bluuebunny/crossref_metadata_2025 huggingface dataset:
Formation of the primary protective layer and phellogen after leaf abscission in peach
Authors: Biggs A. R. , Northover J.
Published: April 2011

Potted peach trees (Prunus persica (L.) Batsch cv. Loring) were mechanically defoliated and the influence of temperature on formation of the primary protective layer and phellogen generation in the leaf abscission region was examined histologically. Plants maintained at 7.5, 12.5, and 17.5 °C showed first indications of primary protective layer formation at 18, 9, and 6 days, respectively. Subsequent generation of phellogen and the appearance of the first phellem cell were observed at 30, 18, and 12 days, respectively. The primary protective layer formed approximately 700 μm proximal to the separation zone and was composed of cells with lignified walls and thin suberin linings.
Hericium in North America: cultural characteristics and mating behavior
Authors: Ginns J.
Published: April 2011

Cultural characteristics observed in nearly 75 cultures were the basis for the descriptions of the four North American species of Hericium. Comparison of the cultural characters showed subtle differences among the species. Similarities in cultural characters led to the evaluation of nearly 4100 intercollection matings to confirm the identity of the cultures and establish species circumscriptions. As a result all Canadian cultures labelled H. erinaceus were reassigned to H. americanum. The presence of H. erinaceus in Canada could not be confirmed. Matings confirmed the conspecificity of North American and European cultures of H. coralloides and H. erinaceus. Intracollection matings established or confirmed that H. abietis, H. americanum, H. coralloides, and H. erinaceus have a bifactorial mating system.
A geometric analysis of somatic embryo formation in carrot cell cultures
Authors: Schiavone F. Mark , Cooke Todd J.
Published: April 2011

Cell cultures of the domesticated carrot, Daucus carota L., are a convenient model system for studying somatic embryogenesis. Various geometric measurements were used to characterize the different stages of carrot embryo formation in an attempt to define the major morphological events associated with the transitions to successive stages. Contrary to the qualitative impressions obtained from previous research, a developmental stage with a distinctive growth pattern is observed between the globular and heart stages of carrot embryogenesis. After the globular stage, which is characterized by isodiametric expansion, the present analyses demonstrate that the future hypocotyl axis undergoes considerable elongation before the emergence of the cotyledons that marks the initiation of the heart embryo. Because of the elongate shape of this intermediate stage, it is termed the oblong embryo. Incipient procambium can also be recognized in the central axis of the oblong embryo. The formation of a torpedo embryo from a heart embryo does not involve any apparent changes in the relative growth of various parts of the heart embryo but rather results from the continuous increase in overall size. These results are discussed in terms of their implications for future investigations into the physiological mechanisms of somatic embryogenesis.
Decomposition of timothy (Phleum pratense) litter on a reclaimed surface coal mine in Alberta, Canada
Authors: Durall D. M. , Parsons W. F. J. , Parkinson D.
Published: April 2011

Three plots differing in the time since their reclamation (7, 3, and 1 years) were selected for a 3-year decomposition study of timothy (Phleum pratense L.) litter on a surface coal mine in Alberta, Canada. A comparison between single and double exponential functions showed that mass losses were best described by double exponential decay functions, which revealed a trend of decreasing mass loss rate of the labile and recalcitrant litter fractions with increasing time following reclamation. This study suggests that abiotic factors control the release of the labile fraction during the initial phase of decomposition, whereas biotic factors control the decomposition of the recalcitrant fraction with minimal influences imposed by the measured microsite parameters. Timothy biomass formed a much larger component of the total biomass on the 7-year plot (39%) than on the 3-year (13%) and 1-year (13%) plots. Reports in the literature indicate that timothy has low nutrient requirements and is tolerant of low soil fertility. The presence of this short-lived perennial at high biomass levels with a relatively small total plant biomass on the 7-year-old plot, along with a relatively low rate of timothy litter decomposition, supports the suggestion that spoil on the oldest plot is deficient in available nutrients.
The ecology of Ramalina menziesii. II. Variation in water relations and tensile strength across an inland gradient
Authors: Larson D. W. , Matthes-Sears U. , Nash III T. H.
Published: April 2011

The lichen Ramalina menziesii Tayl. shows a clear gradient in morphology from coastal to inland sites. Experiments were conducted to evaluate the impact of this morphological variation on water uptake, water loss, and tensile strength properties. The results show that none of these characters is greatly influenced by morphological variation. Artificial loading of thalli with NaCl altered the wetting and drying responses in the same direction as was found in coastal material. This implies that the presence of elevated intrathallus concentrations of NaCl found near the coast is mainly responsible for the small differences in wetting and drying characteristics. It further implies that the morphological variation seen in the field is not an adaptation to the conditions near the coast but, rather, is the imposed result of a permanently moist, cool, and salty environment.
Nutrient-limitation effects on the biochemical composition of Cyclotella meneghiniana (Bacillariophyta): an experimental and statistical analysis
Authors: Millie David F.
Published: April 2011

