bluuebunny/crossref_metadata_2025 huggingface dataset:
Interactions of two strains of Magnaporthe grisea with rice, goosegrass, and weeping lovegrass
Authors: Heath Michèle C. , Valent Barbara , Howard Richard J. , Chumley Forrest G.
Published: April 2011

Two strains of the fungus Magnaporthe grisea caused responses in goosegrass, weeping lovegrass, and rice that varied from no visible symptoms, through isolated discrete lesions with or without brown margins, to coalescing lesions that completely killed the inoculated areas of the leaf. The fungus sporulated under conducive conditions in all of the five plant–strain combinations that produced visible symptoms, but the degree of sporulation varied considerably. Microscopical examination revealed a previously unreported dimorphism in the infection hypha in all three plant species. In all combinations, some appressoria failed to form infection hyphae. In all but one combination, some infection hyphae failed to differentiate and (or) became restricted to a single epidermal cell with autofluorescent walls. Quantitative data showed that the presence and density of lesions reflected the frequency with which appressoria formed growing fungal colonies; lesion appearance depended on the interaction between such colonies and the leaf tissue. The results suggest that the different plant–strain combinations represent a continuum of plant–fungus interactions, and that small differences in the frequency of different plant–fungus interactions at the cellular level may have significant effects on macroscopic symptom development.
Kathistes, a new genus of pleomorphic ascomycetes
Authors: Malloch D. , Blackwell M.
Published: April 2011

The genus Kathistes is described to accomodate two new species, K. calyculata and K. analemmoides, and an existing one based on Pyxidiophora fimbriata Barrasa & Moreno. All three species are coprophilous and produce transversely septate ascospores in long-necked perithecia. Ascospore germination occurs by the production of budding yeast cells. Sporelike bodies, termed sporidiolae, are produced in spherical structures resembling the perithecia called sporidiomata. Similar genera and species are discussed and contrasted by a dichotomous key. Kathistes species do not appear to be closely related to other ascomycetes and are assigned to a new family Kathistaceae.
Effects of environmental stress factors on ectomycorrhizal fungi in vitro
Authors: Willenborg Antonius , Schmitz Doris , Lelley Jan
Published: April 2011

The reaction of various ectomycorrhizal fungi to environmental stress factors was examinated in a screening program. Tolerance to acid and heavy metals, resistance to antagonists, and reactions to automobile exhaust fumes were tested. Differences in reaction between the several ectomycorrhizal species and strains were observed. These results confirm that the susceptibility of ectomycorrhizal fungi to environmental stress factors varies from species to species, but also from strain to strain within a species. Pure culture synthesis with Picea abies showed the symbiotic potential of the selected fungi. Key words: ectomycorrhizal fungi, Picea abies.
Occurrence and distribution of aspartate aminotransferases in spruce and beech ectomycorrhizas
Authors: Chalot Michel , Brun Annick , Khalid Ahmed , Dell Bernard , Rohr René , Button Bernard
Published: April 2011

Activities and localization of aspartate aminotransferases (AAT) were determined in spruce and beech ectomycorrhizas, as well as in nonmycorrhizal roots and fungi in pure culture. Preliminary data emphasized the importance of AAT in amino acid synthesis; thus, aspartate derivatives (asparagine, citrulline, and arginine) accounted for about 63% of the total nitrogen of the free amino acid pool. Specific activities were in the same range for both symbiotic tissues and free-living partners; however, electrophoretic patterns revealed that the two host isoforms were detected in ectomycorrhizal tissues, whereas the single fungal isoform was absent in the associations investigated. Dissection of the symbiotic tissues into three parts (vascular cylinder, cortical region, and mycelial layer) confirmed these results: the cortical region, including both host and fungal cells, contained only the two host isoforms. Results from immunological tests and immunocytochemical labelling using antibodies raised against fungal AAT were also consistent with a strong suppression of the fungal AAT accumulation in the association. Implications of fungal AAT repression in the symbiotic tissues are discussed.
Effects of sucrose concentration on the accumulation of anthocyanins in grape (Vitis vinifera) cell suspension
Authors: Cormier François , Crevier Hélène A. , Do Chi Bao
Published: April 2011

A cell suspension of Vitis vinifera L. cv. Gamay Frédaux var. teinturier composed of 50% pigmented cells was grown in Gamborg B5 medium supplemented with (per litre) 250 mg casein hydrolysate, 0.1 mg α-naphthalenacetic acid, 0.2 mg kinetin, and either 20, 30, 50, or 60 g sucrose. In the presence of 20 and 30 g sucrose/L, growth of cells was characterized by a typical sigmoid pattern and maximum cell density was obtained in 30 g sucrose/L. In both media, the anthocyanin content of pigmented cells did not change significantly throughout the growth cycle. In the presence of 50 g sucrose/L, cell growth was characterized by an extended lag phase. During this period, there was a significant (P < 0.05) accumulation of anthocyanins in the pigmented cells. Browning of the medium and premature cell death was observed in medium with 60 g sucrose/L. Microscopic observation of the suspension revealed the occurrence of anthocyanoplasts, especially in anthocyanin-containing cells cultured in 50 g sucrose/L. In some instances anthocyanoplasts were observed in cells with nonpigmented vacuoles, thus supporting the thesis according to which anthocyanoplasts would be the site of anthocyanin synthesis. Key words: anthocyanins, anthocyanoplasts, cell culture, metabolism, sucrose, Vitis vinifera.
A revision of the genera Antromycopsis, Sclerostilbum, and Tilachlidiopsis (Hyphomycetes)
Authors: Stalpers Joost A. , Seifert Keith A. , Samson Robert A.
Published: April 2011

