bluuebunny/crossref_metadata_2025 huggingface dataset:
Size relationships of apical cell and basal cell in two-celled embryos in angiosperms
Authors: Sivaramakrishna D.
Published: May 2008

A mathematical analysis of the relative sizes of the apical and basal cells of 100 published figures of two-celled embryos is used to show that contrary to the contemporary opinion, the size relationships of the two cells are widely varied. Certain factors having a bearing on the size of these cells are discussed.
Imperfect state of Eutypella parasitica in culture
Authors: Johnson David W. , Kuntz James E.
Published: May 2008

Isolates of Eutypella parasitica Dav. and Lor. obtained from mycelial fans, infected bark tissue, and ascospores from different maple cankers produced conidia in culture on most standard media when exposed to light but not in the dark. Hyaline, one-celled, crescent-shaped, spores 1.3–1.8 μm wide and 25–32 μm long were extruded in gelatinous yellow or butterscotch cirri from pycnidiumlike structures or more open labyrinthiform structures which developed within the mycelium. Spores were borne terminally on branched conidiophores. The shape of these spores varied among different isolates. Conidia did not germinate when placed on several media, including host tissue, or when incubated over a wide temperature or pH range. The perfect state was not induced in culture despite various treatments, including incubation of mixed cultures for 2 years.
The ABPHYL syndrome in Zea mays. II. Patterns of leaf initiation and the shape of the shoot meristem
Authors: Greyson Richard I. , Walden David B. , Hume Judith A. , Erickson Ralph O.
Published: May 2008

Microscopic cross sections near the point of leaf initiation document that spiral and decussate leaf arrangements in ABPHYL specimens of Zea mays are the product of altered patterns of leaf initiation. The analysis of seedling meristems also demonstrates that the spiral pattern is generated from meristems having diameters averaging 17% larger than comparably aged normal meristems. The relationship of these observations to phyllotactic models is discussed.
Two new species of Encoelioideae (Helotiales) on western hemlock
Authors: Funk A.
Published: May 2008

Pestalopezia tsugae n.sp. is described from cankered branches of western hemlock (Tsuga heterophylla (Raf.) Sarg.) where it is closely associated with Seiridium abietinum (Ell. and Ev.) Sutton. Nipterella tsugae n.sp. is described from dying, understory branches of western hemlock.
Antheridiogen and the breeding system in the fern genus Bommeria
Authors: Haufler Christopher H. , Gastony Gerald J.
Published: May 2008

Gametophyte morphologies and gametangial sequences in agar cultures of Bommeria species indicated developmental control by an antheridiogen system. The first gametophytes to develop were meristematic and archegonial with ameristic, exclusively antheridial plants appearing later in the same cultures. Bommeria gametophytes were found to form precocious antheridia in response to antheridiogen A but did not respond to antheridiogens B or C. Assays of the native Bommeria antheridiogen indicate that it is an A type antheridiogen hormone and that each Bommeria species responds to the hormone produced by its congeners. Differential response by Bommeria species to dilute antheridiogen may be useful in concert with morphological characters in establishing relationships among species. Spores which establish colonies of unisexual gametophytes and fail to produce sporophytes in monospore culture suggest the presence of an obligately outcrossing breeding system. Such a breeding system, while maintaining genetic diversity, would restrict range extension of the sexually reproducing species. Only the apogamous Bommeria pedata is capable of establishing a new sporophyte plant by a single spore.
The lichen genus Dactylina in North America
Authors: Thomson J. W. , Bird C. D.
Published: May 2008

Four species of Dactylina are reported for North America, including Dactylina beringica sp.nov. Discussions cover the chemistry, descriptions, maps of distribution, and statements of ecology for each species.
The climatology of two succulent plant families: Cactaceae and Crassulaceae
Authors: Teeri J. A. , Stowe L. G. , Murawski D. A.
Published: May 2008

The relative abundance of native species in both the Cactaceae and Crassulaceae in different regions of North America is highly negatively correlated with the coefficient of humidity, an estimate of soil moisture content. The species of both families are relatively more abundant in dry habitats as estimated by this coefficient and other moisture variables. The two families exhibit different patterns of seasonal correlation with the monthly values of the coefficient of humidity. The Cactaceae are most strongly correlated with winter values and the Crassulaceae with summer values. The preferred habitats of the Cactaceae are characterized by high rates of evaporation, while the preferred habitats of the Crassulaceae are characterized by low amounts of precipitation. The species of the Cactaceae are much more highly correlated (multiple R = 0.977) with the combination of moisture and temperature variables that best predict their relative geographic abundance than are those of the Crassulaceae (multiple R = 0.888) with the combination of variables yielding the best prediction of their abundance. It is suggested that the expression of the crassulacean acid metabolism (CAM) phenotype may be of less overall importance to the members of the Crassulaceae of North America than it is to the members of the Cactaceae.
The regulation of potassium influx into intact roots of barley by internal potassium levels
Authors: Glass Anthony D. M.
Published: May 2008

