bluuebunny/crossref_metadata_2025 huggingface dataset:
Mineral storage in Cucurbita embryos. III. Calcium storage as compared with storage of magnesium, potassium, and phosphorus
Authors: Ockenden I. , Lott J. N. A.
Published: April 2011

Neutron activation analysis was used to measure the concentrations of Mg, K, Ca, and P stored in embryos of Cucurbita maxima, Cucurbita andreana, and their reciprocal hybrids. The embryos contained much higher concentrations of Mg, K, and P than Ca. However, Ca was the only one of the four minerals that was significantly different in the four kinds of embryos. Although all four minerals were stored in higher concentrations in the small root–shoot axes than in the large cotyledons, the proportion of total Ca stored in the axis was higher than the proportion of the other three minerals. P was the predominant mineral in the embryos, K was highest in the seed coats. Differences in mineral concentrations of embryo parts and seed coats indicated a marked selectivity in embryo mineral uptake.
Effect of freezing resistance and low-temperature stress on development of cottony snow mold (Coprinus psychromorbidus) in winter wheat
Authors: Gaudet D. A. , Chen T. H. H.
Published: April 2011

The relationship between snow mold resistance and freezing resistance was studied under controlled-environment conditions, using winter wheat (Triticum aestivum L. em. Thell) cultivars varying in freezing resistance and resistance to cottony snow mold (Coprinus psychromorbidus Redhead & Traquair). Cultivars varying in freezing resistance were equally susceptible to C. psychromorbidus. There existed a negative relationship between snow mold resistance and freezing resistance. Sublethal, subzero freezing temperatures between −3 and −12 °C predisposed the winter wheat cultivar 'Winalta' to increased damage by C. psychromorbidus. A synergistic effect resulting in increased mortality was observed when winter wheat plants received a combination of low-temperature stress and inoculation with C. psychromorbidus. In hardened winter wheat plants, sublethal levels of snow mold damage following 6 weeks incubation with C. psychromorbidus resulted in a reduction in freezing resistance or LT50 (50% killing temperature) of approximately 7 °C compared with the noninoculated controls. The possible role of low-temperature stress on the susceptibility of winter wheats to C. psychromorbidus and of snow mold infection on the retention of freezing resistance in winter wheats during winter in the central and northern Canadian prairies is discussed.
Asparagus mesophyll cells and the influence of CO2 availability on changes in ATP levels in response to light
Authors: Ciccarelli Bruce , Bown Alan
Published: April 2011

Suspensions of mechanically isolated, photosynthetically competent Asparagus sprengeri Regel mesophyll cells were stirred in 10 mL of pH 6.3 medium contained in an open glass vessel. The influence of medium aeration with normal or CO2-free air on the steady-state ATP level was determined. In illuminated cells aerated with CO2-free air, the ATP level was 1.10 nmol ATP/106 cells. However, in the presence of CO2, levels were 0.89 nmol ATP/106 cells. The transition from CO2-free to normal air resulted in ATP levels dropping 24% within 15 min. This relationship between reduced CO2 availability and increased ATP levels was also demonstrated when a change from normal to CO2-free air resulted in a 27% increase in ATP levels. When aeration with normal air ceased, the ATP level in the illuminated cell suspension rose approximately 20%. If cells were aerated with normal air, the onset of illumination resulted in a 34% decrease in the ATP level. In contrast, the onset of illumination had little influence on ATP levels in suspensions exposed to CO2-free air. With normal air, removal of illumination resulted in a 25% increase in ATP, whereas in CO2-free air, there was a 10% increase. The data demonstrate that the influence of illumination on ATP levels is determined by the availability of CO2. They are discussed with reference to conflicting reports concerning the influence of illumination on steady-state ATP levels and the likely effect of varying CO2 levels on the rate of photorespiration.
Effects of time of nitrate application on nitrate reductase activity, nitrate uptake, and symbiotic dinitrogen fixation in faba bean and pea
Authors: Chalifour François-P. , Nelson Louise M.
Published: April 2011