The anamorphic genera Antromycopsis, Sclerostilbum, and Tilachlidiopsis are revised. Three anamorph species with basidiomycetous affinities are accepted in Antromycopsis: A. macrocarpa (Ellis & Everh.) comb.nov. (basionym Stilbum macrocarpum), previously known as A. broussonetiae (teleomorph: Pleurotus cystidiosus), A. angustata sp.nov. for the presumed anamorph of Pleurotus angustatus, and A. guzmanii sp.nov. (teleomorph Pleurotus smithii). A description and illustration are presented of the type species of Tilachlidiopsis, T. racemosa, the anamorph of Collybia racemosa. Sclerostilbum is considered a taxonomic synonym of Tilachlidiopsis. Nothoclavulina ditopa, the anamorph of Arthrosporella ditopa, is illustrated and briefly discussed. Key words: anamorph–teleomorph connections, Antromycopsis, Sclerostilbum, Pleurotus, Collybia, nematophagous fungi.
Fungal communities in winter wheat roots following crop rotations suppressive and nonsuppressive to take-all
Authors: Sturz A. V. , Bernier C. C.
Published: April 2011

Mycofloral communities colonizing winter wheat roots were quantified in five crop sequences involving winter wheat preceded by either spring wheat, spring oats, spring barley, spring canola, or flax. Fungi were categorized into groups (major pathogenic, minor pathogenic, and nonpathogenic) based on their ability to cause root disease. Forty-six species of fungi were identified, of which the principal species were Alternaria alternata, Fusarium acuminatum, and Microdochium bolleyi. Isolates from the genus Fusarium formed the largest proportion of the mycofloral community. Fungal species that comprised root-colonizing communities were generally the same, and there were no significant differences in the total numbers of fungal species and isolates recovered in any of the crop sequences examined. However, the ratio of major pathogenic isolates to other isolates (minor pathogenic and nonpathogenic) was significantly different (in 1985) and a trend towards lower levels of root disease with decreasing ratios was seen. The most destructive of the root rot pathogens identified was Gaeumannomyces graminis var. tritici. Generally, the lowest ratio of major pathogenic to all other isolates and the lowest levels of root disease and root colonization (expressed as numbers of fungal isolates and species recovered) occurred in sequences involving flax and canola.
A clarification of Medicago sinskiae
Authors: Small Ernest , Brookes Brenda
Published: April 2011

Little information has been available to justify the species status of the rare Turkmenian Medicago sinskiae Uljan. recognized by Uljanova in 1964. The holotype and plants raised from its seeds were examined, the chromosome number was determined, and a numerical taxonomic comparison was made of M. sinskiae and the other 12 species of Medicago section Spirocarpos subsection Pachyspirae. It was found that M. sinskiae is well separated from the most closely related species of Medicago and deserves recognition at the rank of species. Key words: Medicago sinskiae, Leguminoseae, alfalfa, taxonomy.
Environmental and genetic influences on phenology and plant size in a perennial herb, Senecio integrifolius
Authors: Widén Björn
Published: April 2011

Individual plants of the perennial herb Senecio integrifolius showed a highly significant correlation between rank order of the dates of first flowering and of first fruiting in a natural population and in cultivation. Plants exposed to full sunshine were smaller and flowered earlier than shaded plants both in a natural population and in cultivation. Within the two groups, plants with large inflorescences started to flower first. Duration of flowering was regulated by the size of the inflorescence; plants with many heads flowered longer than plants with few heads. There was a significant correlation between phenological rank order of mother plants in natural populations and their progenies in cultivation, but no consistent relationship between mother size and progeny size was found. Cultivated plants were consistent in rank order of flowering and in size over the years. Key words: flowering phenology, plant size, genetic variation, Senecio.
Ultrastructural interactions of one strain of Magnaporthe grisea with goosegrass and weeping lovegrass
Authors: Heath Michèle C. , Howard Richard J. , Valent Barbara , Chumley Forrest G.
Published: April 2011

In leaves of the susceptible host, weeping lovegrass, strain 4091-5-8 of the rice blast fungus, Magnaporthe grisea, elicited no ultrastructurally detectable responses of underlying epidermal cells during appressorium development or penetration peg formation. During the subsequent growth of the fungus both inter- and intra-cellularly, leaf cells initially showed little obvious response even after fungal penetration, although the cytoplasm of invaded cells eventually became disorganized. In leaves of the less susceptible goosegrass, successful penetration from appressoria was rare and usually resulted in rapid death of both fungus and epidermal cell. Most frequently, however, fungal growth ceased at various stages during the formation of the penetration peg, in association with the deposition of highly electron-opaque material in the underlying epidermal wall. From their ultrastructural appearance, and their natural electron opacity after osmium removal with periodate, these deposits appeared to contain silica. Key words: rice blast, wall appositions, silica.
Amelioration of copper and nickel toxicity by iron plaque on roots of rice (Oryza sativa)
Authors: Greipsson S. , Crowder A. A.
Published: April 2011

