bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of copper, nickel, and zinc tolerances in four grass species
Authors: Rauser Wilfried E. , Winterhalder E. Keith
Published: April 2011

Clones of Agrostis gigantea, Deschampsia caespitosa, Hordeum jubatuin, and Poa compressa were evaluated for their tolerance with respect to copper, nickel, and zinc. Most of the plants originated from acidic, copper- and nickel-contaminated soils near Sudbury, Ont. Metal tolerance was assayed by measuring all of the adventitious roots growing from tillers but excluding lateral roots. Tolerance of copper, nickel, and zinc was evident in the four clones of D. caespitosa originating from Sudbury. One clone of A. gigantea originating from a roast bed showed tolerance of copper, while none showed tolerance of cither nickel or zinc. One clone of P. compressa from Sudbury indicated increased tolerance of copper and nickel, yet its root growth was inhibited at lower zinc concentrations than that of a companion clone from Sudbury and a control. The H. jubatum plants showed no tolerance of any of the metals. Copper was most toxic to all of the species, followed by nickel and then zinc.
A new chytridiomycete parasitizing the tardigrade Milnesium tardigradum
Authors: Dewel Ruth Ann , Joines Jerry D. , Bond John J.
Published: April 2011

The life cycle of a chytridiomycete, Sorochytrium milnesiophthora gen. et sp. nov., infecting the tardigrade Milnesium tardigradum, is described. The zoospores are posteriorly uniflagellate and ovoid, and possess a central mass similar to a nuclear cap. To initiate an endobiotic infection they attach to the cuticle of the host, encyst, and generate an appressorium. The appressorium forms a penetration tube which crosses the cuticle to the epidermis and enlarges at the tip into a spherical thallus. Concomitantly, vacuoles replace the cytoplasm of the cyst and appressorium. As the thallus enlarges, it moves into the body cavity and cleaves into segments. The segments separate and round up into incipient sporangia. The incipient sporangia develop branching rhizoids in conjunction with host death. After a period of growth the sporangia form inoperculate exit papillae which penetrate the host cuticle. Zoospores exit individually and fully formed. The fungus can develop a polycentric phase when freshly collected, dead hosts containing sporangia are cultured in habitat water or on nutrient agar. The growth is extramatrical, covering the surface of the old host. It is rhizoidal, branching, and nonseptate with numerous intercalate incipient sporangia bearing rhizoids. On nutrient media the thallus grows indefinitely while in habitat water the incipient sporangia mature and discharge motile spores. The spores frequently have two to five flagella and are larger than those of the endobiotic colonial phase. A similar polycentric growth develops when motile spores are isolated on nutrient medium and suggests that the extramatrical growth on the host originates from encysted spores.
Laticifers and latex in fruits of periwinkle, Catharanthus roseus
Authors: Eilert U. , Nesbitt L. R. , Constabel F.
Published: April 2011

Light and electron microscopic observation of laticifers in fruits of periwinkle, Catharanthus roseus (L.) G. Don, revealed cells which after fixation showed an abundance of droplets in vacuoles. The droplets have a rough surface and are electron dense. A comparison of cytoplasm of laticifers and neighboring parenchyma cells indicated varying degrees of degradation of organelles. Degradation visibly affects the nuclei, plastids, and mitochondria. Latex contains electron-dense droplets and some vesiculated cytoplasm with highly degraded organelles interspersed. Vindolinine and 19-epivindolinine, but not vindoline, were found to be the main alkaloids of periwinkle fruit latex.
Hormonema merioides n.sp., on Douglas-fir needles
Authors: Funk A. , Woods T. A. D. , Hopkinson Sarah J.
Published: April 2011

Hormonema merioides n.sp. is described from needles of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) in British Columbia, Canada, where it is associated with a needle blight.
A monographic revision of the genus Myriosclerotinia
Authors: Schumacher Trond , Kohn Linda M.
Published: April 2011

The genus Myriosclerotinia (Helotiales, Sclerotiniaceae) is redefined to include only those species producing tuberoid sclerotia within the culms of host plants, not producing a disseminative conidial anamorph, producing a Myrioconium microconidial anamorph within locules in the culms of host plants, and developing an apothecial microanatomy characterized by an ectal excipulum composed of inflated angular to globose cells and a medullary excipulum of granularly roughened prosenchymatous cells. The taxonomy and nomenclature of 34 epithets which have been referred to Myriosclerotinia, or which have been suspected by us or by other authors as possibly belonging there, are reviewed. Nine species are retained in the genus: M. scirpicola, M. caricis-ampullaceae, M. curreyana, M. dennisii, M. duriaeana, M. juncifida, and M. longisclerotialis; M. sulcatula (=M. sulcata (Whetzel) Buchw.) and M. luzulae are described as new. Eight epithets are placed in synonymy under accepted species, 5 are treated as imperfectly known, and 12 epithets are excluded and either assigned to other genera or accepted in generic accommodations made by other authors.
A comparison of seedling vigour in crop and weed biotypes of proso millet (Panicum miliaceum)
Authors: Moore Dwayne R. J. , Cavers Paul B.
Published: April 2011

