bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies on the haustorium of Castilleja (Scrophulariaceae). II. The endophyte
Authors: Dobbins David R. , Kuijt Job
Published: September 2008

The portion of the Castilleja haustorium within the host, the endophyte, was examined at the light-and electron-microscopic levels. The endophyte consists of a stalk of lipid-containing cells and digitate cells at its tip. Vessels run the length of the endophyte. There is a harmonious meshing between host cortical cells and those of the endophyte flank, suggesting that penetration is accomplished, in part, by cell dissolution. Crushing of cells also occurs during endophyte invasion as host phloem tissues are severely buckled and cell walls are greatly folded. Some features of digitate cells include dense cytoplasm, an abundance of endoplasmic reticulum, lateral walls that are thickened as well as those on the side adjacent to the host, and an ability to conform to the contours of host tissues. Often digitate cells are divided by very thin walls that are hardly visible under the light microscope. It is suggested that the thick cell walls may function as "free space" in the absorption of materials from the host. Within the endophyte, vessels differentiate and may contain either a finely granular, dark-staining material or a more coarsely granular, light-staining material. The particles of the latter have irregular shapes. Although granular materials are thus carried by some vessels, cells resembling the structurally intermediate "phloeotracheids" were not seen. Connections through the cell wall were not observed between parasite and host; however, within the endophyte plasmodesmata were highly branched and often contained median nodules. Transfer-like cells which have irregularly thickened walls occurred in the endophyte. Host tissues next to digitate cells appeared to be in a degraded state. Invaginations of the plasmalemma were common and small flattened vesicles were formed in some host cells from the disrupted tonoplast. In several instances, the cytoplasm had receded from the host cell wall and a "beaded" material was present in both vacuoles and large vesicles. The host cell wall at times had a very loose fibrillar appearance. Some host tracheids were occluded with a dense and dark-staining material. The xylem strands of the parasite are connected to the host xylem either by cell wall dissolution or by actual penetration of a digitate cell into a host xylary cell. The penetrating cell subsequently differentiates into a vessel member. A summary and general discussion are given to relate the two portions of the haustorium, the upper haustorium and the endophyte. The mass of new information gained in this study leads us to encourage the application of plastic embedding and sectioning techniques to further light-microscope studies on haustoria.
Stimulation of chlorophyll synthesis in cucumber cotyledons by benzyladenine
Authors: Fletcher R. A. , Teo C. , Ali A.
Published: September 2008

When exposed to light, etiolated cucumber cotyledons exhibited a lag phase in chlorophyll biosynthesis. Pretreatment of the cotyledons with benzyladenine (BA) eliminated the lag phase and stimulated chlorophyll formation. In BA-treated cotyledons, the incorporation of 14C-leucine into protein and the total synthesis of protein were higher than in the non-BA-treated controls. After BA treatment and exposure to light, the accumulation of δ-aminolevulinic acid in the cotyledons increased with time and was higher than in the controls, where a lag phase was apparent. These results support our hypothesis that BA affects chlorophyll formation by inducing the production of proteins including ALA-synthetase, the rate-limiting enzyme in chlorophyll biosynthesis.
Inflorescence development of semidwarf and standard height wheat cultivars in different photoperiod and nitrogen treatments
Authors: Holmes David P.
Published: September 2008

A comparative study was made of the growth and development of the shoot apex/inflorescence in two contrasting spring wheat (Triticum aestivum L.) cultivars: Marquis—a standard height, day-length-sensitive type; and Pitic 62—a semidwarf, Norin 10 derivative with relatively low day-length sensitivity. The effects of 8-, 12-, 16-, 20-, and 24-h photoperiods and of two nitrogen levels in 12 and 20 h on both cultivars were determined, as well as those of two phosphorus levels on Marquis in 20 h.Apical primordium production continued for a longer duration in Pitic than in Marquis, and the initiation of spikelet primordia was delayed. Spikelet development was more synchronous in Pitic than in Marquis in all treatments. Apical spikelet formation always coincided in both cultivars with the initiation of rachis internode extension. Inflorescence development after termination of spikelet primordia formation was as fast in Pitic as in Marquis (or faster in short photoperiods).In general, increasing N increased the rate and duration of primordium production (apical spikelet formation occurring later at high N), and delayed inflorescence development and extension. These effects were more pronounced in Pitic, resulting in much greater N responses for spikelet and grain numbers per spike, and for grain yields per spike. Effects of high P were similar to those of high N. Increasing photoperiod increased the rate, but decreased the duration of primordium production, and accelerated the development and the extension growth of the inflorescence.The results are discussed in relation to a postulated involvement of endogenous gibberellins and inhibitors in the regulation of inflorescence growth and development.
Six Rhizophydium species (Chytridiales) in culture
Authors: Barr D. J. S.
Published: September 2008

A comparison was made of isolates in culture of Rhizophydium granulosporum Scherffel, R. biporosum (Couch) comb. nov., R. chlorogonii (Serbinow) Jaczewski, R. haynaldii (Schaarschmidt) Fischer, R. laterale (Braun) Rabenhorst, and an unidentified species from water. All isolates grew saprophytically on algae and pine pollen and demonstrated great variability in their morphology on different substrates. An evaluation is given of the characteristics currently used for distinguishing species, and criteria of perhaps more discriminating taxonomic value are suggested.
Environmental control of gametogenesis in Laminaria saccharina. III. The effects of different iodine concentrations, and chloride and iodide ratios
Authors: Hsiao Stephen I. C. , Druehl Louis D.
Published: September 2008

