bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultrastructure of laticifers in seedlings of Glaucium flavum (Papaveraceae)
Authors: Nessler Craig L.
Published: April 2011

Laticifers in seedlings of Glaucium flavum Crantz were examined by electron microscopy. Laticifer initials first apeared in procambium of the radicle adjacent to the phloem about 48–72 h after germination. Differentiation of laticifer initials was characterized by the proliferation of numerous vesicles from dilation of endoplasmic reticulum. The usual complement of organelles was present in laticifer elements including a nucleus, mitochondria, dictyosomes, and plastids. Plastids were devoid of organized lamellae and starch grains but contained electron-dense, membrane-bound inclusions. Large crystalline bodies of unknown composition were also seen in the cytoplasm of some laticifer elements. Perforations were not observed in the longitudinal walls shared by adjacent laticifer elements; thus the laticifer system in this species can be classified as nonanastomosing. Transverse walls between laticifer elements remained intact until late in cell differentiation; however, large perforations did form in these walls as a result of the gradual removal of wall material at the perforation site.
The mycorrhizal status of boreal plants: additional species from northeastern Ontario
Authors: Malloch D. , Malloch B.
Published: April 2011

Thirty-one species of vascular plants commonly occurring in the Boreal Forest Region of northeastern Ontario were examined for the presence of mycorrhizae. Two species were ectomycorrhizal, 3 both ecto- and endo-mycorrhizal, and 15 endomycorrhizal. Two species of Ericaceae had ericoid mycorrhizae and one had both ericoid and arbutoid mycorrhizae. Eight species, unexpectedly including three species of Rosaceae and two of Saxifragaceae, completely lacked mycorrhizae. The significance of the findings concerning the Betulaceae, Fraxinus, the Ericaceae, Rosaceae, and Saxifragaceae are discussed, as is occurrence of Cenococcum-type infections among the species.
Distribution of cellular amino acids, protein, and total organic nitrogen during fruitbody development in Flammulina velutipes. I. Growth on sawdust medium
Authors: Gruen Hans E. , Wong William M.
Published: April 2011

Dry weights of stipes and pilei of Flammulina velutipes grown on nutrient-supplemented sawdust increased throughout the growth period. The pilei weighed only slightly less than the stipes. Amounts of total organic nitrogen, α-amino nitrogen, and alkali-soluble protein increased in the whole pileus and stipe as the fruitbodies elongated, but the concentrations on a dry weight basis decreased although they were always highest in the pileus. The concentration of alkali-insoluble nitrogen increased in both structures and was highest in the stipe. Concentrations of total nitrogen and protein in surface mycelium did not change significantly when fruitbodies formed but increased markedly when their growth ceased. An average of 8.3 mg dry weight of spores containing about 0.6 mg of nitrogen was released during the life of the fruitbody. Changes in 18 free and 17 protein amino acids were followed quantitatively in the pileus and stipe. Glutamic and aspartic acids and alanine were always among the four predominant free amino acids. Lysine and arginine concentrations remained low in the stipes but increased considerably in the expanding pilei. Ornithine levels increased strongly in the stipe during the early part of rapid elongation but remained almost constant and low in the pilei. Free proline was detected only in traces. Valine became the most abundant protein amino acid during elongation, especially in the stipe. There was very little bound methionine and cystine. In surface mycelium levels of free amino acids were low before fruiting and close to the end of fruitbody growth. Protein amino acids increased during that interval but their proportions remained virtually unchanged and valine was not predominant. The concentration of urea remained very low in both pilei and stipes during their growth.
Distribution of cellular amino acids, protein, and total organic nitrogen during fruit body development in Flammulina velutipes. II. Growth on potato–glucose solution
Authors: Gruen Hans E. , Wong William M.
Published: April 2011

In Flammulina velutipes grown on potato–glucose solution the dry weight of mycelium decreased when fruitbodies elongated rapidly. Loss of dry weight by aborted primordia and stunted fruitbodies paralleled gains by large fruitbodies. These gains exceeded the losses by the rest of the colony and indicate that large fruitbodies derived their substrates both from the medium and from materials stored in the rest of the colony. Close to 43% of the organic nitrogen in the medium was consumed before fruitbodies formed and only 8% remained at the end of their growth. Concentrations of total nitrogen, α-amino nitrogen, and alkali-soluble protein declined in the mycelium during most of the growth of the fruitbodies and then remained constant except for a slight final increase in protein. Concentrations of these fractions also decreased in the small fruitbodies and stipes of large fruitbodies but increased in the pilei. Changes in total amounts of these fractions show that gains by all fruitbodies during elongation exceeded the losses by the mycelium and that part of their nitrogen continues to be derived from the medium. Changes in 18 free and 17 protein amino acids were followed quantitatively in the colony. Free arginine, glutamic acid, ornithine, and alanine predominated in the mycelium and small fruitbodies during early growth of the latter, but arginine and ornithine decreased steeply thereafter. During rapid elongation of the large fruitbodies the concentration of arginine increased strongly in the pilei. The increase was much less in the stipes, but successive changes in the rest of the colony suggest that arginine is translocated into the large pilei from the mycelium and possibly the small fruitbodies. Aspartic and glutamic acids, leucine, and alanine predominated in protein of the whole colony until the early growth of fruitbodies, but protein composition changed during rapid elongation. The proportion of valine increased in the mycelium and it became the most abundant bound amino acid in large stipes. [14C]Leucine was fed in replacement medium and incorporation of the label was determined in nitrogenous fractions of different colony portions at the onset and termination of fruitbody growth. Most of the label transported into fruitbodies was in the ethanol-soluble free amino acids.
Protein bodies in umbelliferous seeds. III. Characterization of calcium-rich crystals
Authors: Spitzer Ernest , Lott John N. A.
Published: April 2011