Three groups (weed, eroplike weed, crop) of proso millet (Panicum miliaceum L.) which vary extensively in seed size and colour were used in a series of experiments to compare their seedling vigour and rates of germination. It was found that greater seed size, lack of seed dormancy, and greater seedling vigour occurred in the crop and croplike weed biotypes. Further, the growth rates of the three groups were similar, and hence most differences in seedling vigour among biotypes resulted from dissimilar seed weights. Several previous studies on other species had shown that seed weight and seedling growth rates were negatively correlated (thus, initial seed size differences would not persist to maturity) and the relationship between those results and ours is discussed. Also, regeneration strategies within a species for both crops and weeds are discussed from an evolutionary point of view.
Efficiency in a forest nursery of an ectomycorrhizal fungus inoculum produced in a fermentor and entrapped in polymeric gels
Authors: Tacon F. Le , Jung G. , Mugnier J. , Michelot P. , Mauperin C.
Published: April 2011

In a nursery in the centre of France, we have compared the effect of different forms of an ectomycorrhizal fungus inoculum (Hebeloma cylindrosporum) on growth and mycorrhizal development of Douglas-fir and Norway spruce after soil fumigation. Compared with inoculum produced on peat and vermiculite, the inoculum produced in a fermentor and entrapped in polymeric gels significantly improved Douglas-fir and Norway spruce seedling growth. The Hebeloma mycorrhizal index was not significantly different between the different forms of inocula. The superiority of the inoculum produced in the fermentor and entrapped in gels is probably related to the high metabolic activity of the mycelium and to the protection given by the polymers after the incorporation of the inoculum into the soil. Hebeloma cylindrosporum stimulates seedling growth even in the presence of Thelephora terrestris mycorrhiza.
Toxicity of soil-applied fungicides and gypsum to the vesicular–arbuscular mycorrhizal fungus Glomus mosseae in groundnut
Authors: Parvathi K. , Venkateswarlu K. , Rao A. S.
Published: April 2011

The effects of four commonly used commercial formulations of contact fungicides (pentachloronitrobenzene, captan, captafol, and mancozeb) and gypsum on the vesicular–arbuscular mycorrhizal development of Glomus mosseae (Nic. & Gerd.) Gerd. & Trappe in groundnut were studied. Drenching the soil with pentachloronitrobenzene or gypsum at the time of seed sowing significantly inhibited the colonization and sporulation by the fungus; the other fungicides were less toxic. Captan, a widely used fungicide, was least inhibitory on development of the fungus. Pentachloronitrobenzene, gypsum, and captafol treatments significantly reduced the plant biomass.
Protein synthesis in flax following inoculation with flax rust
Authors: Sutton Ben C. S. , Shaw Michael
Published: April 2011

Resistance to flax rust Melampsora lini (Ehrenb.) Lév. in flax carrying the N resistance gene is determined by 24 h postinoculation, at which time hypersensitivity is observed. We have examined protein synthesis in cotyledons inoculated with both virulent and avirulent races of rust by in vivo labelling with [35S]methionine. The pattern of protein synthesis was assessed by one- and two-dimensional electrophoresis 8, 13, and 18 h after inoculation. No changes in protein synthesis were observed in the first 14 h following inoculation; however, by 18 h after inoculation the susceptible combination showed a marked decrease in protein synthesis (22%; P = 0.01). This could be largely accounted for by the reduced synthesis of the ribulose 1,5-bisphosphate carboxylase large subunit, which was readily quantified on electrophoresis gels. In addition, a 30-kDa polypeptide also declined in the susceptible combination. Two-dimensional electrophoresis enabled changes to be detected in the synthesis of other minor polypeptides. None of these changes were observed in the resistant combination in which a small increase in the synthesis of the ribulose 1,5-bisphosphate carboxylase large subunit and the 30-kDa polypeptide was found. These results indicate that the outcome of the host–pathogen interaction has already been determined by 18 h after inoculation.
Evaluation of the actual evapotranspiration model of decomposition at a subalpine surface coal mine
Authors: Parsons W. F. J. , Durall D. M. , Parkinson D.
Published: April 2011

Percentages of original dry mass lost annually and single exponential decay rates (k) for timothy (Phleum pratense L.) leaf litter decomposing on three reclaimed subalpine mine spoil plots (7, 3, and 1 years old) in Alberta, Canada, were compared with values predicted using generalized equations devised by Meentemeyer on the basis of an annual regional average of actual evapotranspiration (Thornthwaite) and a site-specific value (Christiansen). Measured decay rates on the more heavily vegetated plots (3 and 7 years old) were similar to k values predicted using Christiansen actual evapotranspiration values, while the decay rate on the plot with the least amount of vegetation cover (1 year old) was much greater than k values predicted using Christiansen or Thornthwaite actual evapotranspiration values. The actual evapotranspiration model severely underestimated annual percentage mass losses, regardless of whether Thornthwaite or Christiansen actual evapotranspiration values were used.
Effectiveness of protective agents for increasing activity of five enzymes from vegetative tissues of white spruce
Authors: Pitel J. A. , Cheliak W. M.
Published: April 2011

Optimal conditions of pH and substrate concentration for five enzymes from crude extracts of needle and bud tissue of a white spruce (Picea glauca (Moench) Voss) tree were first investigated, and then used for subsequent experiments. With increasing age of the needles on the tree, activity of peroxidase increased, while that of 6-phosphogluconic acid dehydrogenase and ferredoxin-NADP+ reductase decreased. Polyethylene glycol increased enzyme activity from needle tissue. For isocitrate dehydrogenase and glucose-6-phosphate dehydrogenase, 2% polyethylene glycol was most effective, while for 6-phosphogluconic acid dehydrogenase, 4% was best. Enzyme activity also varied considerably with the pH of the extraction buffer. Extraction of needle and bark tissues with various combination buffers referred to in the literature clearly indicated that no one extraction buffer was optimal for all five enzymes of this study. Unlike that of needle and bark tissues, enzyme activity of bud tissues was high even in the absence of any protective agent. The effect on enzyme activity of storage of the bud extracts for 10 days at 4 °C varied with the enzyme.
Thermal acclimation of photosynthesis by the arctic plant Saxifraga cernua
Authors: Mawson Bruce T. , Svoboda Josef , Cummins Raymond W.
Published: April 2011

