bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies on the growth and development of the rhizome and lateral rhizome buds in Elytrigia repens: some effects of parent shoot excision
Authors: McIntyre G I , Cessna A J
Published: April 2011

In experiments conducted under controlled conditions, excision of the shoot of Elytrigia repens (L.) Nevski increased the rate of rhizome elongation and promoted the growth of the lateral rhizome buds. Measurements with a transducer showed that the long-term growth response of the rhizome to shoot excision (4-6 days) was preceded by an immediate but transient (10 min) increase in growth rate. These various responses were associated with the occurrence of guttation from the rhizome apex, increases in the water content of the rhizome apex and lateral buds, and a 62% increase in rhizome water (pressure) potential. Parent shoot excision also induced a transition from rhizome to shoot development at the rhizome apex and caused lateral buds to develop as shoots instead of rhizomes when released from apical dominance. These developmental responses were associated with reductions in the dry weight of the rhizome apex and lateral buds and increases in the total N, amino-N, and nitrate content of the rhizome apex when expressed on a dry weight basis. These results provide evidence that, in E. repens, competition for water by the parent shoot may limit rhizome growth and contribute to the correlative inhibition of the lateral buds. They are also consistent with previous evidence that the C:N ratio may be an important morphogenetic factor in the mechanism controlling the path of bud and rhizome development.Key words: Elytrigia repens, water, nitrogen, rhizome, apical dominance.
What are hemoglobins doing in plants?
Authors: Hill Robert D
Published: April 2011

Within the last 3-4 years, evidence has accumulated to indicate that hemoglobin proteins exist widely in the plant community. This review presents some of the evidence to support this view and describes some of the properties of a barley hemoglobin. Barley hemoglobin has a strong avidity for oxygen, having an oxygen dissociation constant for oxyhemoglobin of 3 nmol L-1. It is induced under low oxygen tensions, with the induction regulated by ATP, or some consequence of ATP action. Experiments with transformed maize cells indicate that hemoglobin acts to improve the energy status of plant cells under low oxygen stress. It is postulated that hemoglobin acts as an oxygenase in plants. The review is a consequence of a CSPP Gold Medal Presentation at the Plant Biology 1997 Meeting in Vancouver, B.C.Key words: nonsymbiotic hemoglobins, hypoxia, barley, flooding tolerance.
Effect of harvesting method on seed bank dynamics in a boreal mixedwood forest in northwestern Ontario
Authors: Qi Meiqin , Scarratt John B
Published: April 2011

The effects of harvesting on seed bank dynamics in a boreal mixedwood forest were studied on replicated 10-ha treatment blocks harvested by different clear-cutting or partial-cutting systems in the fall of 1993. From 1994 to 1995 we monitored seed rain, soil seed banks, and seasonal changes in species composition in understory vegetation and seed banks in all harvest blocks plus three uncut controls. No persistent conifers were found in the soil seed banks of any treatment. The number of seeds of other species generally decreased with soil depth in all treatments, with the lower layer of organic soil yielding the highest numbers of seedlings. Many seeds of sedges and some herbs were found in the upper mineral soil horizon, indicating significant longevity. While disturbance by harvesting operations altered the distribution of seeds in the soil profile, harvesting method had little effect on the total number of species present in post-harvest seed banks or understory vegetation. There were no differences in seasonal compositional changes between treatments. Seed rain monitoring indicated that few conifer seeds were added to the seed bank. Betula papyrifera Marsh. was the dominant tree species in seed rain in the partial cutting treatments. However, in the second post-harvest year on clear cut sites sedges and grasses increased from less than 1 to 14% of seed rain. The results suggest that predominantly hardwood stands with prolific understory vegetation will initially develop on the treated sites, with a variable, but depleted conifer content.Key words: boreal mixedwood forest, natural regeneration, seed rain, seed bank, succession, vegetative propagation.
Bioenergetics of membrane transport in Synechococcus R-2 (Anacystis nidulans, S.leopoliensis) PCC7942
Authors: Ritchie Raymond J
Published: April 2011

Specialized chemical probe techniques need to be used to measure the membrane potential (delta psii,o) or the intracellular pH (pHi) of the cyanobacterium Synechococcus R-2 (PCC7942). The pHi of Synechococcus is essentially a set point (7.3) over a wide range of extracellular pH (pHo) from 7 to 11. Maintenance of the pHo is strongly Na+-dependent and the cells cannot tolerate acid pHo. The 86Rb+-valinomycin method of measuring the delta psii,o has inherent limitations, the most obvious being that the valinomycin treatment itself might alter the membrane potential. 201Tl+ has been found in Synechococcus to distribute across the plasmalemma passively, and so the accumulation ratio of the ion ([Tl+]i/[Tl+]o or Tl+i,o) can be used to calculate the apparent delta psii,o. The two types of probe give comparable results in Synechococcus. Polarizations of the delta psii,o of cells, because of electrogenic transport of ions, can be detected from its effects upon the uptake rate of permeant cations using both the 86Rb+-valinomycin and 201Tl+ methods. HCO3- hyperpolarized delta psii,o, whereas NH4+, CH3NH3+, and K+ led to depolarization. Most active transport systems, including the HCO3- pump, in cyanophytes appear to be ATP binding cassette (ABC) type ATP pumps. Few cotransport (H+ or Na+) driven mechanisms have been identified. A substantial proportion of the power available from photosynthesis and respiration is used to maintain ionic gradients and the membrane potential and in the light a large part (10%) is used to import inorganic carbon.Key words: cyanobacteria, membrane potential, intracellular pH, electrochemical gradient, bioenergetics.
Influence of the carbon concentrating mechanism on carbon stable isotope discrimination by the marine diatom Thalassiosira pseudonana
Authors: Fielding Anthony S , Turpin David H , Guy Robert D , Calvert Stephen E , Crawford David W , Harrison Paul J
Published: April 2011