The chemical composition of the calcium-rich crystal inclusions present in the seed protein bodies of 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 determined. Using a variety of methods including X-ray diffraction, infrared spectroscopy, microincineration, energy dispersive X-ray analysis, solubility studies, and staining, the chemical composition of the calcium-rich crystal inclusions was identified as calcium oxalate.
Identification of a Casparian band in the hypodermis of onion and corn roots
Authors: Peterson Carol A. , Emanuel Mary E. , Wilson Christine
Published: April 2011

The radial walls of the hypodermis in onion and corn roots were impermeable to the apoplastic fluorescent dye Tinopal CBS. All walls of the hypodermis as well as the walls of the epidermis were autofluorescent when viewed under violet light. After clearing with hot NaOH, however, autofluorescence was observed only in the radial walls of the onion and corn hypodermis and in the walls of the onion epidermis. The fluorescence could be intensified by staining with an extract of Chelidonium majus root. The Casparian band of the onion and corn endodermis likewise acted as a barrier to Tinopal CBS diffusion and continued to autofluoresce after treatment with hot NaOH. It is concluded that a Casparian band exists in the hypodermis of onion and corn roots. In the hypodermis the entire radial wall is occupied by the Casparian band. In longitudinal view, the hypodermal Casparian band appears in all the radial and transverse walls of the cells and is continuous from one cell to the neighbouring cells.
Some observations on methods of estimating the proportions of morphologically similar pollen types in fossil samples
Authors: Gordon A. D.
Published: April 2011

For pollen types whose morphological characters overlap markedly, it is often helpful to be able to estimate the proportions of each type present in a sample of pollen grains. Several numerical methods of estimation have been proposed in recent years. This paper criticizes some procedures that are based on the identification of each pollen grain, rather than the direct estimation of proportions. A class of maximum likelihood models is described and illustrated by the analysis of eight samples of Picea pollen from late Quaternary profiles in eastern North America. The maximum likelihood approach provides an indication of the precision of the estimates, a point considered to be important.
A stimulatory effect of low nitrate levels on nodulation, leghaemoglobin content, nitrogenase activity, and growth of mung-bean plants (Vigna radiata)
Authors: Das Gaurangakumar
Published: April 2011

Mung beans (Vigna radiata) were grown in the field, and measurement of leghaemoglobin and nitrogenase activity of root nodules during plant growth showed a maximum 30 days after sowing, i.e., just when flowering began. Mung beans were also grown in hydroponic cultures with varying amounts of nitrate nitrogen and harvested at 30 day s. The extent of root nodulation, leghaemoglobin accumulation and nitrogenase activity in the nodules, and plant dry weights were found to be maximal at a low concentration (0.5 mM) of nitrate. Dry weights of shoots and roots (exclusive of nodules) and total chlorophyll content of leaves were also increased more by this low concentration than at higher concentrations of 1–3.5 mM. Nodule formation, including leghaemoglobin content and nitrogenase activity, declined with increased nitrate levels. At the highest nitrate levels studied (4.5 and 5 mM) no nodules were formed, but the shoot and root dry matter increased markedly. It is evident from the results that a minimal amount of nitrate nitrogen is essential for efficient symbiotic nitrogen fixation.
A checklist of freshwater algae of the Northwest Territories, Canada
Authors: Sheath Robert G. , Steinman Alan D.
Published: April 2011

A checklist of the freshwater algae from the Northwest Territories has been compiled to add to an algal flora of Canada. The 44 studies included report on 279 bodies of water. A large diversity of algal communities has been examined in these investigations, such as phytoplankton and periphyton in permanent and temporary tundra ponds, polluted and unpolluted high arctic lakes, and subarctic lakes and streams. The flora consists of 212 genera and 1577 subgeneric taxa. The major algal classes represented in this list are the Bacillariophyceae (761 taxa), the Chlorophyceae (481 taxa), and the Cyanophyceae (173 taxa).
White pine in the transition hardwood forest
Authors: Hibbs David E.
Published: April 2011

Eastern white pine (Pinus strobus) in central New England is found in pure stands and as a component of mixed hardwood -pine stands. In older mixed forests, this pine is emergent over the surrounding hardwood canopy. Owing to the only moderate shade tolerance and initial slow growth rate of pine, there has been frequent speculation about how pine could survive and grow in hardwood forests. Results presented here indicate that successful white pine regeneration is achieved (i) by group reproduction in dense hardwood stands (25 m2∙h−1) where the group acts as a buffer around a central and eventually surviving pine; (ii) by single pine seedlings if hardwood competition is not too severe (18 m2∙h−1); (iii) occasionally by advanced regeneration from a previous stand; and, (iv) in mature forests, by regeneration in larger canopy gaps.
Seed banks and seedling occurrence in a high Arctic oasis at Alexandra Fjord, Ellesmere Island, Canada
Authors: Freedman B. , Hill N. , Svoboda J. , Henry G.
Published: April 2011