The lipid, fatty acid, glucan, protein, and chlorophyll contents of nutrient-starved and nutrient-stressed cells of Cyclotella meneghiniana Kütz. were investigated in batch and semicontinuous culture experiments, respectively. In batch culture experiments, cells were removed from nutrient-replete media, resuspended in silicon-, nitrogen-, or phosphorus-deficient media according to a 2 × 3 factorial design in fractional replication, and analyzed 3 and 9 days after transfer to treatment media. Silicon starvation caused a significant increase (300%) in cell protein content. In semicontinuous culture experiments, cells were grown in media with silicon, nitrogen, or phosphorus at concentrations lower than necessary for maximum rates of growth. Within each nutrient experiment, dilution rates of 0.10, 0.25, and 0.50∙day−1 produced three distinct rates of nutrient supply per cell. Cell lipid : glucan ratios significantly decreased (50%) with increasing silicon supply rate. Cell lipid, glucan, and protein significantly increased (300%) with increasing nitrogen supply rate. Cell lipid and glucan significantly increased (300 and 400%, respectively) with increasing phosphorus supply rate. Fatty acids of extracted lipids generally possessed carbon chain lengths of 14 to 24. However, carbon chain lengths of fatty acids from silicon-stressed cells ranged from less than 14 to 18. No distinct differences in fatty acid composition were observed among supply rates within silicon- and nitrogen-stressed cultures.
Étude ultrastructurale et cytochimique de la paroi cellulaire chez Gracilaria verrucosa (Rhodophyceae)
Authors: Verdus M. C. , Christiaen D. , Stadler T. , Morvan H.
Published: April 2011

The cell wall ultrastructure of Gracilaria verrucosa was investigated, using electron microscopy, before and after extraction of the agar by two techniques. In this species, the agar is the main constituent of the cell wall matrix. The amorphous part of the cell wall disappeared after extraction and some structural modifications of the fibrillar squeletic phase were observed. These observations showed that a mild extraction method improves the colloid purity.
Comparison of the structures of even-aged aspen stands in three geographic regions
Authors: Pielou E. C. , Campbell J. S. , Lieffers V. J.
Published: April 2011

Even-aged aspen (Populus tremuloides Michx.) stands in regions with contrasting climates differ from one another in the growth rates of individual stems and in the rates at which they self-thin. The dependence on stand age of four statistics describing stand structure (the mean, standard deviation, and skewness of the distribution of tree girths and the number of trees in a 400-m2 plot) were studied in three geographical regions: northern Alberta, Yukon, and the Foothills of the Rocky Mountains in southern Alberta. Each region has unique stand statistics. The annual radial increment is least in the Yukon, presumably because of the short growing season. Foothills plots are unique in having girth distributions that are approximately symmetrical at all ages; this contrasts with the other two regions, where girth distributions exhibited positive skewness in young stands and skewness decreased with age. Also in Foothills plots, the standard deviations of the girths increased more slowly with age than in the other two regions. A model was devised to simulate the progressive changes in these statistics in a stand as it ages. To run the model, one begins with data from an actual, observed stand for which the distribution of the trees in different size classes is known. It is then assumed that the trees grow; the growth rate of a tree is greater the larger the tree was initially. Simultaneously, trees die; the probability that a tree will die is greater the smaller the tree was initially. Thus, the values that the descriptive statistics of a given young stand are expected (according to the model) to have when the stand is old can be predicted; the predictions can be compared with current statistics of observed stands that are already old.
Localization of glycopeptides and race-variable polypeptides in urediosporelings and urediosporeling walls of Puccinia graminis tritici; affinity to concanavalin A, soybean agglutinin, and Lotus lectin
Authors: Kim W. K. , Howes N. K.
Published: April 2011

Detergent-soluble polypeptides from urediosporelings and purified germ-tube walls of urediosporelings of wheat stem rust, Puccinia graminis f.sp. tritici, races C1(17), C17(56), and C36(48) were separated by two-dimensional isoelectric focusing – polyacrylamide gel electrophoresis. More than 280 polypeptides were distinguished by Coomassie brilliant blue staining in each race, and there were 18 polypeptides that varied among the three races, 7 of which were coincident with urediosporeling wall polypeptides. Polypeptides transferred from two-dimensional gels onto nitrocellulose membrane were either stained with India ink or probed with concanavalin A – peroxidase for the location of concanavalin A binding glycoproteins. Of 97 concanavalin A binding glycoproteins in urediosporelings, 41 were coincident with polypeptides that stained with Indian ink and 3 were coincident with race-variable polypeptides. The walls of urediosporelings contained few polypeptides that stained with Coomassie brilliant blue or India ink, but most were concanavalin A binding. None of the polypeptides had affinity to soybean agglutinin or Lotus lectin, suggesting that galactose or fucose is not a terminal sugar moiety in these polypeptides. We conclude that race-variable polypeptides are located both within the cytoplasm and in the walls of urediosporelings, but most are not glycosylated.
The distribution and reproductive phenology of intertidal fleshy crustose algae in Washington
Authors: Dethier Megan N.
Published: April 2011

