bluuebunny/crossref_metadata_2025 huggingface dataset:
The decomposition of standing and fallen litter of Typha glauca and Scirpus fluviatilis
Authors: Davis C. B. , Valk A. G. van der
Published: May 2008

Changes in dry weight and N, P, K, Na, Ca, Mg, Al, and Fe content were studied over a 525-day period in decomposing Typha glauca and Scirpus fluviatilis shoots. Submerged Typha litter decomposed more rapidly than submerged Scirpus litter, losing 50% of its original dry weight in 325 days while Scirpus litter still retained 62% of its original dry weight after 525 days. Major pathways of mineral flow from standing litter were (1) leaching during the first few weeks after shoot death and (2) fragmentation and litter fall during the rest of the study. Mineral losses from fallen litter were mainly due to leaching or to excretion by microbial populations associated with the litter. Microbial uptake (N, P) and adsorption (Ca, Al, Fe) were important processes in the fallen litter. After 525 days, as a result of the combined action of mineral uptake and release, Typha litter had net releases of N (71 kg/ha), P(10 kg/ha), K (123 kg/ha), Na (94 kg/ha), Ca (41 kg/ha), and Mg (25 kg/ha) and net accumulations of Al (21 kg/ha) and Fe (20 kg/ha). Scirpus litter, during this same period, had net releases of N (10 kg/ha), K (9 kg/ha), and Na (11 kg/ha). All other minerals increased in decomposing Scirpus litter: P (8 kg/ha), Ca (55 kg/ha), Mg (5 kg/ha), Al (13 kg/ha), and Fe (11 kg/ha). At the end of the study, the calculated combined dry weight of undecomposed standing and fallen litter had decreased by only 20% in Typha litter and 14% in Scirpus litter. Most of the biomass and minerals were in the fallen litter.
Sorbitol and proline as intracellular osmotic solutes in the green alga Stichococcus bacillaris
Authors: Brown Lewis M. , Hellebust Johan A.
Published: May 2008

A freshwater isolate of Stichococcus bacillaris Naeg. (strain UTEX 314) was evaluated for its ability to grow, photosynthesize, and osmoregulate over a wide range of salinity. The growth and photosynthetic measurements indicate that it is a euryhaline organism. Studies of the soluble organic metabolite pools showed that the steady-state levels of two solutes varied with salinity; sorbitol (a polyol) and proline (an amino acid). Intracellular proline levels increased from 0.002 to 0.28 M over the salinity range of 0 to40%c whereas the sorbitol level increased from 0.10 to 0.52 M. The level of total amino acids (excepting proline) remained relatively constant. No single amino acid of this group exceeded an intracellular concentration of 0.04 M. The changes in the concentrations of these solutes accounted for at least 75% of the required increase in intracellular osmolality in cells following adaptation to high salinity media. Sorbitol and proline are very soluble, nontoxic, and are efficient osmotic solutes. These properties make them ideal solutes for osmoregulation.
Effect of shoot decapitation on the translocation of 2,4-D in Cirsium arvense
Authors: McIntyre G. I. , Fleming W. W. , Hunter J. H.
Published: May 2008

When 14C-labelled 2,4-D [(2,4-dichlorophenoxy)acetic acid] was applied to the basal leaves of Canada thistle (Cirsium arvense L.), prior removal of approximately the upper two-thirds of the flowering shoot resulted in a 20 to 30% increase in total 14C exported from the treated leaves and a twofold to threefold increase in the amount in the roots. Removing only the apical region of the shoot had the opposite effect, markedly reducing 14C export from the treated leaves and translocation to the roots. Provision of a higher N level more than doubled 14C translocation from the treated leaves and caused a threefold increase in 14C content of the roots of undecapitated plants. The reduction in basipetal transport produced by apical decapitation was attributed to the inhibiting influence of subapical lateral shoots on basal branching and root bud growth. When apical decapitation was combined with removal of the axillary buds in the subapical region, basal branching and root bud growth were promoted and 14C translocation into the roots was significantly increased.
Potential for natural hybridization between strains of Ustilago nuda
Authors: Thomas P. L.
Published: May 2008

Hybridization of gametes produced by different teliospores of Ustilago nuda (Jens) Rostr. was demonstrated to occur within the host. Confirmation that a host plant is usually infected by only a single dikaryon permitted the sampling of sori as presumptive hybrids. The detection of hybrids relied upon the use of two strains of smut that differed in teliospore color and virulence on a range of host cultivars. The potential for hybridization was calculated to be as much as 43% of the amount expected from random mating between the gametes produced by teliospores in the florets of barley.
Alpha and beta spore occurrence in Phomopsis juniperovora pycnidia on Juniperus virginiana and in culture
Authors: Otta J. D.
Published: May 2008

Pycnidia of Phomopsis juniperovora on Juniperus virginiana were examined for occurrence of beta spores. Beta spores were observed in only 3% of the pycnidia on diseased material collected in the field. The most beta spores observed in one pycnidium was four. Thirty-two percent of the pycnidia produced after diseased material was collected contained beta spores. The beta spore content in induced pycnidia ranged from 0 to 85% of the spores observed. The pycnidia observed from cultures on potato dextrose agar contained between 15 and 98% beta spores. The absence of beta spores in pycnidia on field-collected material hinders proper diagnosis of the causal organism.
Cyathus pedicellatus, a new species of the Nidulariaceae from Colombia
Authors: Brodie Harold J.
Published: May 2008