A study was made of the effects of different concentrations of iodide and iodate, and chloride/iodide ratios on meiospore germination, morphology, and gametogenesis of Laminaria saccharina gametophytes in axenic cultures, using a synthetic seawater medium under optimal light, temperature, nitrate, and phosphate conditions.Iodide and iodate were not essential for antheridial and oogonial production, but a small addition of iodine had a stimulatory effect. At low concentrations, iodide was more effective than iodate. At high concentrations, iodate had a less inhibitory effect than iodide. Inhibition occurred at iodine concentrations 60 000 times greater than that in natural seawater. This inhibition diminished with increasing chloride concentrations. The natural chlorinity of seawater might counteract adverse iodine effects on the marine algae thus allowing them to accumulate high concentrations of iodine.
Penetration and invasion of sunflowers by Sclerotium bataticola
Authors: Chan Y. H. , Sackston W. E.
Published: September 2008

Sclerotium bataticola forms appressoria on the epidermis of inoculated sunflower seedlings. The appressoria may aid both mechanical and chemical penetration. Penetration is direct. Penetration of adult plant stems is by mass action of hyphae.Invading hyphae are both intra- and inter-cellular. Longitudinal spread in the cortex is in the intercellular spaces. Hyphae are closely associated with cell walls and the walls of xylem vessels. Vessels are penetrated through the pits.A virulent isolate formed sclerotia on inoculated seedlings within 24 h. An avirulent isolate formed chlamydospore-like resting structures first, and sclerotia later. Sclerotial formation appeared to reflect level of nutrition rather than relationships of isolates.
Geotropic response patterns of the Avena coleoptile. I. Dependence on angle and duration of stimulation
Authors: Pickard Barbara Gillespie
Published: September 2008

A systematic study was made of the kinetics of geotropic response of coleoptiles of Avena sativa L., cv. Victory.Over a reasonably large range, response could be approximated as a linear function of stimulus duration for coleoptiles stimulated by horizontal placement. The threshold for induction of subsequently visible curvature was about 20 s, but evidence is presented that inductive reactions begin as soon as the coleoptile is set on its side. Corroboratively, intermittently administered stimuli as brief as 0.5 s were summed without loss.Plants were stimulated at selected angles between 0° and 90° from the vertical position of equilibrium for an arbitrarily selected time, and response was linearly dependent on the perpendicular component of acceleration. This dependence supports the hypothesis that geotropism is a response to the differential exertion of pressure. Data for supplementary angles are also consistent with the pressure hypothesis.
Preliminary studies on the ecology of palsa mounds in northern Ontario
Authors: Railton J. B. , Sparling J. H.
Published: September 2008

Peat mounds with frozen permafrost cores, or palsas, occur in areas with sporadic permafrost in subarctic and boreal parts of Canada. In northern Ontario, the surface vegetation of palsas is characterized by the presence of Cladonia alpestris, C. rangiferina, and C. sylvatica with occasional stunted Picea mariana which are surrounded by Ledum groenlandicum and Vaccinium vitis-idaea. From vegetational analysis, hummock and palsa morphology, and radiocarbon dating, evidence is given for a recent origin under climatic conditions similar to the present. The largest palsas appear to be about 200 years old. Details of energy exchange during July are given for mature, partially eroded, and collapsed palsas. The formation of palsas may be dependent on changes in surface albedo associated with vegetational change from Sphagnum fuscum to Cladonia spp. dominated communities where the albedo was found to increase from 13.8% to 21.3%. However, evidence is presented that decreased penetration of heat during summer associated with the drying of surface peat may be important in palsa formation. Lower thermal conductivity of the peat at this time would insulate the ice core from insolation. Collapse of palsas was attributed to surface and marginal erosion and higher heat penetration to the core associated with wetter peat conditions on the palsa.
A transcellular water flux induced by light in Nitella
Authors: Fensom D. S. , Barclay S. L. , Law Sophie , Thompson R. G.
Published: September 2008

When Nitella cells in artificial pond water (APW) are illuminated in an electroosmometer, water appears to move into the closed chamber of the instrument. This has been termed the "basic flow" of the instrument. A part of this basic flow is thermal expansion but an appreciable part is a water flow through the living cell. This transcellular water flow is increased by illumination of any part of the cell and is mostly removed by 10−3 mM N-dichlorophenyl-N′,N′-dimethylurea (DCMU). It is readily altered by conditioners which alter the membrane properties at one end of the cell compared with the other: carbonyl cyanide m-chlorophenyl-hydrazone (CCCP) at 5 × 10−3 mM, dinitrophenol (DNP), 10−1 mM ouabain, and particularly pH. Asymmetrical changes in the hydraulic permeability of the membrane are indicated as the most probable cause of this water flow.An electric current flows between the two ends of the cell when the cell is differentially illuminated, particularly at the beginning or end of the light change. The current is thought to indicate the presence of some electrogenic pumps on the plasma membranes.
The effect of some growth-regulating compounds upon electroosmotic measurements, transcellular water flow, and Na, K, and Cl influx in Nitella flexilis
Authors: Wanless I. R. , Bryniak Nancy , Fensom D. S.
Published: September 2008

