bluuebunny/crossref_metadata_2025 huggingface dataset:
Competition among Sclerotinia sclerotiorum genotypes within canola stems
Authors: Maltby A. D. , Mihail J. D.
Published: April 2011

Populations of Sclerotinia sclerotiorum are often composed of multiple genotypes. In examining 35 naturally infected canola plants, 29 supported reproduction (i.e., sclerotium formation) by a single S. sclerotiorum genotype, as defined by the mycelial compatibility test. Only six plants supported reproduction by two genotypes. To test the hypothesis that infrequent multiple genotype infections were due to differences in virulence or competitive ability among isolates, four greenhouse experiments were conducted in which four isolates, representing three genotypes, were used in pairwise coinoculations of canola. There were no differences among the isolates in four virulence parameters. Mean reduction in sclerotial mass produced by a coinoculated isolate was calculated by comparison with the mean sclerotial mass of that isolate in the absence of competition, and used as the measure of competition. In all experiments, at least half of the coinoculation treatments resulted in reduced fungal reproduction for one or both of the coinoculated isolates, providing evidence of competitive differences. Generally, the magnitude of reproduction reduction was the same for each isolate in the pair. However, the magnitude was nonreciprocal when the more competitive isolate was given an advantage of early temporal arrival or spatial placement of inoculum at the lower position on the stem. Competitive differences among S. sclerotiorum isolates affecting reproduction represent one possible mechanism to explain temporal shifts in genotype frequencies. Key words: canola, competition, population structure, Sclerotinia sclerotiorum, virulence.
Variation in pollen wall ultrastructure in New World Senecioneae (Asteraceae), with special reference to Packera
Authors: Bain J. F. , Tyson B. S. , Bray D. F.
Published: April 2011

The structure of the pollen wall as revealed by transmission electron microscopy is presented for 34 species representing two subtribes and 12 genera of New World Senecioneae. The genus Packera (=aureoid Senecio), with the exception of Packera zimapanica, is characterized by the helianthoid wall structure. In light of these results, the disposition of the latter species requires review. The genera Robinsonecio and Telanthophora of the subtribe Tussilagininae also possess helianthoid pollen. All other taxa surveyed have senecioid pollen. So far as known no taxa exist within the tribe Senecioneae with a base chromosome number of n = 20 and helianthoid pollen. This suggests that the evolution of Packera may have involved hybridization between members of the two subtribes Senecionineae and Tussilagininae. Key words: Asteraceae, Packera, Senecioneae, pollen, TEM, systematics.
Peroxidase and laccase activities in mycorrhizal and non-mycorrhizal fine roots of Norway spruce (Picea abies) and larch (Larix decidua)
Authors: Münzenberger B. , Otter T. , Polle A. , Wüstrich D.
Published: April 2011

Peroxidase (EC 1.11.1.7) and laccase (EC 1.10.3.1) activities were determined in mycorrhizal and non-mycorrhizal main and lateral roots of Picea abies (L.) Karst. (Norway spruce) and Larix decidua Mill, (larch) and in mycelia of the ectomycorrhizal fungus Laccaria amethystea (Bull.) Murr. grown under axenic conditions. Peroxidase isozyme patterns were identified after isoelectric focussing. In both tree species, mycorrhizae contained the lowest, and laterals of noninoculated plants the highest, peroxidase activities. Pure mycelia of Laccaria amethystea contained considerable laccase activity but no peroxidase activity. Laccase activity was barely detected in noninoculated laterals of spruce, but was present in noninoculated laterals of larch and in main roots of Norway spruce and larch. Highest laccase activities were found in mycorrhizae of both tree species, indicating that most of the activity was derived from the fungus. Laterals of Norway spruce contained eight, and those of larch five, acidic peroxidase isozymes. In mycorrhizae of Norway spruce and larch, specific peroxidase isozymes with pI values of 4.5 and 6.2 and 5.8 and 6.0, respectively, were almost completely suppressed. The specific suppression of peroxidase suggests that the fungal symbiont is able to modify the host defence response in mature mycorrhizae. Key words: defence mechanism, laccase, mycorrhiza, peroxidase (isozymes), plant–fungus interaction.
Floral color change in Errazurizia megacarpa, a sonoran desert shrub
Authors: Kelt Douglas A.
Published: April 2011

Flowers of many species undergo partial or complete color changes in the course of their development. These changes are thought to cue pollinators to receptive flowers. In the Lower Sonoran Desert of northern Mexico, individuals of the long-lived perennial shrub, Errazurizia megacarpa (S. Watts) I.M. Johnston 1924 (Leguminosae), produce many hundreds of racemose inflorescences in which the terminal, younger flowers have yellow corollas, while lower, older flowers have red ones. I studied the response of visitor species to the floral display of E. megacarpa by direct observation of visitor activity and by manipulating the floral display to remove yellow or red flowers. Equal-sized plants with similar sized floral displays containing only red flowers, only yellow flowers, and control plants with both red and yellow flowers, attract roughly equal numbers of putative pollinating insects. However, once pollinators have approached a plant, they discriminate against red flowers, visiting these extremely rarely. Floral color change in this species provides a cue to direct pollinator activity to receptive and rewarding flowers. Key words: floral color change, pollinator cues, reproductive ecology.
Environmental parameters influencing the distribution of Platanthera blephariglottis and Platanthera clavellata (Orchidaceae) in peatlands on the Avalon Peninsula, Newfoundland
Authors: Brown C. J. , Scott P. J.
Published: April 2011