Cyathus pedicellatus sp.nov. (Nidulariaceae) is a large, dark brown, deeply plicate species readily distinguished from all others because the cupulate portion of the peridium is attached to the emplacement by a conspicuous dark-coloured pedicel of firm texture. This Cyathus from Colombia is closely related taxonomically to C. limbatus Tul.
Ultrastructure of the dormant and germinating sporangiospore of Phascolomyces articulosus (Mucorales)
Authors: Jeffries P. , Young T. W. K.
Published: May 2008

Using results obtained with light and scanning electron microscopy of critical-point-dried material and transmission electron microscopy of carbon replicas and freeze-fracture and ultra-thin sections, the structure and germination of the sporangiospore of Phascolomyces articulosus Boedijn is described. The sporangial wall is trilaminate and the ornamented spore wall is two layered. During germination, a new wall layer develops between the plasmalemma and the original spore wall. Sporangial structure is related to that of other members of the Thamnidiaceae and the use of germinating spores of P. articulosus for infection studies of the mycoparasite Piptocephalis unispora is indicated.
Meiotic nuclear behavior and ascospore formation in five homothallic species of Neurospora
Authors: Raju Namboori B.
Published: May 2008

Meiotic nuclear behavior and chromosome numbers have been examined, using a propionic–iron–hematoxylin staining method, in Neurospora crassa and in five homothallic species, N. africana, N. dodgei, N. galapagosensis, N. lineolata and N. tcrricola. Ascus development, haploid chromosome numbers (n = 7), and morphology in all five homothallic species resemble the heterothallic N. crassa. The following observations have not been reported previously for any Neurospora species, although some have been described in other fungi. Most observations apply to all five homothallic species and to N. crassa except where otherwise indicated. (1) Chromosomes elongate considerably between karyogamy and the beginning of synapsis, and leptotene and zygotene stages can be identified. (2) The ascus tip flattens, and an apical pore begins to form during diplotene. (3) After telophase III, when all eight nuclei line up in single file, the nuclei are always arranged perpendicularly to the ascus wall with all spindle plaques on the same side. All nuclei then tilt relative to the ascus base with the spindle plaques at the lower end; consequently, the spores become obliquely arranged. (4) Ascospores of N. terricola are initially spindle shaped and occupy the entire ascus but later become compact and ovoid with spaces between them. (5) Maturing ascospores grow two to four times their initial compacted size. (6) In the young ascus, the nucleolus usually orients toward the base. (7) In N. terricola, the nucleolus is frequently hemispherical, especially in the young asci. (8) Half-moon-shaped polar caps are sometimes visible, one on each side of the prophase I nucleus; these are most prominent in N. terricola. (9) Cytological preparations are greatly improved if hydrolyzed perithecia are thoroughly washed in a Carnoy's solution containing chloroform.
Phosphate absorption by soybean varieties: the influence of ferulic acid
Authors: McClure Peter R. , Gross H. Douglass , Jackson William A.
Published: May 2008

The effect of ferulic acid upon phosphate absorption by excised and intact roots of three soybean (Glycine max (L.) Merrill) varieties (Hill, Ogden, and Jackson) was examined using 32P-labelled solutions. Kinetic analysis of the phosphate uptake rates of roots of 3-day-old seedlings showed that 0.5 and 1.0 mM ferulic acid inhibited the absorption of phosphate by each variety. This inhibition was noncompetitive; the presence of ferulic acid reduced the Vmax values of the absorption systems but did not alter the values of the apparent Km. No direct effect upon the translocation of absorbed phosphate was found in the intact seedlings.
Effect of buffered solutions and various anions on vegetative and sexual development in gametophytes of Pteridium aquilinum
Authors: Evans Lance S. , Bozzone Donna M.
Published: May 2008

Experiments were performed to determine the effects of chloride, nitrate, and sulfate in buffered solutions on sperm motility and fertilization in gametophytes of Pteridium aquilinum. Buffered solutions with various anions simulated exposures to acidic precipitation up to 3.5 h. The presence of each anion decreased both sperm motility and fertilization. Addition of 43.3 μM sulfate (equivalent to the sulfate concentration in rain of northeastern United States) decreased sperm motility about 40% compared with plants exposed to buffers without sulfate. Additions of 86.6 μM and 173.2 μM sulfate gave sperm motility levels of approximately 45% and 36% of sperm unexposed to sulfate. Percentage reduction in sperm motility during sulfate exposure was independent of buffer pH. Additions of chloride and nitrate at pH 4.8 gave sperm motility values similar to buffers with sulfate. However, at pH 5.8, chloride ions were less harmful than nitrate or sulfate. Addition of anions also had a detrimental effect on fertilization or production of sporophyte plants. In all experiments, the presence of chloride and nitrate alone or in combination with sulfate gave reductions in fertilization similar to that of sulfate alone at equivalent concentrations. Additions of one or more anions produced additive effects at all pH levels to reduce both sperm motility and fertilization in gametophytes of Pteridium aquilinum.
Cytochemical and ultrastructural peculiarities of embryogenic pollen grains and of young androgenic embryos in Datura innoxia
Authors: Sangwan-Norreel Brigitte S.
Published: May 2008