Fleshy (noncalcified) crustose algae are abundant throughout the intertidal zone in Washington State. Crusts include members of the Chlorophyta, Phaeophyta, Rhodophyta, Cyanobacteria, and marine lichens and represent a variety of life-history patterns. Some of the 14 taxa studied are observed only in specific habitats (e.g., only in the low or high intertidal zone or in pools), whereas others are broadly distributed throughout the intertidal zone. All crusts are patchy in their distribution, and their thicknesses show no trends with tidal height. The reproductive periodicity of 10 common fleshy species was studied over 2 years. Most crusts reproduce in the fall and winter, but none is rigidly tied to a seasonal pattern. A key to the fleshy crusts is provided.
Histochemistry of lignin and suberin deposition in boundary layers formed after wounding in various plant species and organs
Authors: Rittinger P. A. , Biggs A. R. , Peirson D. R.
Published: April 2011

Wound responses in a variety of injured plant tissues were assessed using conventional lignin tests and fluorescence techniques for suberin detection in tissues present at the time of wounding. The tissue assessed included twigs of four conifer species, barley and cherry foliage, fern rachis, potato tuber, carrot root, musksmelon cotyledons, and cucumber hypocotyl. Apple leaves infected by a leaf spotting fungus (Botryosphaeria obtusa) were also examined. All tissues, except barley and apple foliage and fern rachis, formed a morphologically distinct lignosuberized boundary layer from cells present at the time of wounding. The boundary layer consisted initially of cells with lignified walls which with time developed suberin lamellae. In the fern rachis, the boundary layer was suberized in the absence of lignin. In the wounded barley and infected apple foliage, neither lignin nor suberin was detected histochemically.
Vegetative proliferation in inflorescences of red fescue (Festuca rubra s.l, Poaceae)
Authors: Aiken S. G. , Lefkovitch L. P. , Darbyshire S. J. , Armstrong K. C.
Published: April 2011

A continuous range of variation in vegetative proliferation among members of the red fescue complex is documented in (ii) the number of spikelets proliferating in the inflorescence, (ii) the position where initiation of proliferation occurs, (iii) the rachilla, where abnormal elongation may result in internodes 3–10 mm long, and (iv) the position of proliferation, which may be either lateral or terminal on the rachilla. Both facultative and obligatory vegetative proliferation occur. Recorded chromosome counts of 2n = 49, 50, 63, and 70; low pollen stainability; absence of seed; and occurrence of proliferation in spikelets of known hybrids suggest that at least some specimens are the products of hybridization. In North America, the name Festuca prolifera has been applied to vegetatively proliferating specimens of F. richardsonii, F. rubra s.l,, and some specimens that may be hybrids. Although proliferating spikelets are conspicuous, they do not justify taxonomic rank.
The occurrence of an extended bundle sheath system (paraveinal mesophyll) in the legumes
Authors: Kevekordes K. G. , McCully M. E. , Canny M. J.
Published: April 2011

The tissue previously described as paraveinal mesophyll in soybean leaves is shown to have the characters of bundle sheath rather than mesophyll cells and is renamed "extended bundle sheath" (EBS) tissue. Its presence was surveyed by leaf clearing in 66 species of legumes of all three subfamilies. A complete extended bundle sheath system similar to that previously described in soybean was identified in 21 of the species. This system is a paradermally oriented tissue, one cell deep, between the spongy and palisade mesophylls, consisting of extended bundle sheath cells, which join each other across the interveinal space either directly or via bridging cells of somewhat similar shape and size. A newly recognized, attenuated extended bundle sheath system, in which bundle sheath cells extend but do not form a continuum except in very narrow interveinal spaces, is described; it was found in 32 species. Extended bundle sheath tissue was absent from 13 of the species. The presence or form of extended bundle sheath tissue does not follow traditional taxonomic divisions. Extended bundle sheath systems were also found in 3 of 5 nonlegume species.
The effects of nickel and copper on the axenic growth of ectomycorrhizal fungi
Authors: Jones Melanie D. , Hutchinson Thomas C.
Published: April 2011

Isolates of several ectomycorrhizal fungi, some from a Cu- and Ni-contaminated smelter site near Sudbury, Ont., and some from an uncontaminated site, were grown on solid media containing 25 or 100 mg nickel/L, or 25 or 100 mg copper/L. The influence of the metals on lag time prior to the commencement of growth, on the maximum increase in colony diameter, and on the final colony dry weight was determined. Isolates from the metal-contaminated site did not outperform those from the uncontaminated site on any of the metal-amended media. In a second experiment, isolates of Laccaria proximo, Lactarius hibbardae, Lactarius rufus, and Scleroderma flavidum were grown in liquid media containing 2 or 5 mg Ni/L or 4 mg Cu/L. These fungi have previously been shown to vary in their effect on the metal tolerance of Betula papyrifera, at these concentrations. The axenic growth of the fungi in the presence of Ni showed no relationship to their effect on the birch seedlings. In general, the fungi that were least tolerant to Cu in liquid culture, Lactarius rufus and Laccaria proximo, were the same ones that proved most detrimental to the birch grown in the presence of Cu. These results indicate that axenic screening tests will not necessarily select fungi that will increase host metal tolerance.
Inheritance and transmission of plastid alterations in a green–white stripe mutant of pearl millet (Pennisetum americanum)
Authors: Reddy M. K. , Subrahmanyam N. C.
Published: April 2011

