bluuebunny/crossref_metadata_2025 huggingface dataset:
Caractérisation des chutes de litière et des apports au sol en nutriments dans une mangrove de Guyane française
Authors: Betoulle Jean Luc , Fromard François , Fabre André , Puig Henri
Published: April 2011

Litter falls and their contributions to soil nutriments were measured in five distinct facies of a mangrove in French Guyana. These facies were characterized by their distance from the sea, their floral composition (Laguncularia racemosa (L.), Avicennia germinans (L.) Stearn, Rhizophora spp.), and their structural features. Data were analyzed according to facies and to species for litters, as well as to seasons for the nutriments. This mangrove produced respectively 8.8 and 8.7 t·ha1·year1 of litter at the pioneer and senescent stages submitted to strong environmental constraint and 12.5 and 12.6 t·ha1·year1 for young and mature stages where developmental conditions are optimum. Nitrogen and carbon inputs were estimated to 1.3 × 102 and 6.4 t·ha1·year1, respectively. Litter appeared rich in phosphorous, corresponding with the high concentrations characterizing the sediments. For a given species, magnesium and calcium concentrations were constant between facies, whereas potassium and sodium concentrations varied according to the distance from the sea. Differences were perceived between species for all nutriments except sodium. Results are discussed in relation with the ecophysiological characteristics of the mangrove trees and the specific sedimentology of Guyana coast and are replaced in the perspective of an improved knowledge of the carbon and mineral balances in tropical coastal ecosystems.Key words: mangrove, French Guyana, litter, carbon balance, mineral nutriments, spatial variations.[Journal translation]
Do rare pines need different conservation strategies? Evidence from three Mexican species
Authors: Molina-Freaner Francisco , Delgado Patricia , Piñero Daniel , Perez-Nasser Nidia , Alvarez-Buylla Elena
Published: April 2011

Mexico is a major center of diversity for the genus Pinus as it has the greatest number of species in the world. Many species are now restricted to Mexico, and some are represented by very small populations and are in danger of extinction. In this study we examined allozyme variation in three rare species of Mexican pines: Pinus pinceana Gord., Pinus lagunae M.F. Passini, and Pinus muricata D. Don, with the objective of providing conservation guidelines. The three species had relatively high levels of genetic variation with mean expected heterozygosities of 0.373, 0.386, and 0.346 for P. pinceana, P. lagunae, and P. muricata, respectively. We found marked differentiation among populations and significant inbreeding within populations of the three species. These values are larger than the range reported for most conifers and suggest that conservation strategies of these rare pines require focusing on the viability of several populations. Given that our knowledge about the demographic status of the three species is scarce, we propose a mixed strategy of conservation. For P. lagunae, we propose an in situ strategy, whereas for P. pinceana and P. muricata we propose an ex situ strategy of conservation until permanent protection can be provided for several of their populations.Key words: genetic structure, conservation, rare pines, Pinus pinceana, Pinus lagunae, Pinus muricata.
Molecular systematics of the ascomycete genus Farrowia (Chaetomiaceae)
Authors: Untereiner Wendy A , Débois Valérie , Naveau Françoise A
Published: April 2011

The genus Farrowia D. Hawksworth was established for members of the Chaetomiaceae with Botryotrichum-like anamorphs and long-necked ascomata, but the separation of Farrowia from Chaetomium Kunze has been questioned by mycologists who did not consider these characters to be significant at the generic level. The recent description of a species of Chaetomium with an aleurioconidial anamorph and long-necked ascomata prompted us to explore this question employing molecular characters. We sequenced a portion of the nuclear large ribosomal subunit rRNA gene (28S) of members of the Sordariales including species of Chaetomium, Farrowia and Thielavia. Phylogenetic analyses confirmed the monophyly of the Sordariales and the close relationship of Aporothielavia leptoderma to the genus Chaetomium. A sequence-based phylogeny identified a well-supported clade that included Chaetomium floriforme, Chaetomium sphaerale, members of the genus Farrowia, and longicollous species of Chaetomium with aleurioconidial anamorphs. A clade containing Chaetomium brevipilium, Chaetomium cuyabenoensis, Chaetomium homopilatum and species of Farrowia was inferred from the analysis of morphological characters, but this data set was found to be incongruent with the 28S sequence data. While these results are in agreement with the hypothesis that species of Farrowia comprise a group of closely related taxa, they do not provide strong support for the recognition of the genus Farrowia.Key words: anamorph, aleurioconidia, Botryotrichum, Chaetomium, 28S ribosomal RNA gene sequences.
Allozyme variation and population structure of Carex humilis var. nana (Cyperaceae) in Korea
Authors: Huh Man Kyu
Published: April 2011