The effects of increasing concentrations of [Formula: see text] (0, 5, 10, or 15 mol∙m−3) supplied at planting or 7 or 14 days after planting were studied in faba bean (Vicia faba L.) and pea (Pisum sativum L.) inoculated with Rhizobium leguminosarum biovar viceae isolate 175F19. Averaged over all times of [Formula: see text] application, N2 fixation (acetylene reduction) was inhibited significantly more in pea than in faba bean. Times of [Formula: see text] application had little effect on N2 fixation for faba bean. In contrast, N2 fixation in pea was most strongly inhibited when [Formula: see text] was applied at planting and showed a decreasing sensitivity as [Formula: see text] applications were delayed to 7 and 14 days after planting. At all times of [Formula: see text] application, as the levels of [Formula: see text] increased, the proportion of total plant nitrate reductase activity contributed by leaves and roots remained relatively constant in faba bean, but these proportions increased and decreased, respectively, in pea. Nitrate was taken up at higher levels and at a greater rate in pea than in faba bean. The lower capacity for [Formula: see text] uptake in faba bean could contribute to the greater tolerance of the symbiosis to [Formula: see text] compared with that in pea.
Autotoxicity in isolated microspore cultures of Brassica napus
Authors: Kott L. S. , Polsoni L. , Ellis B. , Beversdorf W. D.
Published: April 2011

Effects of a suspected toxin in isolated microspore cultures of oilseed rape, Brassica napus L., were observed in the reduced levels of embryogenesis and in altered embryo morphology. The toxin appeared to be generated by the cultured spores themselves. Inclusion of binucleate microspores in the cultures, along with younger, potentially embryogenic spores, was correlated with these negative effects and could be simulated by inoculation of embryogenic cultures with media generated from high-density cultures of older spores. Replacement of culture media 24 h after microspore isolation effectively reduced the levels of the autotoxins in the medium and allowed normal embryo development.
Effects of preconditioning on subsequent water relations, stomatal sensitivity, and photosynthesis in osmotically stressed black spruce
Authors: Zwiazek Janusz J. , Blake Terence J.
Published: April 2011

The effects of stress conditioning with polyethylene glycol on water relations and photosynthesis in preconditioned ramets were compared with those of unconditioned black spruce (Picea mariana Mill. BSP). Preconditioned plants maintained lower osmotic and water potentials and higher turgor potentials (measured as a difference between osmotic and water potentials), but photosynthetic rates were similar in both groups of plants. The conditioning treatment increased stomatal sensitivity to water stress, and stomatal conductance was lower in preconditioned plants soon after water stress was imposed. Preconditioned plants maintained significantly lower osmotic potentials during a severe water stress and were able to maintain turgor at the time when unconditioned plants wilted. Water-use efficiency was not affected by stress-conditioning treatment.
Multivariate analyses of hybridization between Betula cordifolia and B. populifolia (Betulaceae)
Authors: DeHond Patricia E. , Campbell Christopher S.
Published: April 2011

Multivariate analyses of Betula cordifolia Regel, B. populifolia Marsh., and B. × caerulea Blanchard in a mixed population in northern Maine show that the latter is a hybrid between the former two species. Hybrid status of B. × caerulea is further supported by the fact that two putative hybrid individuals have the same chromosome number as reports for the two parental species and that all three taxa have overlapping flowering times at this site. Studies of pollen germination and stainability and seed germination show that the putative hybrids are fertile. Betula papyrifera Marsh., which is also present in this mixed population and was included in the analyses, flowers earlier than B. cordifolia and B. populifolia, and it apparently does not hybridize with the latter species at this site. Characters that have not been used prior to this study and that are among the best discriminators between B. cordifolia, B. papyrifera, and B. populifolia are number and width of preformed staminate catkins and length and diameter of overwintering vegetative buds.
Generic relationships within Leonticeae (Berberidaceae)
Authors: Loconte Henry , Estes James R.
Published: April 2011

