bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of abscisins and 3-indolylacetic acid in leaves of Sorghum bicolor by high performance liquid chromatography
Authors: Durley Richard C. , Kannangara Tissa , Simpson Graham M.
Published: May 2008

The growth regulators abscisic acid (ABA), phaseic acid, dihydrophaseic acid, and 3-indolylacetic acid (IAA) have been detected and the levels were measured in extracts of leaves from Sorghum bicolor using high performance liquid chromatography (HPLC). For purification of extracts, columns contained 37- to 75-μm-diameter octadecylsilica. For analysis of the growth regulators, microoctadecylsilica columns were used. Both columns were used in the reverse phase mode. The efficiency and resolution of the microcolumn combined with the high sensitivity of the ultraviolet absorption microcell detector could accurately determine as little as 2 ng of ABA and 6 ng of IAA. The method is suitable for routine analysis of levels of regulators in moderately large numbers of plant extracts.
An autecological study of Blidingia minima var. subsalsa (Chlorophyceae) in the Squamish estuary (British Columbia)
Authors: Prange Robert K.
Published: May 2008

The autecology of the estuarine alga, Blidingia minima var. subsalsa (Kjellman) Scagel (Chlorophyceae) was considered with regard to its distribution and abundance in the Squamish River estuary, British Columbia, Canada, by integrating a multifactorial laboratory study and field data.Increases in abundance of Blidingia were associated with brackish waters, high light intensity, high air temperature, moderate desiccation, and possibly, favourable ion ratios. The upper limit of vertical distribution appeared to be associated with unfavourable osmotic conditions, e.g., heavy rain or extreme desiccation, and the lower limit with low light intensities. Horizontal distribution was limited by absence of seawater on the freshwater side and high salinities on the marine side.The periods of highest and lowest field abundance of Blidingia compared favourably with the laboratory combinations which produced the highest (20‰, 20 °C, 50 μg-at ℓ−1 N and 5.0 μg-at ℓ−1 P) and the lowest photosynthetic rates (0.25‰, 5 °C at all N and P concentrations) respectively.
New taxa and nomenclatural changes with respect to Vascular Plants of British Columbia: A Descriptive Resource Inventory
Authors: Taylor Roy L. , MacBryde Bruce
Published: May 2008

A number of nomenclatural changes were required for the presentation of the descriptive resource inventory of vascular plants of British Columbia. Documentation and discussion of these changes are presented. Additional notes and discussion are provided for some taxa presenting unusual problems in the British Columbia vascular plant flora, and several new taxa are described.
Comparative ultrastructure of the haustoria in uredial and pycnial infections of Puccinia coronata avenae
Authors: Harder D. E.
Published: May 2008

The haustorial apparatus in uredial infections of Puccinia coronata in Avena sativa was essentially similar to that reported elsewhere for the cereal rusts. Further evidence was obtained that membranes of some host cytoplasmic vesicles were continuous with the invaginated host plasmalemma.The intracellular structure in pycnial infections of P. coronata in Rhamnus cathartica remained confined to and established a long-term relationship with the host cell, thus qualifying it as a ‘haustorium’ (designated P haustorium). However, the P haustoria were less specialized than uredial haustoria and differed from them in the following ways: (1) the P haustorium mother cell did not appear to be attached to the host cell, and there was no localized thickening of the fungal wall at the penetration site; (2) there was no specialized penetration peg; (3) an ingrowth of host wall-like material formed in advance of the penetrating fungus, and the remnants of the ingrowth later formed a collar around a necklike portion of the P haustorium; (4) there was no well differentiated neck and no neck ring; (5) the P haustoria were very irregular in shape with sharply contoured outlines and were occasionally septate; (6) the P haustorial protoplasts were more densely staining and contained large amounts of lipid and glycogen storage material; (7) there was an irregularly occurring sheath around the P haustoria; and (8) the host vascular tissue was invaded by both intercellular and intracellular growth in pycnial infections.
Root growth in corn and soybeans: effects of cadmium and lead on lateral root initiation
Authors: Malone Carl P. , Miller Raymond J. , Koeppe D. E.
Published: May 2008

This study examines the previously reported inhibitory effects of Cd on root growth. In hydroponic experiments, 100 μg Cd/ℓ effected a 33% inhibition of lateral root initiation of corn. The growth of corn and soybean primary roots was not reduced at Cd concentrations of 1 mg/ℓ, and the number of lateral root initials in soybeans was not reduced at 2 mg Cd/ℓ. The toxic effects of Cd were ameliorated by additions of Zn or by additions of Fe citrate to nutrient growth solutions. While both Zn and Fe additions did result in increased lateral root initiation, the number of initials was significantly lower than the controls. Lead had no effect on the initiation of soybean lateral roots at a concentration of 100 μg Pb/ℓ. However, 5 mg Pb/ℓ did effect a 21% decrease in corn lateral root initials, but this decrease could not be demonstrated with higher Pb concentrations.
Flow in xylem vessels and Poiseuille's law
Authors: Giordano R. , Salleo A. , Salleo S. , Wanderlingh F.
Published: May 2008