Genetic diversity and population structure of 22 Carex humilis var. nana Ohwi (Cyperaceae) populations in Korea were determined using genetic variation at 23 allozyme loci. This is a long-lived herbaceous species with a widespread distribution in eastern Asia. The 12 enzymes revealed 23 putative loci, of which 11 were polymorphic (47.8%). Genetic diversity at the varietal level and at the population level was 0.131 and 0.118, respectively. Total genetic diversity (HT = 0.274) and within population genetic diversity (HS = 0.256) were high, whereas the extent of the population divergence was relatively low (GST = 0.068). An indirect estimate of the number of migrants per generation (Nm = 3.42) indicated that gene flow was high among Korean populations. Wide geographic ranges, perennial herbaceous nature, and the persistence of multiple generations are associated with the high level of genetic variation. A distinct difference between Asian and North American Carex is shown in the proportion of genetic variation (GST) (p < 0.001). The mean GST of Asian Carex was estimated as 0.056; thus, only 5.6% of genetic variability was distributed among populations, whereas the mean GST of North American Carex was estimated as 19.5% (3.5 times higher). It is probable that the geographical distance between population pairs and presence or absence of glacial history may play roles in the substantial difference between both groups.Key words: Carex humilis var. nana, genetic diversity, population structure.
Variation in leaf epidermal and stomatal traits ofPopulus trichocarpafrom two transects across the Washington Cascades
Authors: Dunlap J M , Stettler R F
Published: April 2011

Epidermal and stomatal cell traits were examined on late leaves of 40 black cottonwood (Populus trichocarpa Torr. & Gray) clones originating from the mesic Nisqually, and xeric Yakima river valleys of Washington. Four leaves per clone were collected from 1-year-old trees in two replicated common gardens located in Puyallup (western Washington) and Wenatchee (eastern Washington). In Puyallup-grown material, Yakima clones had abaxially 14% smaller epidermal cell diameters (CDIAM) and 27% greater cell densities (CDEN; No. per mm2), and 25% smaller leaves than Nisqually clones (p [Formula: see text] 0.03). Abaxial stomatal densities (STDEN; No. per mm2) were highest (206) in the lower elevation, xeric-origin Yakima clones, as compared with an average of 120 in Nisqually clones. A higher proportion of Yakima leaves had shorter stomates than those from the Nisqually at both sites (p [Formula: see text] 0.002). Besides shorter stomates (p [Formula: see text] 0.030), the lower elevation Yakima clones generally had higher STDEN and ratios of STDEN to CDEN than those clones from the upper group (p [Formula: see text] 0.098). Acclimation of Wenatchee-grown clones to the hotter, drier summer climate was also evident, as they generally had smaller CDIAM, and higher CDEN and STDEN than those grown at Puyallup. Genetic variances (among rivers, groups within river, and clones within group within river) ranged from 42 to 84% with clone being dominant for epidermal traits while the other two components were dominant for stomatal traits. In the Yakima leaves, much of the genetic variance (group and clone within group) resided in the group component. Broad-sense heritabilities averaged 72%, indicating moderately strong genetic control in most traits. This study provides further evidence of genetic variation in P. trichocarpa at the regional and local scales across the Washington Cascades.Key words: Populus trichocarpa, black cottonwood, stomata, adaptation, acclimation, genetic variation.
The evolutionary significance of variation in infection behavior in two species of rust fungi on their hosts and related nonhost plant species
Authors: Eckenwalder James E , Heath Michèle C
Published: April 2011

We explored the association between the phylogeny of 14 species of beans in the genera Phaseolus and Vigna (subtribe Phaseolinae) and the progress of infections in them caused by two pathogenic rust fungi, Uromyces appendiculatus (Pers.) Unger and Uromyces vignae Barclay. The analyses involved construction of phenograms, ordinations, and cladograms derived from the infection characteristics and their comparison to a composite of three previously published DNA phylogenies. The patterns of infection by U. vignae showed no relationship to the phylogeny of the infected plants. The course of infection by U. appendiculatus, however, displayed a significant phylogenetic component, although the defense responses of the infected plants themselves did not. These differences in phylogenetic signal between infections caused by the two fungi may reflect distinct evolutionary histories with members of the Phaseolinae, a long association for U. appendiculatus but a much more recent one for the more host-specific U. vignae.Key words: bean rust, cowpea rust, evolution, infection characteristics, Phaseolus, Vigna.
Pollen tube growth and inhibition in distylous and homostylousTurneraandPiriqueta(Turneraceae)
Authors: Tamari Farshad , Athanasiou Andreas , Shore Joel S
Published: April 2011

We investigate sites of incompatibility for five Turnera L. species and for Piriqueta caroliniana (Walt.) Urban using aniline blue staining of pollen tubes and fluorescence microscopy. We show that sites of incompatibility occur in the stigma and upper regions of the style. There is an asymmetry between the morphs where, following selfing, pollen tubes tend to grow further into long-styled compared to short-styled plants, although the difference is not particularly marked. We demonstrate for the first time a qualitative difference in the appearance of pollen tubes. Upon self-pollination, pollen tubes in short-styled plants do not produce callose plugs, while all other pollinations result in callose plug formation. This could indicate that there is a difference in the mechanisms of incompatibility between the morphs. Exploiting crosses between two populations of Turnera scabra Millsp. that differ in flower size, we found no support for the hypothesis that incompatibility of long-styled plants is the result of insufficient nutrient reserves in pollen. Bud-pollinations provided limited support for the hypothesis that a short-specific style protein is involved in incompatibility. Crosses between distylous and homostylous species provided support for a recombinant origin for homostyly for four species, while deviations from this expectation were observed in four instances.Key words: distyly, homostyly, self-incompatibility, callose, pollen tubes, Turnera.
Alteration in flowering time causes accelerated or decelerated progression throughArabidopsisvegetative phases
Authors: Steynen Quintin J , Bolokoski Dee A , Schultz Elizabeth A
Published: April 2011

