bluuebunny/crossref_metadata_2025 huggingface dataset:
Seasonal patterns of the CO2 exchange characteristics of understory plants from a deciduous forest
Authors: Taylor R. J. , Pearcy R. W.
Published: September 2008

The seasonal patterns of CO2 exchange characteristics were determined for six deciduous forest understory species that differed substantially in time of photosynthetic activity with regard to the time of overstory canopy development. Species that were photosynthetically active only before overstory canopy development were characterized by high maximum light-saturated net photosynthetic rates and high leaf and mesophyll conductances. These early species were, however, active for only a relatively brief period of time. Species that were present during overstory canopy closure initially had moderate light-saturated net CO2 uptake rates that dropped markedly in response to the reduced light intensities after overstory canopy closure. All species present during the summer under the strongly reduced light intensities had low rates of light-saturated net CO2 uptake and low leaf and mesophyll conductances. These species, however, possessed low dark respiration rates which resulted in higher rates of net CO2 uptake at low light intensities than those of the early species. Light-saturated photosynthetic rates were correlated with ribulose-1,5-diphosphate (RuDP) carboxylase activities in mature but not in young expanding leaves.
Physiological aspects of the ecology of Dicranum fuscescens in the subarctic. I. Acclimation and acclimation potential of CO2 exchange in relation to habitat, light, and temperature
Authors: Hicklenton Peter R. , Oechel Walter C.
Published: September 2008

Laboratory measurements of net carbon dioxide exchange in relation to light and temperature were made on Dicranum fuscescens Turn, at Schefferville, Quebec (latitude 55° N), during the summer of 1974. Net CO2 exchange was measured using an open-flow infrared gas analysis system. Moss samples were collected from two field sites (a lowland lichen woodland and highland semitundra region) immediately before the experiments. Temperature optima for photosynthesis in plants from both sites showed acclimation to higher temperatures in the middle of the season. Measured maximum rates of photosynthesis, attained in early July, equalled 2.1 mg CO2∙g dry weight−1∙h−1 in plants from the highland site and 0.74 mg CO2∙g dry weight−1∙h−1 in those from the lowland lichen woodland. Dark respiration rates showed no seasonal temperature acclimation. Radiation levels required for saturation of photosynthesis at optimum temperatures showed an increase from early season through midseason in samples from both populations. A reverse trend towards lower light requirements for saturation was detectable in the late season. Field-collected plants were exposed to different temperature regimes for [Formula: see text] months in growth chambers. During this period, temperature acclimation of photosynthesis to ambient temperature conditions elicited a rapid shift in optimum temperatures for photosynthesis over periods as short as 48 h. All results are discussed in relation to measured environmental parameters in the two study sites throughout the 1974 growing season.
An analysis of elm (Ulmus americana) mortality in a second-growth hardwood forest in southeastern Michigan
Authors: Richardson Curtis J. , Cares Charles W.
Published: September 2008

A second-growth hardwood forest containing both wet lowland and mesic upland sites in southeastern Michigan was studied 24 years after the introduction of Dutch elm disease. American elm (Ulmus americana) surprisingly had the highest importance value (IV = 61/300) (IV = relative density + relative dominance + relative frequency). Two other species (Acer rubrum and Quercus macrocarpa) closely followed elm with IVs of 41/300 and 38/300. respectively. Mortality for all trees surveyed was 20.4%. Elm comprised 86.6% of this total. Although reduced, the present IV for elm and the percentage of living individuals in each diameter class indicate that elm is still an important species in the forest community. Elm mortality reached 100% only on the poorly drained lowland pockets where densities of elm exceeded 50%. Its high reproductive capacity and dispersal rate indicate that elm will continue to exist as an important species, even if not a canopy dominant, in some types of hardwood communities.
Sexual compatibility in Gonium pectorale (Volvocales: Chlorophyceae) from soil of a single pond
Authors: Stein Janet R. , McCauley Marion J.
Published: September 2008

Clones of Gonium pectorale O.F.M. were crossed in all combinations at 20 °C and the resultant zygotes were examined to determine the degree of sexual compatibility within a single pond (dry soil sample originally). Two distinct groups were recognized within the 31 clones isolated and tested from a single sample, with all the clones in one group incompatible with those of the other. However, members of both groups were compatible with three additional clones. The existence of more than one group of sexually compatible clones isolated from a single soil sample indicates the fallacy of applying the term 'population' to such a sample, although geographically a small unit (<15 cm diam).
Chromosome morphology of Clematis, subsection Viornae (Ranunculaceae)
Authors: Dennis W. Michael
Published: September 2008

Cytological studies were made on the following taxa: C. addisonii, C. filifera, C. glaucophylla, C. pitcheri, C. reticulata, C. texensis, C. versicolor, and C. viorna. All species were found to have a somatic chromosome number of 16 with a uniform karyotype consisting of five pairs of metacentric chromosomes with centromeres in the median region and three pairs of acrocentric chromosomes, two pairs with centromeres in the terminal region and one pair with centromeres in the subterminal region. These findings agree with reports of chromosome number and karyotype for other species of Clematis and suggest a marked stability of chromosome complement in the genus.
Ecological studies of hypogeous fungi. II. Sporocarp phenology in a western Oregon Douglas Fir stand
Authors: Fogel Robert
Published: September 2008