Cytochemical and ultrastructural studies of androgenic embryogenesis in Datura innoxia Mill. have been performed on (a) uncultured pollen grains collected at the stage favourable to embryo formation, i.e., at the time just before and just after the first haploid mitosis of the microspore nucleus (flower bud length of 4–5 cm); and (b) pollen grains and young androgenic embryos picked from the medium after 5, 9, and 11 days in culture.Only features presumed to play a role in the induction of androgenic embryogenesis are described.The phase of pollen development favourable to embryogenesis is very short but it involves important changes in the cytochemical features and in the ultrastructure of pollen grains. The changes are particularly clear in RNA and nucleohistone stainabilities and in the number and activity of the cytoplasmic organelles.It is suggested that it is not one particular metabolic or ultrastructural state of the cell which is responsible for the embryogenesis competence but that it is the fact that the changes occur which is important. Pollen which is in an unstable ultrastructural and metabolic state will be more sensitive to external stimuli.The study of very young androgenic embryos shows several features which are presumed to be responsible for the induction of embryogenesis: (a) Changes in cytoplasmic distribution and in nuclear organization consecutive to the first haploid mitosis in the microspore. These modifications sometimes lead to the formation of two equal pollen nuclei instead of differing vegetative and generative nuclei. The two identical nuclei are located in two equal-sized cells or in a single pollen cell. (b) Variations in pollen RNA content and in the organization of the endoplasmic reticulum which are related to changes in the pollen metabolism. (c) Modifications of the plasmalemma within pollen grains and of the cell wall surrounding the pollen grains. Such modifications are presumed to cause variations in the intercellular exchanges as well as in the exchanges between pollen and medium.
Nectar secretion in excised flowers. VI. Relationship of secretion to protein metabolism
Authors: Shuel R. W. , Tsao W.
Published: May 2008

The relationship of nectar secretion in snapdragon to protein metabolism, and the influence on both processes of indoleacetic acid (IAA) and to a lesser extent pollination, were both studied. Indoleacetic acid at 5 × 10−4 M appeared to initiate a reorganization in the nectary which led to the stimulation of growth and an early termination of secretion. Two hours after treatment began, incorporation of [14C]uracil into RNA was 60% higher than in controls. A twofold to threefold increase in protein synthesis from [14C]sucrose followed but with no increase and usually a reduction in total nectary protein, despite considerable enlargement of the nectary. These effects suggested a differential action of IAA on protein synthesis and an enhanced degradation of existing protein. Changes in RNA and protein gel electropherograms, and a lowering of the adsorptive capacity of protein in nectary homogenate for [14C]sucrose, were also noted. Actinomycin C, puromycin, and chloramphenicol, like IAA, strongly inhibited secretion but differed from IAA with respect to other effects. None stimulated nectary growth. Actinomycin inhibited synthesis of protein from [14C]sucrose. Puromycin and chloramphenicol increased the amount of protein synthesized from [14C]sucrose but reduced the total protein content. Changes in the nectary following pollination resembled those caused by IAA with respect to RNA and protein gel patterns, stimulation of growth, reduction in tissue protein concentration, and cessation of nectar secretion. It is possible, though not demonstrated, that termination of secretion by IAA and pollination was mediated by changes in proteins associated with sugar transport.
Variability of uredial cultures of Puccinia graminis tritici derived from 'vegetative' axenic mycelium
Authors: Green G. J. , Williams P. G. , Maclean D. J.
Published: May 2008

Two of 26 'vegetative' axenic cultures of Puccinia graminis tritici were induced to infect wheat by the epidermal stripping and mycelial implant technique. Only one of these two cultures produced urediospores and could be propagated on wheat. The urediospores obtained from implants had poor infectivity and there was a long incubation period. Single pustule isolates varied in growth rate, colour, virulence, sporulation, pustule type, and number of nuclei per spore. The uredial cultures comprised two groups: (1) one group with dikaryotic spores which resembled the parent culture race 126-Anz-6,7, Sydney University No. 334; (2) another group with monokaryotic spores which varied widely. The variability of the uredial cultures is interpreted as evidence that the diploid nucleus of the 'vegetative' axenic cultures originated by fusion of two haploid nuclei and divided in two ways: firstly, by a reduction division that produced two haploid nuclei and reconstituted a dikaryon similar to race 126-Anz-6,7, and secondly, by a mitotic division that produced diploids, variant aneuploids, and possibly mitotic recombinants.
The fine structure of ascus development in Lasiobolus monascus (Pezizales)
Authors: Kimbrough James W. , Benny Gerald L.
Published: May 2008

Ultrastructural and cytochemical studies on the ascus of Lasiobolus monascus are presented. Apothecia in various stages of development were obtained in culture and prepared for both light and electron microscopic observations. Ultrathin sections for electron microscopic inspection were often treated with silver methenamine to enhance wall characteristics. Ascus development was followed from fertilization to maturity.In this species, the ascogonium enlarges after fertilization to become the ascus mother cell. Two pores are present in the young ascus, one connecting it to the antheridium and another between the ascus and stalk cell. The ultrastructural features of these pores in the young and maturing ascus are described. During ascus enlargement, as many as four wall layers are found when poststained with silver methenamine. Only two layers are clearly distinguishable when poststained with uranyl acetate and lead citrate. The apical zone of dehiscence is characterized by a distinct annular swelling which appears during early ascosporogenesis. By spore maturation, this swelling is not evident either at the light or electron microscopic level. Instead, there appear to be both physical and chemical changes in the area of dehiscence. The wall is distinctly thinner and much more electron transparent in the area of dehiscence when treated with silver methanamine.
The comparative ecology and distribution and within-species variation of the lichenized Ascomycetes Ramalina cuspidata and R. siliquosa in the British Isles
Authors: Sheard J. W.
Published: May 2008