Deposition of an iron oxide plaque or coating on roots of rice (Oryza sativa L. cv. M-201 84 Biggs) ameliorated the toxic effects of copper (Cu), nickel (Ni), and Cu + Ni on plant growth and affected patterns of metal uptake and accumulation. Plaque was formed on plants during 24 h in an anaerobic solution containing 20 mg ∙ L−1 iron at pH 5.5. Subsequently two additional coatings were deposited after new growth of roots. Plants were grown hydroponically in one-quarter strength Hoagland's solution and exposed to Cu (0.5 mg ∙ L−1), Ni (2.0 mg ∙ L−1), or Cu + Ni; exposure to metals lasted 21 – 45 days. At the end of the experimental period growth was estimated as total biomass, dry weight of root, dry weight of shoot, length of leaf, and length of root. After harvesting, Fe, Cu, and Ni concentrations in plaque were measured using a dithionite–citrate–bicarbonate extraction, and internal Fe, Cu, and Ni concentrations were measured in roots and leaves using atomic absorption spectrophotometry. Formation of the palque did not affect growth of plants in control solutions. When exposed to Cu, plants with plaque had significantly larger biomass, dry weight of roots, dry weight of leaves, and growth increments of root and leaf than plants without plaque. When exposed to Ni, plants with plaque had signifiantly higher increment in leaf growth than plants without plaque. When exposed to Ni + Cu, plants with plaque had significantly higher biomass than plants without plaque. Toxic symptoms were not observed on plants with plaque grown with excess copper, while all other plants exposed to metals showed chlorosis, necrosis, or both. Metals were detected on the surface of roots, whether plants were allowed to develop a plaque or not. Cu, Ni, and Fe were concentrated in plaque and in roots. Lower concentrations of Cu and Ni were found in leaves of plants with a plaque than in plants without plaque. Comparisons of concentrations of Fe, Cu, and Ni with those of other species grown under field conditions are made. Key words: rice, iron plaque, toxicity of Cu and Ni.
Microtubular and actin filament configurations during microspore and pollen development in Brassica napus cv. Topas
Authors: Hause G. , Hause B. , Lammeren A. A. M. Van
Published: April 2011

The structures of the microtubular and microfilamental cytoskeletons were investigated during the development of microspores and pollen grains of Brassica napus L. cv. Topas. Microfilaments were observed directly with rhodamine–phalloidin and microtubules with FITC by indirect immunofluorescent staining and transmission electron microscopy. We observed microtubules in all developmental stages and noted several changes in the configuration of the microtubular cytoskeleton during microspore development, microspore mitosis, and pollen development. A preprophase band before microspore mitosis was not observed. The arrest of the microspore nucleus in an eccentric position is likely caused by microtubules as is the shape of the phragmoplast at microspore mitosis. Despite the application of various staining methods, i.e., labelling of fixed and unfixed fresh and cryosectioned microspores and pollen with rhodamine–phalloidin, microfilaments could not be observed in all developmental stages. Prominent microfilamental arrays were observed during cytokinesis of microspore mitosis and during the free generative cell stage. They mark the stages with different configurations. Key words: Brassica napus, immunolabelling, cytoskeleton, microspore and pollen development.
Relations entre organogénèse apicale et croissance dimensionnelle de la tige principale du soja (Glycine max)
Authors: Barthou Henri
Published: April 2011

The relationships existing between apical morphogenesis and dimensional growth kinetics in the development of the main stem of soja (Glycine max (L.) Merr.) were quantified applying Nelder's generalized logistic with different population densities. Evidence was obtained that, from a morphogenetic standpoint, dimensional growth activity of the stem was more important than that of its organogenesis and that the peak activities of these processes were chronologically out of phase, thus showing two successive periods dominated first by organogenic activities and then by growth. Data show that population density has a greater effect on growth activities than on development and that its effects are exerted earlier on organogenesis and more progressively on growth. Key words: growth, population, density, Glycine max, organogenesis, soja. [Journal translation]
Embryology of Brassica campestris: the entrance and discharge of the pollen tube in the synergid and the formation of the zygote
Authors: Sumner M. J.
Published: April 2011

The postanthesis synergids and zygote of Brassica campestris cv. Candle were examined using techniques of light, fluorescence, and electron microscopy. The pollen tube enters the degenerate synergid by way of the filiform apparatus. A degeneration of one of the two synergids occurs after anthesis and is independent of pollination. The first sign of synergid degeneration is a more intense staining of one of the synergids, followed by a loss of organelle membrane integrity. There is a disappearance of the plasma membrane and dictyosome cisternae; however, profiles of degenerate synergid mitochondria, plastids, and dilated endoplasmic reticulum remain along with dictyosome vesicles that contain periodic acid – thiocarbo-hydrazide – silver proteinate positive substances. The zygote, shortly after fertilization, is reduced in size and lacks the large micropylar vacuole characteristic of the mature unfertilized egg cell. Plastids and mitochondria are concentrated around the centrally located nucleus of the zygote, and dictyosomes, active in vesicle production, are located in the lateral and chalazal regions of the cell, adjacent to the cell wall. The lateral cell walls are periodic acid – Schiff's and Calcofluor positive, while the ampulliform chalazal tip of the cell is weakly periodic acid – Schiff s positive and Calcofluor negative. Microtubules, with the long axis perpendicular to the long axis of the zygote, are abundant in the ampulliform chalazal tip of the cell. Following fertilization the central cell becomes highly vacuolate. There is continuity between the zygote – central cell plasma membrane, the central cell vacuole tonoplast, and membranes of the central cell endoplasmic reticulum. Central cell wall projections, of the transfer cell type, are located in the lateral regions of the megagametophyte adjacent to the developing zygote cell and are positioned adjacent to the region of inner and outer integument starch. Key words: Brassica, ultrastructure, synergid, megagametophyte, pollen tube, zygote.
Applanodictyosporous Pleosporales: Clathrospora, Comoclathris, GraphyIlium, Macrospora, and Platysporoides
Authors: Shoemaker R. A. , Babcock C. E.
Published: April 2011