Isotherms were obtained for the influx of K+ into roots of intact barley (Hordeum vulgare (L.) cv. Conquest) plants which had previously been grown in either 0.5 mM CaSO4 solution or 0.5 mM CaSO4 plus 5 mM KGl solution. Km and Vmax values obtained from these influx data were 0.03 ± 0.003 mM and 10.8 μmol g−1 h−1 respectively for the low-K+ plants and 0.1 ± 0.01 mM and 1.74 ± 0.08 μmol g−1 h−1 for the high-K+ plants.When the K+ content of low-K+ plants was increased, by pretreating the roots of intact plants in 10 mM KCl plus 0.5 mM CaSO4 solution, K+ influx values, as determined from 0.1 mM KCl plus 0.5 mM CaCl2 solutions, declined continuously during the 12 h of pretreatment. Hill plots of this data revealed a consistent biphasic response to internal K+. Below 50 μmol K+ g−1 the Hill coefficient was close to unity. Above 50 μmol g−1 the Hill coefficient increased to values close to 3. The time, or root K+ concentration, at which this change in Hill coefficient occurred corresponded to the first indications of net transfer of K+ to the shoot.
Notes on Venezuelan Corticiaceae (Basidiomycetes)
Authors: Liberta Anthony E. , Navas Antonio J.
Published: May 2008

Fifty-seven species of Corticiaceae collected in Venezuela are reported. The genus Rogersella and the species R. asperula are described as new and one new combination is made: Rogersella sambuci.
Characteristics of prescribed burns and resultant short-term environmental changes in Populus tremuloides woodland in southern Ontario
Authors: Smith D. W. , James T. D.
Published: May 2008

In a series of prescribed burns of low intensity and short duration in southern Ontario, wind speed, amount of fuel, and fuel moisture were important environmental controls of fire severity. A heterogenous pattern of burning, related to clumping in the vegetation and to a hummock–hollow microtopography presumably affected and was perpetuated in the reestablishing postfire vegetation.Removal of vegetation cover and surface litter plus surface albedo changes resulted in increased soil temperature 2 months after burning. These increases were short-lived and soil temperatures were close to those of unburned areas 4 months after the prescribed fires. Despite their small magnitude and short duration, the soil temperature increases could have an important stimulatory effect on regenerating vegetation.Significant increases in levels of readily available forms of phosphorus, potassium, calcium, and magnesium at surface soil depths immediately after burning could have been depleted through uptake by vegetation and microorganisms. Portions of the nutrients were removed, also, by erosion of fly ash during burning, leaching to subsurface depths, and through fixation in unavailable form.
Changes in the shrub and herb layers of vegetation after prescribed burning in Populus tremuloides woodland in southern Ontario
Authors: Smith D. W. , James T. D. W.
Published: May 2008

The undisturbed condition in the shrub and herb layers of a Populus tremuloides woodland in southern Ontario was characterized by a mosaic of two main vegetation groupings, one being relatively species rich and the other species poor. Their distribution was related chiefly to two environmental variables: (a) relative degree of shrub canopy cover, and (b) microtopographic position. Species-poor vegetation was associated with those sites having a closed shrub canopy and low, wet positions on the microtopographic gradient.Prescribed burning added a further dimension to the clumped pattern and species richness of the vegetation. Microscale heterogeneity created by the burns tended to increase species richness, but in general, richness was reduced by burning. Rapid postburn changes in the vegetation were largely restricted to shifts in dominance by the three most abundant species; Cornus stolonifera Michx., Calamagrostis canadensis (Michx.) Beauv., and Carex stricta var. strictior Lam. The changes in the dominants after burning appeared to be short lived but affected the overall structure of the shrub and herb vegetation.
Photoperiod and floral-bud development in Caryopteris × clandonensis
Authors: Layzell David B. , Horton Roger F.
Published: May 2008

Floral development in Caryopteris × clandonensis A. Simmonds (C. incana (Houtt.) Miq. × C. mongholica Bunge) from cyme initiation through to anthesis is described, with emphasis on the development of the anthers. The later stages of development and anthesis are completed only on mature plants under short days (SD, 8 h light per day). Under long days (LD, 20 h light per day) senescence occurs in the early stages of anther wall differentiation.
Effect of molybdenum deficiency on the growth and metabolism of corn plants raised in sand culture
Authors: Agarwala S. C. , Sharma C. P. , Farooq S. , Chatterjee C.
Published: May 2008

Molybdenum deficiency decreased the dry matter yield, tissue concentration of molybdenum, and chlorophyll content of corn (Zea mays L. cv. T.41) plants. Compared with the normal (control) plants, leaves of molybdenum-deficient plants had significantly lower activities of nitrate reductase, catalase, aldolase, and alanine aminotransferase and higher activities of peroxidase, β-glycerophosphatase, and ribonuclease. Within 72 h of supplying molybdenum (50 μM) to molybdenum-deficient plants, chlorophyll concentration, soluble protein, and activities of nitrate reductase, catalase, and alanine aminotransferase showed considerable recovery but the increase in the peroxidase activity was further enhanced. Supply of molybdenum to molybdenum-deficient plants did not significantly affect the activity of aldolase, ribonuclease, and β-glycerophosphatase.
Chromosomal proteins of conifers. 1. Comparison of histones and nonhistone chromosomal proteins from dry seeds of conifers
Authors: Pitel J. A. , Durzan D. J.
Published: May 2008

