bluuebunny/crossref_metadata_2025 huggingface dataset:
Size structure and seed yield over 4 years in an experimental Cassia marilandica (Leguminosae) population
Authors: Piper Jon K.
Published: April 2011

An experimental population of a perennial species, Cassia marilandica, was monitored for 4 years to examine changes in size structure and seed production over time. Plants flowered and set seed the 1st year and annually thereafter. Plant size, seed mass per plant, and reproductive effort were highest in the 2nd year but declined thereafter. Over the first 3 years, density remained constant, but plant size and yield varied. By the 4th year, density, size, and seed yield all declined, owing probably to combinations of drought and insect herbivory. Mean distance to nearest neighbors was consistently positively correlated with plant size but with seed mass in the 2nd and 3rd years only. Plant size was positively correlated with seed mass in each year, with reproductive effort in the first 3 years, but with relative growth rate in the last 2 years only. Population size structure and lifetime reproductive output were generally positively skewed. Except for a slight effect from the 1st to the 2nd year, no cost of reproduction, measured as reduced growth, reproduction, or likelihood of survival was seen. Key words: Cassia marilandica, cost of reproduction, density, Leguminosae, nearest neighbor, perennial, population structure, prairie plants, seed mass.
Relationships between some North Atlantic and North Pacific species of Porphyra (Bangiales, Rhodophyta): evidence from isozymes, morphology, and chromosomes
Authors: Lindstrom Sandra C. , Cole Kathleen M.
Published: April 2011

Five pairs of putative sibling species of Porphyra are recognized between the boreal North Atlantic and North Pacific oceans on the basis of similarities in isozymes, morphology, and chromosomes. These pairs are North Atlantic P. amplissima and North Pacific P. miniata (recognized here as P. cuneiformis), North Atlantic P. "leucosticta" and North Pacific P. fucicola, North Atlantic P. "linearis" and North Pacific P. pseudolinearis, North Atlantic P. miniata and North Pacific P. variegata, and North Atlantic P. "purpurea" and North Pacific P. "purpurea." Species names in quotation marks are tentative, pending verification by further studies, since at least two species are currently recognized by each of these names. Evidence from isozymes and morphology is used to support separation of P. amplissima and P. cuneiformis from P. miniata, and reference is made to their type specimens. Key words: biogeography, chromosomes, isozymes, morphology, Porphyra, vicariance.
A rapid fluorescence technique to probe the permeability of the root apoplast
Authors: Enstone Daryl E. , Peterson Carol A.
Published: April 2011

The alkaloid berberine is useful as a mobile apoplastic tracer. It is readily precipitated by thiocyanate, forming bright yellow, needle-like, fluorescent crystals. When berberine hemisulphate and potassium thiocyanate are applied sequentially to plant tissue, the crystals form in unmodified walls and in the lumina of dead cells such as tracheary elements. Lignified and suberized walls stain with berberine but do not develop crystals. Regions of the plant that have been penetrated by the chemicals can be located by preparing freehand sections, mounting them in potassium thiocyanate to inhibit dissolution of the crystals, and examining them with a fluorescence microscope. When the two chemicals are sequentially introduced into the xylem of onion, corn, and broad bean roots, the tracer does not pass the endodermal Casparian band, indicating that the system traces apoplastic pathways. The chemical concentrations that produce sufficient crystals so that berberine can be used as an apoplastic tracer in primary roots are 0.05% berberine hemisulphate and 0.09 M potasium thiocyanate. These concentrations were not toxic to cells of onion bulb epidermis. They reduced the growth rates of corn and broad bean roots but did not kill them. Berberine–thiocyanate is a useful apoplastic tracer provided care is taken not to exceed the limits of berberine toxicity to the tissue. Key words: apoplastic tracer, berberine hemisulphate, potassium thiocyanate, roots, toxicity tests, corn, onion, broad bean.
Effect of drought and waterlogging stress on needle monoterpenes of Picea abies
Authors: Kainulainen P. , Oksanen J. , Palomäki V. , Holopainen J. K. , Holopainen T.
Published: April 2011

Monoterpenes were analysed in needles of clonal Picea abies (L.) Karst. exposed to drought and waterlogging. In drought-stressed trees the amounts of tricyclene, α-pinene, and camphene were significantly (p < 0.05) higher than in the control trees. In the drought treatment the total terpene concentration was also significantly (p < 0.05) higher. Waterlogging did not have significant effects on individual terpenes and total terpene concentration. However, multivariate redundancy analysis indicated that the effect of treatments on all the compounds simultaneously was not significant (p = 0.12). These results are discussed in terms of their potential impact on preferential selection of host plant by insects. Key words: drought, needles, Picea abies, terpenes, waterlogging.
Influence of culture conditions on mycelial growth and phialospore production and germination in Chalara elegans
Authors: Punja Zamir K.
Published: April 2011