There is no clear explanation why phytoplankton δ13C values are more negative in colder waters, but one current theory suggests that because colder waters hold more CO2, there is less diffusional limitation of CO2. This results in more discrimination against 13C and more negative phytoplankton δ13Cvalues. However, many species are able to actively take up CO2 or HCO3-, the latter being the major inorganic carbon species present in the dissolved inorganic carbon (DIC) pool of modern oceans. A previous study suggests that carbon concentrating mechanism (CCM) induction would affect carbon isotope discrimination, and this study confirms the presence of a relationship between discrimination and induction of a CCM in the marine diatom Thalassiosira pseudonana. CCM induction was measured by determining the half-saturation constant of photosynthesis (K0.5DIC). Values of K0.5DIC increased from 85 to 470 m M DIC over a range of ambient DIC levels from 0.2 to 2.7 mM. The fractionation factor increased from 10 to 21.3omicron over this same range. There was a significant relationship between K0.5DIC and the fractionation factor suggesting that CCM induction state influences carbon isotope discrimination. Other factors that influence discrimination may act through CCM induction.Key words: carbon isotope discrimination, carbon concentrating mechanism, Thalassiosira pseudonana, active carbon uptake, marine phytoplankton.
Changes in inorganic carbon uptake during the progression of a dinoflagellate bloom in a lake ecosystem
Authors: Berman-Frank Ilana , Erez Jonathan , Kaplan Aaron
Published: April 2011

The physiological, biochemical, and genetic aspects of inorganic (Ci) carbon uptake in aquatic plants and algae have been studied extensively. Yet, to date, few studies examined these questions on dominant phytoplankton populations in their natural environment. Lake Kinneret, Israel, provides a good example of a system in which changes in CO2availability play a vital role in the ecophysiology of inorganic carbon uptake and in the population dynamics during the annual bloom of the dinoflagellate Peridinium gatunense Nygaard. In this study we investigated whether the availability of CO2(aq)limited growth rates and primary productivity of in situ populations of P. gatunense and focused on the role of adaptive mechanisms for Ciuptake. At the onset of the bloom, when epilimnetic pH was low ( = 8) and Ciconcentrations were high ( = 2.5 mM), carbonic anhydrase activity and cellular affinity to CO2(aq)were comparatively low. At this time photosynthetic rates, quantum yields, and in situ growth rates were high. As P. gatunense biomass increased, inorganic carbon decreased by 40%, while CO2(aq)concentrations declined 50-fold to values less than 2 µM. The algae adapted by acquiring a CO2-concentrating mechanism indicated by (i) intracellular Ci-concentrations higher by a factor of 5-70 relative to the ambient Ci; (ii) levels of carbonic anhydrase activity higher by 5- to 50-fold than those at the beginning of the bloom; and (iii) enhanced affinity for Ciand CO2(aq)3- and 40-fold higher, respectively, than affinities at the start of the bloom. These mechanistic changes in carbon uptake were reflected in declining photosynthetic rates and quantum yields as well as in the carbon isotopic composition with lower fractionation (13C enrichment) of the algae as the bloom progressed. Finally, despite induction of adaptive uptake mechanisms to low CO2availability; scarcity of other nutrients combined with low CO2concentrations, increased temperatures, and increased turbulence cause a decline in in situ growth rates and the collapse of the dinoflagellate biomass.Key words: dinoflagellates, inorganic carbon uptake, CCM, carbonic anhydrase, Peridinium gatunense.
Chlamydomonas reinhardtiicDNAs upregulated in low-CO2conditions: expression and analyses
Authors: Somanchi Aravind , Handley Eric R , Moroney James V
Published: April 2011

Unicellular algae acquire the ability to raise their internal CO2concentrations under low-CO2conditions because of the presence of a CO2concentrating mechanism (CCM). In Chlamydomonas reinhardtii, this mechanism is induced when cells grown in high-CO2conditions are switched to low-CO2conditions. To elucidate the genes and proteins involved in this mechanism, we constructed a cDNA library from low CO2adapted cells and differentially screened the library for cDNAs upregulated under low-CO2conditions. Earlier studies identified six classes of clones specific to low CO2adapting cells. To identify other genes and proteins playing a role in this mechanism, we have systematically characterized the cDNA clones that appear to be upregulated by low-CO2adaptation but do not cross-hybridize with the six previously identified classes. We identified seven new classes of clones that are distinctly upregulated in low-CO2conditions. These clones were checked by Northern analyses, sequencing, and homology studies. One class of clone represents a novel gene, lci 3. We report on the seven classes of clones and the characterization of lci 3.Key words: Chlamydomonas, CO2concentrating mechanism, gene regulation, inducible genes, gene expression.
Cyanobacterial mutants impaired in bicarbonate uptake isolated with the aid of an inactivation library
Authors: Ronen-Tarazi Michal , Bonfil David J , Schatz Daniella , Kaplan Aaron
Published: April 2011