Phenetic analyses of morphological characters of Leonticeae reveal three distinct groups of operational taxonomic units corresponding to genera. The genera Leontice and Gymnospermium of Eurasia are pheneticlly equidistant from Caulophyllum, which occurs in eastern Asia and eastern North America. On the basis of phenetic similarity, L. kiangnanensis is transferred to Gymnospermium as G. kiangnanensis.
Simultaneous measurements of tomato fruit and stem water potentials using in situ stem hygrometers
Authors: Lee D. R. , Dixon M. A. , Johnson R. W.
Published: April 2011

Simultaneous measurements were made of the water potentials of the stem and fruit of intact tomato plants (Lycopersicon esculentum Mill. var. Heinz 2653) using in situ temperature-corrected stem psychrometers. Water potential of the fruit remained consistently lower than the water potential of the stem except when the plant had been subjected to prolonged water stress. Stem water potential recovered quickly with rewatering, increasing by approximately 0.5 MPa in 1 h, but the water potential of the fruit remained consistently near −1.0 MPa. The results indicate a significant resistance to water flow between the stem and the fruit and a substantial hydraulic capacitance represented by the volume of the fruit. Diurnal changes in dimensions of tomato fruit were also measured. Fruit diameter expanded at night and contracted during the day even when the water potential gradient favoured flow towards the fruit. This indicates that bidirectional flow (to and from the fruit) is not responsible for the observed diurnal changes in the fruit dimensions.
Physiological specialization of Heterobasidion annosum on conifer hosts
Authors: Hsiang Tom , Edmonds R. L.
Published: April 2011

Eight conifer hosts belonging to five conifer species were inoculated in vitro with conidial suspensions of eight isolates of Heterobasidion annosum from Washington and California. The conifer trees were represented in inoculation tests by 1 cm diameter branch disks of 0.7 cm thickness. The ability of H. annosum to colonize dying woody tissue was assessed in terms of the number of conidiophores produced on the disks, measured 2 to 3 weeks after inoculation. Analysis of variance showed that there was a great range in conidiophore production with most of this variation attributable to host differences rather than to differences between the pathogen isolates. A second analysis involving four Tsuga heterophylla trees and five isolates showed similar results. In both the interspecific analysis with eight trees and the intraspecific analysis with four T. heterophylla trees, there were significant differential interactions between the isolates and the trees. This indicated that physiological specialization exists in this natural disease system at both the host-interspecific and host-intraspecific levels.
Contribution of Azospirillum brasilense Cd to growth of tomato seedlings is not through nitrogen fixation
Authors: Bashan Y. , Singh M. , Levanony H.
Published: April 2011

A wild type and a site-directed mutant strain (Nif−) of Azospirillum brasilense Cd, totally deficient in N2-fixation capability, were used to evaluate if improvement in tomato seedling growth is due to the N2-fixation process. The mutant (Nif−) exhibited several physiological, ecological, and antigenic features similar to the parental strain. When inoculated onto tomato seeds, the significant positive effects of the A. brasilense Nif− on seedling growth under greenhouse conditions in artificial medium were similar to that of the wild-type strain. It is concluded that the contribution of A. brasilense Cd to the improvement of tomato seedling growth is not through N2-fixation.
The frequency and local abundance of Ruppia occidentalis in relation to sediment texture and lake salinity
Authors: Husband Brian C. , Hickman Michael
Published: April 2011

