bluuebunny/crossref_metadata_2025 huggingface dataset:
Light and electron microscopic investigations in the Dictyonemataceae (basidiolichens). II. Dictyonema irpicinum
Authors: Slocum Robert D.
Published: April 2011

The nature of the fungus–alga association between the lichen-forming basidiomycete Dictyonema irpicinum Mont. and its Scytonema host was investigated using light and electron microscopical techniques. The lichen-like basidiocarp is established as a result of the active capture of free-living Scytonema sp. trichomes by the fungal symbiont. A septate, intracellular haustorial hypha is produced by the basidiomycetous fungus within the filamentous blue-green alga. This specialized haustorial apparatus appears to enhance the survivorship of the otherwise ephemeral fungus, allowing it to maintain a long-term, stable association with the algal host.
Nitrate assimilation in suspension cultures of Paul's scarlet rose
Authors: Jordan Douglas B. , Fletcher John S.
Published: April 2011

Nitrate reductase activity, the assimilation of NO3−, and growth were studied in suspension cultures of Rosa cv. Paul's Scarlet grown in media with either 24 mM NO3−,or with 24 mM NO3− + 0.91 mM NH4+.Ammonium partially repressed the development of nitrate reductase during the first 4 days of growth and the degree of repression was more pronounced when cells were provided with lower concentrations of NO3−. The repression of nitrate reductase by NH4+ was only observed when casein was used during enzyme extraction. The repression of nitrate reductase activity by NH4+ was not recognized in earlier work when no casein was used.The presence of casein in the extraction or assay medium increased the total recoverable nitrate reductase activity. The enhancement was differential depending on cell age with the greatest influence being on young and old cells where 100 and 400% enhancements were observed, respectively.In vitro nitrate reductase activity correlated well with NO3− assimilation. Over 14 days of growth, the ratio of total nitrate reductase activity to the total amount of NO3− reduced was 3.8 for cultures grown with or without NH4+. Cultures grown with NH4+ achieved 80% more fresh weight and reduced 70% more NO3− over 14 days than cultures grown without NH4+.
Population ecology in an environmental mosaic: Cakile edentula on a gravel bar
Authors: Keddy Paul A.
Published: April 2011

The population ecology of the annual plant Cakile edentula was studied on a gravel bar in Halifax County, Nova Scotia, where it grows in a two phase mosaic consisting of (1) open shingle or gravel and (2) thick mats of dead Zostera marina wrack. Cohorts of seedlings were marked and regularly counted in both habitats. Reproductive output and seed dispersal were also studied.There were marked differences in C. edentula ecology between the two habitats. In general, survivorship and reproductive output were both greater in shingle. However, caterpillar grazing in late summer was concentrated on shingle plants, with the eventual result that net reproductive output was greater in wrack. There was no evidence of seed movement between wrack and shingle.Seedlings of C. edentula often grew in dense clusters around the remains of the previous year's parent(s). In both habitats, C. edentula seedling density declined with distance from the centre of clusters. Reproductive output increased with distance in both habitats; survivorship increased with distance only in wrack. Distal fruit segments were dispersed further than proximal segments; thus seedlings derived from distal segments tended to grow further from the previous year's parent, and in turn had higher survivorship and reproductive output. Distal fruit segments are normally thought to function primarily for long-distance dispersal; on shingle beaches "long-distance dispersal" of less than a metre could significantly improve the reproductive success of a seedling.
Navicula subfossilis sp.nov., the dominant taxonomic entity of a Pleistocene assemblage from Ellesmere Island, N.W.T.
Authors: Lichti-Federovich Sigrid
Published: April 2011

The numerically dominant diatom of a Pleistocene marine littoral assemblage has been ascribed to the Naviculae microstigmaticae section and assigned a "new species" status. Scanning electron and light photo micrographs have been presented to demonstrate the structural features used in the morphological delineation of the taxon Navicula subfossilis sp.nov. The phenotypic characteristics of allied forms have been evaluated and their structural relationships have been assessed.
Sexual reproduction in western red cedar (Thuja plicata)
Authors: Owens John N. , Molder M.
Published: April 2011

Pollen cones and seed cones ended dormancy in mid-February, microsporogenesis occurred in late February, and pollination occurred for about 1 week in early March. Pollen was shed at the two-celled stage. Pollination drops were exuded from only a few ovules at one time. Pollen contacting the pollination drop was rapidly taken in. The pollination drop was withdrawn into the micropyle which was later sealed by enlargement of cells lining the micropylar canal. Megasporogenesis occurred in late February but female gametophytes did not mature and fertilization did not occur until late May. An archegonial complex formed containing seven to nine archegonia, of which several usually were fertilized. Proembryo development varied depending upon the size and shape of the archegonia. Usually, a 12-celled, three-tiered proembryo formed by mid-June. Cleavage polyembryony was not observed. Embryos were mature by mid-August and most seed was shed in September and October.The potential seed set was only 16 seeds per cone and filled seed averaged only 2.6 per cone. Most potential seed was lost because of early ovule abortion from unknown causes, insect damage, or low temperatures at or shortly after pollination. Some potential seeds were lost because the ovules were not pollinated or the embryos aborted. These seeds were soft but nearly normal appearing and contained spongy female gametophyte tissue. Methods of maximizing seed production are suggested.
Some new taxonomic characteristics applied to Stichococcus bacillaris (Chlorophyceae)
Authors: Brown Lewis M. , Hellebust Johan A.
Published: April 2011