The sizes and floras of the seed banks and seedling communities are described for a variety of habitats in a high Arctic lowland oasis on Ellesmere Island, located at 79° N latitude. Four disturbed habitats had larger seed banks than did four undisturbed habitats (averaging 3070/m2 vs. 63/m2). The seedling densities measured in the disturbed habitats were also larger (1780/m2 vs. 180/m2). The data indicate that sexual reproduction is important to the herbaceous, short-lived, ruderal species which colonize disturbed sites in the high Arctic. This contrasts with the more conservative strategy of stress-tolerant species that occur in relatively closed and undisturbed habitats, which tend to propagate by vegetative mechanisms.
Morphological characteristics of leaves from some legume forages: relation to digestion and mechanical strength
Authors: Lees G. L. , Howarth R. E. , Goplen B. P.
Published: April 2011

Leaflets of bloat-causing and bloat-safe forage legumes were examined to identify morphological characteristics which might relate to mechanical strength, rate of digestion, and bloat-causing potential. The bloat-causing legumes were alfalfa (Medicago sativa L.), white clover (Trifolium repens L.), and red clover (T. pratense L.). The bloat-safe legumes were cicer milk-vetch (Astragalus cicer L.), birdsfoot-trefoil (Lotus corniculatus L.), and sainfoin (Onobrychis viciifolia Scop.). Only cicer milk-vetch had reticulate secondary and tertiary vein patterns and collenchyma or bundle sheath cells extending from the vascular tissue to both epidermal layers in the primary, secondary, and tertiary veins. Sainfoin and birdsfoot-trefoil leaflets contained tannin sacs beneath the adaxial epidermis and extending into the mesophyll. Sainfoin also had an intermittent subepidermal layer of cells adjacent to the abaxial epidermis. Sainfoin and cicer milk-vetch leaflets were the least disrupted by shaking with glass beads. Digestion of whole leaflets by rumen microorganisms or a purified leaf-macerating enzyme was less extensive in the bloat-safe species. These digestion results and recent findings on the mechanical strength of leaflets from the same species may be related to secondary and tertiary vein patterns and structure.
Sexual reproduction in grand fir (Abies grandis)
Authors: Singh Hardev , Owens John N.
Published: April 2011

Phenology and anatomy of the postdormancy reproductive phase of Abies grandis Lindl, were studied. The dormant microsporangia contained compactly arranged pollen mother cells (PMC). The pollen cones broke dormancy in the 3rd week of February and soon afterwards the PMC entered meiosis. Microspore tetrads formed by the 2nd week of March. Pollen grains were shed at the five-celled stage in the 3rd week of April. The pollen grains were bisaccate and showed a triradiate mark on the proximal pole. The dormant ovulate-cone buds bore rudimentary ovuliferous scales, each with two ovular areas. Ovulate cones broke dormancy at the end of January. Megaspore mother cells differentiated by the end of February and the integument was initiated soon afterwards. A megaspore triad formed in the 2nd week of April. By the 3rd week of April, at the time of pollination, the ovule contained a free-nuclear gametophyte, and the integument had developed a stigmatic micropylar funnel. Numerous microdroplets were observed on the surface of the funnel to which pollen adhered. After pollination the funnel became infolded, enclosing the pollen grains. Pollen germination, pollen tube growth through the nucellus, and syngamy took only 3–4 days and occurred in the 3rd week of June. The female gametophyte was long and bore two or three archegonia. The proembryo consisted of four tiers of four cells each. The suspensors developed from the subterminal tier of cells. The four terminal cells formed the embryonal mass, whose proximal cells elongated and developed into a secondary suspensor. Differentiation of the root apical meristem and the cotyledons in the young embryo occurred in the 1st week of July and the embryo matured in the 3rd week of August.
Jack pine – lichen woodland on sandy soils in northern Saskatchewan and northeastern Alberta
Authors: Carroll Steven B. , Bliss L. C.
Published: April 2011

Open woodland forests dominated by Pinus banksiana occur on sandy soils in northeastern Alberta and northwestern Saskatchewan and are generally even-aged and uniform in height. Ordination techniques were used to divide the stands (n = 38) into the following communities: Pinus banksiana/Vaccinium myrtilloides seral community; Pinus banksiana/Cladina mitis, Pinus banksiana/Vaccinium myrtilloides/Cladina mitis in uplands; and Pinus banksiana–Picea mariana/Ledum groenlandicum/Cladina spp. in lowlands. Fires occur with a mean return interval of 38 years (range at six locations, 28–54 years). Pinus banksiana recolonizes rapidly after fire, and average thickness of lichen cover is reached in 45 years. This is a shorter time interval for recovery than is reported for the Northwest Territories. Stands that escape fire 90+ years become more open in upland sites, but in lowlands Picea mariana becomes codominant with associated shift in lichen species and an increase in bryophytes.
Entomogenous fungi from the Galápagos Islands
Authors: Evans Harry C. , Samson Robert A.
Published: April 2011

Twenty-one species of entomogenous fungi, collected during a mycological survey of the island of Santa Cruz, are listed. Several coccid-associated species are described in detail, including Hirsutella sphaerospora sp. nov. on Eriococcid larvae; Hirsutella besseyi Fisher; and Torrubiella confragosa Mains, putative teleomorph of Verticillium lecanii (Zimm.) Viégas. In addition, Hirsutella darwinii on a spider host is described as new. The entomogenous mycoflora is similar to that of mainland Ecuador and the ecological implications are discussed particularly in relation to coccid populations.
Variegation in Selaginella martensii f. albovariegata. I. Expression and inheritance
Authors: Tanno James A. , Webster Terry R.
Published: April 2011

