bluuebunny/crossref_metadata_2025 huggingface dataset:
Chemical composition of epicuticular wax in cabbage plants grown in vitro
Authors: Sutter Ellen
Published: September 2008

The chemical composition of epicuticular wax from cabbage plants grown in vitro was compared with that from plants grown in a greenhouse. There was a greater percentage of polar compounds (fatty acids, primary alcohols, aldehydes, and esters) and less alkanes and secondary alcohols in wax from cultured plants relative to those from greenhouse plants. Homologues in each class were more evenly distributed and had a greater range of chain lengths in wax from cultured plants. The high proportion of polar components in wax from cultured plants might be a factor in water loss when the plants are transferred to the greenhouse. Possible explanations for the altered wax composition in plants grown in vitro include increased relative humidity and decreased light intensity characteristic of in vitro conditions.
Conostoma williamsonii n. sp., a lagenostomalean ovule from the Pennsylvanian of the Illinois Basin
Authors: Stubblefield Sara P. , Rothwell Gar W. , Taylor Thomas N.
Published: September 2008

Ellipsoid lagenostomalean ovules previously regarded as Conostoma oblongum are recognized as a distinct species based on shape, number of vascular bundles, and histological features of the integument. Conostoma williamsonii n. sp. is shorter and broader than C. oblongum and possesses a larger number (eight or nine) of vascular bundles. Features of the integument are similar to those of C. oblongum and C. chappellicum and include a smooth outer margin and a two-zoned sclerotesta. Conostoma williamsonii increases our understanding of the diversity of lagenostomalean ovules during the Middle Pennsylvanian and calls to question the occurrence of C. oblongum in currently known North American coal-ball floras.
Variations du contenu lipidique occasionnées par la carence en pyridoxine du milieu nutritif de Ceratocystis ulmi
Authors: Dalpé Y.
Published: September 2008

Pyridoxin deficiency of the synthetic growth medium results on four of the five strains of the studied Ceratocystis ulmi in an increase (6.9 to 18.8%) of the lipid content of the mycelium. This increase mainly affects the neutral lipid fraction. The analysis of fatty acids shows a significative decrease, both in the neutral and the polar lipid fraction, of the polyunsaturated fatty acid content, and in some cases the total disappearance of the linolenic acid.
Endothiella aggregata n. sp. (Phialostromatineae) on western conifers
Authors: Funk A.
Published: September 2008

Endothiella aggregata n. sp. is a red, clustered, stromatic coelomycete that is associated with diseased bark of various western conifers.
A study of the factors affecting morphological differentiation in a population of Pinus ponderosa
Authors: Maze Jack
Published: September 2008

Trees are among the most variable of organisms, the result, it would seem, of fusion between gametes from genetically different individuals. Genetically different individuals may result from selection, causing population differentiation over small geographic areas or selecting for different individuals in different climatic regimes that prevailed during different years. However, selection is not necessary to explain the existence of genetically different individuals. The evolutionary theory of Wiley and Brooks predicts an increase in variation as a consequence of natural laws pertaining to increasing disorder. The effect of habitat differences, trees, age, size of trees, and past climate, as evidenced by tree ring site summaries, on pattern of variation in needle variables was estimated by calculating the percentage of variation in principal components analysis axis scores for which each factor accounts. In all comparisons made, the greatest percentage of variation was accounted for by trees and an error term, indicating selection has little impact on patterns of variation. While it may be argued that relevant selective factors were missed, it should be pointed out that such arguments can lead to the unacceptable stance of explaining away unpopular results by asserting that the important elements were not measured. A large percentage of variation that is apparently unaccounted for by selection is a prediction that would follow from the theory of Wiley and Brooks.
Studies on the Stellaria longipes complex: phenotypic plasticity. I. Response of stem elongation to temperature and photoperiod
Authors: Macdonald S. Ellen , Chinnappa C. C. , Reid David M.
Published: September 2008

Clonal material of one genotype of Stellaria longipes Goldie s.l. was used to study the effects of photoperiod and temperature on stem elongation. Temperature is the more important influence for induction of stem elongation. Photoperiod exerts a lesser effect. A combined synergistic effect of temperature and photoperiod is in operation. A minimum number of heat degree-days, equivalent to about 3 days at 22:18 °C (day: night) temperature, is required to induce elongation. A minimum period of "winter cold," equal to 50 short, cold days is required for maximum elongation in subsequent warm, long days. Some elongation will occur in continuous long, warm days, but a short cold period is essential for flowering. After 8 months in short, cold days flowering will occur without elongation.
The effect of humidity, root excision, and potassium supply on hypocotyl elongation in dark-grown seedlings of Helianthus annuus
Authors: McIntyre Gordon I. , Boyer John S.
Published: September 2008