Six genera of the order Pleosporales are revised taxonomically. Although five genera have unusual applanate ascospores, they are members of three different families. Clathrospora (10 species, 2 new), Comoclathris (21 species, 7 new), and Macrospora (3 species) are placed in a new family Diademaceae in which the ascoma opening is a characteristic flat circular lid. Diademosa, a new genus with one species with terete ascospores is placed in Diademaceae. Graphyllium (3 species) is placed in the family Hysteriaceae characterized by hysterothecia with a slit-like opening. Platysporoides n.gen. (11 species, 1 new) is maintained in the Pleosporaceae because of the terete pored beak of the ascomata. Key words: Pleosporales, applanate ascospores, Clathrospora, Comoclathris, Macrospora, Diademosa, Graphyllium, Platysporoides.
Effect of snow-free duration on leaf life-span of four alpine plant species
Authors: Kudo Gaku
Published: April 2011

Leaf life-spans and specific leaf weights of four plant species, Phyllodoce aleutica, Rhododendron aureum, Sieversia pentapetala, and Potentilla matsumurae were compared along a gradient of decreasing snow-free duration in alpine snow beds. Life-span was obtained by observation from emergence to senescence for deciduous plants and was estimated from leaf age distributions for evergreen plants. Along the gradient, the evergreen shrubs Ph. aleutica and R. aureum had extended leaf life-spans, whereas the deciduous shrubs S. pentapetala and the deciduous herb Po. matsumurae had reduced leaf life-spans. Specific leaf weights, obtained by dry weight per unit leaf area, increased in Ph. aleutica but decreased in S. pentapetala and Po. matsumurae along the gradient. These phenomena are considered adaptive adjustments for maintaining a positive carbon balance under the conditions of limited photosynthetic season. Key words: alpine snow bed, carbon balance, deciduous plants, evergreen plants, leaf life-span, specific leaf weight.
Evaluation of a fungal antagonist, Phaeotheca dimorphospora, for biological control of tree diseases
Authors: Yang D. , Plante F. , Bernier L. , Piché Y. , Dessureault M. , Laflamme G. , Ouellette G. B.
Published: April 2011

Phaeotheca dimorphospora, which was first isolated from elm wood and found to be antagonistic in vitro against the Dutch elm disease pathogen Ophiostoma ulmi, was tested for antifungal activity in vitro against other tree pathogens by a variation of the agar layer technique. Phaeotheca dimorphospora produced antifungal compounds that were strongly inhibitory against a wide range of tree pathogens in addition to O. ulmi, such as Gremmeniella spp., Armillaria spp., Septoria musiva, Verticillium albo-atrum, Cylindrocladium floridanum, Phytophthora sp., Nectria galligena, and Heterobasidion annosum. Under light and interference microscopy, four types of morphological changes were observed in the pathogens tested: swelling of hyphae, production of resting spores such as chlamydospores and of sclerotia, extrusion of cytoplasm from hyphal tips, and bursting and destruction of mycelium. Chloroform-soluble antagonistic compounds were extracted that showed both fungicidal and fungistatic effects on the test organisms. Key words: Phaeotheca dimorphospora, biological control, fungal antagonist, hyphal interactions, antifungal metabolites, tree diseases.
Description and pathogenicity of Cylindrocladium ovatum sp.nov.
Authors: El-Gholl N. E. , Alfenas A. C. , Crous P. W. , Schubert T. S.
Published: April 2011

Cylindrocladium ovatum El-Gholl, Alfenas, Crous, et Schubert sp.nov., the cause of a leaf spot disease on Eucalyptus urophylla in Para, Brazil, is described and is shown to be a pathogen on Eucalyptus grandis, Eucalyptus robusta, Eucalyptus terelicornis, and Eucalyptus torelliana. Key words: Cylindrocladium ovatum, Eucalyptus urophylla, leaf spot disease.
Combined effects of hormones and light during growth promotion in primary leaves of Phaseolus vulgaris
Authors: Brock Thomas G.
Published: April 2011

Cell enlargement in primary leaves of bean is promoted by bright white light, gibberellic acid, or the cytokinin N6-benzyladenine. I examine the combined effects of light and hormones on growth, cell wall properties, and osmotic parameters during growth over 24 h. Applied alone, benzyladenine (10 μM), gibberellic acid (10 μM), and white light produced similar increases in the length and fresh weight of excised leaf strips over 24 h. The combined effects of hormones and light on growth were much less than additive. Individually, all three treatments significantly increased cell wall plastic extensibility over 24 h. However, benzyladenine combined with white light were additive in effect on plastic extensibility, and gibberellic acid combined with white light were synergistic. The differences in effects of hormones in white light on growth versus plastic extensibility indicate a decrease in growth potential, which is attributable in part to hormonal effects on osmotic concentration. Although white light alone increased osmotic concentration, both benzyladenine and gibberellic acid greatly decreased it, with or without white light. Furthermore, because growth potential is a function of both osmotic potential and wall yield threshold, it appears that yield threshold does not decline in parallel with osmotic potential in hormone-treated bean leaf strips. Finally, both benzyladenine and gibberellic acid inhibit the increase in osmotic solutes normally produced by white light. This effect, coupled with water uptake during cell expansion, would produce the observed decreases in osmotic concentration in hormone-treated strips. Hence, both benzyladenine and gibberellic acid interfere with light-induced growth, primarily through effects on the apparent ability of light to direct solute accumulation. Key words: Phaseolus vulgaris, leaf growth, cytokinin, gibberellic acid, light.
Components of seed mass and their relationships to seedling size in Calamovilfa longifolia
Authors: Zhang Jianhua , Maun M. A.
Published: April 2011