Chromosomal proteins from a wide range of seeds of coniferous species and from provenances of jack pine were characterized by polyacrylamide gel electrophoresis. Histones were resolved into five main fractions. The very lysine-rich F1 histone contained five subfractions. The electrophoretic properties of the nonhistone chromosomal proteins (NHCP) were distinctly different from histones and also from the soluble proteins of the cytoplasm and nucleus. The NHCP fraction contained 18 to 25 protein fractions with molecular weights from 9400 to over 68 000.Histones from nine species of Pinus were similar electrophoretically. Minor differences were noted in mobilities of subfractions of the very lysine-rich F1 fraction. Histones of dry seeds from seven provenances of Pinus banksiana, while qualitatively similar, revealed only minor differences in the percentage distribution of the histone fractions.The relative distributions of the NHCP on discontinuous polyacrylamide gels were different in all seven provenances and in two of the provenances, additional NHCP were present.Comparison of the NHCP of Pinus, Picea, Abies, Pseudotsuga, and Larix species presented a range of quantitative and qualitative differences over and above that found among some species of one genus such as Pinus.
Leucogyrophana (Aphyllophorales): identification of species
Authors: Ginns J.
Published: May 2008

The basidiocarps of nine species are described and the cultural characters are presented for six species. All have pale yellow spores and hyphae with clamp connections and primarily occur on coniferous wood where they are associated with a brown rot. Leucogyrophana arizonica and L. romellii are proposed as new species. Merulius pulverulenta Fr. is transferred to Leucogyrophana. New synonymy is proposed following the study of type specimens and several names previously regarded as synonyms are shown to apply to distinct species.
Salvinia leaves. I. Origin and early differentiation of floating and submerged leaves
Authors: Croxdale Judith G.
Published: May 2008

A study of floating and submerged Salvinia leaves using light and scanning electron microscopy shows unique features in the arrangement of leaves and their growth. Leaves are produced in phyllotactic units of six; within each phyllotactic unit are two sets or groups of three leaves each. The genetic spiral of leaf initiation is not unidirectional but alternates from clockwise to counterclockwise with the production of each group of three leaves. Within each group of leaves, the sequence of primordial expansion is the reverse of their inception. Observations of floating leaf apical cells show that during development they undergo configurational changes from rectangular to hemisperical to lenticular to tetrahedral. Floating and submerged leaves diverge structurally when they are 70–90μm in length. The general course of leaf development appears to differ from previously described ferns and angiosperms in that each floating leaf blade panel is generated from the abaxial primordial surface.
Seasonal dynamics of carbon dioxide exchange in a mixed grassland ecosystem
Authors: Redmann R. E.
Published: May 2008

Carbon dioxide exchange of a mixed grassland sward dominated by Agropyron dasystachyum and A. smithii was measured over two growing seasons using field chambers and infrared gas analysis. Net photosynthesis of the sward began in late April and rose to a peak in early July ([Formula: see text] ground area h−1). Drought during the later part of the summer, a typical feature of the climate of the region, caused net photosynthesis to decline drastically. Air temperature and reduced green leaf area inhibited photosynthesis early and late in the growing season. A multiple regression analysis showed that soil moisture and air temperature together accounted for 44% of the variability in net photosynthesis. Solar radiation and dew-point temperature explained an additional 16%. The ability of the dominant grasses to adapt to fluctuations in water availability is discussed.
Recovery sequence of Picea mariana – Vaccinium uliginosum forests after burning near Inuvik, Northwest Territories, Canada
Authors: Black R. Alan , Bliss Lawrence C.
Published: May 2008

Picea mariana – Vaccinium uliginosum vegetation was sampled in a north–south transect near Inuvik, N.W.T., Canada. Four stages in the postfire recovery sequence were described. Little qualitative change in vascular plants was found in the transect or with time since burning, although quantitative changes were found to exist. Contrary to vascular plant development, an orderly postfire succession of cryptogamic species was found. The postfire recovery sequence by comparison with other open boreal forest studies has a persistent shrub-dominated stage. Burning, with few exceptions, occurred within 100 years of examination along the transect. Objective analyses by Bray–Curtis ordination and reciprocal averaging ordination were used to analyse the vegetation data and proved useful in the data reduction and interpretation of results.
A new species endemic to West Florida: Chrysopsis godfreyi (Compositae–Astereae)
Authors: Semple John C.
Published: May 2008

The new species Chrysopsis godfreyi (Compositae–Astereae), n = 5, is endemic to the Gulf Coast islands of West Florida. The plants are biennial or perennial, forming basal rosettes of woolly, oblanceolate leaves. The species inhabits open sand dunes and in some areas stabilizes the dunes. The plants typically have weakly ascending stems branching near the base, although more erect plants occur in sheltered areas away from salt spray. Two forms occur: the typical one with white woolly stem leaves and one with green, densely stipitate glandular leaves. The species is morphologically similar to Chrysopsis lanuginosa and C. gossypina f. decumbens.
Unusual cell wall layers in elm parenchyma of secondary xylem
Authors: Ouellette G. B.
Published: May 2008

Multilayering of secondary wall layers in American elm parenchyma cells is described. This includes one additional layer like S1–S3 and protective layers each in vasicentric parenchyma and up to two additional such layers in ray parenchyma. These extra layers are comparable with those mentioned by a few other workers, but they are not necessarily related to tylosis formation as implied by some of these.
Protoplasmic incompatibility and self-lysis in Podospora anserina: enzyme activities associated with cell destruction
Authors: Boucherie Hélian , Bernet Jean
Published: May 2008