The two species are shown to be almost perfectly sympatric, but their centres of abundance on the shore are different, Ramalina cuspidata being most abundant low in the supralittoral and R. siliquosa most abundant higher in this zone. Principal component analyses show that the within-species variation, which is considerable, is continuous in both species. Correlation of the attribute scores and height above sea level of the individuals with the component scores for the individuals demonstrates that in R. cuspidata both morphological and chemical variation are related to vertical position on the shore. Only chemistry is related to vertical position in R. siliquosa, morphological variation being controlled by angle of rock surface and protection from inundation. The continuum of morphological variation is considered to be a response to a potential evapotranspiration gradient in both species. Individual ramuli of R. cuspidata frequently exhibit a wide range of the morphological continuum along their length indicating that morphological variation is not the result of genotype selection. There is no unequivocal evidence by which to refute the widely held view that the zonation of chemotypes in both species is the result of habitat selection. However, it now seems more probable that chemical variation may be explained as being the result of progressive truncation of biosynthetic pathways as a response to an increasingly stressful environment with increasing height above sea level. The concept of morphological buffering is introduced and the role of morphological plasticity in the survival strategy of lichens is discussed.
Effects of low concentrations of ethylene on cell division and cytodifferentiation in lettuce pith expiants
Authors: Zobel Richard W. , Roberts Lorin W.
Published: May 2008

The initiation of callus and tracheids from lettuce pith explants is inhibited when initial ethylene levels are above 100 nl/ℓ. When initial ethylene levels were near 2 nl/ℓ, lettuce pith explants cultured in small continuously sealed vials demonstrated no reduction in callus development compared with controls, but unlike the controls, they demonstrated no tracheid development. An hypothesis is advanced that ethylene has little effect on cell division per se, but at concentrations in excess of 100 nl/ℓ, it may inhibit the cytodifferentiative events leading to callus production and (or) tracheid development in lettuce pith explants.
Modern diatom assemblages from lake sediments in the boreal–arctic transition region near the Mackenzie Delta, N.W.T., Canada
Authors: Koivo L. K. , Ritchie J. C.
Published: May 2008

Surface lake mud samples from 20 lake sites across the transition from northern boreal forest to tundra, near the Mackenzie Delta, N.W.T., yielded 284 taxa of diatoms of wide-ranging, mainly subarctic–boreal–nemoral geographical affinity. The ionic composition of the water column shows that 17 of the lakes are oligotrophy with roughly similar diatom assemblages. Distinctive diatom assemblages were recorded only from the three chemically exceptional lakes, saline, meromictic, and slightly N enriched, respectively. The ratio of Araphidineae to Centrales proved to have little use in classifying these particular lakes, although it has been effective in other geographical regions.
Diurnal temperature gradients in shallow water produced by populations of artificial aquatic macrophytes
Authors: Dale H. M. , Gillespie T. J.
Published: May 2008

Three artificial populations, with leaf area indices (L) of 4.4, 1.5, and 0.54 were submerged in identical tubs of 1-m3 capacity. Experiments showed that the maximum vertical temperature gradient of the water varied and was dependent on the ratio of solar radiation to wind speed, the leaf area index, and the arrangement of the leaves in the population. The time of day of the maximum temperature gradient was also dependent on L and leaf arrangement. The interception of the light energy by the leaf surface heated the water locally, while the shadow beneath caused the temperature to remain low. With fewer plants, water evaporation was slightly greater. Evaporation resulted in a marl deposit which was confined to the upper surface of the leaves.
Vegetative propagation of sandalwood plants through tissue culture
Authors: Rao P. S. , Bapat V. A.
Published: May 2008

Hypocotyl segments excised from seedlings of Santalum album (sandalwood tree) grown in vitro were cultured aseptically on various nutrient media. Regeneration of shoot buds on explants was observed on basal media supplemented with auxins like IAA, IBA, NAA, or NOA. Shoot bud formation was completely suppressed on 2,4-D or pCPA medium. Cytokinins stimulated and enhanced shoot bud formation better than auxins. Excised stem segments from adult plants did not respond to any hormonal treatment. The importance of this method in the propagation of the sandalwood tree is emphasized.
Chemotaxonomic studies in the Saxifragaceae s.l. 10. The flavonoids of Heuchera cylindrica
Authors: Bohm B. A. , Wilkins C. K.
Published: May 2008

Thirty-three flavonoids have been isolated from Heuchera cylindrica Dougl. var. glabella (T. & G.) Wheelock and at least partially identified. The flavonols kaempferol, quercetin, isorhamnetin, myricetin, and syringetin and the flavone luteolin were found. The flavonols occur in a variety of glycosylated forms, monoglycosides, diglycosides, triglycosides, and gallylated monoglycosides, although not all flavonols exist in all of these forms. Luteolin occurs only as the 7-O-glucoside. Several collections of varieties glabella and cylindrica exhibited identical flavonoid patterns as judged by thin-layer chromatography. Flavonoids, thus, cannot be used as varietal markers. Comparison of the flavonoids of H. cylindrica with those of H. micrantha shows differences which suggest simplification in the flavonoid chemistry associated with evolution within the genus.
The effects of threshold levels of phenylmercuric acetate (PMA) on the paint mildew Aureobasidium pullulans
Authors: Crang Richard E. , Pechak David G.
Published: May 2008

