bluuebunny/crossref_metadata_2025 huggingface dataset:
Nonsporulation in the Dutch elm disease fungus Ophiostoma ulmi: evidence for control by a single nuclear gene
Authors: Richards Wayne C.
Published: December 2007

A single nuclear gene controls nonsporulation in a novel isolate of the Dutch elm disease fungus Ophiostoma ulmi (Buism.) Nannf. This has been clearly demonstrated through segregation of the nonsporulating phenotype-in meiotic products recovered from crosses between a mutant nonsporulating isolate (WRB2-1) and wild-type sporulating isolates, between F1 progeny and their parents, and between F1 progeny. All crosses between nonsporulating and sporulating isolates yielded a 1:1 ratio for these two phenotypes in the meiotic products, whereas all crossings between isolates of the same phenotype produced meiotic products of that phenotype. The genetic stability of the nonsporulating phenotype was clearly shown when no disease symptoms were observed following artificial inoculation of the nonsporulating progeny into white elm, Ulmus americana L. Exposure to trifluoperazine, a calmodulin inhibitor, did not shift the nonsporulating isolates to the yeast phase, which supports our findings that nonsporulation is under genetic control rather than metabolic control. Key words: nonsporulation, Ophiostoma ulmi, mutant, single nuclear gene, meiotic products.
Effect of salinity, temperature, and growth regulators on the germination and early seedling growth of Atriplex griffithii var. stocksii
Authors: Khan M. Ajmal , Rizvi Yasmeen
Published: December 2007

Seed germination and early seedling growth of Atriplex griffithii var. stocksii from seeds collected from a saline desert habitat in Karachi, Pakistan, were studied. The seeds of A. griffithii did not germinate under high salt stress (516 mM NaCl). Best germination percentages were obtained in distilled water. Seed germination was stimulated in light at cooler alternating temperature (25:10 °C) and inhibited at warmer temperature (30:15, 30:20, and 35:25 °C) regimes. Early seedling growth showed responses towards salinity and temperature that were similar to the germination responses. Both GA3 and kinetin alleviated salinity-induced germination inhibition, and in most cases germination was stimulated by growth regulator treatments. A low concentration of kinetin (0.46 μM) and a high concentration of GA3 (28.9 μM) significantly promoted early seedling growth at all salinity treatments. Key words: Atriplex griffithii var. stocksii, seed germination, early seedling growth, salinity, temperature, growth regulators.
Variations in rooting ability of cuttings and in seed characteristics of five populations of Juniperus communis var. depressa from subarctic Quebec
Authors: Houle Gilles , Babeux Patrice
Published: December 2007

Juniperus communis var. depressa is a species with potential for site restoration in the Canadian subarctic and low arctic. We assessed this potential by evaluating the rooting ability of cuttings and the seed quality of five populations of the species along the east coast of Hudson Bay, in subarctic Quebec. Cuttings of male and female plants were sampled from each site. Cones were collected, and seeds were extracted, weighed, and then tested for viability. Cuttings from female plants rooted more easily than those from male plants. At high indolyl-3-butyric acid concentration, rooting of female cuttings was inhibited. Among-population differences in rooting ability were large: cuttings from the northernmost population rooted more easily than those from sites further south. Seed number per cone and seed mass and viability also varied significantly among sites. Of the populations studied, the northernmost one produced the lightest seeds and the southernmost one produced the heaviest seeds. Juniperus presents some potential for restoration, but transplant (cutting or seedling) performance in the field should be evaluated before any definite recommendations are made. There is some evidence that seed quality and rooting ability are characteristics that are negatively related in Juniperus, although the basis of such a trade-off has not been investigated. Key words: gender differences in rooting ability, indolyl-3-butyric acid, restoration, Whapmagoostui-Kuujjuaraapik.
Infection of wheat seed by Pyrenophora tritici-repentis
Authors: Schilder A. M. C. , Bergstrom G. C.
Published: December 2007

The seed infection process of Pyrenophora tritici-repentis, incitant of tan spot of wheat, was investigated, as were several influencing factors. Following inoculation of the wheat spike, P. tritici-repentis gained access to the seed by first colonizing the glume, lemma, or palea. Seed infection was first observed 3 d after inoculation, and infection incidence increased with time and with inoculum concentration. Wheat seeds were susceptible to infection by this fungus throughout most of their development, although inoculation at the milk stage resulted in the highest percentage of infected seeds. Susceptibility to foliar infection by P. tritici-repentis was not a good predictor of susceptibility to seed infection in four wheat cultivars tested in a glasshouse experiment, except perhaps in ‘BR 8’, which was significantly less susceptible than the other cultivars at early and late stages of seed development. In a field experiment, wheat seed infection by P. tritici-repentis occurred primarily after the early dough stage and was positively correlated with tan spot severity on the flag leaf shortly after anthesis. Key words: wheat, Pyrenophora tritici-repentis, Drechslera tritici-repentis, tan spot, seed infection, New York.
A history of mycology in Canada
Authors: Estey Ralph H.
Published: December 2007