Populations of two terrestrial species of orchids, Platanthera blephariglottis (Willd.) Lindl. and Platanthera clavellata (Michx.) Luer, were investigated for two field seasons (1991-1992) to determine what environmental factors (substrate constituents, water pH, water level) may influence their distributions within a peatland. Peat constituent values (magnesium, phosphorus, nitrogen, potassium, iron, calcium, pH, moisture, organic matter, ash) associated with individual species were, for the most part, not significantly different among sites or between species, although the values associated with P. clavellata tended to be higher and to have a greater range than those associated with P. blephariglottis. Water level values associated with species were significantly different between species, suggesting mat it is on this basis that these species partition their habitat. Key words: water level, environmental parameters, distribution, peatland, Platanthera blephariglottis, Platanthera clavellata.
Measurement of the amount and isotopic composition of the CO2released from the cyanobacteriumSynechococcusUTEX 625 after rapid quenching of the active CO2transport system
Authors: Miller Anthony G. , Salon Christophe , Canvin David T. , Espie George S.
Published: April 2011

Air-grown cells of the cyanobacterium Synechococcus UTEX 625 were suspended in a cuvette connected to a mass spectrometer and supplied with H13C18O3−to investigate the intracellular interconversion between CO2and HCO3−as determined from the isotopic composition of CO2appearing in the extracellular medium under a wide variety of experimental conditions. Upon injection of H13C18O3−to the cell suspension in the light, the extracellular [13C16O2] increased. As the CO2species were13C labelled, this demonstrated that the18O-depleted CO2was originating from the added H13C18O3−. A comparison of the rates of13C16O16O appearance in the medium with the formation of13C16O16O from spontaneous dehydration–hydration in the extracellular medium in the presence of cells demonstrated that most of it had to originate from a series of intracellular dehydration–hydration cycles of H13C18O3−that had been recently transported into the cells. During the time course of the experiments both the m/z (mass to charge) = 49 (i.e.,13C18O18O) and 47 (i.e.,13C18O16O) signals decreased constantly, whereas the m/z = 45 signal (i.e.,13C16O2) always increased. Inhibiting CO2fixation enhanced the amount of CO2arising in the medium but did not change its isotopic composition, and the CO2was always fully depleted of18O. When the CO2transport system was inhibited by darkening the cells, adding inhibitors such as Na2S or COS, or quenching the uptake of inorganic13C with an excess of inorganic12C, the magnitude of the extracellular [13C16O2] was increased but the CO2species were still always depleted of18O. Various incubation times of the illuminated cells in the presence of H13C18O3−were used to obtain a variety of internal Cipool sizes. When the inhibitor (COS) was added, the amount of13C16O2arising during the response time of the mass spectrometer was equivalent to the amount of CO2that would have been present in the whole cell if CO2and HCO3−were in equilibrium throughout the entire cell volume, but it was at least 40 times higher than the amount of CO2that would have been present in the cell if the CO2was confined to the carboxysomes. Experiments were also conducted at pH 9.0 where the spontaneous rate of13C16O2production from H13C1803−dehydration–hydration would be negligible, and again the same features were observed. Results show that intracellular HCO3−and CO2are in rapid equilibrium throughout the entire cell volume. Key words: Synechococcus UTEX 625, cyanobacteria, CO2leakage,18O exchange, active CO2transport, carboxysomes, inorganic C concentrating mechanism.
Parasitism of algae by lignicolous Basidiomycota and other fungi
Authors: Hutchison Leonard J. , Barron G. L.
Published: April 2011

On water agar, 30 out of 81 species of fungi tested showed positive directional hyphal growth towards microcolonies of the green alga Protococcus sp. and produced coralloid masses of branched assimilative hyphae within the invaded algal colonies. Of 77 species of fungi tested against the blue-green alga Synechococcus elongatus, 33 exhibited this same phenomenon. Cell walls of S. elongatus were subsequently lysed while only cell death occurred in Protococcus sp., resulting in the release of the contents that were presumably absorbed by the coralloid hyphae. Branched hyphae from some invading fungi occasionally attached to larger individual cells of Protococcus sp., penetrated the walls, and absorbed the contents. Key words: algae, Chlorophyta, Cyanophyta, cyanobacteria, Basidiomycota, wood decay, nitrogen requirements, Protococcus, Synechococcus.
The natural history of western skunk cabbage (Lysichiton americanum) in southeast Alaska
Authors: Willson Mary F. , Hennon Paul E.
Published: April 2011

Western skunk cabbage is protogynous, with great seasonal variation in floral sex ratios. It is pollinated chiefly by a small staphylinid beetle (Pelecomalius testaceum), which was found most abundantly on male-phase inflorescences in southeast Alaska. Yellow spathes attracted more beetles than green ones, especially on male inflorescences. The gelatinous coat around the seed impeded local dispersal, slowed germination slightly, had no detectable effect on seed predation, and had a possible deterrent effect on a pathogenic fungus. Key words: Lysichiton americanum, western skunk cabbage, Araceae, Pelecomalius testaceum, southeast Alaska, pollination.
Cupric oxide oxidation products of northern peat and peat-forming plants
Authors: Williams Christopher J , Yavitt Joseph B , Wieder R Kelman , Cleavitt Natalie L
Published: April 2011