Ruppia occidentalis S. Wats. is a submerged macrophyte often found in saline and subsaline (> 3000 mg ∙ L−1 and 500–3000 mg ∙ L−1 total dissolved solids (TDS), respectively) lakes but rarely in freshwater (< 500 mg ∙ L−1, TDS) in Alberta, Canada. To determine the effect of water salinity on its distribution, we investigated the frequency and local abundance of R. occidentalis in relation to sediment texture within three lakes, having 2165, 1557, and 275 mg ∙ L−1 total dissolved solids. Sediment texture has the largest effect in freshwater and differences among lakes are greatest on the sediment with greatest local abundance. Ruppia occidentalis occurred in 82, 79, and 42%, respectively, of the sites examined within these lakes. This reduction in frequency was associated with a decrease in the diversity of sediment textures in which R. occidentalis occurred. Within the saline lakes, the frequency of R. occidentalis was not dependent on sediment texture. In freshwater, however, R. occidentalis is found primarily on coarse-textured sites. The absence of R. occidentalis from fine-textured sediments, when in freshwater, is not correlated with the abundance of other macrophytes. Local environments associated with coarse sediments, such as low organic content or reduced biotic interactions, are necessary for R. occidentalis to occur in freshwater. However, contrary to the patterns of frequency among sites, local abundance in relation to sediment texture was similar among lakes and least on coarse-textured sediments. Moreover, local abundance was not significantly correlated with lake salinity, except on sandy sites. Therefore, the effects of water salinity on the colonization of new sites, rather than the performance within sites, may be most important in determining the distributional limits of R. occidentalis in central Alberta.
Morphology of Dianthoveus cremnophilus (Cyclanthaceae)
Authors: Wilder George J.
Published: April 2011

Dianthoveus cremnophilus exhibits terminal inflorescences and rhizomes composed of renewal shoots. A rhizome bears two kinds of vegetative buds directly, viz. renewal buds that form renewal shoots and nonrenewal buds that may develop into new rhizomes. Adult leaves consist of sheath, petiole, transition zone, and a bifid lamina that varies from unicostate to subtricostate. The inflorescence axis consists of peduncle and spadix and bears two kinds of spathes, conspicuous and inconspicuous. Seeds exhibit four outer cell layers and become split periclinally throughout the third layer, as well as longitudinally down to this layer, along one edge. Tissue outside the region of splitting may be abscinded; wall ingrowths of the ruptured third layer adhere to, and appear outermost on, the remaining portion of seed, where they directly contact the environment. Seedlings exhibit a primary root, very short hypocotyl, cotyledon, and epicotyl with plumular leaves. Shoots manifest substantial mirror-image symmetry.
Studies in Crataegus (Rosaceae: Maloideae). XX. Interserial hybridization between Crataegus monogyna (series Oxycanthae) and Crataegus punctata (series Punctatae) in southern Ontario
Authors: Wells T. C. , Phipps J. B.
Published: April 2011

Introduced Crataegus monogyna Jacq. and native Crataegus punctata Jacq. are common and distinct species often co-occurring in southern Ontario. Both taxa are diploid obligate outcrossers with overlapping floral phenologies. Putative hybrids between C. monogyna and C. punctata were examined using morphometric analyses, chromatographic comparisons of leaf phenolics, and crossing experiments. These individuals were morphologically and biochemically intermediate in relation to the two parental taxa and were determined to be diploid. In crosses, F1 progeny were formed between C. monogyna and C. punctata, particularly when C. monogyna was the seed parent. The resulting offspring had leaves morphologically intermediate between adult parental and seedling-type material, whereas their chromatographic profiles were comparable to those of the naturally occurring putative hybrids. Based on these data, interserial hybridization between C. monogyna (Oxycanthae) and C. punctata (Punctatae) was confirmed. Postmating barriers are probable and may account for the rare and sporadic occurrence of the hybrids. Seed set in the natural hybrids appeared to be much lower on average than those of the parental species and failed to germinate under controlled conditions.
Capillataspora corticola gen. et sp.nov., a new bitunicate ascomycete from intertidal prop roots of Rhizophora apiculata
Authors: Hyde Kevin D.
Published: April 2011