This brief history of mycology in Canada has comments on the activities of more than 200 men and women. Emphasis is on those aspects of mycology in which Canadian mycologists, plant pathologists, forest pathologists, and geneticists have pioneered or excelled. It includes their studies on fossil fungi, aeromycology, the identity of wood destroying fungi in their mycelial stages, the coevolution of parasitic fungi and their host plants, mycotoxicology, psychrophilic fungi, predacious fungi, fungal genetics, and mycorrhizae, in addition to systematics, numerical taxonomy, and the use of computers in mycology. Key words: fossil fungi, fungal genetics, coevolution, predacious, mycorrhizae, taxonomy.
Germination requirements of Oenothera biennis seeds during burial under natural seasonal temperature cycles
Authors: Baskin Carol C. , Baskin Jerry M.
Published: December 2007

Buried seeds of Oenothera biennis, which have the potential to form long-lived seed banks, were investigated to determine whether or not they (i) undergo seasonal changes in their dormancy states and (ii) require light for germination. Seeds were buried in soil and exposed to natural seasonal temperature changes. Samples of seeds were exhumed at monthly intervals for 31 months and tested for germination in light and darkness at 12-h daily thermoperiods of 15:6, 20:10, 25:15, 30:15, and 35:20 °C. At maturity in autumn, seeds germinated to 84–95% in light at 30:15 and 35:20 °C, but to 0–69% at other test conditions. By late winter, seeds germinated to 95–100% at the five thermoperiods in light and in darkness. In summer and autumn, germination in light decreased at 15:6 °C, and in darkness it dropped to 0% at 15:6 °C and decreased at 20:10, 25:15, 30:15, and 35:20 °C. Following the second winter of burial, seeds germinated to near 100% at all thermoperiods in light and darkness. Thus, seeds exhibited an annual nondormancy – conditional dormancy cycle, being nondormant from midwinter to late spring and conditionally dormant in summer and autumn. Oenothera biennis is 1 of 10 species whose seeds live for 39–40 years or longer in soil and also have an annual conditional dormancy – nondormancy cycle. Seeds of six of these species, including O. biennis, can germinate in darkness in spring or summer at simulated habitat temperatures. Therefore, a light requirement for germination is not necessarily a prerequisite for long-term survival of buried seeds, and something other than darkness prevents germination of seeds of some species buried in soil. Key words: seed banks, buried seeds, germination, dormancy cycles, light requirement, Oenothera.
Neighbour effects on gender variation in Ambrosia artemisiifolia
Authors: Lundholm J. T. , Aarssen L. W.
Published: December 2007

In this study we tested the prediction that male gender allocation in natural populations of common ragweed (Ambrosia artemisiifolia L.) depends more on relative plant height within the neighbouring canopy than on absolute plant height. This is consistent with the assumption that success as a pollen donor for an anemophilous plant within a crowded population will be greater when neighbours are shorter than when neighbours are taller. Data on height and proximity of neighbours, irradiance, and target plant height, biomass, and gender allocation were collected from two natural populations. In one population, these data were also recorded for a group of target plants that had local neighbours artificially removed when the target plants were seedlings. Allocation to male flowers was most strongly positively correlated with height relative to that of close neighbours and with percent irradiance in natural populations. Numerous all-female plants were recorded among the smallest individuals that were suppressed by a dense overhead canopy of neighbours. No relationships were found between plant size and gender when plants were taller than their neighbours or when neighbours were artificially removed. Hence, previously reported size-dependent gender variation in this species may depend on the presence of neighbours. It is postulated that ragweed individuals may sense the presence of neighbours through the phytochrome system, and that effects of neighbours on light quantity and quality cues a shift to increased female function. However, plants that grew from the seedling stage without neighbours were heavier and more female but were not taller than plants with neighbours left intact. The interpretation of this effect is unclear but may reflect a change in plant architecture corresponding with the removal of neighbours. Key words: gender, plant height, plasticity, pollen dispersal, phytochrome, shading.
Primary production and management of seasonally flooded prairie marshes harvested for wild hay
Authors: Neill Christopher
Published: December 2007

Experimental spring-flooded and nonflooded water regimes were applied to prairie marshes dominated by whitetop grass (Scolochloa festucacea) in Manitoba, Canada, to examine their effects on aboveground and belowground primary production and to evaluate flooding management for wild hay production. Spring flooding increased marsh aboveground and belowground production. Annual and perennial forbs comprised a greater portion of aboveground production in nonflooded marsh. Two methods (soil coring and ingrowth into mesh bags) showed earlier commencement of belowground growth and greater belowground production in flooded marsh. Higher rhizome ingrowth in flooded marsh indicated that spring flooding increased plants' ability to replenish belowground reserves. The percentage of plant production allocated aboveground was greater in flooded marsh, but shifts in allocation were small compared with the absolute increases in production caused by flooding and could not account for the observed differences in aboveground production between flooding regimes. The strong plant growth response to flooding indicates that management that conserves or mimics the natural spring-flooded hydrologic regime can increase whitetop forage production and control invasion by undesirable species. Key words: belowground, hydrologic regime, prairie marsh, primary production, rhizomes, roots.
Phaeotheca dimorphospora sp.nov.: description et caractéristiques culturales
Authors: DesRochers Pierre , Ouellette G. B.
Published: December 2007