An inactivation library consisting of genomic fragments ligated within a modified bluescript vector was used to isolate several new high CO2requiring mutants of Synechococcus PCC7942. The mutants described here were impaired in the ability to accumulate Ciinternally when supplied with HCO3-. The relevant genomic regions bearing novel genes involved in the ability to transport and to accumulate Ciwithin the cells and thus to grow under low-CO2conditions are presented. Some of the mutants were also impaired in ability to adjust to an elevated pH in their medium. We show that the use of inactivation libraries enabled cloning of genes encoding membrane-located proteins; we point to mutations introduced by the single cross-recombination events resulting in the formation of some of these mutants. Possible artifacts that may result in incorrect identification of genes, the inactivation of which could have led to the observed phenotype, are discussed.Key words: bicarbonate uptake, cyanobacteria, CO2, mutants, photosynthesis, Synechococcus.
The inorganic carbon-concentrating mechanism in cyanobacteria: induction and ecological significance
Authors: Kaplan Aaron , Ronen-Tarazi Michal , Zer Hagit , Schwarz Rakefet , Tchernov Dan , Bonfil David J , Schatz Daniella , Vardi Assaf , Hassidim Miriam , Reinhold Leonora
Published: April 2011

In this minireview we focus on certain aspects of the induction, function, and ecophysiological significance of the inorganic carbon-concentrating mechanism in cyanobacteria. Since this entire issue is dedicated to various aspects of this mechanism, we mainly discuss some of the recent studies in our laboratory and point to open questions and perspectives.Key words: CO2, cyanobacteria, inorganic carbon-concentrating mechanism, photosynthesis.
Trichoderma koningii: neotypification and Hypocrea teleomorph
Authors: Lieckfeldt Elke , Samuels Gary J , Börner Thomas , Gams Walter
Published: April 2011

A neotype is selected for Trichoderma koningii. The species is characterized by morphological and molecular characters, the latter including polymerase chain reaction (PCR) fingerprinting and restriction fragment length polymorphism (RFLP) analysis and direct sequencing of the variable regions of the rDNA (internal transcribed spacer 1 (ITS-1) and internal transcribed spacer (ITS-2)). The neotype was selected from among four cultures obtained from soil at the type locality. These cultures were compared with a broader collection of Trichoderma strains and anamorphs of Hypocrea that morphologically conform to T. koningii. Comparison was also made with members of Trichoderma sect. Trichoderma and of the Hypocrea schweinitzii complex (Trichoderma sect. Longibrachiatum). According to its ITS sequences, T. koningii is a member of sect. Trichoderma, showing very low variability in comparison with Trichoderma viride and Trichoderma atroviride. We found five additional strains from various geographical regions that are identical to the neotype in morphology and in their sequences. One of them is Hypocrea koningii sp.nov., which we consider to be the teleomorph of T. koningii. PCR fingerprint patterns demonstrate the high genetic similarity of these nine strains. There was only low similarity in molecular characters between T. koningii and the H. schweinitzii complex despite morphological similarities.Key words: Hypocreales, Hypocrea muroiana, Hypocrea rufa, internal transcribed spacer, systematics.
Reassessment of Mycosphaerella spp. and their anamorphs occurring on Platanus
Authors: Crous Pedro W , Corlett Michael
Published: April 2011

Several species of Mycosphaerella, some of which have been linked to cercosporoid anamorphs, have been described from Platanus. A reassessment of these species revealed several synonymies and incorrect anamorph-teleomorph connections. Mycosphaerella albocrustata (Schwein.) Crous & Corlett is recognized as an earlier name for Mycosphaerella platanifolia (Cooke) F.A. Wolf, a species with no known anamorph. Mycosphaerella stigmina-platani F.A. Wolf is shown to be the teleomorph of a new anamorph species, Xenostigmina wolfii, which has a Cercostigmina synanamorph. The latter synanamorph was previously confused with Cercospora platanicola Ellis & Everh., which has recently been placed in Pseudocercospora. Xenostigmina wolfii is known only from the United States and is distinguished from Stigmina platani (Fuckel) Sacc. and Stigmina platani-racemosae Dearn. & Barthol. by its mode of conidiogenesis, longer conidia, and Cercostigmina synanamorph.Key words: Mycosphaerella, Platanus, Stigmina, systematics.
Flammulina (Agaricales): F. stratosa, a new New Zealand species distantly related to the cultivated Enoki mushroom
Authors: Redhead S A , Petersen R H , Methven A S
Published: April 2011

A new species, Flammulina stratosa Redhead, Petersen & Methven, sp.nov., is described from living Nothofagus from New Zealand. It is characterized by a thick, gelatinized mediopellis that virtually replaces all other pilear tramal tissues and is comparable with Flammulina similis. Cultures and mating systems are described.Key words: tetrapolar, conidia, southern hemisphere.
Three new hyphomycetes isolated from soil and feather debris
Authors: Udagawa Shun-ichi , Uchiyama Shigeru
Published: April 2011