The thermal acclimations of net photosynthesis, dark respiration, and photorespiration have been studied in the arctic plant Saxifraga cernua. The gas exchange of whole plants grown to maturity under different temperature regimes was analysed for individual plants transferred from (i) 10 to 20 (referred to as high-temperature acclimation) and (ii) 20 to 5 °C (low-temperature acclimation). High- and low-temperature acclimation resulted in shifts of the leaf temperature optimum for net photosynthesis of whole plants in the direction of the new growth temperature. That the acclimating temperature directly affected the photosynthetic apparatus was indicated by (i) changes in the optimum temperature for gross photosynthesis of whole plants and (ii) a change in the oxygen sensitivity of net photosynthesis after acclimation to a new growth temperature. The change in the optimum temperature for net photosynthesis was also due, in part, to altered dark respiration rates which increased during acclimation to low growth temperatures. These results suggest that such acclimation in arctic species like S. cernua arose as a result of the selective pressure of fluctuating temperatures which are experienced during the growth season to maximize annual growth under arctic and subarctic conditions.
Phenolic metabolites of Ceratocystis minor from laboratory cultures and their effects on transpiration in loblolly pine seedlings
Authors: DeAngelis J. D. , Hodges J. D. , Nebeker T. E.
Published: April 2011

Several low molecular weight phenolic metabolites of Ceratocystis minor (Hedgcock) Hunt, a blue-stain fungus of loblolly pine, were isolated from cultures grown on 2.5% malt-extract liquid medium. The most abundant compounds were 6,8-dihydroxy-3-hydroxymethyl isocoumarin and 6,8-dihydroxy-3-methyl isocoumarin. Two unknown phenolic compounds were also isolated. Solutions of these fungal metabolites stimulated transpiration in loblolly pine seedlings when administered through the cut stem. Rates of water loss were doubled within 24 h after treatment with isocoumarin solutions. Administration of raw or sterile fungal culture (in liquid medium) on the other hand produced a small but significant inhibition of water loss shortly after treatment. Reduction in transpiration after treatment with fungal culture probably is the result of partial tracheid blockage by as yet unidentified fungal products. Effects of metabolites of C. minor on the water relations of loblolly pine are discussed in terms of a possible mutualistic association between C. minor and the southern pine beetle, Dendroctonus frontalis Zimmermann.
The ultrastructure of Ulothrix mucosa. I. Mitosis and cytokinesis
Authors: Lokhorst G. M.
Published: April 2011

For the most part, the fine structure of the cytokinetic apparatus of Ulothrix mucosa Thuret has been found to possess distinctive ulvophycean features including initiation of the cleavage furrow when the nucleus is still in interphase, replication of the lateral centrioles at prophase and their changed position near the polar fenestrae of the broad metaphase spindle pole, the semiclosed condition of the nuclear envelope throughout most mitotic stages, and the rapid completion of the cleavage furrow following restoration of the interphase condition in daughter nuclei. However, outstanding characteristics reminiscent of the typical chlorophycean pattern are also found, including the frequent presence of a microtubular system, which appears to be most distinct in the final developmental stage of the cleavage furrow, and the quick descent of the sets of centrioles along the telophase nuclei until they are close to the cleavage plane opposite each other, which is particularly reminiscent of a chlorococcalean behaviour. Comparison of the fine structure of the cytokinetic apparatuses within Ulothrix reveals variation in the pattern of deposition of cell wall material onto the intervening new septum, and in the biogenesis of the ingrowing plasmalemma. It is stated that comparative cytological analyses which show cell variability at the generic level (as in Ulothrix) continue to be useful and are needed before recommendations may be made as to the validity of the modern green algal classifications in use today.
New foliicolous hyphomycetes from India
Authors: Narayan P. , Kamal
Published: April 2011

Four foliicolous hyphomycetes, viz., Bioconiosporium berberidis sp. nov., Pithomyces divaricatus sp. nov., Scolecobasidium trichoides sp. nov., and Tretospora indica sp. nov., collected on living leaves of Berberis asiatica Roxb., Casearia tomentosa Roxb., Ficus hispida Linn., and Randia longispina DC., respectively, in different forests of Uttar Pradesh State in India, are described and illustrated.
Sur la variabilité de la capacité rhizogène d'explantats racinaires de Cichorium intybus (var. Witloof) cultivés in vitro : influence de la dimension des explantats initiaux et de la durée de conservation des racines au froid
Authors: Vasseur Jacques , Lefebvre René , Backoula Enoch
Published: April 2011