A new fungus, Capillataspora corticola gen. et sp.nov., from the bark of decaying intertidal prop roots of Rhizophora apiculata Blume, is described. The fungus is illustrated by light micrographs, and its taxonomic placement is considered.
Regulation of ammonia-assimilating enzymes by various nitrogen sources in cultured Ipomoea spp.
Authors: Zink M. W.
Published: April 2011

The levels of ammonia-assimilating enzymes of Ipomoea spp. (morning glory) grown in suspension culture on a chemically defined medium are affected by various nitrogen sources. An increase in nitrate or ammonium concentrations in the growth medium elevated the levels of glutamate dehydrogenase, glutamine synthetase, and glutamate synthase. The levels of the enzymes varied in a manner similar to the growth pattern of the cells. When the growth rate of Ipomoea was maximal, high levels of enzymes were obtained; when cell growth was poor, a low yield of enzymes was obtained. Glutamine, whether used as the sole nitrogen source or as a supplement in media containing ammonium plus nitrate, increased the level of glutamate dehydrogenase and decreased the level of the other two enzymes. The developmental pattern of glutamine synthetase activity with culture age in Ipomoea differed with different nitrogen sources in the growth medium.
Association of phenol-containing structures with Apium graveolens resistance to Fusarium oxysporum f.sp. apii race 2
Authors: Jordan C. M. , Jordan L. S. , Endo R. M.
Published: April 2011

Electron-opaque (EO) structures were studied, using light and electron microscopy, in the xylem parenchyma cells and vessels of both incompatible and compatible Apium graveolens L. var. rapaceum (celeriac) and compatible Apium graveolens L. var. dulce (celery) roots 24 h after inoculation with Fusarium oxysporum f.sp. apii race 2. Few small EO bodies were observed in the noninoculated hosts. Histological, cytochemical, and chemical tests indicated the presence of phenolic substances and polysaccharides in the EO materials. These EO structures increased both in number and size as infection progressed. The incompatible host produced three and five times more of the EO materials than the compatible celeriac and celery, respectively. The amount of the EO materials and host compatibility were related to the absence and presence of fungal hyphae in the vascular system. Hyphae either associated with or enveloped by the EO structures were vacuolated; their cytoplasm was restricted to the cell periphery. Occlusion of the xylem vessel pores of the incompatible host with the EO structures likely prevented upward spread of the pathogen throughout the entire plant.
Epicuticular waxes of the genus Hordeum: a survey of their chemical composition and ultrastructure
Authors: Baum Bernard R. , Tulloch A. Pat , Bailey L. Grant
Published: April 2011

This study was based on 148 accessions representing 39 species of Hordeum. SEM ultrastructural morphology of waxes was based on individual spikelets, whereas waxes' chemical composition was assessed from whole plants. When all the data, in the form of individual accessions, were subjected to various cluster analyses methods, no groupings were revealed. But when the data were first summarized by species and then subjected to clustering, two polythetic groups of species were detected. Group 1 is characterized by species with 40–60% average alcohol content and by the common presence of diketones, whereas group 2 is characterized by species with 61 – 80% average alcohol content, by the total absence of hydroxy-β-diketone, and almost all species without β-diketone. The chemical data were then subjected to classificatory discriminant analysis to assess if a single previously unclassified accession could be identified into one of the two groupings. The nature of the differences between the two groupings was described by means of a canonical discriminant analysis. Mostly only plates and filaments were detected, and in many accessions the filaments were widened, appeared platelike, and were characteristic for one group. Presence of β-diketone varied within species. Hordeum violaceum was found to be unique in chemical composition.
Nectria and Fusarium. 1. Nectria setofusariae and its anamorph Fusarium setosum
Authors: Samuels Gary J. , Nirenberg Helgard
Published: April 2011

The new species Nectria setofusariae and its anamorph Fusarium setosum are described and illustrated. Fusarium setosum is placed in the new section Fusarium sect. Setofusarium. The relationship of Nectria setofusariae to other species of Nectria and Fusarium is discussed.
Effect of photorespiratory inhibitors on in vivo nitrate reduction in the leaves of barley and maize
Authors: Kumar P. A. , Abrol Y. P.
Published: April 2011