We measured water flow in simple xylem vessels of Sechium edule at various pressures. We found a disagreement with Poiseuille's law, which changes from vessel to vessel and becomes abruptly pronounced in some cases. We discuss our data in terms of an 'impediment coefficient,' K. It can be shown that the total flux in a stem, calculated as the sum of the flux in single vessels, agrees quite well with the data reported in literature.
Photosynthesis of eggs, sperm, zygotes, and embryos of Fucus serratus
Authors: McLachlan J. , Bidwell R. G. S.
Published: May 2008

Eggs, sperm, zygotes, and embryos of Fucus serratus L. fixed 14CO2 in light. Based on a visual estimation of sample size, eggs had a somewhat higher rate of photosynthesis than sperm. The rate for eggs declined with time but increased on fertilization. The rate of photosynthesis in embryos increased rapidly during the first days of their growth. Eggs and particularly sperm tended to produce more amino acids than embryos, whose products of photosynthesis were similar to those found in mature plants.
Influence of parental rye on the development of embryos and endosperm of wheat–rye hybrids
Authors: Taira T. , Lelley T. , Larter E. N.
Published: May 2008

Seven lines of rye (Secale cereale L.), six inbred (S9) and one open-pollinated, were used as pollen parents in crosses with two tetraploid wheat strains (Triticum turgidum var. durum cvs. 'Jori' and 'Langdon'). The rye lines were of diverse genetic background and exhibited significant differences in meiotic stability as measured by frequencies of chiasmata and univalent formation. The rate and extent of development of the embryo and endosperm tissue of hybrid ovules were not influenced by the level of meiotic stability of the rye parent, but rather by a genetic interaction between a specific rye genotype and wheat. This was indicated by the significant differences obtained in the frequency of normal embryo formation when different rye lines were used as parents in crosses to a common wheat cultivar. The specific effect of the wheat genotype on the mean seedset was shown by the significant differences obtained when different wheat cultivars were crossed with a given set of rye genotypes under the same environmental conditions. The prevailing ambient temperature significantly affected hybrid embryo and endosperm development in vivo.
Seasonal nutrient and sodium accumulation in the macrophyte Pontederia cordata
Authors: Bayly I. L. , Shibley M. E.
Published: May 2008

A seasonal study of accumulation of calcium, magnesium, sodium, potassium, and phosphorus was made on Pontederia cordata L., an important component of wetlands in North America. Twice weekly sampling of soil and plant material was made from May 23, 1975, to September 23, 1975. Results were analysed using the prepared program POLYFIT TSL, which fits a curve to the data and prepares an R2 value (coefficient of multiple determination) for the data. Positive correlations between seasonal growth events of P. cordata and accumulation of individual ions were obtained from the analysis. In addition, a positive correlation between accumulation of ions and changes of ion concentration in the upper horizon of the soil was detected for potassium and magnesium.
Southern Australian Tertiary epiphyllous fungi, modern equivalents in the Australasian region, and habitat indicator value
Authors: Lange R. T.
Published: May 2008

Various Lower Tertiary epiphyllous microfungi are described from southern Australia, including the monotypic new genus Cribrites aurea and the new species Callimothallus australis. Modern equivalents were searched for in 72 leaf-litter samples from Australasia. The habitat indicator value of the fossils is assessed by comparison with the geographic, climatic, and vegetational relationships of the modern forms.
A new technique for manipulating host–parasite interactions by low speed centrifugation
Authors: Waterman Margaret A. , Aist James R. , Israel Herbert W.
Published: May 2008

An apparatus and a method for centrifuging living, inoculated plant tissues were developed for studies of a cytoplasm-related host response of barley coleoptiles to penetration by the powdery mildew fungus Erysiphe graminis hordei. When the coleoptiles were attached to the apparatus with the long axes of the cells parallel to the centrifugal force, cytoplasm-rich and cytoplasm-poor zones were produced, permitting simultaneous comparisons of interactions in the presence or absence of host cytoplasm. The inner epidermis was inoculated and centrifuged for 12–14 h at 4750 × g. Desiccation was prevented by addition of liquids at the cut end of each coleoptile; the rest of the coleoptile was dry and suitable for inoculation with E. graminis conidia. Of the host cells, 50–80% had well-compacted cytoplasm, conidia developed penetration and infection structures, and the host response was restricted to cytoplasm-rich zones and was shown to be cytoplasm-dependent. Cytoplasmic streaming resumed within 10 min after centrifugation stopped, and 90–100% of the epidermal cells were actively streaming 3 h later. This centrifugation method could be adapted and applied to studies of the other host–parasite interactions.
Assessing stress in Rhododendron macrophyllum through an analysis of leaf physical and chemical characteristics
Authors: Gholz H. L.
Published: May 2008

Exposure to full sun provided the most stressful environment, as reflected by foliar characteristics, for naturally occurring Rhododendron macrophyllum growing at low to middle elevations. However, for a given age, exposed plants had a greater woody biomass than shaded plants. In comparison with shaded plants, foliar chemical concentrations (as percentage dry weight) were greatly reduced, unit-area concentrations were greatly increased, total leaf area per plant was reduced about half, and average leaf areas and specific blade areas were greatly reduced. Exposed plants also lacked almost totally the normal fourth age class of foliage.Reduced temperatures and growing-season length, associated with shaded sites at high elevation, caused intermediate levels of stress. This was indicated by intermediate unit-area measurements of foliar chemical concentrations, total leaf area per plant, average leaf size, and specific blade area. Percentage dry weight concentrations did not differ significantly from those of other shaded plants. Foliar biomass per plant was similar for the high-elevation site and the exposed site. Woody biomass of shaded plants at high elevations was similar to that of shaded plants at low elevations.Results showed that the dimensional characteristics of leaves (average leaf area, specific blade area), the total leaf area per plant, and foliar chemical concentrations expressed on a unit-area basis were the foliar characteristics most accurately reflecting stressful environments.
Nectar secretion in excised flowers. V. Effects of indoleacetic acid and sugar supply on distribution of [14C]sucrose in flower tissues and nectar
Authors: Shuel R. W.
Published: May 2008