The genus Stichococcus has been distinguished from the genus Klebsormidium with difficulty. Also, small unicellular algae with bacilliform to oblate morphology have also been confused with members of the genus Stichococcus. A number of algal strains were examined that were either taxonomically related or morphologically similar to this genus. These algae are characterized by patterns of organic solute accumulation during salinity stress. Growth and morphological responses to salinity in culture and aspects of cell wall composition supplement criteria based on solute accumulation. The genus Stichococcus Nägeli is easily distinguished from Klebsormidium Silva, Mattox and Blackwell and other algae based on this evidence. It is proposed that Klebsormidium marinum be merged with Stichococcus bacillaris and be reduced to a synonym of S. bacillaris.
Long-term effects of fire on the composition and activity of the soil microflora of a subalpine, coniferous forest
Authors: Bissett J. , Parkinson D.
Published: April 2011

The biomass, community composition, and metabolic activity of soil microorganisms were studied in adjacent burnt and unburnt areas of spruce–fir subalpine forest razed 6 years previously by a moderately severe natural fire. Similar levels of microbial biomass were observed at comparable burnt and unburnt sites, although the ratio of fungal to bacterial biomass was higher in the unburnt soils. The decreased acidity of the surface horizons in the burn probably tended to favor the development of a bacterial flora rather than a fungal flora. Microbial biomass in the burnt sites peaked earlier in the season than in the unburnt sites in response to the warmer soil temperatures and earlier thaw in the spring in the burn area.Significant differences in the species composition of the mycoflora in the organic soil horizons were observed between the burnt and unburnt sites. Apparently, these were related to qualitative differences in the recent litter. Phoma, Cladosporium, and Botrytis, which are usually associated with early stages of decomposition of herbaceous litter, were more common in the burnt soil. The mycoflora of the mineral soil horizons varied considerably from one burn site to another, possibly reflecting the geographical variation in the intensity of the burn. In overall composition, however, the mycoflora in the mineral soil horizons of the burn was not appreciably different from that of the unburnt sites.Higher laboratory rates of respiration and cellulose decomposition were observed for soil samples from the undisturbed forest. However, the rate of decomposition of cellulose in the field was much higher in the burnt sites, probably as a result of the higher soil temperatures in the burn area. Low soil temperature was concluded to be the main factor limiting microbial activities in the study area, and the removal of the insulating plant canopy and increased heat absorption by the ash in the burn area were found to increase decomposition rates, at least at this stage in the succession following the disturbance of fire.
Etude tridimensionnelle du complexe sécréteur plastes–réticulum endoplasmique dans les poils glandulaires d'Hygrophila difformis (Acanthacées)
Authors: Rohr René , Dexheimer Jean , Kieffer Mariette
Published: April 2011

The general organisation and functioning of the secretory cells of the glandular hairs of Hygrophila difformis show some analogies with previously studied glandular systems of the same type; they differ from the latter, however, in the complexity of organisation of the reticulum – plastid complex.In the undifferentiated cell the plastids have a simple rounded, slightly elongated form; they display no special relationship with the endoplasmic reticulum which, at this stage, is represented by irregularly enlarged cisternae containing a dense substance of fibrous appearance.During the secretory phase, on the contrary, the ultrastructures of the plastids and of the endoplasmic reticulum undergo considerable changes; the latter appears in the form of small tubes arranged parallel to each other and in close contact with the plastids. The plastids themselves take on shapes which, until now, have never been observed in this type of cell and which can only be shown clearly by a three-dimensional reconstruction. This technique, which involves making a series of thin sections, has been applied to secretory plastids for the first time. It gives a faithful picture of their original morphology and the various modes of association possible between the plastids of a given reticulum – plastid complex.
Lichens from the area drained by the Peel and Mackenzie rivers, Yukon and Northwest Territories, Canada. I. Macrolichens
Authors: Bird Charles D. , Thomson John W. , Marsh Alfred H. , Scotter George W. , Wong Pak Yau
Published: April 2011

The distribution and general ecology of 249 macrolichen taxa is described for 230 000 km2 of coniferous forest, open fens, and alpine terrain along the Mackenzie River in the District of Mackenzie, Northwest Territories, and the Peel River, a major tributary which rises in the Yukon Territory. Permafrost plays a major role in determining the plant communities that are present. Fire and man-made disturbances initiate succession. There are 45 new reports for the District of Mackenzie and 30 for the Yukon. Of the taxa, 86% are found in Europe, Asia, and North America, 9% are known from Asia and North America, whereas only 4% are restricted to North America. Pilophorus robustus is new to Canada. High mountains in the western part of the area, generally nonglaciated during the Wisconsinian, support a flora that contains many Arctic and Arctic–Alpine taxa. Amphi-Beringian species occur primarily in the north.
Genera coelomycetum. XVIII. Ellula anamorph-gen.nov., another coelomycete with basidiomycetous affinities
Authors: Raj T. R. Nag
Published: April 2011

Eleutheris guaduae Viegas is reassessed and redisposed in a new anamorph genus Ellula as E. guaduae (Viegas) Nag Raj comb.nov.
Identification of Picea pollen of Late Quaternary age in eastern North America: a numerical approach
Authors: Birks H. J. B. , Peglar Sylvia M.
Published: April 2011