An unknown fungus isolated from an elm branch and inhibitory against Ophiostoma ulmi in vitro is described as Phaeotheca dimorphospora sp.nov. This dematiaceous deuteromycete propagates by endoconidia released after exfoliation of chlamydospore outer wall, as in mother cells of the type species Phaeotheca fissurella. However, P. dimorphospora differs from the type species by producing hyaline secondary ameroconidia between the endoconidial masses. Other ameroconidia, similar to the secondary ameroconidia, are produced through the chlamydospore outer wall. The optimal growth temperature of P. dimorphospora is 23 °C, whereas it is 15.5 °C for the type species. On media containing a high dextrose concentration (30 g ∙ L−1), colonies of P. dimorphospora are gray and crustose and grow slowly, at least initially. Conversely, on media with a low dextrose concentration (5 or 10 g ∙ L−1) colonies have a faster growth rate and appear whitish or ivory and fluffy. Key words: Phaeotheca dimorphospora, diagnosis, inhibition, Ophiostoma ulmi, Dutch elm disease.
Growth and osmoregulation of Boekelovia hooglandii in relation to salinity
Authors: Fujii Shuhei , Hellebust Johan A.
Published: December 2007

The growth and osmoregulation of Boekelovia hooglandii Nicolai et Baas Becking (Chrysophyceae) was investigated as a function of salinity. This chromophyte microflagellate was found to be euryhaline and also to require sodium for growth. The optimum sodium chloride concentration for growth was 0.2–0.4 M, and growth was severely inhibited in media with sodium chloride concentrations above 1 M. Using gas chromatography – mass spectroscopy analysis of cell extracts, it was established that the alga contains D-mannitol, myo-inositol, as well as the inositol derivative, cyclohexanetetrol. The content of cyclohexanetetrol and mannitol increased with increased salinity, while the content of inositol remained almost constant. Potassium and magnesium were the major intracellular cations. However, the content of cations and amino acids showed only minor increases with salinity over a wide salinity range. The contents of cyclohexanetetrol and mannitol increased rapidly when cells were subjected to hypertonic shocks. It was concluded that B. hooglandii utilizes cyclohexanetetrol and mannitol as osmoregulatory substances. Key words: Boekelovia hooglandii, chromophyte, cyclohexanetetrol, euryhaline, D-mannitol, myo-inositol, osmoregulation, salinity.
The role of clonal growth in the pathosystem Cirsium arvense – Puccinia punctiformis
Authors: Frantzen J.
Published: December 2007

The impact of the pathogenic rust fungus Puccinia punctiformis on the population dynamics of the clonal host plant Cirsium arvense was studied using field data and a matrix population model. To account for the spatial growth pattern of C. arvense, the study area was divided into cells of 10 × 10 cm. The cells were classified as empty (no C. arvense shoots), diseased (shoots infected by P. punctiformis), or healthy. The spatial growth pattern of C. arvense could be described as static or dynamic. Abundance of C. arvense depended largely on dynamic clonal growth. Shoots produced by dynamic clonal growth had a lower probability to be infected by P. punctiformis than shoots produced by static clonal growth. Dynamic clonal growth seemed to serve as a mechanism of disease escape. The results are discussed with respect to the use of P. punctiformis as biological agent for control of C. arvense in grasslands. Key words: clonal growth, disease escape, Puccinia punctiformis, Cirsium arvense, biological weed control.
Eleocharis compressa × Eleocharis erythropoda, a new natural hybrid spike rush from Ontario
Authors: Catling P. M.
Published: December 2007

Partially sterile plants from eastern Ontario are identified as Eleocharis compressa × Eleocharis erythropoda on the basis of intermediacy in perianth bristle length, tubercle shape, achene surface roughness, length of rhizome internodes, culm cross-section shape, and length of terminal lobes of scales. Both putative parents occurred with the hybrid plants. The hybrid plants had tardily deciduous scales and either bifid or trifid styles. They superficially resemble E. erythropoda most closely but differ markedly in their scaly rhizomes with shorter internodes 3.8 – 7 mm long. They are most readily distinguished from E. compressa by their elliptic or broadly rectangular culm cross sections and some perianth bristles exceeding 0.5 mm in length. This putative hybrid involves taxa in different subseries that would normally be regarded as too distantly related to permit hybridization. Key words: Eleocharis compressa, Eleocharis erythropoda, Cyperaceae, hybrid, taxonomy, classification.
Biological control of foot and root rot in pea caused by Fusarium solani with nonpathogenic Fusarium oxysporum isolates
Authors: Oyarzun P. J. , Postma J. , Luttikholt A. J. G. , Hoogland A. E.
Published: December 2007

Two nonpathogenic isolates of Fusarium oxysporum were examined for their ability to counteract F. solani f.sp. pisi, which causes foot and dry root rot in pea. Antagonism was studied in vitro, in a sterilized field soil, and in six natural field soils. Besides native F. solani, other typical pea root rot pathogens occurred in the natural field soils. Both nonpathogenic F. oxysporum isolates reduced disease severity and prevented the plant weight losses that occurred owing to F. solani f.sp. pisi in sterilized soil. Precolonization of sterilized soil with nonpathogenic isolates increased the antagonistic effect. Also, in highly infested field soils the addition of nonpathogenic isolates resulted in lower disease severities and higher yields. Colonization of the soil organic matter by F. oxysporum reached 100% in sterilized soil, independent of the presence of F. solani, and 40 – 90% in naturally infested soils containing native F. solani. The performance of benomyl-resistant mutants of F. oxysporum did not differ from their wild types. Key words: antagonism, soil organic matter, colonization, Pisum sativum.
Evidence for the hybrid origin of Carex knieskernii with comments on hybridization in the genus Carex (Cyperaceae)
Authors: Waterway Marcia J.
Published: December 2007

