bluuebunny/crossref_metadata_2025 huggingface dataset:
Statistical Geometry and Cavity Correlations in the Hard Sphere Fluid
Authors: Speedy Robin J. , Bowles Richard K.
Published: April 2008

The statistical geometry of a system of hard spheres is discussed in terms of the volumes Vj that lie with a sphere diameter, σ, of exactly j sphere centres. A site that has no sphere centre within σ is called a cavity site. We focus on the probability n00(r) that two sites separated by r are both cavity sites. n00(0), n00(σ), and the limiting slope (d ln n00(r)/dr)r=0, are all known in terms of the thermodynamic properties. The Vj and n00(r) are measured by computer simulation and an empirical expression, which satisfies the known exact relations, is shown to represent n00(r) precisely in the range 0 ≤ r ≤ σ.
PHOTOPERIODIC RESPONSES IN SEEDLINGS OF NORTHERN TREE SPECIES
Authors: Vaartaja O.
Published: April 2008

Seedlings of 10 tree species were tested under two widely different photo periodic conditions in environment otherwise near optimum. The amount of light given to the plants was the same under both conditions. Under the conditions simulating long photoperiods, the seedlings of all the species grew well and continued their growth during the 8-month experimental period. Under the short photoperiod, the following species remained nearly or fully dormant for several months beginning soon after germination: Larix laricina (Du Roi) K. Koch, Ulmus americana L., and two provenances of Picea glauca (Moench) Voss; the following species either remained nearly dormant or grew significantly slower than under the long day conditions: Betula lutea Michx. f., B. verrucosa Ehr., and Pinus banksiana Lamb.; P. resinosa Ait. was considered sensitive to photoperiods but its responses in appearance and growth were small; Caragana arborescens Lam., Thuja plicata Donn, and Acer negundo L. showed no significant response.
THE DEVELOPMENT OF THE BLUEBERRY SEED
Authors: Bell Hugh P.
Published: April 2008

Seed development was followed from fertilization to maturity. Pollen tubes required about 4 days to grow from stigma to ovule. In some plants, particularly bagged ones, nucellar cells remained alive and contents of the embryo sac degenerated. Many ovules did not develop. Seeds were counted and sorted in a random representative collection of 1075 berries. The average number of seeds per berry was 64.2. Of these 49.9 (or 77.7%) were imperfect. More complete pollination increased the percentage of normally developing ovules. Development of perfect seeds followed a familiar pattern. Unfamiliar features were noted as follows: 1. Degeneration of cells at both micropylar and chalazal ends resulted in a homogeneous plasma. This plasma formed strands across haustoria and almost completely surrounded the zygote. 2. Micropylar endosperm cells formed a dense plug. Developing embryos may have had difficulty in penetrating this plug. 3. Many embryos had died at some stage of development. 4. A conspicuous integumentary tapetum was present until the endosperm was about half its final size.Embryo development was the "soland" type. Mature seeds were "axile linear". Imperfect seeds were chiefly of two types: (a) medium sized and solid with middle integumentary layers lignified, or (b) small and collapsed with all tissues inside seed coat disintegrated. No imperfect seed had an embryo.
ADDITIONS TO THE PARASITIC FUNGI OF NOVA SCOTIA
Authors: Savile D. B. O.
Published: April 2008

The following parasitic fungi are newly reported from Nova Scotia: Peronospora cakiles Savile sp. nov. (on Cakile edentula), Taphrina tosquinetii (West.) Magn., Stigmatea robertiani Fr., Pucciniastrum potentillae Kom., Puccinia calcitrapae DC, Puccinia praegracilis Arth. var. cabotiana Savile var. nov. (on Hierochloë odorata, aecia on Habenaria psycodes), Uromyces ervi West., Cercospora pontederiae Ell. & Dearn., Isariopsis bulbigera (Fckl.) Savile comb. nov. (= Ovularia bulbigera (Fckl.) Sacc), Ramularia oxalidis Farl., Ramularia pusilla Unger (= Ovularia pusilla (Unger) Sacc.), Ramularia rubella (Bon.) Nannf., Ramularia subsanguinea (Ell. & Ev.) Savile comb. nov., Marssonina sennenis Gonz. Frag., Septogloeum potentillae Allescher, and Septoria levistici West. The status of the genera Ovularia and Ramularia is briefly discussed. A few new host records of other fungi are included.
THE EFFECT OF FUSARIUM TOXINS ON THE ENZYMIC ACTIVITY OF TOMATO HYPOCOTYL MITOCHONDRIA
Authors: Paquin Roger , Waygood E. R.
Published: April 2008

The presence of an active cyclophorase system capable of oxidizing the principal acids of the Krebs acid cycle was demonstrated in mitochondria from hypocotyls and cotyledons of tomato seedlings. The optimum conditions for active mitochondrial preparations and maximum enzyme activity, especially for the succinoxidase system, were determined and are reported.Lycomarasmin and fusaric acid, two toxins produced by Fusarium oxysporum f. lycopersici, inhibit the succinoxidase and cytochrome oxidase activity of the mitochondria at a concentration of 10−2 M. The inhibition was overcome by the addition of catalytic amounts of cytochrome c. No effect was observed on succinic dehydrogenase. It was concluded that the toxins inhibit enzyme activity by affecting the integrity of the mitochondria allowing diffusion of cytochrome c from active sites. The role of the toxins in Fusarium wilt of tomatoes is discussed.
STUDIES IN TREE PHYSIOLOGY: IV. FURTHER INVESTIGATIONS OF SEASONAL CHANGES IN MOISTURE CONTENT OF CERTAIN CANADIAN FOREST TREES
Authors: Clark J. , Gibbs R. Darnley
Published: April 2008