Five collections of modern Picea glauca pollen, four of P. mariana, and two of P. rubens were examined in an attempt to distinguish the pollen of the species. Three morphological variables were recorded for individual grains in each collection. The sculpturing of the furrow membrane is not diagnostic, but the presence of an undulating margin to the cap and of irregular reticulation in the sacci characterize P. rubens pollen. Seven size variables were also measured for each grain. No simple combination of morphological and size criteria provides effective discrimination between P. glauca and P. mariana pollen.Linear discriminant analysis was applied to the size data for P. glauca and P. mariana. The mathematical assumptions of the method were tested, and to satisfy them, the discriminant analysis was confined to six of the seven variables measured. The discriminant analysis resulted in 91.5% of the pollen being correctly distinguished.The same six variables were measured on fossil Picea pollen from two Late Wisconsin sites in Minnesota and one Holocene sequence in Labrador. The individual fossil grains were assigned to either P. glauca or P. mariana by means of discriminant analysis. The Late Wisconsin spectra consist of both species, a result supported by macrofossil evidence. Picea glauca predominates in the early Holocene spectra from Labrador. It is replaced by P. mariana after about 5000 years before present, reflecting paludification and the spread of muskeg.The limitations of the procedure are discussed, and its potential is emphasized.
Nectar production in the boreal forest lily Clintonia borealis
Authors: Plowright R. C.
Published: April 2011

Nectar secretion in unpollinated flowers of Clintonia borealis (Ait) Raf. (Liliaceae) began as the tepals first opened, reached a maximum at about the time the anthers dehisced, and ceased after the tepals began to curl back. Total lifetime sugar production was highly correlated with flower size and was not affected by daily nectar removals. Nectar concentration varied widely as a response to fluctuations in atmospheric relative humidity. It is suggested that since freshly secreted Clintonia nectar ranged in concentration from 4 to 63% sugar by weight, comparisons of nectar concentration among different species may not be meaningful unless accompanied by environmental data at and prior to the time of sampling.
Histological comparison of compatible, mesothetic and incompatible reactions between Puccinia graminis tritici and wheat
Authors: Higgins Verna J.
Published: April 2011

Three races of Puccinia graminis tritici developed by successive mutations to give increased virulence (i.e., incompatible → mesothetic → compatible) on the Sr6 gene for resistance were compared histologically on cv. McMurachy (Sr6 gene) growing at 20.5 °C. The length of the longest hyphae and the size of the lesions remained similar in the three interactions up to 3 days after inoculation and then comparative degrees of growth occurred in the following decreasing order; compatible > mesothetic > incompatible. Necrotic cells in the compatible interaction were infrequent (maximum of 6% of infection sites) and hyphae radiated out from the point of ingress in an unimpeded manner. Although necrosis in the incompatible interaction occurred 1 day in advance of necrosis in the mesothetic reaction, by the 6th day, 98–100% of the infection sites in both systems had necrotic cells. In the mesothetic reaction, hyphae grew beyond the area of necrosis in a high proportion (70% at day 6) of the infection sites whereas the incidence of such growth was much less (8% at day 6) in the incompatible reaction. The role of the hypersensitive reaction in these interactions is discussed.
Further characterization of the physiologic races of Pseudomonas glycinea
Authors: Fett W. F. , Sequeira L.
Published: April 2011

Leaf age at the time of inoculation was a critical factor determining the differential reaction of soybean cultivars to the leaf blight pathogen, Pseudomonas glycinea. Of 23 P. glycinea strains from Wisconsin, 22 were of race 4 and one of race 5. Of 14 P. glycinea strains obtained from the National Collection of Plant Pathogenic Bacteria, Harpenden, England, one strain was of race 1, nine strains were of race 4, and three strains were of a new physiologic race herein designated as race 9. Pathogenicity to soybean of one strain, NCPPB 1764, could not be confirmed.The reaction of several soybean cultivars to representatives of several physiologic races of P. glycinea differed from that originally reported in that a susceptible rather than a resistant response was obtained. This difference may have resulted from experimental conditions that differed slightly from those used by the original investigators.
An in-block, light microscope viewing procedure for botanical materials in plastic embedments; with emphasis on location and selection of host cell–microbe encounter sites
Authors: Zeyen Richard J. , Bushnell William R.
Published: April 2011

A generalized procedure for direct, in-block, light microscopic viewing of plastic embedded botanical specimens has been developed that allows users to: (i) quickly and economically survey large numbers of specimens in embedment blocks, (ii) remove unwanted tissue and cell types from viewing areas with little risk of artifact development, (iii) map and photograph locations of desired sectioning sites before block trimming, (iv) view desired sectioning sites during the trimming process, and (v) perform either thick sectioning or ultramicrotomy on specimen blocks manipulated during the procedure.
Evolution in vitro du contenu en ADN nucléaire et de la ploïdie des embryons polliniques du Datura innoxia
Authors: Sangwan-Norreel Brigitte S.
Published: April 2011