When seedlings of Helianthus annuus L. were grown in the dark with their roots in vermiculite saturated with distilled water the rate of elongation of the hypocotyl was significantly increased by increasing the relative humidity around the shoot from approximately 25 to 100%. This response was correlated with a reduction in transpiration rate of approximately 95% and with increases in the water potential and cell turgor in the growing region. Measurements with a transducer revealed very rapid growth responses to changes in humidity, usually preceded by a variable period of growth oscillations. Excision of the roots, either in water or in air, induced an immediate increase in rate of elongation at low humidity, but at high humidity this response was delayed and markedly reduced. The growth rate was significantly increased by supplying 10 mM KCl to the roots at both high and low humidity. The response to K was slower than the response to humidity and was correlated with a significant reduction in the osmotic potential of the growing region. A growth response was first detected approximately 45 min after the application of K to the roots and 10 min after application to the shoot. These results arc consistent with the hypothesis that, in the intact plant, stem elongation is largely controlled by the interacting effects on cell turgor of transpiration-induced negative pressure potential in the apoplast and the osmotic potential of the growing cells.
Study of tobacco mosaic virus in vitro disassembly by sucrose density gradient centrifugation and agarose gel electrophoresis
Authors: Hogue Richard , Asselin Alain
Published: September 2008

In vitro disassembly of tobacco mosaic virus (TMV) strains U1, U2, U4, U6, and U7 with alkali and urea was studied by sucrose or sucrose–dimethylsulfoxide (DMSO) density gradient centrifugation and by agarose gel electrophoresis. All strains gave similar decapsidation patterns with both agents when partially stripped virus particles (PSVs) were analyzed by sedimentation and electrophoresis. However, U6 was more sensitive to decapsidation than the other strains and U2 exhibited resistance to decapsidation. Agarose gel electrophoresis of TMV decapsidation products allowed the detection of several classes of PSVs in addition to aggregation products involving PSVs and monomer particles. Agarose gel electrophoresis is thus very rapid and useful for analysis of TMV disassembly products especially when aggregation phenomena and kinetic studies with numerous samples are considered.
Acid rain effects on foliar histology of Artemisia tilesii
Authors: Adams C. M. , Dengler N. G. , Hutchinson T. C.
Published: September 2008

The present study describes the effects of simulated acid rain (pH 2.5–5.6) on foliar histology of an arctic herb, Artemisia tilesii Ledeb., which is remarkably tolerant to naturally occurring atmospheric acidity at Smoking Hills, N.W.T. Plants were exposed to simulated acid rain twice weekly for 4 weeks in exposure chambers in the greenhouse. Droplets as acidic as pH 2.5 caused limited macroscopic foliar damage. However, much greater damage was observed when sectioned leaf tissue was examined microscopically. On leaves having no injury visible to the unaided eye, small lesions consisting of one to three collapsed epidermal cells were observed in scanning electron micrographs and in cleared leaves after exposure to rain of pH 3.0 and 3.5. Stomata remained open in damaged areas of acid-sprayed leaves. Lesions most commonly developed from an initial collapse of a few adaxial epidermal cells, followed by progressive injury of underlying tissues. Palisade and spongy mesophyll cells underwent hypertrophic (abnormal cell enlargement) and hyperplastic (abnormal cell division) responses in the region adjacent to severely collapsed tissue, causing reduced intercellular spaces. These effects isolated the injured areas from adjacent healthy tissues, and resembled wound periderm responses to fungal pathogens and to mechanical irritation. This response may be one mechanism of limiting acid rain damage.
Bud development in mountain hemlock (Tsuga mertensiana). II. Cone-bud differentiation and predormancy development
Authors: Owens John N.
Published: September 2008

Seed cones of Tsuga mertensiana (Bong) Carr. occur terminally on distal lateral branches and form from the differentiation of a terminal, previously vegetative apex, into a seed-cone apex. Pollen cones commonly occur on lateral branches and form from the differentiation of an undetermined axillary apex about 6 weeks after axillary bud initiation. Pollen cones also occasionally occur terminally. All cone buds began differentiation in late July after bud-scale initiation was complete and at about the end of lateral shoot elongation. Seed-cone buds initiated bracts and ovuliferous scales, but not ovules, before they became dormant at the end of October. Pollen-cone buds initiated all microsporophylls by early September. Microsporangia containing microspore mother cells differentiated before pollen-cone buds became dormant in mid-October. The time of cone-bud differentiation is related to vegetative bud and shoot development. The time and method of cone-bud differentiation is discussed in relation to T. heterophylla and other conifers having similar bud development.
Races of Fusarium oxysporum f. sp. apii in California and their genetic interrelationships
Authors: Puhalla John E.
Published: September 2008

Other researchers distinguished two races of Fusarium oxysporum f. sp. apii based on virulence tests; race 1 attacked only yellow celery varieties, whereas race 2 attacked both yellow and green types. In the present study, a third race, race 3, was found which attacked only green celery. Three laboratory tests were devised that identified these three races without recourse to virulence tests. The laboratory-based criteria included colony size on a sorbose-containing medium, allozymic differences for the enzyme acid phosphatase, and heterokaryon, or vegetative, incompatibility. These laboratory tests also tentatively defined two additional races, 2E and 3E, and they indicated that some avirulent strains isolated from celery were attenuated variants of all three races. Race 1 was clearly unrelated to race 2, and therefore the one did not arise from the other. However, races 2 and 3 appeared to be closely related. Strains of these two races were genetically very homogeneous and could be clonal derivatives of a single progenitor. Races 1 and 2E, however, each represented a group of genetically diverse strains. So far only races 2 and 3 have been found in California.
Colonization by oak seedlings into a heterogeneous successional habitat
Authors: Harrison Janet S. , Werner Patricia A.
Published: September 2008