Movement and distribution of [14C]sucrose was studied in snapdragon flowers cultured on sucrose solutions in relation to the timing and extent of the characteristic reduction of nectar yield by 1AA, the question of whether IAA acts in the nectary cells or by reducing sugar movement to the nectary, and competition for sugar between nectaries and other tissues.There was a 50% reduction in accumulated nectar yield in flowers treated with IAA within 18 h; thereafter, the capacity to secrete nectar was virtually abolished. Within 6 h, IAA caused a significant increase in the incorporation of 14C into protein. Most of the 14C activity lost to nectar in flowers treated with IAA was recovered in the ethanol-soluble materials and protein of the flowers. Radioactivity continued to accumulate in the secretory tissue after secretion had stopped. The percentage reduction in nectar by IAA was not diminished under conditions of minimal growth and sugar transport distance. It was concluded that IAA acts on the secretory process in the nectary cells rather than on movement of sugar to the nectary.The influence of differences in sugar supply appeared mainly in the distribution of 14C activity between peduncles and nectar: as sugar supply was increased, a smaller percentage remained in the peduncles and a larger percentage was secreted. The secretory process competed strongly with floral tissues for sugar even when the latter were undersupplied.
Recruitment and survival of seedlings of a perennial Hieracium species in a patchy environment
Authors: Johnson Christine D. , Thomas A. G.
Published: May 2008

Observations on a population of Hieracium piloselloides Vill. in an old-field habitat revealed two distinct microsites on which seeds might land, bare soil and moss-covered areas. Regular monitoring of newly emerged seedlings on both microsites revealed that the seeds could germinate as soon as they are shed and that emergence of the seedlings coincided with rainfall, forming distinct emergence flushes. The number of emergences and losses recorded on the bare soil sites always exceeded those which occurred on the moss-covered microsites. The greatest losses of seedlings from the population occurred in periods of low rainfall. The mortality in six seedling cohorts was also followed on these plots. Similar patterns of survival were shared by most of the bare soil cohorts and by all cohorts of moss-covered soil, but the decline in the bare soil cohorts was always more rapid. The number of seeds available in the natural seed rain is estimated to be 40 190 seeds/m2. To this, a total of 120 000 seeds/m2 were added artificially in marked plots, and from the recorded emergences, the establishment success of seedlings was estimated at less than 1%. It is suggested that in terms of monthly microclimatic variation, both types of microsite may be of value in contributing to the apparent stability of the population.
A taxonomic study of the large-glumed species of Stipa (Gramineae) occurring in Canada
Authors: Barkworth Mary E.
Published: May 2008

The morphology and awn anatomy of the large-glumed species of Stipa occurring in Canada were examined. Numerical analysis of the data indicates that S. spartea var. spartea and S. spartea var. curtiseta are very distinct taxa differing not only in many of their quantitative characters but also in nodal pubescence, ligule shape, and pubescence of the leaf margin. It is proposed that they be treated as separate species, S. spartea and S. curtiseta. Some evidence was found for differentiation within S. spartea s.s. but it was deemed insufficient for the recognition of infraspecific taxa. Stipa comata var. comata and S. comata var. intermedia are very similar in all morphological characters examined. Cross sections of their distal awn segments do, however, show consistent distinguishing characters; those of var. intermedia are more heavily lignified and tend to be square in outline compared with those of var. comata. Although similar to each other, cross sections of the varieties of S. comata are distinct from those of S. spartea and S. curtiseta. The possibility that certain specimens were hybrids between S. comata var. comata and S. curtiseta was explored and rejected. Distribution maps and a key to the accepted taxa are given.
Xylem ethylene, phenol-oxidizing enzymes, and nitrogen and heartwood formation in walnut and cherry
Authors: Nelson Neil D.
Published: May 2008

In black walnut sapwood, ethylene production, in vitro, near the heartwood boundary peaks early in the dormant period and is low while the cambium is active. In black cherry, ethylene production in the heartwood–sapwood transition zone peaks during the middle to the late growing season and is greater than in the middle and the outer sapwood during early dormancy. In walnut, in vitro peroxidase (EC 1.11.1.7) activity near the heartwood boundary peaks during the late growing season to the early dormant period and is greater than in the adjacent sapwood regions. In both species, ethylene production correlates with peroxidase activity. In vivo tyrosinase (EC 1.10.3.1) and peroxidase activities are relatively high near the heartwood boundary during dormancy. Laccase (EC 1.10.3.2) is absent from the heartwood boundary region. Total nitrogen levels reach a minimum during the dormant period. General phenological biochemical trends suggest that in both species dormancy is a time of major heartwood formation. Heartwood formation in walnut apparently is minimal when cambial activity is greatest. Walnut phenotypes that differ in heartwood-formation class, a measure related to sapwood–heartwood ratio, also differ in sapwood peroxidase activity. In cherry sapwood, ethylene production and total nitrogen are related to heartwood formation class.
Genera coelomycetum. XIV. Allelochaeta, Basilocula, Ceuthosira, Microgloeum, Neobarclaya, Polynema, Pycnidiochaeta, and Xenodomus
Authors: Raj T. R. Nag
Published: May 2008