By using a small, constant, applied current on a cell of Nitella in artificial pond water, it was possible to compare the effect of different growth-regulating compounds on the apparent electroosmotic water coupling in the cell wall – membrane complex. Indoleacetic acid (IAA) at first enhanced the electro-osmotic effect and then ceased to alter it, but began to change the asymmetric transcellular water flow. Gibberellic acid (GA), when added to IAA, increased this effect, while abscissic acid (ABA) added to IAA decreased it. Some compounds like naphthaleneacetic acid (NAA), alar-83, skatol, or ABA alone, had no effect on the electroosmotic (eo.) coefficient; but NAA, skatol, ABA (alone) changed the asymmetric water flow (basic flow) and some ion influxes. Light-degraded IAA acted in a manner very similar to skatol, which suggests that IAA is quickly converted to skatol in the cell in the presence of light. With light–dark transitions or with IAA, the electroosmotic coefficient changed in a manner parallel to passive ion (Na+ and K+) influx, but was not related to basic flow or Cl− influx changes.Under controlled conditions of low constant current applied to a test cell, it has been shown that a change in apparent eo. coefficient upon auxin addition is largely a reflection of change in the true electroosmotic properties of the cell membrane at the positive end of the cell.
Cell wall structures of Epicoccum nigrum (Hyphomycetes)
Authors: Brushaber J. A. , Haskins R. H.
Published: September 2008

Two structurally distinct types of secondary wall layers are present in older hyphae in addition to the primary wall. A coarsely fibrous outer wall layer often becomes quite massive and frequently fuses with the outer wall layers of adjacent cells in the formation of hyphal strands. The uneven deposition of this outer layer often produces large verrucosities. The inner secondary wall layer is relatively electron transparent and contains a reticulum of electron-dense lines. The interface of the inner secondary wall with the cytoplasm is often very irregular, and sections of the plasma membrane are frequently overlain by wall material. The outer secondary wall of conidia is composed of an electron-dense material different from that of the outer wall of hyphae. Cells in the multicellular conidia tend to be polyhedral in shape with either very thick primary walls or thin primary walls having a thick inner wall deposit.
A variety of Puccinia centaureae on Centaurea diffusa
Authors: Savile D. B. O.
Published: September 2008

A rust from Krymsk, U.S.S.R., strongly adapted to Centaurea diffusa, has small urediniospores and large teliospores, and is named Puccinia centaureae var. diffusae. It holds promise as a control agent for this weed.
Phylloplan et phyllosphère
Authors: Diem Hoang G.
Published: September 2008

In consequence of the observations on the stimulation at the leaf surface of microbial activity, by pollen grains in the regions named "palynoplane" and "palynosphere," new definitions are proposed to explain the two terms phylloplane and phyllosphere.
Conidium ontogeny in hyphomycetes. The blastoconidia of Cladosporium herbarum and Torula herbarum
Authors: Hashmi M. H. , Morgan-Jones G. , Kendrick Bryce
Published: September 2008

Conidium ontogeny in Cladosporium herbarum (Pers.) Link ex S. F. Gray and Torula herbarum (Pers.) Link ex S. F. Gray is analyzed by time-lapse photomicrography. Both fungi are shown to produce conidia holoblastically in acropetal chains.
Seasonal changes in the standing crop of two montane sedges
Authors: Gorham Eville , Somers Maureen Gibson
Published: September 2008

Aboveground green biomass of a montane pure stand of Carex rostrata varies from about 125 g/m2 (air-dry weight) at the end of November to about 640 g/m2 in early August. The maximum production rate of about 6 g/m2 per day occurs in May. For a nearby stand of Carex aquatilis with a prominent moss layer the aboveground green biomass of sedge material varies from about 40 g/m2 in February to about 380 g/m2 in mid-August. The maximum production rate for sedge material is about 4 g/m2 per day in July. Both species exhibit two main populations of shoots, one emerging in late summer and the other through winter and early spring. The winter and spring shoots of Carex rostrata flower and die after about 18 months, while the late summer shoots, which do not mature vegetatively until the following summer, have a life-span of about 2 years. The late summer shoots of Carex aquatilis mature vegetatively before winter, and flower and die within about 12 months; while the winter and spring shoots live through the next winter, and flower and die the following summer after a life-span of about 18 months.
Studies on lichen-dominated systems. III. Phytosociology of a raised-beach system near Cape Henrietta Maria, northern Ontario
Authors: Neal Micheal W. , Kershaw Kenneth A.
Published: September 2008

A modified version of the Braun–Blanquet technique for the analysis of plant associations was applied to an area of lichen-dominated raised-beach system near Cape Henrietta Maria in subarctic northern Ontario. Eleven plant associations were extracted which appear to follow ecological gradients related to water availability, soil pH, and the presence/absence of a peaty substratum. It was concluded that this type of association analysis fulfilled all the major objectives of a preliminary survey.
A relationship between nuclear volume and response to auxin herbicides for some weed species
Authors: Mohandas T. , Grant W. F.
Published: September 2008