The pattern of oak (Quercus velutina L. and Quercus alba L.) seedling establishment in relation to ground-cover vegetation was examined over a 5-year period in a 30-year Michigan old field. Three types of vegetation cover were identified: primary patches were areas of bare ground or those covered by moss, lichen, or a moss–lichen matrix over mineral soil (sand); transitional patches were areas of herbaceous vegetation over a ground layer of primary vegetation; secondary patches were areas of herbaceous perennials and (or) grasses over organic soil. In 1976, 27% of the study field was covered with primary patches but by 1980 only 8% of the area was covered with primary patches. Age distribution data indicated that oaks began colonizing the field about 15 years after abandonment; lack of seed input to the field or inability of seedlings to survive beyond 15 years in this field could account for the apparent absence of colonization in the first 15 years. Oak seedlings colonized principally the primary patches: 84% of 1-year-old seedlings were found in primary patches in 1976 and 59% of 1-year-old seedlings were found in primary patches in 1980, despite the small proportion of the field covered by primary patch types. Older seedlings (>7 years) were found principally in transitional and secondary patch types as the primary patch types became transitional and secondary types. There are indications that the appearance of acorns on primary patch types is due to blue jays which preferentially disperse acorns to open ground cover. In contrast, growth rates of seedlings were greatest in secondary patches and lowest in primary patches. The study suggests that oak seedlings invading an abandoned field become first established in bare ground but then survive only if the surrounding vegetation invades the microsite.
The pollination mechanism of Sitka spruce (Picea sitchensis)
Authors: Owens John N. , Blake Margaret D.
Published: September 2008

The development and function of the pollination mechanism and the optimal time for pollination are described for Sitka spruce (Picea sitchensis (Bong.) Carr.). After winter dormancy, the rudimentary integument overgrew the nucellus and formed two long micropylar arms. Soon after seed-cone buds burst, the epidermal cells on the micropylar arms secreted mucilage droplets to which pollen adhered. The ultrastructure of mucilage droplet secretion is described. After 6–8 days a pollination drop formed from the nucellus. This filled the space between the micropylar arms and picked up any pollen which adhered to the arms or landed on the pollination drop. The pollination drop was then withdrawn carrying pollen into the micropyle. The secretory cells on the micropylar arms then autolyzed and a large mucilage plug sealed the micropyle and filled the space between the withered micropylar arms. Conelets closed and became pendant. Pollen germinated and pollen tubes formed about 2 weeks after pollination ended. Conelets enclosed in pollination bags were open and receptive for about 10 days, but the optimal time for pollination was 6 to 8 days after cone buds burst. This coincided with the time of pollination-drop formation.
The classification of Spizellomyces, Gaertneriomyces, Triparticalcar, and Kochiomyces (Spizellomycetales, Chytridiomycetes)
Authors: Barr D. J. S.
Published: September 2008

A classification is given for those Chytridiomycetes with monocentric and eucarpic growth forms, endogenous sporangium development, and multipapilliated sporangia that are now known in culture. These belong to six genera which are classified on unique ultrastructural characteristics of the zoospore; however, for convenience of routinely distinguishing these genera, a key is given based on characters detectable by light microscopy. Eight species are described for Spizellomyces, which include S. punctatus (Koch) D. Barr; S. plurigibbosus (D. Barr) comb, nov.; S. kniepii (Gaertner) comb, nov.; S. palustris (Gaertner) comb. nov.; S. acuminatus (D. Barr) comb. nov.; S. dolichospermus sp. nov.; S. lactosolyticus sp. nov.; and S. pseudodichotomus sp. nov. There are two species in Gaertneriomyces: G. semiglobiferus (Uebelmesser) D. Barr and G. tenuis sp. nov. Triparticalcar arcticum (D. Barr) D. Barr and Kochiomyces dichotomus (Umphlett) D. Barr are monotypic genera. Criteria for classifying these fungi in culture are discussed. Rhizophydium and Karlingia are included in the generic key but are not treated at the specific level. This new classification is intended strictly for cultures and neither augments nor replaces earlier and more classical systems.
Initiation and morphological development of somatic embryoids from barley cell cultures
Authors: Kott L. S. , Kasha K. J.
Published: September 2008

Somatic embryogenesis was induced in callus previously initiated from immature embryos of barley. These cultures ranged in age from 6 weeks to 30 months. Embryoids were readily initiated from homogenized suspension-grown aggregates when plated on modified B5 media with 2,4-dichlorophenoxyacetic acid. Low concentrations (0.1 and 0.05 mg∙L−1) of abscisic acid promoted further maturation of embryoids, while gibberellic acid (1 mg∙L−1) and kinetin (0.1 mg∙L−1) were used in the media to encourage embryoid germination. The development of somatic embryoids from initiation through maturation and germination is described.
A practical treatment of the Solidago gigantea complex
Authors: Morton Gary H.
Published: September 2008