Two hyphomycetous fungi isolated from soil in Japan and Nepal are described and assigned to a monotypic new genus, Conjunctospora, and to a new species of Oidiodendron. Conjunctospora vesiculifera is characterized by Aspergillus-like vesiculate conidiophores, a layer of ovoid conidiogenous cells, and brown meristem conidia. Oidiodendron hughesii is characterized by the development of the terminal part of conidiophores into a reticulate network of dark, thick-walled hyphae with appendage-like spines and a pale-coloured arthroconidial mass. This fungus is a psychrophile. Spirosphaera keratinophila, isolated from a fallen crow feather in Japan, is also described as a third new hyphomycete. This fungus is keratinolytic and characterized by hyaline to pale yellow clathroconidia.Key words: Hyphomycetes, systematics, Conjunctospora, Oidiodendron, Spirosphaera.
The genus Uncinocarpus (Onygenaceae) and its synonym Brunneospora: new concepts, combinations and connections to anamorphs in Chrysosporium, and further evidence of relationship with Coccidioides immitis
Authors: Sigler Lynne , Flis Arlene L , Carmichael J W
Published: April 2011

The genus Uncinocarpus (Onygenales, Onygenaceae) is emended to include keratinophilic fungi with discrete, globose gymnothecial ascomata without differentiated ascomatal hyphae and bearing uncinate, helical, or no appendages; oblate, punctate ascospores sometimes with irregular reticulations; bulbous initials, and Malbranchea or Chrysosporium anamorphs. The new combination Uncinocarpus orissi is proposed for Pseudoarachniotus orissi; Gymnoascus arxii is shown to be a synonym. New records show that the fungus has a wide distribution from North America, Europe, Asia, and the Middle East. The teleomorph is formed under laboratory conditions by mating representative isolates. The anamorph has been described under the names Chrysosporium zonatum and Chrysosporium gourii. Chrysosporium queenslandicum is morphologically similar. Its teleomorph Apinisia queenslandica is transferred also to the genus Uncinocarpus as Uncinocarpus queenslandicus. Brunneospora reticulata, the type species of the genus Brunneospora, is a synonym. Orromyces spiralis appears to be another name applied to this fungus. Development of helical coils in an isolate of Coccidioides immitis provides further evidence of a possible relationship between this dimorphic human pathogen and this group of ascomycetes.Key words: Uncinocarpus, Onygenales, systematics, keratinophiles, human pathogen.
Double-stranded RNA and associated virulence in South African isolates of Sphaeropsis sapinea
Authors: Steenkamp Emma T , Wingfield Brenda D , Swart Wijnand J , Wingfield Michael J
Published: April 2011

Sphaeropsis sapinea (Fr.) Dyko & Sutton is an opportunistic pathogen of various Pinus spp., causing severe shoot blight and dieback. Some isolates of S. sapinea display characteristics such as reduced virulence, reduced growth rate, lack of pigmentation, altered colony morphology, and suppressed conidiation. South African isolates of S. sapinea displaying a range of growth patterns, including reduced growth rate and atypical morphology, were screened for the presence of double-stranded RNA (dsRNA). They were also tested for relative virulence in pathogenicity tests. Double-stranded RNA was isolated by means of phenol extraction and cellulose chromatographic purification. A single species of dsRNA (± 4.3 kilobase pairs in size) was obtained from two slow-growing isolates and two isolates with more regular growth. The virulence of these dsRNA-containing isolates was tested on mature Pinus patula Schlecht. et Cham. trees. Although reduced virulence was positively correlated with slower growth in vitro, the presence of dsRNA could not be linked to either of these characteristics.Key words: double-stranded RNA, hypovirulence, Sphaeropsis sapinea.
Étude comparée de la reproduction de Phymatolithon calcareum (Pallas) Adey & McKibbin et Lithothamnion corallioides (P. & H. Crouan) P. & H. Crouan (Corallinales, Rhodophyta), et reconsidérations sur la définition des genres
Authors: Mendoza M L , Cabioch J
Published: April 2011

The two CorallinalesPhymatolithon calcareum and Lithothamnion corallioides are the main components of European maerl communities. A large majority of the thalli are free-living branches borne on juvenile crusts that are rarely found. A detailed investigation of these juvenile stages has allowed the discovery of their reproductive features. Sexual reproduction of P. calcareum, the type-species of the genus, is described here for the first time and thus gives fundamental data for the generic definition. On the floor of the female conceptacle, a set of carpogonial branches is formed. Each fertilized carpogonium then fuses with the supporting cell of the carpogonial branch, which is also its auxiliary cell. A small fusion cell is thus formed, which produces upwards a small gonimoblast reduced to a short chain of carposporangia. In a mature conceptacle, the surface of the fertile floor thus appears entirely covered with small gonimoblasts. In the male conceptacle, mature spermatangia produced on the floor are typically dendroid; those produced on the walls are of a more simple type. The organization of the asexual conceptacle is briefly reviewed. The reproduction of L. corallioides is also newly described and compared with that previously reported for L. muelleri, the type-species of the genus.Key words: Corallinales, Phymatolithon, Lithothamnion, sexual reproduction, generic definition.
Analysis of litter decomposition in an alpine tundra
Authors: Bryant David M , Holland Elisabeth A , Seastedt Timothy R , Walker Marilyn D
Published: April 2011