Pure cultures of the paint mildew Aureobasidium pullulans were grown on solid and liquid media, both defined and undefined. Various concentrations of phenylmercuric acetate (PMA) were incorporated in the media, and threshold inhibitory levels were determined. Electron microscopy observations were performed on A. pullulans grown on a defined media which promoted hyphal growth.In the presence of threshold levels of PMA at 200 parts per billion, the cells of A. pullulans were swollen but did not germinate into hyphal filaments. Blastospore production was reduced when compared with non-mercury-containing cultures. The membrane systems of the cells were markedly affected in that the plasma membrane and nuclear envelope were ill defined or wavy in sectional view and the mitochondrial cristae were swollen. Endoplasmic reticulum and microfilament bundles were restricted or lacking in treated cultures.
Interactions entre le chloramphénicol et la 6-benzylaminopurine au cours du verdissement de cotylédons de concombre
Authors: Farineau N. , Hoffeltet M. , Roussaux J.
Published: May 2008

Etiolated cotyledons of cucumber (Cucumis sativus L.) were incubated for 15 h in the dark followed by 72 h in the light in the presence of 10−6 g/ml 6-benzylaminopurine (6-BAP) or 10−4 g/ml chloramphenicol (CHL). These compounds were applied either permanently or only during the dark period, the first 6 h in the light, or the following 66 h in the light. In all cases 6-BAP stimulates both chlorophyll synthesis and plastid differentiation and increases the area of appressed thylakoids. CHL decreases the rate of chlorophyll synthesis only if given during the whole incubation period (dark + light). However, CHL always inhibits the development of the stroma thylakoids and increases both the number of stacked thylakoids per grana and the size of these thylakoids. During the first 6 h in the light, the structure and pigment content of plastids submitted to 6-BAP and CHL (or conversely) appear to be regulated by the compound applied in the dark period. The changes observed in the following light period (after 6 h) depend on the compound present during this period. These results, and those obtained with the two compounds acting simultanously, indicate that the action of these molecules is localized at different cellular levels. The modes of interaction between 6-BAP and CHL are discussed with reference to a biometrical analysis of some structural parameters of plastids.
Evénements structuraux et métaboliques dans les entre-nœuds des bourgeons axillaires du pois, en réponse à la levée de dominance
Authors: Nougarède Arlette , Rondet Pierre
Published: May 2008

Events associated with the release from dominance are described for internodes 1 and 2 of the axillary buds of Pisum sativum. During the inhibited state, most of the nuclei are found in the G1 phase of a diploid cycle. At the release from dominance, some nuclei in the G2 phase during inhibition enter into mitosis and the nuclei in G1 enter into the DNA synthetic phase. Until the 3rd day, a homogeneous reaction is registered for the whole of the two first internodes. Three maxima of mitotic activity are detected in the epidermis, the cortex, and the procambium and only one in the pith. From the 3rd day, the mitoses are localized at the uppermost part of these internodes: meanwhile, elongation occurs in their basal portion. At this level, the nuclear volumes are maximal at the 6th day. After release from apical dominance, the increase in DNA content reflects the resumption of the mitotic cycle and, subsequently, the onset of differentiation, with 4C level nuclei in the cortex and 8C nuclei in the pith. The cell growth of the epidermis, the cortex, and the pith, either radial or tangential, precedes the elongation phase.
The competitive and synergistic interactions of Drechslera sorokiniana and Curvularia geniculata on leaf spot development on Poa pratensis
Authors: Hodges Clinton F. , Madsen James P.
Published: May 2008

Research was initiated to determine interactions between Drechslera sorokiniana and Curvularia geniculata in a potential disease complex on Poa pratensis. Inoculations with D. sorokiniana resulted in the greatest disease severity at 20 and 25 °C: disease severity was minimal with C. geniculata inoculations at all temperatures. Inoculations with the combination of both organisms displayed competitive and synergistic interactions that were temperature dependent. Combination inoculations reduced disease severity below that produced by D. sorokiniana alone and increased disease severity above that produced by C. geniculata alone at 20 and 25 °C and was indicative of a competitive interaction. Inoculations with the combination of the organisms increased disease severity above that produced by either organism alone at 30 °C, indicative of a synergistic effect at higher temperatures. Reisolations of the organisms from lesions produced from inoculations with the combination of the organisms indicated that C. geniculata competes more successfully for infected tissue than D. sorokiniana but is dependent on lesions initiated by D. sorokiniana to establish successfully. Competition for tissue colonization by C. geniculata is greatest at temperatures of 25 to 35 °C. It was concluded that C. geniculata should be recognized as a weak, high-temperature, primary-leaf infecting pathogen of P. pratensis, that a true ‘disease complex’ relative to disease severity can exist between the organisms at 30 °C that is dependent on lesions initiated by D. sorokiniana and reflects the high-temperature aggressiveness of C. geniculata, that tissue invaded by both organisms is more successfully colonized by C. geniculata at higher temperatures, and that the necrotic portions of lesions produced by D. sorokiniana, and on which this organism does not sporulate well, is the probable site of establishment for C. geniculata where the organisms are found together.
Cellular slime molds in tundra and forest soils of Alaska including a new species, Dictyostelium septentrionalis
Authors: Cavender James C.
Published: May 2008