Alkaline cupric oxide oxidation and proximate analysis were used to investigate the sources and diagenetic state of organic matter in six Sphagnum-dominated peatlands located between Alberta, Canada, and Ohio, U.S.A. Cupric oxide oxidation was also used to characterize vascular and nonvascular wetland plant species to provide a specific biological fingerprint of these plant tissues. Oxidation of 15 species of Sphagnum moss released large quantities of unsubstituted p-hydroxyl phenolic compounds as well as the species specific sphagnum acid (p-hydroxy-β-[carboxymethyl]-cinnamic acid). By contrast, vascular plant tissues released large amounts of lignin oxidation products. Cupric oxide oxidation of Sphagnum peat from more northerly sites produced mainly p-hydroxyl phenolic monomers with lesser amounts of vascular lignin derived phenols. In contrast, southern sites and those dominated by woody vegetation produced oxidation products characteristic of vascular plant lignin. A distinct relationship exists between the amount of acid-insoluble Klason lignin and both the diagenetically sensitive phenolic acid to aldehyde ratios as well as the total yield of vanillyl phenolic oxidation products. We found evidence of selective decay of phenolic lignin precursors. These relationships indicate the lignin component in surficial layers of Sphagnum-dominated peat is influenced by both Sphagnum and vascular plant lignin, and the structure of lignin appears to undergo diagenetic changes in these layers. Application of an end-member mixing model revealed that lignin oxidation products poorly predicted vegetational composition of the lignin in more decomposed peat, probably as a result of selective decay of lignin structural phenols. Key words: lignin, organic soil, proximate analysis, Sphagnum moss, wetland.
Isolate-by-cultivar interaction in root-knot nematodes Meloidogyne hapla, M. chitwoodi, and M. fallax on potato
Authors: Van der Beek J G , Vereijken PFG , Poleij L M , Van Silfhout C H
Published: April 2011

To study virulence and aggressiveness in root-knot nematodes on cultivars of potato (Solanum tuberosum L., four isolates of Meloidogyne hapla Chitwood race A, one of M. hapla race B, three of Meloidogyne chitwoodi Golden et al., and two of Meloidogyne fallax Karssen were evaluated on 10 commercial potato cultivars under semisterile conditions in Petri dishes. Virulence and aggressiveness were assessed in terms of nematode reproduction by egg-mass index and reproduction factor, estimated by the number of egg masses and juveniles produced, respectively, divided by the number of juveniles inoculated. Significant interaction for both parameters was revealed between species of Meloidogyne and potato cultivars. Only M. hapla showed significant isolate-by-cultivar interaction, which was predominantly caused by the M. hapla race B isolate Hh. This indicates variation in virulence and suggests the occurrence of different genetic factors for virulence and resistance in M. hapla isolates and potato cultivars, respectively. Despite large differences, the observed levels of resistance were too low to be of practical meaning for breeding, with the exception of resistance to isolate Hh. No significant differences were obtained between isolates of M. chitwoodi and M. fallax or isolate-by-cultivar interaction, indicating neither variation in aggressiveness nor in virulence in the isolates used. A comparative greenhouse experiment gave comparable results for egg-mass index but contradicting results for reproduction factor, most likely because of differences in life cycle, which appeared to be shorter in M. fallax than in M. hapla and M. chitwoodi. The Petri-dish method proved to be accurate for virulence studies of root-knot nematodes on potato culitvars. Meloidogyne fallax was most aggressive on potato, followed by M. chitwoodi, M. hapla race A, and finally by M. hapla race B. Key words: aggressiveness, biadditive model, biplot, plant breeding, resistance, virulence.
Ecological causes, function, and evolution of abortion and parthenocarpy inPistacia lentiscus(Anacardiaceae)
Authors: Verdú Miguel , García-Fayos Patricio
Published: April 2011

Parthenocarpy (the production of seedless fruits) and abortion of reproductive structures at different developmental stages are important processes limiting female fecundity in Pistacia lentiscus (Anacardiaceae), a Mediterranean endozoochorous dioecious shrub. This paper tests (i) the effects of water and pollen as the ecological causes of abortion and parthenocarpy, (ii) the function of abortion and parthenocarpy regarding the uncertainty on resources and predispersal seed predation, and (iii) reviews the evolution of parthenocarpy across the phylogeny of the genusPistacia and the family Anacardiaceae. Using experimental manipulations, we examined the effects of pollen and water availability on female fecundity. The components of female fecundity were the four sequential developmental stages in the reproductive cycle: (i) flower survival after pollination, (ii) latent ovary survival, (iii) final-sized fruit survival, and (iv) seed viability. The survival of reproductive structures along the four developmental stages in response to pollination was highly variable. The survival of pollen-excluded flowers was negligible. Water addition increased the survival of reproductive structures in the first two developmental stages but this effect was lost in the other two stages. However, irrigation had a delayed effect, significantly increasing the number of viable seeds per number of flowers at the following reproductive season. The irrigated females significantly increased the percentage of viable seeds, whereas nonirrigated females did not. These data support the hypothesis that the adjustment of progeny size to the available resources is an individual feature inherent to the life history of each individual and therefore independent on the present resource level. This adjustment may have an adaptive value in relation to uncertainty of water availability. An advantage for parthenocarpy in terms of reducing seed predation was not found and it may be a nonadaptive plesiomorphic character within the genus Pistacia and within the family Anacardiaceae. A significant negative relationship was found between the rate of seed abortion and predispersal seed predation by wasps, suggesting that abortion reduces insect predation. In support of this hypothesis, we found that fruits with aborted seeds abscised in a lower proportion than expected, while fruits with seeds parasitized by wasps fell in a greater proportion than expected. Key words: abortion, parthenocarpy, predispersal seed predation, seed production.
Water relations in Azospirillum-inoculated wheat seedlings under osmotic stress
Authors: Creus Cecilia M , Sueldo Rolando J , Barassi Carlos A
Published: April 2011