Mycelial growth, both linear extension and biomass accumulation, and phialospore production in three Chalara elegans strains from diverse geographical areas were greatest at 20–25 °C. Growth and sporulation were minimal at 10 °C and nil at 35 °C. The optimal pH range for growth was 4.0–6.5, and no growth was observed at pH 3.0 or 7.75. Phialospore production was most abundant at pH 5.5–6.5. A reduction in the osmotic potential of the medium from −0.2 to −0.6 MPa using PEG 8000- or CaCl2-enhanced phialospore production by twofold to threefold and increased mycelial biomass by approximately 35%. With further reductions in osmotic potential, there were corresponding decreases in growth and sporulation, both of which were nil at −1.8 MPa. Cultures grown in continuous darkness had slightly greater growth and sporulation than cultures exposed to light. Phialospores germinated on 1 % Noble water agar in the absence of exogenous nutrients, with 80–96% germination at pH 4.0–6.0, temperatures of 15–25 °C, and an osmotic potential of −0.2 to −0.4 MPa. The germ tubes either developed into extensive hyphae or terminated in short phialides within which secondary phialospores were produced without an intervening mycelial phase (microcycle conidiation). Germination to produce microcycle conidiation was strain dependent, was greater in older (8 week) than in younger (3 week) cultures, and was not affected by the density of spores plated onto the agar surface. The addition of 50 mM glucose enhanced the hyphal form of germination in all strains, whereas heat stress (40 °C for 22 h) enhanced microcycle conidiation in one strain. An osmotic stress provided by 50 mM NaCl or CaCl2 had no effect on the two forms of germination. These findings are discussed in relation to the development of root diseases caused by C. elegans. Key words: black root rot, dematiaceous hyphomycete, endoconidia, microcycle conidiation, Thielaviopsis basicola.
Lack of isozyme similarity between Vigna unguiculata and other species of subgenus Vigna (Leguminosae)
Authors: Vaillancourt R. E. , Weeden N. F.
Published: April 2011

The cowpea (Vigna unguiculata (L.) Walp.) is an important crop of tropical Africa, Asia, and South America. However, the relationship between the cowpea and other species of subg. Vigna is relatively unknown. The objective of this study was to assess the genetic distance among species of subg. Vigna using isozymes. Twenty-four populations of the cowpea species and 39 populations from 10 other species (at least one species per section of subgenus Vigna) were sampled. Nei's genetic distance was calculated from allelic frequencies at 26 isozyme loci. UPGMA cluster analysis was performed. The range of genetic distance among species of subg. Vigna (0.41 – 2.69) was greater than previously reported in most plant genera. Three clusters of species were apparent. The first cluster included three species of sect. Vigna (V. luteola, V. oblongifolia, and V. subterranea (the Bambara groundnut)). The second cluster grouped together sections Liebrechtsia and Macrodontae. The third cluster included V. unguiculata, V. reticulata, and V. vexillata. The distances between species of this cluster were large and of similar size in all combinations (range from 0.92 to 0.95). None of the species included in this survey can be called a close relative of V. unguiculata. Key words: Vigna, cowpea, isozymes, genetic distances.
Cryoprotection of Plagiomnium affine induced by various natural and artificial substances
Authors: Rütten Dorothea , Santarius Kurt A.
Published: April 2011

Greenhouse-grown shoots of Plagiomnium affine (Funck) Kop. were incubated in solutions of various potential cryoprotectants prior to freeze–thaw treatment. Sucrose uptake and release and plasmolysis studies indicated that the permeability of the plasma membrane of leaf cells for sugars, proline, and polyethylene glycols with average molecular weights of 400 (PEG-400) and 1000 (PEG-1000) was very low or insignificant, but that dimethylsulfoxide readily penetrated into the cytosol. Pretreatment of shoots at concentrations of these compounds that induced plasmolysis effectively increased the cryoprotection of the moss tissue. Obviously, damage of the plasma membrane by freeze–thaw treatment was avoided when compatible solutes reached a sufficient concentration either in the cytosol, outside the protoplast, or in both compartments. Pretreatment of shoots with hypertonic glycerol and PEG-4000 solutions also caused plasmolysis but did not prevent freeze–thaw damage. Efficient cryoprotection of moss thalli by various additives indicates that cryoprotective compounds could also play a role in acquisition of frost tolerance of bryophytes. Key words: cryoprotection, freezing, frost tolerance, permeation, photosynthesis, Plagiomnium affine, sucrose.
La cinétique des unités vasculaires sépalaires du Fittonia verschaffeltii
Authors: Cusset Gérard
Published: April 2011

Observations of development and arrangement of sepal veins distinguished three groups of vascular units. Lignification kinetics of each of these groups corresponds to Langmuir's biophysical model. Key words: lignification, tracheogenesis, veins, sepals, perianth.
La trachéogenèse sépalaire globale du Fittonia verschaffeltii
Authors: Cusset Gérard
Published: April 2011

Measurements of total lignified length of the sepal veins showed that this value is proportional to the sepal area and can be described by a time-related Gompertz function. Vascular density corresponded to a hyperbolic function of sepal area. In relation with time, this density included three successive stages. A link with the sepal water economy appears highly probable, since the transitions between phases corresponded to the moment of vessel formation and the moment stomata became functional. Key words: lignification, tracheogenesis, sepals, hierarchical levels. [Journal translation]
Isoetes × truncata: a newly considered pentaploid hybrid from western North America
Authors: Britton Donald M. , Brunton Daniel F.
Published: April 2011