In the fungus Podospora anserina protoplasmic incompatibility, a phenomenon of cell destruction resulting from the presence in a common cytoplasm of nonallelic incompatible genes, is associated with the appearance of specific proteolytic activities and a phenoloxidase absent from normal cells. We have now shown that during cell lysis, the levels of four additional enzymes increase significantly (3- to 10-fold): a second phenoloxidase, a malate dehydrogenase, a reduced nicotinamide adenine dinucleotide dehydrogenase, and an amino acid oxidase. These increases were inhibited by cycloheximide but unaffected by 5-fluorouracil and actinomycin D or β-phenyl pyruvic acid, an inhibitor of the proteases specific to disintegrating cells. The increase of these four enzymes was shown to be suppressed by mutations in modifier genes known to prevent cell destruction and to inhibit the formation of the proteolytic enzymes.
Additional note: the perfect state of Pyricularia grisea and its allies
Authors: Yaegashi H. , Udagawa S.
Published: May 2008

not available
Phytotoxic action of glyphosate and amitrole on corn seedlings
Authors: Ali A. , Fletcher R. A.
Published: May 2008

The phytotoxic actions of two herbicides, glyphosate and amitrole, were compared using corn seedlings. Six days after treatment with amitrole at 1.68 kg/ha, plant heights, leaf lengths, and shoot fresh weights were reduced 20, 20, and 25% respectively, whereas with glyphosate applied at 1.12 kg/ha the inhibition was 62, 60, and 84% respectively. The lowest concentration of glyphosate (0.28 kg/ha) inhibited plant growth more than the inhibition caused by the highest concentration of amitrole (3.36 kg/ha). A purple colour appeared on the whole shoot of plants treated with glyphosate, and with amitrole, only the new growth of shoots was white. Both treatments reduced chlorophyll levels and the amitrole treatment reduced the carotenoid levels more than the chlorophyll levels. The root growth of plants treated with 1.12 kg/ha glyphosate was inhibited more than 80%, whereas with amitrole at 1.68 kg/ha, the inhibition was 40%. Within 6 h glyphosate severely reduced the rate of root respiration and 12 h after treatment respiration was reduced more than 70%. This rapid effect on root respiration was not observed with amitrole, and even 48 h after treatment, the decrease in respiration was less than 30%. We conclude that the primary site of action of glyphosate in corn seedlings is in the roots whereas the effect of amitrole is in the shoot.
The identification, induction of perithecia, and pathogenicity of Gibberella (Fusarium) tricincta n.sp.
Authors: El-Gholl N. E. , McRitchie J. J. , Schoulties C. L. , Ridings W. H.
Published: May 2008

Fusarium was consistently isolated from leaf spots on English ivy (Hedera helix L.). This Fusarium culture (mass culture) was single spored, and three distinct pigmentation types were evident: brown, red, and white. They appeared to be cultural variants of the mycelial type and were identified as Fusarium tricinctum (Corda) Sacc. Perithecia resulting from pairings of certain combinations of these single-spored cultures, or from the mass culture, were formed on water agar containing cold-sterilized dried stem pieces of coastal Bermuda hay (Cynodon dactylon Pers.). Gibberella tricincta n.sp. is proposed for the binomial of the heterothallic sexual state, which is heretofore undescribed. In vitro inoculation of detached English ivy leaves with ascospores or conidia of the pathogen reproduced the leaf spotting originally observed; however, pathogenicity was very limited under the conditions studied.
Ultrastructural studies on the oil bodies of Marchantia paleacea Bert. I. Early stages of oil-body cell differentiation: origination of the oil body
Authors: Galatis B. , Apostolakos P. , Katsaros Chr.
Published: May 2008

The differentiation of the idioblastic oil-body cells (OBC's) of Marchantia paleacea begins with the formation of protoplasmic and organelle complement in some thallus cells, which are meristematic in appearance. An increase of cytoplasm quantity and density, a proliferation of rough endoplasmic reticulum (ER) membranes, free ribosomes, dictyosomes, plastids, and mitochondria, as well as the appearance of cytoplasmic microtubules and the establishment of ER–plastid relationships were observed especially. These associations, together with the increased cytoplasm quantity, constitute accurate criteria for the identification of very young OBC's.The above protoplasmic changes are accompanied by the cell polarization; the nucleus is displaced at the one end of the cell and the vacuoles at the other end or peripherally. At these stages, the dictyosomes appear active and produce numerous smooth and coated vesicles.Gradually, at a more or less central area free of vacuoles, a number of ER membranes, dictyosomes, and dictyosome vesicles are preferentially localized. Microtubules fan out from this area toward the cell walls. The oil body (OB) appears in the form of a rudimentary 'vacuole,' at the centre of this area. Its bounding membrane is identical with the one of dictyosome vesicles and quite different from the ones of ER and typical vacuoles. Microtubules are associated with its contour, while rough ER membranes may surround it partly. The nascent OB grows further by the fusion of dictyosome vesicles, a phenomenon demonstrated for the coated vesicles and suggested for the smooth ones. The microtubules form a dense framework around the growing OB, while some of them are detected bridged with its limiting membrane. Actually, these microtubules appear to radiate out from the OB and persist until the first stages of lipophilic material elaboration.From the presented observations it is suggested that the OB's originate by the fusion of dictyosome vesicles through a mechanism in which microtubules play a key role. The ER membranes also seem to participate in the development of the newborn OB.
Fomitopsis cajanderi: development in nature and in culture
Authors: Kennedy Lorene L. , Wong William M.
Published: May 2008