Selaginella martensii f. albovariegata is a variegated sport which produces distinctly white tissue in an irregular fashion. Typical specimens possess not only variegated branches but some branches exhibiting uniformly green growth and others showing completely white growth. Variegated and green branches often change in character as they grow, while white branches are stable. Leaf variegation patterns are highly variable and strongly influenced by the cell division patterns of early leaf growth. Reciprocal crosses between wild-type S. martensii and f. albovariegata show maternal inheritance of variegation, suggesting cytoplasmic control. Further crosses, involving progeny of selected reciprocal crosses, also indicate a lack of direct nuclear influence on variegation. The details of character expression and inheritance can be accounted for on the basis of a random sorting of normal and defective cytoplasmic factors at cell division. Recent characterizations of chloroplast DNA for several species of green plants suggest that the DNA molecules within the plastid may represent the sorting factor.
Electrophoretic analysis of the species and population structure of the diatom Asterionella formosa
Authors: Soudek Jr. D. , Robinson G. G. C.
Published: April 2011

One hundred and one clones from 25 North American and 7 European populations of Asterionella formosa Hass. were isolated or obtained from other investigators. Twenty populations were represented by two or more isolates obtained either simultaneously or at different times of the year.Soluble proteins, present in crude extracts of homogenized cells from batch cultures of each isolate, were separated in polyacrylamide gels and stained either with a nonspecific protein stain or for enzyme activity. Six enzymes (leucine aminopeptidase, alkaline phosphatase, glutamate dehydrogenase, malate dehydrogenase, acid phosphatase, and esterase) were examined but only the latter three, together with general protein, showed variation in electrophoretic banding patterns.There was no detectable variation (with one possible exception) among multiple isolates from the same population, suggesting that the populations are clonal or at least highly homogeneous genetically. This was true both for contemporaneous isolates and for isolates obtained at different times of the year and in different years.On the other hand, isolates from different populations differ by 3 to 28 bands out of 41. The frequency distribution of a measure of dissimilarity between pairs of population-specific electrophoretic patterns is unimodal, indicating that the observed variation is essentially continuous and that the collection of isolates is not comprised of a small number of discrete races. However, identification of groups of populations by means of hierarchical cluster analysis in terms of their geographical origin and of the ecological characteristics of their habitat was possible to a limited extent.
The cytogeography of Aster lanceolatus. II. A preliminary survey of the range including A. hesperius
Authors: Semple J. C. , Chmielewski J. G. , Rao K. Sankara , Allen G. A.
Published: April 2011

Aster lanceolatus has been reported to occur at five ploidy levels in at least some parts of its range: 2n = 32, 40, 48, 56, and 64. Chromosome number determinations from 127 populations from throughout the range are reported here. Octoploid plants were frequent from Nova Scotia to Virginia and across to the Great Plains. Hexaploids were predominant in some northern parts of the range, but very rare or absent in the southern portions. Tetraploids occurred sporadically in the northeast, were common in parts of southern Ontario and Michigan, and were not found in the southern parts of the range. Odd-level polyploids occurred rarely in areas where two even ploidy levels were sympatric. On the Great Plains A. lanceolatus intergraded with A. hesperius with which it is perhaps conspecific. Thirty-four hexaploid and octoploid populations of this western "species" were found in two transects across the northern portion of the prairies and from scattered montane and southern locations. Octoploids were frequent in the western areas while hexaploids were frequent in the northeastern area. Some aneuploidy was found in the montane populations of octoploids. One decaploid 2n = 80 population was found in Wisconsin that is best labelled as A. coerulescens DC. sensu Rosendahl and Cronquist.
A numerical analysis of karyotypes in the genus Pseudotsuga
Authors: El-Kassaby Yousry A. , Colangeli Anna M. , Sziklai Oscar
Published: April 2011

Numerical data were collected from the karyotypes of seven species in the Pseudotsuga genus. These included two North American species, P. macrocarpa and P. menziesii, the latter with two varieties (P. menzeisii var. menziesii and P. menziesii var. glauca) and five Asiatic species, P. japonica from Japan, P. wilsoniana from Taiwan, and P. forrestii, P. sinensis, and P. gaussenii from China. A stepwise discriminant function analysis was employed to test the validity of using karyotype data for characterizing the cytogenetical and the geographical differences of each species. Good discrimination was shown among P. macrocarpa and the Asiatic species. The discrimination among the Asiatic species was further improved when the well-separated P. macrocarpa was omitted. A high level of discrimination was observed between the two P. menziesii varieties. This statistical technique was particularly helpful in selecting variables that best separated the taxa. To our knowledge, these results provide the first reported karyotype numerical analysis for the Pseudotsuga genus as well as the first reported karyotype analysis for P. gaussenii.
A pattern mimic of Calathea veitchiana (Marantaceae) from Peru
Authors: Kennedy Helen
Published: April 2011

Calathea pseudoveitchiana, a leaf pattern mimic of the unrelated C. veitchiana, is described as new. The leaf pattern type is charahcteristic of species from Amazonian Peru and Ecuador. Calathea pseudoveitchiana is in Calathea series Nudiscapae, while C. veitchiana is in series Comosae. Calathea longipetiolata, from Perú, is also described as new.
Distribution of prairies and solonetzic soils in the Peace River district, Alberta
Authors: Wilkinson K. , Johnson E. A.
Published: April 2011