The Solidago gigantea complex is usually treated in floristic works as being composed of a single species with two infraspecific taxa: var. gigantea and var. serotina. Recent studies by Beaudry revealed that the complex is composed of individuals of three different chromosome numbers. He proposed that the individuals at each ploidy level be treated as belonging to separate species: S. gigantea, 2n = 18; S. serotina, 2n = 36; and S. shinnersii, 2n = 54. Chromosome counts reported in this paper of individuals of the S. gigantea complex from a wide geographic range verify the existence of the three different ploidy levels. Evaluation of the morphological characters of these vouchers, however, shows that plants with different chromosome numbers cannot be consistently separated using morphological characters. It is proposed, therefore, that the complex be treated as a single species without any infraspecific categories.
Pollen morphology in Dodartia, Lancea, Leucocarpus, and Mazus and an analysis of pollen morphotypes in the Mimuleae (Scrophulariaceae)
Authors: Argue Charles L.
Published: September 2008

The pollen grains of Dodartia, Lancea, Leucocarpus, and Mazus are single, radially symmetrical, isopolar, and suboblate to prolate with trizoniaperturate ectocolpi; the colpus membranes show various patterns of transverse rupturing but most frequently have a single, equatorial rupture. The exine is composed of a semitectate sexine 2, a simplicolumellate sexine 1, and a frequently foveolate to perforate nexine, thinner than the sexine. Data from the present and earlier studies on the Mimuleae are analyzed statistically to establish a specific set of correlated morphological characters with discriminatory value in the definition and delimitation of major pollen types for the tribe. Interspecific and intergeneric palynological variation among tricolporate Mimuleae is assessed and taxonomic implications of the pollen data are discussed.
Influence of temperature and water potential on growth of Botrytis allii
Authors: Alderman S. C. , Lacy M. L.
Published: September 2008

Water potentials for optimum growth varied with temperature and with the material used to alter water potential. On prune extract – lactose – yeast extract (PLY) agar adjusted with KCl, sucrose, NaCl, or polyethylene glycol (PEG) 8000, growth rates were optimal at 20 or 25 °C and at water potentials of −5 to −10 bars (1 bar = 100 kPa). At 30 °C growth rates were optimal at −35 to −45 bars in the presence of KCl or sucrose and at −10 to −20 bars with NaCl or PEG 8000. Radial growth rates in dried onion leaves, adjusted to various water potentials over salt solutions in sealed chambers, corresponded to those on PLY media adjusted to the same water potentials with KCl or sucrose. Growth was halted at water potentials below −95 to −100 bars in onion leaves or in PLY agar containing KCl or sucrose osmotica, but it was halted at −50 to −60 bars in the presence of NaCl or PEG 8000. Growth of Botrytis allii in onion bulb tissue was optimal at 20 °C. Extent of bulb colonization increased linearly with the logarithm of increasing inoculum concentrations applied to small wounds in bulbs. Survival of B. allii in dead leaf tissue declined rapidly after 3 and 9 days at 37 and 32 °C, respectively.
Growth and fungal persistence by Quercus rubra inoculated with ectomycorrhizal fungi and planted on a clear-cutting and strip mine
Authors: Beckjord Peter R. , McIntosh Marla S.
Published: September 2008

Quercus rubra seedlings were grown in a greenhouse in media inoculated with and without vegetative hyphae of the ectomycorrhizal fungi Pisolithus tinctorius, Cenococcum geophilum, Scleroderma auranteum, and Rhizopogon nigrescens. Some seedlings were also inoculated with basidiospores of P. tinctorius and S. auranteum in the greenhouse. Rhizopogon nigrescens did not infect the seedlings during greenhouse production. Seedlings were planted and grown for two seasons on clear-cut and strip-mine sites. Some nonmycorrhizal seedlings were inoculated with basidiospores at planting. Seedling growth after one season on the clear-cut site was positive for all P. tinctorius, C. geophilum, and vegetative S. auranteum inoculations and significant differences in growth occurred among inoculation treatments. Root-core samples after one season showed that 80–100% of the seedlings on the clear-cut site had fungal persistence of assigned fungal species from all fungal inoculations except that no ectomycorrhizae were evident with seedlings field inoculated with basidiospores. Growth after two seasons on the clear-cut site was significantly different among treatments but not significantly different on the strip-mine site. Excavated root systems after two seasons showed that 0–100% of the seedlings on the clear-cut and strip-mine sites had fungal retention of assigned fungal species and ectomycorrhizae from basidiospore chip inoculations.
Interaction of Glomus fasciculatum and Pythium ultimum on greenhouse-grown poinsettia
Authors: Kaye J. W. , Pfleger F. L. , Stewart E. L.
Published: September 2008

Rooted Euphorbia pulcherrhima (poinsettia) plants, mycorrhizal with Glomus fasciculatum or nonmycorrhizal, were grown in a potting medium with a phosphorus (P) level of 5 μg/g, containing Pythium ultimum at 0, 38, 66, or 132 colony-forming units (CFU)/g dried soil. Fertilization was at 75 ppm nitrogen–potassium (N–K) weekly. Mycorrhizal root colonization was greater in plants grown in P. ultimum soil at each density than in plants grown in soil without P. ultimum, as determined by the root segment method and at 132 and 38 CFU/g as determined by the root length method. Plant height and foliar P content of mycorrhizal plants were greater than of nonmycorrhizal plants when grown in soil infested with 38 CFU/g P. ultimum. Foliar manganese (Mn) content was greater in nonmycorrhizal than mycorrhizal plants when grown in P. ultimum soil at each density. Mycorrhizal plants had lower final P. ultimum populations in rhizosphere soil than nonmycorrhizal plants when grown in soil infested with 38 CFU/g P. ultimum. Densities of Pythium ultimum were greater in rhizosphere compared with nonrhizosphere soil in the absence of mycorrhizae.
Ecological relationships of wild rice, Zizania aquatica. 3. Factors affecting seeding success
Authors: Lee P. F. , Stewart J. M.
Published: September 2008