Sporocarp phenology of hypogeous or subterranean fruiting fleshy fungi was studied between March 1972 and March 1975 in a 40- to 65-year-old Douglas fir stand in western Oregon. Estimates of yearly productivity ranged from 11052 to 16753 sporocarps ha−1 and 2.3 to 5.4 kg dry weight ha−1. The productivity curve was bimodal as a result of temperature and moisture effects, with peaks in May–June and October. Eleven hypogeous ascomycete species and 13 hypogeous basidiomycete species were collected during the study. Major species that each accounted for 5% or more of the total weight were Tuber murinum, Hymenogaster parksii, Hysterangium crassum, H. separabile, and Truncocolumella citrina var. citrina. Sporocarp moisture content as determined for several species presumably varied with sporocarp age and soil moisture content and ranged from 17.4 to 88.6%. Hypogeous sporocarps had substantially higher macronutrient contents of N, P, and K plus the micronutrients Fe and Al than did epigeous sporocarps of Fomes pinicola. Sporocarp numbers increased exponentially with distance from nearest live Douglas fir stem to a peak at 160 to 200 cm, beyond which numbers dropped sharply. The optimum sporocarp zone was slightly less than the average midpoint between tree stems (205 cm).
Isolation of peroxidase isozymes from two flax genotypes by column chromatography
Authors: Fieldes M. A. , Bashour N. , Deal C. L. , Tyson H.
Published: September 2008

Isolation of the four major peroxidase isozymes (isozymes 1, 2, 3, and 4) of two flax genotypes was achieved by modifying the procedure used by Shannon et al. (1966) for the isolation of horseradish peroxidase isozymes. The net positive and net negative charges of isozymes 1, 2, and 4 were different. Isozyme 3 resembled isozyme 4 in charge but differed in apparent molecular weight. The chromatographic elution profiles of both genotypes were the same. Anionic gel electrophoresis demonstrated that after isolation and repurification, relative mobility differences existed between the corresponding isozymes of the two genotypes for all four isozymes.
The effects of light quality and non-steady-state, localized 14CO2 pulse labeling on net assimilation and 14C translocation profiles in Heracleum lanatum
Authors: Hoddinott John , Gorham Paul R.
Published: September 2008

Red, green, blue, and white light of equivalent intensities of photosynthetically active radiation (PAR) (400–700 nm) had no effect upon leaf diffusion resistance, net assimilation, or translocation of leaves of Heracleum lanatum Michx. at 20 °C. Regardless of light quality at 80 μE m−2 s−1 PAR, 5 min and 40 min after the start of a 2-min application of 70 μCi of 14CO2 to a 1.33-cm2 spot on a leaflet, the major ethanol-soluble labeled assimilates were sucrose and glutamic acid while sucrose was the only labeled translocate. Regardless of light quality at 80 μE m−2 s−1 PAR, 5 min after the start of a 2-min spot tag, well defined ‘wave-like’ translocation profiles consisting of five peaks, 3 to 6 cm apart, were observed along 20 cm of petiole. Regardless of light quality, in 40-min experiments, the ‘wave-like’ profiles were replaced by typical, linear semilogarithmic translocation profiles. It is concluded that the initial ‘wave-like’ profiles were induced by perturbing the steady-state kinetics of synthesis and vein loading labeled sucrose by pulse labeling a small spot with an unusually high concentration of 14CO2. It is possible that pulsed profiles reported by others may have originated in similar fashion.
Formation de l'acide pipécolique chez Triglochin maritima
Authors: Goas Gabrielle , Goas Marie , Larher François
Published: September 2008

Radioactive D-lysine supplied to Triglochin maritima L. shoots can be utilized without configuration inversion. The pipecolic acid is the most radioactive compound. It would be synthetized via the α-ceto-ε-aminocaproïc acid.In the plant, L-lysine can be partly converted into D-lysine; however, the data obtained in the presence of L-[3H1-lysine suggest the possibility of a direct transformation of the L-isomer into pipecolic acid via the adipic semialdehyde.In all cases, the labelled pipecolic acid is the L-enantiomer that is more radioactive in presence of sodium chloride.
Biopotentials along the stem of Helianthus in association with short-term translocation of 14C and chilling
Authors: Woodley S. J. , Fensom D. S. , Thompson R. G.
Published: September 2008

Tracer experiments using 14CO2 fed to leaves and [14C]sucrose fed directly to stems show that localized chilling of a sunflower stem temporarily stops or reduces translocation for 10–15 min. The reduction of translocation seems to extend along the entire stem above and below the chilled section. Biopotential measurements along the stem indicate a cyclic change which corresponds closely in time with the dislocation of translocation. Similar biopotential cycles occur when the top of the plant is given a 100% humidity shock. The translocation profiles obtained are bidirectional from the feeding area and bimodal. In other words, there is a massive portion moving at about 30–100 cm h−1 preceded by a faster but much smaller portion moving at speeds up to 720 cm h−1. Both portions are interspersed with peaks or pulses along them. These pulses are probably moving and, if so, are difficult to explain by a pressure-driven mass-flow mechanism alone.
Promotion of stipe elongation in Flammulina velutipes by a diffusate from excised lamellae supplied with nutrients
Authors: Gruen Hans E.
Published: September 2008