Complete seasonal patterns of moisture content of the wood and bark of Betula lutea (which resembles other species of birch) and of Tsuga canadensis are given, along with those for sapwood and heartwood of Abies balsamea and Picea rubens. Incomplete seasonal data are also presented on the moisture content of the wood of Picea glauca and Thuja occidentalis.Minor variations in the water content pattern of yellow birch due to precipitation, evapotranspiration, and winter insolation are described. These variations, examined in the light of climatic data, lend little support to the view that birch dieback is due to an increase in temperature or to drought, except possibly through their effects on some unknown biotic factor.The practical aspects of tree water content studies are discussed with particular reference to the questions of flotation and sinkage of logs.
Genera coelomycetum. XXI. Strasseria and two new anamorph-genera, Apostrasseria and Nothostrasseria
Authors: Raj T. R. Nag
Published: April 2008

Revisionary studies of the anamorph-genus Strasseria have led to the recognition of a single species: Strasseria geniculata, the synonymy of which is expanded to include S. carpophila f. pruni, S. oxycocci, S. nigra, and S. rhododendri. Strasseria aconiti is reduced to synonymy with Neoplaconema napelli. Strasseria agapanthi, S. camarae, S. corynocarpi, S. garciniae, S. japonica, S. petrakii, S. phomopsimorpha, S. polygonati, S. rusci, S. sequoiae, S. viburni, and S. vincae are shown to belong in Phyllosticta. Strasseria dar-akobensis is excluded from Strasseria. Strasseria lycopodina, Ceuthospora lunata, and three previously undescribed coelomycetous anamorphs are disposed in a new anamorph-genus: Apostrasseria. Nothostrasseria anam.-gen. nov., type species: N. dendritica (≡ Spilomyces dendritica) is erected for a fungus on leaves of Eucalyptus eximia, E. maculata, and E. obliqua in Australia.
Activités ATPasiques du nœud cotylédonaire et du bourgeon cotylédonaire du pois inhibé, réactivé ou soumis à la fusicoccine
Authors: Nougarède Arlette , Landré Pierre , Rembur Jacques
Published: April 2008

The activity of enzymes which hydrolyse ATP at neutral pH was demonstrated cytochemically in the cotyledonary node and in three types of cotyledonary buds (inhibited, released from dominance, treated with fusicoccin). In the intact plant, the transfer cells of the cotyledonary node showed a very strong Mg2+-dependent, ouabaïne-insensitive ATPase activity, essentially located on the outer surface of the plasmalemma. A high concentration of K+ stimulated the ATPase activity of the plasmalemma of transfer cells and sieve elements. ATPase activity was even more specifically detected along mitochondrial cristae and the tonoplast of the phloem transfer cells and along the reticular membranes of the xylem transfer cells. All these activities which were not modified by decapitation increased after a fusicoccin treatment. In the inhibited bud the same pattern of ATPase activity occurred along the plasma membrane but with a lesser intensity. At the base of the first-bud internodes the phloem transfer cells were the only ones with a high ATPase activity. Decapitation induced, without cell specificity, an increase in the ATPase activity of the plasmalemma for the entire bud, while after fusicoccin treatment, the increase extended to the tonoplast. Proper controls eliminate the possibility of artifactual reactions or interactions with other enzymes.
The influence of flooding pretreatment on metabolic changes in winter cereal seedlings during ice encasement
Authors: Andrews C. J. , Pomeroy M. K.
Published: April 2008

The survival of winter wheats during ice encasement is increased by pre-exposure to low temperature flooding. The response is duplicated by nitrogen exposure, indicating an anaerobic hardening process. During ice encasement, higher levels of ethanol accumulate in previously flooded plants than in nonflooded plants. Alcohol dehydrogenase activity is threefold higher at the end of a 2 week low temperature flooding period than in aerobically grown plants. The activity is lower after 3 days in ice. The decrease is similar in previously flooded and nonflooded plants, but is larger in Dover barley which is more susceptible to ice encasement stress than the wheats. Malate declines during flooding and is higher during ice encasement in nonflooded than in flooded plants. Previously flooded plants enter the more severe anaerobic stress of ice encasement with an accelerated glycolytic rate, and thus a higher survival potential.
Dehardening in flower buds of saskatoon-berry, Amelanchier alnifolia, in relation to temperature, moisture content, and spring bud development
Authors: Junttila Olavi , Stushnoff Cecil , Gusta Lawrence V.
Published: April 2008

Flower-bud dehardening of saskatoon-berry (Amelanchier alnifolia Nutt. ‘Smoky’ and ‘Pembina’) was studied under natural and controlled conditions. Flower buds were hardy to −45 °C until the middle of March, after which hardiness gradually declined to −12 °C by the beginning of May. Petal expansion was associated with a loss of hardiness, even though bud moisture content decreased slightly. Hardiness of unopened flower buds was closely correlated with bud moisture content (r = 0.94) and under outdoor conditions there was a significant positive correlation between cumulative degree days (base 0 °C) and bud moisture content. Imbibition in gibberellic acid (GA3) increased water uptake and reduced hardiness of excised flower buds compared with imbibition in water. Treatments with abscisic acid and salicylic acid had no significant effect on hardening. Budbreak, in the postrest period, required only 73 degree day (base 2 °C) heat units. Low-temperature exotherms were not detected in intact flower buds but were present in hardy excised florets.
Variation in germination percentage of basidiospores collected successively from wood decay fungi in culture
Authors: Schmidt E. L. , French D. W.
Published: April 2008