We have identified three phases within the wild-type Arabidopsis thaliana (L.) Heynh. rosette, based on significant differences in leaf shape, size, vascular pattern, and presence of abaxial trichomes. To test the hypothesis that a single, central mechanism controls the progression through all plant phases and that conditions that alter the time to flowering will also alter the progression through vegetative phases, we analysed the rosette phases under such conditions. In support of our hypothesis, we determined that those conditions (loss of LEAFY activity, short days) that decelerate time to flowering show decelerated progression through the rosette phases, while those conditions (loss of TERMINAL FLOWER, overexpression of LEAFY, low light) that accelerate time to flowering show accelerated progression through the rosette phases. In all conditions except short days, the length of the first phase was unaffected, indicating that this phase is less susceptible to influences of the central mechanism. Progression through the subsequent two rosette phases was accelerated differentially, such that the second phase was affected more strongly than the first. This supports the idea that, in the rosette, as in the inflorescence, the inhibition of phase transition by the central mechanism is gradually decreasing.Key words: phase change, flowering time, Arabidopsis thaliana, LEAFY, TERMINAL FLOWER, heteroblasty.
The mating system in natural populations of western redcedar (Thuja plicata)
Authors: O'Connell Lisa M , Viard Frédérique , Russell John , Ritland Kermit
Published: April 2011

Outcrossing rates and the correlation of paternity were estimated in six natural populations of western redcedar (Thuja plicata Donn. ex D. Don) in southwestern British Columbia. Over 3000 offspring were assayed, as progeny arrays, for the only sufficiently polymorphic isozyme locus in this species, glucose-6-phosphate dehydrogenase. Estimates of population outcrossing rates ranged from 0.173 to 1.257 and averaged 0.715 ± 0.045 (mean ± SD). Estimates of the correlation of paternity generally did not differ from zero. Six of the seven outcrossing estimates (one population was surveyed in two consecutive years) were higher than a previous seed orchard study. However, these outcrossing rates are still lower than those estimated for most other species of conifers. Population outcrossing rates also showed wide variation, and this variation is discussed in terms of ecological and phenological differences among populations.Key words: Cupressaceae, conifers, isozymes, outcrossing rate, inbreeding.
Maturation of the tracheary elements in the roots of Pinus banksiana and Eucalyptus grandis
Authors: Taylor J H , Peterson C A
Published: April 2011

Tracheary elements of the xylem are responsible for the longitudinal (axial) transport of water and ions that have moved radially across the root. These vessel members and (or) tracheids mature some distance behind the root tip, and it is generally believed that this distance is directly related to root growth rate. To test this idea, the distances behind the root tip at which tracheary elements of pouch-grown Pinus banksiana Lamb. and Eucalyptus grandis W. Hill ex Maiden mature were examined. From each species, three root tip types (white, brown, and ectomycorrhizal short lateral) were assessed. Unlike previous studies of this topic, two methods of testing tracheary element maturity were employed concurrently. The first was anatomical and involved visualizing the deposition of lignin in the walls of the tracheids or vessel members. The second was functional and consisted of determining the capability of the tracheary elements to conduct a fluorescent, tracer dye. The distance behind the root tip at which the conductive xylem cells mature varied from 0.16 to 1.6 mm and was highly dependent on species and root type. No significant correlation was found between growth rate and proximity of tracheary element maturation to the tip for white roots. The presence of lignin in the tracheary element wall was not a reliable indicator of the cell's functional maturity.Key words: conductivity, development, roots, tracheary elements, xylem.
Phosphorus solubilization and pH changes as a result of the interactions between soil bacteria and arbuscular mycorrhizal fungi on a medium containing NH4+as nitrogen source
Authors: Villegas J , Fortin J A
Published: April 2011

This paper reports the effects of Glomus intraradices (Schenck & Smith) external mycelium, mycorrhizal, and nonmycorrhizal transformed carrot roots (alone or in interaction with Pseudomonas aeruginosa (Schroeter) Migula, Pseudomonas putida (Trevisan) Migula, or Serratia plymuthica (Dyar) Bergey et al.) on phosphorus solubilization and pH changes of the medium. All experiments were conducted in a two-compartment Petri plate system with a NH4+medium containing an insoluble source of phosphorus (P). In interaction with P. aeruginosa, G. intraradices mycorrhizal roots and G. intraradices external mycelium enhanced solubilization of sparingly soluble sources of phosphates above the levels reached with each culture alone. These improvements were correlated with changes in the pH of the media.Key words: Glomus intraradices, P solubilization, external mycelium, Pseudomonas aeruginosa, Pseudomonas putida, Serratia plymuthica.
Anatomical features at the disarticulation zone in florets of fatuoid and nonfatuoid oat (Avena sativa L.)
Authors: Hoekstra G J , Darbyshire S J , Mather D E
Published: April 2011