Flammulina velutipes fruit bodies were grown on partly decayed Populus tremuloides sawdust supplemented with wheat bran and malt extract. In each culture there was a gradation in fruit body size, which served to select test specimens at an early stage of growth. Diffusates collected in agar blocks were applied on the apex of decapitated stipes. Plain agar and dilute potato dextrose agar (PDA/2) alone had the same slight effect on growth. Lamellae placed on plain agar caused limited growth promotion. Lamellae on PDA/2 gave 100–150% more growth promotion than on plain agar during early development, but the activity decreased to zero during the middle of the stage of rapid elongation. Lamellae of that age had no effect on young stipes and the older stipes were insensitive to diffusate from young lamellae. Very small amounts of lamellae promoted stipe elongation. Potato extract alone did not stimulate production of the lamellar diffusate and glucose was less effective than the two nutrients combined. A delay of 2 h in applying lamellar diffusate reduced stipe elongation, and there was no response after 12 h delay. Pilear trama did not produce growth-promoting diffusate.
Uptake by soybean root cells of [14C] alanine over a wide concentration range
Authors: King John
Published: September 2008

Uptake of [14C]alanine by soybean (Glycine max L. var. Mandarin) root cells growing in liquid suspension culture was examined over a concentration range of 10−6 M to 10−2 M. Below about 5 × 10−4 M, results could be explained by a single, active-uptake system with high affinity (Km = 4.6 × 10−5 M) and low capacity (Vmax = 5 nmol h−1 106 cells−1). Above 5 × 10−4 M, uptake was greater and could no longer be explained by the high-affinity system. A progressively greater uptake component appeared which was unaffected by metabolic inhibitors, 2,4-dinitrophenol and sodium azide, and by low temperature (2.5 °C). After subtraction of this so-called diffusional component from uptake kinetic data, a low-affinity (Km = 8 × 10−3 M), high-capacity (Vmax = 154 nmol h−1 106 cells−1), active-uptake system remained at high alanine concentrations.Uptake of alanine in these cells could be accounted for at low physiological concentrations by a single, monophasic system. Additional uptake at higher concentrations could be explained by other systems already demonstrated in these cells which are not specific for alanine, but which are, on the basis of competitive inhibition, capable of transporting it, and by a component which is probably diffusional in nature.
Photosynthesis and assimilate distribution in relation to yield of cassava grown in controlled environments
Authors: Mahon J. D. , Lowe S. B. , Hunt L. A.
Published: September 2008

Cassava (Manihot esculenta Crantz) plants were grown for 52 weeks in controlled-environment growth rooms with day/night (14/10 h) temperatures of 29/24 °C and 24/19 °C. Plants were sampled for growth analysis at monthly intervals for 36 weeks and at 52 weeks. At intervals the photosynthetic CO2 uptake by leaf parts and the respiration were measured in situ by using infrared CO2 analysis.The growth rate at both temperatures was directly related to the product of leaf photosynthesis and total leaf area, and the decreasing net assimilation rate of the high-temperature plants was reflected in the declining mean photosynthetic rates of the leaf tissue. The rate of photosynthetic CO2 uptake was between 9 and 18 mg dm−2 h−1, depending on leaf position.During the early stages of growth, the relationship between root weight and total weight was unaffected by temperature. As the plants increased in size, the proportion of dry matter in the roots increased in low-temperature plants but remained constant in high-temperature plants. The estimated plant respiration averaged 45% of the total assimilation. In high-temperature plants the root respiration was equivalent to 0.7% of the root dry weight per day and after 36 weeks the total root respiration exceeded the root growth.
Comparative CO2 exchange patterns in mosses from two tundra habitats at Barrow, Alaska
Authors: Oechel Walter C. , Collins Nigel J.
Published: September 2008

The effects of variation in light intensity, temperature, and water content on rates of net photosynthesis and dark respiration have been investigated in two common tundra mosses, Polytrichum alpinum from drier habitats and Calliergon sarmentosum from wetter habitats at Barrow, Alaska. Optimum temperatures for net photosynthesis of 10–15 °C for both species and saturating light intensities (photosynthetically active radiation (PhAR), 400–700 nm) of about 0.12 cal cm−2 min−1 for P. alpinum and 0.15 cal cm−2 min−1 for C. sarmentosum correlate well with measurements of light intensity and moss tissue temperatures made over the season at the collection site. It is suggested that depressions in net photosynthetic rates around midday might be caused by supraoptimal temperatures and possibly supraoptimal light intensities. Calliergon sarmentosum, a semiaquatic species required a higher water content (about 450% dry weight) than P. alpinum (about 200%) to reach maximal rates of net photosynthesis. Mean maximal rates of net photosynthesis ranged from about 2.6 to 4.4 mg CO2 g−1 dry weight h−1 for P. alpinum and from about 1.5 to 3.0 mg CO2 g−1 dry weight h−1 for C. sarmentosum. Predictions of net annual production have been made for both species. Predicted levels of 171 g C m−2 per 50-day season for C. sarmentosum compare well with results obtained for species of similar growth form elsewhere in polar regions. For P. alpinum the predicted level of 38.5 g C m−2 per 50-day season compares with observed dry matter production at the same site of 43 g m−2 per season.
Miscellaneous microfungi. I.
Authors: Raj T. R. Nag
Published: September 2008

Coniella eucalypticola sp. nov. and Thozetella canadensis sp. nov. are described. Hyalotiopsis borassi Thaung is excluded from Hyalotiopsis Punith. and accommodated in Parahyalotiopsis gen. nov.
Hypoxylon mammatum ascospore germination and mycelial growth on bark and wood media from young branches of trembling aspen
Authors: French J. R. , Manion P. D.
Published: September 2008