The breeding behaviour of the GWS-14 stripe mutant of pearl millet was tested in crosses with different normal inbred lines. The F2 segregations revealed two independently assorting recessive nuclear genes controlling the stripe phenotype with variable expressivity. Striping appeared 25 days after germination or later, suggesting the delayed expression of mutant genes. When stripe plants were crossed with pollen from normal inbreds, normal and white F1 progeny were obtained, while reciprocal crosses gave exclusively normal F1 progeny, suggesting that the white plastids are maternally transmitted in the absence of homozygous recessive nuclear genes in homoplastidic (altered plastids) egg cells. The absence of stripe progeny indicates the possible reversion of such plastids in heteroplastidic egg cells.
Effect of penicillin and of streptomycin sulphate on infection of sunflower seedlings by Plasmopara halstedii
Authors: Sackston W. E. , Vimard Brigitte , Gray A. Bruce
Published: April 2011

Streptomycin sulphate prevented infection of sunflower seedlings by three races of the downy mildew pathogen Plasmopara halstedii (Farl.) Berlese et de Toni. It inhibited emergence of zoospores from zoosporangia and at high concentrations (500 ppm) was phytotoxic. Affected seedlings were stunted and chlorotic. Penicillin had no observable effect on infection or on appearance of the seedlings.
A taxonomic study of the annual Hordeum depressum and related species
Authors: Baum Bernard R. , Bailey L. Grant
Published: April 2011

To clarify the limits between H. depressum (Scribner & Smith) Rydberg and its close and remote allies, H. intercedens and H. pusillum, respectively, we carried out morphological and cytological examinations and various statistical analyses including classifactory discriminant analysis, canonical discriminant analysis, and logistic discrimination. We concluded that H. depressum, a tetraploid species, can usually be morphologically separated from H. intercedens, a diploid species with which it is most frequently confused, by the maximum width of the lateral lower glumes. Those of H. depressum are 0.1–0.5 mm wide, whereas those of H. intercedens are 0.4–1.3 mm wide. Very few specimens will fall in the area of overlap between the two species. In these cases morphological identification can be ascertained by the lodicules, which in H. depressum have an obvious and glabrous side lobe, whereas if there is a lobe in H. intercedens, it is rather small and beset with hairs at the margins. Populations of H. depressum are often large and occur in the intermontane region of northern and central California, whereas those of H. intercedens are typically small and occur along the coast of south California and Baja California. These two species are sympatric to a small degree, whereas H. pusillum does not occur in south and Baja California but is found throughout the United States and a few adjacent places in Canada. Other morphological and statistical findings are discussed.
Erigeron salishii, a new Erigeron (Asteraceae) from British Columbia and Washington
Authors: Douglas George W. , Packer John G.
Published: April 2011

Erigeron salishii G. W. Douglas & J. G. Packer, n.sp., a morphologically distinctive species from southwestern British Columbia and northwestern Washington, is described, illustrated, and compared with E. compositus var. discoideus.
Development of helicoidal texture in the prerelease mucilage of quince (Cydonia oblonga) seed epidermis
Authors: Abeysekera R. M. , Willison J. H. M.
Published: April 2011

Quince (Cydonia oblonga Mill.) seed epidermis was examined cytologically during its development. Three developmental phases were delimited: immaturity, transition to maturity, and maturity. These cytological phases corresponded with phases of competence to release hydrated mucilage on wetting, immature tissue being completely incompetent and mature tissue fully competent. Growing cells of immature tissue were vacuolate and thin walled. By contrast, protoplasts of nongrowing mature epidermal cells had contracted to a remnant and been replaced by periplasmic deposits. Within these deposits, surrounded by amorphous material, were massive arrays of widely spaced microfibrils arranged helicoidally. In the oldest sample examined, periplasmic material appeared to be spewing through the broken outer walls of some cells. The periplasmic material is interpreted to be prerelease mucilage, which progressively fills the periplasm during a brief transitional phase. It seems that amorphous periplasmic material is deposited initially and microfibrils later intermingle with it. At some stage during filling of the periplasm, the microfibrils begin to organize, ultimately becoming helicoidal. Orderliness seems to begin in the central region of the periplasmic pool, not at its edges. It is proposed that nucleation of liquid crystalline helicoidal arrays occurs in the periplasm and that these arrays remain fluid until their disintegration during release as a result of hydration.
The effects of sodium fluoride on cytoplasmic leakage and the lipid and fatty acid composition of jack pine (Pinus banksiana) seedlings
Authors: Zwiazek J. J. , Shay Jennifer M.
Published: April 2011

The effects of sodium fluoride on the lipid and fatty acid composition of jack pine (Pinus banksiana Lamb.) seedlings were studied using chromatography techniques. Sodium fluoride markedly reduced levels of phospholipids and increased those of nonpolar lipids. Fatty acid composition was little affected. In several fluoride treatments, elevated levels of palmitic and stearic acid were found, while those of behenic acid declined. The changes in lipid and fatty acid composition were accompanied by increased solute leakage from cells. Cellular membranes are implicated as possible sites of fluoride injury.
Effects of a water-depth gradient on the germination of lakeshore plants
Authors: Moore Dwayne R. J. , Keddy Paul A.
Published: April 2011