Carex knieskernii, originally described as a distinct species, is shown to be a sterile hybrid between Carex arctata and Carex castanea based on evidence from allozyme variation, chromosome numbers, morphology, and geographical distribution. The two parental species differed at eight enzyme-coding loci; C. knieskernii showed the expected heterozygous pattern at each of these loci. Individuals of C. knieskernii were highly sterile and the enzyme patterns suggested that they were F1 hybrids formed independently at each location. Chromosome numbers determined for 27 individuals of C. arctata (n = 27, rarely 26) agreed with previously published counts. The eight counts of C. castanea (n = 22) differed from the one previous count of 2n = 64. Individuals of C. knieskernii from five different populations all had disturbed meiosis with irregular pairing and ca. 49 chromosomes. A canonical discriminant analysis of morphological data from population samples of the three taxa clearly separated C. arctata and C. castanea, with the individuals of C. knieskernii having intermediate scores on the first canonical axis. Carex knieskernii is a widespread but rarely occurring hybrid that is found where the ranges of the parental species overlap and the blooming times are synchronous. The sterility of this hybrid, the obvious disruptions of normal meiotic pairing, and the large genetic distance between the parental species based on allozyme variation suggest that although the two species hybridize, they may not be closely related. Key words: Carex knieskernii, Cyperaceae, hybridization, allozyme variation, chromosome numbers.
Interactions between Norway spruce (Picea abies) and Heterobasidion annosum. I. Infection of nonsuberized and young suberized roots
Authors: Heneen W. K. , Gustafsson M. , Karlsson G. , Brismar K.
Published: December 2007

Nonsuberized and young suberized roots of Norway spruce (Picea abies) were inoculated with an S-strain of Heterobasidion annosum for 2–20 days. The roots were sectioned for light microscopy and transmission electron microscopy. They were susceptible to infection at both stages of development. The host reaction to delimit the infection was the formation of a necrotic ring barrier in the outer cortex. In cases where the inner cortex also became infected, fungal hyphae accumulated just before the endodermis, which acted as a new barrier. Only in nonsuberized roots did the hyphae succeed in penetrating the stele, and within 3 days after inoculation the stele was almost completely digested. Other resistance reactions included accumulation of phenolic deposits, secondary thickening of cell walls, and formation of papillae. The hyphae were able to grow within and across cell walls. The presence of translucent areas around penetrating hyphae possibly reflected the digestive action of fungal enzymes. The hyphae showed signs of degeneration when entrapped in encompassing cellular deposits. Key words: Norway spruce, Heterobasidion annosum, root infection, nonsuberized roots, young suberized roots, microscopy.
Pectic enzyme patterns as a taxonomic tool for the characterization of Gremmeniella spp. isolates
Authors: Lecours Nicole , Toti Luigi , Sieber Thomas N. , Petrini Orlando
Published: December 2007

Isolates of different species of the conifer pathogen Gremmeniella, including some cultures from western Canada and some endophytic isolates, have been characterized by pectic enzyme patterns. Pectinase isozyme patterns are in good agreement with results of electrophoresis of mycelial water-soluble proteins. The North American and European races of G. abietina var. abietina can be distinguished on the basis of a cathodal polygalacturonase band present in all isolates of the former but absent in the latter. Another band, present in all isolates, shows polymorphisms related to the host from which the isolates are derived, thus making it possible to group them on a pathogen race – host genus basis. Sixteen isolates originating from western Canada that were previously found to belong to the North American race with a water-soluble protein assay were also found to belong to that race following the analysis of pectic enzymes. It was not possible using our assay to distinguish between isolates of Brunchorstia pinea var. cembrae and others derived from other Pinus spp. Among the endophytic isolates, the Pinus cembra endophytes show the same polygalacturonase profile as those from diseased pines. Key words: ascomycetes, diagnostic tools, electrophoresis, plant pathology, taxonomy.
Analyse structurale et architecture de l'inflorescence des Begoniaceae
Authors: Goulet Isabelle , Barabé Denis , Brouillet Luc
Published: December 2007

The inflorescence structure of Begoniaceae was analyzed taking into account their degree of symmetry. Qualitative and quantitative analyses of 71 species led to the recognition of nine architectural models. When the whole plant is considered, the inflorescence of Begoniaceae is a thyrse. Comparative analyses of the models allowed to determine at what level symmetry or asymmetry is found. There is a correlation between the total lengths of axes and between flower numbers on the best and least developed sides of an inflorescence. For the whole family, the difference between the two sides of the inflorescence is significant for the former, and not for the latter. Divergence angles on the best developed side do not differ from those on the least developed one for a same ramification, and likewise between successive levels of ramification. Thus, the inflorescence appears asymmetrical if total length of axes is considered. These results tend to support the hypothesis that the Begoniaceae are fundamentally asymmetrical. Inflorescence symmetry is found in some groups by stabilization and compensation of different asymmetric components at the global and local levels. Nevertheless, inflorescence asymmetry does not seem to be related to plant architecture, although it seems to be related to the degree of foliar asymmetry. Key words: Begoniaceae, inflorescence, cyme, inflorescential architecture, structural asymmetry.
Genetic structure of Pyrenophora teres populations determined with random amplified polymorphic DNA markers
Authors: Peever Tobin L. , Milgroom Michael G.
Published: December 2007