Thirty-two sites were seeded with wild rice. Based on the number of panicles per square metre, production in the sites was categorized as commercial, marginally commercial, or unsuitable for commercial production. Discriminant analysis was used to derive two functions which explained these production differences. High values for the first discriminant function, which was interpreted as a factor of sediment phosphorus concentration and sediment type, separated the sites suitable for commercial production. The second discriminant function separated the remaining two categories on the basis of sediment type and light penetration through the water column. Those sites unsuitable for commercial production had higher values for this function than those sites which produced marginally commercial growth. Further research is needed into the spatial and temporal variations of the significant environmental variables before any recommendations can be made on the criteria for selecting potential wild rice sites.
Pénétration d'une endo-pectate lyase tritiée dans les cellules corticales de racines de courge
Authors: Vogt G. F. , Coulon J.
Published: September 2008

Erwinia carotovora produces pectate lyases (endo-PGTE) on sterilized beans hypocotyls. Two endo-PGTE fractions were isolated and purified by electrofocusing. The action of these enzymes on the ultrastructure of cortical cells of pumpkin roots was very similar to the action of the whole bacterium. Erwinia carotovora grown on tritiated amino acid supplemented medium produced [3H]endo-PGTE. By incubating the host tissues with 3H-labelled enzymes and by subsequent autoradiographic analysis it was possible to localize the endo-PGTE inside the cells. Thus, it was shown that the enzyme (the complete molecule or only a peptide part thereof) was transported towards the vacuole. It is suggested that the endo-PGTE acts on the filamentous polysaccharide extensions which bind the external surface of the plasmalemma to the cell wall.
Lipid acyl hydrolase of patatin
Authors: Racusen David
Published: September 2008

Patatin, the major protein of potato tubers, was copurified with lipid acyl hydrolase (LAH). The common identity of LAH and patatin was demonstrated by sodium dodecyl sulfate denaturation studies, isoelectric focusing, and the inhibition of LAH activity by patatin antiserum.
A method to isolate the female sexual cells of Larix decidua for cytological studies
Authors: Rohr R. , Bonga J. M.
Published: September 2008

A cytological squash technique to study megasporogenesis, egg formation, and proembryo formation in Larix decidua was developed. The middle lamellae of the cells were dissolved and the cytoplasm was cleared by treating the tissues with several combinations of glycerol, water, dimethyl sulfoxide, sodium bicarbonate, and potassium hydroxide at high temperatures. The nucelli, meiocytes, coenocytes, central cells, or eggs were excised in a drop of toluidine blue stain solution on a microscope slide. A coverslip was added and slight pressure was applied. Meiotic chromosomes stained darkly and displayed several structural details well. Metaphase 1 bivalents separated easily and clearly showed their chiasmata. Since meiocyte excision from nucelli was about 90% successful, the degree of synchrony in meiosis within cones could be determined. A few aborting tetrads were observed. Division of the central cell and egg formation could be followed in detail.
Pisum sativum cultivar effects on hydrogen metabolism in Rhizobium
Authors: Bedmar Eulogio J. , Phillips Donald A.
Published: September 2008

Data from 14 Pisum sativum L. cultivars establish that three pea genotypes, which were previously reported to affect net H2 evolution from root nodules in air and uptake hydrogenase activity of Rhizobium leguminosarum 128C53, are not unique. Two pea lines, 'JI1205' and 'Green Arrow,' produced very active uptake hydrogenase activity in strain 128C53, and essentially no H2 was evolved in air from root nodules capable of reducing 20 μmol C2H2 ∙ plan−1 ∙ h−1. Five other cultivars produced significantly lower uptake hydrogenase activities in the same bacterial strain and had much higher rates of net H2 evolution with similar C2H2-reduction capabilities. Parallel experiments with the same cultivars nodulated by R. leguminosarum 300, an organism with no convincing uptake hydrogenase activity in any pea line, showed that 'JI1205' and 'Green Arrow' had a significantly lower relative efficiency (RE) of N2 fixation (1 − (H2 evolved in air/C2H2 reduced)) than the other five cultivars. Developmental differences among the pea lines prevented any conclusion about the advantages or disadvantages of uptake hydrogenase activity for plant growth, but in general, cultivars with high uptake hydrogenase activity and low net H2 evolution grew more slowly than those evolving large amounts of H2.
Shoot development in Betula papyrifera. V. Effect of male inflorescence formation and flowering on long shoot development
Authors: Caesar J. Cartey , Macdonald Alastair D.
Published: September 2008