The generic names Allelochaeta, Basilocula, Ceuthosira, Pycnidiochaeta, and Xenodomus are shown to be redundant. Allelochaeta and the single species A. gaubae are reduced to synonymy with Seimatosporium and S. dilophosporum, respectively. Basilocula, Ceuthosira, and Xenodomus are treated as synonyms of Coleophoma with C. lauricola, C. aesculi, and C. taxi proposed as new combinations. The names Microgloeum and M. pruni are shown to be applicable to a microconidial state associated with Cylindrosporium padi. The generic name Neobarclaya is revived to accommodate N. primaria and is segregated from Polynema in which P. ornatum and P. radiatum comb. nov. are accepted. Pycnidiochaeta and its type species, P. biciliata, are reduced to synonymy with Dinemasporium and D. gramineum, respectively.
Genera coelomycetum. XV. Belaina, Belainopsis, and Crucellisporium
Authors: Raj T. R. Nag , Kendrick B.
Published: May 2008

The type species of the Coelomycete genera Belaina Batista & Peres and Belainopsis Batista & Maia were illustrated by their original authors as having conidial fructifications and stauroconidia resembling those subsequently described for Crucellisporium Farr (one basal arm, two or three apical arms) and therefore offered a possible earlier name for that genus. We demonstrate that the conidia of Belaina and Belainopsis can actually be ascribed to Polynema (two or three basal appendages, one apical appendage). A new species of Crucellisporium is described and the type species is redescribed.
Nuclear condition, types of hyphal development from differentiating, and nondifferentiating uredosporelings, and effect of 3,3′-bis-indolylmethane on Puccinia graminis f.sp. tritici in vitro
Authors: Grambow Hans J. , Müller Dietmar
Published: May 2008

In vitro Puccinia graminis f.sp. tritici, race 32, produced dikaryotic hyphae from infection structures, corresponding to appressoria and substomatal vesicles (differentiated), which are formed by germ tubes as a response to a heat shock within 24 h after seeding the spores. Dikaryotic hyphae also formed spontaneously from nondifferentiated senescing germ tubes 3–4 days after seeding the spores. The hyphae which originated from the different structures did not appear to be different with regard to nuclear condition, morphological appearance, and fluorescence properties as a consequence of Feulgen staining. 3,3′-Bis-indolylmethane (BIM) increased the hyphal growth rate in contrast with the germ tube growth rate. It also supported the transition from germ tube growth to hyphal growth. The possible mode of action of BIM and the involvement of an unknown factor which represses hyphal growth are discussed.
Functional significance of the nodal constricted zone in Populus deltoides
Authors: Larson Philip R. , Isebrands J. G.
Published: May 2008

A zone of minimum vessel number and vessel cross-sectional area (the constricted zone) occurs in the nodal region of each of the three vascular traces serving a leaf of Populus deltoides Bartr. When the area data are transformed to Σr4, they can be used in the Poiseuille equation to estimate hydraulic conductivity. The decrease in xylem conductivity frequently observed at vascular junctions, such as the nodal constricted zone, may be accounted for by a restriction in hydraulic conductivity.
Forests dominated by hemlock (Tsuga canadensis): distribution as related to site and postsettlement history
Authors: Rogers Robert S.
Published: May 2008

Along a transect of mature forests from Wisconsin to Nova Scotia, hemlock attains dominance most frequently where soil is thin or low in stored nutrients. Very probably, soil is also dependably moistened either by climate or seepage. The inability of shade-tolerant competitors to survive suppression on thin or infertile soil may explain hemlock's success, even though hemlock maintains understory populations at very low densities. Hemlock also grows well on moist uplands with richer soil but does not often attain dominance or form large aggregates in a continuously varying mixed forest. This is in contrast to hemlock's codominance on a wide variety of upland sites in the presettlement forest. Recent history, then, may best explain the rarity of hemlock-dominated stands on richer sites: (1) hemlock is sensitive at all stages of its life cycle to disturbances that were intensified after European settlement as well as to the kinds of animal consumption that increase with disturbance; (2) disturbance has been most frequent on sites with richer soils; and (3) hemlock does not compete well with shade-tolerant trees such as sugar maple, beech, and red spruce that are better adapted to disturbance. These species can increase at the expense of hemlock because they have less rigorous requirements for seedling establishment, are not as palatable to consumers, or, in the case of sugar maple and beech, have deeper root systems and can sucker or sprout after extensive shoot damage.
Starch accumulation in bundle sheath chloroplasts during the leaf development of C3 and C4 plants of the Gramineae
Authors: Miyake Hiroshi , Maeda Eizo
Published: May 2008