Nuclear DNA content was estimated by densitometry in three stages of in vitro development of Datura innoxia Mill. embryos (3–25 cells) obtained from pollen. At the same time, the sizes, structure and arrangements of nuclei in young embryos were examined and chromosome numbers of adult embryos were determined. Results showed that: (i) Embryos originating from pollen were haploid, diploid, aneuploid, or myxoploid. Proportions of each ploidy level varied with cell numbers in embryos, and with ages of cultures, (ii) Young diploid embryos were very regular and had dense nuclei of one type only. Haploid embryos were less regular; they had one or two types of nuclei whose texture was often looser than that of diploid embryo nuclei. Aneuploid and myxoploid embryos had very irregular structures, (iii) Initiation of androgenetic embryos was spread out in time from the 2nd to the 12th day of culture. Embryos showed different nuclear features if they were initiated at the beginning, in the middle, or at the end of the culture period. Embryos initiated early were mostly haploid and the proportion of abnormal ploidy embryos was low during the 1st week of culture. In Datura innoxia, therefore, embryos must be taken after 1 week of culture to obtain the population which is most favourable to further genetic breeding. [Journal translation]
Levels of glucose-6-phosphate and 6-phosphogluconate dehydrogenases in the embryos and endosperms of some dormant and nondormant lines of Avena fatua during germination
Authors: Upadhyaya Mahesh K. , Simpson Graham M. , Naylor James M.
Published: April 2011

To investigate the possible role of the pentose phosphate pathway in dormancy and germination of seeds of Avena fatua L., levels of glucose-6-phosphate and 6-phosphogluconate dehydrogenases were analyzed in genetically dormant and nondormant pure lines. Embryos and endosperms of dry mature seeds of each line exhibited high activity for both enzymes. Dehydrogenase levels in the embryos isolated from dormant lines remained constant during the first 48 h of incubation in water, but in nondormant lines there was a sharp increase after 24 h of incubation, well after the onset of germination. Similarly, when seeds of a dormant line were incubated with gibberellin A3 (GA3), there was no increase in dehydrogenase levels in embryos prior to the onset of germination. Thus, in Avena fatua the levels of pentose phosphate pathway dehydrogenases are not involved in the regulation of seed dormancy.In endosperm tissue the pentose phosphate pathway dehydrogenase activity declined rapidly after germination (GA3-induced in the case of the dormant line). The α-amylase activity increased as the dehydrogenase activity declined. Thus, the pentose phosphate pathway appears to be active in endosperm during the early stage of germination, and its dehydrogenases are selectively inhibited, inactivated, or degraded after germination. Unlike α-amylase, the pentose phosphate pathway dehydrogenases were not induced by the exogenous application of GA3 to the endosperm halves.
Étude cyto-écologique de quatre populations de Claytonia caroliniana var. caroliniana au Québec
Authors: Gervais Camille , Grandtner Miroslav M.
Published: April 2011

The cytology and ecology of four Québec populations of Claytonia caroliniana var. caroliniana, each one coming from a different phytosociological climax domain, have been studied. The plants from Mt. Logan (subalpine zone) were stable (n = 8 or 2n = 16, the usual chromosome number of the species) but three other populations (maple forest domains) have shown various proportions (10–50%) of abnormal chromosome numbers: n = 9, 10, 11, 15, 19, 20 and 2n = 17, 25. These numbers could be explained (1) by the formation of diploid gametes, (2) by the arising of triploid individuals, and (3) by the presence of B chromosomes. The percentage of plants with anomalies is parallel but smaller when tubers are examined instead of the flowers. This suggests a disturbing influence of environmental or genetic factors on scapes, flower development, or sporogenesis. The plants with abnormal chromosome numbers observed in the samples, seem to be occasional cytotypes rather than representatives of actual chromosomal races. Furthermore, there are apparently no morphological characters permitting their identification or the segregation of the various populations that have been studied from different environments. The frequencies of anomalies in the flowers seems to be related to the stations (χ2 = 8,75, df = 3). Correlation tests also show that the drainage and rainfall in April and May could be eventually connected (r = 1,000, α = 0,05) to the chromosomal anomalies and to the cytological evolution of the populations, as it possibly affects the sporogenesis which takes place when the scapes reach the soil surface. Such causative correlations are evidently extremely hypothetical because the number of sampling points is too small; more cytological and ecological data and (or) experimental evidence still remain to be collected. Nevertheless, these observations demonstrate that C. caroliniana is undergoing cytological variations in the northeastern part of its area and behaves similarly to C. virginica.
Cell wall water dilution: an explanation of apparent negative turgor potentials
Authors: Markhart III Albert H. , Sionit Nasser , Siedow James N.
Published: April 2011

Errors in psychrometric determinations of osmotic potential (Ψs) due to dilution of the cytoplasm by cell wall water are investigated. Model systems using filter paper to represent the cell wall and sucrose solution and distilled water to represent protoplasm and cell wall water, respectively, show significant dilution of the sucrose solution at cell wall to protoplast ratios typical of plant tissue. Mathematical simulation of error in Ψs determination as a function of percent cell wall and cell wall hydration indicate that wall water dilution can be a significant problem and could explain reported apparent negative turgor potentials.
Vessel-length distribution in stems of some American woody plants
Authors: Zimmermann Martin H. , Jeje Ayodeji A.
Published: April 2011