Greenhouse studies were conducted to determine the relative contribution of endosperm and embryo masses to seed mass and seedling size in Calamovilfa longifolia. Seed mass in a sample varied from 0.71 to 3.17 mg per seed, and according to fitted functions, from approximately 0.26 to 2.48 mg per endosperm and from 0.15 to 0.50 mg per embryo. Both the embryo and endosperm masses were significantly correlated with mass, length, width, and area (length × width) of seeds. Seedling (2-weeks old) height, leaf area, and dry weights of leaves, stems, and roots were also highly positively correlated with seed mass. Because endosperm mass contributed much more to the variation in seed mass and showed stronger correlation with seed mass than embryo mass, seedling size may depend mainly on the amount of seed reserves in the endosperm rather than the embryo. Key words: seed mass, seedling size, embryo mass, endosperm mass, Calamovilfa longifolia.
In vitro germination of three Cypripedium species in relation to time of seed collection, media, and cold treatment
Authors: Pauw M. A. De , Remphrey W. R.
Published: April 2011

To maximize the in vitro seed germination of three Cypripedium species, C. candidum Muhl. ex Willd., C. reginae Walt., and C. calceolus var. parviflorum Salisb. Fern., the optimum time of seed collection and the suitability of various media were studied. A cold treatment was investigated for C. candidum. Seed pods were collected at regular intervals after pollination, ranging from green pods at 5 weeks to dry undehisced pods at 12 weeks. Seed was inoculated onto three media, Harvais, Van Waes and Debergh, and a modified Norstog and germination was assessed at 4-week intervals for 20 weeks. Cypripedium reginae germinated better than the other two species. Except for C. candidum in 1989 when germination peaked for seed collected at 6 weeks after pollination, seed collected at 8 weeks after pollination had the highest germination. After 8 weeks, germination decreased sharply in all species, dropping below 1% for C. candidum. There were differences among media but the effects on germination were not consistent and depended on the year, the date of collection, and the species. Subsequent development of protocorms was superior in all cases on the modified Norstog medium. The effect of cold treatment on germination of C. candidum was variable and therefore its importance is questionable. Key words: in vitro, germination, Cypripedium, lady's slippers, seed maturity.
Distribution of mineral nutrients within the leaves of common dandelion (Taraxacum officinale) galled by Phanacis taraxaci (Hymenoptera: Cynipidae)
Authors: Paquette L. C. , Bagatto G. , Shorthouse J. D.
Published: April 2011

Galls induced by the cynipid wasp Phanacis taraxaci on the leaves of common dandelion, Taraxacum officinale, alter the concentrations of various mineral nutrients found within attacked leaves. Two distinct patterns of accumulation in normal leaves, galls, and the tissues of galled leaves were observed. In the first pattern, Mn, Mg, Ca, and ash content was galled leaf > gall ≥ normal leaf, whereas in the second pattern, Cu, Zn, and Fe was gall > gall leaf ≥ normal leaf. The manner by which this gall and the insects within intercept nutrients transported down the midrib is discussed, as is the apparent variability in mineral acquisition by various gall systems. Key words: Phanacis taraxaci, gall, mineral nutrient sinks, Taraxacum.
Investigations on the nature of a graft-transmissible agent in poinsettia
Authors: Dole John M. , Wilkins Harold F. , Desborough Sharon L.
Published: April 2011

The free-branching poinsettia (Euphorbia pulcherrima) cultivar Annette Hegg Brilliant Diamond contains a free-branching agent that is graft-transmissible to the restricted-branching cultivar Eckespoint C-1 Red. Transmission electron microscopy failed to reveal evidence of bacteria, fungi, or mycoplasma-like organisms in either 'Brilliant Diamond' or 'C-1 Red' plants. Treatment of both cultivars with tetracycline-hydrochloride produced no differences in branching pattern or leaf morphology in either cultivar, indicating that the agent may not be a mycoplasma-like organism. Scions of a poinsettia mosaic virus indicator species (Euphorbia cyathophora) grafted onto 'Brilliant Diamond' and 'C-1 Red' stocks exhibited the mottling symptoms characteristic of poinsettia mosaic virus, while self-grafted E. cyathophora scions showed no mottling, indicating that poinsettia mosaic virus was not the agent. The agent was not transmitted by pin prick, carborundum, or dodder (Cuscuta sp.), and ribaviran did not eliminate expression of the branching agent from 'Brilliant Diamond' plants. No differences in double-stranded RNA banding patterns were found between extracts of free- and restricted-branching poinsettias by polyacrylamide gel electrophoresis. The double-stranded RNA was attributed to poinsettia mosaic virus and other unknown RNA viruses. Attempts to detect a specific DNA associated with free-branching were inconclusive. Key words: branching agent, Euphorbia pulcherrima, graft transformation, dsRNA, poinsettia mosaic virus.
Effects of benomyl, clipping, and competition on growth of prereproductive Lotus corniculatus
Authors: Borowicz Victoria A.
Published: April 2011