Nonphotosynthetic starch accumulation in chloroplasts is examined by light microscopy during the leaf development of several C3 and C4 grasses and compared between mesophyll and bundle sheath cells. In Oryza sativa, Phragmites communis (C3 grasses), and Cynodon dactylon (C4 grass), bundle sheath chloroplasts accumulate large amounts of starch in the early stages of the leaf development, while in other grasses, both mesophyll and bundle sheath chloroplasts accumulate only small amounts of starch. It is suggested that bundle sheath chloroplasts of starch-accumulating species, regardless of their photosynthetic characteristics, are specialized in the accumulation and supply of storage starch during the leaf development.
Medullary tissue culture of the red alga Chondrus crispus
Authors: Chen L. C.-M. , Taylor A. R. A.
Published: May 2008

Techniques were developed for the isolation and axenic culture of medullary tissue explants from female gametophytic fronds of Chondrus crispus Stackh. When a strain with narrow thick branches was grown in vitro in a special, enriched seawater medium with added growth regulators, the colourless medullary tissue explants (2-mm cubes) produced fronds exhibiting the normal morphology of the parent plant.
The flagellar apparatus in the Chytridiales
Authors: Barr Donald J. S. , Hadland-Hartmann Victoria E.
Published: May 2008

The flagellar apparatus is described in zoospores of Rhizophydinm chlorogonii, R. constantineani, R. haynaldii, R. laterale, R. patellarium. R. pollinis-pini, R. sphaerotheca, R. subangulosnm, Phlyctochytrium plurigibbosum, Chytridium confervae, C. olla, C. lagenaria, Rhizoclosmatium globosum, and Rluzophlyctis rosea, which are all members of the order Chytridiales. In fine structure, the flagellar apparatus is basically similar to that of fungi in other orders of the class Chytridiomycetes. The characteristics of the flagellar apparatus which are unique to the class are: (1) kinetosome props and associated segment of doublets with a curved extension seen as a hook in thin sections; (2) a spiral structure which connects to the A tubules of the doublets and coils in the core of the transition zone. These characteristics distinguish this class of fungi from the Oomycetes, from algae, protozoa, and other eukaryotes. It is further proposed that six modifications to the flagellar apparatus within the Chytridiales are diagnostic characteristics which could be used for describing subgroupings within the order. These modifications are the presence of a fibrous rhizoplast in some species; presence and form of electron-dense inclusions in the basal area; arrangement of kinetosome-associated microtubules; presence of an electron-dense area in the base of the flagellum; the angle of the nonfunctional centriole to the kinetosome and the presence of a veil-like structure on the side of the nonfunctional centriole. Taxonomic implications of these findings are discussed.
Host range of the smut species Ustilago nuda and Ustilago tritici in the tribe Triticeae
Authors: Nielsen J.
Published: May 2008

Thirty-seven species of the genera Aegilops, Agropyron, Elymus, Eremopyrum, Haynaldia, Hordeum, Secale, and Taeniatherum in the tribe Triticeae and six species of the genus Lolium in the tribe Festuceae were tested for their reaction to loose smut of barley, Ustilago nuda, and loose smut of wheat, U. tritici. One new host for U. nuda was found: Hordeum violaceum. Fifteen new hosts for U. tritici were found: Aegilops caudata, Ae. ovata, Ae. triuncialis, Agropyron caninum. A. fibrosum, A. scabrifolium, Elymus canadensis, E. dahuricus, E. virginicus. Haynaldia villosa, Hordeum brachyantherum, H. jubatum, H. marinum, Secale silvestre, and Taeniathernm crinitum. Six new hosts for both U. nuda and U. tritici were found and they are the first known common hosts for these fungi: Agropyron scabriglume. A. striatum, A. tsukushiense var. transiens, Hordeum bogdanii, H. brevisubulatum, and H. compressum. On all these hosts, the sori of U. nuda were covered by a thin membrane or peridium whereas the sori of U. tritici were naked. Spores formed on all hosts germinated in the manner typical for the species used for inoculation. The wild barley common in Canada. Hordeum jubatum, differentiated between races of loose smut of wheat, U. tritici. Six species of Lolium were resistant to U. nuda and U. tritici.
Trace metal dynamics in decomposing leaf litter in habitats variously influenced by coal strip mining
Authors: Lawrey James D.
Published: May 2008

In a 20-year-old abandoned surface coal-mining area in eastern Ohio, fiber-glass litterbags containing thalli of two cryptogam species and leaves of 10 dominant tree species were set out in four vegetated stands influenced to varying degrees by the impact of strip mining. Decomposition rate of the litter types studied was correlated with the soluble carbohydrate, ash, and macronutrient fractions of the litter. No effects of strip mining on litter decomposition were apparent in any of the vegetated stands.Metal elements (Mn, Fe, Al, Cu, Zn, and Mo) were found to accumulate in decomposing litter with time. The degree to which dominant metals (Mn, Fe, and Al) were lost or accumulated with time was significantly correlated with the initial metal content of litter, indicating that a cation-exchange process is probably involved in observed metal-mobilization patterns.Leaching experiments using distilled water acidified to pH5.5 with H2SO4 to simulate rainfall in this region revealed that litter types which exhibited generally high decomposition rates or high initial amounts of metals tended to lose metal elements as a result of leaching. Metal-mobilization patterns evident from the litter-decomposition experiment indicated that the 1st month of litter decomposition results in metal loss owing to leaching.
Pollen morphology in the genus Myriophyllum (Haloragaceae)
Authors: Aiken S. G.
Published: May 2008