A study of 13 native prairie remnants in the Peace River district of Alberta revealed two community types: a Stipa spartea var. curtiseta – Carex spp. – Artemisia frigida community found on steep, south-facing slopes and a more widespread Carex spp. – Danthonia intermedia – Stipa spartea var. curtiseta community situated on solonetzic-order soils. By using early land survey records and recent soil survey data, a close correlation was found between the large tracts of prairie vegetation and the distribution of solonetzic soils. The solonetzic soils appear to support grasslands and not forests because of their unfavorable ratios of Na to Ca, hard, columnar B-horizon, and relatively impermeable clay pan close to the surface.
Inoculation studies of Juncus articulatus with Entorrhiza casparyana (Ustilaginales)
Authors: Fineran Judith M.
Published: April 2011

Teliospores of Entorrhiza casparyana from soil infected Juncus articulatus L. in well-drained and waterlogged soils under glasshouse conditions. After 3.5 months the maximum infection perplant was 2546 galls which weighed 1.2 g (or 18.5% of the root dry weight and 9.6% of the total dry weight of the plant). After 8.5 months the maximum infection per plant was 4267 galls which weighed 14.3 g (or 54.9% of the root dry weight and 29.7% of the total dry weight of the plant). Galls were relatively evenly distributed on the roots in well-drained soils but not in waterlogged soils. The effect on plant appearance and growth (measured on a dry weight basis after 3.5 months) was insignificant, explaining why infected plants are difficult to detect in the field.
Leaf survival of woody plants in deciduous broad-leaved forests. 1. Tall trees
Authors: Kikuzawa Kihachiro
Published: April 2011

Seasonal changes in mean numbers of leaves per shoot were shown for 41 tall-tree species in deciduous broad-leaved forests in Hokkaido, northern Japan. Three types of leaf-emergence pattern were recognized; namely (1) succeeding type, (2) intermediate type, and (3) flush type. The two species showing the succeeding type emergence pattern have homonomous winter buds characterized by one-lamina and two-stipules sets. The species of intermediate- or flush-type emergence pattern usually have heteronomous winter buds with several bud scales. A negative correlation was found between leaf-emergence duration and number of bud scales. Species having a long leaf-emergence duration were open land or gap invaders. Among them, those having long leaf-fall duration were found in riverside forests. On the other hand, species showing flush-type leaf emergence with short duration and almost simultaneous leaf fall with also short duration were mainly found in mixed-forest stands. The longevities of leaves at the basal part of the shoot were short in the species whose bud scales have not entirely differentiated from foliage leaves. The main evolutionary trend in the shoots was suggested to be from homonomous to heteronomous structure and towards the clear distinction between foliage leaves and bud scales.
The distribution and ultrastructure of the endophyte of toxic tall fescue
Authors: Hinton D. M. , Bacon C. W.
Published: April 2011

The symptomless relationship of tall fescue grass (Festuca arundinacea Schreber) and its endophytic parasitic fungus, Sphacelia typhina (Fr.) Tul. (= Acremonium coenophialum fide Morgan-Jones et Gams), was studied with light and electron microscopy. The fungus was intercellular and was distributed throughout the plant with the exception of roots and leaf blades. The highest concentration of the fungus occurred in the base of the leaf sheath. In the seed the fungus was sequestered between the epithelial cells of the scutellum and the starchy endosperm. The seed embryo was not infected; infection was also not evident during the early stages of seed germination. At the ultrastructural level, the parasitic relationship was established in tissues where there were intercellular spaces. Micrographs indicated that the fungus did not separate the middle lamella of host cells, nor did it produce any obvious alteration in host cell morphology. Ultrastructural characteristics of the fungus depended on the age and type of fescue tissue. Hyphal cells possessed numerous vesicular and multivesicular structures, and in some sections, the hyphal walls were inordinately thickened and with or without an extracellular matrix. The fungus appeared to colonize the innermost areas of tissues in all infected organs and no signs of egress were ever detected.
A morphometric study of effective nodules induced by Rhizobium loti and Bradyrhizobium sp. (Lotus) on Lotus pedunculatus
Authors: Wood Susan M. , Layzell David B. , Newcomb William , Pankhurst Clive E.
Published: April 2011

Effective root nodules formed on Lotus pedunculatus by Rhizobium loti NZP2037 and Bradyrhizobium sp. (Lotus) CC814s were examined by light and electron microscopy. NZP2037 nodules were larger than CC814s nodules as a result of a much thicker nodule cortex. The smaller CC814s nodules had a much larger infected zone and, consequently, larger volumes of infected cells, peribacteroid space, and host cytosol per nodule. As well, CC814s nodules demonstrated a significantly higher number of bacteria which typically contained prominent polar bodies and beta-polyhydroxybutyrate (PHB) granules. The bacteria of NZP2037 nodules lacked the polar bodies, but PHB deposits were occasionally observed. A correlated physiological study in which acetylene reduction was used to estimate nitrogen fixation showed CC814s nodules to be more active than NZP2037 nodules (Pankhurst, C. E., and D. B. Layzell. 1984. Physiol. Plant. 62(3) : 404–409.). This measured difference in nitrogen-fixing activity was considered due to the degree of infection and bacterial proliferation as well as differences in the carbon and nitrogen metabolism of the two nodule types. The significance of the structural observations and morphometric analyses and their relationship to differences in nitrogen fixation are discussed.
Population biology of Ammophila breviligulata and Calamovilfa longifolia on Lake Huron sand dunes. I. Habitat, growth form, reproduction, and establishment
Authors: Maun M. A.
Published: April 2011