Three Isoetes found in Pyramid Lake, Jasper National Park, Alberta, constitute populations of tetraploid (2n = 44)I. maritima, hexaploid (2n = 66)I. occidentalis, and an abortive-spored, pentaploid hybrid (2n = 55) with intermediate morphological characteristics. Although the hybrid has been present in the lake since at least 1918, I. maritima and I. occidentalis were previously unknown in Alberta. The presence of these aquatics hundreds of kilometres from their next known populations in central British Columbia is suspected to reflect the floristic and faunal affinity of the Pyramid Lake area to biotic regions in the interior of British Columbia. Morphological, scanning electron microscopy, and cytological data are provided to support our conclusion that the Alaskan type material of I. × truncata is synonymous with the Pyramid Lake pentaploid. Investigations of similar taxa in western North America detected several I. occidentalis populations in Alaska where it was previously unknown. This represents the first report of a pentaploid Isoetes hybrid in North America and the first western North American hybrid to be described in detail. Key words: Isoetes, Isoetes maritima, Isoetes occidentalis, Isoetes × truncata, hybrid, Alberta, Alaska.
Schizolysis of dolipore–parenthesome septa in an arthroconidial fungus associated with Dendroctonus ponderosae and in similar anamorphic fungi
Authors: Tsuneda A. , Murakami S. , Sigler Lynne , Hiratsuka Y.
Published: April 2011

An arthroconidial anamorphic fungus occurred in pupal chambers of the mountain pine beetle (Dendroctonus ponderosae) in lodgepole pine. No teleomorph was found and no suitable form genus was available for its disposition. However, in cultural characteristics it closely resembled the group 1 arthroconidial fungi, defined by other researchers as probable basidiomycete anamorphs. Septa of the pupal-chamber fungus and several of the group 1 isolates were of the dolipore–parenthesome type. Conidial separation was by septum schizolysis. Cell separation was initiated by disintegration of the dolipore wall, followed by progressive shrinkage of the fused dolipore wall. The parenthesomes retracted towards the dolipore wall and the triangular areas of the cross wall dissolved. The cross wall then split centripetally along the median electron-light layer to complete cell separation. The pupal-chamber fungus was also compared with Phlebia radiata (group 2) and with groups 3 and 4 strains of other researchers. Mauginiella scaettae was confirmed to have simple septa; thus this genus fails to accommodate arthroconidial basidiomycete anamorphs. Key words: basidiomycete anamorphs, dolipore–parenthesome septa, septum schizolysis, arthroconidiogenesis, Phlebia radiata, Mauginiella scaettae.
An ultrastructural study of pollen development in tomato (Lycopersicon esculentum). II. Pollen maturation
Authors: Polowick P. L. , Sawhney V. K.
Published: April 2011

The maturation of tomato pollen grains encompassed several ultrastructural changes. The generative cell separated from the intine and was free in the cytoplasm of the vegetative cell. This process coincided with the appearance of starch in plastids and the division of elongated mitochondria. This stage was followed by a second phase of vacuolation in the vegetative cell cytoplasm. Starch was still abundant at this stage, as were mitochondria, endoplasmic reticulum (ER), and ribosomes. Lipid droplets were the prominent feature of mature pollen grains. Each droplet was surrounded by rough ER (RER), suggesting the role of RER in lipid accumulation and mobilization. Long stretches of ER were present at early stages of maturation, and stacks of up to 50 strands of RER were abundant in mature pollen. The plastids in mature pollen were devoid of starch and had few internal membranes. Mitochondria were abundant and spherical with parallel cristae. In many cases, the cytoplasm at the periphery of the mature pollen grain was dense, forming a distinct zone, and contained only ER. The generative cell cytoplasm had mitochondria, ER, and actin-like filaments but no plastids. The pollen wall at maturity had a lamellated foot layer, a lightly sculptured tectum, and broad intine. The intine was layered in the region of the pollen aperture. Key words: Lycopersicon esculentum, pollen grains, tomato, ultrastructure.
Population structure of Heterobasidion annosum from North America and Europe
Authors: Otrosina William J. , Chase Thomas E. , Cobb Jr. Fields W. , Korhonen Kari
Published: April 2011

Isolates of Heterobasidion annosum (Fr.) Bref. representing North American S and P and European S, P, and F intersterility groups were subjected to isozyme analysis. European S, P, and F groups had more variability than the North American S and P groups in expected hterozygosity, number of alleles per locus, and percent polymorphic loci. In contrast with the North American S and P groups, the European intersterility groups could not be distinguished from each other on the basis of individual isozyme loci, although significant differences in allele frequencies exist between European S and P groups. This suggests that evolution proceeded at different rates in the intersterility groups, or intersterility barriers appeared later in the European populations relative to the North American populations of H. annosum. Changes in climate and host species associations during the Tertiary may have been a major factor in evolution of H. annosum intersterility groups. Key words: allozymes, forest tree hosts, playnological events, evolutionary relationships, Hymenomycetes, root disease.
Inhibitory effects of UV mutants of Streptomyces corchorusii and Streptomyces spiroverticillatus on bean and banana wilt pathogens
Authors: El-Abyad Mohamed S. , El-Sayed Mostafa A. , El-Shanshoury Abdel-Reheem , El-Batanouny Nadia H.
Published: April 2011