The germination requirements of many wetland species commonly found in the seed bank are poorly understood. The purpose of this study is to explore the germination responses of lakeshore plant species to a water-depth gradient on each of two soil types normally found on shorelines and to test whether germination patterns predict field distributions of adults. Germination patterns were determined in a greenhouse by sowing seeds of 24 lakeshore species along an artificial water-depth gradient, using two soil types (sand and organic soil). Those species showing significant treatment effects were then tested for similar or different germination patterns, using Kendall's coefficient of concordance. Species had similar germination patterns (n = 5, P = 0.02) on sand. Species had different germination patterns (n = 7, P > 0.50) on the organic soil. Mean water-depth of germination was significantly correlated with the mean depth occupied by adults in the field for seven species (r = 0.81, P = 0.04). This study shows that germination requirements are important in controlling recruitment of wetland species after disturbance.
Intraspecific genetic variability of isozymes in the ectomycorrhizal fungus Suillus tomentosus
Authors: Zhu Hong , Higginbotham Kenneth O. , Dancik Bruce P. , Navratil Stan
Published: April 2011

Mycelial extracts of 43 isolates of Suillus tomentosus (Kauffm.) Singer, Snell & Dick collected from four boreal forest regions in Alberta were subjected to starch gel electrophoresis. A total of 21 bands was resolved from eight different enzyme systems presumably representing 13 loci. Six loci were polymorphic among these isolates. Cluster and principal components analyses demonstrated that intraspecific genetic variability of this fungus existed among and within forest regions. Polymorphic loci of acid phosphatase and alkaline phosphatase exhibited the greatest genetic similarity among the isolates within forest regions. Habitat isolation and host selection could be the major sources of genetic variation among forest regions.
Structure and properties of sperm cells isolated from the pollen of Zea mays
Authors: Cass David D. , Fabi George C.
Published: April 2011

Sperm cells can be isolated from maize pollen grains by gentle osmotic treatment. After the initial osmotic burst, the slurry is sieved through nylon mesh and then subjected to sucrose density gradient centrifugation to remove as much starch as possible. The isolated cells are spherical and approximately 7.2 μm in diameter, exclude Evans blue stain up to several hours at room temperature, and can be frozen and stored with reasonable retention of viability. Little alteration of the appearance of the living cells is seen after preparation for transmission electron microscopy. There is ultrastructural confirmation that maize sperm cells are protoplasts. Furthermore, there is no evidence of vegetative cell inner membrane on the outside of the sperms. Internally, there is a normal organelle complement including mitochondria, dictyosomes, protein bodies, and endoplasmic reticulum. The latter component is extensive and has associated ribosomes. Some coated vesicles occur in maize sperm protoplasts. Nuclear morphology is quite variable, including spherical, lobed, and irregular shapes.
Silica deposition in the inflorescence bracts of wheat (Triticum aestivum). I. Scanning electron microscopy and light microscopy
Authors: Hodson M. J. , Sangster A. G.
Published: April 2011

Silica deposition in the lower glume, lemma, and palea of wheat (Triticum aestivum L. cv. Highbury) was investigated using scanning electron microscopy and light microscopy. Silica was present in the outer walls of all the epidermal cells including prickles and papillae of the glume and lemma awns. The glume and the lemma were similar in epidermal silica deposition pattern, both having numerous silicified short trichomes and papillae on inner and outer surfaces. Epidermal long cells and short cells were also silicified. Macrohairs were restricted to isolated areas in these bracts, particularly on the inner surfaces just beneath the awns. The palea was a thin membranous structure differing markedly from the other two bracts. Most of the palea is pressed between the caryopsis and the next floret, and both surfaces are almost devoid of trichomes in these areas. However, at the apex and margins of the palea, macrohairs and papillae were abundant. The results are discussed with respect to possible taxonomic, anatomical, medical, and archaeological implications.
Les lichens sur serpentine et amphibolite du plateau du mont Albert, Gaspésie, Québec
Authors: Sirois Luc , Lutzoni François , Grandtner Miroslav M.
Published: April 2011

At Mount Albert, Quebec, many taxa are found exclusively on either serpentine or amphibolite contiguous formations. This exclusivity is clearly more noticeable within the saxicolous lichens than within the other groups. Serpentine seems to be an unfavourable substratum for the growth of saxicolous lichens. There are more infrequent taxa on serpentine than on amphibolite. The saxicolous, muscicolous, and terricolous lichen flora and the lichenicolous fungi of the plateau include 202 taxa, most of which have an arctic affinity. Of these taxa, 36 are recorded for the first time in Quebec, 16 in Canada and, 11 in North America. The ecological influence of serpentine on the lichens is, in many aspects, similar to that observed on vascular plants.
New species of Stephanoascus with Sporothrix anamorphs
Authors: Traquair J. A. , Shaw L. A. , Jarvis W. R.
Published: April 2011

