora megakarya isolates grew better on lactose while those of P. palmivora grew better on glucose, sucrose, and maltose. Sporulation was not as efficient in isolates of P. megakarya as in those of P. palmivora; no sporulation on starch and sorbose occurred in 9A and very little in 75. On the six nitrogen compounds, isolates of P. palmivora generally grew better than those of P. megakarya. Glycine was preferred for growth by 9A and 71, while casein hydrolysate was favoured by 75 and 78. For sporulation, asparagine proved to be the best for P. palmivora and ammonium tartrate for P. megakarya. Glutamic acid was not suitable for sporangial production in the isolates of P. megakarya; on the other hand in the isolates of P. palmivora sporangia developed freely on this compound. Solid media was used to detect the production of the extracellular enzymes. Amylase and urease were detected only in the isolates of P. palmivora, while lipase, DNAase, protease, and phosphatase were detected in all the isolates tested.
Apical dominance in the rhizome of Agropyron repens: the influence of humidity and light on the regenerative growth of isolated rhizomes
Authors: McIntyre Gordon I.
Published: April 2011

The influence of humidity and light on the regenerative growth of isolated five-node segments from rhizomes of Agropyron repens was investigated under controlled conditions. When the rhizomes were incubated in the dark at 20 ± 1 °C shoot growth at the apical node was significantly reduced by each 0.5% reduction in relative humidity between 100 and 98.5% and at 98.0% growth at all nodes was completely inhibited. The restriction of these effects to the apical end of the rhizome (nodes 1 and 2) was attributed to their interaction with the basipetal gradient of decreasing N concentration previously identified as one of the causal factors in the polarity of bud activity. Bud inhibition at a relative humidity of 98% was eliminated by supplying water through the basal end of the rhizome. This treatment also released the buds from the inhibition induced by the exposure of the rhizomes to light. Since the uptake of water by the rhizomes was also greater in the light than in the dark it was postulated that the light-induced inhibition of bud growth was due to a reduction in rhizome water potential mediated by an increase in the rate of transpiration.
The Progymnospermopsida: the construction of a concept
Authors: Stewart Wilson N.
Published: April 2011

This is a review of the discovery, characteristics and phylogenetic importance of the Progymnospermopsida. The origin of this group from the Devonian Rhyniopsida is briefly discussed as is the evidence that supports the relationship between the two principal orders, the Aneurophytales and Archaeopteridales. Differing interpretations about the origins of cycadophytes and coniferophytes from progymnosperms also are presented. It is recommended that the old class Gymnospermae be reinstated as a natural unit of vascular plant classification for those seed plants whose origins are with the Progymnospermopsida.
The distribution of silicon in the adventitious roots of the bamboo Sasa palmata
Authors: Bennett Daphne M. , Sangster A. G.
Published: April 2011

Samples taken from the proximal end and 10 cm below the proximal end, of adventitious roots of mature Sasa palmata plants, were investigated using the scanning electron microscope and electron-probe microanalyzer.High levels of silicon were confined to the endodermis. It was present within the inner and outer tangential walls, and also the radial walls. The results are discussed in relation to the anatomy of the tissues, and the possible functions of silicification.
Histochemical observations on apothecia, permanently vegetative hyphae, and sclerotia of Pyronema domesticum with special reference to light
Authors: Moore-Landecker Elizabeth
Published: April 2011

The Discomycete, Pyronema domesticum (Sow. ex Gray) Saccardo was cultured on an inorganic salts medium, as well as on potato dextrose agar (PDA), and exposed to different light regimens. Permanently vegetative hyphae were obtained on PDA cultures illuminated with cycles of 12 h light: 12 h darkness, while abnormal confluent padlike apothecia were formed on PDA in constant light and sclerotia were formed in PDA cultures that were incubated in the dark. Apothecia were formed on the inorganic salts medium and exposed to different light regimens that favored either overall apothecial development or primarily favored development of the ascogenous or sterile system. Histochemical tests were conducted on permanently vegetative hyphae, sclerotia, and apothecia to localize glycogen, carbohydrates, mucilage, protein, DNA, RNA, lipids, and carotenes. Exposure to light stimulated synthesis of DNA, lipid, glycogen, and other carbohydrates. Favorable development of morphologically normal ascogenous hyphae and asci was positively correlated with moderate to high levels of DNA, RNA, protein, and PAS-positive substances (excluding glycogen). Conversely, favorable development of the morphologically normal sterile system was not positively correlated with higher levels of any components, but excessive accumulation of glycogen was associated with its unfavorable, limited development. Massive accumulations of protein, phospholipids, DNA, glycogen, mucilage, and other carbohydrates were observed in the nonsporulating asci in cultures maintained in the dark for 4 days before being exposed to constant light, or in the permanently vegetative hyphae.
The effects of shade on growth, development, and resource allocation patterns of three species of foxtail (Setaria)
Authors: Lee Susanna M. , Cavers Paul B.
Published: April 2011

Three weedy foxtail species, Setaria glauca (L.) Beauv., S. verticillata (L.) Beauv., and S. viridis (L.) Beauv. occur in southwestern Ontario. Plants of the three species were grown in pure stands in the open and under one, two, or three layers of cheesecloth which transmitted 71, 40, and 19% of incident insolation, respectively. Six harvests were taken between July and September in which height, tiller number, dry weight of component parts, and leaf area were determined for randomly selected plants of each species. In unshaded conditions, S. verticillata was the tallest species and had the greatest total dry weight per plant. However, this species was the most adversely affected by shade, with significant reductions in tiller number, biomass production, and reproductive effort with increasing shade. Setaria viridis and S. verticillata exhibited a relative increase in allocation to leaves with increasing shade while S. glauca had a relative increase to stems, indicating different strategies in response to shade. The apparent lower tolerance of shade in S. verticillata may help to explain the comparative rarity of this species in southwestern Ontario.
Copper requirement of a copper-tolerant isolate of Scenedesmus and the effect of copper depletion on tolerance
Authors: Stokes P. M. , Dreier S. I.
Published: April 2011