The purpose of this investigation was to produce improved mutants of Streptomyces corchorusii and Streptomyces spiroverticillatus, using a UV-irradiation regime, which are effective against the causal pathogens of the Fusarium wilt of French bean and the bacterial wilt of banana, respectively. Seven out of the 11 mutants obtained from S. corchorusii were active antagonists against Fusarium oxysporum f.sp. phaseoli; mutant 155 was the most effective. All five mutants obtained from S. spiroverticillatus showed inhibitory effects against Pseudomonas solanacearum; mutant 281 was the most potent. Spore germination, germ-tube elongation, growth, and sporulation of F. oxysporum f.sp. phaseoli were significantly inhibited in the different concentrations of filtrates of either wild or mutant 155 of S. corchorusii in vitro with the mutant being more effective; maximum inhibition was at 80% concentration. The filtrate of either wild or mutant 281 of S. spiroverticillatus sharply decreased the number of colonies of P. solanacearum as its concentration increased up to 80%, at which no growth was obtained. The in vivo utilization of S. corchorusii in the biocontrol of Fusarium wilt of French bean revealed that soaking seeds in filtrate of the antagonistic strain prior to sowing was the most effective treatment and that mutant 155 reduced disease incidence by 83.4% (43.3% for the wild type) compared with the untreated control, in addition to improving plant growth. Key words: antagonism, UV irradiation, mutation, Streptomyces spp., Fusarium wilt, bacterial wilt, French bean, banana.
A typologic and morphometric study of variation in phytoliths from einkorn wheat (Triticum monococcum)
Authors: Ball Terry B. , Brotherson Jack D. , Gardner John S.
Published: April 2011

Variation between phytoliths produced in the laminae, inflorescence bracts, and culms of einkorn (Triticum monococcum L.) were examined. Variation in the type of phytoliths produced and in the morphometries of the various types produced was evaluated. Morphometric data were obtained using computer-assisted image analysis. Types of phytoliths produced by various plant tissues included silica cell, large and small prickle, hair cell, trichome base, stomata, sheet element, long cell, and subepidermal cell phytoliths. Laterally dendriform subepidermal cell phytoliths were unique to inflorescence tissue. Long (100–250 μm), sinuate, alate trapezoid phytoliths were unique to lamina tissue. Tukey honestly significant difference comparisons indicated that there are some significant differences (p ≤ 0.05) between the mean morphometries of silica cell phytoliths produced in the lamina tissue and those produced in the culm and inflorescence tissues. Discriminant functions based on the morphometric data obtained were effective in distinguishing between populations of silica cell phytoliths extracted from each of the plant tissue types. These results suggest that (i) when preparing reference matrial for phytolith analysis, each part of a plant should be sampled and evaluated separately, and (ii) discriminant analysis of morphometric data obtained through image analysis is a potentially valuable research tool for the further development and application of phytolith systematics. Key words: phytoliths, image analysis, Triticum monococcum.
Étude biomathématique du nombre de glandes peltées des feuilles de Mentha ×piperita
Authors: Colson M. , Pupier R. , Perrin A.
Published: April 2011

The enumeration of peltate glands on Mentha ×piperata leaves was carried out with respect to the date of leaf initiation and the state of its development. For this purpose, observations were made using scanning electron microscopy associated with a mathematical method based on a precise description of gland dispersal on the leaf blade surface. The number of glands can thus be estimated by using only a few photographs of the foliar region located at 2/5 of the leaf length, measuring from the base. The analyses demonstrate a consistency in the number of peltate glands for a given foliar verticil, when the leaf height is equal to or greater than 10 mm. Furthermore, these analyses indicate that the number of peltate glands vary as a function of the level of the foliar verticil. This number increases progressively in verticils 1 to 10, stabilizes, and then decreases in the last verticils produced. This reduction may originate in the meristematic activity that is gradually oriented towards efflorescence. Key words: Mentha, glandular trichomes, enumeration, spatial distribution, leaves, scanning electron microscopy. [Journal translation]
Diseases of Amaranthus spp. caused by Pythium aphanidermatum and Macrophomina phaseolina
Authors: Mihail J. D. , Champaco E. R.
Published: April 2011

Experimental plantings of several species and crosses of Amaranthus were monitored during the 1990–1992 growing seasons to identify diseases that might limit commercial production of grain amaranth in Missouri. Two diseases, previously unreported on the Amaranthus spp. being evaluated in Missouri, are described. Pythium stem canker, caused by Pythium aphanidermatum, was observed when high temperatures coincided with prolonged periods of soil saturation. Tan cankers with black borders developed at the soil line on nearly mature (flowering) plants and lodging was associated with 2.7% of plants examined. Of the species and crosses examined, A. cruentus (cultivar K436) and A. hypochondriacus × A. hybridus (cultivars K432, K433, and K593) were affected most severely by the disease. Differences in susceptibility among the 11 cultivars suggest the potential for the development of disease-resistant cultivars. Charcoal rot, caused by Macrophomina phaseolina, affected A. hypochondriacus × A. hybridus (cultivars K432 and K433) growing in two mid-Missouri locations in 1990. Key words: Amaranthus cruentus, Amaranthus hypochondriacus, Amaranthus hypochondriacus × Amaranthus hybridis, charcoal rot, grain amaranth, stem canker.
Survival of seedling cohorts of a tropical legume on a sand dune system along the Gulf of Mexico: influence of germination date
Authors: Martinez M. Luisa , Moreno-Casasola Patricia
Published: April 2011