In the natural environment and in culture the vegetative mycelium of Fomitopsis cajanderi forms a primordial mat, a basidiocarp primordium, and a sporulating basidiocarp. The fundamental structural unit is the clamped, generative hypha which functions initially in nutrient absorption, then produces unbranched or branched skeletal cells and basidia. and later develops irregularly thickened walls and swollen clamp connections. These structural elements, the brownish-rose color produced by massed skeletal cells, the hymenium of basidia only, and the narrow, slightly curved basidiospores are characters readily observed in the natural basidiocarp and in culture.
Differences in volumes of sister nuclei in binucleate cells: evidence for asymmetry of mitosis
Authors: Davidson D. , Pertens E.
Published: May 2008

Roots of Zea mays cv. Golden Bantam were treated with a 0.1% solution of caffeine for 1–4 h and allowed to recover for up to 17 h. Binucleate cells were present in the root cap and in the meristem; nuclear volumes were determined for the pairs of sister nuclei in the binucleate cells. In row I cells of the root cap, 41%of pairs of sister nuclei had different volumes in roots treated with caffeine for 1–4 h or for 2 h and then allowed to recover for 5 h. In the period 2 + 6 to 2 + 17 h, however, 70% of the pairs differed in volume. Volumes of sister nuclei present in the same cell differ soon after they enter G1; they also differ in the period 2 + 6 to 2 + 17 h when mean nuclear volume increases from 145 to 243 μm3. Both aspects suggest that sister nuclei differ in their ability to grow. In most binucleate cells, the larger nucleus was in the position it would have occupied if it lay in a row I cell. It is suggested, therefore, that a gradient exists, in a row I cell, of some factor that regulates nuclear growth. The consequence of this gradient is that sister nuclei grow differentially even though they share a common cytoplasm. Mitosis in a row I cell appears to be asymmetrical. Cells induced to become binucleate were inhibited by the caffeine treatment. Only 9% of the binucleate cells completed a cell cycle and divided and, for some of them, cycle time was increased.
Organogenèse induite in vitro sur des fragments de racine de Nicotiana tabacum L.
Authors: Hanh Trinh T.
Published: May 2008

Explants taken from superficial epidermic and subepidermic tissues from flowering stocks of Nicotiana tabacum can be induced to flower, produce buds, callus, or roots from a single type of cell, of subepidermic origin. Explants from neoformed roots, when cultivated on media inducing the formation of flowers (IAA 10−6 M, kinetin 10−6 M), buds (IAA 10−6 M, BA 10−5 M), callus (2,4-D 5∙10−6 M, kinetin 10−7 M), and roots (IBA 10−5 M, kinetin 10−7 M) can form buds or callus. New roots are formed when either IAA or kinetin is omitted from the flowering medium. None of the above media induced the formation of flowers from root explants.Temperatures of 22 or 24 °C and the addition of 10−6 M BA were optimal for the de novo formation of buds from root explants. [Traduit par le journal]
Zoospore ultrastructure in the genus Rhizophydium (Chytridiales)
Authors: Barr D. J. S. , Hadland-Hartmann V. E.
Published: May 2008

The zoospore ultrastructure of 12 species of Rhizophydium is described. Species include the following: R. chlorogonii (Serbinow) Jaczewski; R. constantineani Saccardo; R. haynaldii (Schaarschmidt) Fischer; R. capillaceum Barr; two morphologically and cytologically different species, each previously identified as R. sphaerotheca Zopf; R. patellarium Scholz; R. biporosum (Couch) Barr; R. subangulosum (Braun) Rabenhorst; R. laterale (Braun) Rabenhorst; R. sphaerocarpum (Zopf) Fischer var. spirogyrae Barr; and two isolates of R. pollinis-pini (Braun) Zopf. The Rhizophydium zoospore is basically similar to the Chytridium zoospore having (1) the nucleus, a compact cluster of ribosomes, one or more mitochondria, and a microbody – lipid globule complex compartmentalized into the core of the zoospore by a double membrane system and (2) two to five microtubules connecting one side of the kinetosome to the rumposome on the lipid globule surface and thus anchoring the lipid globule in a lateral–posterior position in the zoospore. Rhizophydium patellarium does not have kinetosome-associated microtubules or a rumposome but does have the membrane-bound core area. In all species, a microbody and mitochondrion are associated with the lipid globule. The number of mitochondria varies from 1 in some species to several or to over 30 in other species. In one isolate of R. pollinis-pini, there is 1 large mitochondrion and in the other there were 30–35 small mitochondria. The peripheral cytoplasm of all species contains clusters of vesicles or endoplasmic reticulum which bud from the double membrane system, vesicles of moderate electron density, and vacuoles of various sizes; R. capillaceum, R. patellarium, and R. subangulosum have in addition vesicles which contain very electron-dense material. Rhizophydium capillaceum and R. sphaerocarpum zoospores have virus-like particles and the R. biporosum zoospore contains a paracrystalline body. The taxonomic significance of the observations and the relationship of Rhizophydium to other chytrids are stressed in the Discussion.
Effects of experimental crude oil spills on subarctic boreal forest vegetation near Norman Wells, N.W.T., Canada
Authors: Hutchinson T. C. , Freedman W.
Published: May 2008