The effects of photorespiratory inhibitors, α-hydroxypyridinemethanesulphonate, isonicotinyl hydrazide, and amino-oxyacetate, on in vivo nitrate reduction in the leaves of barley (C3) and maize (C4) were studied. The inhibitors had a pronounced effect on enzyme activity in the leaves of barley but not of maize. Photorespiratory substrates, glycolate and glycine, enhanced nitrate reduction in the leaves of barley. The enhancement was reversed by the inhibitors. It is proposed that glycine oxidation supports nitrate reduction in C3 plants but not in C4 plants.
Homothallism and heterothallism in Tremella fuciformis
Authors: Fox Raymond D. , Wong George J.
Published: April 2011

Nine stocks of Tremella fuciformis were determined to be homothallic or heterothallic. All stocks from Hawaii and the single stock from Panama were homothallic and fruited in single-spore cultures, Heterothallic stocks were obtained from Florida, Louisiana, and New Zealand, and were determined to have a modified bifactorial mating pattern in which two A alleles and multiple B alleles were identified. Among the heterothallic stocks, compatibility was observed between the Louisiana and the Florida stocks and between the Louisiana and the New Zealand stocks. However, the Florida and New Zealand stocks were intersterile and produced only false-clamped mycelia when crossed. Because of the limited number of collections obtained for this study, the basis for intersterility is not known. Key words: bifactorial incompatibility, heterothallism, homothallism, intersterility, Tremella fuciformis.
Survey of enzyme activity on solid media in Phytophthora
Authors: Ann P. J. , Ko W. H.
Published: April 2011

Among 53 isolates of Phytophthora parasitica, Phytophthora palmivora, Phytophthora capsici, and Phytophthora cinnamomi tested, there was no difference in ability to produce lipase, phosphatase, or urea on solid media. However, only some isolates of P. parasitica and P. palmivora produced DNase or pectate transeliminase. The ability to produce pectin depolymerase or amylase varied greatly among isolates of some species. Zoospore progeny of A1 and A2 isolates of P. parasitica tested were relatively uniform and were similar to their parents. However, progeny from oospores produced by the same isolates as a result of hormonal stimulation displayed great variation in their ability to produce amylase. These results support the hypothesis that species of Phytophthora are diploid and indicate that amylase production in P. parasitica is controlled by heterozygous multiple genes.
The relationship between bud scale morphology and indeterminate and determinate growth patterns in Acer (Aceraceae)
Authors: Sakai Satoki
Published: April 2011

Bud scale morphology was investigated for 18 species of Japanese Acer, including 12 species that exhibit indeterminate growth and 6 that exhibit determinate growth. The bud scales of the inner pairs of terminal buds and all bud scales of lateral buds exhibited different patterns of development in the two types of species. In the indeterminate species, the formation of rudimentary laminae was observed, whereas no laminae formation was observed in the determinate species. Loss of laminae could have occurred over the course of the evolutionary specialization of bud scales, since the bud scales of the indeterminate species are assumed to be more primitive than those of the determinate species. A consideration of the bud morphology of Dipteronia, an outgroup of Acer, supported this view. This study then suggests that in Acer a determinate growth pattern actually evolved from a pattern of indeterminate growth. It seems likely that for some member(s) of the genus Acer, sites of regeneration began to shift from sites containing less shady area to those containing more, and that this shift was associated with the evolution from indeterminate to determinate growth.
The fine structure of an algal mat from a freshwater maritime antarctic lake
Authors: Oppenheim Deborah R. , Paterson David M.
Published: April 2011