Azospirillum has been shown to improve coleoptile growth in seedlings growing in darkness under osmotic stress. However, the changes in water relations that may occur in this experimental system have not yet been studied. Two-centimetre long Triticum aestivum cv. Buck Pucará and Triticum durum cv. Balcarceño-INTA seedlings were inoculated with viable or autoclaved (control) Azospirillum brasilense Sp. 245 bacteria, at approximately 108 cells per seedling. Three days after inoculation, seedlings were exposed to osmotic stress by immersing their roots in 20% polyethylene glycol 6000 for up to 72 h. Germination and seedling growth were at 20°C in darkness. Shoots were excised after 72 h of stress, and water-status parameters were determined through pressure-volume analyses. While osmotic potential at full turgor remained constant, Azospirillum-stimulated growth in Buck Pucará seedlings was accompanied by significant decreases in osmotic potential and relative water content at zero turgor, in volumetric cell wall modulus of elasticity, and in absolute symplastic water volume and by a significant rise in apoplastic water fraction parameters. Except for a constant volumetric cell wall modulus of elasticity, similar results were obtained with Balcarceño-INTA seedlings. However, bacterial growth promotion was evident only in the less tolerant cv. Buck Pucará. Turgor at low water potential was higher in inoculated seedlings in both wheat cultivars under osmotic stress. These results are consistent with a better water status in Azospirillum-inoculated wheat seedlings under water stress, where both effects on cell wall elasticity and (or) apoplastic water are evident.Key words: Azospirillum, drought, seedlings, water status, wheat.
Relationships of wildBrassicaspecies with chromosome number 2n= 18, based on comparison of the DNA sequence of the chloroplast intergenic region betweentrnL(UAA) andtrnF(GAA)
Authors: Lannér Carita
Published: April 2011

A specific chloroplast DNA sequence was compared in 34 populations representing 10 wildBrassica species (2n = 18). Species studied were Brassica bourgeaui (Webb) O. Kuntze, Brassica cretica Lam., Brassica hilarionis G.E. Post, Brassica incana Ten., Brassica insularis Moris, Brassica macrocarpa Guss., Brassica montana Pourret, Brassica oleracea L., Brassica rupestris Raf., and Brassica villosa Biv. The sequence was located between the trnL and trnF genes in the large, single-copy region of the chloroplast genome. Site-specific primers were used to amplify the region via the polymerase chain reaction technique. Products of the same size were amplified from all populations. Sequence differences in the DNA fragments were detected by denaturing gradient gel electrophoresis. Ten different haplotypes defined by 20-base sequence differences were detected. Haplotype did not always reflect species classification. Haplotypes were shared by the species pairs B. rupestris - B. villosa, B. cretica - B. incana, and B. bourgeaui - B. oleracea. Populations carrying divergent haplotypes were discovered for B. cretica, B. montana, and B. insularis. Possible introgression of the B. macrocarpa cytoplasm into a B. insularis population was observed. DNA sequences for the 10 haplotypes were determined and subjected to phylogenetic analysis using maximum parsimony. In the phylogenetic tree, the B. rupestris - B. villosa haplotype formed a basal clade, the B. macrocarpa haplotype diverged next, while all other species fell into a third clade.Key words: wild Brassica species, B. oleracea cytodeme, haplotype, cpDNA, phylogeny.
A morphometric evaluation of the subspecies ofFragaria chiloensis
Authors: Catling Paul M , Porebski Sue
Published: April 2011

To evaluate the relationship between the four subspecies of Fragaria chiloensis, 14 characters were measured in 95 plants. F ratios from ANOVA were used to determine and apply the optimal characters for subspecies separation. Discriminant analysis indicated that the Hawaiian ssp. sandwicensis was entirely distinct, differing from the other subspecies in having longer leaflets and longer hairs on the undersurface of the leaflets and more numerous leaflet veins. The South American and North American plants were significantly different but overlapped to a degree. The former differed primarily by having mostly 6-10 petals, instead of having 5-6 (rarely 7) petals. The two North American subspecies overlapped extensively and may be best transferred to a lower taxonomic rank. A key to the subspecies is included.Key words: Fragaria chiloensis, ssp. pacifica, ssp. lucida, ssp.sandwicensis, ssp. chiloensis, Rosaceae, strawberry, taxonomy, classification, morphology, North America, South America, Hawaii.
Allelopathic potential of Artemisia campestris ssp. caudata on Lake Huron sand dunes
Authors: Yun Kyeong W. , Maun M. A.
Published: April 2011

Greenhouse studies were conducted to test allelopathic effects of Artemisia campestris ssp. caudata on seed germination and seedling growth of several sand-dune species and colonization by mycorrhizal fungi. The aqueous extracts of A. campestris showed no inhibitory effect on seed germination, seedling elongation, or dry-weight growth of plants at lower concentrations (10 and 50%), but 100% concentration of the extracts caused varying degrees of inhibition depending on the test species. The mixing of dry leaves of seedlings of A. campestris to the sand showed severe inhibition of Elymus canadensis seedlings. The percent germination of test species in soil from the rhizosphere of A. campestris was significantly lower than that of the control. The leaf area and dry weight were also lower but the differences were not significant. The aqueous extract inhibited mycorrhizal fungal colonization in roots of three sand-dune grasses. Key words: allelopathy, Artemisia campestris ssp. caudata, seed germination, seedling growth, mycorrhizal fungi.
Influx and efflux of inorganic carbon during steady-state photosynthesis of air-grownAnabaena variabilis
Authors: McGinn Patrick J. , Canvin David T. , Coleman John R.
Published: April 2011