Vesicular–arbuscular mycorrhizae, defoliation, and competition can influence survival, growth, and fecundity of plants, but the combined effects of these factors are not well known. I examined how combinations of these factors influence biomass allocation and investment in root nodules by prereproductive Lotus corniculatus and whether the effects were ephemeral. Soil with vesicular–arbuscular mycorrhizal (VAM) fungi was treated with the fungicide benomyl or water and added to trays containing two L. corniculatus or one L. corniculatus and one Brassica napus (a nonmycotrophic species). Leaves of target L. corniculatus were undamaged or clipped five times over 40 days. Plants were harvested 5, 18, or 36 days after last clipping. Interspecific competition was the dominant effect at all harvests: B. napus greatly depressed growth of its neighbor. Benomyl depressed VAM colonization only in the first harvest, and growth reduction associated with depressed colonization diminished over time. Clipping reduced growth most in plants paired with conspecifics, but growth depression was transient. Benomyl and clipping reduced mass of root nodules in the first harvest. Benomyl reduced root mass in nontarget (competitor) L. corniculatus, but plants recovered with time. Neither benomyl nor clipping of the target plant affected B. napus. Interactions were few, indicating that the effects of factors were mostly additive. Key words: VAM fungi, resource allocation, nonmycotrophic competitor.
Generation means analysis of phenolic compounds in maize grain and susceptibility to maize weevil Sitophilus zeamais infestation
Authors: Serratos J. A. , Blanco-Labra A. , Mihm J. A. , Pietrzak L. , Arnason J. T.
Published: April 2011

Generations derived from crosses between inbred lines were used to analyze the genetics of hydroxycinnamic acid accumulation in maize grain and susceptibility to infestation by the maize weevil Sitophilus zeamais. There was a significant negative correlation between phenolic content and susceptibility of the grain to weevil infestation, and the estimates of genetic parameters indicate that a close relationship between those two traits exists. Key words: insect resistance, maize, maize weevil, genetics, phenolics.
Growth, nutrition, and proteolytic activity of the sap-staining fungus Ophiostoma piceae
Authors: Abraham L. D. , Roth A. , Saddler J. N. , Breuil C.
Published: April 2011

The sap-staining ascomycete Ophiostoma piceae strain 387N used ammonium, but not nitrate, as an inorganic nitrogen source. Organic nitrogen sources assimilated included bovine serum albumin, collagen, acid-hydrolyzed casein, urea, and various amino acids. Sucrose, glucose, maltose, raffinose, and soluble starch were suitable carbon sources. The optimum temperature for growth was near 23 °C, with an upper limit at 35 °C and minimal growth at 4 °C after 3 days. An initial pH of 6.1 yielded the greatest biomass. Proteolytic activity was greatest in cultures supplemented with protein as the nitrogen source, but some activity was detected in cultures with no assimilable source of nitrogen. Proteinases were detected throughout growth in protein-supplemented liquid media, and they appeared to hydrolyze azocoll, with optimal activity at pH 8. Isoelectric focusing gels of culture filtrates, obtained after fungal growth on protein supplemented media, showed a major proteolytic band focusing at pH 5.2. Key words: staining fungi, Ophiostoma, nutrition, biomass, proteinases.
Isoenzyme analysis of teliospores from species of Anthracoidea parasitic on Carex species
Authors: Salo Vanamo , Sen Robin
Published: April 2011

The smut sori of five Anthracoidea species, A. echinospora, A. heterospora, A. buxbaumii, A. limosa, and A. paniceae, removed from infected inflorescences of 5 Carex host plant species collected from 17 natural Finnish populations, were surveyed by isozyme analysis. The protein extracts of individual sori, containing teliospores (smut spores), together with uninfected utricles, were subjected to polyacrylamide gel electrophoresis and stained for esterase and four peptidase enzymes. Single sori, representing individual infection units, were sufficient to reveal considerable esterase and peptidase isozyme activities, whereas little or no activity was seen in the control utricle extracts. High levels of genetic variation as expressed by the detection of multiple loci and allelism were recorded between species and various populations, but variation within populations was lower. Peptidase banding patterns, in particular, proved to be useful in differentiating species: A. heterospora and A. echinospora, parasitic on the same plant, were clearly distinguished by their isozyme patterns, and the three remaining smuts belonging to the subgenus Proceres could be separated from one another. One morphological character, presence of numerous thick internal swellings in the cell walls of teliospores, seemed to correlate well with banding pattern differences in A. heterospora. Key words: isozymes, electrophoresis, Anthracoidea, Carex, chemotaxonomy.
Serological evidence for the occurrence of races in Sclerospora graminicola and identification of a race-specific surface protein involved in host recognition
Authors: Kumar Vasanthi U. , Shishupala S. , Shetty H. S. , Umesh-Kumar S.
Published: April 2011