The occurrence and distribution of cellular slime molds in Alaska were investigated. Particular emphasis was given to tundra soils since this habitat was not previously explored for cellular slime molds. Isolations were also made from the white spruce – aspen forest of the interior forest region and the western hemlock – Sitka spruce forest of the southeast coastal forest region. Three species Dictyostelium mucoroides, D. sphaerocephalum, and D. giganteum occur in tundra. The first two species are common and frequently very abundant indicating that cellular slime molds play an active role in tundra ecology. Six other species were found in forest soils. One, Dictyostelium septentrionalis, was found for the first time and is described as a new species. It is distinctive for its size and optimum growth temperature, which is below 20 °C. The study completes the investigation of the latitudinal distribution of cellular slime molds in the northern hemisphere, establishing their occurrence north of the Arctic Circle.
Behavior of Alternaria brassicae and its mycoparasite Nectria inventa on intact and on excised leaves of rapeseed
Authors: Tsuneda A. , Skoropad W. P.
Published: May 2008

On intact leaves of two cultivars (cv.) of rapeseed, Midas (Brassica napus) and Torch (B. campestris), conidia of Alternaria brassicae germinated at a rate of 12.1% and 19.5%, respectively, at 9 h after inoculation. They germinated usually by producing either germ tubes or secondary conidia. Penetration of leaves by A. brassicae was abundant at 24 h and occurred either with or without the formation of appressoria. Penetration of cv. Torch leaves by the fungus occurred either directly through epidermal cells or indirectly through stomata, while cv. Midas leaves were penetrated almost exclusively through stomata. Blackspot lesions developed within 48 h after inoculation.Conidia of Nectria inventa required at least 24 h to initiate germination and 4 days to parasitize A. brassicae on intact leaves. Therefore, N. inventa did not prevent primary infection of the leaves by A. brassicae. Instead, N. inventa suppressed the vegetative growth and sporulation of A. brassicae on excised rapeseed leaves.
A new Hypoxylon species from Wales
Authors: Rogers Jack D. , Whalley A. J. S.
Published: May 2008

A new Hypoxylon species with ridge-like ornamentation on the ascospore, H. chestersii, is described. The fungus was collected in Wales.
The role of oxygen diffusion from the shoots and nodule roots in nitrogen fixation by root nodules of Myrica gale
Authors: Tjepkema John
Published: May 2008

Nitrogenase activity (acetylene reduction) and oxygen uptake by root nodules of Myrica gale L. were measured before and after removal of nodule roots. There was no significant effect of nodule root removal when respiration was measured in the gas phase (0.05–0.2 atm pO2 (1 atm = 101.325 kPa)) or acetylene reduction in a stirred aqueous phase at 0.2 atm pO2. However, when acetylene reduction was measured in 0.05 atm pO2 in an unstirred aqueous phase, there was a 66 to 76% reduction in activity. These results indicate that nodule roots are important for oxygen uptake when the nodules are present in an aqueous phase at low pO2, which is probably the normal environmental conditions for many of the nodules. Other measurements showed that diffusion of oxygen from the shoot to the root nodules is not important for nitrogen fixation. These measurements were done on whole plants with the shoots in air (0.20 atm pO2) and the roots in water at the desired pO2 value. With 0.0 atmpO2 in the root environment, the rate of acetylene reduction was only 4% of the rate at 0.2 atmpO2. Thus, only small amounts of oxygen are transported from the shoot to the nodules.
Characterization and classification of mycorrhizae of Douglas-fir. III. Pseudotsuga menziesii + Byssoporia (Poria) terrestris vars. lilacinorosea, parksii, and sublutea
Authors: Zak B. , Larsen M. J.
Published: May 2008

Three distinct Douglas-fir (Pseudotsuga menziesii) ectomycorrhizae formed by newly recognized varieties of Byssoporia (Poria) terrestris are described. They are named according to tree species and fungus as follows: P. menziesii + B. terrestris var. lilacinorosea. P. menziesii + B. terrestris var. parksii, and P. menziesii + B. terrestris var. sublutea. Each mycorrhiza is macroscopically and microscopically defined, including surrounding mycelium and attached rhizomorphs. Cultural characteristics of the three fungal symbionts grown on potato dextrose agar medium are briefly noted.
The metabolism of glucose in corn coleoptiles in relation to oxygen and 2,4-dinitrophenol
Authors: Forward D. F. , Cheung K-W.
Published: May 2008

[U-14C]glucose was fed in tracer amount to corn coleoptiles and the distribution of 14C was observed after 8.5 h in air, 5% oxygen (extinction point), or nitrogen, in the presence or absence of 2,4-dinitrophenol 9 × 10−6 M. Restriction of oxygen caused increased loss of labelled sugars, mainly between the extinction point and zero oxygen. This accounted for about half of the increase in 14CO2 and [14C]ethanol, the rest resulting from diversion of 14C from synthesis of insoluble tissue compounds. Addition of 2,4-dinitrophenol produced similar results. The data are consistent with current theories of the relation of oxygen and oxidative phosphorylation to the regulation of glycolytic reactions but indicate additional effects in the tissue.The metabolism of exogenous [14C]glucose did not represent that of endogenous substrate. At the extinction point, CO2 from respiration of unlabelled endogenous substrate was less than in air while, 14CO2 from exogenous substrate was greater. The existence and the possible nature of an overriding control of glycolysis in the aerobic state of the tissue are considered.
A procedure for the purification of DNA from tobacco cell cultures and isolation of tobacco single-copy DNA
Authors: Locy R. D. , Hall Ross H.
Published: May 2008