Some aspects of the population biology of two dune-forming perennial grasses, Ammophila breviligulata Fern. and Calamovilfa longifolia (Hook) Scribn., growing along Lake Huron shoreline, were investigated under natural and controlled conditions. Plants of A. breviligulata exhibit erratic flowering, ranging from no panicles in some areas to 16 per hundred tillers in others. Calamovilfa longifolia plants occur as single clumps of varying diameters and flower profusely. Ammophila breviligulata expands into adjacent areas by producing plagiotropic rhizomes ranging in length from 1 to several m and then producing ramets on some of the nodes. Such a growth form is best suited for rapid colonization of bare areas. Clumps of C. longifolia expand outward in concentric circles through the development of diving rhizomes, and the radius of a clump increases by about 15 to 31 cm per year. This growth form is well suited for local occupancy. Ammophila breviligulata is more tolerant of burial (100 cm) in sand than C. longifolia (60 cm). Calamovilfa longifolia produces larger number of caryopses per square metre than A. breviligulata. The weight per caryopsis of both species is similar, but the significantly greater surface area per fruit of A. breviligulata improves its flotation ability in water, thus facilitating long-distance dispersal of fruits. Establishment of C. longifolia plants under natural conditions occurred almost exclusively from seedlings. In contrast, the establishment of A. breviligulata seedlings was rare and almost all new plants along the beach originated from clonal fragments cast on the drift line by high waves.
Succession and biomass allocation as controlled by Sphagnum in an Alaskan peatland
Authors: Luken J. O. , Billings W. D. , Peterson K. M.
Published: April 2011

The vascular plant vegetation on active Sphagnum hummocks, on senescent hummocks, and in hollows of an Alaskan peatland was measured in several ways. Aboveground biomass and net primary production were greatest on senescent hummocks. Growth of hummock-forming Sphagnum mosses caused a significant increase in stem density and adventitious shoot production of Ledum palustre and Andromeda polifolia, while Vaccinium vitis-idaea showed a decrease in stem density; Rubus chamaemorus was unaffected. Overgrowth of vascular plants by Sphagnum resulted in significantly higher leaf/stem ratios in most of the shrub species. In addition, leaf turnover rates of the evergreen shrubs were modified. The growth of Sphagnum hummocks leads to a developmental stage in the vascular vegetation in which a large amount of structural biomass is present relative to leaf biomass. The rate of microsuccessional change in hummock–hollow complexes appears to be relatively high, at least in comparison to those macrosuccessional processes associated with permafrost formation and melting.
Sclerotia of Aspergillus aculeatus
Authors: Jarvis W. R. , Traquair J. A.
Published: April 2011

Sclerotial development in Aspergillus aculeatus is described for the first time. The sclerotium originates as a knot of interwoven hyphae. The mature sclerotium has a rind of flattened hyphae, below which are two cortical layers and a medulla. The outer cortical layer has isodiametric cells and the inner layer has somewhat radially elongated polyhedral cells. The thick walls of the cortical cells are perforated by simple septal pores. The medulla comprises a loosely interwoven mass of hyphae. Sclerotia remain pale luteous.
Forty-one years of population change and community succession in aspen forests on four soil types, northern lower Michigan, U.S.A.
Authors: Roberts Mark R. , Richardson Curtis J.
Published: April 2011

In 1938, four permanent 0.04-ha (0.1-acre) plots were established in pioneer aspen (Populus grandidentata Michx. and P. tremuloides Michx.) forests on dry-mesic to wet-mesic soils in Michigan. These sites are representative of the soils and vegetation types found in the region. Patterns of survival, growth, and recruitment of individual woody stems are determined from remeasurements in 1945, 1951, 1955, 1968, 1973, and 1979. Five patterns of change in species populations are identified, reflecting differences in reproductive characteristics and physiological requirements of the species: (1) early dominance, (2) delayed dominance, (3) persistence, (4) progressive recruitment, and (5) late recruitment. Patterns 1, 3, and 4 predominated on dry-mesic soils, reflecting slow replacement of aspen by Pinus resinosa Ait. and P. strobus L. from seedling origin, whereas all five patterns occurred on the mesic soil where Acer rubrum L., A. saccharum Marsh., and Fagus grandifolia Ehrh. increased in importance through both vegetative sprouting and seedling establishment. Recruitment on the dry-mesic soils did not correspond to the stages of development of the aspen overstory as determined from −3/2 thinning curves. In contrast, recruitment and growth in the understory appeared to be dependent upon the occurrence of canopy openings on the mesic soil. Species populations responded to insect defoliation on the wet-mesic plot, illustrating the importance of understanding population dynamics in studies of succession.
Biosynthesis of 3-acetyldeoxynivalenol and other metabolites by Fusarium culmorum HLX 1503 in a stirred jar fermentor
Authors: Miller J. David , Blackwell Barbara A.
Published: April 2011