A protein specific to a virulent pathotype of the downy mildew pathogen Sclerospora graminicola was identified on the Western transfers using the cross-adsorbed antibody. This protein was approximately 90 kDa and without subunits. Serological agglutination studies localized the protein on the cell wall surfaces. Enzyme linked immunosorbent assay and dot blotting using the specific antibodies identified distinct races of the pathogen. Immunofluorescence studies and enzyme linked immunosorbent assay using suspension cultures of host cells showed that the protein bound to the cells of susceptible cultivar but not to those of resistant cultivar. These results suggested that this protein may be involved in host recognition. Key words: Sclerospora graminicola, Pennisetum glaucum, host–pathogen recognition.
Conidiogenesis in Oidiodendron periconioides and ultrastructure of ericoid mycorrhizas formed with Rhododendron brachycarpum
Authors: Currah R. S. , Tsuneda A. , Murakami S.
Published: April 2011

Oidiodendron periconioides was isolated from hair roots of seedlings of Rhododendron brachycarpum growing in pots containing a commercial peat moss in Japan. The unusual process of conidiogenesis in O. periconioides involved the formation of conidia from vesicle-like swellings that developed from vegetative hyphae or from the apex of a mononematous conidiophore. Scanning electron microscope examinations of mature conidia revealed that they were regularly dimpled, giving them the characteristic and previously reported radiate pattern of sculpturing visible with the light microscope. Oidiodendron periconioides formed ericoid mycorrhizas that were morphologically and ultrastructurally similar to previously studied ericoid systems involving Oidiodendron maius and Hymenoscyphus ericae, and a few other species of Rhododendron. Rough-walled hyphae grew appressed to the epidermal cells of young hair roots, penetrated the external walls via narrow penetration tubes, and invaginated the plasma membrane of the host cell during the process of forming a complex system of hyphal loops. Infection was restricted to the zone proximal to the active region of the meristem. Hyphal complexes were short-lived and degenerated as the epidermal cells matured and died. The physiological role of O. periconioides as a mycorrhizal endophyte is unknown. Key words: ericoid mycorrhiza, Oidiodendron periconioides, Rhododendron brachycarpum, conidiogenesis.
Effect of experimental conditions and genotypic variability on somatic embryogenesis in Coffea arabica
Authors: Bieysse D. , Gofflot A. , Michaux-Ferrière N.
Published: April 2011

The somatic embryogenic potential of leaf explants from greenhouse-grown plants of eight Coffea arabica genotypes was investigated on three different gelose-gelled culture media (Dublin, Pierson, and Yasuda). Four of these genotypes were reactive. Optimal somatic embryogenesis was obtained when the explants were taken from microcutting and cultured on gelrite-gelled Yasuda's medium. Under these culture conditions, somatic embryos and plantlets were obtained in two previously recalcitrant genotypes. The histocytological callus development was found to be identical in responsive or recalcitrant genotypes. Embryogenic cells formed at two successive points during callogenesis and their subsequent development varied according to culture conditions. Cells initiated in 10- to 15-day-old calli either degenerated or developed directly into embryos. Cells initiated in 60-day-old calli became isolated and developed into embryos or their development was arrested. Embryos obtained in these conditions were able to develop into plantlets. Key words: Coffea arabica, genotypic variability, histocytology, in vitro culture, somatic embryogenesis.
Self-compatibility, autonomous self-pollination, and insect-mediated pollination in the clonal species Iris versicolor
Authors: Kron Paul , Stewart Steven C. , Back Allison
Published: April 2011

In clonal species, sexual and asexual systems interact to create a hierarchy of reproduction. For example, self-pollination can occur within pollination units, flowers, ramets, or clones. We investigated the reproductive biology of a natural population of Iris versicolor using pollination manipulations and observations of pollinator behaviour. We found that (i) individuals were completely self-compatible, (ii) selfing rates were close to 100%, (iii) autonomous self-pollination can occur through stigma–anther contact or wind action, (iv) most seed and fruit set can be accounted for by insect pollination, and (v) facilitated self-pollination likely occurs because pollinators frequently visit more than one pollination unit within a flower. Our observations showed that flowers pass through three stages: (i) a male stage (in which pollen is freely available, but stigmas are inaccessible, preventing autogamy); (ii) a female stage (in which stigma flaps have reflexed and are receptive, but pollinators may have already removed most pollen grains, structuring opportunities for geitonogamy); and (iii) a strongly autogamous stage (in which stigma flaps have curled back to contact anthers, leading to delayed autonomous self-pollination). This hierarchy of relatedness among mates determines the genetic consequences of vegetative and sexual reproduction in clonal plants and influences their evolution. Key words: Iris, self-incompatibility, reproductive biology, clonal, pollination.
Germination response to phytochrome depends on specific dormancy states in wild oat (Avena fatua)
Authors: Hou J. Q. , Simpson G. M.
Published: April 2011

Effects of brief red and far-red light on germination of seeds from dormant lines of wild oat (Avena fatua L.) were studied in combination with mechanical injury to the seed coat, application of gibberellin A3, or changes in relative humidity during afterripening. Aberrant germination responses to phytochrome action were observed in the mechanically injured seeds in some of the lines, i.e., brief red light inhibited or delayed germination induced by injury, and immediately following far-red light cancelled the negative effects. Phytochrome action influenced germination of the gibberellin-treated seeds in a normal fashion, although effects of the gibberellic acid and brief red light on germination were not additive. Brief red light inhibited germination of seeds afterripened in zero relative humidity; the same light promoted germination of those in 30 and 60% relative humidity. Germination response to phytochrome in wild oat depends on specific seed dormancy states, illustrated by genetic origins, dormancy-breaking methods and afterripening conditions. Key words: Avena fatua, dormancy, mechanical injury, gibberellin A3, phytochrome, relative humidity.
Pollen morphology of Lagotis (Scrophulariaceae)
Authors: Argue Charles L.
Published: April 2011