Pollen size and aperture number are reported for nine North American species of Myriophyllum. For seven of these, scanning electron micrographs are provided. The wall sculpture of M. alterniflorum is microrugulate and that of eight other species is microverrucate. In M. exalbescens and M. tenellum, microvermcae develop late in pollen maturation. Myriophyllum farwellii, a species that flowers underwater, has asymmetrically arranged pores and variation in pore number. An estimated 90% of M. farwellii pollen, from collections made in 1975 and 1976, had collapsed: the apparently sterile grains suggest that this species is at least partly apomictic. A pollen key to the species is provided.
Ecological studies on the epipelic algal community in five prairie–parkland lakes in central Alberta
Authors: Hickman Michael
Published: May 2008

Seasonal fluctuations of the epipelon in five eutrophic, prairie–parkland lakes were characterized by spring and late summer – autumn maxima, although midsummer peaks, dominated by chlorococcalean algae, occurred at the shallow stations in three lakes. Winter peaks were invariably dominated by algae of planktonic origin. The epipelon was light limited at the deep stations under ice cover during the winter. More correspondence than in previous studies was found between the standing crop and the nutrient status of the overlying water but no one single factor could account for seasonal fluctuations of the epipelon. Instead, a combination of light levels, nutrients, temperature, physical disturbance, and biotic interactions affected these fluctuations. The mean standing crop size of the epipelon was closely related to the mean bicarbonate levels.
The Zygorhynchus zygosporangium and zygospore
Authors: O'donnell K. L. , Flegler S. L. , Ellis J. J. , Hesseltine C. W.
Published: May 2008

Zygosporangium and zygospore formation in Zygorhynchus was followed by scanning and transmission electron microscopy. One or more slender, lateral zygophoric filaments proliferate from the subterminal portion of a septate, erect hypha. These lateral zygophoric branches recurve and conjugate with the stout, terminal zygophoric hypha. Heteromorphic gametangia are delimited asynchronously on either side of the fusion wall. Deposition of wart material on and within the inner primary wall layer is concomitant with fusion septum dissolution. The mature zygosporangial wall is composed of electron-opaque stellate, confluent warts with an elaborate ornamented inner surface. The potential taxonomic value of mature zygosporangium and zygospore topography in Zygorhynchus is examined.
Electron-probe microassays for silicon in the roots of Sorghastrum nutans and Phragmites communis
Authors: Sangster A. G.
Published: May 2008

Nodal roots of field specimens of Sorghastrum nutans (L.) Nash exhibited Si deposition confined exclusively to the endodermis in the form of nodular silica aggregates. Si distribution in this species is compared with that for other genera within the tribe Andropogoneae, and the possible function of Si in the root is discussed.Phragmites communis Trim, in contrast, exhibited no consistent accumulation of Si in the nodal root. The variations in Si accumulation between the two species are interpreted in relation to their root anatomy and differing habitat characteristics.
Concentration of highway deicing agents along roadsides near London
Authors: Foster A. C. , Maun M. A.
Published: May 2008

Analysis of snow and soil samples showed that the concentrations of Na and Cl were higher near the road and decreased with increasing distance from the pavement. The level of calcium in soil did not change with distance. The concentration of calcium in the foliage of eastern white cedar trees (Thuja occidentalis L.) facing the highway was not significantly different from the concentration in the foliage on the opposite side. The filter paper discs attached to the foliage accumulated significantly high amounts of salts on days with freezing rain or snow storms. A strong correlation was found between element levels in the foliage and the levels found in filter paper discs.
Further theoretical analysis of concentration–pressure–flux waves in phloem transport systems
Authors: Ferrier Jack M.
Published: May 2008

Theoretical results show that waves involving complex interactions between osmotic pressure, hydrostatic pressure, and fluxes of water and solute can occur in any phloem transport system surrounded by a semipermeable membrane. These results show that such waves can travel from sugar sink to sugar source as well as from sugar source to sugar sink. The time-dependent sugar concentration variation is shown to be caused largely by the time-dependent variation of the gradient of mass flow velocity in the sieve tube which is produced by the time-dependent variation of water flux across the membrane. This water flux variation is produced by a slight phase difference between osmotic and hydrostatic pressure variation. It is proposed that this phenomenon be called the concentration–pressure–flux (CPJ) wave.
Identification of chromosome segments controlling the synthesis of peroxidases in wheat seeds and in transfer lines with Agropyron elongatum
Authors: Kobrehel K.
Published: May 2008

The genes coding the synthesis of the three major cathodic isoperoxidases a, c, and d in common wheat cv. Chinese Spring, as determined by polyacrylamide slab gel electrophoresis, are located on the chromosome arms 7DS, 4BL, and 7AS, respectively. Transfer lines with Agropyron elongatum can be detected by electrophoretic analysis of peroxidases if the chromosome arm 7AgS is involved in these transfers. Results have also shown a homology between the chromosome 7D of common wheat and the chromosome 7Ag of Agropyron elongatum.
Endogonaceae from Quebec soils
Authors: Herskowitz Joan M. , Estey R. H.
Published: May 2008

Spores of the Endogonaceae, isolated from soils in the vicinity of Macdonald College, P.Q., included those of the following species: Glomus mosseae (Nicol. & Gerd.) Gerd. & Trappe, G. macrocarpus var. geosporus (Nicol. & Gerd.) Gerd. & Trappe, G. caledonius (Nicol. & Gerd.) Gerd. & Trappe, and Acaulospora laevis Gerd. & Trappe. Sporocarps of Sclerocystis rubiformis Gerd. & Trappe were also found.The ectocarpic spore population was lowest in May or June. It increased in late summer, reaching a peak in September or October.
Germinability of sclerotia of Macrophomina phaseolina
Authors: Ayanru D. K. G. , Green Jr. R. J.
Published: May 2008