Successive collections of basidiospores, produced in culture from the same hymenial areas of four species of wood decay fungi, were tested for spore germination percentage on malt extract agar under controlled conditions. Spores from white rot fungi retained high germination levels after 5 weeks of spore production, but germination averages for brown rot fungi decreased by more than 50%. Such variation should be considered in wood pathology research using spore germination bioassay.
Historical and phenological observations on the spread of Chaenorrhinum minus across North America
Authors: Widrlechner Mark P.
Published: April 2008

Through a review of floristic and taxonomic literature and an examination of over 1500 herbarium specimens, this report documents the rapid spread of Chaenorrhinum minus (L.) Lange along railroads across North America. The relationship between C. minus and railroads is described and phenological data on flowering and fruiting are presented. The combination of an effective dispersal mechanism and the rapid onset of reproductive maturity contributes to the species' adaptive success.
Étude du polymorphisme intraclonal chez le Verticillium albo-atrum, forme à microsclérotes. III. Morphologie et morphogénèse comparées de deux isolats de phénotype sauvage et de leurs principaux variants
Authors: Boisson Claude , Lahlou Houria
Published: April 2008

From precise morphological studies of variants from two Moroccan isolates of Verticillium albo-atrum R. and B. (microsclerotial form), two main types of variants were determined. The first was characterized by the loss of sclerogenesis or by a late and weak sclerogenesis. The second was typified by some alterations in morphogenesis and morphology of microsclerotia. The range of morphological variability was delimited by its effects on certain characteristics of isolates such as general appearance and growth of thalli, conidiogenesis and appearance of conidiophores, sclerogenesis, and microsclerotial structure.
Catastrophic wind disturbance in an old-growth hemlock–hardwood forest, Wisconsin
Authors: Dunn Christopher P. , Guntenspergen Glenn R. , Dorney John R.
Published: April 2008

On 4 July 1977, the Flambeau River Hemlock–Hardwood Scientific Area (Sawyer County, WI) was leveled by a downburst of hurricane-force winds. This paper documents preblowdown and postblowdown composition in a 61-ha portion of a state Scientific Area. Total stand basal area after the blowdown was reduced to 6% of prestorm levels. Total seedling density increased greatly following the blowdown, especially that of Betula alleghaniensis Britt. Acer saccharum Marsh, continued to dominate the relatively unaffected sapling layer. A dense shrub layer of Sambucus pubens Michx. developed. Such massive blowdowns do not appear uncommon in northern Wisconsin. Implications for forest regeneration and structure are discussed.
A late snow bed bryophyte community in western Newfoundland, Canada
Authors: Belland René J.
Published: April 2008

The bryophyte floras of eight bryophyte-dominated late snow beds near Bonne Bay, western Newfoundland, were investigated and consisted of 49 species of which 4 are reported new for eastern North America (excluding Greenland): Andreaea nivalis Hook., Kiaeria falcata (Hedw.) Hag., Moerckia blyttii (Moerck) Brockm., and an undescribed species of Trematodon. Five additional species were previously unreported from Newfoundland. Eleven bryophytes from the Newfoundland snow beds are characteristic of this habitat throughout much of their world range, and 13 species show a disjunct distribution pattern between eastern and western North America.
Observations of flagellate protozoa (Phytomonas sp.) in the xylem of Euphorbia lasiocarpa in Ecuador
Authors: Dollet M. , Gargani D. , Cambrony D. , Dzido J. L.
Published: April 2008

In Asclepias curassavica L. and Euphorbia lasiocarpa Kl. flagellated protozoa (Phytomonas sp.) occur in laticiferous tubes. In Euphorbia lasiocarpa, but not in Asclepias curassavica, they also occur in the xylem and the intercellular spaces. The significance of these findings in relation to possible arthropod vector transmission of Phytomonas is discussed.
Root apex structure in Ephedra nevadensis
Authors: Peterson R. L.
Published: April 2008

The distinctive, large cells in the central region of the root apex of Ephedra nevadensis Wats. which do not incorporate [3H]thymidine and stain lightly with Feulgen reagent comprise the quiescent centre. These cells and adjacent meristem cells remain at the 2C–4C level of DNA. Ultrastructurally, cells of the quiescent centre are characterized by possessing proplastids, numerous ribosomes, small vacuoles, and few plasmodesmata. The root cap consists of a columella and periphery. Nuclei of columella cells are either at the 2C or 4C level of DNA as determined by microspectrophotometry. The mitotic index remains high up to 50 cell tiers from the quiescent centre – root cap boundary. Starch deposition is delayed considerably in columella cells but not in peripheral cells. The root cap of this genus is unique in its method of growth.
Telium formation and teliospore germination in Melampsora lini
Authors: Gold Randall E. , Statler Glen D.
Published: April 2008