In oat (Avena sativa L.), the manner by which mature florets separate from the inflorescence depends on whether the plant is fatuoid or nonfatuoid and on whether it has naked or hulled grain. The anatomical basis for these differences is not well understood. Here, anatomical features were examined at the intersection of rachilla and lemma callus (disarticulation zone) in florets of fatuoid hulled-grain oat, which "shatter", and of nonfatuoid hulled-grain oat, fatuoid naked-grain oat, and nonfatuoid naked-grain oat, none of which shatter. A layer of one to several rows of small, thick-walled cells usually occurred at the disarticulation zone of fatuoid hulled-grain florets. This layer was less frequently observed at the disarticulation zone of nonfatuoid florets or fatuoid naked-grain florets. Visible at the early stages of development, these rows of small cells apparently form an abscission layer in mature florets of hulled-grain fatuoids. Disarticulation of florets is further assisted by the disintegration of medial parenchyma tissues of the lemma callus, resulting in the formation of lacunae around the vascular bundles. Although a layer of small cells in the disarticulation zone was often seen in mature fatuoid naked-grain florets, it did not function as an abscission layer.Key words: Avena, oat, fatuoid, disarticulation, abscission, shattering.
Growth and metabolism of cells and tissue of jack pine (Pinus banksiana). 2. The quantitative analysis of the growth of callus from hypocotyls and radicles
Authors: Chalupa V. , Durzan D. J. , Vithayasai C.
Published: April 2011

Jack pine (Pinus banksiana Lamb.) calluses from hypocotyls and radicles of 5-day-old seedlings were established when the yield of callus from the donor was greatest compared with other stages of germination. Effects of macroelements, organic nitrogen sources, growth regulators, temperature, light, and carbon dioxide on the fresh and dry weights of callus indicated that the medium formulated was optimal. Although tissues assimilated exogenous sources of N, they also depended upon the food reserves that were mobilized during germination as the density (dry weight per cubic centimetre) of calluses gradually fell.Initially, the proliferation and release of cells from their neighbors was mainly on the outer surface of tissue. Eventually all cells appeared to divide to yield a friable, green callus with cell clumps that were easily dissociated from one another. Some clumps, especially those below the surface and near vascular tissues, were filamentous and exhibited polarity resembling the early stages of pine embryogeny.The growth form of hypocotyl callus was autocatalytic, whereas radicle callus was exponential for both dry weight and volume. Final size was greater in hypocotyl callus. In both systems, the relative growth rates of weight and volume correlated negatively but significantly to water intake. Average parameters of growth rates were calculated using Richards's comprehensive growth function.
Taxonomic and ecologic observations of zoosporic fungi in soils of a high-arctic ecosystem
Authors: Booth Tom , Barrett Paul
Published: April 2011

Phylctochytrium arcticum Barr and Rhizophlyctis harderi Uebelmesser are reported as additional taxa in soils of Truelove Lowland (Devon Island, N.W.T.) and Nowakowskiella spp., Olpidium pendulum Zopf, Pythium irregularae Buisman. Pythium spp., Phlyctochytrium arcticum, and Rhizophydium sphaerotheca Zopf are readily detectable as active organisms in Lowland microhabitats. Species diversity is greatest in mesic and warm soils and species composition of water-logged soils is different than dry soils. Soil acidity effects on distribution are discussed and autecological considerations of Nowakowskiella elegans and R. sphaerotheca with respect to pH, percentage N, C, and P, milliequivalents Ca2+ and Mg2+, moisture, and temperature are presented.
Ash dieback and drought
Authors: Tobiessen Peter , Buchsbaum Steven
Published: April 2011

We give further evidence of the correlation of the inception of dieback in white ash and local drought. We suggest that the marked stomatal sensitivity of ash to drought could be an important factor coupling dieback to drought.
Heat production and pollination in Araceae
Authors: Moodie G. E. E.
Published: April 2011

The ecological role of heat production in Araceae has not been extensively investigated. The possibility that carbon dioxide and heat production are components of a carrion, dung, and mammal mimicry syndrome deserves consideration. Warm inflorescences might also serve as significant shelters for pollinators of species flowering during cold seasons.
Technique for the observation of early morphological changes during ectomycorrhiza formation
Authors: Fortin J. André , Piché Yves , Lalonde Maurice
Published: April 2011

Flat, transparent polyester growth pouches were used for synthesis of ectomycorrhizae on Pinus strobus seedlings. Typical ectomycorrhizae with mantle and Hartig net were obtained within 5 days after inoculation with Pisolithus tinctorius. An extensive extramatrical network of hyphae and hyphal strands could be observed within 15 days after ectomycorrhizae formation. The process was somewhat slower with Cenococcum graniforme. Other proven ectomycorrhizal fungi on P. strobus were unsuccessful in forming ectomycorrhizae under conditions used in these experiments.
Perithecium growth and expansion in Chaetomium globosum
Authors: Froeyen Ove Johan
Published: April 2011

The development of the perithecium of Chaetomium globosum has been studied by light and transmission electron microscopy. During all developmental stages the growth and expansion seem to be caused by the growth and enlargement of actively growing hyphae in an apical growth region. This growth region, at a later stage, also gives rise to the ostiole. The perithecial cavity is formed by the autolysis of hyphae in the inner growth region and in the hymenium. The possibility that the perithecial expansion is caused by volume increase of the hyphae in the lower parts of the growth region is discussed. The ostiole seems to be opened by the action of an inner pressure caused by the hymenial growth. The tangential orientation of the inner peridial cells and the cells lining the centrum is caused by displacement of cells from the growth axis and by perithecial unfolding.
Wound periderm formation in Juniperus occidentalis in response to Arceuthobium campylopodum
Authors: Jaramillo Annabelle E.
Published: April 2011