One-year-old vegetative and reproductive long shoots of Betula papyrifera Marsh, were collected from 40-year-old trees when leaves were fully expanded. Leaf areas were significantly reduced on shoots bearing developing male inflorescences; late leaves were affected most. Late leaves were thinner than early leaves on vegetative shoots and thinnest on reproductive shoots. The effect of developing male inflorescences was most pronounced on the specific leaf area of early leaves, suggesting that inflorescences are strong sinks for assimilates being exported by early leaves. Two-year-old vegetative and reproductive branches were collected just after bud burst to determine mean bud dry weight. These values were highest for buds on vegetative long shoots, lower for buds on reproductive long shoots, and lowest for buds on reproductive long shoots bearing female short-shoot buds. Formation of male inflorescences reduced the growth potential of buds. Female short-shoot buds on reproductive long shoots and pseudoterminal buds positioned below male inflorescences exhibited reduced growth potentials. Mean total early leaf areas measured 3 weeks after flushing showed similar trends. Thus, development and flowering of male inflorescences lowered the growth potential and vigour of axillary buds and reduced canopy expansion.
The penetration and growth of blue-stain fungi in the sapwood of lodgepole pine attacked by mountain pine beetle
Authors: Ballard R. G. , Walsh M. A. , Cole W. E.
Published: September 2008

The growth of blue-stain fungi was investigated in naturally blue-stained lodgepole pine (Pinus contorta var. latifolia Engelm.) sapwood. Events occurring at the leading edge of hyphal penetration were studied. Fungi are initially confined to the sapwood rays. Hyphae readily penetrate the primary cell walls of ray parenchyma cells and proliferate within. Hyphae also grow freely in the region of the middle lamella of the rays. Host cell walls are breeched mechanically by a penetration peg originating from an appressoriumlike structure. Eventually, hyphae enter tracheids by penetrating the primary cell walls of pinoid, half-bordered pit pairs. Within the tracheid, fungal hyphae grow in a longitudinal fashion, branching infrequently. Hyphae may pass from tracheid to tracheid via bordered pit pairs. Ensuing water stress and eventual tree death is discussed in light of histological evidence presented.
Dynamique de la végétation d'emprises de lignes de transport d'énergie
Authors: Darveau M. , Bellefleur P.
Published: September 2008

We made a preliminary study of the impact of phytocides on plant dynamics in the corridors of Hydro-Québec power lines. Three hypotheses were tested: the first assumed that the phytocides changed vegetation composition and structure in the corridors; the second assumed that the corridor under the power line favored the development of an ecotone at its border with the forest; the third assumed that the method used for initial cutting of the corridors (bulldozer or chain saw) affected the forthcoming vegetation for over 15 years. Vegetation was sampled on one control power line and four power lines maintained with mixtures of picloram, 2,4-dichlorophenoxyacetic acid, 2,4,5-trichlorophenoxyacetic acid, and sodium trichloroacetate. Multidimensional statistical analysis was used to show the underlying structure of the raw data and to test the hypotheses. We found out that phytocides are very efficient on woody species to the advantage of herbs, mostly grass, which invaded the corridors and created rather stable artificial communities. No significant ecotone was found at the border line of the corridors and the forest. The influence of the method for initial cutting of the corridors, although severe the first few years, disappeared after about 10 years under the action of the phytocides.
A role of cotyledons and sucrose in the differentiation of primary phloem fibers in hypocotyls of sunflower seedlings
Authors: Mukherjee Ilabanta , Yeung Edward C. , Reid David M.
Published: September 2008

Sucrose treatment of the hypocotyls of derooted 7-day-old sunflower seedlings stimulated growth of hypocotyls as measured by dry weight. The fresh weight of the hypocotyls was unaffected. Stimulatory effect of sucrose was much greater in the presence of the cotyledons than in their absence. Cotyledons also influenced the differentiation of primary phloem fibers in the hypocotyls of seedlings, although when cotyledons were removed, induction of some phloem fiber differentiation was possible by sucrose treatment alone. In the presence of the cotyledons, sucrose in the concentrations of 0.025 and 0.05 M greatly enhanced primary phloem fiber differentiation and secondary cell wall thickening. Stimulation of dry weight of the hypocotyls by sucrose treatment in the presence of the cotyledons may be due to enhanced secondary cell wall thickening.
Studies in Crataegus (Rosaceae: Maloideae). IX. Short-shoot leaf heteroblasty in Crataegus crus-galli sensu lato
Authors: Dickinson T. A. , Phipps J. B.
Published: September 2008

In the taxa that constitute Crataegus crus-galli L. sensu lato short-shoot leaves vary progressively from node to node in both size and shape. The pattern of this variation may differ not only between taxa but also within taxa, among local stands. Failure to recognize such variation may confound taxonomic studies based on leaf shape, judging from the results of parallel canonical variates analyses differing in whether or not sampling was stratified by leaf position. With the incorporation of such stratification into the sampling design, however, leaf descriptors provide a valuable source of data for studies of group differentiation in Crataegus taxa.
Selectivité de fixation du sodium au niveau des embryons et des jeunes plantes sensible ou tolerante au NaCl
Authors: Guerrier Gilles
Published: September 2008