Two new folicolous fungal epiphytes, Stephanoascus flocculosus and Stephanoascus rugulosus, with distinctive conidial anamorphs, Sporothrix flocculosa and Sporothrix rugulosa, respectively, are described and illustrated. Both Stephanoascus species have two-celled asci and galeate ascospores. These two species are distinguished from previously described Stephanoascus species by asci with long, cylindrical appendages. Their anamorphs can be distinguished by colony morphology and conidial characteristics. Sporothrix flocculosa produces powdery to somewhat tufted to plumose colonies on malt–yeast extract agar, while colonies of S. rugulosa are yeast-like and wrinkled. Sporothrix flocculosa produces subglobose to obovoid, rough-walled secondary conidia, while S. rugulosa produces ellipsoidal to narrowly obovoid secondary conidia that are smooth or rarely slightly warted. The conidiogenous cell of S. flocculosa is produced directly on the vegetative hypha; the conidiogenous cell of S. rugulosa is produced on a conical hyphal projection.
Apoplastic and ultrastructural characterizations of the trichomes from the carnivorous bromeliad Brocchinia reducta
Authors: Owen Jr. T. Page , Benzing David H. , Thomson William W.
Published: April 2011

The ultrastructure of the trichomes from the carnivorous bromeliad Brocchinia reducta was studied. The foliar trichome occurred in a cutinized epidermal crypt and was differentiated into cap, stalk, and foot cells. Unlike members of other bromeliad genera, the approximately 30 cells in the cap were alive at maturity and possessed an unusual labyrinthine-like wall organization. Irregularly shaped, dense wall regions that were separated by electron-transparent interstices extended from a thin, primary wall. This system appeared to constitute an elaborate system of channels specialized for nutrient uptake, a role which is consistent with the observed localization of the apoplastic tracer lanthanum. Moreover, cuticular gaps were noted where the cap cells face the tank cavity. These openings were the only site of solute entry into the gland. Cap cells possessed much plasmalemma blebbing and contained numerous coated vesicles and coated plasmalemma regions, all suggesting specializations for absorption and possibly secretion. Experiments using lanthanum as a tracer indicated that an apoplastic continuum exists from the cap cells to the underlying mesophyll, and that this system might provide a diffusive pathway for nutrient uptake.
An inhibitor of aflatoxin biosynthesis in developing cottonseed
Authors: McCormick Susan P. , Bhatnagar Deepak , Goynes Wilton R. , Lee Louise S.
Published: April 2011

A factor present in the coats of young developing cottonseed (20–25 days old) but absent from older developing seeds (35–40 days old) significantly inhibited (> 85%) aflatoxin formation by Aspergillus flavus without affecting fungal growth. Inhibition was independent of levels of seed moisture, phenolics, or tannins. The inhibitory factor was nondialyzable (molecular mass > 8 kDa); the inhibition of aflatoxin accumulation was dependent on its concentration. The inhibitor was probably an anionic protein since it bound to an anion exchanger and was eluted at 0.15 M salt. The inhibitor did not exhibit a peroxidase-like activity, even though it was observed that the factor was stable at temperatures below 70 °C and that sugar moieties were associated with the inhibitory property. The inhibitory activity was not similar to that of a serine protease.
Mineral storage in Cucurbita embryos. II. Calcium storage in reciprocal hybrids of Cucurbita maxima and Cucurbita andreana
Authors: Ockenden I. , Lott J. N. A.
Published: April 2011

Hybrid seeds from crosses between Curcurbita maxima and Curcurbita andreana were similar in weight to the seeds of the maternal parents. The calcium concentrations of the hybrid embryos were significantly different from the Ca concentrations of both parent species and tended toward a level intermediate between that of the two parents. However, the hybrids also differed in Ca concentration from each other and each was more similar to its female parent, indicting some maternal influences on Ca accumulation. There was a significant negative correlation between both embryo weight and embryo length and Ca concentration in hybrid embryos of the large seeds of Cucurbita maxima × Cucurbita andreana. The small seeds of Cucurbita andreana × Cucurbita maxima had embryos in which embryo weight was positively correlated with Ca concentration. In both parent and hybrid embryos the Ca concentration of the axis was higher than the concentration in the cotyledons. The axes of all four kinds of embryos had similar Ca concentrations so that the differences found for whole embryos were due to changes in Ca concentrations in the cotyledons.
Some aspects of nitrogen, phosphorus, and potassium nutrition of three colonizing beach species
Authors: Hawke Mary Ann , Maun M. A.
Published: April 2011

The culture of three colonizing dune species in hydroponics indicated that nitrogen (N), phosphorus (P), and potassium (K) were essential for high plant productivity. The K requirement of Oenothera biennis was lower than that of Cakile edentula or Corispermum hyssopifolium. The dry weight per plant of O. biennis was greater at higher concentrations of N, P, or K; however, the dry weight per plant of Cor. hyssopifolium was similar at all concentrations except in the complete absence of N, P, or K. Cakile edentula did not grow well under any of the nutrient concentrations, probably because of a poor response to hydroponic solutions. The number of live leaves and leaf area of O. biennis and Cor. hyssopifolium were affected more by a lack of N and P than K. The nutrient requirements of Cakile edentula were substantially higher than those of either O. biennis or Cor. hyssopifolium. It is suggested that the hierarchy in plant size and seed production in field populations may result from variability of available nutrients. Oenothera biennis, a generalist weedy species of farmland, old fields, waste places, and sandy beaches, was less exacting in its requirements of N, P, and K than the two beach specialists, Cakile edentula and Cor. hyssopifolium.
A critical examination of the soil washing technique with special reference to the effect of the size of the soil particles
Authors: Bååth Erland
Published: April 2011