Western juniper (Juniperus occidentalis) appears to resist infection by dwarf mistletoe (Arceuthobium campylopodum) with tissue necrosis and the formation of a wound periderm thereby restricting the penetrating structure of the parasite to peripheral host tissues.
In vitro germination and pollen tube growth of maize (Zea mays) pollen. IX. Pollen source genotype and nonionic surfactant interactions
Authors: Pfahler P. L. , Linskens H. F. , Wilcox M.
Published: April 2011

Because of their structure and active metabolic state, pollen grains are vulnerable to any agent in the in vitro germination medium. Surfactants are used in biological systems to reduce surface tension but are also known to produce subtle biochemical effects. This study investigated the effect of three nonionic surfactants on the germination characteristics of pollen grains from three pollen source genotypes. Pollen grains from three single cross hybrids (Wf9 × H55, K64 × K55, Ky228 × Ky226) were cultured on an artificial medium (15% sucrose, 0.6% bacto-agar, 0.03% calcium nitrate, 0.01% boric acid) supplemented with all possible combinations of three concentrations (10, 100, 1000 ppm, v/v) of the following surfactants: (i) Tween 80 (polyoxyethylene sorbitan monooleate); (ii) X-114 (alkyl phenoxypolyethoxy ethanol); and (iii) commercial sticker spreader (alkyl olefin aromatic polymers). A control containing no supplement was included. Over all genotypes, increasing concentrations of Tween 80 had the least effect on the germination characteristics measured (germination and ruptured percent, pollen tube length at 1, 2, and 3 h after inoculation) and X-114 had the greatest effect with no germination found above 10 ppm. For most of the germination characteristics, highly significant pollen source genotype X concentration interactions were found for each surfactant. The direction and magnitude of the surfactant effects depended on the surfactant, its concentration, the germination characteristic involved, and the pollen source genotype.
Some effects of soil and air temperature on growth of Agropyron spicatum following clipping or burning
Authors: Willms W. , Bailey A. W. , McLean A.
Published: April 2011

Studies were made in both the Artemisia tridentata and Pseudotsuga menziesii communities to examine some factors affecting available growth in spring. The appearance of tillers was examined in relation to species (Agropyron spicatum. Agropyron cristatum. Poa sandbergii) and temperature. The rate of tiller elongation in Agropyron spicatum was studied in relation to temperature and fall clipping or burning while tiller length was examined in relation to fall or late-winter burning. Tiller development in all species appeared within the same week. The community had no apparent effect on tiller initiation. However, growth in Agropyron spicatum was arrested for 1 week in the Pseudotsuga menziesii community after the tillers appeared at the ground surface. The rate of tiller elongation was not affected by clipping. However, burning resulted in a more rapid rate at cool temperatures and a slower rate at warm temperatures. Tillers were shorter in plants burned in late winter than in plants burned in fall.
Resistance to Cronartium ribicola in Pinus monticola: reduced needle-spot frequency
Authors: Hoff R. J. , McDonald G. I.
Published: April 2011

Low frequency of needle spots caused by the blister rust fungus (Cronartium ribicola J. C. Fisch. ex Rabenh.) in western white pine (Pinus monticola Dougl.) appears to be an expression of a horizontal resistance factor in secondary needles. Heritability averaged 37% for two sets of a 4 tester × 10 candidate mating system. We discuss the implications of these results with respect to developing varieties of western white pine resistant to blister rust.
Photorespiration and internal recycling of CO2 in the submersed angiosperm Scirpus subterminalis
Authors: Søndergaard Morten , Wetzel Robert G.
Published: April 2011

The presence and magnitude of photorespiration in the submersed freshwater angiosperm Scirpus subterminalis Torr. was investigated by gas-exchange characteristics in an open water-flow system. The minimal rates of photorespiration during active photosynthesis were measured by following the time course of differential 14CO2 and 12CO2 uptake. At 8 mg O2 L−1 (equal to oxygen saturation at 20 °C), the rate was 0.4 μg C (mg organic dry weight)−1 h−1, which was about 10% of net photosynthesis under the experimental conditions. Increasing the oxygen concentration to 30 mg O2 L−1, enhanced photorespiration to 30% of net photosynthesis. It was shown that the concentration of oxygen affected net photosynthesis, CO2 evolution into CO2-free water in the light, the post-illumination CO2 burst, and the CO2 compensation point.The effect of the internal gas space on recycling of CO2 was investigated by comparing gas-exchange by intact and sectioned leaves. About 30% of the CO2 of photorespiratory origin was recycled internally within the lacunal system. The gas-exchange characteristics of Scirpus were similar to those observed in terrestrial C3 species although of a minor magnitude and a different time course. The ecological implications of these finds are discussed.
Multivariate morphometric relationships between Hordeum jubatum and Hordeum brachyantherum in Canada and Alaska
Authors: Baum Bernard R.
Published: April 2011