Vessel-length distributions in some trees, shrubs, and a vine have been calculated from measurements of particle penetration and of air-volume flow through the xylem. In shrubs and diffuse-porous species, longest vessels were about 1 m long, but most of them were much shorter, the largest percentage in the 0–10 cm length class. In the two ring-porous species investigated (Quercus rubra and Fraxinus americana), the longest vessels often were as long as the tree's stem, but most of them were much shorter. In the grapevine (Vitis labrusca) which has large-diameter vessels (ca. 300 μm) a small percentage of the vessels was 8 m, but most of them were less than 5 m long. In a given species, lengths of the longest vessel were quite variable, but the distribution of the short lengths was more constant. In general, vessel lengths are correlated with vessel diameters: wide vessels are longer. Even in diffuse-porous species, the slightly narrower latewood vessels are somewhat shorter than the wider early wood vessels. The method is a simplified version of that described by Skene and Balodis, but using a programmable desk calculator. It works best with diffuse-porous species in which vessels are randomly distributed in the stem, and less well in species with wide vessels, because as vessels reach the length of the stem itself, they cannot be randomly distributed.
Localization of phenols and polyphenol oxidase in 'Jewel' sweet potatoes (Ipomoea batatas 'Jewel')
Authors: Schadel W. E. , Walter Jr. W. M.
Published: April 2011

Histochemical tests for phenols and polyphenol oxidase were performed on fresh root tissue of Ipomoea batatas (L.) Lam. 'Jewel.' The phenolic compounds were localized in the phellem, phellogen, and phelloderm, in approximately 1 mm (ca. 10–15 cells) of the tissue directly beneath the periderm, in the latex of laticifers, in the phloem, in the cambium which separates the secondary phloem from the secondary xylem, in the anomalous secondary cambia of the central core, in the parenchyma cells adjacent to the xylem elements, and in the walls of the xylem elements. Polyphenol oxidase was localized primarily in the phellogen and phelloderm and most prominently in the latex of laticifers.
Ecological diversification among nine species of Pohlia (Musci) in western North America
Authors: Shaw A. Jonathan
Published: April 2011

Nine North American species of Pohlia, section Pohliella, form a complex of morphologically and ecologically similar species. In western North America, where there is a broad region of overlap in geographic ranges, they frequently grow together in various combinations. Over 300 soil samples representative of these species were analyzed with respect to organic matter content, pH, and concentrations of exchangeable calcium and magnesium ions, and each species was found to be distinctive in terms of these environmental factors. Morphologically variable species tend to be ecologically and geographically widespread, while less variable species tend to be more restricted. Species with a predominance of primitive morphological features occur primarily on tundra soils of intermediate pH, while morphologically advanced species inhabit road banks or other disturbed sites where the pH may be high or low.
Septal ultrastructure and the taxonomy of Exobasidium
Authors: Khan Saeed R. , Kimbrough James W. , Mims Charles W.
Published: April 2011

The relationship of Exobasidium (Exobasidiales) to other groups of Basidiomycetes has long been questioned. Although this genus has been traditionally placed in the Holobasidiomycetes, septal ultrastructure, combined with other features of the basidium, suggest a much closer relationship to the Teliomycetes.
Insect–fungus blister galls on Solidago graminifolia and S. rugosa. I. A macroscopic and light microscopic study of the host–parasite relationship
Authors: Camp Russell R.
Published: April 2011

The host–parasite relations of an insect–fungus blister gall on Solidago graminifolia and a related gall on S. rugosa were studied. The midge, Asteromyia carbonifera, and fungus, Sclerotium asteris, were associated with both gall types.Externally, young galls of both types had a black center surrounded by a yellow halo. During growth in diameter the external coloration did not change in S. graminifolia; however, in S. rugosa a beige – ashy grey area developed in the center of the black region and expanded outward. In both species the leading edge of intercellular fungal hyphae was present in the halo region. Behind this front, hyphae sequestered to form an undifferentiated subepidermal stroma. The stroma differentiated into a black cortex and underlying white medulla at the margin of the black region. Differentiated cells remained subepidermal in both species except for the cortex that became subcuticular in S. graminifolia. During cortical proliferation in S. graminifolia the cuticle remained intact; however, epidermal cells became isolated and collapsed. In S. rugosa the epidermis separated extensively from the mesophyll but remained intact. Mesophyll cells within the halo and black region exhibited a reduction in number and size of chloroplasts and starch grains in both species.
Lateral branch vascularization: its circularity and its relation to anisophylly
Authors: Larson Philip R. , Richards Jennifer H.
Published: April 2011

The vasculature of elongating lateral branches of Populus deltoides Bartr. ex Marsh. was examined to determine how vascular continuity was attained around the entire branch circumference. In a previous study it was found that a pair of original bud traces (A, A′) gave rise to three pairs of bud traces in sequence (a, a′; b, b′; g, g′) that vascularized the axillary bud; the original bud traces then continued upward in the main stem axis. In this study we demonstrated that the lower, abaxial part of the branch cylinder was vascularized by derivatives of the first pair of bud traces (a, a′), the lateral parts primarily by derivatives of the second pair of bud traces (b, b′), and the upper, adaxial part by derivatives of the third pair of bud traces (g, g′). Thus, the organizational pattern for branch vascularization was established during the earliest stages of axillary-bud initiation. Leaves on all lateral branches were anisophyllous; the condition was related to the position of leaves in the phyllotactic array and to their vascularization. The smallest leaves always occurred on the upper branch side and their central traces were diverted upward in the main stem vascular cylinder. The largest leaves were usually on the lower stem side and their central traces were diverted downward. Some first-formed leaves were falcate, and the lateral traces serving the suppressed sides of their laminae were also found to be diverted upward in the main stem axis. It was suggested that both the small anisophyllous and the falcate leaves might result from a lower nutritional status because of their upward-directed leaf traces.
Isoetes acadiensis, a new species from eastern North America
Authors: Kott L. S.
Published: April 2011