Hypoxylon mammatum radial growth rates increased with increasing concentrations of propylene-oxide-sterilized bark or wood tissue from fourth-season branches as sole nutrient source in agar media. Assay of bark and wood of one- to three-season-old branches demonstrated clonal and seasonal variation in growth-promoting and spore-germination-inhibiting factors.
Plant distribution in Newfoundland especially in relation to summer temperatures measured with the sucrose inversion method
Authors: Damman A. W. H.
Published: September 2008

Inadequate climatic data for large parts of Newfoundland hamper detailed analysis of factors controlling species distribution. Average temperatures for the vegetative season were measured over most of Newfoundland, using the sucrose inversion method. On this basis the coldest and warmest areas could be pinpointed, and regional differences could be mapped in considerable detail. The southern and eastern coastal areas are as cold or colder than the highest peaks except those of the Northern Peninsula. Highest average temperatures were recorded in the valleys of southwestern Newfoundland.Four groups of arctic–alpine species could be recognized which show clear geographic patterns controlled by climate; they include species (1) tolerating high summer maxima, (2) limited by high summer temperatures, (3) requiring deep winter snow cover, and (4) restricted to areas without frequent winter thaws.Deciduous forest species reaching Newfoundland occur in areas with highest average summer temperatures. The abrupt floristic changes in the southern part of the Northern Peninsula appear to be controlled primarily by length of vegetative season. In contrast, Alnus rugosa is limited by low summer temperatures and shows clear distributional limits in the northern as well as southeastern parts of the island.
Xylem in galls of lodgepole pine caused by western gall rust, Endocronartium harknessii
Authors: Zalasky Harry
Published: September 2008

Xylem in galls of lodgepole pine (P. contorta var. latifolia) caused by Endocronartium harknessii consists of unusually short, hyperplastic and hypoplastic aggregates of tracheids. The member pairs have random branching, shapes, and sizes. Some pairs and individual members or portions of them are atrophied in the early stage of differentiation. Others appear as strand tracheids. Ray crossings and coiled and reticulate patterns of aggregation in tracheids indicate that ray parenchyma fill multidirectional spaces and fan out spirally from a central point in the wood. The expanded rays consisting of isodiametric and cylindric ray parenchyma, and ray tracheids are connected to randomly spaced pit members at ray crossings that feature variable shapes and sizes of pit canals and chambers. The structure of the galls has many features in common with frost burls and frost ribs, i.e. chimeral nature, nodulations, abundance of rays, and hyperplastic and hypoplastic tissues.
Determination of copper, iron, nickel, and sulphur by X-ray fluorescence in lichens from the Mackenzie Valley, Northwest Territories, and the Sudbury District, Ontario
Authors: Tomassini F. D. , Puckett K. J. , Nieboer E. , Richardson D. H. S. , Grace B.
Published: September 2008

X-ray fluorescence was adapted to the analysis of 22 terricolous lichen species from 14 sites in the Mackenzie Valley, Northwest Territories, and 7 species from the Sudbury District of Northern Ontario. X-ray fluorescence (XRF) proved to be faster and exhibited better sensitivity and reproducibility than conventional analytical techniques; also, the samples were not destroyed in the analysis. Procedural details of the XRF method are given. The levels of copper, iron, nickel, and sulphur in Arctic lichens were similar to those found in lichens growing on the periphery of the Sudbury pollution zone but very much lower than in specimens nearer the nickel smelter. A linear relationship between concentration and the reciprocal of the distance from the Copper Cliff smelter was confirmed for the occurrence of these four elements in samples collected along a 60-mi NNW transect.
Anther and pollen infection in relation to the pollen and seed transmissibility of two strains of barley stripe mosaic virus in barley
Authors: Carroll Thomas W. , Mayhew Dennis E.
Published: September 2008

Anther and pollen infection in relation to seed and pollen transmission were studied for two different strains of barley stripe mosaic virus in 'Atlas' barley. Examination of sectioned anthers and pollen revealed that the seed- and pollen-transmitted isolate of the virus (MI-1) invaded the floral meristem of the host early and subsequently infected the pollen mother cells and sperms. During the premeiotic and meiotic stages of anther and pollen development, most virions of MI-1 were seen attached to microtubules, including those of the spindle. In later stages, the association of virions with microtubules diminished. Usually, MI-1 caused no apparent interference with normal mitosis and meiosis during development of anthers and pollen in central florets. Occasionally, however, the virus induced degeneration in anther and pollen-precursor cells before and during meiosis. By comparison, virions of the NSP strain, a strain which is not seed or pollen transmitted, could only be detected in wall cells of a single mature anther. None were discovered in the floral meristem or in pollen. It was also shown with unsectioned material that infection with either virus adversely affected anther and pollen development and that infection by MI-1 increased seed sterility.
Investigation of a non-nodulating cultivar of Pisum sativum
Authors: Degenhardt T. L. , Larue T. A. , Paul E. A.
Published: September 2008

A non-nodulating cultivar of Pisum sativum cv. Afghanistan was studied to characterize the nature and location of the non-nodulating factor. Nodule formation was not temperature sensitive. Rhizobium leguminosarum could exist in the rhizosphere. Root secretions did not decrease nodulation in adjacent normal plants, nor did the proximity of normal plants promote nodulation. Infection threads formed in the root hairs, but nodules were not formed. The infection process apparently aborted, resulting in the formation of swellings on areas of the root where nodulation would normally occur. Grafting experiments indicate that the factor preventing nodulation is in the root and is not translocated from the cotyledon or plant top.
Light and electron microscope studies of cytoplasmic aggregates formed in barley cells in response to Erysiphe graminis
Authors: Bushnell W. R. , Zeyen R. J.
Published: September 2008