Chamaecrista chamaecristoides is a legume endemic to the coastal sand dunes along the coasts of Mexico. Hard-coat dormancy of seeds is broken through naturally occurring temperature fluctuations, and seedlings can emerge and establish throughout the year. In the study site, winter storms (called Nortes) are responsible for moving large quantities of sand that bury young seedlings. The objectives of the study were (i) to elucidate the timing of seedling emergence, (ii) to investigate the effect of date of emergence on seedling survival, and (iii) to evaluate different factors of mortality. Seedling survival was monitored under natural conditions, from January 1988 to April 1991. Survivorship curves were compared using the log-rank Peto and Peto test. It was found that the probability of survival or reproduction was not strictly determined by chronological age but by size. Larger sized seedlings survived better during the Nortes. Timing of germination has a great impact on C. chamaecristoides populations, since it affects seedling growth possibilities and thus survival and reproduction. In a changing environment like the sand dunes, there seems to be a selective advantage for maintaining cohorts germinating during different seasons of the year. Key words: tropical sand dunes, seedling survival, Gulf of Mexico, cohorts, seedling size.
A comparison of spatial heterogeneity of vesicular–arbuscular mycorrhizal fungi in two maple-forest soils
Authors: Klironomos John N. , Moutoglis Peter , Kendrick Bryce , Widden Paul
Published: April 2011

The variations in the numbers of propagules and in the colonization rates of vesicular–arbuscular mycorrhizal fungi in soils of two sugar maple forests, one near Waterloo in southern Ontario, the other near Lacolle in southern Quebec, were investigated. Both forests comprised similar plant communities, and in each case the most numerous mycorrhizal spores were identified as those of Glomus macrocarpum, Glomus geosporum, and Acaulospora foveata. In both forests, root colonization and length of hyphae in soil peaked in spring and again in autumn, and spore densities were highest in autumn and gradually decreased during the rest of the year. Mean percent root colonization at Lacolle was twice as high as at Waterloo, and mean spore densities were almost 10 times higher. In contrast, average total length of hyphae in the soil was approximately 10 times higher at Waterloo than at Lacolle. Sporulation by G. macrocarpum was positively correlated with soil organic matter content, and sporulation by A. foveata was negatively correlated with increasing pH. Root colonization was not correlated with spore densities but was positively correlated with the total length of hyphae in the soil. Relationships among root colonization, production of external hyphae, and spore abundance in natural ecosystems are discussed. Key words: vesicular–arbuscular mycorrhizae, Acer saccharum, environmental influences.
Flowering height and postfloral elongation of flower stalks in 13 species of angiosperms
Authors: Verbeek N. A. M. , Boasson R.
Published: April 2011

All species studied, except Lilium columbianum, flowered at or above the height of the surrounding vegetation, and the difference in height was significant. For L. columbianum and Fritillaria lanceolata we showed experimentally that they set significantly more fruit when their flowers bloomed at or above the surrounding vegetation than below it, probably because they were more visible or it was easier for pollinators to get to them. In 12 of the 13 species studied the flower stalk elongated after flowering so that the fruit capsule was above the surrounding vegetation. We showed experimentally that in F. lanceolata elongation of the flower stalk occurred intrinsically and was not brought on by extrinsic factors, such as competition for light by the surrounding vegetation. Raising the seed capsule, which opens first at the top in all species, above the surrounding vegetation probably aids in the distribution of seeds. In several species, flowering stalks that bear fruit become woody and remain standing, thus keeping the capsule exposed to the wind for some time. Postfloral elongation of the flower stalk appears related to season; early flowering species elongated the most. Key words: flowering height, fruiting height, pollination, flowering season, seed dispersal.
Low-temperature storage of monosporidial cultures of the wheat bunt fungi
Authors: Loomis Patricia , Leung Hei
Published: April 2011

Collections of Tilletia species are commonly maintained in the form of sori harvested from smutted heads. This has been a convenient and effective storage method because teliospores enclosed in a sorus remain viable for over 20 years. However, mycelial cultures derived from germinated teliospores are genetically mixed because of meiotic segregation among sporidia. For the purposes of genetic analysis and establishing strain identity, it is necessary to maintain haploid sporidial cultures that can be readily retrieved for manipulations. We found that sporidial cultures of Tilletia tritici and Tilletia controversa can be preserved for at least 1 year by suspending a mixture of mycelia and sporidia in 15% glycerol and storing at −70 °C. Approximately 80% of the stored cultures were viable after 12 months in storage. Five out of nine monosporidial cultures of T. tritici and T. controversa tested retained their sexual fertility in interspecific crosses. The glycerol storage method has advantages over serial transfer in the maintenance of monosporidial cultures by reducing the accumulation of somatic mutations; however, the technique should be used cautiously until greater infectivity of stored cultures is demonstrated. Key words: common and dwarf bunt fungi, Tilletia controversa, Tilletia tritici.
Seed mass and light requirements for regeneration in Southeast Asian rain forest
Authors: Metcalfe D. J. , Grubb P. J.
Published: April 2011

Seed mass values are given for 140 species of primary lowland rain forest and associated secondary forests in Singapore. Among shade-tolerant species of primary forest there is a trend for a decrease in mean seed mass with tall trees > woody climbers > small trees > shrubs > herbs; the differences between tall trees and small trees or shrubs or herbs, and between herbs and small trees or woody climbers are significant. There are a few light-demanding herbs or shrubs in the primary forest; among small trees, light demanders have significantly lower seed mass values than shade tolerators. In 9 out of 13 comparisons within taxa including both shade tolerants and light demanders the former had appreciably larger seeds than the latter. Two out of 13 comparisons involved very small seeded shade tolerators, and one a notably large-seed light demander. Many shade-tolerant herbs, shrubs, and trees have seed mass values much smaller than those of trees of secondary forest conventionally regarded as small seeded, and exploit moist, litter-free sites, e.g., steep microslopes. The trees of secondary forests on degraded soils do not differ significantly in seed mass from those on nondegraded soils. Key words: seed mass, light requirement, regeneration, tropical rain forest, phylogenetic analysis.
Evidence for a fungal liaison between Corallorhiza trifida (Orchidaceae) and Pinus contorta (Pinaceae)
Authors: Zelmer Carla D. , Currah R. S.
Published: April 2011