A new species of Isoetes, Isoetes acadiensis, from North America is described. The particular combination of characters of microspore and megaspore ornamentation, spore sizes, and chromosome number separates this species well from all existing species. Its range is restricted to the northeastern seaboard of North America and it occurs most commonly in Nova Scotia.
Fertility relationships in closely related taxa of Oxalis, section Corniculatae
Authors: Doust Lesley Lovett , Doust Jon Lovett , Cavers Paul B.
Published: April 2011

Reciprocal pollinations with control treatments were made within and among four closely related taxa of Oxalis: O. corniculata, O. stricta, O. dillenii ssp. dillenii, and O. dillenii ssp. filipes.The following conclusions were made. (1) There was evidence that O. d. ssp. filipes was capable of seed set by facultative apomixis. (2) All four taxa were self-compatible and showed highest seed set when left to self-pollinate. (3) In all matings seed set occurred, but the level of fecundity was dependent upon species and also upon whether a species served as maternal or paternal parent. (4) The seeds were subsequently germinated. It was found that measures of intertaxon compatibility based on capsule formation or seed set alone did not necessarily reflect the level of interfertility in terms of seed viability. (5) Differential reproductive success of each mating generally supports the earlier taxonomic treatment of Eiten for the section.
Sporopollenin in the cell walls of Coccomyxa and Myrmecia phycobionts of various lichens: an ultrastructural and chemical investigation
Authors: Honegger Rosmarie , Brunner Ueli
Published: April 2011

Symbiotic and cultivated Myrmecia phycobionts of Baeomyces rufus and Coccomyxa phycobionts of five different asco- and basidio-lichens were investigated with cytological and chemical methods. The cell wall structure of the free-living type species Coccomyxa dispar was compared with that of the lichen phycobionts.Three different wall layers were observed in all Coccomyxa and Myrmecia cells investigated. An innermost, variably thick layer is amorphous in structure and is built up mainly by Golgi-derived hemicelluloses. An outer wall layer, uniformly thick, appears electron dense in thin sections and exhibits short, probably cellulosic fibrils embedded in an amorphous matrix in freeze-fracture preparations. Beyond these two wall layers is an outermost trilaminar wall layer of uniform thickness in all species investigated. It contains sporopollenin in its electron-transparent, rigid middle part; proteinlike particles are embedded in an amorphous, carbohydrate-containing matrix on its electron-dense inner and outer surfaces. IR spectrophotometry of acetolysis-resistant material yielded data comparable with those of other sporopollenin-containing algal walls, although the Coccomyxa and Myrmecia sporopollenin did not dissolve in chromic acid. The trilaminar layer is not lysed during or after autospore formation. Persistent mother cell walls were detected in all lichen thalli investigated, as well as in the culture medium of isolated phycobionts. Persistent mother cell walls were also found in the gelatinous sheath of Coccomyxa dispar.This type of wall structure affords protection against fungal parasitism and may be a significant factor in the success of some lichens and some other symbiotic systems.
Needle demography and growth pattern of Corsican pine
Authors: Maillette Lucie
Published: April 2011

A study of the demography of the needles and the growth pattern of Corsican pine is presented in relation to other studies of foliage dynamics. The construction of life tables is explained and applied to populations of Corsican pine needles. Needles from different trees as well as from different parts of trees had different survivorship. Leader needles had a much lower survivorship than all other needles. The frequency distribution of shoot lengths was log-normal, with the leader as the longest shoot. Climatic variations, tree age, apical dominance, and growth pattern appeared to be some of the factors involved in needle survivorship. Possible causes of needle senescence are considered with respect to an "activity schedule" derived from the work of other authors.
Studies in Gentianaceae. Embryology of Swertia minor (Gentianinae)
Authors: Rao K. Sankara , Nagaraj M.
Published: April 2011

The embryology of Swertia minor Knobl. (Gentianinae Gentianaceae) was studied. Features of its development are tetrasporangiate anthers, dicotyledonous type sporangial wall formation, glandular anther tapetum and its dual origin, simultaneous cytokinesis in microsporocytes, tricolporate two-celled pollen, unilocular ovary, forked parietal placentae, tenuinucellar unitegmic anatropous ovules, Polygonum-type megagametogenesis, persistent multiple multinucleate highly enlarged haustorial antipodal cells, nuclear endosperm, Solanad type embryo development, and multiseriate suspensor. Embryological features of taxonomic significance in the Gentianinae are compiled in a review of the pertinent data on the subtribe.
Influence of water stress on Verticillium wilt of yellow-poplar
Authors: Morehart A. L. , Melchior G. L.
Published: April 2011