Teliospore formation occurred 10–15 days following inoculation with urediniospores of Melampsora lini on stems of Linum usitatissimum cv. Bison. Seedlings supported extensive uredinial development followed by little telial production, whereas older stems exhibited progressively less uredinial development and generally more abundant telial production. Teliospores of M. lini were conditioned to germinate by treating telia with either alternate periods of (i) freeze–thaw and wet–dry or (ii) wet–dry. The minimum time required for the induction of germination was ca. 25 and 15 days for the two methods, respectively. Under constant conditions of temperature, humidity, and continuous light, teliospores germinated rhythmically with a periodicity of ca. 24 h and daily maxima between 1200 and 1800 for a period of 5 weeks, after which the cultures had decomposed. Quantitative estimation of germination was based on the ability of telial cultures, held over susceptible plants for a defined period, to cast infectious basidiospores that initiated the pycnial stage. After 6–10 freeze–thaw and (or) wet–dry cycles, the stem epidermis was severely disrupted and sloughed off from the fissured telial surface. Concurrently, the level of teliospore germination increased rapidly to its maximum. Metabasidia and basidiospores were observed only on telial surfaces stripped of epidermis. Following 21 cycles, no further germination was detected from the cultures then void of all telial remnants.
Photosynthetic recovery in arctic caribou forage lichens following a long-term field sulfur dioxide fumigation
Authors: Moser Thomas J. , Nash III Thomas H. , Olafsen Astrid G.
Published: April 2008

The gross photosynthetic response of Cladonia stellaris (Opiz.) Pouz. & Vezda., Cladonia rangiferina (L.) Wigg., and Cetraria cucullata (Bell.) Ach. was monitored during three growing seasons subsequent to a long-term, in situ SO2 fumigation conducted in 1978 at Anaktuvuk Pass, AK. The lichen vegetation which had experienced the greatest SO2 stress during the 1978 fumigation remained photosynthetically inactive. Significant photosynthetic recovery was discovered in the test species which had experienced sublethal concentrations of SO2; however, their photosynthetic capacities remained less than controls.
Photosynthesis, transpiration, and leaf diffusive conductance of the cassava leaf in response to water stress
Authors: Palta Jairo A.
Published: April 2008

The effects of short periods of water shortage on the CO2 and water vapour exchange of attached cassava (Manihot esculenta Crantz 'M Col 72') leaves were measured. Gas-exchange and leaf water potential measurements were made in outdoor grown plants previously subjected to varying periods without water. Leaf water potentials fell to between −0.61 and −1.06 MPa and net photosynthesis and transpiration rates declined as leaf water potential decreased. Estimations of the leaf internal CO2 conductance indicated that the linear relationship established between leaf water potential and net photosynthesis is dominated by, but not completely explained by, stomatal closure.
Ultrastructural localization of calcium in the organic acid secreting trichomes of chickpea (Cicer arietinum)
Authors: Lazzaro Mark D. , Thomson William W.
Published: April 2008

In the organic acid secreting trichomes of chickpea (Cicer arietinum L.), calcium is localized in the stalk and head cells using pyroantimonate and X-ray microanalysis. Light calcium deposits are present in the endoplasmic reticulum, mitochondria, and cytoplasm of the stalk and head cells and in the cell walls of the stalk cells. Dense calcium deposits are present in the vacuoles of stalk and head cells and within the plasmodesmata between stalk cells. In the head cells, heavy calcium deposits are present in small, secretory vesicles that fuse with the plasma membrane. In addition, calcium deposits are localized in the cell wall space around the head cells, in the secretion chamber, and in collected secretions. These observations suggest that secretion from the head cells occurs predominantly through an exocytotic, vesicular pathway. We conclude that once secreted, calcium diffuses through the walls to the collecting chamber and subsequently through the cuticular pores into the secretion droplet. Key words: calcium secretion, Cicer arietinum, pyroantimonate, secretory vesicles, trichome.
Leaf canopy display, stomatal conductance, and photosynthesis in seedlings of three tropical pioneer tree species subjected to drought
Authors: Reekie E. G. , Wayne P.
Published: April 2008

Seedlings of Piper aurtitum, Cecropia obtusifolia, and Trichospermum mexicanum, pioneer species of lowland tropical rainforests, were subjected to controlled drought cycles, with stomatal conductance and net photosynthesis monitored to determine species response. The affect of soil moisture on canopy display and the response of stomatal conductance to fluctuations in humidity, light, and temperature were also measured. Stomatal conductance and photosynthesis in Piper and Cecropia showed no relationship with soil moisture until it declined to approximately 20%. At higher soil moistures, stomatal conductance in Piper and Cecropia was positively correlated with relative humidity. In contrast, Trichospermum stomatal conductance and photosynthesis showed no relationship with relative humidity and declined gradually as soil moisture decreased. Canopy display in all three species showed a sharp decline at the end of the drought cycle. There were marked differences among species in canopy structure. Piper and Cecropia both have large leaves and a low fibre content in stems, petioles, and leaves, whereas Trichospermum has much smaller leaves and a higher fibre content. In addition, Piper has a higher leaf to stem ratio than Trichospermum. Differences among species in response of stomatal conductance and photosynthesis to environmental factors may reflect the need to maintain a relatively high turgor pressure in Piper and Cecropia for canopy display. Key words: canopy architecture, drought stress, leaf size, Piper auritum, Cecropia obtusifolia, Trichospermum mexicanum.
Development of stigmatoid anthers in a tobacco mutant: implications for regulation of stigma differentiation
Authors: Trull Melanie C. , Holaway Brian L. , Malmberg Russell L.
Published: April 2008