Cytoplasmic aggregates that formed in susceptible barley epidermal cells 11-12 h after inoculation with Erysiphe graminis were examined by light microscopy in living specimens and by electron microscopy in fixed specimens. Rapid development of the aggregate (5–10 min) suggested that cytoplasm migrated to the site of each aggregation. The aggregate contained features generally associated with areas of high metabolic and synthetic activity: abundant mitochondria, rough endoplasmic reticulum (associated with smooth cisternae), Golgi bodies, and polyribosomes. Leucoplasts and nuclei were sometimes near aggregates but not consistently. Microbodies and osmiophilic spherosomes were not present.
Inheritance of virulence in Puccinia recondita on six backcross lines of wheat with single genes for resistance to leaf rust
Authors: Samborski D. J. , Dyck P. L.
Published: September 2008

The inheritance of virulence on six backcross lines with genes for resistance to leaf rust (P. recondita Rob. ex Desm.) was investigated using cultures obtained from selfing race 11 and, in some cases, F1 cultures of race 9 × race 11 and race 11 × race 161 and F1 and F2 cultures of race 9 × race 161. Race 11 was heterozygous for recessive genes for virulence on Thatcher*6/Kenya W1483 (Lr15), Lee FL310/6*Thatcher (Lr23), Thatcher*6/Terenzio, Thatcher*6/El Gaucho and for a dominant gene on Thatcher*6/Carina (LrB) and homozygous virulent on Thatcher*6/Exchange. On the basis of the F1 hybrid cultures, race 9 was homozygous for virulence on Lr15 and Thatcher*6/Exchange and homozygous for a virulence on Lr23 and LrB; while race 161 was homozygous for virulence on Lr15 and heterozygous for virulence on Lr23, Thatcher*6/Exchange, and possibly LrB.The rust cultures used in the present study were used in previous virulence inheritance studies on host genes Lr1, Lr2, Lr3, Lr3ka, Lr14a, Lr14b, and Lr17. Virulence on Lr3ka was linked with virulence on Thatcher*6/Terenzio (3.7 ± 1.93%) and virulence on Lr3 with virulence on Lr14a (3.9 ± 1.62%); all others were independent.
Membrane polypeptides and chlorophyll–protein complexes of maize mesophyll chloroplasts
Authors: Hayden D. B. , Hopkins W. G.
Published: September 2008

Polypeptide profiles of maize mesophyll chloroplast lamellae have been obtained using SDS – acrylamide gel electrophoresis. Molecular weights have been assigned to the major polypeptides using the same technique. Chlorophyll–protein complexes from lamellae have been resolved using both SDS – acrylamide gel electrophoresis and chromatography on hydroxylapatite. Chlorophyll a alone is associated with a 69-kilodalton polypeptide while both chlorophylls a and b are associated with a 23-kilodalton component.
Bryophytes of Cataracts Provincial Park, Newfoundland: ecology and phytogeography
Authors: Weber David P. , Brassard Guy R.
Published: September 2008

Bryological knowledge of insular Newfoundland has been significantly augmented by an intensive investigation of the mosses and liverworts of Cataracts Provincial Park. The study area (13 ha) included forest, bog, heath, and a deep, narrow, and angular river gorge and waterfalls, which provide numerous microhabitats particularly suitable for bryophytes. The bryophyte habitats are described, and a list of species gives data on occurrence, frequency, and fertility. Within the study area 121 species of mosses and 63 species of liverworts were collected, which represent 35% of the known bryoflora of the island of Newfoundland. Bryum creberrimum, Cephaloziella hampeana, and Ditrichum lineare are additions to the bryoflora of insular Newfoundland. The ranges of several predominantly calciphilic bryophytes, previously thought to be more or less restricted in Newfoundland to the more calcareous western regions, have been extended to southeastern Newfoundland (Avalon Peninsula). A small southern element and a small northern element, represented by Sematophyllum marylandicum and Lophozia bantriensis, respectively, are present within the Park, but most of the bryophyte species there are typical circumboreal species.
Grass cuticles: a new paleoecological tool for East African lake sediments
Authors: Palmer Patricia G.
Published: September 2008

Reconstruction of past vegetation in grassy environments of tropical Africa is hindered by the indistinguishability of grass pollen grains. For these regions, it is necessary to use other fossil material (e.g. grass leaf fragments) to obtain additional paleoecological data. Since many core samples from East African lakes are rich in cuticular fragments of grasses, the identification of these fragments can provide paleobotanical information to complement pollen studies. Light microscopy and scanning electron microscopy are used to identify fossil cuticles to the level of subfamily, tribe, or genus. This new technique provides a much-needed source of information for reconstructing the past vegetation and past climate of regions where grasses are important elements in the fossil records.
Prothallal lichen substances in two species of crustose lichens, Fuscidea cyathoides and Rhizocarpon geographicum
Authors: Fahselt Dianne
Published: September 2008