The genetic structure of Pyrenophora teres, an ascomycete fungus that causes net blotch of barley, was examined using random amplified polymorphic DNA (RAPD) markers. Twenty-seven random oligonucleotide primers were screened against DNA from 16 isolates of P. teres of diverse geographic origin. Five primers gave scorable, reproducible DNA products (bands) suitable for population genetic studies. Genetic analyses of bands produced by two of the primers revealed single locus segregation in three of four crosses, indicating that these RAPDs can be interpreted as alleles at genetic loci. Allele frequencies were determined for 10 putative RAPD loci from five primers in 22–35 isolates of P. teres sampled from each of five geographically separated populations in Canada, Germany, and the U.S.A. Eight RAPD loci were polymorphic in at least one population and two loci were monomorphic in all five populations. Variation in allele frequencies (allelic diversity) among the five populations was partitioned into within- and among-population components using Nei's GST. A GST value of 0.46 was obtained among all populations indicating that approximately 46% of the total genetic variability detected was due to differentation among populations compared with 54% within populations. A GST value of 0.33 was obtained among the North American populations only. From five to nine multilocus genotypes were found in each population. Nine genotypes occurred exclusively in the German population and four exclusively in the New York population. The other populations had one or two unique genotypes. Gametic disequilibrium values (nonrandom associations of RAPD loci) were calculated among all pairs of polymorphic loci within each population. Eleven of 49 values were significantly different from 0 (P < 0.05); 8 of the 11 significant gametic disequilibrium values occurred in the New York population. Highly significant gametic disequilibrium was detected between the same two RAPD loci in three different populations, suggesting that these loci are genetically linked. Two different multilocus analyses revealed that the genetic structures of the Alberta, North Dakota, and German populations but not the New York population were consistent with random sexual reproduction occurring in these populations. Key words: polymerase chain reaction, population genetics, fungi, genetic differentiation.
Développement et polymorphisme racinaires chez de jeunes semis d'hévéa (Hevea brasiliensis)
Authors: Roux Yannick Le , Pagès Loïc
Published: December 2007

The major problems (bad anchorage, water stress, and root disease) with the cropping of the rubber tree (Hevea brasiliensis) are related to the architecture of its root system. So, the morphogenetic properties of the various roots that emerge during the development of the young seedlings are described to improve our understanding of the dynamics of root system architecture. In this study, the development of the root system of 12 seedlings grown for 40 days in root observation boxes has been recorded on a daily basis and analysed. Additional observations were also made on plants grown in pots or in the field for a 60-day period. This analysis of the sequential differentiation of the root system allowed us to distinguish five different root types according to their spatial and temporal location at emergence: (i) taproot, (ii) early first-order lateral roots, (iii) acropetal first-order lateral roots, (iv) late first-order lateral roots, (v) second-order lateral roots. Large variations and close relationship were found within the growth and branching characteristics on one hand, and within anatomical characteristics on the other (number of xylem poles, external diameter, and stele diameter). These between-type variations were also observed, to a lesser extent, among roots from the same type. The continuity of these development characteristics, which were shown to be acquired early, led us to characterize a morphogenetic gradient. This gradient is a reference scale to understand the morphological plasticity of the root system growing in other mediums. Key words: root system, development, morphogenesis, anatomy, root observation box, Hevea brasiliensis.
Penicillium tricolor, a new mould species from Canadian wheat
Authors: Frisvad Jens C. , Seifert Keith A. , Samson Robert A. , Mills John T.
Published: December 2007

A new Penicillium species, P.tricolor, morphologically similar to P. aurantiogriseum and allied species, was isolated from red spring wheat and durham wheat grains in Saskatchewan and Manitoba. Penicillium tricolor is classified in Penicillium subg. Penicillium and is characterized by the following combination of diagnostic characters: tuberculate conidiophore stipes, greyish turquoise smooth conidia, orange-brown exudate droplets and colony reverse, and production of the mycotoxins xanthomegnin, viomellein, vioxanthin, terrestric acid, and the alkaloids rugulosuvine, leucyltryptophanyldiketopiperazine, verrucofortine, puberuline, and asteltoxin. Key words: Penicillium tricolor, taxonomy, wheat, mycotoxins.
The native rust fungi of Hawaii
Authors: Gardner Donald E.
Published: December 2007

F.L. Stevens (1925. Bernice P. Bishop Mus. Bull. No. 19) published the first comprehensive list of fungi in Hawaii, recognizing 7 species of endemic rusts and 10 species probably indigenous. Stevens considered this small number of rusts particularly noteworthy in comparison with the rust floras of other areas with which he was familiar. He ascribed the scarcity to the geographic isolation of the Hawaiian Islands from significant land masses. Currently, of the more than 74 rusts in Hawaii, 22 are considered native, of which 13 are endemic and 9 indigenous. The rust flora, like other groups of native organisms of Hawaii, provides interesting examples of biological colonization and adaptation to remote insular environments. Key words: endemic, Hawaii, indigenous, rusts.
Mycorrhizal activity in warm- and cool-season grasses: variation in nutrient-uptake strategies
Authors: Hetrick B. A. D. , Wilson G. W. T. , Schwab A. P.
Published: December 2007