We characterized the development of a tobacco floral mutant, Mgr27, previously obtained by selecting for resistance to an inhibitor of an enzyme in the polyamine biosynthetic pathway. Mgr27 plants are shorter than the wild type with smaller leaves and a compact inflorescence. The plants have a regular leaf plastochron and a vegetative shoot apex similar to the wild-type vegetative shoot apex. There are frequently more than five floral organs in the first three whorls, and the anthers produce stigmatoids. At the scanning electron microscope level, the stigmatoids appear concurrently on all of the anthers and at approximately the same time that the stigma appears on the pistil. The stigmatoids contain tissue histologically and biochemically similar to transmitting tissue and they permit the germination and growth of pollen tubes. The mutant line has significantly lower levels of free and conjugated spermidine as well as significantly lower levels of conjugated putrescine. Key words: floral development, mutant, Nicotiana tabacum (tobaccco), polyamines, stigmatoid anthers.
Vegetation of stressed calcareous screes and slopes in Sverdrup Pass, Ellesmere Island, Canada
Authors: Maycock Paul F. , Fahselt Dianne
Published: April 2008

Although calcareous erosional mountain systems such as those in central Ellesmere Island constitute extremely limiting environments and are sometimes even considered to be totally unvegetated, quantitative analysis of vegetation revealed 156 species, 81 of which were lichens. Although cryptogams of such depauperate landscapes in the Canadian High Arctic have often been overlooked in vegetational studies, it was found that lichens serve as reliable ecological markers, and under the most limiting conditions, 11 species occurred as major dominants. The system also supported 37 bryophytes that in poor sites were dwarfed and sterile but that served as dominants under somewhat better conditions. Thirty-eight species of vascular plants were found, 7 of which were major dominants in less limiting environments. A wide range of both environmental factors and plant communities were found under the marginal conditions of the cliff, slope, and scree system. Key words: vegetation, lichens. High Arctic, polar desert, semipolar desert.
Comparative anatomy of absorbing roots and anchoring roots in three species of Cyclanthaceae (Monocotyledoneae)
Authors: Wilder George J. , Johansen Jeffrey R.
Published: April 2008

Absorbing roots and anchoring roots of Asplundia sp., Evodianthus fiinifer, and Thoracocarpus bissectus differ from one another anatomically in at least 15 quantitative characteristics and in additional related respects. Differences are diverse, involving both stelar and extrastelar tissues. Absorbing roots are significantly greater in diameter, have more vascular tissue, exhibit broader tracheary elements and sieve elements, and have other characteristics supporting the hypothesis that those features logically interpretable as optimizing conduction in xylem and phloem predominate in the absorbing roots. The three species also differ significantly from each other according to the anatomy of their absorbing roots, with T. bissectus having the most distinctive anatomy. Statistical and nonstatistical approaches to analysis of the data provided very consistent results, both in regard to differences between the two root types under study and to differences between taxa. Key words: absorbing roots, anchoring roots, Asplundia, Cyclanthaceae, Evodianthus, root anatomy, Thoracocarpus.
Seasonal and year to year variation in performance of Gordonia acuminata seedlings in different light environments
Authors: Cornelissen J. H. C.
Published: April 2008

The effects of light environment on temporal growth and allocation patterns in the subtropical Chinese evergreen tree Gordonia acuminata, a gap-dependent species, were studied during its first 2 years of growth. Seedlings were grown in full sun (S100), 55% of full sun (S5S), 33% of full sun (S33), and 18% of full sun (S18). During the 1st year, plant size and leaf dynamics were monitored nondestructively. The best growth was at S33. Growth rates fluctuated more from season to season in treatments of higher relative light exposure, largely owing to sun-imposed inhibition of growth in summer. Leaf size was to a large extent ontogenetically determined. Additionally, a size reduction with increasing light exposure was shown for individual leaves that had expanded during a given ontogenetic phase. In the 2nd year relative growth was best at S55 (first 6 months) and in full sun (second 6 months), successively, which resulted in S55 plants outgrowing the initially bigger S33 plants. Self-shading and smaller relative investment in leaf area were associated with a reduction of sun-imposed inhibition and thus with enhanced growth in sun in the 2nd year. The large seasonal and year to year variation in growth response to relative light exposure may have important consequences for the success of young Gordonia plants in gaps of different sizes or formed in different seasons. Key words: broad-leaved evergreen seedlings, gaps, growth, morphology, ontogeny, seasons, subtropical China.
Effet des conditions de culture sur la mycorhization de l’Helianthemum guttatum par trois espèces de terfez des genres Terfezia et Tirmania d'Algérie
Authors: Fortas Zohra , Chevalier Gérard
Published: April 2008

Three species of edible desert truffles, Terfezia arenaria, Terfezia claveryi, and Tirmania pinoyi associated with Helianthemum guttatum in Algeria were examined in this study. The mycorrhizal synthesis between the three species of desert truffles and Helianthemum guttatum was carried out with two different methods: (i) under axenic conditions on perlite permeated by a nutritive solution, by inoculating the seedlings with mycelial fragments; (ii) under gnotoxenic conditions on natural substrates, by inoculating plants with spore suspensions. The method of synthesis did not have any influence on the type of mycorrhizae. The desert truffles formed two types of mycorrhizae according to the fertility of the substrate: ectomycorrhizae without sheath, in the phosphorus rich substrates, or ectendomycorrhizae, also without sheath, in the phosphorus deficient substrates. Primordial ascomata were obtained in the syntheses involving polysporous inocula. Key words: ectomycorrhizae, ectendomycorrhizae, Helianthemum guttatum, Terfezia, Tirmania.
Effects of simulated herbivory on growth and reproduction of two beach annuals, Cakile edentula and Corispermum hyssopifolium
Authors: Gedge Kevin E. , Maun M. A.
Published: April 2008