Lichen substances in the prothallus of two species of crustose lichens, Fuscidea cyathoides (Ach.)Wirth and Rhizocarpon geographicum (L.)DC., were compared with those in the primary thallus. Quantification was accomplished using thin-layer chromatography and microdensitometry. In both species, at least some of the prothallal tissue, although it consisted only of fungal hyphae, contained the same lichen substances as the main part of the thallus. The quantities present in the prothallus, however, were lower, especially in the case of R. geographicum, where there was no more than about 5% as much psoromic acid per unit dry weight of prothallus as of areoles. In scanning electron micrographs the extrahyphal depositions present in prothalli appeared similar to those in the medullary regions of the primary thallus, but in R. geographicum they were noticeably less copious. The possibility that lichen substances could migrate within the thallus is discussed.
Notes sur l'écologie de trois espèces ligneuses à la bordure méridionale de la baie d'Ungava, Nouveau-Québec : Betula glandulosa, Larix laricina, Picea mariana
Authors: Ducruc J. P. , Zarnovican R.
Published: September 2008

not available
Apothecial development and sexuality in Ascobolus sacchariferus
Authors: Paden John W. , Linton M. A. Susan
Published: September 2008

Sexuality and apothecial ontogeny in the operculate Discomycete Ascobolus sacchariferus (Ascomycetes, Pezizales) were investigated. Ascobolus sacchariferus is heterothallic and produces oidia that can function as vegetative propagules or as gametes. When oidia are contrasted with mycelia in either a compatible or incompatible cross, they fail to germinate. In a compatible cross the oidia are changed physiologically into functional antheridia and attract hyphae of the opposite mating type, which then delimit ascogonia. The ascogonia are blunt-ended, without a differentiated trichogyne, and coil around the oidia. Some strains were found to be stronger males, others stronger females. After plasmogamy, apothecial development is cleistohymenial. Opening of most apothecia occurs in the midmesohymenial phase. After opening, ripe asci protrude from the hymenial surface. Attempts to hybridize A. sacchariferus and A. sterocorarius yielded negative results. The two species, however, inhibit the germination of each other's oidia.
The late-Quaternary vegetational history of the Western Interior of Canada
Authors: Ritchie J. C.
Published: September 2008

The late-Wisconsinan pollen stratigraphy of the Western Interior of Canada is assembled and 16 representative sites provide a basis for establishing trends of vegetation history. Sites in the southern, prairie region show an early Picea–Artemisia assemblage (12 × 103 to 10 × 103) replaced by a zone dominated by herb pollen. Similarly, sites in the Aspen Parkland and Transitional zones all have the Picea–Artemisia zone from as early as 13.9 × 103 to 10 × 103, followed by a herb zone. It is replaced by an arboreal pollen zone at 4.5 × 103 to 3 × 103 B.P. While there is a broad trend common to all sites in the modern boreal forest, from an early spruce-dominated assemblage to a late postglacial spruce–pine–birch assemblage identical with modern spectra, there are differences in the details of stratigraphy. Two sites in central Alberta have a poplar zone preceding the early spruce zone. Sites near the modern southern forest boundary show a late development (3 × 103 B.P.) of the mixed boreal forest from prairie and hardwood deciduous forest communities. One site, at Flin Flon, Saskatchewan, provides clear evidence for a treeless episode (Artemisia–grass–sedge) preceding the spruce zone.As the late-Wisconsinan glacial ended, an early version of the boreal forest, dominated by spruce and lacking pine, spread from adjacent U.S. on to deglaciated surfaces and till over stagnant ice. It persisted in the southern part of the area until about 10 × 103 and until 6 × 103 in the northernmost portions. In the south the spruce forest was replaced directly by prairie, spreading from the southwest and extending farther north than its modern limit between 7.5 × 103 and 6 × 103. All remnants of ice sheets and glacial lakes had disappeared by about 7 × 103 and the northern part of the area was occupied by a boreal forest undergoing rapid changes in composition from the early spruce-dominated version to the mixed spruce–pine–birch–poplar mosaic prevalent today. Pine probably spread from western réfugia, at least into areas north and west of L. Winnipeg. At about 3 × 103 the southern limit of the forest extended to the south, apparently in response to a climate with cooler and (or) wetter growing seasons. The rapid replacement of the spruce-dominated boreal forest by grasslands in the early postglacial was probably a response to warmer and drier growing seasons.
Physiology and plastid fine structure of deetiolating Lemna minor
Authors: Frick Hugh , Jones Raymond F.
Published: September 2008

During the 12-h lag period in chlorophyll accumulation after the onset of white-light illumination of Lemna minor etiolated for 35 days, a rapid increase in visible fronds per culture occurred. This new frond production then assumed a log-linear rate of increase, and total protein per unit fresh weight came to parallel the rate of increase in fresh weight per plant. The ribosomal RNA content of 45-day-etiolated plants was deficient in 23S and 16S species compared with green plants. The prolamellar bodies of etioplasts were either tightly or loosely paracrystalline within the same cell; they were without extended perforate lamellae, which developed during far-red-light illumination even while prolamellar bodies persisted. The development of chloroplasts in deetiolating L. minor was typical of other higher plants. The developmental sequence in green Lemna included proplastid to deeply stacked granal chloroplast within several millimetres. Plastid profiles suggestive of division configurations occurred only in primordial cells of green and etiolated plants. The relatively small numbers of plastids in any given stage of differentiation may account for the sensitivity of plastid development to inhibitors of protein and nucleic acid synthesis.
The effect of 2,4-D and kinetin on the morphology, growth, and cytochemistry of peroxidase of cotyledon cell suspension cultures of bush bean (Phaseolus vulgaris cv. Contender)
Authors: Arnison Paul G. , Boll W. G.
Published: September 2008