The three-dimensional microstructure of Tolypothrix mats from the bottom of a maritime antarctic lake of Signy Island, South Orkneys, was examined. Samples from mats at two depths, 4 and 6 m, within the lake were taken by scuba divers and frozen (−80 °C) in March 1987. The samples were freeze-fractured and examined by ambient and low temperature scanning electron microscopy (LTSEM). The mats shared a similar structure consisting of a compact lower zone of prostrate filaments and an upper zone of loose vertical filaments. An outer layer of extremely loose spreading filaments was only found by LTSEM, leading to the conclusion that some collapse of the mat structure occurred during dehydration for ambient SEM. Fine detail of the mat matrix such as the attachment of epiphytes and associated microfauna to the filaments was often obscured by mucilage. Fast-particle etching was used to remove this mucilage and also the organic coat that covers uncleaned diatoms, thereby allowing the identification of attached cells in situ. A variety of attachment strategies were observed although sessile forms were most common. Further fast-particle etching of the epiphytic diatom assemblages revealed that many of the attached diatoms were devoid of cell contents. Together with the epiphytic diatoms a variety of microfauna were identified, both incorporated within the mat and on the mat surface. The implications of these observations are discussed.
Développement des axes des arbres : pousse annuelle, syllepsie et prolepsie chez le Hêtre (Fagus sylvatica)
Authors: Thiébaut B. , Comps B. , Cros E. Teissier du
Published: April 2011

Polycyclic growth is more complex in the European beech (Fagus sylvatica L.) than in other tree species. Growth patterns common to all beeches studied have revealed the existence of annual and intra-annual growth rhythms and a development program peculiar to this species. Syllepsis and prolepsis are discussed in relation to beech. These observations raise new questions: (i) how can we explain a meristematic revertible conversion and (ii) what are the advantages of such a complex mode of development?
Occurrence of cones borne laterally on long shoots of Larix leptolepis
Authors: Powell G. R. , Hancox M. E.
Published: April 2011

Pollen cones borne laterally were observed on many one-season-old long shoots on six Larix leptolepis (Sieb. & Zucc.) Gord. trees 7.5 to 10.4 m tall. The cones occurred proximally on their parent shoots and on the under or side surfaces. They were smaller and developed to maturity more slowly than nearby pollen cones situated terminally on short shoots. The lateral cones were produced in two successive years.
Amino acid activity in the Nelson–Somogyi glucose assay
Authors: Upadhyaya Mahesh K. , Konesky David W.
Published: April 2011

The Nelson–Somogyi assay has been widely used to measure reducing sugars in plant research. We found that the L-amino acids cysteine, cystine, serine, tryptophan, and tyrosine (at 0.1 to 1 mM) react in the Nelson–Somogyi glucose assay, yielding high absorbance values. Alanine, arginine, aspartic acid, glutamic acid, glycine, histidine, hydoxyproline, isoleucine, leucine, lysine, methionine, phenylalanine, proline, threonine, and valine showed little or no effect on color development. Manganese ions strongly inhibited color development in the presence of glucose, serine, cystine, and tryptophan. Investigators measuring glucose in biological materials using this assay must consider the activity of amino acids and (or) the effect of manganese ions in the reaction mixture when interpreting their results. Key words: Nelson–Somogyi assay, sugar analysis, glucose assay, reducing sugar assay.
Identification of taxa of E-strain mycorrhizal fungi by restriction fragment analysis
Authors: Egger K. N. , Fortin J. A.
Published: April 2011

A comparison of cultures of E-strain fungi isolated from mycorrhizal roots and cultures isolated from ascocarps of the teleomorph genus Wilcoxina indicates that the majority of E-strain fungi can be accommodated in two taxa, Wilcoxina mikolae and Wilcoxina rehmii. Comparisons were based upon restriction fragment polymorphisms within the nuclear ribosomal RNA genes (rDNA) and culture morphology (color, growth rate, vegetative spore production). Restriction fragment patterns were quite consistent within taxa, although there was variation that appeared to be due to differences in length of the intergenic spacer. Morphological characters were less reliable for identifying taxa, with growth rate and color showing considerable variation among isolates on different growth media. The presence of terminal chlamydospores was consistently associated with W. mikolae isolates from pine but is not diagnostic of this taxon for isolates from spruce. Key words: E-strain, Wilcoxina, mycorrhiza, ribosomal DNA, restriction fragment length polymorphism.
Evolutionary relationships of Douglas-fir and its relatives (genus Pseudotsuga) from DNA restriction fragment analysis
Authors: Strauss Steven H. , Doerksen Allan H. , Byrne Joyce R.
Published: April 2011