Cakile edentula var. lucustris (sea rocket) and Corispermum hyssopifolium (bugseed) are two annual flowering plants that grow on the sandy shores of the Great Lakes. This habitat is extremely unpredictable and plants are subject to grazing by a number of insect herbivores as well as browsing by white-tailed deer. The objectives of these studies were to estimate the extent of herbivore damage under natural conditions, to determine the most vulnerable stage of damage, and to examine the compensatory ability of each species to tolerate herbivory. Greenhouse experiments showed that both species were able to compensate for low to moderate levels of artificial defoliation. However, high levels near the time of anthesis reduced the growth and reproductive output of both species. Similar experiments in the field revealed that although the critical time of damage was still the same, the plants were less able to tolerate herbivory. Cakile edentula plants exposed to natural herbivory in an unsprayed cabbage field were quickly attacked by large numbers of specialist insect herbivores and completely defoliated in 11 days. The fact that such damage does not occur in its natural habitat suggests that Cakile edentula escapes heavy damage because insects are unable to locate these populations along the shoreline. Key words: white-tailed deer, defoliation intensity, defoliation stage, compensatory response, indeterminate growth.
Morphological and chromosomal variation in Dodecatheon pulchellum (Primulaceae)
Authors: Suttill Terri A. , Allen Geraldine A.
Published: April 2008

Dodecatheon pulchellum (Raf.) Merr. is a widespread and morphologically variable species of western North America. Analysis of morphological variation, combined with chromosome counts and evidence from a transplant study, showed this species to consist of two subspecies. Subspecies cusickii is pubescent, mainly diploid, and occurs in the drier parts of the species range. The more variable ssp. pulchellum is glabrous to sparsely pubescent, mainly polyploid, and is widely distributed. Within ssp. pulchellum, three varieties can be recognized: the tall, many-flowered var. alaskanum, of wet, low-elevation habitats; the diminutive var. watsonii, generally of alpine habitats; and the intermediate and widely distributed var. pulchellum. Common garden studies indicate that size differences among these varieties have a genetic basis and that ecological differences exist in D. pulchellum even among morphologically similar forms. Key words: Dodecatheon, Primulaceae, systematics, morphology, chromosome numbers, common garden studies.
Resin flow as a function of height along the bole of loblolly pine
Authors: Tisdale Robert A. , Nebeker T. Evan
Published: April 2008

Resin flow was measured at four heights along the bole of loblolly pine, Pinus taeda L., using two, four, and eight wounds per height in May, June, July, and August of 1990. Consistent differences in resin flow between heights were observed with the eight per height treatment. The greatest amount of flow was found to be from the midbole and below. The differences in flow for the two and four samples per height treatments followed the same pattern as the eight per height treatment; however, no statistical differences were detected. Total flow for the entire tree was found to increase from May to August. Key words: oleoresin secretory system, Pinus taeda, southern pine beetle, insect – host interaction, induced response.
Response of Acacia mangium to vesicular – arbuscular mycorrhizal inoculation, soil pH, and soil P concentration in an oxisol
Authors: Habte M. , Soedarjo M.
Published: April 2008

The vesicular–arbuscular mycorrhizal (VAM) fungus Glomus aggregatum and the legume species Acacia mangium were grown together in a manganese-rich oxisol at pH 4.3 to 6.0 and at soil P concentrations favorable for VAM-host growth (0.02 mg ∙ L−1) and sufficient for non-VAM host growth (0.8 mg ∙ L−1). At the lower P concentration, vesicular–arbuscular mycorrhizal fungal (VAMF) colonization of roots increased as soil pH increased from 4.3 to 5.0. However, colonization of roots was not significantly influenced by further increases in pH. Growth of A. mangium at 0.02 mg P/L in the presence of G. aggregatum was inferior to that observed at 0.8 mg P/L, suggesting that there was some degree of host–endophyte incompatibility. Increasing P concentration from 0.02 to 0.8 mg P/L increased target soil pH in the unlimed soil from 4.3 to 4.8 and reduced the concentration of available soil Mn from 13.2 to 2.1 mg ∙ L−1. Thus, the better plant growth observed at the higher P concentration at pH < 5 was mainly due to the alleviation of Mn toxicity due to the precipitation of the cation directly by excess phosphate and (or) phosphate-induced elevation of soil pH. The poor VAMF inoculation effect observed at the lower soil P level in the unlimed soil was thus largely due to the toxicity of high concentrations of Mn2+ and H+ ions. Keywords: hydrogen ion, calcium, manganese-rich, manganese toxicity, pinnule P, soil acidity, VAMF colonization, VAMF effectiveness.
Fluorescent dye particles are good pollen analogs for hummingbird-pollinated Silene virginica (Caryophyllaceae)
Authors: Fenster Charles B. , Dudash Michele R. , Hassler Cynthia L.
Published: April 2008