A procedure is presented for the purification of DNA from tobacco callus cells. The procedure can be scaled up for the preparation in large quantity of DNA free of RNA, protein, and polysaccharide. The DNA prepared by this procedure has the same melting temperature and buoyant density as tobacco DNA prepared by previously published procedures and is of sufficient purity to be used for analysis of the reassociation kinetics of tobacco callus DNA. The DNA has been used as a source for the isolation of tobacco single-copy DNA.
Ultrastructure of wilt syndrome caused by Verticillium dahliae. IV. Evidence for α- and β-conidial forms
Authors: Brisson J. D. , Robb Jane , Busch Lloyd
Published: May 2008

Scanning electron microscope observations of leaf petioles of chrysanthemums infected with V. dahliae suggest that two spore forms are present: the normal conidiospore (α conidium) and a sickle-shaped secondary spore or β spore (beta spore). Conidia of V. dahliae appear to be ovoid in shape, possibly septate, and in the host plant, covered by a coating material. Phialides are rarely seen in the host, although the conidia are numerous. Conidia can apparently give rise, simultaneously, to two secondary structures: germ tubes and β spores. The β spores are sickle-shaped structures of constant diameter and when mature are free floating in the vessels.
Morphological and genetic factors influencing the response of weed species to herbicides
Authors: Tomkins D. J. , Grant W. F.
Published: May 2008

The survival of 75 weed species after exposure to herbicides (auxin and nonselective) was monitored over three growing seasons. Each species was classified as resistant, susceptible, or intermediate in response. Polyploids were consistently more resistant to both types of herbicides. In addition, average somatic (but not basic) chromosome number was significantly higher in species resistant to nonselective herbicides than in susceptible ones. The averages of both nuclear volume and interphase chromosome volume were greater in species resistant to auxins than in susceptible ones, although the results were not statistically significant at the 5% probability level. There was a significantly greater proportion of monocots than dicots among the auxin-resistant species, but there was no correlation between life-form and response to either group of herbicides.
Comparison of algae in the euplankton, tychoplankton, and periphyton of a tundra pond
Authors: Sheath Robert G. , Hellebust Johan A.
Published: May 2008

The algal flora of a small tundra pond near Tuktoyaktuk, N.W.T., was examined during the ice-free period in 1974. A total of 166 species were identified from three communities, the euplankton, the tychoplankton, and the periphyton. The taxa containing the highest proportion of species were the Chlorophyceae, Cyanophyceae, Bacillariophyceae, and Chrysophyceae, in that order. There were a number of differences in species composition between the algal communities of the pond. There were 36 unique species in the euplankton, 10 in the tychoplankton, and 15 in the periphyton. The species found exclusively in the euplankton were fairly evenly distributed in the various taxa, whereas a large proportion of the unique species in the tychoplankton were desmids. The species found only in the periphyton were largely diatoms. However, 66 species were present in all three communities. Each community exhibited two biomass increases, the timing of which was slightly different for each association. The major contributors to the biomass of the euplankton were nanoplanktonic flagellates of the Chrysophyceae, whereas the periphyton was dominated by large, colonial, filamentous or desmid members of the Chlorophyceae. The tychoplankton dominants were intermediate between the other two communities. The primary productivity of the euplankton was slightly greater than that of the tychoplankton during the July maximum, while the tychoplankton had a five-fold greater productivity in late August.
Effects of water stress on leaf expansion, net photosynthesis, and vegetative growth of soybeans and cotton
Authors: Bunce James A.
Published: May 2008

Soybeans and cotton were subjected to humidities from 40 to 80% at 23 °C and to soil drought during early vegetative growth under controlled conditions. Measurements were made of leaf water potentials, leaf expansion rates, leaf diffusive resistances to water vapor, and whole-shoot net photosynthesis rates. Net assimilation rates were calculated from harvest data. Low humidity resulted in low leaf water potential and low turgor in all cases and resulted in reduced leaf expansion rates in some, but not all, cases. Low humidity reduced dry weight growth only where leaf expansion rates were reduced. Net photosynthesis rates per unit leaf area were unaffected by low humidity, despite up to 1.5-fold increases in diffusive resistance to water vapor. During soil water stress, leaf expansion rates were reduced 1–2 days before net photosynthesis rates per unit leaf area were reduced, but leaf expansion continued at night after net photosynthesis rates were severely reduced by stress. As a result, the relative importance of leaf area expansion and net assimilation rate to growth in dry weight during soil water stress was dependent on the degree and duration of stress.
The effect of thallus age and drying procedure on extractable lichen substances
Authors: Mirando Martha , Fahselt Dianne
Published: May 2008