Decomposition of plant litter regulates nutrient cycling and transfers of fixed carbon to soil organic matter pools in terrestrial ecosystems. Climate, as well as factors of intrinsic litter chemistry, often govern the rate of decomposition and thus the dynamics of these processes. Initial concentrations of nitrogen and recalcitrant carbon compounds in plant litter are good predictors of litter decomposition rates in many systems. The effect of exogenous nitrogen availability on decay rates, however, is not well defined. Microclimate factors vary widely within alpine tundra sites, potentially affecting litter decay rates at the local scale. A controlled factorial experiment was performed to assess the influence of landscape position and exogenous nitrogen additions on decomposition of surface foliage and buried root litter in an alpine tundra in the Front Range of the Rocky Mountains in Colorado, U.S.A. Litter bags were placed in three communities representing a gradient of soil moisture and temperature. Ammonium nitrate was applied once every 30 days at a rate of 20 g N·m-2 during the 3-month growing season. Data, as part of the Long-Term Inter-site Decomposition Experiment Team project, were analyzed to ascertain the effects of intrinsic nitrogen and carbon fraction chemistry on litter decay in alpine systems. Soil moisture was found to be the primary controlling factor in surface litter mass loss. Root litter did not show significant mass loss following first growing season. Nitrogen additions had no effect on nitrogen retention, or decomposition, of surface or buried root litter compared with controls. The acid-insoluble carbon fraction was a good predictor of mass loss in surface litters, showing a strong negative correlation. Curiously, N concentration appeared to retard root decomposition, although degrees of freedom limit the confidence of this observation. Given the slow rate of decay and N loss from root litter, root biomass appears to be a long-term reservoir for C and N in the alpine tundra.Key words: litter decomposition, alpine tundra, nitrogen deposition, LIDET, Niwot Ridge.
Wound response characteristics as related to phenylpropanoid enzyme activity and lignin deposition in resistant and susceptible Populus tremuloides inoculated with Entoleuca mammata (Hypoxylon mammatum)
Authors: Bucciarelli B , Jung H G , Ostry M E , Anderson N A , Vance C P
Published: April 2011

Green internodal stem tissues of glasshouse grown Populus tremuloides were either wounded or wound-inoculated with Entoleuca mammata (Hypoxylon mammatum) and assayed for phenylalanine ammonia-lyase (PAL), caffeic acid - o-methyltransferase (CA-OMT), and cinnamyl - alcohol dehydrogenase (CAD) activity over a 96-h period. Lignin deposited in response to the treatments was analyzed by the Klason and the pyrolysis - gas chromatographic (GC) - mass spectroscopy (MS) methodologies. The wound-inoculated treatment resulted in a wound morphology congruent with a typical resistant and susceptible response to E. mammata. Wounding alone resulted in no morphological differences between the two genotypes. In wound-inoculated stem tissue PAL and CAD activities were substantially higher in the resistant relative to the susceptible genotype. Total Klason lignin was similar for both genotypes; however, pyrolysis-GC-MS analysis revealed a difference in the lignin monomeric composition between the two genotypes, with the susceptible genotype accumulating higher levels of hydroxyphenyl units relative to the resistant genotype. It is concluded that differences in PAL and CAD activity and the synthesis of distinct phenylpropanoid monomers distinguish the resistant from the susceptible aspen genotype. Alterations in boundary zone formation due to the differential synthesis of phenylpropanoid monomers and its effect on compartmentalization of the pathogen are discussed.Key words: aspen, Hypoxylon canker, phenylalanine ammonia-lyase, cinnamyl - alcohol dehydrogenase, caffeic acid - o-methyltransferase, disease resistance.
Phenetic distinction between the dwarf yellow water-lilies: Nuphar microphylla and N. pumila (Nymphaeaceae)
Authors: Padgett Donald J
Published: April 2011

Nuphar pumila (Timm) DC. and Nuphar microphylla (Pers.) Fern. are morphologically similar yellow water-lily species that are often regarded as conspecific or recognized as varieties of Nuphar lutea (L.) Sm. This phenetic study analyzes 18 features of vegetative, floral, and fruit morphology scored from North American populations of N. microphylla and Eurasian populations of N. pumila. Morphological similarities among specimens were assessed by univariate statistics, clustering by the unweighted pair group method using arithmetic averages (UPGMA), and ordination by principal components analyses. Means for 17 of the 18 quantitative variables differed significantly between operational taxonomic units (OTUs) of the two species, and an UPGMA phenogram provided good separation of OTUs. Principal components analysis also provided reasonable separation of OTUs, indicating leaf and fruit characters as strong distinguishing features. Multivariate analyses indicate two similar, yet distinct, morphological entities. When coupled with qualitative features, geographical barriers, and putative physiological barriers, morphometric data support the taxonomic recognition of two closely related species. Both species are most closely related to the Japanese endemic Nuphar japonica DC.Key words: Nuphar, Nymphaeaceae, water-lily, taxonomy, phenetics.
Changes in leaf structure in relation to crown position and tree size of Betula papyrifera within fire-origin stands of interior cedar-hemlock
Authors: Ashton P Mark S. , Olander Lydia P , Berlyn Graeme P , Thadani Rajesh , Cameron Ian R
Published: April 2011