We tested the utility of fluorescent dye particles as pollen analogs for hummingbird-pollinated Silene virginica (Caryophyllaceae) by comparing the movement of pollen and fluorescent dye across sequentially visited emasculated flowers. We found no differences in either the intercept or the slope of the regressions of the two particle types on floral visitation sequence. In addition, the presence of fluorescent powder on the stigmas of a flower was a good indicator of pollen transferred to that flower. Both pollen and dye particles were transported almost identical distances in the flower sequence. These data indicate that fluorescent powder is a good pollen analog for S. virginica. We compare our findings with previous studies examining the utility of fluorescent dye as a pollen analog. Keywords: pollen analog, fluorescent dye, pollen carry-over.
Floral and pollination biology of three sympatricVaccinium(Ericaceae) species in the Upper Ardennes, Belgium
Authors: Jacquemart A. -L. , Thompson J. D.
Published: April 2008

Comparative studies of the reproductive biology and pollination ecology of closely related species allow us to test several ideas related to the evolution of selfing taxa from outcrossing ancestors. The existence of closely related species in the same habitat provides a particularly useful opportunity to examine this issue. A variety of floral traits likely to be associated with the reproductive system of three sympatric Vaccinium species (V. myrtillus, V. vitis-idaea, and V. uliginosum) were quantified in a heathland in the Upper Ardennes, Belgium. These traits included the length and width of the corolla, the number and size of the anthers, the number of pollen tetrads and ovules, and the length of the style. Pollen to ovule ratios suggest a mixed mating system in the three species. The greater pollen to ovule ratio and stigma–anther separation in V. vitis-idaea suggest that it functions more as an outcrosser than the two congeners. The effects of caging, emasculation, and artificial pollination on fruit and seed set differed among years and among the three species. Supplementary pollination increased fruit set and fruit characteristics (particularly seed number) relative to natural pollination in the three species. The three species showed a varied but poor capacity to self in the absence of pollinators. Seed set per fruit was lower in the spontaneously selfed flowers in comparison with hand-crossed pollinated flowers in V. myrtillus and V. vitis-idaea but not in V. uliginosum. This higher ability to self in V. uliginosum indicates a lower capacity to self in the absence of pollinators. However, all the three species were at least partially self-compatible. Together the floral traits and selfing ability suggest that the polyploid V. uliginosum appears to be more highly selfing than the two diploids, particularly V. vitis-idaea. Keywords: floral biology, mixed mating, mating system, Vaccinium, seed set.
Population genetic structure in duckweed (Lemna minor, Lemnaceae)
Authors: Cole Christopher T. , Voskuil Martin I.
Published: April 2008

Allozyme variation in 11 Minnesota populations of Lemna minor L. was studied, using 11 enzyme systems, resolving 16 putative loci from 285 plants. Significant deviations from Hardy–Weinberg frequencies occurred in several populations that had excesses of heterozygotes at several loci. While genotypic diversity and evenness measures are similar to other vegetatively reproducing plants (D = 0.541, E = 0.607), very few multilocus genotypes per population were found (mean = 4.0). Substantial population structure was evident (FST = 0.407), apparently reflecting low levels of gene flow (Nm = 0.30) despite the capacity of this species for dispersal of plantlets. This low level of gene flow and apparent low frequency of sexual reproduction has produced substantial levels of genetic divergence among populations, despite an absence of morphological differentiation. Keywords: allozymes, genetic structure, hydrophily, Lemna, vegetative dispersal, vegetative reproduction.
Ultrastructure of the ungerminated conidium of Blumeria graminis f.sp. hordei
Authors: Roberts Jr. Donald R. , Mims Charles W. , Fuller Melvin S.
Published: April 2008

Ungerminated conidia of Blumeria graminis f.sp. hordei were prepared for transmission electron microscopy using cryofixation and freeze-substitution. Conidia were uninucleate, with the nucleus located in the central portion of the conidium, typically off to one side. The nucleus was spherical and contained a distinct nucleolus with an associated satellite. Conidia contained numerous large, spherical vacuoles that occupied much of the spore volume. Vacuolar contents were mostly homogeneous with occasional electron-opaque inclusions. Much of the cytoplasm consisted of lightly staining aggregations of glycoprotein that could be labelled with Concanavalin A – gold and that stained darkly using a modified Thiéry's reaction specific for carbohydrates containing vicinal hydroxyl groups. Mitochondria, strands of endoplasmic reticulum, Golgi body equivalents, multivesicular bodies, microbodies, Woronin bodies, and microtubules were present in the conidium. Cuboidal, stacked, electron-translucent structures also were present in the cytoplasm. The conidium was surrounded by a two-layered wall that labelled with gold-conjugated wheat germ agglutinin-ovomucoid, indicating the presence of chitin. The wall between attached conidia contained areas that did not label with gold-conjugated wheat germ agglutinin-ovomucoid. Keywords: Erysiphe, ultrastructure, electron microscopy, freeze substitution.
Changes in nuclear genome size and relative ribosomal RNA gene content in cambial region cells ofAbies balsameashoots during the development of dormancy
Authors: Lloyd A. D. , Little C. H. A. , Mellerowicz E. J. , Riding R. T.
Published: April 2008