On Cichorium intybus root explants of different size, it is possible to demonstrate the existence of a relation between the volume/surface ratio and adventitious root formation capacities. With a volume/surface ratio equal to one, the highest number of adventitious roots and percentage of explants able to produce roots have been observed. When this ratio deviates from unity, adventitious root formation declines. Cold storage of chicory roots causes breakdown of fructosans and accumulation of sucrose, glucose, and fructose. At the same time, adventitious root formation on explants cultured in vitro decreases. Inclusion of glucose in culture media increases adventitious root production whatever the duration of chicory root cold storage may have been. Results are discussed and the hypothesis of a regulation of adventitious roots by sucrose and reducing sugars is advanced.
Composition du nectar et rôle des nectaires extrafloraux chez l'Ailanthus glandulosa
Authors: Bory Gérarad , Clair-Maczulajtys Danielle
Published: April 2011

The composition of the extrafloral nectar from Ailanthus glandulosa varies according to the type of nectary. When the buds open, those which are located on the cataphylls or the stipules are only supplied by carbohydrate reserves. In this case, a high sucrose content is found in the nectar, and rhamnose is also detected. The floriferous or sterile state of the trees does not modify the sugar composition of the foliar nectar. For amino acids, the predominance of serine, threonine, and proline is constant in all types of nectars. The amount of proline is very important in the nectar of the cataphylls and increases with the age of the leaf. The activity of the foliar nectaries seems to correlate with the occurrence of a requirement for photosynthetic products. The nectaries from trees developing fruits or from those showing only vegetative growth continue to be functional for a long time. The ablation of foliar nectaries leads to a sugar accumulation in the leaf and slows down the reconstitution of starch reserves in the branch. The function of the extrafloral nectaries is interpreted as being the elimination of excess sugars. Thus, the initiation of these nectaries may be due to a carbohydrate accumulation during the ontogeny of foliar organs.
Metabolic activity of living sapwood ray cells in Picea mariana expressed by a new indicator
Authors: Yang K. C.
Published: April 2011

The metabolic activities of living sapwood ray cells of Picea mariana (Mill.) BSP. were studied and the nuclear slenderness ratio was compared with a new indicator, the nuclear elongation index. For comparative studies of the two indicators, 40 living sapwood ray cells from earlywood uniseriate rays of 11 sapwood growth rings were measured for cell length, nuclear length, and nuclear width. For the study of the relationship between the ray cell length and nuclear length, 40 earlywood and 34 latewood cells of the first, second, and fifth growth rings of sapwood of specimens collected in May were measured. A strong positive relationship between the nuclear length and the ray cell length existed in the three studied growth rings. A general decreasing trend of cell activity in the living sapwood ray cell was shown by both indicators. However, the new indicator, the nuclear elongation index, shows a smoother curve than that exhibited by the old indicator.
Rapid genotypic change in a population of the grass Danthonia spicata following disturbance
Authors: Scheiner Samuel M. , Teeri James A.
Published: April 2011

A population of the grass Danthonia spicata growing in a pine–hardwood forest in northern lower Michigan was studied before, during, and after a period of major disturbance. Samples of the aboveground population were collected after clear-cutting but before fire, 9 days after fire, 10 months after fire, and 13 months after fire. Change was examined by growing clonally replicated genets in a series of light and watering treatments in the greenhouse. There was a significant change in the composition of the population after fire. Genets collected following the fire grew faster and larger in the 100% light treatment than individuals collected before the fire. Differences among collections were small or not significant for plants grown in the 20 and 6% light treatments. The watering treatments showed little or no effects. Although there are limitations in the interpretation of common garden studies, the differences among collections appear to have a genetic basis. The growth characteristics of genets collected after the fire showed possible adaptation to postfire conditions. These results suggest a greater importance for genetic adaptation in the persistence of D. spicata during secondary succession than had been concluded from earlier experiments.
Ultrastructure des mitochondries des stomates de maïs; cas d'une ouverture photoactive
Authors: Lascève Gérard , Vavasseur Alain , Couchat Philippe , Pellegrini Liliane , Pellegrini Max
Published: April 2011

Young intact maize plants were placed in an experimental chamber specially designed to allow continuous measurement of transpiration and photosynthetic rates in defined environmental conditions. After two circadian periods, leaf samples were collected at the end of the night period and after 150 min of light exposure. Samples were immediately immersed in fixative bath and prepared for ultrastructural examination. In darkness, when stomata were closed, most of the observed guard cell mitochondria exhibited the characteristic morphology of the resting state, while the others appeared in the respiring state. In subsidiary cells, the distribution showed an inverse pattern. After photoactive stomatal opening, all mitochondria of the guard cells were in the resting state 3 configuration, but in subsidiary cells they were in active state 4 configuration. These differences in mitochondrial ultrastructure corresponding to their location in guard cells or subsidiary cells during photoactive stomatal opening provide information about energy expenditure in the cells of the stomatal complex. Subsidiary cells appear to play a role more important than merely an ionic reservoir.
Effect of temperature on ion efflux properties of leaf cell compartments in several chilling-sensitive and chilling-insensitive crop plants
Authors: Mozafar A. , Oertli J. J.
Published: April 2011