The inward and outward fluxes of inorganic carbon in illuminated cell suspensions of air-grown Anabaena variabilis were measured by mass spectrometry under conditions of inorganic carbon disequilibrium. The inclusion of 25 mM NaCl significantly enhanced both inward inorganic carbon influx during CO2fixation and outward CO2efflux when CO2fixation was blocked by the Calvin cycle inhibitor, iodoacetamide. At low, steady-state concentrations of inorganic carbon (< 100μM), CO2fixation was nearly entirely supported by HCO3−transport in the presence of 25 mM NaCl. At approximately 150 μM inorganic carbon, the contributions of CO2and HCO3−transport to CO2fixation were about equal. Above this, CO2transport provided most of the substrate for CO2fixation. The affinity (K0.5) of photosynthesizing cells for CO2, HCO3−and total inorganic carbon was determined and mean values of 1.7, 9.5, and 8.2 μM, respectively, were determined. Maximum rates of inward CO2and HCO3−transport and CO2fixation during steady state were 255.7, 307.3, and 329.1 μmol∙mg−1Chl∙h−1, respectively. Permeability coefficients for CO2of 9.8 × 10−8 m∙s−1and 2.8 × 10−7 m∙s−1were calculated for the plasma membrane and carboxysomal surface areas, respectively, from the dark efflux rates assuming an internal pH of 7.2. A permeability coefficient for HCO3−across the plasma membrane of 7.6 × 10−9 m∙s−1was calculated from the dark inorganic carbon efflux corrected for the corresponding dark CO2efflux. Sodium sulphide (Na2S, 200 μM) blocked CO2transport. In the presence of 25 mM NaCl, net CO2efflux was approximately seven times greater than in its absence, when CO2transport and fixation were both blocked, indicating greater CO2leakage as a result of larger internal inorganic carbon pools in the presence of NaCl. The rapidity and amount of C16O2generated from the exchange of18O from18O-enriched HCO3−with water in cell suspensions suggested that the internal inorganic carbon pool may be rapidly equilibrated. Key words: Anabaena variabilis, CO2-concentrating mechanism, CO2transport, HCO3−transport, CO2efflux, permeability coefficient.
Haidadinium ichthyophilumgen.nov. et sp.nov. (Phytodiniales, Dinophyceae), a freshwater ectoparasite on stickleback (Gastetosteus aculeatus) from the Queen Charlotte Islands, Canada
Authors: Buckland-Nicks J. , Garbary D. J. , Reimchen T. E.
Published: April 2011

The dinoflagellate Haidadinium ichthyophilum gen.nov. et sp.nov. is associated with the threespine stickleback, Gasterosteus aculeatus L., in freshwater. This new genus differs from all previously described dinoflagellates in the morphology and ultrastructure of its complex life history stages and in the ecology of its interaction with G. aculeatus. Distinguishing characters included (i) the absence of thecal plates and the occurrence of chloroplastes in the short-lived swarmer (=dinospore) stage; (ii) the development of four distinct amoeboid stages including a spheroidal, rolling amoeba unknown in any other species; and (iii) the fact that this dinoflagellate causes epithelial hyperplasia in the stickleback and does not result in massive fish kills. Haidadinium ichthyophilum is known only from two acidic lakes in the Queen Charlotte Islands, British Columbia, Canada. Haidadinium is tentatively assigned to the family Phytodiniaceae of the order Phytodiniales. Key words: dinoflagellates, Dinophyceae, Gasterosteus, Haidadinium ichthyophilum gen.nov. et sp.nov., Queen Charlotte Islands, Phytodiniales, symbiosis, taxonomy, ultrastructure.
The floral development ofMonococcus echinophorus(Phytolaccaceae)
Authors: Vanvinckenroye P. F. , Decraene L. P. Ronse , Smets E. F.
Published: April 2011

The floral ontogeny of the monotypic genus Monococcus (Phytolaccaceae) is investigated with the scanning electron microscope. Flowers arise on pendent racemes and are preceded by a bract and two bracteoles arising successively. In both staminate and pistillate flowers four sepals are incepted in diagonal position. In the staminate flowers four alternisepalous stamens are initiated successively. Further stamen inception occurs centrifugally and runs concomitant with peripheral growth of the receptacle. This centrifugal stamen initiation is interpreted phylogenetically as a secondary increase and is expressed by the appearance of four triplets. Initiation of a variable number of outermost stamens (0–8) occurs mostly in the latero-abaxial region of the flower. In staminate flowers there is no trace of a gynoecium. In pistillate flowers a gynoecium primordium arises centrally and grows into a monocarpellate structure. Later, hooked bristles arise on the carpel flanks while a short style is produced bearing a distal tangle of long hairs. A close relationship of Monococcus with Petiveria is confirmed; similarities include the median position of the prophylls, the diagonal position of four sepals, the sequential inception of four alternisepalous stamens, and the fruits with adaptations for exozoochory. Key words: androecium, floral ontogeny, Monococcus, Phytolaccaceae, Rivinoideae.
Pyramimonas robusta sp.nov., a new punctate species, and a reappraisal of the subgenus Punctatae
Authors: Pienaar R. N. , Sym S. D.
Published: April 2011