The relationship between nuclear genome size, measured cytophotometrically, and relative ribosomal RNA gene (rDNA) content, determined as the ratio of the hybridization signals from a 25S rRNA gene probe and a randomly labelled total genomic DNA probe, was investigated in cambial region cells of balsam fir (Abies balsamea (L.) Mill.) shoots during the onset of dormancy and the transition between the dormancy stages of rest and quiescence. The dormancy status was manipulated by exposing potted trees for 13 weeks, starting August 14 when the cambium was still active, to one of the following environments: (i) the declining temperature and photoperiod of the natural environment (denoted N-N), (ii) simulated natural temperature and 15-h photoperiod (sN-15), (iii) simulated natural temperature and 8-h photoperiod (sN-8), and (iv) warm temperature and 15-h photoperiod (sN-15). On November 12, the trees were transferred to a greenhouse having environmental conditions favorable for growth to assess their ability to reactivate. The entire activity –rest–quiescence transition occurred in the N-N environment and was associated with an increase in nuclear genome size and a decrease in the relative rDNA content. The sN-8 environment also induced the transition but not completely, and the associated increase and decrease in nuclear genome size and relative rDNA content, respectively, were smaller than in the N-N environment. The sN-15 environment delayed the onset of rest, inhibited the changeover to quiescence, increased then decreased the nuclear genome size, and did not affect the relative rDNA content. The W-15 environment, which induced budbreak and the formation of a false ring, also prevented the rest–quiescence transition and transiently increased the nuclear genome size without altering the relative rDNA content. The data suggest that the normal rest–quiescence progression in shoot cambial cells is associated with an increase in nuclear genome size, which is caued by amplification of a fraction that is not rDNA but is recognized by our genomic probe. Keywords: dormancy, genome size, ribosomal RNA genes, vascular cambium.
Clonal structure and fertility in a sympatric population of the peat mosses Sphagnum rubellum and Sphagnum capillifolium
Authors: Cronberg Nlls
Published: April 2008

Data from isozyme and leaf shape variation are combined to explore the clonal structure at a site where hybridization between Sphagnum rubellum and Sphagnum capillifolium was previously indicated. Shoots of both species were sampled at 10-cm intervals along seven transects across different hummocks. Allelic data from 13 enzyme systems revealed 22 multilocus genotypes representing different clones, 18 being S. capillifolium and 4 being S. rubellum. The mean ± SE and maximum clonal length were 35 ± 8 cm and 160 cm, respectively. The sets of alleles found in the progeny of S. capillifolium were identical to the maternal complement of alleles in 78% of the material, indicating either self-fertilization or fertilization by a male with the same set of alleles at the screened loci. Outcrossing was detected in six cases. Patterns of differentiation and the hierarchical structuring of diversity among species, transects, and clones were analysed with canonical variates analysis using stem-leaf characters. A stronger relative differentiation was found between transects than between species. Clones identified by electrophoresis were usually morphologically well defined. Hybridization was indicated by morphological characters, occasional misplaced alleles, and signs of developmental instability. Keywords: allozymes, computerized image analysis, breeding system, clonal structure, Sphagnum rubellum, Sphagnum capillifolium.
Mitosis in the yeast phase of Agaricostilbum pulcherrimum and its evolutionary significance
Authors: Frieders Elizabeth M. , McLaughlln David J.
Published: April 2008

Agaricostilbum pulcherrimum is an anomaly and is difficult to place systematically. It possesses a yeast phase, and as in most basidiomycetous yeasts, mitosis has not been investigated cytoiogically. Yeast cells of A. pulcherrimum were prepared for immunofluorescence and transmission electron microscopy by a freeze-substitution method. A cladistic analysis of cell cycle characters among A. pulcherrimum and two ascomycetous and two basidiomycetous yeasts, performed with phylogenetic analysis using parsimony, revealed that A. pulcherrimum is basal within these basidiomycetes. Spindle pole bodies are multilayered discs and appear to be intranuclear during early division, similar to meiotic division. Spindle initiation and early elongation occur in the parent, a situation unreported in basidiomycetous yeasts. The site of spindle initiation, the position of the nucleus during division, and the pattern of astral microtubules demonstrate that the mode of nuclear division in A. pulcherrimum is intermediate between those of the investigated ascomycetous and basidiomycetous yeasts. Keywords: basidiomycete, cell cycle, cytoskeleton, immunofluorescence, phylogeny, spindle pole body.
Lipids and their seasonal variation in the nucellar layers of Scots pine (Pinus sylvestris) seeds
Authors: Tillman-Sutela Eila , Johansson Anu , Laakso Pälvi , Kallio Heikki , Kauppi Anneli
Published: April 2008

The content, composition, and seasonal variation of lipids in the nucellar layers of two mature Scots pine seed lots from northern and central Finland were studied. These lipophilic layers, which are located inside the seed coat, are composed of collapsed cells and restrict the imbibition of seeds. In this study, epicuticular wax was found on their surface; in particular, the surface of the nucellar cap was composed of intermeshing wax rods. The content of total lipids of the nucellar layers varied seasonally from 10 to 24%, being highest in April. In addition to simple lipids, which formed the most abundant lipid fraction in nucellar layers, small amounts of phospho- and glyco-lipids were also present. The proportion of simple lipids and their fatty acid composition in the seeds of both provenances remained constant throughout the year, whereas seasonal variation was found in the proportions of phospho- and giyco-lipids and in their fatty acids. In general, the variation was more marked in the northern seed lot. The unsaturated fatty acids dominated in the fractions of simple lipids and phospholipids, with linoleic acid being the most abundant single fatty acid. The saturated fatty acids with more than 22 carbon atoms were most abundant in the glycolipid fractions. The role of lipids for the function of the collapsed nucellar layers in the regulation of imbibition and germination of pine seeds is discussed. Keywords: Pinus sylvestris L., northern seeds, fatty acids, imbibition, germination.