Data are presented on the effects of experimental crude oil spills made on two subarctic boreal forest plant communities near Norman Wells, N.W.T. Spray spills of fresh unweathered crude oil at an intensity of 9.1 ℓ/m2 had a general herbicidal effect and caused the death of any green tissue coming in direct contact with the oil. Death of lichens and mosses was rapid and complete. For some higher plants, a considerable lag period occurred between the time of the spill and the time of death (up to 4 years for some individuals of Picea mariana). For others, death occurred during the first winter, with marked effects on cover values in the spring. These effects resulted in large decreases in total plant cover and frequency at spill sites. However, within a few weeks, and in subsequent years, some species developed regrowth shoots. Other species survived as underground rhizomes for a number of years prior to their reappearance above ground (i.e., Equisetum scirpoides). Limited seedling establishment by vascular plants was first observed in the fourth postspill growing season, when some sporeling establishment was also noted for several bryophyte species. No Picea mariana regeneration has occurred in the spill plots in the six postspill growing seasons monitored thus far.Crude oil spills made in winter were found to be less damaging than equivalent summer spills in their short-term biological effects and on rates of recovery and species affected. Initial observations indicate that a summer diesel oil spill shows roughly equivalent toxicity to a summer crude oil spill of the same intensity. Comparisons between an intensive spill (8500 ℓ) made at one point and dispersed spray spills indicate that the former are far less damaging per unit of oil applied to the plant community, with severe detrimental effects being largely limited to areas of direct surface contamination. In the point spill examined, most of the oil percolated downwards and then laterally. Surface vegetation growing above areas with subsurface horizons contaminated by oil was not greatly affected in the first 2 years. An increased area of damage appeared in postspill years 5 and 6, including death of Picea mariana. Oil also appeared to move laterally in 1976 when severe rains occurred, and the oiled area increased somewhat.Limited short-term effects of the spill treatments on depth of active layer thaw have been noted in this study, but these initial effects were not maintained after the first postspill growing season. The low rates of oil application make the conclusions about the effects of large spills on active layer stability conjectural. Potential effects on vegetation are much more firmly based. Oil in the boreal forest soil appeared to retain toxic properties throughout the 5-year study period.
Seasonal dynamics of epiphytic algal growth in a marsh pond: productivity, standing crop, and community composition
Authors: Hooper-Reid Nina M. , Robinson G. G. C.
Published: May 2008

The seasonal growth of epiphytic algae colonizing artificial cellulose acetate substrates positioned in a stand of Scirpus acutus Muhl. and in a zone of Potamogeton pectinatus L. in a marsh pond was quantified in terms of 14C photosynthetic uptake, cell volume, cell surface area, dry weight, and chlorophyll a, protein, carbohydrate, and lipid content. Standing crop and productivity increased at both sites in September and October, after generally low summer growth with the exception of the occurrence of heterocystous blue-green algae at the Potamogeton site in July. Factor analysis of interrelationships among the various parameters suggested that cell surface area was more directly related to productivity and various standing-crop parameters than was cell volume.
L'androcée centripète d’Ochna atropurpurea
Authors: Pauzé Fernand , Sattler Rolf
Published: May 2008

After the inception of usually five sepals and five petals, five primary androecial primordia are initiated as broad bulges in alternation with the narrow petal primordia. On each of these primary androecial primordia, usually seven stamen primordia (i.e., secondary androecial primordia) are formed centripetally in a definite pattern. The fasciculate pattern of the androecium is noticeable only in very early stages of floral development since the stamen primordia of adjacent primary androecial primordia approach each other as closely as the stamen primordia of the same primary androecial primordium. Furthermore, the number and arrangement of the stamen primordia on the primary androecial primordia may vary even within the same floral bud. The total number of stamens per floral bud varied from 26 to 43, while the number of petals varied from 4 to 6. Some of the stamen primordia, especially among the inner ones, sometimes develop into filament-like staminodia. The findings support the view that the Dilleniidae cannot be generally characterized by a centrifugal androecium. The sequence of stamen inception is not necessarily of such fundamental importance that it is a reliable criterion for the reconstitution of major phylogenetic lineages at or above the rank of families. Shifts from a centrifugal to a centripetal androecium or vice versa may have occurred during the evolution of taxa at the ordinal (or even family) level. [Translated by the journal]
On the taxonomy of Monilia roreri, an important pathogen of Theobroma cacao in South America
Authors: Evans Harry C. , Stalpers Joost A. , Samson Robert A. , Benny Gerald L.
Published: May 2008

Monilia roreri Cif., the causal agent of an important pod rot of cocoa in South America, is redescribed and illustrated. The presence of dolipore septa in the vegetative mycelium indicating basidiomycetous affinities and the development of the conidia in basipetal chains necessitate the transfer of the fungus to another genus. The new genus Moniliophthora is proposed. Conidium ontogeny shows similarities with the genera Basipetospora and the anamorph of Blumeria (=Erysiphe).
Ultrastructure of wilt syndrome caused by Verticillium dahliae. V. Attempted localization of phenolic compounds in the vascular region
Authors: Robb Jane , Brisson J. D. , Busch Lloyd , Lu B. C.
Published: May 2008