Because cool-season grasses display little or no mycorrhizal responsiveness in prairie soil, it is unclear whether the high levels of mycorrhizal activity observed previously in these grasses represent nutrient uptake by external hyphae or simply metabolism of stored fungal reserves in roots. To distinguish between these hypotheses, a warm-season grass, Andropogon gerardii, or a cool-season grass, Bromus inermis, were grown at two temperatures on one side of a pot divided by a 43-μm nylon root barrier. Mycorrhizal function was assessed by measuring the amount of 32P translocated from one side of the pot to plants on the other side. As a control, mycorrhizal hyphae crossing the barrier were severed manually. Approximately 100 times more 32P was observed in mycorrhizal B. inermis grown at 18 °C versus 29 °C, and in B. inermis with intact versus severed hyphae at the cooler temperature. In contrast, A. gerardii accumulated approximately 4 times more 32P at 29 °C than at 18 °C, and approximately 100 times more with intact versus severed hyphae at the warmer temperature. Thus, it appears that mycorrhizal hyphae are highly active in both plant species regardless of the host's mycorrhizal responsiveness. Furthermore, mycorrhizal activity is highest at the temperature that favors growth of each species. The considerable activity of mycorrhizae in B. inermis is enigmatic since it usually has no biomass response. To further clarify the relationship between nutrient uptake and biomass response, both plant species were fertilized with a range of P levels and grown at a neutral temperature that supported the growth of both species. Although the concentration of P in B. inermis plant tissue increased in response to fertilization, there was no corresponding increase in biomass. In contrast, for A. gerardii, there was a direct and positive relationship between P fertilization and biomass produced, but tissue P concentrations remained relatively stable. Mycorrhizal symbiosis had no overall effect on biomass of B. inermis but significantly improved the growth of A. gerardii. These experiments showed clear differences in the growth strategies used by these two plant species. It is unclear whether these are differences that can be attributed to warm- and cool-season grasses in general. Short-term biomass responses as a measure of a plant's reliance on the symbiosis may not entirely reflect the contribution of the symbiosis if plants store nutrients with subsequent and perhaps delayed effects on fecundity, offspring performance, or even biomass. However, if the stored nutrient merely represents luxury consumption, this could still affect competitive ability because luxury consumption preempts the availability of nutrients for competitors. Key words: mycorrhizal responsiveness, mycorrhizal dependence, big bluestem, smooth bromegrass.
Interaction of abscisic acid and jasmonic acid on the inhibition of seed germination and the induction of freezing tolerance
Authors: Wilen Ronald W. , Ewan Bruce E. , Gusta Lawrence V.
Published: December 2007

The possible interaction of the two growth regulators, abscisic acid and jasmonic acid, on the inhibition of seed germination and the induction of freezing tolerance in bromegrass (Bromus inermis Leyss) cell cultures was investigated. Both of these processes are known to be affected by exogenous abscisic acid. Alfalfa (Medicago sativa), cornflower (Centurae gynura), cress seed (Lepidium sativum), maize (Zea mays), and wheat (Triticum aestivum) seeds were treated with varying concentrations of abscisic acid and jasmonic acid, either alone or in combination. In all species, seed germination was inhibited by 10 μM abscisic acid at 23 °C. In contrast, at 23 °C, jasmonic acid was partially inhibitory only at 100 μM; however, 10 μM jasmonic acid inhibited germination in all species at 10 °C. Jasmonic acid in combination with abscisic acid resulted in a higher degree of germination inhibition at 23 °C in all species than either growth regulator applied separately. Treatment of a bromegrass suspension cell culture with 75 μM abscisic acid at 25 °C for 7 days increased the freezing tolerance from −10 °C to lower than −35 °C. In contrast, jasmonic acid (0.25–75 μM) had no detectable effect on freezing tolerance. Jasmonic acid in combination with suboptimal concentrations of abscisic acid, however, enhanced the abscisic acid-induced freezing tolerance in these cells. In contrast, a combination of 75 μM abscisic acid and 25 or 75 μM jasmonic acid reduced the freezing tolerance of these cells compared with treatment with abscisic acid alone. Key words: abscisic acid, freezing tolerance, germination, jasmonic acid.
Fossil legume fruits from tertiary strata of Puebla, Mexico
Authors: Magallón-Puebla Susana , Cevallos-Ferriz Sergio R. S.
Published: December 2007

A small assemblage of fossil legume fruits, leaf fragments, and leaflets has been recovered from the Tertiary (Oligocene) "Los Ahuehuetes" flora near the town of Tepexi de Rodríguez, Puebla, in south-central Mexico. Five legume fruits are described and compared with fruits of extant genera. Four fruit types were identified as belonging to the modern genera Prosopis (Mimoseae; Mimosoideae), Mimosa (Mimoseae; Mimosoideae), Lysiloma (Ingeae; Mimosoideae), and Sophora (Sophoreae; Papilionoideae). Another fruit exhibits a combination of characters unknown among extant legumes, and although superficially similar to some species of Papilionoideae, it represents an extinct genus. The four identified genera are diverse in the extant vegetation of Mexico; in fact, Mexico represents an important area of distribution for them. The presence of Prosopis, Mimosa, Lysiloma, and Sophora in the fossil flora of Puebla documents the occurrence of these genera in this part of their present area of distribution by the Oligocene. The climatic affinities of modern species of Mimosa, Lysiloma, and Sophora are so varied as to preclude any useful paleoclimatic inference. Prosopis is regularly associated with arid environments; however, the genus has been reported from fossil localities where humid conditions prevailed. This observation, together with the assemblage of plants that co-occur in the Los Ahuehuetes flora, suggests that plant communities of the past may have been composed, at least partly, of elements that today are associated with different habitats and environmental conditions. The fossil legume fruits from Los Ahuehuetes flora add to the previously known diversity of Leguminosae by the Tertiary, confirm tropical America as one of the important areas of radiation and diversification for Leguminosae, and contribute to the knowledge of Tertiary floras of southern North America. Key words: Leguminosae, Tertiary, Mexico, paleobotany, fossil legume.
Evidence against the existence of varieties in Arctagrostis latifolia ssp. arundinacea (Poaceae)
Authors: Aiken S. G. , Lefkovitch L. P. , Gardiner Susan E. , Mitchell W. W.
Published: December 2007