The germination of sclerotia of Macrophomina phaseolina from 3- to 20-day-old PDA cultures incubated at 32 °C and 24 °C varied from 98 to 25% and 75 to 30%, respectively. Germinability of sclerotia from cultures of all ages tested was rapidly lost during storage in desiccators for 24 h at 6 °C or in screw-top vials at room temperature for 30 days. Germination of sclerotia stored in screw-top vials at 6 °C for 30 days declined less rapidly. There was a linear relationship between the size of the sclerotium and the number of germ tubes emerging from it. The role of sclerotium size in survival and what factors may be responsible for loss of germinability with increasing age of source culture are discussed.
Stimulation of Fusarium graminearum by maize pollen
Authors: Naik D. M. , Busch L. V.
Published: May 2008

Maize pollen stimulated infection of maize by Fusarium graminearum Schwabe both in in vivo and in vitro. Significant increases in percentage germination of macroconidia and length of germ tube of F. graminearum occurred in the presence of pollen dialysate, while dextrose and sucrose were not as stimulatory. All concentrations of macroconidia used to inoculate greenhouse-grown maize plants were equally effective in producing lesions in the leaf axils in the presence of pollen. Without pollen, only the highest inoculum concentration was effective and then only half as many lesions were produced. In a survey of two fields, over 90% of the maize plants had lesions in their leaf axils similar to those induced in greenhouse-grown plants. Reduction in dry weight of detached maize silks inoculated with three different spore concentrations was greater in the presence of pollen than in its absence.
Byssoporia gen. no v.: taxonomy of the mycorrhizal fungus Poria terrestris
Authors: Larsen Michael J. , Zak Bratislav
Published: May 2008

Poria terrestris (DC. per Fries) Sacc., recently discovered to be mycorrhizal with roots of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and western hemlock (Tsuga helerophylla (Raf.) Sarg.), is separated into five distinct varieties. Separation is based on color of basidiocarps, morphology of rhizomorphs, cultural characteristics, color reactions of tissues to chemotaxonomic reagents, differences between respective Douglas-fir mycorrhizae, and fluorescence of tissue under ultraviolet (UV) (3600 Å (1 Å = 0.1 nm)). Byssoporia, a new genus, is proposed for P. terrestris and its varieties.
Application of compatibility analysis in numerical cladistics at the infraspecific level
Authors: Baum Bernard R. , Estabrook George F.
Published: May 2008

Compatibility analysis was applied to a set of evolutionary units (EUs) whose true cladogram is known. These EUs consisted of 16 Avena cultivars. The results show great differences between the true cladogram and the generated trees. Very few characters were found to correctly reflect the cladistic relationships among the 16 EUs. An attempt is made to explain this discrepancy, and as a result, a number of unanswered questions are raised.
The zoospore of Synchytrium endobioticum
Authors: Lange Lene , Olson Lauritz W.
Published: May 2008

An ultrastructural study of the zoospore of the obligate plant parasitic chytrid Synchytrium endobioticum (Schilb.) Perc., the causal agent of potato wart disease, is presented. The uniflagellate zoospore of S. endobioticum is characterized ultrastructurally by (1) an even distribution of the ribosomes, (2) one large, anteriorly located lipid globule, (3) mitochondria that are gathered around the nucleus. (4) cytoplasmic microtubules associated with the functional kinetosome, (5) an extensive sheet of endoplasmic reticulum partially encapsulating most of the cellular organelles, and (6) a structure which may resemble a contractile vacuole. The ultrastructure of the zoospore of S. endobioticum is discussed in relation to other chytridiaceous zoospores studied; it is concluded that among the Chytridiales, differences in zoospore ultrastructure exist between species within the same genus (e.g., Phlyetochytrium) that are as great as those observed between different genera and even different families.
Contribution of overwintering leaves to the growth of three broad-leaved, evergreen shrubs belonging to the Ericaceae family
Authors: Reader R. J.
Published: May 2008

Individual leaves of three bog ericads, leatherleaf (Chamaedaphne calyculata), bog laurel (Kalmia polifolia), and Labrador tea (Ledum groenlandicum), were retained for a maximum of two growing seasons in a peat bog in southern Ontario. The premature loss of mature leaves, resulting from artificial defoliation, significantly reduced the growth of new shoots of L. groenlandicum and K. polifolia but not of C. calyculata. Defoliation effects were directly proportional to the normal retention time for overwintering leaves. Mature leaves probably translocate photosynthate, nitrogen, and phosphorus to other plant parts. This would explain why leaf dry weights were greatest at the start, rather than at the end, of the leaves' second growing season. Net photosynthetic rates decreased with leafage, but in terms of leaf nitrogen content, new and old leaves fixed equal amounts of carbon.
Etude ultrastructurale de la gamétogenèse mâle dans une espèce à floraison cléistogame: Oxalis corniculata, suivie de quelques considérations générales sur la cléistogamie
Authors: Pargney J. C.
Published: May 2008