Corallorhiza trifida Châtelain, or pale coral root orchid, is a heterotrophic, leafless, rootless, terrestrial orchid with a circumboreal distribution. Because of its relative inability to photosynthesize, the orchid obtains energy through the digestion of fungal hyphae that grow within the cells of its contorted, yellowish, coralloid rhizomes. Recently, we isolated and cultured strains of a slow-growing basidiomycete with bright yellow, clamped hyphae that are typical of the fungal cells present in C. trifida endomycorrhizas from different treed habitats at widely distributed locations in the northern hemisphere. By inoculating the roots of Pinus contorta Douglas ex Loudon seedlings with this fungus we were able to demonstrate its ability to form distinctive ectomycorrhizas with an ectotrophic, woody plant. The formation of endomycorrhizas with C. trifida and ectomycorrhizas with P. contorta indicates that in nature a triple symbiosis, with a circumboreal distribution, exists among certain trees, the coral root orchid, and this yellow basidiomycete that links the two and functions as a mycorrhizal symbiont in both. Key words: Corallorhiza trifida, orchid mycorrhiza, triple symbiosis, ectomycorrhiza, Pinus contorta.
Cellular interaction of the smut fungus Ustacystis waldsteiniae
Authors: Bauer Robert , Oberwinkler Franz , Mendgen Kurt
Published: April 2011

The cellular interaction between the smut fungus Ustacystis waldsteiniae and its host Waldsteinia geoides was analyzed by serial-section electron microscopy using chemically fixed and high-pressure frozen – freeze-substituted samples. After penetration, each haustorium extends a short distance into the host cell where it often forms up to three short lobes. The haustorium is wholly ensheathed by a prominent matrix. The matrix is a complex structure, differing significantly from that known of other fungal plant parasites: it is filled with amorphous, electron-opaque material in which membrane-bounded, coralloid vesicles are embedded. During the contact phase of the hypha with the host cell wall, vesicles with electron-opaque contents accumulate in the contact area of the hypha where they appear to fuse with the fungal plasma membrane and extrude their contents. Subsequently, the host cell wall increases in electron opacity and matrix material becomes deposited between host plasma membrane and host cell wall exactly at the ends of the altered areas in the host cell wall. The coralloid vesicles within the matrix, however, are of host origin: exocytosis of Golgi products into the matrix results in the formation of coralloid vesicular buds in the host plasma membrane. Subsequently, the buds seem to detach from the host plasma membrane to flow as coralloid vesicles into the matrix. Matrix development continues during penetration and after penetration at the haustorial tips. After host wall penetration, the fungal cell wall comes in contact with the matrix. The fungal component of the matrix may play a key role in the inducement of these transfer cell-like compartments in host cells responding to infection. Key words: freeze substitution, haustoria, high-pressure freezing, host–parasite interaction, smut fungi, Ustacystis waldsteiniae.
Location of α-amylase/subtilisin inhibitor during kernel development and germination
Authors: Hill R. D. , Gubbels S. M. , Boros L. , Sumner M. J. , MacGregor A. W.
Published: April 2011

The location of an endogenous α-amylase/subtilisin inhibitor in developing and germinating barley (Hordeum vulgare, cv. Bonanza) was determined using immunohistochemical techniques. The inhibitor was found within protein bodies of cells containing starch granules in the starchy endosperm and embryo of developing caryopses. It could be detected as early as 2 weeks postanthesis in both organs. Upon germination, inhibitor was released from protein bodies, resulting in increased detection of the protein in regions of the starchy endosperm in which storage mobilization was occurring. Antibodies to α-amylase revealed large quantities of this protein in the same regions. Key words: α-amylase, α-amylase/subtilisin inhibitor, barley, germination, kernel development, starch.
Developmental patterns of leaves in Podostemaceae compared with more typical flowering plants: saltational evolution and fuzzy morphology
Authors: Rutishauser Rolf
Published: April 2011

Leaves and stems of flowering plants have been widely accepted as clearly distinguishable structural categories. Evolution, however, can blur the stem–leaf (axis–appendage) distinction. Compound leaves with apical growth and three-dimensional branching may be seen as developmental mosaics sharing some growth processes with leafy stems (shoots). To cope with fuzzy boundaries between structural categories, fuzzy morphology is proposed as a complementary way of looking at higher plant architecture. Fuzzy morphology treats structural categories (e.g., leaves and stems) as concepts with fuzzy (not sharp) boundaries. The developmental morphology of compound leaves is described comparing Apium repens (Apiaceae) with less typical angiosperms ("misfits") of the rheophyte family Podostemaceae, especially Marathrum rubrum, Mourera fluviatilis, and Tristicha trifaria. In some taxa within the Podostemaceae, typical leaf characteristics may be replaced by new properties, e.g., 90° switch of symmetry plane of the leaf primordium with production of pinnae or lobes along the adaxial and abaxial margin in Marathrum rubrum and Mourera fluviatilis. In Tristicha trifaria, compound photosynthetic appendages (called ramuli) combine developmental characters of typical leaves and typical stems. Thus, they may be called leaf-stem intermediates. Fuzziness of structural categories such as leaf and stem is especially obvious in Podostemaceae, which can be seen as the result of saltational evolution. The structural categories of typical flowering plants are transcended in the Podostemaceae because of developmental changes, resulting in organs with unique combinations of features. Key words: leaf development, developmental mosaic, Apium, Marathrum, Mourera, Tristicha.
The distribution and phenology of arbuscular mycorrhizae along an inland salinity gradient
Authors: Johnson-Green Perry C. , Kenkel Norm C. , Booth Thomas
Published: April 2011