Ferric chloride has been used in an attempt to detect phenolic compounds at the ultrastructure level in the petioles of chrysanthemums and sunflowers infected with Verticillium dahliae. The fungus contains two types of cytoplasmic structures which stain very densely with ferric chloride; one is similar to a multivesicular body, the other solid and apparently spherical. In treated chrysanthemums, the ferric ion accumulates mainly in vessel plugs, in laminar arrays or localized diffuse deposits in the secondary walls of vessels, in vasicentric parenchyma cells, and the protective layer of parenchyma cells immediately adjacent to the vessels. In treated sunflowers the ferric ion accumulates mainly in vessel plugs, in the pectinaceous layers of the cell wall (i.e. middle lamella and primary cell walls), and in the vasicentric parenchyma cells. Differences in the pattern of phenolic deposition in the two hosts could account wholly or in part for differences in symptom expression.
Two new Hyphomycetes from Venezuela
Authors: Crane J. L. , Dumont K. P.
Published: May 2008

Brachysporiella dennisii sp. nov. and Hyalocylindrophora venezuelensis gen. et sp. nov. are described and illustrated from material collected on the 1971 and 1972 Flora Neotropica expeditions to Venezuela.
Contribution to the Aphyllophorales of the Canary Islands. 4. Two new species of Trechispora and Xenasmatella
Authors: Ryvarden Leif , Liberta Anthony E.
Published: May 2008

Trechispora canariensis and Xenasmatella odontioidea are described as new.
Nitrogen fixation associated with Scirpus atrovirens and other nonnodulated plants in Massachusetts
Authors: Kana Todd M. , Tjepkema John D.
Published: May 2008

Nitrogen fixation was measured using the acetylene reduction technique in soil cores of 13 nonnodulated, herbaceous plant species growing in mesic and wetland habitats. Six species that grew in a well-drained portion of an old field exhibited low rates of N2 fixation (7 g N∙ha−1∙day−1). A bulrush, Scirpus atrovirens, which grew in an area of compacted soil in the old field, showed a moderate rate of N2 fixation (30–100 g N∙ha−1∙day−1). These old field species exhibited a lag of only a few hours before a constant rate of acetylene reduction occurred. The estimated rates for the six wetland species were generally higher, and there was a lag such that the activity was still increasing after 20 h of incubation. N2 fixation in cores of S. atrovirens was primarily associated with the roots and adhering soil. Incubation of the cores in N2 for 24 h caused a fourfold increase in the acetylene reduction rate over that in air, although the rates during the first 4 h were similar.
Growth of Macrocystis integrifolia in Barkley Sound, Vancouver Island, B.C.
Authors: Lobban Christopher S.
Published: May 2008

Stipe elongation rates were measured over an 18-month period which included one normal summer and one in which there was unusually heavy epiphytism and defoliation. Calculated standard growth rates (G) followed atypical boreal pattern, rising in February through April, with a summer maximum of ca. 40 mm/day, and falling in October and November. This contrasts with M. pyrifera in southern California, which has G ca. 70 mm/day throughout the year. The maximum number of fronds that could be produced in the growing season by a frond series of M. integrifolia is about 20, but the number actually produced is 8; many frond initials are lost through grazing or abrasion or may be suppressed by high frond densities.
Structure of a stem-derived callus of Ruta graveolens: meristems, leaves, and secretory structures
Authors: Peterson R. L. , Scott M. G. , Ellis B. E.
Published: May 2008

Differentiation in a stem-derived callus of Ruta graveolens was studied by correlated light and electron microscopy. Shoot apical meristems, some of which initiated leaves, differentiated randomly at the surface of the callus. Some of the apical meristems had a tunica–corpus organization. Cells of the tunica and corpus had large nuclei with prominent nucleoli, small vacuoles, mitochondria, endoplasmic reticulum cisternae, and leucoplasts. The leaves were radial and had well developed stomata and chloroplasts of two types, one storing large starch grains and the other with no starch but with well developed grana. Lysigenous and schizolysigenous secretory glands were initiated in the leaves and towards the periphery of the callus. Central cells in the lysigenous glands underwent lysis forming a gland lumen into which lipid-like material from the degenerating cells was released. During early stages of cell lysis, breakdown of the middle lamella occurred, followed by the degeneration of cell walls. The lipid-like deposits are thought to be the essential oils known to be produced by these callus cultures. Schizolysigenous glands are formed by the separation of gland cells along the middle lamella and the subsequent development of an epithelial layer or layers surrounding a gland lumen. The cytology of epithelial cells was characterized by numerous ribosomes and the presence of plastids with lipid-like deposits, rough endoplasmic reticulum which occurred either as sheets of cisternae or tubular profiles, and osmiophilic deposits in the cytoplasm. Changes in the epithelial cell walls bordering on the gland lumen indicated that these cells were probably undergoing lysis in older stages of gland development.
Effects of highway deicing agents on Thuja occidentalis in a greenhouse
Authors: Foster A. C. , Maun M. A.
Published: May 2008

Greenhouse studies showed that eastern white cedar (Thuja occidentalis L.) exhibited yellowing and necrosis of foliage and browning of roots in response to high salt concentrations in soil and nutrient solution. Foliar spray showed injury symptoms to the foliage but the root system was not affected. Water stress as measured by water saturation deficit of the leaves also increased with increased concentration of salt in the soil. The damage to white cedar foliage occurred when the concentration of Na was 3 mg/g (0.3%) of dry matter. The toxic concentration of Cl was 8 mg/g (0.8%) of dry foliage. White cedar trees grown in muck soil treated with salt exhibited less injury than those grown in loam, sandy, or greenhouse soils receiving the same treatment.
An open-circuit apparatus for continuous determination of net ion uptake by seedlings grown hydroponically
Authors: Caldwell C. D. , Fevre P. E. Le , Aikman D. P.
Published: May 2008