The ultrastructure of a new punctate species, Pyramimonas robusta, is described and, by comparison with features of Pyramimonas olivacea N. Carter and Pyramimonas mucifera Sym et Pienaar, has allowed for a more defined delimitation to the subgenus Punctatae McFadden. Features, in addition to the obvious character of puncta, which are considered characteristic of this subgenus, include a benthic nature, a chloroplast with a ventral groove coincident with the left and right sinuses, box scales with spines on their side walls, crown scales with eccentric crosses on their base plates, segmented T hairs, limuloid scales with three subsidiary spines and five subsidiary radial ribs, a 3-1 type flagellar apparatus, a basal body with a long region of triplets with longitudinal fibrils separating proximal and distal cartwheel structures, and a 3(2/1):4 or 3:3(2/1):2 microtubular root system. Although as a suite these are characteristic, a great deal of the individual features are shared with other subgenera, specifically subgroup 2 members of the subgenus Trichocystis McFadden but especially members of the subgenus Pyramimonas McFadden. Features originally considered diagnostic that now are questionable include pyrenoid structure and starch investiture and the bilayered nature of the eyespot. Key words: Punctatae, Pyramimonas, Pyramimonas robusta sp. nov., ultrastructure.
Effects of disturbance by sand movement and inundation by water on tropical dune vegetation dynamics
Authors: Martinez M. Luisa , Moreno-Casasola Patricia , Vázquez Gabriela
Published: April 2011

Sand movement and slack inundation by water act as disturbance agents in dune systems. In this study we focus on these disturbance agents with different intensity and frequency that affect differentially the structure and composition of dune vegetation. Sand movement and slack inundation by water were monitored during 1979 – 1981 and 1991 – 1995. Sand movement reached higher values during the dry months, which coincided with the occurrence of yearly strong northerly winds. Sand movement has decreased over the last 10 years due to an increment in plant cover, particularly Chamaecrista chamaecristoides and Schizachyrium scoparium. Slack inundation was also a common phenomenon at the study site, but its frequency was much less predictable. Pluchea odorata, Panicum maximum, and Schizachyrium scoparium were the first species to recolonize the area after intense inundation. In the absence of inundated periods, slack vegetation increased its species richness and showed a more complex structure with higher shrub and tree cover. Markovian models showed a stable state in which species richness increased. Our study showed that the mosaic pattern of dunes is the result of two types of heterogeneity: spatial heterogeneity due to dune topography, and the asynchronous occurrence of two disturbance regimes that modify succession in a patchy fashion. Key words: tropical dunes, disturbance, heterogeneity, sand movement, inundation, succession.
The effect of fire on red heather (Phyllodoce empetriformis)
Authors: Potash Laura L , Agee James K
Published: April 2011

Red heather (Phyllodoce empetriformis (Sw.) D. Don) recovery after experimental fires and wildfires was studied at five subalpine sites in Washington State, U.S.A. Experimental burn treatments showed that fire had a neutral to positive effect on stem numbers but generally a short-term negative effect on aboveground biomass production. Although there were no differences in effects between experimental burn and clip treatments, long-duration smoldering beyond that documented in our experiments may have more damaging effects. On three wildfire sites, sprouting was vigorous after fire except at one site adjacent to forest cover where significant litter consumption occurred. The duration of fire, rather than its presence or absence, may be an important character of the fire regime in predicting post-fire response of red heather.Key words: red heather, Phyllodoce empetriformis, fire, subalpine meadows, Pacific Northwest.
Tamsiniella labiosa gen. et sp.nov., a new freshwater ascomycete from submerged wood
Authors: Wong Sze-Wing , Hyde Kevin D , Ho Wai-Hong , Stanley Susan J
Published: April 2011

Investigations into the fungi occurring on wood submerged in freshwater ecosystems have revealed a unique, but characteristic group of fungi. In this paper a new pyrenomycete, Tamsiniella labiosa gen. et sp.nov., is described and illustrated with light, scanning, and transmission electron micrographs. The genus has remarkable short stipitate cylindrical asci with an internal refractive apical ring that are apically truncate and have an external thickening. Ascospores are ellipsoidal-fusiform and surrounded by a mucilaginous sheath. At the transmission electron microscope level, the annulus part of the ascus apical apparatus is differentiated from the inner ascus wall layer and is composed of horizontally oriented, electron-dense fibrillar material. A narrow plug is present in the centre of the apical ring. An electron-dense amorphous region occurs between the outer ascus wall layer and the annulus part of the apical apparatus. The outer ascus wall layer is lacking at the apex. The ultrastructure of the ascus apex differs from those described in the Lasiosphaeriaceae, Sordariaceae, and Xylariaceae.Key words: aquatic fungi, Myelosperma, new genus, transmission electron microscope.
Cytotaxonomic studies in Brazilian Rhynchospora (Cyperaceae), a genus exhibiting holocentric chromosomes
Authors: Luceño Modesto , Vanzela André LL , Guerra Marcelo
Published: April 2011