In male gametophytes of chasmogamous and cleistogamous flowers of Oxalis corniculata, the development of the tube cell at the ultrastructural level shows that gametogenesis is almost the same in both cases: the dictyosomes, in particular, go through an inactive period accompanied by an intense production of microvesicles. This rest phase, present in pollen grains of numerous Angiosperms, is thus well marked in the two types of flowers. However, the similarity between the two types of gametogenesis is less obvious with regard to cell reserves: in pollen grains of cleistogamous flowers, starch formation is slightly retarded. At maturity, they contain numerous starch grains comparable with those found in chasmogamous flowers. In both types of flowers, the generative cell of the mature gametophyte gives rise to two sperms.Earlier studies on male gametogenesis in chasmogamous and cleistogamous flowers of Streptoearpus nobilis and Viola sp. compared with results on Oxalis corniculata show that cleistogamy determines more or less strongly the ontogeny of pollen grains as well as the morphology of the vegetative and floral parts. Thus, different degrees of cleistogamy exist from very specialized states (Streptocarpus nobilis) to very little modified ones (Oxalis corniculata).
Organogenesis and chromosome number in callus derived from cassava anthers
Authors: Liu Ming-Chin , Chen Wen-Huei
Published: May 2008

Experiments have been performed to induce callus formation and organogenesis in anther culture of cassava (Manihot esculenta Crantz). Callusing was achieved on a modified Murashige and Skoog medium (MSB) supplemented with 4.44 μM 6-benzylaminopurine (BAP) and 4.52 μM 2,4-dichlorophenoxyacetic acid (2.4-D). No callus was formed from anthers pretreated at 4 °C for more than 48 h or on a medium containing 4g/ℓ activated charcoal. Callus on MSB with 4.44–8.88 μM BAP alone formed roots only. BAP (8.88 μM) in combination with α-naphthalene acetic acid (NAA) (10.74 μM) resulted in chlorophyll formation in callus. Abscisic acid (ABA) acted as an antagonist to NAA in reducing the frequency of callus greening when the latter was applied jointly with BAP. Chromosome counts of mitotic figures from callus cells ranged from 34 to 38 indicating that the calli were derived from the somatic tissues of the anthers.
Analysis of the genetic complexity of a hybrid plant
Authors: Jiménez Estela Sánchez de , Willerer Alejandro Otto Meyer
Published: May 2008

Nuclear DNA from wheat, rye, and Triticale plantlets was isolated and purified. Purity of the samples was tested spectrophotometrically. Tm values and hyperchromicities were determined for the three DNA samples. The DNA(s) were denaturated and annealed under controlled conditions. Cot curves were carried out for total DNA on the three samples and for the repetitive DNA fractions.The analysis of those curves indicated that the genomes of wheat and rye are made of highly repetitive, intermediate, and unique DNA fractions. The highly repetitive fraction (107) is suggested as corresponding to palindrome areas in the genome.The Triticale genome showed a similar pattern to the parents, except for the highly repetitive DNA fraction which showed different orders of repetitiveness.
Capture of nematodes by Arthrobotrys oligospora, an electron microscope study
Authors: Nordbring-Hertz Birgit , Stålhammar-Carlemalm Margaretha
Published: May 2008

The capture of nematodes by Arthrobotrys oligospora consists of (1) firm adhesion of the nematode to the capture organ, (2) penetration of the nematode cuticle by a penetration hypha, and (3) digestion of the nematode. Penetration of the nematode cuticle by a penetration hypha originating from the trap took place within 1 h after addition of nematodes to a fungal culture and occurred at any point on the nematode surface. Vegetative hyphae were able to invade an immobilized nematode only through the body orifices (8–12 h after addition of nematodes to fungal cultures lacking traps). The presence of prey caused an increased secretion of adhesive from the trap. Scanning electron microscope micrographs show a captured nematode covered by a mucilaginous coat. In transmission electron microscope micrographs of thin sections, a distinct osmiophilic layer between trap and nematode is always present. Since penetration occurred at the point of deposit of these substances, it is suggested that the osmiophilic layer also has enzymatic activity. An osmiophilic layer was never seen around vegetative hyphae, indicating the lack of both adhesive and similar enzymes.The traps contained numerous membranous electron-dense vesicles (150–300 nm) not present in hyphae. Large osmiophilic inclusions (1–2 μm) were more common in traps at certain stages of development than in hyphae. The results indicate that the adhesive and the digestive enzymes originate from either or both of these organelles.
Development and ultrastructure of the marine, parasitic oomycete, Lagenisma coscinodisci (Lagenidiales): encystment of primary zoospores
Authors: Schnepf E. , Deichgräber G. , Drebes G.
Published: May 2008

The primary zoospores of Lagenisma contain many peripheral "encystment vesicles." They disappear when the primary cyst wall is formed. The primary cyst wall consists of a 6-nm-thick, electron-dense layer and is secreted in less than 1 s. Ten seconds later, the flagella are retracted in the "straight-in way" within 3–4 s. The cyst bears spines which initially are filled with cytoplasm. They do not seem to contain cytoskeletal elements and possibly are shaped by a locally restricted extension of the cytoplasm and the cyst wall when the latter is formed. Later on, a secondary, inner, thicker fibrillar cyst wall layer is secreted. In contrast with other developmental stages studied hitherto, the vegetative primary cyst contains microbody-like structures.