Cotyledon cell suspension cultures of Phaseolus vulgaris were grown in the presence and absence of the growth regulators (2,4-dichlorophenoxy)acetic acid (2,4-D) and kinetin. Omission of the regulators changed the growth and cell division and produced striking changes in morphological characteristics. Cytochemical studies of peroxidase activity showed that the enzymes were mainly cytoplasmic in young cells and mainly associated with wall in older cells. No apparent differences in localization of activity were detected between the treatments, but cells cultured without the regulators showed a much more intense enzyme reaction. The location and increase of peroxidase, with increasing cell age and cell complexity, are consistent with the view that peroxidase activity is involved in cell wall expansion and differentiation.
The effect of 2,4-D and kinetin on peroxidase activity and isoenzyme pattern in cotyledon cell suspension cultures of bush bean (Phaseolus vulgaris cv. Contender)
Authors: Arnison Paul G. , Boll W. G.
Published: September 2008

Cotyledon cell suspension cultures of Phaseolus vulgaris were grown in the presence and absence of the growth regulators (2,4-dichlorophenoxy)acetic acid (2,4-D) and kinetin. Peroxidase (EC 1.11.1.7) activity was at a minimum during the phase of cell division and at a maximum during the phase of cell expansion. Both the pattern and activity of peroxidase isoenzymes changed during the culture cycle.Cells cultured without growth regulators showed increased peroxidase activity and changed isoenzyme patterns. Certain peroxidase isoenzymes were only present or prominent during specific phases of the culture cycle.The electrophoretic mobilities of peroxidase isoenzymes detected in the medium were not the same as those of the cytoplasmic isoenzymes. Cell cultures grown with and without growth regulators showed different patterns of medium peroxidase activity.Results are discussed in relation to the correlation of peroxidase activity with cell wall expansion and the possible role of peroxidase in cell growth and differentiation.
Morphological characters, relative to distribution, and taxonomic considerations of the genus Climacium in North America
Authors: Horton Diana G. , Vitt Dale H.
Published: September 2008

A quantitative and qualitative analysis of Climacium americanum and C. dendroides in North America confirms that these two taxa are distinct, although there is limited morphological intergradation in the region of the Great Lakes eastward to the coast. Climacium americanum has branch leaf upper cell length-to-width ratios of 3–7(8): 1, branch leaf auricles generally larger, stem leaf apices acuminate, and capsules symmetric, 3.0–6.0 mm long; while C. dendroides has branch leaf upper cell length to width ratios of (6)7–13:1, branch leaf auricles generally smaller, stem leaf apices obtuse and apiculate, and capsules usually asymmetric, 1.5–4.0 mm long. Climacium americanum is endemic to southeastern North America, while C. dendroides is western and boreal in distribution. It is hypothesized that the endemic C. americanum arose in isolation from the circumboreal C. dendroides. Upon retreat of Pleistocene glaciers, geographical intermingling of the two species resulted in limited morphological intergradation in southeastern Canada and northeastern United States. Climacium kindbergii is considered to be taxonomically synonymous with C. americanum, while C. novae-seelandiae is regarded as taxonomically synonymous with C. dendroides. Climacium japonicum is a distinct species characterized by a few large teeth on the abaxial surface of the costa of branch leaves.
Comparative studies of activity and properties of ferredoxin–NADP+ reductase during cold hardening of wheat
Authors: Riov Joseph , Brown Gregory N.
Published: September 2008

Activity and properties of chloroplast ferredoxin–NADP− reductase (EC 1.6.7.1) were studied during cold hardening of two varieties of wheat (Triticum aestivnm), hardy Kharkov (winter wheat) and much less hardy Rescue (spring wheat), to determine whether adaptation to low temperatures involves changes in the activity and properties of this enzyme. Specific activity of ferredoxin–NADP− reductase increased during hardening of both varieties, but the increase was much greater in the more hardy variety, Kharkov 22 MC. No changes were found in the Michaelis constants for NADPH and 2,6-dichlorophenol indophenol, activation energy values, inhibition constants for p-chloromercuriphenylsulfonate, and sensitivity toward cold and heat inactivation of the enzyme from control and cold-hardened seedlings of both varieties. The data suggest that there is a preferential synthesis of ferredoxin–NADP− reductase during hardening of wheat, but the enzyme molecule remains unchanged.
Anatomical changes in the secondary phloem of grand fir (Abies grandis) induced by the balsam woolly aphid (Adelges piceae)
Authors: Saigo Roy H.
Published: September 2008

This study examines the microscopic anatomy and seasonal changes of the secondary phloem, cambium, and a portion of the xylem of grand fir trees (Abies grandis [Dougl.] Lindl.) infested with the balsam woolly aphid (Adelges piceae Ratz.) as compared with tissues of non-infested trees.The reactivation of the vascular cambium and production of astrosclereids and resin cells are about the same in infested and non-infested trees.The infested trees exhibit sieve cells that are shorter in length, having a tangential dimension about the same as normal cells, and produce more tangential bands of phloem parenchyma cells, more fiber sclereids, biseriate rays, and lipoidal-filled ray cells, abnormally shaped ray parenchyma cell nuclei, giant cortical parenchyma cells, and traumatic resin ducts in the xylem.
Chemosystematic studies in the genus Abies. II. Leaf oil analysis of grand fir
Authors: Rudloff E. von
Published: September 2008