Dimensions of anatomical and morphological attributes of leaves can influence physiological response to changes in environment over time. Linking structural attributes of leaves to crown position and tree size within naturally developing cohorts of trees can provide a clearer understanding of changes in crown morphology for a species. This study examined leaf anatomy and morphology of Betula papyrifera Marsh. growing in two stages of stand development of interior cedar-hemlock forest, northern British Columbia. Anatomical and morphological measurements of leaves located at six different positions within the crown were made on trees selected from stands that originated 15 years (small tree size) and 145 years (large tree size) after catastrophic fire. Leaf area and mass were measured in the field. Microscopic measures were made in the laboratory of thicknesses of leaves, cuticle, upper and lower epidermis, palisade, and spongy mesophyll. Stomatal density and stomatal aperture lengths were also determined. Leaf anatomy and morphology varied significantly with position in the crown and among size-classes of trees. Changes in leaf anatomy observed among positions within the crown reflect the changing availability of light and moisture experienced during crown development. For both size-classes of tree the largest anatomical dimensions of leaves were at the outer and uppermost parts of the crown, whilst the smallest were at the lower and innermost parts. Foliage of large trees (145 years) exhibit leaf attributes characteristic of the sun-shade dichotomy reported in the literature, but this was not shown for foliage of young saplings (15 years). For the small trees (15 years) the largest leaves were located at the top of the crown while the smallest were located at the bottom. This has been reported for many tropical pioneers but is in contrast to the usual sun-shade dichotomy of temperate pioneers. The large trees (145 years) followed the typical pattern with the smallest leaves at the top of the crown. Information from this study contributes to our understanding of foliar development of tree crowns by demonstrating how leaf structure changes with crown position and tree size under stand competition.Key words: Betula papyrifera, British Columbia, crown development, cuticle thickness, leaf area, palisade mesophyll, paper birch, stand dynamics.
The generalist pollination system and reproductive success of Calluna vulgaris in the Upper Ardenne
Authors: Mahy Grégory , Sloover Jacques De , Jacquemart Anne-Laure
Published: April 2011

Although specialist pollination systems are often thought to be the outcome of selection, wide evidence exists for generalization within plant-pollinator interactions. We studied the pollination system and reproductive success of Calluna vulgaris (L.) Hull over 3 years in an Upper Ardennes site in Belgium. A wide variety of insect visitors was recorded including Hymenoptera, Diptera, and Lepidoptera. Relative abundance of families and species of visitors varied markedly among years except for bees. Bumblebees and honeybees were the most efficient pollinators at the study site. Syrphid flies, mainly large ones, acted as important co-pollinators because of their high relative frequency. Calluna pollen was also dispersed by wind, and insect-exclusion experiments demonstrated that wind pollination contributed to reproductive success. Following open pollination, fruit set was high, ranging from 82.0 to 97.2% and independent of sampling location. Mean seed number per fruit was less than maximum potential seed number and varied strongly among sampling locations. We discuss this pollination system (generalist insect and wind) in terms of the ecological and geographical success of the species.Key words: Calluna vulgaris, pollinator visitation, insects, wind pollination, reproductive success.
Physiological and morphological responses to shade and nutrient additions of Claytonia virginica (Portulacaceae): implications for the "vernal dam" hypothesis
Authors: Anderson Wendy B , Eickmeier William G
Published: April 2011

Because of their unique phenology and physiology, spring ephemeral herbs are believed to play an important role in intrasystem nutrient cycling in deciduous forest ecosystems. It was hypothesized that they function as a "vernal dam" by temporarily sequestering nutrients and preventing leaching from the system during a period of high nutrient availability. However, spring ephemerals require high-irradiance growing conditions. How do their physiological and morphological responses to ambient light and shade limit their ability to sequester excess nutrients? We performed field experiments using Claytonia virginica L. as a model to test several responses to shade and increasing levels of nutrient additions. We also examined the biomass responses and nutrient storage capacities of other spring ephemeral herbs. In C. virginica, shading reduced ribulose 1,5-bisphosphate carboxylase-oxygenase (Rubisco) activity, photosynthesis rate, specific leaf weight, leaf width/length (W/L), and biomass; nutrient additions increased W/L and biomass only under unshaded conditions. Other herbs responded similarly but reached maximum biomass at lower nutrient addition levels than C. virginica. Shading reduced and nutrient additions increased nitrogen and phosphorus concentrations in both C. virginica and other herbs. Shaded herbs generally reached nutrient saturation at lower nutrient addition levels than unshaded herbs. Overall, unshaded plants sequestered larger amounts of nutrients than shaded plants. This pattern is best explained by a reduction in biomass under shaded conditions. We concluded that C. virginica and other spring herbs, although important components in forest nutrient cycling in the early spring, are limited in their capacity to store excess nutrients, particularly when shaded.Key words: Claytonia virginica, nutrient cycling, spring ephemerals, vernal dam.
Structures restricting passage of water in the mature seeds of yellow-cedar (Chamaecyparis nootkatensis)
Authors: Tillman-Sutela Eila , Kauppi Anneli
Published: April 2011