The morphological diversity of North American specimens of Arctagrostis latifolia ssp. arundinacea (Trin.) Tzvelev was evaluated for possible varieties within the subspecies by considering (i) descriptions of three previously recognized taxa included in the subspecies, (ii) measurements of spikelet characters of the types of five taxa, (iii) Macoun's illustrations of spikelet diversity, (iv) a morphological study of 130 herbarium specimens, and (v) a transplant garden study. Characters thought to be uninfluenced by environment were examined. These included (i) the seed protein banding patterns revealed by SDS–PAGE, (ii) the guard cell sizes from plants of known chromosome number, and (iii) a study of anther lengths and pollen diameters. The data do not support the recognition of varieties. Key words: SDS–PAGE, transplant garden, pollen, chromosome number, guard cells, Arctagrostis, Poaceae, taxonomy.
Mechanically isolated photosynthetic cells from asparagus cladophylls originate from two distinct tissue locations
Authors: Guinel Frédérique C. , Bown Alan W.
Published: December 2007

Photosynthetically competent cells from cladophylls of Asparagus densiflorus (Kunth) Jessop, previously called Asparagus sprengeri Regel, are readily isolated using mechanical disruption of tissue. They have been used in many physiological and biochemical studies. Light microscopy indicates an apparently homogeneous population of cells. However, the tissue locations of the isolated cells is not clear, and more than one cell type may be present. A light microscope examination of fresh and cleared cladophyll tissue revealed a complex articulated network of photosynthetic cells between the epidermal and vascular tissues. Three types of photosynthetic cell were identified. The first type, referred to as the spongy mesophyll cells, had a shape distinct from that of the isolated cells; they were elongated and often branched. The two other types of cells were similar in shape to the isolated cells and were found attached to the epidermal and spongy mesophyll tissues. Those attached to the epidermis, the palisade cells, had a length to width ratio of 2.7 (± 0.5), while those attached to the spongy cells had a length to width ratio of 2.2 (± 0.5). Analysis of the isolated photosynthetic cells indicated an overall ratio of 2.4 (± 0.7) and that only the last two cell types were represented. The elongated spongy mesophyll cells were therefore excluded during the isolation procedures; because of their elongated irregular shape they were probably eliminated during cell filtration to remove debris. Consequently, isolated cells represent two distinct cell types that may respond differently to experimental treatments. Key words: asparagus, cladophyll, isolated photosynthetic cell, structure.
Meiosis, septal pore architecture, and systematic position of the heterobasidiomycetous fern parasite Herpobasidium filicinum
Authors: Bauer Robert , Oberwinkler Franz
Published: December 2007

Meiosis, spindle pole body cycle and septal pores in Herpobasidium filicinum were examined using light and electron microscopy and compared with findings in the Uredinales and other simple-pored heterobasidiomycetes. The septal pore apparatus in Herpobasidium filicinum is rustlike, and the nuclear characteristics are also similar but not identical to those found in the Uredinales. Some details, such as the spindle pole body behaviour at prophase, the presence of a complete wrapping of endoplasmic reticulum surrounding the nucleus during division, the extension of the spindle pole body into the cytoplasm during division, and the nucleolus behaviour, distinguish Herpobasidium filicinum from the rusts. On the other hand, nuclear division and spindle pole body characteristics in Herpobasidium filicinum show some features common with Cryptomycocolax abnorme. However, Herpobasidium filicinum shares more important nuclear features with Pachnocybe ferruginea, Eocronartium muscicola, Helicobasidium mompa, and Helicobasidium brebissonii than with the Uredinales or Cryptomycocolacales. Apart from the phylogenetic implications of the ultrastructural data, the most interesting observation in the present work is the unusual type of meiosis. No evidence for meiosis II was found in basidia of Herpobasidium filicinum. Instead, the genesis of the interphase I spindle pole body in Herpobasidium filicinum is essentially identical to the basidiomycetous postmeiotic and intermitotic spindle pole body duplication. Key words: Herpobasidium filicinum, heterobasidiomycetes, meiosis, septal pore, spindle pole body, ultrastructure.
Localization and quantification of cell wall phenolics in European corn borer resistant and susceptible maize inbreds
Authors: Bergvinson D. J. , Arnason J. T. , Pietrzak L. N.
Published: December 2007