The volatile leaf oil of the grand fir consists mainly of (−)-α-pinene, (−)-camphene, (−)-β-pinene, (−)-β-phellandrene, (−)-bornyl acetate, cadinene and muurolene isomers, and two cubebol isomers. Santene, tricyclene, myrcene, car-3-ene, limonene, terpinolene, p-cymene, camphenolene aldehyde, camphor, borneol, terpinen-4-ol, α-terpineol, citronellyl and geranyl acetate, α-cubebene, α-copaene, calamenene, and two farnesol isomers were also isolated. Attempts to identify these terpenes with a combined gas chromatograph – mass spectrometer failed to give unequivocal data and identities had to be confirmed by isolation and recording of other spectra. Except for β-pinene and β-phellandrene, within-tree and tree-to-tree variation of terpene percentages was relatively small. The leaf oil terpene composition appears to be well suited to determine geographical variation. Only minor differences were recorded between some northern coastal and interior populations, but samples from south-central Oregon showed major differences that are indicative of introgression with white fir.
Conimitella (Saxifragaceae) and its rust
Authors: Savile D. B. O.
Published: September 2008

A rust found on Conimitella williamsii in southwest Alberta and central Colorado is referable to Puccinia saxifragae var. heucherarum. Morphology and the rust relationship suggest that Conimitella diverged from a moderately advanced Heuchera.
Zoospore ultrastructure of three Chytridium species and Rhizoclosmatium globosum
Authors: Barr D. J. S. , Hartmann V. E.
Published: September 2008

Zoospore cytology of Chytridium lagenaria Schenk, C. confervae (Wille) Minden, C. olla Braun, and Rhizoclosmatium globosum H. E. Petersen is described. Zoospores of C. confervae, C. olla, and R. globosum have many ultrastructural characteristics in common and, considered of particular significance, show similarities in the basal area by the kinetosome; here two sets of three electron-dense, stacked, plate-like bodies are on the side of the kinetosome opposite to a parallel, non-functional centriole. Zoospores of C. lagenaria instead of having plate-like bodies have an electron-dense, half-saddle-shape structure partially covering the kinetosome. The position of certain organelles in C. lagenaria further distinguishes it from the other three species. Zoospores of all four species have a membrane-bound cluster of ribosomes, usually a single lipid body with a rumposome and microbody in association with it, a bundle of microtubules which connect the rumposome and kinetosome, and, in the peripheral area, a striated (paracrystalline) inclusion. Comparison with other chytrids is made and taxonomic implications are discussed.
Ultrastructural effects and translocation of methyl-2-(4-(2,4-dichlorophenoxy)-phenoxy)propanoate in wheat (Triticum aestivum) and wild oat (Avena fatua)
Authors: Brezeanu A. G. , Davis D. G. , Shimabukuro R. H.
Published: September 2008

Ultrastructural effects, absorption, and translocation of the experimental compound methyl-2-(4-(2,4-dichlorophenoxy)phenoxy)propanoate (MPP), topically applied to resistant wheat (Triticum aestivum L.) and susceptible wild oat (Avena fatua L.), were studied.The two species were affected differently by MPP when greenhouse-grown seedlings were treated at the [Formula: see text]-leaf stage. The second leaf of both species was damaged, but wild oat leaves were affected much more than wheat leaves. Although tissues formed after treatment and the apical region of the second leaf of wheat did not appear to be injured, ultrastructural modifications occurred. In wild oat, both visible injury and ultrastructural modifications were seen. Chloroplasts were the organelles most affected by the compound in both species. Cellular alterations ranging from slight to complete destruction of the cytoplasm were observed in cells of treated leaves. Frequently cells with undamaged chloroplasts were located next to cells with damaged chloroplasts. The translocation patterns of [14C]MPP applied as a drop were similar in wheat and wild oat and could not account for the differences in their sensitivities. About 95% of the 14C was recovered in the region of application in both species.
Excipuloid stroma ontogeny in Peziza quelepidotia
Authors: O'donnell K. L. , Hooper G. R.
Published: September 2008

Excipuloid stroma ontogeny in Peziza quelepidotia Korf & O'Donnell was investigated. The scanning electron microscope was used to examine whole specimens from the initials up to maturity. In addition, the internal features of cryofractured, critical-point-dried stroma of various stages were investigated and compared with thick-sectioned, plastic-embedded material viewed in the light microscope. A comparison of these indeterminate vegetative structures with stroma and sclerotia was made.
Apothecial ontogeny in Saccobolus versicolor (Pezizales: Ascomycetes)
Authors: O'Donnell K. L. , Fields W. G. , Hooper G. R.
Published: September 2008

Apothecial ontogeny in Saccobolus versicolor was followed by scanning electron and light microscopy from ascogonial coil initiation through spore discharge. Several slender, recurved branches functioned as ascogonia and initiated apothecium formation. Since antheridia were never observed, development was assumed to be parthenogenetic. Soon after ascogonia appeared, slender investing hyphae grew up from nearby vegetative hyphae and from the ascogonium. Subsequently, the basal cells in the ascogonia greatly increased in diameter and their septa broke down. Apothecium ontogeny was either eugymnohymenial with a poorly developed ectal excipulum or paragymnohymenial opening in the prehymenial phase. As a result of the presence of several functional ascogonia, asci developed by typical crozier formation and exhibited a strong positive phototrophic response as they protruded before spore discharge.