The genus Rhynchospora (Cyperaceae) is a widely distributed Brazilian group, with approximately 150 species. We have studied mitosis and (or) meiosis of 16 species of four sections (Dichromena, Longirostres, Polycephalae, and Pluriflorae). The results showed high frequencies of chromosome number multiples of x = 5, which is the probable basic number. Polyploidy, in contrast to agmatoploidy and (or) symploidy, seems to be the predominant cytogenetic mechanism in the evolution of the karyotype. Primary constrictions were not visible in the chromosomes, suggesting a holocentric condition, as observed in other genera of this family. Karyotype interspecific differences were useful in the cytotaxonomic analysis in three sections. Our data propose (i) the separation of Rhynchospora ciliata (Vahl.) Kükenth. from Rhynchospora nervosa (Vahl.) Böckeler (section Dichromena), (ii) the inclusion of Rhynchospora legrandii Kükenth. ex Barros as a subspecies of Rhynchospora corymbosa (L.) Britton (section Longirostres), and (iii) a suggestion for the organization of section Pluriflorae.Key words: Rhynchospora, Cyperaceae, holocentric chromosomes, polyploidy.
Effect of temperature during sclerotial formation, sclerotial dryness, and relative humidity on myceliogenic germination of sclerotia of Sclerotinia sclerotiorum
Authors: Huang H C , Chang C , Kozub G C
Published: April 2011

A study was conducted to determine the effect of sclerotial dryness, temperature during sclerotia formation, and relative humiditiy during incubation on myceliogenic germination of sclerotia of two isolates of Sclerotinia sclerotiorum (Lib.) De Bary. In the absence of exogenous nutrients, sclerotia germinated more readily at 100% RH than at 95% RH or lower. Desiccation of sclerotia is an important factor affecting myceliogenic germination and hyphal growth. At high humidity, either in an atmosphere with 100% RH or on moist sand, desiccant-dried sclerotia germinated readily and produced vigorous hyphal growth that often developed into colonies. On the other hand, fresh, untreated sclerotia germinated less readily and produced limited growth of hyphae that rarely developed into colonies. There was generally no effect of temperature at which sclerotia formed on germination. The incidence of seed rot and seedling wilt of sunflower was significantly (p < 0.05) higher when desiccant-dried sclerotia were used as inoculum rather than fresh sclerotia.Key words: Sclerotinia sclerotionum, sclerotia, myceliogenic germination, sclerotinia wilt of sunflower, relative humidity.
First intergeneric hybrids (Psilanthus ebracteolatus Hiern x Coffea arabica L.) in coffee trees
Authors: Couturon E , Lashermes P , Charrier A
Published: April 2011

Intergeneric hybrids between Psilanthus ebracteolatus (2n = 22) and Coffea arabica (2n = 44) were successfully produced by crossing at the tetraploid level. Although a total of 41 plants was obtained, only nine plants survived after 5 months growth in the nursery. Hybrid status was confirmed by means of cytological and molecular methods. For most of the morphological characteristics analyzed, hybrids appeared intermediate between the two parental species. The mean production of two surviving hybrids per 100 pollinated flowers as well as their fertility are comparable with those reported for intrageneric crosses between subgenera Coffea species, and do not support the present division of coffee trees into two genera. Both the capacity of C. arabica to hybridize with P. ebracteolatus and the fertility of hybrids produced appear high enough to envisage intergeneric gene transfers from P. ebracteolatus into C. arabica.Key words: coffee, fertility, hybridization, intergeneric, polyploid, wide cross.
Cotyledon-derived diploid and haploid protoplast culture and diploid plant regeneration in Brassica napus cv. ' Topas '
Authors: Sun M , Kieft H , van Lammeren AAM
Published: April 2011

The present paper describes a simple and reliable protocol for the successful isolation, purification, culture, and regeneration of diploid cotyledon-derived protoplasts of Brassica napus L. cv. 'Topas'. Various protoplast isolation media, nutrient media, subculture procedures, and protoplast sources were tested under two culture temperatures. Protoplast viability, cell wall regeneration, and cell division were monitored. Single cotyledon-derived protoplasts formed calli in liquid protoplast medium, and when these were subcultured on solid proliferation medium and solid regeneration medium of appropriate composition, plants regenerated either by shoot formation or embryogenesis. Continuous culture at 32°C instead of 25°C favoured the initiation of cell division and cell proliferation but prevented regeneration, although calli maintained regeneration capacity. Viable haploid protoplasts were isolated from cotyledons of heat-shock-induced, microspore-derived haploid embryos and from young leaves of secondary embryos that were formed on microspore-derived embryos. Cell divisions were triggered in the two types of haploid protoplast cultures, and microcalli were formed at high frequencies. Differences between haploid and diploid protoplast cultures are discussed.Key words: cotyledon protoplast culture, haploid culture, plant regeneration.
Intraspecific variability in the response to light quality in Crotalaria incana and Impatiens sultanii
Authors: Wulff Renata
Published: April 2011

To study some aspects of intraspecific variability, half-sib families of Crotalaria incana L. and Impatiens sultanii Hook. f. were grown in the field exposed to reflected light of either high or low red to far-red ratio, without direct shading. Plants of both species responded to the light quality of the reflected light. Crotalaria plants were more responsive; a reduction in the red to far-red ratio in reflected light produced a significant increase in height, internode length, petiole length, leaf area, and dry weight. In Impatiens, only internode length was significantly increased by this treatment. For some traits, in both species, half-sib families differed significantly in the response to the light treatments. For several characters there were significant interactions between the light-quality treatment and family, suggesting that the response to light quality may have a genetic component. The changes induced by an alteration in light quality may have important fitness consequences.Key words: intraspecific variability, red to far-red ratio, morphological traits, Crotalaria incana, Impatiens sultanii.
Leucogyrophana lichenicola sp.nov., and a comparison with basidiomes and cultures of the similar Leucogyrophana romellii
Authors: Thorn R G , Malloch D W , Ginns J
Published: April 2011