The responses of 15 weeds (Agropyron repens, Centaurea cyanus, C. jacea, Chrysanthemum leucanthemum, Cirsium arvense, C. vulgare, Daucus carota, Erigeron canadensis, Euphorbia cyparissias, E. esula, Nasturtium officinale, Neslia paniculata, Plantago major, Silene cucubalus, Vicia angustifolia) to eight herbicides were considered in relation to the level of ploidy, the life form, the nuclear volume, and the interphase chromosome volume, for each species. In general, susceptible weeds had a lower nuclear volume than those showing an intermediate or a resistant response to the herbicides. Interphase chromosome volume did not show any consistent relationship with the degree of susceptibility. Intermediate and resistant plants were mostly perennials, whereas susceptible ones were annuals or biennials.
Regulation of cell reproduction in bud meristems of Tradescantia paludosa
Authors: Yun Kyu-Byung , Naylor J. M.
Published: September 2008

The mitotic cycle can be arrested in the apical summit of vegetative terminal buds of Tradescantia paludosa by restricting the level of nitrogen or light available to the plant. Cells in this portion of the bud are much more sensitive to these stress conditions than those in the subjacent portion of the meristem. This differential response induced the establishment of a quiescent "central zone" which is distinguished from the rest of the meristem by the apparent absence of mitosis and DNA synthesis, larger nuclear volume, and a lower histone content of chromatin. These features are identical with those imposed by apical dominance in apices of inhibited lateral buds.The results support the view that competition for nutrients is an important causal factor in apical dominance. They suggest also that competition for nutrients within the terminal bud meristem is important in the regulation of growth in vegetative shoots in respones to conditions of the environment.
Age- and size-related response of lodgepole pine to inoculation with Europhium clavigerum
Authors: Shrimpton D. M.
Published: September 2008

In 1970, 280 lodgepole pines between 8 and 140 years old, in the east Kootenay region of British Columbia, were inoculated with Europhium clavigerum. The resinous response of the tree to this inoculation was used as a measure of potential resistance to bark beetle attack. Trees between 31 and 50 years old had the greatest frequency of potentially resistant individuals. The following year, 250 trees between 10 and 120 years old were inoculated on June 11, July 5, and July 23, with similar results. The youngest (10–30) and oldest (91–120) trees had a greater decrease in frequency of resistant individuals, as the summer progressed, than the intermediate age classes. Trees rated as potentially resistant from all three inoculations had faster growth rates and thicker phloem than those rated nonresistant.
Studies on lichen-dominated systems. IV. The objective analysis of Cape Henrietta Maria raised-beach systems
Authors: Neal Michael W. , Kershaw Kenneth A.
Published: September 2008

A principal-component ordination technique was applied to Domin-based data from the Cape Henrietta Maria raised-beach systems. Eight of the 11 associations originally extracted by Braun–Blanquet methods were retained while the remaining three showed good reason to be grouped into one. Multiple regression trend surface analysis was applied to selected dependent variables mapped onto the ordination, and showed significant large-scale variations in the distribution of these points that were related to ecological factors.
Electrophoretic analysis of effects of in vitro heating on proteins and enzymes from dormant peanuts (Arachis hypogaea)
Authors: Thomas Dempsey L. , Bright James E.
Published: September 2008

Protein extracts from dormant peanut cotyledons were heated to determine the influence of different temperatures on banding characteristics of soluble proteins and enzymes by use of horizontal starch gel electrophoresis. Soluble proteins showed no significant change between 25° and 85 °C. At 95 °C, however, major bands of reserve protein decreased in staining intensity and new bands with greater migration velocity appeared; banding still occurred at 100 °C. Distribution patterns of glutamate dehydrogenase (GDH), malate dehydrogenase (MDH), nonspecific α-esterases (α-EST), and leucine aminopeptidase (LAP) reflected no change in banding or apparent enzyme activity at temperatures less than 45 °C. Complete inactivation was estimated for GDH at 80 to 85 °C, MDH at 65 °C, α-EST at 60 to 65 °C, and LAP at 60 to 65 °C. Isoenzymes of GDH, MDH, and LAP, and bands of α-EST exhibited differential thermal sensitivity. Peroxidase activity (using pyrogallol as the hydrogen donor) was not influenced through 65 °C; minimal reaction with benzidine occurred. No alkaline phosphatase activity was observed. Banding patterns of proteins or enzymes heated for 15 min were identical with those heated for 30 min. The results are compared with those of other studies regarding the influence of heat on proteins and enzymes in extracts of heated cotyledons from 5-day peanut seedlings and in extracts from wet- and dry-roasted seed.
The metabolism of 14C-urea by white spruce seedlings in light and darkness
Authors: Durzan D. J.
Published: September 2008

Weak urease activity was detected in 2-week-old white spruce seedlings. The addition of urea to these seedlings increased urease activity in light compared to darkness. Urease was localized in the cytoplasm mainly in the epidermal cells, and to a lesser extent in vascular tissues and at the shoot apex.In light, the early products of 14C-urea indicated the release of 14C-carbon dioxide and ammonium ions. Radioactivity appeared in the anionic and neutral fractions and then in alanine, serine, and glycine, just as in the fixation of 14C-bicarbonate. By 4 h most radioactivity resided in glutamic acid and alanine. This pattern was associated with increased protein synthesis, and with high levels of free glutamine. Serine, glycine, alanine, and carbamyl aspartic acid had high specific activities.In darkness, radioactivity in alanine persisted, but levels in serine, glycine, and protein were low. Most radioactivity eventually resided in asparagine. Radioactive urea and citrulline were kept at higher levels than in light. Glutamic acid, citrulline, and carbamyl aspartic acid had the greatest specific activities. In light and darkness, carbamyl derivatives were formed more readily from 14C-urea than from 14C-bicarbonate.Carbamyl phosphate was implicated as a precursor of citrulline and arginine as well as for carbamyl aspartic acid. In light, radioactivity was recovered from ribosomal (25, 23, 18, 16, and 5 S) and transfer RNA (4 S). This resided mainly in uracil and cytosine. By contrast, in DNA, radioactivity was recovered mainly from thymine, cytosine, and 5-methylcytosine. In rapidly growing seedlings, urea contributed to de novo nucleic acid synthesis mainly through pyrimidine pathways via carbamyl aspartic acid.
The influence of nitrate on the induction of nitrate reductase in maize roots
Authors: Stevens D. L. , Oaks Ann
Published: September 2008