Scoring for morphometric characters was conducted on both herbarium material (including artificially produced hybrids) and specimens collected across Canada and Alaska and studied in situ. The data from herbarium material were analysed by means of various principal component analyses and by a series of discriminant analyses. The morphometric data from field material were obtained by repeated observations of every spikelet along the one side of each spike selected for analysis. A representative sample of spikes was collected from every population visited, with emphasis on hybrid populations. These repeated observations within spikes were also made in order to evaluate the reliability, representability, and taxonomic value of every spikelet and the degree of homologization within a spike. The field data were analysed by means of discriminant analyses and various cluster analyses.The conclusion reached is the recognition of three species for Canada and Alaska, H. jubatum L., H. caespitosum Scribn., H. brachyantherum Nevski, and a hybrid H. jubatum × brachyantherum representing F1 and F1-like phenotypes. Classification function coefficients were computed and are provided in this paper in order to effect both the identification of the three taxa and the hybrid and their circumscription.All the herbarium specimens were identified by means of these coefficients and, as a result, previously unsuspected hybrids were revealed. This study indicated that an analysis of herbarium specimens alone can be misleading and, consequently, that field data are necessary. It is also demonstrated that the spikelets within a spike are not uniform enough for taxonomic reliance to be placed on observations made on one spikelet alone.
Laser-induced fluorescence in aquatic plants
Authors: Czuba M. , Mortimer D. C.
Published: April 2011

Aquatic plants exposed to 488-nm laser light emit a bright, red–orange fluorescence. This fluorescence is brightest in young tissues, especially meristematic tissue of both shoots and roots. Older tissues of shoots and root hair areas both emit a pink and a white fluorescence respectively. The quality and intensity of fluorescence are decreased by the age of the tissue.
Natural selection for spotted leaves: parallel morph ratio variation in three species of annual plants
Authors: Ganders Fred R. , Griffiths A. J. F. , Carey Ken
Published: April 2011

Three sympatric species of annuals, Collinsia parviflora, Mimulus guttatus, and Trifolium tridentatum, are polymorphic for anthocyanin spots on the upper epidermis of the leaves. In each case the presence of spots is determined by a single dominant gene. Spotted morphs are most obvious in young plants, and in Collinsia and Mimulus the spotted phenotype is expressed only at low temperatures. Phenotype frequencies were determined in population samples in the Flat Top Islands, British Columbia, and at Anacortes, Washington. In all three species spotted morphs are more frequent in cold, exposed habitats, and the three species show parallel patterns of morph ratios in the sites studied. This provides strong evidence that the polymorphism is under the control of natural selection. Direct evidence of the adaptive significance of spotted leaves is lacking, but indirect evidence suggests the hypothesis that leaf spots may be advantageous in cold microhabitats because they increase leaf temperature during the winter growing season of these annuals.
Thin-section, freeze-fracture, and energy dispersive x-ray analysis studies of the protein bodies of tomato seeds
Authors: Spitzer Ernest , Lott John N. A.
Published: April 2011

Protein bodies of dry seeds of tomato (Lycopersicon esculentum) from radicle, hypocotyl, cotyledon, and endosperm tissue were extensively studied using thin-sectioning, freeze-fracturing and energy dispersive x-ray (EDX) analysis. Protein bodies varied in size, were oval to circular in section, and generally consisted of a proteinaceous matrix, globoid crystal, and protein crystalloid components. Size, shape, and arrangements of globoid crystals and protein crystalloids varied even within the same cell. Globoid crystals were generally oval to circular in section. They were always surrounded by a proteinaceous matrix. In a given protein body the number present ranged from a few to numerous. A protein body generally contained only one protein crystalloid. In section, protein crystalloids were irregular or angular in shape. They were composed of substructural particles which formed lattice planes. EDX analysis of tomato seed globoid crystals revealed the presence of P, K, and Mg in all cases, a fact that is consistent with globoid crystals being phytin-rich. Rarely, small amounts of calcium were found along with P, K, and Mg in globoid crystals of each of the tissue regions considered. The distribution pattern of cells with Ca containing globoid crystals was random. Small amounts of Fe and Mn were also found in the globoid crystals of protein bodies from certain cell types. These two elements, unlike calcium, were specific in terms of their distribution. Globoid crystals from the protodermal cells often contained Mn and Fe. The globoid crystals from provascular tissue of radicle, hypocotyl, and cotyledon regions often contained Fe while globoid crystals in the first layer of large cells surrounding these provascular areas always contained Fe. Results from EDX analysis of the proteinaceous material from the protein bodies are presented and discussed as are variations in elemental content due to different fixations.
Electrophoretic evidence supporting self-incompatibility in Lotus corniculatus
Authors: Dobrofsky Shirley , Grant W. F.
Published: April 2011

Self-incompatibility, a prefertilization event, and self-sterility, a postfertilization event, have both been suggested as causes for differences in seed set between cross- and self-pollinated florets in Lotus corniculatus L. Ovary protein subunits of selfed, crossed, and unpollinated florets of L. corniculatus cv. Mirabel were studied using polyacrylamide gel electrophoresis. Banding patterns differed for all three conditions. Ovary protein differences were found prior to the time fertilization is known to occur, thereby providing evidence that self-incompatibility is at least partially responsible for the reduced seed set after self-pollination.
Cytoskeletal ultrastructure and motility of cells
Authors: Allen Robert Day
Published: April 2011