Embryos and young plants of tomato, radish, and red cabbage germinated in different media showed an ascending degree of tolerance to NaCl. Red cabbage embryos were tolerant to salinity and showed the highest K+ and Ca2+ fixation capacities which were correlated to the lowest initial adsorption of Na+. Furthermore, initial accumulation of K+ and Ca2+ in red cabbage was increased with increasing NaCl in the medium. Conversely, salt-sensitive tomato embryos showed the lowest initial internal ratios of Ca2+/Na+ and K+/Na+, and increasing NaCl concentrations did not provoke any increase in contents of K+ and Ca2+. No correlation was found between tolerance to salinity and Na+ content of young plants. However, Ca2+ accumulation capacity in a (NaCl + CaCl2) medium was associated with the degree of tolerance, although the ratio of internal Ca2+/Na+ decreased. In tomato and red cabbage, a competitive interaction was found between K+ and Na+ at high salt concentrations, while in radish allosteric interactions were observed. Thus, radish accumulated more K+ than Na+ at high KCl and NaCl concentrations and young plants of radish and red cabbage had the highest selectivity for potassium. Plant tolerance to salinity, during seed germination, was correlated to accumulations of K+ and Na+ in embryos. The mobilization of Ca2+ stored in the seed does seem to have a regulatory role in the plasmalemma selectivity.
Development of a freshwater periphyton community as influenced by diatom mucilages
Authors: Roemer Stephen C. , Hoagland Kyle D. , Rosowski James R.
Published: September 2008

The function of diatom mucilage in the formation of spatially complex periphyton communities was investigated in McConaughy reservoir (Nebraska, U.S.A.). Seasonal biofilms on natural and artificial substrates revealed high densities of periphytic diatoms (up to 3.5 × 104 cells mm-2). Growth habits of the dominant taxa (short stalk, Achnanthes minutissima; long stalk, Cymbella affinis and Gomphonema olivaceum; rosette, Fragilaria vaucheriae and Synedra radians) depend on the mucilage morphology. The volume of stalk mucilage in late stages of community development was estimated to be more than two times the volume of the cells producing it. When the periphytic biomass exceeded the carrying capacity of its substrate, portions of the community were sloughed, resulting in the loss of the upper story of cells and mucilage. Diatom mucilage affects community structure as follows: (i) it allows cell–surface adhesion; (ii) stalks of Cym. affinis provide increased surface area for attachment by Ach. minutissima; (iii) dense canopies of long-stalked Cym. affinis and Gomphonema olivaceum trap euplanktonic algae which have settled into the periphyton; (iv) mucilage binds detrital particulates; (v) stalked diatoms enable vertical stratification in the community, as spring collections revealed the development of an upper tier composed of Gomphonema olivaceum and Cym. affinis covering a lower tier dominated by F. vaucheriae and Stephanodiscus minutula.
Chaetomium globosum antagonizes the apple scab pathogen, Venturia inaequalis, under field conditions
Authors: Cullen Daniel , Berbee Flora M. , Andrews John H.
Published: September 2008

During the 1981 and 1982 growing seasons, Aureobasidium pullulans (de Bary) Arnaud and Chaetomium globosum Kunze: Fr. spore suspensions were applied to apple saplings in an orchard at 1- to 2-week intervals to control the apple scab pathogen, Venturia inaequalis (Cke.) Wint. (anamorph, Spilocaea pomi Fr.). Population densities of applied antagonists were monitored during 1982 trials by dilution plating of leaf washings onto selective media. Aureobasidium pullulans and C. globosum populations averaged 54 and 314 colony-forming units (CFU) per milligram of leaf tissue 3 h after application and declined to means of 15.9 and 35.7 CFU mg−1, respectively, before the next application. Relative to buffer controls, spore suspensions of A. pullulans were only slightly antagonistic to V. inaequalis infection, but C. globosum ascospore suspensions reduced scab more than 20% in both years. Light and scanning electron microscope examination of leaf surfaces following inoculation of seedlings in growth chambers showed a 25% increase in C. globosum ascospore germination on scab-infected tissue relative to healthy tissue. The minimum concentration of C. globosum inocula effectively reducing apple scab in growth chamber experiments was approximately 1 × 106 ascospores mL−1.
Evidence for the role of antibiosis in the antagonism of Chaetomium globosum to the apple scab pathogen, Venturia inaequalis
Authors: Cullen Daniel , Andrews John H.
Published: September 2008

Ascospore suspensions and culture extracts of Chaetomium globosum Kunze: Fr. reduced infection of apple seedlings by Venturia inaequalis (Cke.) Wint. (anamorph, Spilocaea pomi Fr.) in growth-chamber studies. An agar diffusion assay was developed to assess the relative fungistatic activity of culture extracts of C. globosum. No differences were observed in the sensitivity of 37 V. inaequalis strains to C. globosum extracts. Seven strains of C. globosum from diverse habitats were evaluated for antibiotic production in culture. Significant differences in antibiotic production between strains were observed, and antibiotic levels were positively correlated with antagonism to V. inaequalis on seedlings in growth-chamber studies. The antibiotic chetomin was tentatively identified in culture extracts by thin-layer chromatography and ultraviolet absorbance. The selection of high antibiotic producing strains of C. globosum may significantly improve antagonistic performance in the field.
Nutrient changes and release during decomposition of leaf litter in a Himalayan oak–conifer forest
Authors: Pandey Uma , Singh J. S.
Published: September 2008