A concentration of 10 mM NO3 saturates the induction of nitrate reductase in maize root tips whereas concentrations up to 100 mM do not saturate the induction in mature root sections. Increasing concentrations of nitrate from 1 to 25 mM have no effect on either the lag phase, or the phase of rapid increase of the enzyme. They do influence the final level of enzyme obtained at 8 h.
Lipid and sugar metabolism during the afterripening of sour cherry embryos
Authors: LaCroix L. J. , Jaswal A. S.
Published: September 2008

Stored lipid decreased in cotyledons of afterripening seed of sour cherry (Prunus cerasus L.). The lipid apparently is degraded to acetate and metabolized by the glyoxylate cycle and reversal of glycolysis to free sugars, which are then transported to the embryonic axis, the major site of respiration during afterripening. The provision of substrate allows for activation of the pentose phosphate cycle, an increased respiratory rate of this tissue, and production of the necessary intermediates for synthesis of essential structural elements necessary for the germination process.
Ascocarp development in Ascobolus michaudii
Authors: Paden John W. , Stanlake Elizabeth A.
Published: September 2008

The ascocarp initial of Ascobolus michaudii Boud. is a coiled, septate ascogonium that is enveloped by hyphae that originate from nearby vegetative cells. The young asci and paraphyses develop within the closed, immature apothecium, and the species is therefore cleistohymenial. Opening of the apothecium occurs during the mid-mesohymenial phase of development. Single ascospore cultures are fertile. The origin of the sheath hyphae in A. michaudii is compared with other species of Ascobolus.
The genus Macbridella with notes on Calostilbe, Herpotrichia, Phaeonectria, and Letendraea
Authors: Samuels Gary J.
Published: September 2008

The brown coloration of ascospores is rejected as a generic character in the Hypocreales. The asci of the type species of Macbridella, M. chaetostroma (= Herpotrichia rhodosticta), are bitunicate. Macbridella olivacea (= M. cinnabarina), M. amazonensis, M. sansevierae, and M. striispora have unitunicate asci and are treated as species of Nectria. The asci of the type species of Letendraea, L. eurotioides, are bitunicate. Letendraea eurotioides is lectotypified. Phaeonectria is found to be synonymous with Calostilbe; Calostilbe is regarded as a synonym of Nectria.
Studies on lichen-dominated systems. VI. Interrelations of vegetation and soil moisture in the Hudson Bay Lowlands
Authors: Rouse W. R. , Kershaw K. A.
Published: September 2008

Soil moisture measurements are presented for the summer period of 1971 for nine sites spaced inland from the Hudson Bay coastline adjacent to East Pen Island. The sites show a great variation in natural vegetation from a sparsely vegetated young raised-beach to older beach ridges dominated by thick mats of lichen. The sites include a non-vegetated blowout in a sand dune and areas which have been damaged by caterpillar tractors and by burning.Differences in soil moisture between sites are very pronounced and are closely related to the organic content of the soils. There are also substantial variations in the rate of soil moisture withdrawal during the summer period and this is reflected in differences in the seasonal evapotranspiration rates. The soil moisture characteristics are widely variable in the surface soils at the different sites but virtually the same at soil depths below 30 cm.
Nematophagous fungi: Haptoglossa
Authors: Davidson J. G. N. , Barron G. L.
Published: September 2008

Haptoglossa heterospora Drech. is redescribed and compared with H. zoospora, which is described as new. In H. zoospora the contents of the infection thallus cleave to form primary zoospores. The encysted zoospore is homologous with the spherical primary spore of H. heterospora. The secondary glossoid spores are apparently not adhesive as previously claimed. The peculiar shape of glossoid spores is related to a unique mechanism of infection whereby infective tertiary spores are injected into nematodes in an extremely short period of time. Tertiary spores develop into separate thalli.
Endogenous rhythmicity and energy transduction. I. Rhythmicity in adenylate kinase, NAD- and NADP-linked glyceraldehyde-3-phosphate dehydrogenase in Chenopodium rubrum
Authors: Frosch Silvia , Wagner Edgar , Cumming Bruce G.
Published: September 2008