The formation of 3-acetyldeoxynivalenol (ADON) and other secondary metabolites of Fusarium culmorum in a stirred jar fermentor is described in relation to changes in concentrations of sugars, N, P, and O2, and in pH in the medium as well as changes in cellular parameters. The addition of sodium [1-13C]acetate to the fermentation demonstrated that the conditions used resulted in the biosynthesis of ADON instead of other primary and secondary metabolites such as culmorin, dihydroxycalonectrin, and sambucinol for all but the early stages of the fermentation. Enrichment studies also revealed that dihydroxycalonectrin was not an important intermediate of ADON. Biosynthesis of ADON was apparently induced by nitrogen limitation. At the end of the fermentation, ca. 710 mg L−1 ADON was obtained.
Holocene history of forest trees in southern Ontario
Authors: Bennett K. D.
Published: April 2011

Three new Holocene pollen percentage and accumulation rate diagrams for southern Ontario are presented. They greatly increase the available information on the history of the area's forest trees and permit a discussion of the competitive interactions that have brought about the forest pattern seen today. In the earliest Holocene, the forests were dominated by Picea, which was replaced by first Pinus banksiana–resinosa and then Pinus strobus. In extreme southern Ontario, Pinus strobus was replaced by Acer saccharum and Fagus grandifolia, but in the area east of Georgian Bay, Tsuga canadensis became the dominant, and near Mattawa, Betula (probably lutea). Late Holocene stability of forests is considered to be a function of the lack of taxa better able to compete than those already present.
Sources of morphological variation and organization within and among populations of Balsamorhiza sagittata
Authors: Robson K. A. , Scagel R. K. , Maze J.
Published: April 2011

Comparisons of differences between morphological means of individual plant parts indicate that the greatest source of variation in two populations of Balsamorhiza sagittata is the individual plants within populations; within-population diversity is greater than among-population diversity. Variable covariance and correlations differ between individual plants and there are subgroups of interrelated variables that can be tied to developmental phenomena. The relationship between developmental phenomena and these groups of variables suggests a relationship between organizational, as reflected in variable interrelationships, and ontogenetic variation. These results are not adequately explained by neoDarwinian theory but are explained more comprehensively by a theory of evolution that views biological change over time as an intrinsically driven self-organization, accompanied by an increase in complexity (a manifestation of the "Second Law of Thermodynamics" as it applies to open systems).
Phenylalanine ammonia-lyase activity in soybean hypocotyls and leaves following infection with Phytophthora megasperma f.sp. glycinea
Authors: Bhattacharyya M. K. , Ward E. W. B.
Published: April 2011

Phenylalanine ammonia-lyase activity increased rapidly beginning 2 h after inoculation with Phytophthora megasperma (Drechs.) f.sp. glycinea (Hildeb.) Kuan & Erwin race 1 in unwounded hypocotyls of soybean cv. Harosoy 63 (resistant) but did not change significantly in cv. Harosoy (susceptible). Small increases in phenylalanine ammonia-lyase activity also were caused by wounding. Activity increased more slowly in hypocotyls (cv. Harosoy 63) wounded just before inoculation than in intact inoculated hypocotyls, but most activity developed in hypocotyls wounded 12 h before inoculation. There were comparable effects of wounding on symptom development. Trifoliolate leaves of 14-day-old cv. Harosoy 63 plants are resistant, but trifoliolate leaves of 12-day-old cv. Harosoy 63 plants and of 14-day-old cv. Harosoy plants are susceptible to race 1. Increases in phenylalanine ammonia-lyase activity following inoculation were demonstrated only in 14-day-old Harosoy 63 plants but not until 24–36 h after the inoculation. Significant accumulation of glyceollin occurred by 24 h. Susceptible trifoliolate leaves of 12-day-old cv. Harosoy 63 plants produced only low levels of glyceollin following either infection or treatment with the abiotic elicitor AgNO3, whereas trifoliolate leaves of 14-day-old cv. Harosoy plants produced high levels of glyceollin in response to AgNO3. It is concluded that trifoliolate leaves of 12-day-old, as opposed to 14-day-old, cv. Harosoy 63 plants have not developed mechanisms that trigger responses to either infection or the abiotic elicitor or they are deficient in metabolic processes that support glyceollin biosynthesis or other defense-related responses.
Buried seed populations in the montane, subalpine, and alpine belts of Mont Jacques-Cartier, Quebec
Authors: Morin Hubert , Payette Serge
Published: April 2011

The analysis of the total buried seed population along an altitudinal gradient in the Mont Jacques-Cartier area, southern Quebec, reveals a close relationship between buried seed flora and aboveground vegetation. Eighty-one percent of the species present in the total buried seed population were present in the aboveground vegetation of the study sites. The total number of seeds in the buried seed population, the number of species in the total buried seed population, and the number of seeds and species in the seed bank did not show any significant linear correlation with altitude. A shift from a boreal to an arctic–alpine buried seed population with increasing altitude was observed, instead of a decrease in seed bank size.
Serological relationships between pathogenesis-related leaf proteins from four Nicotiana species, Solanum tuberosum, and Chenopodium amaranticolor
Authors: Parent Jean-Guy , Hogue Richard , Asselin Alain
Published: April 2011