The fungal species composition found by using the soil washing technique was affected by the number of species that were isolated from each particle. The particular species that were present were also of importance. Usually, slow-growing fungi were less often isolated if many other species or if heavily sporulating isolates were present. Faster growing species were also affected. Thus, Mortierella pulchella was seldom isolated from a soil particle with another Mortierella species. The use of small particles, where more than one isolate was seldom found, favoured the isolation of slow-growing fungi. The use of small particles with the soil washing technique thus appeared to give a more realistic picture of the fungal community.
Lipid synthesis by isolated duckweed (Lemna minor) chloroplasts in the presence of a sublethal concentration of atrazine
Authors: Grenier Gilles , Proteau Luce , Beaumont Gaston
Published: April 2011

We have examined the effects of a sublethal concentration of atrazine on the incorporation of sodium-[U-14C] acetate into isolated chloroplast lipids of Lemna minor. A high level of [14C]-acetate was incorporated into diacylgalactosylglycerol (DGG) and diacylglycerol (DAG). Consequently, the conversion of phosphatide acid to DAG and that of DAG to DGG seems to be as active in L. minor (an "18:3-plant") as in "16:3-plants." Chloroplast lipids from atrazine-treated plants were more extensively labelled with [14C]-acetate than the control plants. These results are in agreement with our previous in vivo studies which suggest that sublethal concentrations of atrazine stimulate the lipid metabolism of L. minor to form more thylakoid membranes. Furthermore, the specific radioactivity of linolenic acid was the highest in DAG and the lowest in DGG. These data suggest that desaturation of linoleic acid to linolenic acid mainly occurs before the galactosylation of DAG to form DGG in L. minor.
Characteristics of naturalized populations of white clover (Trifolium repens) in Atlantic Canada
Authors: Fraser Joanna
Published: April 2011

Some characteristics of seven populations of naturalized white clover (Trifolium repens L.) from native pastures in Nova Scotia, Prince Edward Island, and New Brunswick were investigated. Nine vegetative characters were measured on 16- to 18-week-old plants, and within and between population differences determined for cyanogenesis. Variation was observed between and within populations for all measured characteristics. Leaf marks were predominately the central V-shaped chevron; one population had plants without the chevron. Relative leaf size (length × width) ranged from 145 to 784 mm2. Hydrogen cyanide concentrations in leaf laminae were lower in cyanogenic (AcLi) and glucosidic (Acli) genotypes than enzymatic (acLi) genotypes. HCN concentrations in genotypes varied between and within populations. A population from Charlottetown, Prince Edward Island, had several desirable agronomic features, e.g., larger leaves, longer petioles, and thicker stolons than other populations, and could be used in a breeding programme for improved winter-hardy white clover varieties suited for rotational grazing and silage in Atlantic Canada.
Characterization of inhibition of Rhizopus stolonifer germination and growth by Enterobacter cloacae
Authors: Wisniewski Michael , Wilson Charles , Hershberger Wilbur
Published: April 2011

Interactions between Enterobacter cloacae and Rhizopus stolonifer were evaluated to determine possible mechanisms by which E. cloacae protects peach fruit from postharvest rot caused by R. stolonifer. Inhibition of Rhizopus sporangiospore germination by E. cloacae was dependent on the concentration of the antagonist. Antagonist concentration (1 × 1010 cfu ∙ mL−1) needed to completely inhibit germination was similar to that needed to prevent fruit infection. Significant inhibition of in vitro hyphal growth was achieved at 1 × 105 cfu ∙ mL−1 with simultaneous culturing of the fungus and antagonist. A reduction in inhibition occurred when addition of the antagonist was delayed. The presence of glucose in the growth medium did not prevent attachment of E. cloacae to hyphae and sporangiospores of R. stolonifer. Agglutination assays of sporangiospores by E. cloacae were positive whereas agglutination of cell-wall fragments was less distinct. Data indicate that nutrient competition, perhaps facilitated by bacterial attachment, may play a key role in E. cloacae and R. stolonifer interactions.
Litterbags, leaf tags, and decay of nonabscised intertidal leaves
Authors: Newell S. Y. , Fallon R. D.
Published: April 2011

Like most plants with perennial rhizomes and annual shoots, Spartina alterniflora does not abscise its leaves. This brings into question the appropriateness of commonly used litterbag methods for study of natural decomposition of S. alterniflora shoots. We compared decay phenomena for S. alterniflora leaves that were either (i) tagged and left in the natural standing position or (ii) cut and placed in litterbags on the marsh sediment at the same site. Rates of loss of mass and leaf area were similar between standing and cut leaves, but distinct differences were detected between leaf types for the carbon to nitrogen ratio and measures of microbial mass and activity. For example, bacterial standing crop was 4 to 67 times greater for cut leaves (though bacterial cells were 9 to 22 times less active (3H-thymidine incorporation/cell)), and fungal living standing crop (ergosterol content) was 5 to 9 times greater for standing leaves. In areas such as southern temperate zones, where shoots are not pushed onto the sediment by ice and snow, it is better to avoid altering the natural positioning of leaves that are not abscised in studies of shoot decay because (i) standing-dead shoots can harbour active microbial assemblages and (ii) shunting directly to the sediment phase can yield an artificial image of microbial–chemical dynamics.
Morphological and anatomical development in the Vitaceae. V. Vegetative and floral development in Ampelopsis brevipedunculata
Authors: Gerrath Jean M. , Posluszny Usher
Published: April 2011