It is demonstrated that adenylate kinase (AK) as well as NAD- and NADP-dependent glyceraldehyde-3-phosphate dehydrogenase (NAD- and NADP-GPD) display an endogenous rhythm in the time courses of their activities in constant conditions. The rhythm in AK activity has a period length of close to 30 h with two 15-h subpeaks in each 30-h period. The cycles in NAD- and NADP-GPD activity have a period length of 15 h and have an inverse phase relationship. The amplitude of the rhythm at the end of a dark period provides the base line for increase in enzyme activity in light after darkness. The increase in light is essentially the same regardless of the length of darkness. There is a differential effect of glucose feeding in light as compared to darkness. In darkness, glucose feeding increased NAD-GPD and AK activity but had no effect on NADP-GPD activity. In light, glucose caused an increase in NAD-GPD as well as AK activity over the Hoagland's controls but not in NADP-GPD, which was less than in the controls.The results are discussed in relation to a hypothesis assuming that endogenous rhythmicity might be due to the spatial separation of energy production and utilization in different cellular compartments with strong dependence on key coenzymes.
A study of DNA and mitotic activity in the vegetative apex of Douglas fir during the annual growth cycle
Authors: Owens John N. , Molder Marje
Published: September 2008

Vegetative apices of Pseudotsuga menziesii (Mirb.) Franco were studied throughout the annual growth cycle. When observations based on anatomy, histochemistry, and external morphology are combined, the growth cycle of the vegetative apex should be subdivided into five stages: (1) dormancy, (2) early bud-scale initiation, (3) late bud-scale initiation and rapid apical enlargement, (4) early, rapid leaf initiation, and (5) late, slow leaf initiation. The same cytohistological zonation pattern is present in vegetative apices throughout the growth cycle and usually consists of apical, peripheral, and rib meristem zones. During dormancy, early bud-scale initiation, and early leaf initiation, the apical zone is separated into apical initials and central mother cells based on nuclear characteristics and mitotic activity. Cytohistological zonation is supported by constant differences in nuclear volume, mitotic activity, and DNA content between zones. The peripheral zone is mitotically more active than the apical zone; however, the apical zone is not quiescent. Zones vary in size, prominence, and mitotic activity, which often relates to a particular developmental stage of the apex. The dormant apex has no mitotic activity, and cytohistological zonation is present but not distinct. Zonation increases throughout the first half of the growing season, reaches a maximum during late bud-scale and early leaf initiation, and decreases as dormancy approaches. In general, increases in nuclear volume, percentage of nuclei at 4C, and average DNA content per nucleus correlate with increases in the prominence of zonation. Zonation did not result from different zones being "held" at certain C levels of DNA. Although nuclear volume was used in calculating the DNA content, the DNA level often varied independently of volume. Mitotic activity and dormancy appear to be related to carbohydrate levels within the bud and subtending shoot. The period of most prominent zonation is also the period of most active primordial initiation, largest apical size, and the time when new axillary shoots become determined in their pathway of development.
Notes on Hyphomycetes. IV. The genus Amphichaetella Höhnel
Authors: Morgan-Jones G.
Published: September 2008

The genus Amphichaetella Höhnel is redescribed and illustrated.
Conidium ontogeny in Riessia semiophora
Authors: Goos R. D. , Tubaki K.
Published: September 2008

Riessa semiophora is an imperfect fungus with basidiomycetous affinities. In culture, the fungus produces two types of conidia: unicellular microconidia and the compound stauroconidia that typify the genus. Both types of conidia are dikaryotic and on germination give rise to a mycelium bearing clamp connections. Their ontogeny is holoblastic, the microconidia arising as separate blown-out points on the apex of the conidiophore, while the stauroconidia develop by the enlargement of the conidiophore apex into, usually, four lobes. Each cell of the stauroconidium is binucleate and capable of germination.
Vegetation changes in shallow marsh wetlands under improving moisture regime
Authors: Millar J. B.
Published: September 2008

Changes in species composition and plant cover were studied in relation to moisture regime over a 10-year period in 71 shallow marsh wetlands in the grassland and parkland regions of Saskatchewan. Decreases in density of the shallow marsh emergents Polygonum coccineum, Carex atherodes, Scolochloa festucacea, and Eleocliaris palustris occurred with greater-than-normal water depth at the start of the growing season but 2 or more years of continuous flooding were required to eliminate emergent cover completely and convert the wetland to open water. Repeated autumn reflooding also resulted in complete elimination of emergent species. Changes in species composition occurred when basins were grazed and as vegetation reestablished after cultivation but no changes followed mowing or burning. Alopecurus aequalis, Beckmannia syzigachne, Glyceria grandis, and G. pulchella are designated as "disturbance" species on the basis of their response to soil-exposing events. Presence of small amounts of deep marsh emergents in shallow marsh wetlands is not considered a reliable indicator of wetter moisture regime. Species composition of rooted submergents in a wetland can be used as an indicator of its moisture regime. Shallow marsh wetlands in basins of 1 ac (0.41 ha) or less experienced little year-long flooding and converted to open water only under atypical conditions. Larger wetlands required basin depths in excess of 36 in. (96.4 cm) to have any amount of year-long flooding and to convert to open water. These basin size and depth criteria have applications in habitat evaluation by waterfowl managers.
New concepts and terminology of coniferous periderms: necrophylactic and exophylactic periderms
Authors: Mullick D. B. , Jensen G. D.
Published: September 2008