The distribution and seasonal patterns of arbuscular mycorrhizal fungi activity were studied in an inland boreal salt pan site in north-central Manitoba. Semipermanent study regions were set up in each of five vegetation zones along a continuous salinity gradient. Roots of Hordeum jubatum, Distichlis stricta, Agropyron trachycaulum, Sonchus arvensis, Spartina gracilis, and other species were collected from the study regions over six time periods: April, June, July, August, and October of 1991, and May of 1992. These roots were used to quantify mycorrhizal colonization, as well as arbuscule and vesicle formation. Arbuscular mycorrhizal fungi were prevalent in the three vegetation zones with lowest soil salinity, with > 40% of the observed root pieces colonized. Colonization was < 2% in the other two zones, where soil salinity was consistently greater throughout the growing season. The only common pattern in the phenology of mycorrhizal activity was a low level of activity in the early spring. Mycorrhizal activity in most plant species occurred at high levels throughout the summer and fall. Differences in patterns of activity appeared to be linked to differences in phenology of root growth, and not to edaphic differences among vegetation zones. Key words: Manitoba, arbuscules, fungi, gradient, mycorrhiza, phenology, salinity, vesicles.
Étude comparée des premières étapes de l'infection chez des bananiers sensibles et résistants infectés par le Cercospora fijiensis (Mycosphaerella fijiensis) agent responsable de la maladie des raies noires
Authors: Beveraggi A. , Mourichon X. , Sallé G.
Published: April 2011

A study of the first infection stages of banana by Cercospora fijiensis was carried out using an experimental host–parasite system including three cultivars, Yangambi km5 (Musa, AAA, Ibota subgroup), Fougamou (Musa, ABB, Pisang awak subgroup), and Grande naine (Musa, AAA, Cavendish subgroup). These cultivars are representative of three host responses to infection: highly resistant (cessation of the infection process after the first streak stage), partially resistant, and susceptible. Observations on the early stages of infection and the chronology of events linked to the host plant (cellular necrosis) and to the parasite (cessation of growth) showed two different interactions in cvs. Fougamou and Yangambi. These observations were confirmed by an ultrastructural study. Partial resistance in cv. Fougamou appeared to be partly linked to a préexistent anti-fungal, plant phenolic component. In the highly resistant cv. Yangambi, an active defense mechanism took place just after penetration of stomata by the fungus. Key words: Cercospora fijiensis, banana, host–parasite interactions, mechanisms of resistance, polyphenols.
Isoetes × marensis, a new interspecific hybrid from western Canada
Authors: Britton Donald M. , Brunton Daniel F.
Published: April 2011

A new interspecific hybrid in Isoetes, I. maritima Underw. × I. howellii Engelm., is delineated and described from the Shuswap Highlands region of British Columbia by means of cytology and scanning electron microscopy of spores. Isoetes × marensis D.M. Britton and D.F. Brunton, hyb.nov. is the name proposed for this taxon. It is triploid (3x; 2n = 33) and is believed to produce only sterile and (or) aborted spores. Hybrid plants have polymorphic spores that demonstrate size and surface ornamentation features intermediate between those of the putative parents. Three populations were examined, each growing with both of the putative parents in silt and sand among granite cobble over clay along an emergent lakeshore. Isoetes × marensis is the first described North American hybrid involving an amphibious Isoetes. It is expected to be a rare taxon owing to the restricted sympatric area of the putative parents and their tendency to occupy different habitats. Key words: Isoetes, Isoetes howellii, Isoetes maritima, hybrid, British Columbia.
Life-history traits and ploidy levels in the genus Capsella (Brassicaceae)
Authors: Neuffer Barbara , Eschner Silke
Published: April 2011

In a random block field experiment, life-history traits associated with colonizing ability of diploid and tetraploid cytotypes of Capsella (Brassicaceae) were compared. These were germination, flowering, growth-form parameters, and leaf shape. Data are not in favour of differences in germination behaviour between the diploid and tetraploid Capsella species, as germination rate and capacity are highly influenced by inception and release of seed dormancy. Although our data at first glance seem to suggest that diploid C. rubella start flowering later than tetraploid C. bursa-pastoris, considerable ecotypic variation for flowering in both species makes it difficult to assign an effect specifically to ploidy level. We also conclude that plant height, rosette diameter, and branching number are not directly determined by ploidy level. In contrast however, leaf shape is clearly determined by ploidy level. In the light of all available data including data of previous experiments, we suggest that gene duplication by polyploidization may have been a key element that provided C. bursa-pastoris with additional genetic flexibility. It is not primarily the gain of colonization ability, as both species are weeds and colonizers. Rather, the greater genetic flexibility enabled C. bursa-pastoris to extend its range beyond that of C. rubella. Key words: ploidy level, germination, flowering, growth form, leaf morphology, Capsella.
Diversité morphologique en culture, sensibilité au carbendazime et pouvoir pathogène du Tapesia yallundae (anamorphe : Pseudocercosporella herpotrichoides)
Authors: Frei Peter , Gindrat Daniel
Published: April 2011