Leaves of Nicotiana tabacum L. cv. Xanthi-nc, Nicotiana clevelandii Gray, Nicotiana rustica L., and Chenopodium amaranticolor Coste & Reyn. were infected with the U1 strain of tobacco mosaic virus and leaves of Nicotiana sylvestris Speg. & Comes and Solanum tuberosum L. cv. Kennebec were infected with the U2 strain. After 10 days, pathogenesis-related (PR) proteins from intercellular fluid extracts were separated by nondenaturing polyacrylamide gel electrophoretic (PAGE) systems for acidic or basic proteins, sometimes followed by denaturating PAGE with lithium dodecyl sulfate. PR proteins were then transferred to nitrocellulose to determine serological relationships. Using an antiserum directed against native PR protein b4 from 'Xanthi-nc' tobacco, serologically reacting acidic PR proteins could be detected in all plant species. Except for potato, related basic PR proteins were also found in all species. Serological relationships were further studied between 'Xanthi-nc' tobacco and 'Kennebec' potato PR proteins separated in PAGE gels under native conditions. Potato basic PR proteins with Rfs of 0.83, 0.85, and 1.00 were serologically related to tobacco acidic PR proteins of the b4 group. Potato acidic PR proteins with Rfs of 0.56, 0.58, 0.61, and 0.64 were related to tobacco acidic PR proteins of the b4 group. Potato acidic PR proteins with Rfs of 0.18 and 0.21 reacted with an antiserum against tobacco PR protein b9. Three potato acidic peroxidases were also serologically related to tobacco peroxidases b6a and b7a. Analysis with denaturing PAGE systems gave results difficult to interpret because bovine carbonic anhydrase, for example, cross-reacted with an antiserum against tobacco PR protein b4. A similar relationship could not be detected in PAGE systems under native conditions.
Spores of Lycopodium and Selaginella of North Pacific America
Authors: Heusser Calvin J. , Peteet Dorothy M.
Published: April 2011

Morphological descriptions and keys apply to spores of eight species of Lycopodium (L. alpinum, L. annotinum, L. clavatum, L. complanatum, L. inundatum, L. obscurum, L. selago, and L. sitchense) and seven species of Selaginella (S. densa, S. douglasii, S. oregana, S. selaginoides, S. sibirica, S. wallacei, and S. watsonii). Spores are radiosymmetric, heteropolar, tetrahedral, and trilete. The most workable characters of use in identification of spores of Lycopodium are type sculpture (mostly reticulate but also foveolate and rugulate) and the presence, continuity, and absence of sculpture on proximal and distal faces. Spores of Selaginella are distinguished by the presence or absence of a perine, perine thickness, microsculpture, and appearance of cristae. Modern, Holocene, and Pleistocene distribution records of L. selago and S. selaginoides are reviewed for the purpose of developing the Quaternary history of Lycopodium and Selaginella in North Pacific America. They illustrate the importance of refugia in Washington, the Queen Charlotte Islands, and Japan – eastern Asia, which were noteworthy distribution centers during and following Wisconsin glaciation.
Interaction between the ectomycorrhizal fungus Paxillus involutus and Pinus resinosa induces resistance to Fusarium oxysporum
Authors: Duchesne Luc C. , Peterson R. L. , Ellis Brian E.
Published: April 2011

Inoculation of Pinus resinosa Ait. seedlings with the ectomycorrhizal fungus Paxillus involutus Fr. resulted in a 47% increase in resistance to subsequent infection by the root pathogenic fungus Fusarium oxysporum f.sp. pini as compared with control seedlings. This increase in seedling survival was associated with a sixfold decrease in the sporulation of F. oxysporum in the rhizosphere of seedlings inoculated with Pax. involutus when compared with the rhizosphere of control seedlings. Extraction and bioassay of the seedling rhizosphere and seedling tissues indicated that inoculation with Pax. involutus led to a fivefold increase in antibiotic activity in the rhizosphere of the seedlings treated with Pax. involutus. Most or all of the fungitoxicity was localized in the rhizosphere. Disease suppression by Pax. involutus in P. resinosa is, therefore, associated with an increase of fungitoxic chemicals in the rhizosphere of seedlings.
Role of temperature in regulating the timing of germination in Portulaca oleracea
Authors: Baskin Jerry M. , Baskin Carol C.
Published: April 2011

The peak of germination of autumn-sown seeds of Portulaca oleracea was between 21 May and 21 June, when mean daily maximum and minimum temperatures were 30.7 and 17.4 °C, respectively. Fresh seeds collected in October germinated to 13 and 94% at 30:15 and 35:20 °C thermoperiods, respectively, in light, and to 0% in darkness. Seeds were buried in October 1975 and exhumed in December 1975 through September 1976. In light, exhumed seeds germinated to 69–100% at 30:15 and 35:20 °C,to 1–80% at 20:10 °C, and to 0–52% at 15:6 °C; in darkness they germinated to 5–55% at 30:15 and 35:20 °C and to0% at 20:10 and 15:6 °C. Germination at 20:10 °C did not exceed 50% until mid-April, and it did not exceed 50% at 15:6 °C until June. Fresh seeds were buried at 5, 15:6, 20:10, 25:15, 30:15, and 35:20 °C, and after 0, 1, 3, and 5 months, seeds from each temperature were tested in light and darkness at the five thermoperiods. The minimum temperature at which 50% or more of the seeds germinated in light decreased with an increase in afterripening temperature. The high temperature requirement for complete afterripening and for germination of partially afterripened seeds prevents germination of this summer annual in temperate regions until late spring and early summer.