A copper-tolerant isolate of Scenedesmus from Sudbury, Ontario, cultured in medium completely lacking copper, lost its ability to grow at high copper concentrations after 10 generations. The change was sudden in onset and relatively rapid. The algae had previously been maintained on medium with micronutrient levels of copper and had retained their tolerance over 7 years of laboratory culture.The tolerance of the copper depleted cells to nickel and cobalt also decreased. Their tolerance to cadmium and silver was unchanged by copper depletion. The situation for zinc tolerance was less clear, but there was no significant decrease over the range tested.When copper-depleted cells were cultured in complete medium with micronutrient levels of copper, copper tolerance increased after four divisions and recovered to the original state after eight divisions. Plate assays indicated that all of the cells in the culture were recovering i.e., this was not a reselection of a few tolerant cells.The results are discussed in terms of possible tolerance mechanisms, and their implications for the occurrence of multiple or cotolerance.
In vitro regeneration of chlorophyll chimeras in tomato (Lycopersicon esculentum)
Authors: Seeni S. , Gnanam A.
Published: April 2011

Explants of hypocotyl, cotyledon, and hypocotyl-derived calli of homozygous (xa-2/xa-2) green, heterozygous (Xa-2/xa-2) yellow–green, and homozygous (Xa-2/Xa-2) albino seedlings of Lycopersicon esculentum Mill. were induced to regenerate plants in vitro on Murashige-Skoog agar medium. Approximately 10–15% of the regenerants obtained from cultures of heterozygous individuals were of the variegated type. Homozygous lines green (xa-2/xa-2) and albino (Xa-2/Xa-2) however, did not regenerate any chimeral plants.
Effect of humidity and light periods on infection and sporulation of Peronospora viciae on Pisum sativum
Authors: Singh H.
Published: April 2011

Plants grown in high relative humidity (RH > 90%) before inoculation supported more sporulation than those kept in drier (RH < 30%) conditions. Sporulation of Peronospora viciae (Berk.) Casp. on Pisum sativum (Berk.) Casp. cv. Superb was lower on plants kept under continuous light for 2 weeks before inoculation than on those maintained in a 12 h light: 12 h dark photoperiod. Treatments involving longer photoperiods after inoculation resulted in greater sporulation (intensity) than those where inoculation was followed by an extended dark period. A minimum of 6 h of high humidity (RH > 90%) in the dark was required to initiate sporulation. However, this period was reduced to 3 h if replaced by lower humidity conditions (RH 65%).
Cultural characteristics, pathogenicity predictions, and pathogenicity tests for some isolates of Ceratocystis ulmi
Authors: Hindal D. F. , Harner E. J. , MacDonald W. L.
Published: April 2011

Ceratocystis ulmi isolates of known pathogenicity were culturally characterized on a defined synnema production medium (SPM) and American elm wood disks. More aggressive isolates generally produced more synnemata and mycelial pigment on SPM and more synnemata on the wood disks than less aggressive ones. There was no relationship between pathogenicity and radial growth or aerial mycelium production on SPM. Multivariate discriminant analyses on synnema and pigment production and radial growth on SPM and univariate discriminant analyses on synnema production on the wood disks accurately classified the isolates of known pathogenicity into their respective pathogenicity classes. Isolates of unknown pathogenicity also were characterized on SPM and elm wood disks, and pathogenicity predictions made for them using discriminant analyses. Five isolates predicted to be less aggressive were selected for pathogenicity testing, and four were less pathogenic in American elm than a known more aggressive isolate.
Histology and histochemistry of elongating needles of Pinus strobus subjected to a long-duration, low-concentration exposure of sulfur dioxide
Authors: Percy K. E. , Riding R. T.
Published: April 2011

Two-year-old seedlings of Pinus strobus were grown from budbreak to bud set (11 weeks) in air containing 132 ± 26 μg SO2∙m−3. Histological and histochemical effects on elongating needles were examined. Cellular injury was restricted to mesophyll parenchyma. Affected cells manifested a progressive alteration of protoplast staining proportional to the degree of injury. Total carbohydrates and plastids aggregated at cell walls. Total proteins and proteins containing sulfhydryl–disulfide groups decreased. Phospholipid staining in the plasmalemma – cell wall region appeared reduced. Succinic dehydrogenase activity was enhanced and was apparent longer in injured cells. Needle ontogeny was slowed in fumigated seedlings. There were no significant differences in external growth parameters after 11 weeks. The injury can, therefore, be classified as latent or hidden. The SO2 effects could contribute to a growth reduction in successive increments.
Photosynthesis and transpiration in large forest-grown Douglas-fir: interactions with apical control
Authors: Leverenz Jerry W.
Published: April 2011

Net photosynthesis, transpiration, and stomatal and residual conductances for current-year shoots of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) were measured in an open gas exchange system. Terminal shoots of branches and branchlets had larger stomatal and residual conductances, and net photosynthetic and transpiration rates than neighboring lateral shoots under conditions which did not limit gas exchange. The differences between terminal and lateral shoots occurred in both exposed and shaded branches and in trees of different dominance classes. For most of the study, current-year lateral shoots were lighter green than terminal shoots. There were no significant differences in shoot water potential or in the microenvironment between terminal and lateral shoots.Effects of apical control on gas exchange rates were strong in shoots subtending the dominant terminal shoot. These effects were not apparent four whorls from the terminal shoot, in agreement with the hypothesis that apical control can not be exerted at long distances from terminal shoots.