The pathogenisis of Verticillium vascular disease was evaluated in root-inoculated yellow-poplar trees grown under favorable, periodically saturated and chronically low soil moisture levels. Verticillium was significantly more aggressive in host trees stressed by periods of low moisture than in host trees subjected to periods of flooding. At no time did inoculated, flooded trees exhibit typical Verticillium symptoms nor was pathogen reisolation obtained from the aboveground parts of these trees. In contrast, inoculated trees treated at favorable and low soil moisture levels incurred extensive pathogen colonization. Histological studies showed that the xylem vessels of petioles became occluded by fungus growth and a dark staining material at the time of first symptom expression. Additionally, macroscopic and microscopic observations of flooded trees indicated that acute injury occurred in the stem base and, under some conditions, the cortex in this region developed an aerenchyma induced by flooding.
Effets comparés de la fusicoccine, de la kinétine et de l'ablation de l'axe principal sur le bourgeon cotylédonnaire inhibé du Pois nain
Authors: Nougarède A. , Rondet P. , Rembur J.
Published: April 2011

The cotyledonary axillary buds with most of their nuclei in the G1 phase react to fusicoccin by showing a rapid elongation of their first two basal internodes. This elongation is achieved by the 15th h and is not accompanied by a passage of the nuclei to the S and G2 phases. In response to decapitation or to 6-furfurylaminopurine (6-FAP) application, DNA synthesis starts again. The cell cycle is released immediately upon decapitation or before subapical elongation starts in 6-FAP treated plants. These results are discussed in relation to the current concepts on the action of fusicoccin and hormonal factors on H+/K+ exchanges.
Observations on the anamorphs of six species of Diatrype and Diatrypella
Authors: Glawe Dean A. , Rogers Jack D.
Published: April 2011

Cultures and anamorphs of six species of Diatrype and Diatrypella are described. Diatrypella favacea produces conidia from sympodially proliferating conidiogenous cells, whereas Diatrype stigma produces conidia from percurrently proliferating (annellated) conidiogenous cells. Both of these types of conidiogenous cell proliferation were found in Diatrypella verrucaeformis, Diatrypella pulvinata, Diatrype virescens, and Diatrype albopruinosa. Both the sympodial and percurrent modes of conidiogenous cell proliferation appear to be associated with holoblastic conidiogenesis.
Reaction of two potato cultivars to leaf infection by Verticillium albo-atrum
Authors: Hung K. S. , Whitney N. J.
Published: April 2011

Leaf infection by Verticillium albo-atrum in both a susceptible cultivar and a resistant cultivar of potatoes was investigated. In both cultivars penetration occurred directly through the cuticle, leaf hairs, and stomata. In the resistant variety, hyphae were restricted to cells in the epidermis and palisade mesophyll resulting within 5 days in pinpoint necrotic spots, whereas in the susceptible cultivar hyphae penetrated freely from cell to cell in the entire leaf and killed the leaf within 5 days. It is suggested that the resistance is manifested as a hypersensitive reaction and that the method herein described offers a possible alternative to the root-dip method of testing for resistance.
Études microspectrophotométriques sur les céphalodies de Pseudocyphellaria faveolata
Authors: Renner Bernd
Published: April 2011

By adopting a cytophotometric technique we were able to localize lichen compounds in freezing microtome sections of lichen thalli with cephalodia. The results of spot measurements within the medullar envelope of cephalodia and the centre of cephalodia, as well as the results of single-line scanning in the visible and ultraviolet region, indicate high concentrations of depsides and depsidones in the medulla and the absence of any such secondary metabolites in the fungal tissue within the cephalodia. This finding agrees with the hypothesis that the mycobiont's metabolism is adapted to the nitrogen metabolism of the secondary algae.
Apparent auxin production and transport during winter in the nongrowing pine tree
Authors: Savidge R. A. , Wareing P. F.
Published: April 2011

Endogenous indol-3yl acetic acid (IAA) was characterized by combined gas chromatography – mass spectroscopy (GC–MS) in inactive cambia of Pinus contorta Dougl. and Larix decidua Mill, during winter, and IAA levels were estimated by GC–MS in buds, needles, and the tissues comprising the inactive cambial region of P. contorta during late autumn and winter. Supplementary IAA estimates were obtained for cambia of Acer pseudoplatanus L., L. decidua, Populus × canadensis 'Robusta,' and Quercus robur L. IAA levels in cambial tissue of lodgepole pine were higher than those in similar-aged tissue of hardwoods throughout the winter.Both winter disbudding and defoliating treatments reduced levels of endogenous IAA in the cambial region of lodgepole pine. Moreover, exogenous [14C]IAA and [14C]sucrose were transported downward in the stem during winter. Microscopy suggested functional sieve cells to be present during winter, and the moisture content of the cambial region of lodgepole pine was more than twice that of overwintering hardwoods.Thus, the vascular cambium of P. contorta probably is not dependent upon a supply of IAA from extending shoots and growing needles for its reactivation in spring. The findings also suggest that IAA production and export from metabolically active buds and mature needles may occur during winter.
Fluorescent antibody technique as a means of localizing Ceratocystis ulmi toxins in elm
Authors: Ipsen John D. , Abul-Hajj Yusuf J.
Published: April 2011