Anatomical structures of seed surface layers and their role in impeding passage of water were studied for mature yellow-cedar (Chamaecyparis nootkatensis D. Don) seeds. The structures of the seed coat, nucellar layers, and megagametophyte of both dry and moistened, sectioned seeds were examined with a field emission scanning electron microscope. The anatomical details of resin-embedded seeds were studied by light or fluorescence microscopy using stained and unstained sections. The permeability of the structures exterior to the megagametophyte was analyzed by placing seeds in a Methylene Blue solution and examining them under a stereomicroscope. Results proved that the seed coat proper had only a minor effect on restricting passage of water. Penetration of staining solution was efficiently directed by the wing and epicuticular wax layer covering it, and by the large, impermeable nucellar cap. These structures, typical for yellow-cedar, essentially differed from those studied in Picea and Pinus seeds. Still, the most effective barrier to the penetration of water was in the junction formed by the megaspore membranes and the strong cuticle of the megagametophyte. These structures together with the phenolic nucellar tissues probably contribute to physiological dormancy in yellow-cedar seeds. Consequently, studies of the localization of dormancy should be focused on these layers rather than on the seed coat.Key words: conifer, seed coat, anatomy, scanning electron microscopy, imbibition.
Variable patterns of seed maturation and abortion in Alliaria petiolata (Brassicaceae)
Authors: Susko David J , Lovett-Doust Lesley
Published: April 2011

We investigated variation in ovule development within and among fruits in garlic mustard, Alliaria petiolata (M. Bieb.) Cavara & Grande. Individuals were sampled at 14 sites in North America. On average, 94% of ovules showed evidence of fertilization and development. The majority of ovules (mean 68%; range 53.2-82.5%) reached seed maturity. Patterns of seed maturation and abortion varied nonrandomly within and among fruits. In sites in Tennessee, Kentucky, and Ontario, resource limitation seemed to be an important determinant of seed production, as fruits initiated nearest the base of an infructescence were significantly more likely to produce mature seeds than distally located fruits. Also the probability of seed maturation within individual fruits decreased significantly from the pedicellar to the stylar ends. In contrast, for individuals from Ohio sites, the probability of maturing seeds was greatest for centrally located fruits within an infructescence as well as for centrally located ovules within fruits, indicating a greater influence of pollen limitation in addition to resource limitation. We conclude that it could be misleading to infer traits of a species as a whole based on observed patterns of seed maturation in a single site or region. Rather such patterns may reflect prevailing conditions and selection pressures at a local, or regional, scale.Key words: Alliaria petiolata, Brassicaceae, garlic mustard, ovule abortion, seed maturation, patterns.
The Ceratocystis species on conifers
Authors: Harrington Thomas C , Wingfield Michael J
Published: April 2011

Seven Ceratocystis species are recognized as having conifers as their primary hosts, and these species comprise a monophyletic group. Despite being morphologically similar, these taxa are distinguished by intersterility and isozyme electromorphs. The first described species in the group, Ceratocystis coerulescens (Münch) Bakshi, is neotypified; it causes bluestain of Picea and Pinus in Europe and North America. A similar species, Ceratocystis pinicola sp.nov., also causes bluestain but has thus far been recorded only on Pinus in Britain. In contrast, Ceratocystis resinifera sp.nov. has been recorded from Picea on continental Europe and North America and invades wounds of living trees. Ceratocystis polonica (Siemaszko) C. Moreau is neotypified and distinguished ecologically from Ceratocystis laricicola Redfern & Minter; both species occur across Eurasia and are associated with Ips bark beetles on Picea and Larix, respectively. A key is presented for these species as well as the recently recognized species from North America, Ceratocystis rufipenni Wingfield, Harrington, & Solheim and Ceratocystis douglasii (Davidson) Wingfield & Harrington, which occur on Picea and Pseudotsuga, respectively.Key words: Ceratocystis, Pinaceae, bluestain, Scolytidae.
Reproductive biology of island and mainland populations of Primula mistassinica (Primulaceae) on Lake Huron shorelines
Authors: Larson Brendon MH , Barrett Spencer CH
Published: April 2011

To investigate the influence of insularity on plant reproductive biology at a local geographic scale, we examined aspects of reproduction in distylous Primula mistassinica Michx. (Primulaceae) on Lake Huron shorelines of the Bruce Peninsula and adjacent Tobermory Islands in Ontario, Canada. A total of 7 mainland and 13 nearshore island populations were compared. Controlled pollinations demonstrated that P. mistassinica possesses a dimorphic incompatibility system with intermorph crosses setting significantly more seeds than self or intramorph crosses. Floral morphology, population style-morph ratios, and seed fertility were compared in mainland and nearshore island populations to determine whether there was evidence for differences in reproductive traits between these areas. Style-morph ratios did not differ significantly from equilibrium expectations, and there were no consistent differences between island and mainland populations in floral morphology or fertility. Rather, the generalized pollination system of P. mistassinica and extensive historical opportunities for colonization appear to have mitigated insular effects so that proximate ecological factors are more relevant to the current reproductive biology of populations.Key words: distyly, insularity, pollination, reproductive biology.
Pathological anatomy of needles of Pinus strobus exposed to carbon-filtered air or to three times ambient ozone concentrations, or infected by Canavirgella banfieldii
Authors: Wenner N G , Merrill W
Published: April 2011