A brief review of the role of contractile proteins in dynamic changes in the cytoskeletons of motile cells is followed by a more detailed account of cytoskeletal ultrastructure in the motility of the giant amoeba, Chaos carolinensis and of human blood platelets.
Characterization of actin, actinin, and myosin isolated from Physarum
Authors: Hatano Sadashi , Owaribe Katsushi , Matsumura Fumio , Hasegawa Takayuki , Takahashi Sho
Published: April 2011

Our work on actin and myosin from Physarum is briefly reviewed, and the physicochemical properties of these proteins are compared with those of the corresponding proteins obtained from rabbit striated muscle. In this article both similarities and differences between these preparations are emphasized in order to characterize the Physarum actomyosin system. Some properties of Physarum actinin, a regulatory protein of actin polymerization, are also reported. Finally, the assembly and disassembly of F-actin filaments in the reversible superprecipitation of Physarum actomyosin are demonstrated. The mechanism of generation of the motive force for protoplasmic streaming in plasmodium is discussed in the light of these findings.
Contractile proteins and hypotheses concerning their role in phloem transport
Authors: Aikman David P.
Published: April 2011

Contractile and motile proteins have been found in plants. Cytoplasmic streaming in Nitella is not inconsistent with several aspects of an actinomyosin system. Several hypotheses have been advanced, invoking the participation of contractile or motile proteins in phloem transport. The peristalsis hypothesis lacks credibility in absence of strong evidence of existence of sufficiently large tubules. Microperistalsis could be responsible for only a small fraction of the specific mass transfer and may require a faster reaction frequency than acceptable for an ATPase system. Undulating filaments would appear to require a much higher power per unit length than could be generated by actinomyosin. Since electroosmosis and surface flow have already been discounted, the Münch hypothesis must be favoured although not all observational or experimental evidence by any means supports it.
Promotion by tryptophan of growth and root formation in lowbush blueberry pericarp callus cultures
Authors: Nickerson Nancy L.
Published: April 2011

Lowbush blueberry (Vaccinium angustifolium Ait.) pericarp callus grew slowly and formed normal tetraploid roots on Nitsch's medium containing L-tryptophan and kinetin. Both growth and rooting depended on the levels of these two substances in the medium. Rooting declined but callus growth rates changed little over successive subcultures. When tryptophan was replaced by indoleacetic acid, indolebutyric acid, 2,4-dichlorophenoxyacetic acid, or naphthaleneacetic acid, callus growth rates increased but no roots formed. Tryptophan medium did not support callus growth or induce rooting unless the tryptophan was autoclaved with the rest of the medium; thus suggesting that an active substance is produced by reaction of the tryptophan with some other constitutent(s) of the medium during heating.
Simultaneous formation of chymopapain inhibitor activity and cubical crystals in tomato leaves
Authors: Akers Carolyn Pruett , Hoff Johan E.
Published: April 2011

Chymopapain inhibitor activity is found in young, excised tomato leaflets exposed to continuous illumination at 30 °C and 50 to 60% relative humidity. Inhibitor activity is accompanied by the formation of cubical crystals in the leaf mesophyll cells. As chymopapain inhibitor activity increases, crystals increase in number and volume. There is a strong positive correlation between crystal volume and inhibitor activity.
Harpella leptosa, a new species of Trichomycetes substantiated by electron microscopy
Authors: Moss Stephen T. , Lichtwardt Robert W.
Published: April 2011

Harpella leptosa (Harpellales, Harpellaceae) from the midget region of blackfly larvae (Simuliidae) is described. With the light microscope it is distinguished from the only known species of the genus, H. melusinae, primarily by its smaller dimensions and less conspicuous holdfast, but electron microscopic studies reveal significant differences in the substructure of the trichospore appendages and holdfast apparatus. Harpella leptosa is presently known only from the northern Rocky Mountains. The two species of Harpella are sympatric, and occasionally live simultaneously in the same host gut.
The influence of substrate on the growth and morphology of Myriophyllum exalbescens and Myriophyllum spicatum
Authors: Aiken S.G. , Picard R. R.
Published: April 2011

Stem cuttings, 30 cm long, of Myriophyllum exalbescens Fern. and M. spicatum L. were planted in three substrates: loam, sand, and peat. Growth responses of these species were compared in three independent experiments each of a duration of 50 days. In some cases M. spicatum grew more vigorously, but the previous growth conditions for the plant material at the start of the experiment influenced the total amount of growth. In all experiments the percentage of ash in M. exalbescens was greater than in plants of M. spicatum grown in the same environment. The two species remained distinct from one another in characteristics of leaf length, number of leaf divisions, and length of internodes near the apex of the main stem. Within each species a marked relationship between morphology and substrate was observed. On the nutrient-poor substrate, sand, leaves of M. spicatum converged in appearance towards leaves of M. exalbescens grown on the nutrient-rich substrate, loam.
Cytological evidence for generic limits in tribe Cladothamneae (Ericaceae)
Authors: Hebda Richard J. , Chinnappa C. C.
Published: April 2011