Ion efflux properties of leaf cell compartments were compared in several chilling-sensitive and chilling-insensitive plants : corn (Zea mays L. cv. Orla-312), cotton (Gossypium hirsutum L. cv. Stoneville-213), rice (Oryza sativa L. cv. M-9), spinach (Spinacia oleracea L. cv. Monnopa), and winter wheat (Triticum aestivum L. cv. Zenith). The effect of photoperiod and temperature (in spinach) and cold acclimation (in wheat) during growth on the subsequent response of cell compartments to temperature was also studied. Leaf strips loaded with Na+ (22Na) (all plants) and K+ (86Rb) (wheat only) were subjected to temperatures of 22, 15, 11, 7, and 3 °C to test efflux of tracers from various cellular compartments. When grown under identical conditions, compartmental absorption and efflux of tracers were different in corn, cotton, rice, spinach, and wheat. Changes in pretest growth conditions (in wheat and spinach) altered the uptake and efflux of tracers by leaf cells. The efflux data show that (i) the fast (free space?) compartment is temperature sensitive in several plants and (ii) not all compartments of every chilling-sensitive plant show increased leakiness at lower temperatures. Photoperiod (but not temperature) in spinach and cold acclimation in wheat were the factors that markedly altered efflux properties of cell compartments during growth. These observations are not fully consistent with models explaining chilling injury based on occurrence of cracks or pores in leaf cell membranes at lower temperatures. An alternative view based on built-in membrane channels is presented.
Adventitious rooting of apple microcuttings in vitro: an anatomical study
Authors: Hicks Gary S.
Published: April 2011

In view of the lack of information on the anatomy of rooting in vitro, the time course of adventitious rooting was followed in an apple rootstock. Microcuttings raised on Murashige–Skoog medium were transferred to medium containing indolebutyric acid, then fixed at 0, 1.5, 3, 5, 7, and 10 days. A variety of tissues in close proximity to the cut stem surface exhibited an "activation" response over the first 3 days. Root meristemoids consisting of densely staining cells with enlarged nucleoli formed outside the xylem by day 5. Considerable variation in meristemoid development was noted within single stems and among stems. Meristemoids transformed into root primordia, some of which established a vascular connection with the stem by day 10.
Additions to Nodulosphaeria
Authors: Shoemaker R. A. , Babcock C. E.
Published: April 2011

Redescriptions and illustrations are given for five species of Nodulosphaeria with five-septate ascospores. A key is provided for these and other known species with five-septate ascospores. Nodulosphaeria winteri (Niessl) Crivelli, known previously from Switzerland, is reported from California, U.S.A., on Plantago juncoides Lam.
Ontogeny of Eucalyptus pilularis – Pisolithus tinctorius ectomycorrhizae. II. Transmission electron microscopy
Authors: Massicotte H. B. , Peterson R. L. , Ackerley C. A. , Ashford A. E.
Published: April 2011

Eucalyptus pilularis – Pisolithus tinctorius ectomycorrhizae were synthesized in growth pouches, and ultrastructural features of the two symbionts were documented during ontogeny. In the root cap – meristem zone, fungal hyphae envelop the root cap and penetrate between root cap cells. These fungal hyphae have numerous organelles and nuclei, some of which are in mitosis. The inner mantle hyphae in this zone and in the pre-Hartig net zone are heterogeneous in cytoplasmic content and are separated from the epidermis by an electron-dense layer. In the young Hartig net zone, hyphae penetrate between epidermal cells which contain electron-dense vacuolar deposits. In this zone and in the older Hartig net zone, hyphae do not penetrate beyond the epidermis and therefore a paraepidermal Hartig net is formed. The outer cortical layer develops as a hypodermis with suberized cell walls. The root–fungus interface consists of Hartig net hyphae which form a labyrinthine wall system and epidermal cells which are enlarged radially and contain electron-dense vacuolar deposits.
Mature forest seed banks of three habitat types in central Idaho
Authors: Kramer Neal B. , Johnson Frederic D.
Published: April 2011

Soils were sampled in two 5-cm layers under mature forests in Pseudotsuga menziesii/Physocarpus malvaceus, Abies grandis/Acer glabrum, and Abies grandis/Vaccinium globulare habitat types in central Idaho. Seed content of sampled soils was determined using a wet sieve seed extraction process followed by greenhouse germination tests. Viable seeds representing more than 80 different species were recorded, with viable seed densities averaging 1065 ± 727/m2 and ranging as high as 4116/m2. Most viable seeds (67%) were found in the top 0- to 5-cm soil layer. Ceanothus velutinus, Physocarpus malvaceus, and Carex spp. accounted for nearly 50% of all viable seeds encountered. Buried seed constancies are presented to compare buried seed occurrence by habitat type.
Growth and survival of ectomycorrhizal and ectendomycorrhizal seedlings of Pinus resinosa on iron tailings
Authors: LoBuglio K. F. , Wilcox H. E.
Published: April 2011

The survival and growth of ectomycorrhizal and ectendomycorrhizal red pine (Pinus resinosa Ait.) seedlings transplanted from a nursery onto iron tailings were examined. Seedlings were inoculated with the E-strain fungus BDG-58 (Complexipes sp. Walker emend. Yang & Korf), Phialophora finlandia Wang & Wilcox, Pisolithus tinctorius (Pers.) Coker & Couch, or Suillus subluteus (Peck) Snell ex Slipp & Snell. The first two isolates are ectendomycorrhizal fungi and the last two ectomycorrhizal fungi. Two-year field data on the tailings indicated a mycorrhizal treatment effect only in root-collar diameter at the end of the first growing season. The mycorrhizal treatments had a higher survival rate than the controls, with BDG-58 and Ph. finlandia seedlings having the greatest percent survival. Results from freehand root sections indicated that ectendomycorrhizae persisted in young roots of 4-year-old red pine seedlings that had been transplanted 2 years previously.
The response of the feather moss, Pleurozium schreberi, to 5 years of simulated acid precipitation in the Canadian boreal forest
Authors: Hutchinson Thomas C. , Scott Martha G.
Published: April 2011