The vegetative and floral development of Ampelopsis brevipedunculata was studied using both three-dimensional and histological techniques. An uncommitted primordium (which usually develops into a tendril in young seedlings and a cymose inflorescence in mature plants) is initiated opposite every leaf on the flank of the shoot apical meristem. Flowers are hermaphroditic, pentamerous, and protandrous. The sepals are initiated spirally, and form a calyx unit as the result of subsequent activity of a basal ring primordium. The common petal–stamen primordia are initiated simultaneously, but differentiate into petals and stamens unidirectionally. The gynoecium is initiated as a ring primordium, which produces two septa from the inner gynoecium wall. Two bitegmic, anatropus ovules arise from the base of each septum. At maturity the gynoecium is superior and two-loculed. Pollen is tricolporate. A nectar-secreting disc arises from the base of the ovary. The fruit is a turquoise-blue berry, containing one to four seeds. Axillary buds, present at each node, develop sylleptically and normally abscise at the end of the growing season. A vertical series of as many as six serial axillary buds develop basipetally to form the overwintering buds, which are not externally visible.
Population density and height distribution of Corylus cornuta in undisturbed forests of Minnesota: 1965–1984
Authors: Kurmis Vilis , Sucoff Edward
Published: April 2011

This study examined hazel populations (chiefly Corylus cornuta Marsh.) over a 19-year period on 232 permanent plots in 29 mature undisturbed stands in five forest types in northern Minnesota. The density, frequency, and height of hazel were greater in the jack pine – red pine, red pine, and aspen–birch types than in the maple–basswood and fir–spruce types. In the red pine and aspen–birch types, hazel density decreased about 30% from 1965 to 1975 and then increased between 30 and 18% from 1975 to 1984. These shifts in density were unrelated to changes in the density of the overstory or of other shrubs. In the maple–basswood type hazel density declined 61% from 1965 to 1984; shade tolerant overstory simultaneously increased. Height distribution generally followed a pattern in which density decreased with height and probably with age. This distribution indicates that hazel stands are maintained by continual recruitment of new stems.
Pathogenicity and vegetative compatibility among isolates of Fusarium oxysporum and F. moniliforme colonizing asparagus tissues
Authors: LaMondia J. A. , Elmer W. H.
Published: April 2011

Isolates of Fusarium moniliforme (Sheld.) emend. Snyd. & Hans., F. oxysporum (Schlecht) emend. Snyd. & Hans., and F. solani (Mart.) Appel & Wollenw. emend. Snyd. & Hans. were recovered from three 5-year-old field grown asparagus (Asparagus officinalis L. cv. Mary Washington) by isolating from symptomatic and asymptomatic feeder roots, storage roots, crown and basal stem segments. Fusarium moniliforme was more virulent than F. oxysporum on asparagus seedlings and F. solani was considered nonpathogenic. Isolates of F. moniliforme and F. oxysporum were placed into vegetative compatibility groups (VCGs) by demonstrating heterokaryosis with complementation tests using nitrate-nonutilizing (nit) mutants (pairing nitM and nit1 mutants). Ninety-seven of 135 isolates of F. moniliforme were placed in 13 vegetative compatibility groups. The remaining 38 isolates were not classified by vegetative compatibility because of poor nit mutant recovery. Eight of 18 isolates of F. oxysporum were unique and classed as single members of eight different VCGs. The other 10 isolates were not placed in VCGs. All isolates of F. moniliforme were virulent, but mean disease ratings differed among the isolates in different VCGs. There was no correlation between vegetative compatibility group and tissue substrate or symptom expression on the tissue substrate. It appears that virulence on asparagus is a common trait with few exceptions among genetically distinct populations of F. moniliforme and F. oxysporum colonizing asparagus.
Development of the crown (nodal diaphragm) in coastal Douglas-fir seedlings
Authors: Krasowski M. J. , Owens J. N.
Published: April 2011

Crown development of coastal Douglas-fir seedlings was studied in 2 consecutive years, compared between seedling lots from low and high elevation grown under containerized-nursery conditions, and related to bud development. Differentiation of the crown began after bud-scale initiation had been completed in seedlings from both elevations. Bud development in high elevation seedlings preceded that of low elevation seedlings by about 2 weeks. The thickening of the cell walls was not strictly related to the completion of embryonic shoot formation, particularly in seedlings from the low elevation source. Intercellular spaces between crown cells were filled with pectic substances during the dormant period. Dictyosomes, ER, plasma membrane, and possibly the nuclear envelope appeared to be involved in formation of cell walls in the crown. Vacuolar and cytoplasmic tannins were abundant in cells of the differentiating crown; the former apparently served as a reservoir of carbohydrates utilized during crown development. ER appeared to be involved in vacuole formation and autophagic processes. Cells of the mature crown were highly vacuolated and during dormancy, the cytoplasm was very dense. Development and morphology of the crown are discussed in relation to its possible function.