An aggressive strain of Ceratocystis ulmi was grown in a defined medium for the production of phytotoxins. Antisera to two distinct toxins, concanavalin A binding glycopeptides and cerato-ulmin, were prepared and used as probes for the detection and localization of the toxins in toxin-treated cuttings of elm. The toxins caused wilting of elm cuttings and were detected primarily on the pit membranes of bordered pits.
Inheritance of virulence of Ustilago tritici on the differential cultivars Carma, Red Bobs, and a derivative of the cross Thatcher × Regent
Authors: Nielsen J.
Published: April 2011

A cross between races T2 and T5 of Ustilago tritici was used to study the inheritance of virulence on three differential cultivars of spring wheat: Carma, Red Bobs, and a derivative of the cross Thatcher × Regent. Virulence on each of the cultivars was conditioned by a recessive gene. Gene Utv3 is responsible for virulence on cv. Carma, Utv4 for that on cv. Thatcher × cv. Regent, and virulence on cv. Red Bobs appears to be conditioned by the previously identified gene Utv1. These genes segregate independently from each other and from the gene for mating type.
A novel taxonomic character for Chaetomium as illustrated by the new species Chaetomium hexagonosporum
Authors: Carter A. , Malloch D.
Published: April 2011

A new Chaetomium species, Chaetomium hexagonosporum, is described and illustrated. In addition, the dextrinoid reaction of the ascospores of this species and other Chaetomium species in the "bostrychodes" group is discussed.
Observations sur le développement de plantules de Hêtre (Fagus sylvatica) cultivées en pépinière, orthotropie et plagiotropie
Authors: Thiebaut Bernard
Published: April 2011

Small beech trees were cultivated in a nursery under different climates, outdoors in the field under a climate with seasonal variations, and indoors in a greenhouse under an unvarying climate. The 1st year, in the field and in the greenhouse, all axes were orthotropic with "juvenile" leaves, whatever the number of cycles of elongation, one in the greenhouse and one to five in the field. The 2nd year, only one cycle of elongation was observed in the greenhouse but one or two cycles appeared in the field. Plagiotropic axes, with "adult" leaves, appeared during the first cycle and orthotropic axes, with "juvenile" leaves during the second cycle. The following years the growth of trees was the same as the second year, but annual polycyclic shoots became rare and orthotropic organs less frequent.
Marssoniella juglandis: anamorphe de Gnomonia leptostyla
Authors: Roquebert Marie-France , Fayret Jacques
Published: April 2011

The microscopical study of the two anamorphs of Gnomonia leptostyla (Fr.) Ces. et de Not. shows the structural similarity of the conidiomata and the same phialidic mode of conidiogenesis. Moreover one phialide is able to give rise to the two kinds of conidia (macro- and micro- conidia). It is proposed to unite the anamorphs under the generic name Marssoniella juglandis (Lib.) Höhnel emend Roquebert and Fayret.
A comparative study of sporophyte morphology of the three cytotypes of Polypodium virginianum in Ontario
Authors: Kott L. S. , Britton D. M.
Published: April 2011

There are three cytotypes of Polypodium virginianum L. in Ontario. These may be identified by macro- and micro-morphological characters. The most useful characters for identification are frond shape, tip lobing, shape of segment apices, spore size, cell size, and number of paraphyses per sorus. The triploid cytotype, which often overlaps the variation shown by the diploid and tetraploid, can be recognized by a high percentage of aborted spores.
Calcium mobilization into developing seedlings of umbelliferous plants
Authors: Lott John N. A. , Spitzer Ernest , Vollmer Catherine M.
Published: April 2011

Calcium mobilization into developing seedlings of several umbelliferous plants including carrot (Daucus carota L. cv. Imperator 408), wild carrot (Daucus carota L.), caraway (Carum carvi L.), anise (Pimpinella anisum L.), dill (Anethum graveolens L.), celery (Apium graveolens L. cv. Tall Utah), fennel (Foeniculum vulgare Mill.), parsnip (Pastinaca sativa L. cv. Hollow Crown), parsley (Petroselinum sativum L. cv. Moss Curled), and chervil (Anthriscus cerefolium L. cv. Curled) was investigated with emphasis on carrot and celery. Calcium determinations using atomic absorption spectrometry of carrot and celery embryos obtained from dry mericarps and carrot and celery seedlings collected when the pericarp plus testa plus endosperm remains fell off the seedlings, revealed that some calcium uptake occurred in carrot and possibly celery. It is possible that some of the calcium obtained by the seedlings came from the calcium oxalate crystals but the calcium could also have originated from other calcium sources within the endosperm. Polarized light studies of endosperm remains from carrot, celery, and the other members of the family Umbelliferae investigated, revealed that large numbers of calcium oxalate crystals were present in the endosperm remains after separation from the seedlings. The results of these studies indicate that calcium oxalate crystals are not used extensively as a calcium source during germination and early seedling growth.
Morphological and growth responses of geographically isolated Macrocystis integrifolia populations when grown in a common environment
Authors: Druehl Louis D. , Kemp Lindley
Published: April 2011

Changes in blade morphology and growth characteristics of Macrocystis integrifolia Bory from four geographically separated populations grown in a common environment were followed over two growth seasons. Initial differences in blade morphology and rate of biomass change became increasingly similar over time, indicating a plastic phenotypic response to the environment. In contrast, frond elongation and the rate of frond initiation appeared to be genotypically controlled.