Permanent plots dominated by the feather moss, Pleurozium schreberi (Brid.) Mitt., were established at a Canadian boreal forest site to study the effects of simulated acid precipitation on percent cover, growth, and photosynthesis of vegetation. For a 5-year period, beginning in 1981, plots of P. schreberi received twice-monthly sprayings of simulated rain, adjusted to pH 5.6, 4.0, 3.5, 3.0, or 2.5 with a 2:1 molar mixture of sulfuric and nitric acids. Unsprayed plots were also monitored. Almost complete elimination of the moss had occurred in the plots sprayed with pH 2.5 by the end of the 2nd year of treatment, and substantial decreases in cover were also recorded at pH 3.0 and 3.5 over the 5 years. Significant reductions of up to 75% in total and living frond height and dry weight were recorded at pH 3.5 and lower. Lateral branches produced in acid-treated plots also were stunted and few in number. This decline in growth and percent cover of P. schreberi may have resulted from the decreased net photosynthetic rates measured in the field and would be accelerated by increased rates of evapotranspiration in the altered moss microhabitat.
Seasonal growth of the exotic submersed macrophyte Nitellopsis obtusa in the Detroit River of the Great Lakes
Authors: Nichols S. J. , Schloesser Donald W. , Geis James W.
Published: April 2011

Seasonal growth and occurrence of an exotic submersed aquatic macrophyte, Nitellopsis obtusa, was monitored at the head of the Detroit River of the Great Lakes from June 1984 to April 1985. Nitellopsis obtusa first appeared in early July, increased in biomass from July to September, remained at relatively high biomass from September to late January, and decreased substantially as ice breakup began in mid-February. By March it had become senescent, lacking chlorophyll and disintegrating easily. Nitellopsis obtusa was therefore available as a source of food and shelter for benthic and juvenile fish populations in late fall and winter, when other macrophytes were absent.
Thirty-three years of plant succession on the Kautz Creek mudflow, Mount Rainier National Park, Washington
Authors: Frenzen Peter M. , Krasny Marianne E. , Rigney Lisa P.
Published: April 2011

Mudflow deposits, when dated, offer an excellent opportunity to examine vegetation and soil development overtime. Vegetation on a 33-year-old mudflow deposit at Mount Rainier National Park, WA, is compared with data collected 4 and 7 years after deposition. Four plant communities are recognized on the mudflow deposit and one is recognized in the adjacent, undisturbed forest. Soil characteristics in each community are compared with soil data collected 8 and 15 years after deposition. Key factors influencing plant succession and soil development on the mudflow deposit are (i) presence of residual standing dead trees and associated organic debris and (ii) proximity of sample stands to adjacent, undisturbed forest. Successional trends and changes in soil characteristics over a 33-year period are discussed.
Springtime recovery of photosynthetic activity of white pine in Michigan
Authors: Jurik Thomas W. , Briggs George M. , Gates David M.
Published: April 2011

The CO2 exchange of a field-grown eastern white pine (Pinus strobus L.) in Michigan was monitored during the winter–spring periods of 1983 and 1985. Its light-saturated photosynthetic rate in ambient CO2 and temperature was depressed during the winter, but recovered very rapidly during the last week of April in both years. The depressed rates in the winter were not due solely to low air temperatures, since the rates remained low even on warmer days or when the air temperature was artificially increased. Photosynthetic activity was more highly correlated with soil temperature at 30 cm than with air temperature or soil temperature at shallower depths. However, photoperiod or endogenous factors could not be eliminated as potential controls on photosynthetic activity.
Characterization of stomatal development in Dianthus chinensis
Authors: Pappas Thalia , McManus Patricia , Vanderveer Peter , Croxdale Judith
Published: April 2011

Stomatal differentiation in Dianthus chinensis leaves was characterized structurally and functionally using plants of the seventh plastochron. Development of stomata was followed using scanning electron microscopy. The maturity of the stomatal complex, the existence of an open stomatal pore, and the localization of K+ within guard cells were used as indicators of stomatal function. The results showed that stomatal development spanned a 10- to 12-day period, which began on the fourth youngest pair of leaves and was completed in the middle of the blade of the sixth youngest leaf pair where stomatal function was acquired. Stomatal frequency on an area basis decreased from the base to the tip of the leaf blade and from the abaxial to the adaxial surface of the leaf. There was a 10-fold decline in the frequency of stomata during leaf maturation; frequency on the abaxial leaf surface was about twice that on the adaxial surface. Dimensions of the antechamber aperture changed during development but at maturity exhibited a range of lengths and widths that was independent of stomatal location on the leaf. The localization of K+ in guard cells occurred only in the later stages of differentiation and was absent in stomata of senescing leaves.
Regrowth of forest understory species following seasonal burning
Authors: Flinn Marguerite A. , Wein Ross W.
Published: April 2011

Small experimental plots in mixed-wood stands of the Acadian Forest were burned in the spring, summer, and autumn to obtain an estimate of the regrowth potential of common forest understory species. The number of stems was measured before burning and then monthly for 5 months thereafter. Supportive experiments on seasonal transplanting were conducted at the same time to determine regrowth potential after interspecific competition had been removed. Regrowth potential of species varied among seasonal burning treatments as expected and was strongest for Maianthemum canadense, Vaccinium myrtilloides, Andromeda glaucophylla, Vaccinium angustifolium, Viburnum cassinoides, and Betula populifolia. These species, which showed a 10-fold increase in stem number, could compete successfully with tree seedling number and composition and thus ultimately alter forest stand composition.
Response of Pyronema domesticum to volatiles from microbes, seeds, and natural substrata
Authors: Moore-Landecker Elizabeth
Published: April 2011