Three types of colonies (WH, WA, and RA) have been characterized among 2245 isolates of Pseudocercosporella herpotrichoides on the basis of colony growth rate and appearance (W, rapid growth and regular margin; R, slow growth and irregular margin) and of the shape of the majority of conidia (H, coiled; A, straight). Apothecia of Tapesia yallundae (anamorph : P. herpotrichoides) were produced on naturally infected stems of winter wheat and barley. Apothecia of an undetermined discomycete were occasionally observed. The progeny of more than 1700 ascospores from 72 apothecia of T. yallundae was distributed among the three types of colonies. These types remained stable through successive conidial and mycelial subcultures. All three colony types were sometimes obtained from a single apothecium. WH and WA were the most common, while RH was never observed. WA isolates were more often resistant than WH isolates to carbendazim. Inoculations of wheat and barley stems with ascospores of T. yallundae were unsuccessful, while inoculations with conidia or mycelium resulted in eyespot lesions. During equivalent periods, RA isolates were less virulent than WH and WA. Key words: cereals, eyespot, Deuteromycetes, sexual stage, Hordeum vulgare, Triticum aestivum.
Effect of landscape position on plant diversity and richness on electric transmission rights-of-way in New York State
Authors: Cameron Donald S. , Leopold Donald J. , Raynal Dudley J.
Published: April 2011

Rights-of-way are kept free of tall trees to insure reliability of electric service. Selective management techniques such as application of cut-stump herbicide and stem foliar herbicide are used on some rights-of-way to remove undesirable tree species while minimizing disturbance to shrub and herbaceous vegetation. Because rights-of-way typically traverse broad productivity and disturbance gradients over large geographic areas and harbor both native and non-native species, they offer unique opportunities to study plant species diversity patterns and their underlying causes at different scales. Plant cover on six managed rights-of-way in forested landscapes of New York State was sampled to determine the effect of landscape position (i.e., xeric, mesic, and hydric sites) on species composition, diversity, and richness and contribution of non-native species. Species composition among sites was compared using redundancy analysis in which the individual covers of the most common species were ordinated with treatment levels. Diversity, species richness, and contribution of non-native species were compared using analysis of variance. Redundancy analysis shows trends in the occurrence of common species based on landscape position. Analysis of variance indicates diversity, richness, and contribution of non-natives are greater on the rights-of-way versus the adjacent woods for xeric and mesic positions, whereas no differences were indicated between rights-of-way and adjacent woods for hydric positions. Key words: rights-of-way, selective management, diversity, competition, stress, invasive species.
Oxygen photoreduction and its effect on CO2accumulation and assimilation in air-grown cells ofSynechococcusUTEX 625
Authors: Li Qinglin , Canvin David Thomas
Published: April 2011

Mass spectrometric measurements of16O2,18O2, and13CO2were used to measure the rates of gross O2evolution, O2uptake, and CO2assimilation in relation to light intensity, temperature, pH, and O2concentration by air-grown cells of the cyanobacterium Synechococcus UTEX 625. CO2fixation and O2photoreduction increased with increased light intensity and, although CO2fixation was saturated at 250 μmol ∙ m−2 ∙ s−1, O2photoreduction was not saturated until about 550 μmol ∙ m−2 ∙ s−1. At high light intensity addition of inorganic carbon to the cells stimulated O2photoreduction 2-fold when CO2, fixation was allowed and 5-fold when CO2, fixation was inhibited with iodoacetamide. The ability of O2, to act as an acceptor of photosynthetically generated reducing power was dependent upon the O2concentration, and the substrate concentration required for half maximum rate (K½(O2)) was 53.2 ± 4.2 μM (mean ± SD, n = 3). The Q10for oxygen photoreduction was about 2. A certain amount (10%) of O2appeared to be required for maximum photosynthesis, as photosynthesis was inhibited under anaerobic conditions, especially at high light intensity. The point of inhibition is unknown but it seemed unlikely to be on CO2transport or the concentration of intracellular dissolved inorganic carbon (Ci), as the rate of initial CO2transport was enhanced and the intracellular Q1pool increased in size under anaerobic conditions. Key words: cyanobacteria, photosynthesis, Ciconcentrating mechanism, inorganic carbon pool, O2photoreduction, electron transport, temperature.
Isoetes × carltaylorii (Isoetes acadiensis × Isoetes engelmannii), a new interspecific quillwort hybrid from the Chesapeake Bay
Authors: Musselman Lytton J. , Bray Rebecca D. , Knepper David A.
Published: April 2011

Isoetes acadiensis Kott is a plant of the Maritime provinces of Canada and the northeastern United States. In the Chesapeake Bay region, this quillwort has previously been misidentified as Isoetes riparia Engelm., Isoetes saccharata Engelm., or Isoetes saccharata var. reticulata A.A. Eaton. Isoetes × carltaylorii hyb.nov. is the hybrid between I. acadiensis (2n = 44) and Isoetes engelmannii A. Braun (2n = 22). This is the first report of a hybrid with I. acadiensis. An apparently sterile triploid (2n = 33), this rare plant of freshwater tidal marshes has the predicted range of sizes and megaspore features of a hybrid. This brings to 14 the number of interspecific quillwort hybrids described from North America since 1985. Key words: Isoetes saccharata var. reticulata, Isoetes riparia, Isoetes saccharata, megaspores, tidal freshwater rivers.