Three maize inbreds (MBR 6796-15, B86, and CI31A) resistant to leaf feeding by the European corn borer Ostrinia nubilalis, and one susceptible inbred (MS72), were evaluated for insect resistance and phytochemical composition to gain a better understanding of maize-resistance mechanisms. Insect resistance was evaluated using laboratory bioassays that demonstrated that immature leaf tissue is the preferred feeding substrate. Phytochemical analyses were conducted for leaf protein, hydroxamic acid content, and hydroxycinnamic acids bound to the cell wall for both immature and mature leaf tissue. Hydroxycinnamic acid distribution in cell walls was examined using five stains, autofluorescence, and microspectrophotometry. Phloroglucinol, azure B, diazotized salts of p-nitroaniline and sulfanilic acid, and chlorine sulfite allowed visualization of phenolic localization but were not quantitative. Microspectrophotometer readings of epidermal, phloem, and xylem cell walls confirmed staining results, showing extremely low cell wall hydroxycinnamic acid levels in epidermal cell walls of immature leaf tissue. Foliar nitrogen content was not related to insect feeding preference. Hydroxycinnamic acid fortification of epidermal cell walls appears to correlate best with corn borer feeding preference, accounting for differential resistance between inbred lines and between tissue maturities. Microspectrophotometry may be useful as a technique for monitoring phytochemical resistance mechanisms in breeding programs. Key words: maize, Ostrinia nubilalis, phenolic, hydroxycinnamic acids, cell wall, microspectrophotometry, resistance.
Composition and spatial structure of plant communities on southeastern Victoria Island, arctic Canada
Authors: Schaefer James A. , Messier François
Published: December 2007

We used multivariate methods to investigate the composition and spatial organisation of tundra plant communities in the Wellington Bay region of southeastern Victoria Island (69°N, 106°W). Ordination and classification of sites at an intermediate scale (≈ 1 ha) were conducted using principal components analysis and sums of squares agglomerative clustering on a matrix of standardized chord distances. The findings suggested eight vegetation classes. These communities are described floristically. At this spatial scale, the vegetation showed correspondence to elevation, slope, and thickness of soil, but not to aspect. The spatial patterns of multiple plant species and physical variables (i.e., slope of terrain and thickness of soil) were examined using multiscale ordination and double logarithmic regressions of variance on distance, respectively. Multiscale ordination revealed ever-increasing plant heterogeneity with distance (0.25 – 1600 m) and suggested only weak general patterns at scales ≤ 200 m. Similarly, variance in the physical factors tended to increase continually with distance. Both the vegetation and physical environment thus appeared to be organised on gradients. Key words: Arctic, classification, ordination, spatial scale, tundra.
Classification of vegetation communities in which geese rear broods on the Yukon – Kuskokwim delta, Alaska
Authors: Babcock Christopher A. , Ely Craig R.
Published: December 2007

Plant communities are described from an area on the Yukon – Kuskokwim (Y-K) delta of Alaska that is used extensively for brood rearing by three species of geese. Earlier studies identified plant species important as food for young geese, but few studies describe or quantify plant communities. We classified species presence or absence information from over 700 quadrats using a two-way indicator species analysis (TWINSPAN) and then tested for agreement of signatures on colour infrared air photos with the identified communities. Sedges were found to dominate all but the wettest and driest communities. Most of the brood-rearing area was covered by Carex ramenskii and Carex rariflora meadows, ponds, Carex mackenziei-dominated pond margins, and C. ramenskii and grass levee meadows. Our interpretation of airphotos accurately predicted vegetation community classes, which will facilitate future studies of habitat selection by geese during the time they are rearing young. The TWINSPAN classification was comparable to classifications of studies conducted elsewhere on the Y-K delta. The interpretation of air photos will enable the identification and evaluation of wetland vegetation complexes and potential goose brood-rearing areas away from our study site. Key words: air-photo interpretation, Alaska, plant communities, salt marsh, Yukon – Kuskokwim delta.
The genus Bombardioidea
Authors: Krug John C. , Scott James A.
Published: December 2007

The taxonomy and ecology of the fungal genus Bombardioidea (Ascomycotina, Lasiosphaeriaceae) are discussed. Descriptions and illustrations are provided for the four accepted species: Bombardioidea anartia n.sp., Bombardioidea bombardioides, Bombardioidea serignanensis, and Bombardioidea stercoris. Observations from axenic culture are provided for B. bombardioides, and an Angulimaya (Phialophora-like) anamorph is reported. The coriaceous and gelatinous aspects of the peridium are considered to be adaptations to xerophytic environments. Key words: Bombardioidea, Angulimaya, Phialophora, coprophilous, ecology, taxonomy.
Seasonal occurrence of freshwater hyphomycetes on submerged fallen leaves in canal waters
Authors: Bareen Firdaus-E- , Iqbal S. H.
Published: December 2007

A total of 40 species of hyphomycetes were observed on submerged leaves during 1 year in canal waters. The number of species increased with leaf fall. The maximum number of species was observed during winter when leaf fall is maximum and the temperature falls to a minimum. Dimorphospora foliicola, Flagellospora penicillioides, Lunulospora curvula, Margaritispora aquatica, Tetracladium marchalianum, and Triscelophorus monosporus sporulated on leaves throughout the year. Most of the other species could be designated as winter and autumn species, with a shorter period of occurrence. Key words: freshwater hyphomycetes, submerged leaves, canal waters.