Volatiles emanating from fungi, bacteria, germinating or killed seeds, and nonsterile or sterile natural substrates (decaying wood, partially decayed oak duff, and garden soil) were tested for their effects on Pyronema domesticum, a pyrophilous discomycete. Mycelial growth was strongly stimulated by volatiles from Schizophyllum commune and inhibited by volatiles from Streptomyces griseus but otherwise was generally unaffected. Volatiles from Chaetomium globosum, a second Pyronema domesticum culture, Trichophea abundans, or Trichoderma viride had little or no effect on numbers of apothecia produced. Fewer apothecia formed with volatiles from Bacillus subtilis, Cyathus stercoreus, Dipodascopsis uninucleatus, Poronia aedipus, Proteus vulgaris, Micrococcus luteus, and Streptomyces griseus. Volatiles from all bacteria and Dipodascopsis uninucleatus impaired development of the ascogenous system. Elongated asci without ascospores formed in the presence of Proteus vulgaris. Apothecia did not form in the presence of volatiles from Sordaria fimicola, Schizophyllum commune, Rhizopus nigricans, germinating seeds, nonsterile wood, or charred duff. Volatiles from autoclaved seeds, nonsterile or autoclaved soil or duff, wood ashes, and sterile wood are strongly inhibitory for apothecial development and permitted only a few apothecia to form.
Inhibitory effect of cotyledons on plumule development in two alpine rosettes
Authors: Purohit A. N. , Nautiyal M. C.
Published: April 2011

The plumule in rosette plants showing the phenomenon of "pseudomonocotyly" remains in a quiescent stage at the base of the cotyledonary tube, and this quiescent stage appears to be due to the inhibitory influence of the cotyledons. This correlative inhibition in which the development of the embryonic apical region is influenced by the cotyledon may be an important survival adaptation in alpine rosettes.
The increase in survival of winter cereal seedlings due to light exposure during ice encasement
Authors: Andrews C. J.
Published: April 2011

Exposure of cold-hardened seedlings of a range of winter cereals (11 winter wheats, 1 winter barley, and 1 winter rye) to a light intensity of 100 μE∙m−2∙s−1 during ice encasement at −1 °C markedly increased survival in comparison with that in dark ice encasement. Cold hardiness of 'Dover' winter barley and 'Fredrick' and 'Norstar' winter wheats was significantly greater after a short period of light ice encasement than dark ice encasement. Less ethanol and more CO2 accumulated in plant crowns in light than dark ice, and lactic acid accumulated in the early days of ice encasement but was little influenced by light. There was greater utilization of total nonstructural carbohydrate in the crown in dark, than in light, and greater utilization of total nonstructural carbohydrate in ice than in air at −1 °C. Considerably less oxygen was consumed by plants in light than in dark ice, while leaves in aqueous solutions at −1 °C evolved significant levels of O2 in light but consumed O2 in the dark. It is proposed that the changes in metabolic components in light are associated with low-temperature photosynthesis, which provides cellular oxygen and greater levels of energy in support of cell maintenance in plants during ice encasement.
Response of rough fescue (Festuca scabrella) to light, water, temperature, and litter removal, under controlled conditions
Authors: Willms W. D.
Published: April 2011

Defoliation of dormant native plants often results in reduced plant height and productivity when growth resumes. To identify a possible mechanism for this effect, three experiments were conducted to test the hypothesis that the response is determined by a modified environment at the crown. Rough fescue (Festuca scabrella Torr.) sod was removed from native grassland during dormancy and transplanted into pots. In the first experiment, clipped plants were subjected to radiation densities (PAR) varying from 80 to 360 μE∙m−2∙s−1. In the second experiment, plants were grown in five soil water contents: 100, 100–80, 100–60, 100–50, and 100–40% of field capacity. In the third experiment, plant response to two levels of each factor (PAR, water, and temperature, 20:10 or 15:5 °C (light:dark)) were examined in relation to litter removal by clipping or burning. Plant response was measured as plant height, number of tillers, and tiller weight. Plant growth was most responsive to soil water deficits and least responsive to temperature. Plant height and tiller weight were 32% less than the control (field capacity) when soil water content was allowed to decline to 60% of field capacity. Plant height was decreased, but not tiller density, with increased PAR. Removing standing litter by clipping resulted in increased tillering (14%) and reduced plant height (15%). Since soil water was not limiting, the effect of clipping was attributed to increased PAR near the crown following litter removal.
Nitrogen cycling in a forested Minnesota bog
Authors: Urban N. R. , Eisenreich S. J.
Published: April 2011