Meiotic chromosome counts for Elliottia paniculata (Siebold & Zuccarini) Hooker, Elliottia bracteata (Maximowicz) Hooker, and Elliottia pyroliflora (Bongard) Brim and P. F. Stevens (Cladothamneae, Ericaceae) are reported for the first time. In all these species it was determined that n = 11, the same as in Elliottia racemosa Muhlenberg. These results support the conclusion of Brim and Stevens that all the members of Cladothamneae belong in a single genus Elliottia.
Abscisic acid levels and stomatal behavior during drought and recovery in Douglas-fir (Pseudotsuga menziesii)
Authors: Newville Edward G. , Ferrell William K.
Published: April 2011

Foliage of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings from xeric and mesic environments was sampled during two induced, consecutive, drought cycles to determine relationships among leaf resistance, plant water potential, and abscisic acid (ABA) concentration. One group of seedlings was placed in a growth room; the other was kept outside at a nursery under natural conditions. During the first drought cycle, seedlings transpired similarly. During the second drought, xeric seedlings in the growth room and nursery initiated stomatal closure at greater levels of plant moisture stress (PMS) than in the first drought cycle, but stomatal behavior of mesic seedlings was unchanged. During the first drought cycle, a sharp increase in ABA concentration in both ecotypes coincided with increased leaf resistance within a narrow water-potential range. However, after xeric seedlings were rewatered and then subjected to drought, leaf resistances remained low even though the previous threshold PMS and ABA concentrations for stomatal closure were reached. For mesic seedlings in the growth room, ABA concentrations remained high after rewatering and slowly decreased with time, although recovery to predrought leaf resistances was largely completed 2 days after rewatering.
Serological relationships of some fungi of the genus Pythium
Authors: Krywienczyk J. , Dorworth C. E.
Published: April 2011

Antisera were prepared to nine species of Pythium and serological interrelationships were investigated using the double diffusion technique in agarose and immunoelectrophoresis. Among the nine species the following groups were distinguishable: P. aphanidermatum and P. butleri appear to be identical and different from the other species investigated. Pythium coloratum and P. dissotocum were closely related to each other but very distantly related to the remaining species. Pythium pyrilobum cross-reacted strongly with the homologous antiserum, and only faintly with other antisera. The last group includes very cross-reactive species: P. debaryanum, P. irregulare, P. mamillatum, P. sylvaticum, and P. ultimum.
Mycorrhizal associations of some actinomycete nodulated nitrogen-fixing plants
Authors: Rose Sharon L.
Published: April 2011

Flowering plants that fix atmospheric nitrogen in actinomycete-induced nodules were sampled for mycorrhizal associates. Twenty-five species from seven families (Betulaceae, Casuarinaceae, Myricaceae, Rhamnaceae, Rosaceae, Elaeagnaceae, and Datiscaceae) were examined. Samples included were from the United States, Japan, and England.Both mycorrhizae and actinomycete-induced nitrogen-fixing nodules were present on: (i) four species of Alnus, (ii) two species of Casuarina, (iii) eight species of Ceanothus, (iv) four species of Myrica, (v) and one species each of Shepherdia, Hippophae, Cercocarpus, Dryas, Purshia, Comptonia, and Datisca. Soil sieving revealed species of the following genera of vesicular–arbuscular (VA) mycorrhizal fungi: Gigaspora, Glomus, Acaulospora, Entrophospora, and three undescribed taxa soon to be described. Spores of species in the first three genera of fungi were found most frequently from soil sievings. The VA mycorrhizal fungi exhibited distinct distributional patterns when associated with nonleguminous nitrogen-fixing hosts in different habitats. The ectomycorrhizae were not characterized.
Effectiveness of diurnal and nocturnal pollination of two milkweeds
Authors: Bertin Robert I. , Willson Mary F.
Published: April 2011

The relative effectiveness of diurnal and nocturnal pollinators of two milkweed species, Asclepias syriaca and A. vcerticillata, was assessed experimentally and related to patterns of nectar production. Nocturnal pollinators inserted and removed fewer pollinia than diurnal vectors but caused equal pod set, and in A. syriaca, caused greater seed set. We suggest that observed peak nectar production patterns are adaptive in attracting nocturnal pollinators that may be of higher quality than diurnal species. This is one of the first attempts to compare the relative effectiveness of diurnal and nocturnal pollinators of any plant species. The excess of vector visits over that needed to obtain maximum pod set may allow selective abortion and (or) be adaptive in increasing reproductive success through pollinia donation.
Growth habits and phenology of drought-deciduous species in an altitudinal gradient
Authors: Hoffmann A. J. , Walker M. J.
Published: April 2011

Several drought-deciduous species occur in the mediterranean type vegetation of central Chile, some of them extending to the slopes of the Coastal and Andean Ranges, up to 2300 m. The growth habits and phenology at different altitudes are compared in two drought-deciduous, malacophyllous shrubs: Talguenea quinquinervia, a species of restricted distribution, and Proustia cuneifolia, of widespread distribution. The morphology and timing of seasonal events of T. quinquinervia do not substantially change along its altitudinal range of distribution. In contrast, gradual displacement of phenology occurs in P. cuneifolia, with increasing altitude. Its growth habit varies from the presumably original chamaephyte to a phanerophyte, when under optimal conditions, or to a hemicryptophyte in the highest altitudes. Low temperatures and a prolonged snow cover constitute severe limiting factors for the survival of this drought-deciduous life form.