Field observations were made on wound and pathological periderms, regardless of the causal agent, and periderms formed at abscission zones, old resin blisters and rhytidomes in Abies amabilis (Dougl.) Forbes, Abies grandis (Dougl.) Lindl., Tsuga heterophylla (Raf.) Sarg., and Thuja plicata Donn. It was established that these periderms were of reddish-purple sequent periderm (rsp) type, rather than either the brown first periderm (bfp), or brown sequent periderm (bsp) types. These reddish-purple pigmented periderms, like the rsp (the usual sequent periderm) were found abutting necrotic tissues and were moreover identical with rsp in 15 newly demonstrated cryofixation and chemical characteristics. Because of this equivalence, it is proposed that all these reddish-purple periderms, including the usual sequent periderm (rsp), constitute one category, the necrophylactic periderms. These periderms arise whenever regeneration of a periderm after death of cells is required, and their main function seems to be protection of living tissues from the adverse effects associated with cell death. Because of the equivalence of bfp and bsp, they constitute another category, the exophylactic periderms. This second category of periderms has a common function of protecting living tissues against the external environment.
The water relations of hemlock (Tsuga canadensis). I. Some equilibrium water relations as measured by the pressure-bomb technique
Authors: Tyree M. T. , Dainty J. , Benis M.
Published: September 2008

Theoretical and experimental aspects of the equilibrium water relations of excised hemlock (Tsuga canadensis) shoots are examined. The equilibrium water relations of hemlock were determined by using the pressure-bomb technique on shoots 15 to 40 g in fresh weight. At or near full turgor the osmotic pressure of the cells averages 16.5 + 0.4 bars. The fraction of the total water content of hemlock shoots residing in the living cells is 0.77 + 0.04. When hemlock shoots are near full turgor the balancing pressure will change linearly with the volume expressed provided the volume changes represent less than [Formula: see text] of the total shoot water content.
The water relations of hemlock (Tsuga canadensis). II. The kinetics of water exchange between the symplast and apoplast
Authors: Tyree M. T. , Dainty J.
Published: September 2008

We present a theoretical analysis of the events that occur while a plant enclosed in a pressure bomb evolves from one equilibrium balancing pressure to another. The initial rate of efflux from any one cell in response to a pressure increment of ΔP equals (ALp)i ΔP, where (ALp)i is the surface area times hydraulic conductivity of the cell's semipermeable membrane(s). If the volume changes and pressure increment are small, the cell will approach equilibrium exponentially. The half time of the exponential process is governed by (ALp)iki, where ki is the cell constant (= the combined rate of change of osmotic and turgor pressure with the volume expressed from the cell). Experimental studies of the kinetics of water exchange between the symplast and apoplast of hemock (Tsuga canadensis) shoots in a pressure bomb reveal that the cells collectively behave as though they fall into three distinct populations which approach equilibrium with different half times.
Photosynthetic 14C-labeling patterns in developing soybeans
Authors: Noble R. D. , Long D. W. , Burley J. W.
Published: September 2008

Soybean plants (Glycine max 'Harasoy') were cultured in a controlled environment room and studied at seven ages ranging from 16 to 40 days after flowering. Fruits from each age group were labeled by translocation of organic compounds from leaves which had photosynthetically incorporated 14CO2. Leaf blades, petioles, and seeds were extracted in boiling ethanol at the termination of labeling experiments. Seeds were also harvested and extracted 1, 2, and 8 days after labeling. Distribution of label in leaf blades and petioles was essentially the same in all age groups with more than 90% of the activity in petioles being found in carbohydrates. Little or no translocation of amino acids and organic acids was occurring. In seeds, most of the label appeared in the carbohydrate fraction immediately after labeling; however, at 2 and 8 days after labeling the label seemed to be transferred to lipids and the ethanol-insoluble residue. The rate of transfer decreased as a function of seed age. Levels of activity in the amino acid and organic acid fractions were low in all samples.
Regulation of mitosis. IV. An in vitro and ultrastructural study of effects of trifluralin
Authors: Jackson William T. , Stetler David A.
Published: September 2008

Cell-wall-free endosperm cells of the African blood lily (Haemanthus katherinae Baker) were observed while undergoing mitosis on control medium or on medium containing the herbicide trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine). The percentage of cells proceeding from an initially observed stage to the next stage, in controls versus treatments, was as follows: prophase to prometaphase, 85 versus 16; prometaphase to metaphase, 80 versus 33; metaphase to anaphase, 95 versus 50; and anaphase to cell plate appearance, 98 to 49%.An analysis of time-lapse films of trifluralin-treated mitotic cells reveals that many of the previously reported abnormalities do not represent end points of herbicide action, but rather stages leading to fusion of daughter nuclei. Ultrastructural studies show a decreased number of microtubules and an accumulation of large vesicles in the cell plate region. These vesicles exclude microtubules and cell plate material. It is postulated that the decrease in number of microtubules and in the amount of cell plate material permits movement of daughter nuclei to a central position where fusion occurs.
Ascospore sculpturing in Morchella (Ascomycetes: Pezizales)
Authors: Malloch David
Published: September 2008

Ascospore sculpturing is reported for the first time in the genus Morchella. The species of Morchella and the family Morchellaceae had previously been considered to be characterized by smooth ascospores. The geographic distribution of collections showing this phenomenon is given, based on specimens in DAOM and TRTC.
Endogenous rhythmicity and energy transduction. II. Phytochrome action and the conditioning of rhythmicity of adenylate kinase, NAD- and NADP-linked glyceraldehyde-3-phosphate dehydrogenase in Chenopodium rubrum by temperature and light intensity cycles during germination
Authors: Frosch Silvia , Wagner Edgar
Published: September 2008