Cladonia rangiferina (L.)Wigg., Cladonia mitis Sandst., and Umbilicaria muhlenbergii (Ach.) Tuck, were extracted with acetone while damp and after three different drying procedures. The extracts were chromatographed and scanned spectrophotometrically. Some of the C. rangiferina compounds were not extractable from damp material. All of the lichen substances studied here decreased significantly in thalli which were dried in an oven at 80 °C, some to the point of imperceptibility. There was no qualitative difference between the complement of compounds found in lichen material dried at 22 °C and at 40 °C. We recommend that drying be carried out at a temperature not exceeding 40 °C. Chemical variability among thallus regions of different ages was studied in Cladonia rangiferina, C. mitis, Umbilicaria muhlenbergii, and Lasallia papulosa (Ach.) Llano. Fumarprotocetraric acid, atranorin, and usnic acid were present in significantly higher amounts in younger tissue than in older. Protocetraric acid in C. rangiferina was detectable only in the older portions and would have been overlooked if young branches had been analyzed exclusively. In neither of the two umbilicate lichens was there any significant difference in the concentration of gyrophoric acid between younger and older thallus parts. Chemical variability among different-aged thallus parts was thus greater in the fruticose species than in the umbilicates examined here.
The relationship of buried, germinating seeds to vegetation in an old-growth Colorado subalpine forest
Authors: Whipple Stephen A.
Published: May 2008

Species of buried, germinating seeds and species occurring in the vegetation are compared for two Colorado subalpine forest stands, one dry and one mesic, both over 325 years old. The total numbers of seeds found were small and the correspondence with species in the vegetation was poor. This is consistent with reports from other old-growth forests and may be accounted for by a combination of low seed input and rapid loss of viable seeds from the soil reservoir for old-growth forest species.
Modern pollen rain of Washington
Authors: Heusser Calvin J.
Published: May 2008

Modern pollen rain was studied at 98 sites distributed in a belt transect some 250 km wide running a distance of 425 km between La Push on the Pacific coast and Grand Coulee on the Columbia Plateau. Sites are located in a variety of plant communities from the Picea sitchensis Zone near sea level to the Alpine Tundra Zone at 2285 m in the Cascades. The purposes of the study are (1) to establish the nature of the pollen rain and its relation to vegetation sources and (2) to develop further the pool of potential analogs of fossil pollen spectra for use in the reconstruction of Quaternary environments.Relative frequencies are shown for the pollen of Pinus, Picea, Abies, Tsuga, Pseudotsuga, Cupressaceae, Alnus, Gramineae, Cyperaceae, Chenopodiaceae, Artemisia, and Compositae. Results indicate the pollen rain to be related to source vegetation at the collection sites except for certain instances of infiltration by extraneous types, of which Pinus is most conspicuous. Alnus is the dominant pollen in the Puget Lowland and the western Coast and Cascade Ranges; Tsuga heterophylla is most prominent in the Coast Range; and Pinus ranks foremost in the eastern Cascades and on the Columbia Plateau. On the Columbia Plateau, the Gramineae, Artemisia, Compositae, and Chenopodiaceae are also distinctive. Subalpine forest types and nonarboreals are generally characteristic of the Timberline and Alpine Tundra Zones.
Evidence for the existence of an intramycelial morphogenetic factor controlling the development of coremia of Doratomyces purpureofuscus
Authors: Breton A.
Published: May 2008

Development of excised coremia of Doratomyces purpureofuscus (Fries) Morton and Smith requires the presence of living mycelium at the coremium base. Relations between the vegetative hyphae and the synnema are established by means of anastomosis. Coremial development is controlled by an intramycelial factor which is one or several small thermostable molecules.
The taxonomic status of Vaccinium pallidum, the hillside blueberries including Vaccinium vacillans
Authors: Kloet S. P. Vander
Published: May 2008

Three hundred and seventy three specimens of Vaccinium § Cyanococcus were collected from 43 sites in eastern North America for taxonomic studies. Data collected using various techniques indicate that the hillside blueberries should be recognized as a single species for which the name Vaccinium pallidum Aiton has nomenclatural priority. Three characters, viz. plant height, leaf width and shape, and leaf margin, separate V. pallidum from V. angustifolium; plant height, growth habit, and leaf width separate V. pallidum from V. corymbosum; while leaf size and shape, glandular indumentum, and calyx pubescence separate V. tenellum from V. pallidum. Although V. pallidum and V. corymbosum are sympatric, only a few natural hybrids have been found among the collected material. Crossing trials among the species yielded experimental phenological data which corroborated the validity of these morphological groups.
Ultrastructural localization of polyphenoloxidase and peroxidase in roots and hypocotyls of cotton seedlings
Authors: Mueller W. C. , Beckman C. H.
Published: May 2008

Polyphenoloxidase and peroxidase were localized and differentiated from each other in the roots and hypocotyls of cotton when these tissues were treated with dihydroxyphenylalanine (DOPA) and diaminobenizidine (DAB), respectively. The DOPA reaction occurred in the thylakoids of plastids from the endodermis of the root and in plastids from several tissues of the hypocotyl. The reaction was inhibited by diethyldithiocarbamate (DIECA), but catalase had no effect. An intense DAB reaction occurred in the epidermal, subepidermal, and endodermal cell walls of both roots and hypocotyls with a lesser reaction in the cortex and stele. DAB also caused a reaction in the microbodies in cells of all tissues, but a reaction could not be detected in other organelles. Aminotriazole (AT) inhibited the reaction in the microbodies but not in the cell walls, whereas the reaction was prevented entirely if H2O2 was eliminated from the medium. These results indicate that the two enzyme systems are localized in different and discrete areas in the cotton tissue and that the plastids are intimately involved in phenolic metabolism.