The pollen grains of 18 species of Lagotis have been examined using light microscopy and scanning electron microscopy of whole and fractured pollen. The grains are characterized by tricolporate apertures with smooth to sparsely granular ectocolpus membranes; lolongate endoapertures with unthickened margins included within the ectocolpi; relatively large exinous processes over the endoaperture; and columellate, semitectate, reticulate to microreticulate exines with or without supramurial processes. Lumina are reduced in size toward the colpus, but the transition is gradual, and a sharply bounded, differentially sculptured colpus border is absent. Lagotis pollen is distinct from that of the Selagineae and Globularia and indistinct from that of some Veroniceae; however, the characters shared with the latter are of wide occurrence in the Scrophulariaceae. Pollen morphology supports the distinction between L. brachystachya and L. stolonifera. It is consistent with the postulated close relationship between L. micrantha and L. integra, and provides no evidence to support the reestablishment of L. cashmeriana, L. minor, L. pallasii, or L. kunawurensis as species distinct from L. glauca. Key words: pollen morphology, Lagotis, Globularia, Selagineae, Veroniceae.
Cotton (Gossypium hirsutum) seed trichomes expand via diffuse growing mechanism
Authors: Tiwari Suresh C. , Wilkins Thea A.
Published: April 2011

The ultrastructure of cotton (Gossypium hirsutum) seed trichomes was investigated to obtain insight into their growth behavior during the phase of rapid cell elongation. A mold and cast method of scanning electron microscopy was used to record the morphological changes in the ovular surface during the initiation and elongation of trichomes. A rapid freeze-fixation and freeze-substitution protocol was used to study the cytological features of trichomes at 2 days after anthesis. At the cytological level, attention was primarily focused on determining whether the seed trichomes display features that are characteristic of other tip-growing plant cells, including organelle zonation, polarized deposition of cell wall, axial orientation of microtubules, and microfilament meshwork at the cell apex. Our results show that cotton seed trichomes do not share any ultrastructural characteristic with other tip-growing plant cells. Rather, they show all the characteristics of cells that undergo diffuse growth. The roles of actin microfilaments and microtubules were also investigated through an in vitro administration of cytochalasin D and colchicine. Although the disruption of actin filaments did not stop trichome growth, disruption of microtubules did prevent polarized cell expansion. Based on these results, cotton seed trichomes are not tip-growing cells but expand via diffuse growth. Key words: cytoskeleton, freeze-fixation, freeze-substitution, Gossypium hirsutum, lint fibers, tip growth, trichomes.
Do halophytophthoras (marine Pythiaceae) rapidly occupy fallen leaves by intraleaf mycelial growth
Authors: Newell Steven Y. , Fell Jack W.
Published: April 2011

Low estimates (2 ∙ L−1) of concentrations of zoospores of Halophytophthora in mangrove water columns seem counterintuitive when compared with rapid rates of occupation of fallen mangrove leaves (100% frequency of occurrence after 24–30 h). One potential explanation is that lateral extension of mycelium within leaves is rapid after establishment of single zoospores. We tested this hypothesis by exposing single leaves in both mangrove and temperate salt-marsh ecosystems, with the upper half of leaves freely exposed to zoospore contact, and the lower half protected behind 8-μm screening. We found no evidence that mycelial growth within leaves was rapid enough to account for the rapid occupation of freely exposed leaves. Of the four Halophytophthora species commonly found (H. kandeliae, H. masteri, H. spinosa var. spinosa, and H. vesicula), only H. masteri appeared to have substantial capability for its zoospores to pass the screening. In temperate salt-marsh waters, H. kandeliae took the place of H. spinosa as co-occupier of leaves with H. vesicula. Two rare species (H. bahamensis and H. epistomium) originally described from subtropical mangrove environs were found in temperate salt-marsh samples. Key words: oomycotes, oomycetes, Halophytophthora, mangrove, salt marsh.
Metal tolerance inAgrostis scabrafrom the Sudbury, Ontario, area
Authors: Archambault Daniel J. , Winterhalder Keith
Published: April 2011

Acid, metal-contaminated soils are frequently colonized by plant species that have evolved tolerance to metals. Agrostis scabra (tickle grass) grows at several such sites in the Sudbury area. To test whether these populations were tolerant to metals, three experiments were performed. A hydroponic root growth experiment, in which clonal ramets from contaminated and uncontaminated sites were grown in metal-amended nutrient solutions, showed that plants from the Sudbury area had greater tolerance indices than those from outside Sudbury. A seed-based hydroponic experiment, where seeds were germinated in metal solutions, showed that metal-tolerance indices calculated from root growth were mostly greater for populations from Sudbury but that leaf growth was not a good indicator of metal tolerance. A seed-based soil-bioassay experiment, in which seeds were germinated on soils covered with filter paper, showed that seeds from contaminated sites performed better on contaminated soil and a 50:50 soil mixture (contaminated–uncontaminated) than those from uncontaminated sites. Populations of A. scabra growing on contaminated soils in the Sudbury area therefore appear to have been selected for metal tolerance. Ecological aspects of metal tolerance and the possible role of A. scabra in the revegetation of the Sudbury area are discussed. Key words: Agrostis scabra, tolerance, metals, acid soil, contamination.