Endogenous rhythmicity in NADP- and NAD-linked glyceraldehyde-3-phosphate dehydrogenase (NADP- and NAD-GPD) as well as in adenylate kinase (AK) activity is initiated or synchronized during cyclic germination conditions of light and temperature, and is free-running in a dark period interrupting continuous light.There is phytochrome control of the amplitude in NADP-GPD and AK oscillations during the first hours of darkness if the beginning of the dark period is in phase with the beginning of the germination period. The endogenous rhythm acts like an "on-off" switch for potential phytochrome action. The results are discussed in relation to daily photoperiodic cycles.
Endogenous rhythmicity and energy transduction. III. Time course of phytochrome action in adenylate kinase, NAD- and NADP-linked glyceraldehyde-3-phosphate dehydrogenase in Chenopodium rubrum
Authors: Frosch Silvia , Wagner Edgar
Published: September 2008

Evidence is presented that phytochrome triggers and maintains the increase in adenylate kinase (AK) as well as NAD- and NADP-dependent glyceraldehyde-3-phosphate dehydrogenase (NAD- and NADP-GPD) activity. After cyclic germination conditions, the time courses of all three enzymes display an endogenous rhythmic increase of their activities in constant far-red light. After germination in constant conditions, NAD- and NADP-GPD activities displayed no rhythm, while AK activity increased rhythmically. Such readiness of AK activity to oscillate was taken as indication of a close functional relationship between the control mechanism(s) of the endogenous rhythm and AK activities. The time courses in NADP-GPD activity demonstrated that phytochrome acted as an on-off switch for the increase in enzyme activity and also controlled enzyme activity depending on the relative concentration of active phytochrome. There is evidence for a function of phytochrome in the "ground state" as well as in an "activated state."It is suggested that phytochrome could be coupled to endogenous rhythmicity by modulating the redox potential of the cell, while phytochrome action itself would be timed by the endogenous rhythm.
The water relations of hemlock (Tsuga canadensis). III. The temperature dependence of water exchange in a pressure bomb
Authors: Tyree M. T. , Benis M. , Dainty J.
Published: September 2008

The pressure-bomb technique has been used to measure the temperature dependence of water exchange between the apoplast and symplast of hemlock (Tsuga canadensis) shoots. By applying the Arrhenius rate theory, the activation energy for water exchange in the whole shoot equals 25.9 + 0.6 × 103 J per mole. A theory is proposed on the basis of the Arrhenius rate equations which allows us to predict the relative magnitudes of the membrane resistance, Rm, and the extracellular resistance, Rx, to water permeation. On the basis of our calculations, we believe Rm is at least one-quarter of Rx and may even exceed Rx, but more work needs to be done to be sure.
A factor analysis of the distribution of some Puerto Rican liverworts
Authors: Bryant Edwin H. , Crandall-Stotler Barbara , Stotler Raymond E.
Published: September 2008

Trends in the distribution patterns of 155 species of leafy hepatics over 10 distinct areas in the Luquillo Mountains of Puerto Rico were revealed by factor analysis. The three factors of the Q-mode (area × area) analysis contrasted (1) high-altitude with low-altitude habitats, (2) shaded, moist habitats with open, more exposed habitats of all elevations, and (3) disturbed low-elevation habitats with less disturbed habitats of all elevations. The R-mode (species × species) analysis produced almost identical distribution trends. The coincidence of these two results allowed us to determine which plant species were primarily indicative of habitat differences.
Ultrastructure and morphogenesis of the synnema of Ceratocystis ulmi
Authors: Harris James L. , Taber Willard A.
Published: September 2008

Ceratocystis ulmi, the Ascomycete responsible for Dutch elm disease, may sporulate by means of a distinctive structure, the synnema, common in nature in the tunnels of elm bark beetles. Developmental stages of this structure and its spores were examined by light microscopy, by conventional transmission electron microscopy of thin sections and freeze-etch replicas, and by scanning electron microscopy of whole spores and fruiting structures. The synnema is a tight bundle of darkly pigmented hyphae growing erect from the substrate and terminated by a mass of colorless, wet spores. A layer of slime covering the hyphal bundle and random cross-connections between parallel hyphae appear to function in stabilization of the structure. Organelles typical of Ascomycetes fill the spores, vegetative hyphae, and young synnemal hyphae. However, in mature synnemal hyphae, the cytoplasmic contents degenerate, leaving only membranous vesicles in the partially collapsed hyphae. The spores contain large lipid droplets not found in either vegetative or synnemal hyphae indicating some differences in metabolism of spores and hyphae. Most synnemal spores form on sympodulae, but some spores form on intrahyphal hyphae.
Photosynthetic ecology of normal and variegated Aegopodium podagraria
Authors: Small Ernest
Published: September 2008

Aegopodium podagraria, widely cultivated in a variegated form, occasionally gives rise to normal (non-variegated) plants which are comparatively vigorous, exhibiting marked weedy tendencies. Net photosynthetic rates and chlorophyll contents were determined for two populations of normal plants and three populations of variegated plants grown separately under full sunlight, and in shade. None of the populations grown in full sunlight differed significantly from each other in rate of photosynthesis on a leaf area basis, despite the mean 83.5% higher chlorophyll content of normal leaves. However, when grown in shade, on a leaf area basis normal plants averaged 50.1% higher rates of photosynthesis, and 73.5% higher content of chlorophyll, and the leaves were 27.4% heavier than the leaves of variegated plants. These differences apparently are responsible for the competitive advantage of normal plants in the usually shady habitat of A. podagraria.