Changes in nitrogen, calcium, water-soluble compounds, and total available carbohydrate in decomposing leaf litter of six tree and one shrub species, enclosed in nylon net bags and placed in a mixed oak conifer forest, were examined for a period of 487 days. The concentration of nitrogen increased during decomposition in all litter species. This increase was up to threefold in Aesculus indica, Quercus floribunda, and Quercus leucotrichophora. In most species the absolute increase in nitrogen mass was observed when decomposition had progressed up to 213 days. However, in Daphne cannabina and Ilex dipyrena, the absolute mass of nitrogen was never greater than the initial mass at any stage of decomposition. The absolute mass of calcium in litter bags generally declined with time. The concentration of water-soluble compounds and of total available carbohydrates varied from species to species; both these constituents, however, continually decreased with the progress of decomposition. Within 1 year, the release of nitrogen, water-soluble compounds, and total available carbohydrates was 100% in D. cannabina, A. indica, and I. dipyrena. In Cedrus deodara, Q. floribunda, and Q. leucotrichophora about 50% of total nitrogen input to the forest floor as litter fall was released by decomposition. In Cupressus torulosa only 14% of nitrogen falling as leaf litter was released during a period of 1 year.
Schiffnerula barnadesiae and its Mitteriella and Questieriella synanamorphs
Authors: Hughes S. J.
Published: September 2008

Mitteriella and Questieriella synanamorphs of Schiffnerula barnadesiae are illustrated, described, and compared with those of two other species, namely M. ziziphina and M. ziziphi-rugosae. Clypeolella ziziphina, the teleomorph of M. ziziphina, is transferred to Schiffnerula.
Spore wall ultrastructure in the liverwort Fossombronia longiseta
Authors: Steinkamp M. P. , Doyle W. T.
Published: September 2008

Mature spores of Fossombronia longiseta (Metzgeriales, Codoniaceae) were examined with both scanning and transmission electron microscopes. Sporoderms are highly sculptured. The distal face markings consist of parallel ridges (cristae) or spines. The flattened proximal face has a series of short spinelike cristae, and a triradiate ridge mark sometimes is apparent. In section, the sporoderm consists of an intine and a two-layered exine. The inner exine layer consists of two lamellae, each of which contains a series of long, thin (3–4 nm), closely spaced, electron-lucent subunits; the subunits are separated by electron-dense material. The more or less solid outer exine consists of highly irregularly shaped lamellae, which also have a "white line" component. Amorphous, electron-dense material permeates these lamellae and fills the channels between the lamellae. The intine and much of the electron-dense material of the exine is removed by acetolysis. Spore wall ultrastructure in this species is complex compared with other species of the Metzgeriales and Jungermanniales that have been studied so far.
Breeding relationships among several species of Agaricus
Authors: Anderson James B. , Petsche Dawna M. , Herr Frank B. , Horgen Paul A.
Published: September 2008

We have examined the breeding behavior of several species of Agaricus including the cultivated A. brunnescens and the wild A. bitorquis, A. vaporarius, A. arvensis, A. campestris, A. silvicola, and A. placomyces. For A. brunnescens, two homo-karyons carrying auxotrophic mutations and compatible mating types were obtained from the American Type Culture Collection. A stable, prototrophic heterokaryon was recovered by nutritional selection from a pairing of the two auxotrophic strains. The two nuclear types were recovered from the heterokaryon by the formation and regeneration of protoplasts, many of which were homokaryotic. In A. bitorquis, a distinct macroscopic interaction correlated with dikaryon formation was observed in compatible matings of single-spore isolates. Fluffy zones of dikaryotic mycelium appeared in compatible pairings where the two cultures met. Mating among monosporous isolates was specified by unifactorial heterothallism. These observations of A. bitorquis were similar to those reported by others. Pairings of isolates from different stocks indicated a minimum of eight incompatibility alleles among 10 stocks of A. bitorquis. Although migration of nuclei generally does not occur in Agaricus, one stock of A. bitorquis produced monosporous isolates with nuclei that migrated through the resident mycelium of some compatible mates. The migration was evident as a fluffy zone of dikaryotic hyphae that spread unilaterally in a pairing. Monosporous isolates of A. vaporarius showed distinct mating interactions similar to those in A. bitorquis. No mating interactions were observed in pairings of sibling monosporous isolates of any of the other species examined. When isolates of different taxonomic species were paired, no reactions suggestive of compatibility were observed between A. brunnescens, A. bitorquis, A. vaporarius, or any of the other species.
Crown architecture of Larix laricina saplings: quantitative analysis and modelling of (nonsylleptic) order 1 branching in relation to development of the main stem
Authors: Remphrey W. R. , Powell G. R.
Published: September 2008

The upper 5 years of crown growth in samples of Larix laricina (Du Roi) K. Koch (tamarack) saplings from natural populations in the Fredericton, N.B., area provided data to model architectural relationships describing patterns of (nonsylleptic) order 1 branching in relation to development of the main stem. The model was based on relationships between branch extension and height growth, and numbers and positions of order 1 branches. Elevation angles of shoots making up the branches, and conversion of order 1 long shoots to order 1 short shoots were also incorporated. Lengths of current shoots of major order 1 branches tended to decrease with increasing depth in the crown. Similar tendencies occurred among lengths of all current branch extensions within single height-growth increments, but the decreases in length became less regular with increasing age of branch. Because the relationships were complex, alternative approaches to modelling shoot lengths were adopted to enhance understanding of the patterns involved. Deterministic and stochastic elements were used in the overall model to account for significant proportions of morphological variability. Simulations based on the alternatives within the model were realistic in their interpretations of actual sapling crown architecture. Classification of L. laricina according to previously proposed architectural models that qualitatively describe general development was discussed.