A necrosis of succulent, elongating, current-year needles of Pinus strobus in the northeastern United States, frequently attributed to "ozone damage," is not due to ozone. The pathological anatomy of affected needles differs from that described for ozone injury and is virtually identical to that described as "semimature-tissue needle blight." The syndrome on affected trees throughout the northeastern United States is consistently associated with the presence of the needlecast fungus, Canavirgella banfieldii. This fungus occurs in the mesophyll of both healthy appearing and dying tissues of such needles before these needles have elongated to half their mature size. The pathological anatomy of infected needles agrees with that described for needlecasts by other researchers, beginning with R. Hartig. In contrast, healthy clones of field-symptomatic and field-asymptomatic trees exposed in open-top chambers to carbon-filtered air and to air adjusted on an hourly basis to 3× ambient ozone concentrations incurred a distinctly different tip necrosis. These necrotic tissues were delimited by an intercellular gummy deposit of unknown composition that appeared to be a type of walling-out response. No hyphae were present in these needles. The pathological anatomy of such needles resembled neither that of the symptomatic parent trees in the field, nor that previously demonstrated in various conifers as due to ozone.Key words: Pinus strobus, Canavirgella banfieldii, needle blight, needlecast, ozone.
Allelopathic interference of chickweed, Stellaria media with seedling growth of wheat (Triticum aestivum)
Authors: Inderjit  , Dakshini KMM
Published: April 2011

The question whether or not annual weeds are allelopathic under field conditions is important in assessing the interference potential of annual weed species. Research was conducted to investigate the probable involvement of allelopathy in the interference potential of chickweed, Stellaria media, a polycarpic winter annual weed. Chickweed maintains heterogeneous populations represented by different age-classes under natural conditions. Results indicate that both young and mature growth stages of chickweed contribute water-soluble phenolics to the soil. Soil amended with matured chickweed had a higher phenolic content than weed-infested soils. Both weed-infested and weed-amended soil affect the seedling growth of wheat. Chickweed could be allelopathic also to a crop of the current season under natural conditions, as it contributes water-soluble compounds to its associated soil.Key words: allelopathy, competition, chickweed, phenolics, weed, wheat.
Pre-European settlement conditions and human disturbance of a coniferous swamp in southern Ontario
Authors: Bunting M Jane , Morgan Clayton R , Bakel Mark Van , Warner Barry G
Published: April 2011

A vegetation survey at Oil Well Bog, southern Ontario, suggested that the central Picea mariana - Sphagnum (black spruce swamp) community represented the most mature point in the wetland succession. Pollen analysis of short sediment cores from beneath three major communities in the wetland (black spruce swamp, white pine swamp, and low shrub swamp) showed that the black spruce community only became established in the last 100 years. From around 2000 BP, the wetland was dominated by low shrubs with a tall shrub element. Upland forest composition around the wetland changed around 500 BP, with a decrease in percentages of Fagus and an increase in Pinaceae. At the same time trees colonized parts of the wetland. When the upland forest was cleared by European settlers (ca. AD 1830-1845), low shrub communities reestablished, suggesting that initially the wetland surface became wetter. Over time, the present-day mosaic of swamp types began to develop. The pollen analyses showed that the black spruce swamp is present as a result of changes in the wetland hydrology induced by human activity, and the fragmentary low shrub vegetation community (which contains locally rare plant species) represents a relic of the pre-European settlement wetland community.Key words: paleoecology, wetland development, hydroseral succession.
Bitter cherry (Prunus emarginata) distribution, successional dynamics, and implications for the role of the seed bank
Authors: Oakley Brian B , Franklin Jerry F
Published: April 2011

Bitter cherry (Prunus emarginata (Dougl.) Walp.) is a largely unstudied early successional tree native to the Pacific Northwest. We used multiple regression and regression tree analyses to identify the most significant variables describing the distribution of bitter cherry populations in the western Cascade Range of Oregon. To determine if bitter cherry relies on a soil seed bank for regeneration after disturbance, we compared successional patterns to direct measures of buried seed. Measurements from 78 sites ranging in age from 1 to 50 years since disturbance and 29 years of permanent plot data showed density, constancy, and cover were low in the first decade after disturbance and did not peak until the third decade. Based on these patterns, we inferred that bitter cherry is not an obligate seed bank species. We did find viable seeds stored in the soil (25.0 ± 6.4 seeds/m2 (mean ± SE) on sites with >600 live stems/ha) but concluded that historical disturbance intervals greater than the length of time seeds can remain viable in the soil have limited bitter cherry regeneration from a seed bank and, as a result, its distribution and abundance. Bitter cherry may play an increasingly important role in Pacific Northwest forests given the large areas of early successional habitat created by frequent timber harvests.Key words: H.J. Andrews Experimental Forest, seed bank, early succession, CART.
Halosarpheia heteroguttulata sp.nov. from submerged wood in streams
Authors: Wong S W , Hyde K D , Jones EBG
Published: April 2011

A new species of Halosarpheia, H. heteroguttulata, is described from wood submerged in streams and lakes in Australia, Brunei, Hong Kong, Mauritius, the Philippines, and South Africa. It differs from other species in the genus in ascospore dimensions, and consistently large guttule(s) in the apical cell, but many smaller guttules in the basal cell. The species is illustrated with light and scanning and transmission electron micrographs and compared with other Halosarpheia species.Key words: appendage ontogeny, freshwater Ascomycete, Halosarpheia, taxonomy, ascospore ultrastructure.