The nitrogen cycle of a small, forested, Sphagnum peatland in northern Minnesota was studied for 4 years. Hydrologic inputs and outputs (atmospheric deposition, upland runoff, streamflow) were monitored for4 years, and annual uptake of N by vegetation was measured over a 3-year period. Microbe-mediated processes of nitrogen fixation and mineralization were measured in the laboratory and field, and accumulation rates of N within the peatland were measured in dated peat cores. Aerobic heterotrophs appear to be the dominant agents of N fixation at this site. Rates of N fixation decrease rapidly below the surface. Perhaps limited by moisture and low pH, N fixation (0.5–0.7 kg∙ha−1∙year−1) is a minor input to the bog relative to the input from atmospheric deposition (10.4 kg∙hg−1∙year−1). The bog is a large sink for N with approximately 65% of inputs retained. Annual turnover of N (66 kg∙ha−1) is much larger than the total input (14.6 kg∙ha−1). This large turnover is achieved by rapidly cycling a relatively small pool of N in the aerobic layers of peat. Plant uptake is closely coupled to mineralization such that losses from the system in runoff are small. However, 7 to 12 kg N∙ha−1∙year−1 is buried in anaerobic peat and rendered unavailable to the biota..
Developmental variation of leaf surface wax of maize, Zea mays
Authors: Blaker T. W. , Greyson R. I.
Published: April 2011

The variability of both composition and amount of leaf surface wax from maize leaves (Zea mays L. cv. Oh 43) of different ages, and on different leaves along the plant, was studied by gas chromatography. In addition to visual comparisons of chromatograms, statistical analyses (ANOVA and PCA) were performed. For this cultivar, among the 25 hydrocarbons recognized, the dominant gas chromatography peak of the waxes from young leaves is 1-dotriacontanol, while wax from mature leaves consists predominantly of odd-numbered alkanes. The surface wax of leaves from intermediate-aged plants is a mixture of the seedling and mature waxes. In addition to age-related differences, consistent leaf-related developmental differences were detected. Furthermore, the amount of wax extracted per unit area increased during the first 20 days, declined rapidly until day 50, and declined gradually thereafter.
Isozyme detection and variation in Uromyces appendiculatus
Authors: Lu T. H. , Groth J. V.
Published: April 2011

A polyacrylamide electrophoretic survey of 12 diverse isolates of the bean rust fungus, Uromyces appendiculatus, revealed that of 20 enzymes examined, 14 were readily detected in germinated urediniospores. Bands were assigned to 27 putative allozyme loci, of which 18 (in 12 enzymes) showed variation involving at least one isolate. Five of the isolates were identical isozymically, while four others differed from them by 9% or less; all of these nine isolates produced telia readily. Three other isolates that never (rarely for one of the three) produced telia were very different from the nine and from one another isozymically, suggesting that the species is not homogeneous.
Comparison of two culture methods for the production of haploids by anther culture in Solanum chacoense
Authors: Cappadocia Mario , Ahmim Mamar
Published: April 2011

The response of anther culture to two culture procedures was tested using anthers of a clone of self-incompatible Solanum chacoense Bitt. grown under field conditions and in a greenhouse. The use of a high level of sucrose (20%) in the induction medium increased the proportion of anthers producing macroscopic calli. This effect was more pronounced for plants grown under field conditions than for those grown in a greenhouse. The later regeneration process, using plants from either source, was not affected by this procedure.
Effects of ozone and acid rain on white pine (Pinus strobus) seedlings grown in five soils. III. Nutrient relations
Authors: Reich Peter B. , Schoettle Anna W. , Stroo Hans F. , Amundson Robert G.
Published: April 2011

The effects of acid rain and ozone on nutrient relations of white pine (Pinus strobus L.) were assessed for potted seedlings grown in each of five forest soils. Ozone treatments consisted of frequent exposure to 0.02, 0.06, 0.10, or 0.14 ppm ozone, while acid rain treatments consisted of exposure to simulated rain of pH 5.6, 4.0, 3.5, or 3.0. Plants were treated with all combinations of acid rain and ozone levels, and treatments were administered for 4 months. Acid rain caused significant leaching of Ca, Mg, K, Mn, Zn, and Cd from leaf litter on the soil surface, and soil Mg and K content declined as well. Concentrations in needles of N, P, K, Ca, Mn, Cd, and Cr were significantly increased as a result of acid rain treatments. In roots, concentrations of N, Mn, Cd, and Cr were significantly elevated as a result of acid rain. Similar increasing but nonsignificant trends were observed for Mg, Zn, and Cu in needles and for P, K, Mg, Ca, and Cu in roots. However, despite the increases in all the major nutrients, the nutrient weight proportions of K:N, P:N, Ca:N, and Mg:N generally declined in pine tissue as a result of acid rain. Although the above relationships were relatively consistent for pine in all soils, significant differences between soils in response to acid rain were observed for some elements. Ozone had significant effects on K, Ca, and Mn concentrations, and interactions between acid rain and ozone were observed for these three elements. In general, the results of these experiments suggest that the effects of acid rain on tree nutrition may be roughly similar in different soils but that the effects on physiology and growth will be heavily influenced by specific soil properties.
Growth of blue grama (Bouteloua gracilis) in response to atmospheric CO2 enrichment
Authors: Riechers George H. , Strain Boyd R.
Published: April 2011

Blue grama (Bouteloua gracilis (HBK.) Griffiths), an important C4 species in the Great Plains grasslands of the north-central United States, was grown under three concentrations of CO2: 350, 675, and 1000 μL∙L−1. Growth of blue grama was significantly enhanced by enrichment to 675 but not to 1000 μL∙L−1. At the end of the experiment, 7 weeks after planting, plants grown at 675 μL∙L−1 had 35% more total biomass and nearly 90% greater leaf area than controls grown at 350 μL∙L−1. This growth enhancement is large for a C4 species, but is modest compared with the response typical of C3 species. It is concluded that blue grama may experience increasing competition from its C3, associates if atmospheric CO2 continues to increase in the future.