An apparatus is described which can monitor the depletion of ions from a solution bathing intact Zea mays roots continuously and with accuracy. It can routinely detect changes in ion concentration of less than 0.1%. Its use in an experiment involving leaf illumination supports the theory that a low supply of photosynthate in the root may limit the rate of ion uptake.
Biosynthetic and cytological studies in tissue cultures and regenerated plants of haploid Atropa belladonna
Authors: Eapen Susan , Rangan T. S. , Chadha M. S. , Heble M. R.
Published: May 2008

Tissue cultures have been established from leaves of one anther-derived haploid plant of Atropa belladonna L. Regenerants obtained from callus cultures were transferred to soil and reared to maturity. Callus cells and regenerants exhibited variable degrees of ploidy. The frequency of different ploidy levels in both the systems did not vary significantly during fifth to eighth serial passages.Callus tissue and regenerated plants (at flowering stage) were analyzed to determine the concentration of tropine, atropine, scopolamine, and total alkaloids. While the alkaloid content in callus cultures was very low (0.8 × 10−3%), the regenerated plants contained different levels of individual and total alkaloids. The ploidy of the plant had direct bearing on the individual and total alkaloid contents.
Chlorophyll fluorescence induction: an indicator of photosynthetic activity in marine algae undergoing desiccation
Authors: Wiltens James , Schreiber Ulrich , Vidaver William
Published: May 2008

Algae of higher intertidal regions tend to be tolerant of extended periods of desiccation, while many lower tidal or subtidal species do not withstand even mild water loss. (Tidal regions can be characterized as high (regularly immersed at high tide and exposed at low tide), low (emergence only during minus tides (lower than mean low tide)), or subtidal (never exposed at low tide and extending to the maximum depth at which net photosynthesis can occur).) The ecological necessity for tolerance in frequently emerged species is obvious, but the physiological basis of it is not well understood. Changes of photosynthetic partial reactions upon desiccation and rehydration of tolerant and sensitive algae were studied by measurements of chlorophyll fluorescence induction kinetics (Kautsky effect). With progressive decrease in water content the gradual disappearance of the characteristic fluorescence transients was observed in both tolerant and sensitive species. The water content ranges where typical changes occurred were species dependent. Rehydration in tolerant plants resulted in rapid recovery from severe desiccation; there was no such recovery in sensitive plants when water content was decreased below a critical value. Analysis of the fluorescence changes upon desiccation and rehydration suggests: (1) electron transport between photosystem II and photosystem I, as well as H2O splitting are the partial reactions sensitive to desiccation; (2) in the resistant Porphyra sanjuanensis, intersystem electron transport is blocked at around 25% water content; (3) further desiccation leads to loss of water-splitting activity and eventually to the complete loss of variable fluorescence photosystem II reaction centers; and (4) on rehydration intersystem electron transport begins almost immediately while recovery of H2O splitting requires several minutes.
Fine structure of mistletoe pollen. I. Eremolepidaceae, Lepidoceras, and Tupeia
Authors: Feuer Sylvia , Kuijt Job
Published: May 2008

An examination of pollen morphology and ultrastructure of Eremolepidaceae (Antidaphne, Ixidium, Eremolepis, Eubrachion) and Lepidoceras by light and scanning and transmission electron microscopy reveals a close relationship among the taxa. Pollen of Eremolepidaceae is typically echinate, tricolporate, and oblate-spheroidal. Eubrachion is unique within the family, exhibiting shallowly reticulate pollen. Ultrastructurally, all Eremolepidaceae exhibit a similar exine structure. The sculptural ektexinous elements (spines or 'muri') are never contiguous with the basal ektexine but rest on a thin granular zone. Pollen characters of Lepidoceras are particularly close to those of Ixidium and Eremolepis. The porate (por(or)ate) aperture type, completely spherical shape, and reduced granular ektexine of Lepidoceras pollen indicate an advanced position within the complex. The relationship of Tupeia to Eremolepidaceae is more obscure as pollen of the genus exhibits both eremolepidaceous (echinate sculpturing, shape in polar and equatorial views) as well as loranthaceous characters (simple apertures, ektexine organization). Palynologically Eremolepidaceae and related genera show no particular close relationship to Olacaceae or Santalaceae. Though Eremolepidaceae et al. do share a number of pollen features with Viscaceae (echinate sculpturing, compound apertures, exine organization) the strong nonpalynological differences between the two families suggest that these pollen features may have arisen independently.
Ultrastructure of basidiospore germination in Fomes fomentarius
Authors: Tsuneda Ichiko , Kennedy Lorene L.
Published: May 2008

Germination of basidiospores in Fomes fomentarius (Fries) Kickx is bipolar with germ tubes emerging at both ends. Ungerminated spores are smooth with a thick cell wall consisting of two layers: an outer thin, electron-dense layer and an inner thick, electron-light layer. During the early stage of germination, two additional cell wall layers are formed: a very thin, electron-dense layer and a relatively thick, electron-light layer. Germ tube walls originate from these newly formed, inner layers. Ungerminated spores are uninucleate and contain numerous lipid bodies, ribosomes, and cisternae of endoplasmic reticulum. Germinated spores have distinct mitochondria and an invaginated plasma membrane and are usually devoid of endoplasmic reticulum.