A new species of Leucogyrophana (Boletales: Coniophoraceae) is described. Leucogyrophana lichenicola is compared with Leucogyrophana romellii Ginns, from which it differs in being lichenicolous, producing brightly colored sclerotia, and in certain cultural characters. The new species produces both basidiomata and orange sclerotia within and on the undersides of lichen mats of the genera Cladonia and Stereocaulon. It has been recorded from Ontario, Quebec, and the Northwest Territories in Canada and from Finland, Norway, and Sweden. The geographic and host ranges for L. romellii are extended. The cultures of L. lichenicola and L. romellii showed no activity for laccase, tyrosinase, peroxidase, or ligninase, but cellulase activity was present.Key words: lichenicolous fungi, brown-rot fungi, Basidiomycota, Boletales.
Genetic diversity in Puccinia striiformis Westend. f.sp. tritici revealed by pathogen genome-specific repetitive sequence
Authors: Shan Wei-xing , Chen Shou-yi , Kang Zhen-sheng , Wu Li-ren , Li Zhen-qi
Published: April 2011

DNA fingerprinting was used to examine genetic variation in populations of Puccinia striiformis Westend. f.sp. tritici, an obligate fungus that causes wheat stripe rust, using as a probe a moderately repetitive DNA sequence PSR331 that shows species specificity in the genome of this pathogen. One hundred and sixty isolates sampled from six provinces throughout China were examined for genetic variation over 26 putative genetic loci defined by PSR331 and the restriction enzyme BglII. Because of the dikaryotic nature of this fungus, DNA fingerprints can not differentiate heterozygotes from homozygotes. We refer to the PSR DNA fingerprints as phenotypes rather than genotypes. Phenotypic diversity analysis revealed a high level of genetic variation. A total of 97 phenotypes was detected among 160 isolates. Phenotypic diversity varied among regions, ranging from 0.3742 in Shaanxi to 0.9380 in Gansu, as calculated with the normalized Shannon's index. Genetic subdivision analysis revealed a low level of genetic differentiation (GST = 0.0084) among regions (Gansu, Henan, Shaanxi, Sichuan, and Yunnan provinces) as well as within regions (Gansu and Sichuan provinces). This, together with the detection of the same phenotypes among regions, provided the molecular evidence for gene flow in P. striiformis f.sp. tritici. The results support conclusions from virulence surveys that Tianshui of southern Gansu is probably the most important "hotspot" area with respect to the potential to generate and maintain virulence variation. DNA polymorphism analysis also detected potential hotspot areas in addition to southern Gansu. This may result in more difficulties in management of genetic variation and thus the potential virulence variation in P. striiformis f.sp. tritici as well as providing opportunities for searching disease resistance factors.Key words: genetic diversity, Puccinia striiformis, DNA fingerprinting, virulence variation.
Highly variable minichromosomes and highly conserved endoglucanase genes in the phytopathogenic fungusMacrophomina phaseolina
Authors: Jones Richard W , Canada Suzanne , Wang Haiyin
Published: April 2011

Electrophoretic karyotype analysis of 17 different isolates of Macrophomina phaseolina revealed the presence of from zero to six minichromosomes (less than 2000 kilobases (kb)), with the smallest size observed being approximately 785 kb. Each isolate had a unique minichromosome pattern, whether from the same field or from different continents. The highly variable minichromosome pattern contrasts to the high degree of conservation found in the two endoglucanase genes (egl1 and egl2) harbored by M. phaseolina. Gene structure was conserved, as judged by Southern analysis, and restriction fragment length was conserved. Digestion of DNA with Sal1 resulted in a 2-kb fragment containing egl1, and a 4-kb fragment contained egl2. Conservation of restriction fragment length suggests that the portions of the genome harboring the endoglucanases are less subject to rearrangement, relative to minichromosome DNA.Key words: charcoal rot, cell wall degrading enzymes, cellulase.
Polyamines conjuguées et différenciation florale chez le sapin de Douglas (Pseudotsuga menziesii (Mirb.) Franco)
Authors: Daoudi EL-Hassania , Bonnet-Masimbert Marc
Published: April 2011

To characterize as early as possible the status of flowering differentiation in Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), the variation of bound or conjugated polyamines is studied in the shoots of young plants (6 years old) during the period covering flowering initiation (between 30 and 75 days after bud burst). These compounds are also quantified in sexual and vegetative buds. The quantitative effects of treatments susceptible to stimulate the flowering (application of gibberellins and (or) calcium nitrate) on the level of conjugated polyamines are investigated in the shoots. The combination of gibberellins to calcium nitrate application strongly increases the flowering. Conjugated polyamines are particularly abundant in sexual buds and in the shoots of flowering plants. Sexual buds are also characterized by a ratio of conjugated putrescine to conjugated spermidine about four to six times higher than in vegetative buds. The accumulation of conjugated polyamines in the shoots accompanies bud sexualization, which suggests that conjugated polyamines may constitute potential markers of floral initiation in Douglas-fir.Key words: floral induction, flowering marker, conjugated polyamines, Douglas-fir.