We used restriction fragment analysis of chloroplast, nuclear, and mitochondrial DNA to study phylogeny in the genus Pseudotsuga. Total genomic DNA from one outgroup (Larix occidentalis Nutt.) and five Pseudotsuga species from Japan, mainland China, Taiwan, and North America were digested with 20 restriction enzymes, blotted, and probed up to 17 times with cloned DNA fragments. A total of 38 shared fragment characters were subjected to Wagner parsimony analysis coupled with bootstrapping to evaluate statistical significance of the phylogenetic trees. The complex patterns that we observed for actin gene fragments were evaluated via a Fitch–Margoliash distance-matrix analysis. Both parsimony and distance-matrix analyses indicated that relationships among species in the genus coincide with their current geographic distribution; genetic similarity declines with migration distance around the Pacific Rim. The Asian and North American species form well-differentiated and statistically significant monophyletic groups. Pseudotsuga japonica is the Asian species closest to the North American species. Affinities to the outgroup Larix occidentalis suggest that Pseudotsuga originated in North America and then migrated into Asia. Key words: parsimony, phylogeny, biogeography, conifer, Pinaceae.
Dépérissement, déficit hydrique et variations de croissance radiale chez le Picea abies
Authors: Badot P. M. , Perrier P. , Badot M. J.
Published: April 2011

Changes in the water status of spruce needles have been studied in relation with the present dieback disease of forests in the French Jura. A study of the variation in width of annual rings has been conducted to evaluate if radial growth was disturbed during forest decline. The water content of the needles displayed great individual variability, but at the population level, variation in water content was closely correlated to the health status of the trees: at the same age, the needles of the damaged trees showed lower water content than those of the healthy ones. A mean diameter growth index was used to take into account the effect of ageing of the trees on diameter growth. Globally, this index increased during the past century: such a result indicates that the vigour of the spruce populations had not been altered since the beginning of the century. The healthy and diseased trees displayed the same variation in the mean growth index until 1949. Then, the affected spruces had annual increments lower than those of the healthy trees during two periods, from 1949 to 1959 and from 1973 to 1987. These growth crises correspond to periods with a pronounced rainfall deficit, which often included one or several years of severe drought. Thus, poor water supply could play a role in the present decline of spruce in the French Jura. Key words: radial growth, forest decline, tree-ring width, drought, water content.
Seimatosporium rossicum anam.-sp.nov.
Authors: Raj T. R. Nag , Mel'nik V.
Published: April 2011

A new anamorph-species in Seimatosporium Corda is described from the Soviet Far East. Key words: Seimatosporium rossicum, Rhododendron sichotense.
Effect of ochratoxin A on aflatoxin production by Aspergillus parasiticus
Authors: Serafini M. , Foddai S. , Pieretti S. , Tomassini L. , Nicoletti M.
Published: April 2011

The effect of ochratoxin A on growth and aflatoxin production by Aspergillus parasiticus was investigated. High concentrations had a significant effect, causing stimulation of aflatoxin production. Key words: Aspergillus parasiticus, aflatoxin production, ochratoxin A.
Cytodifferentiation during the development of friable embryogenic callus of maize (Zea mays)
Authors: Fransz P. F. , Schel J. H. N.
Published: April 2011

Immature embryos of Zea mays L. were cultured on N6 medium to obtain embryogenie callus. Cultured tissue fragments with various developmental stages of friable callus were sampled and prepared for light microscopy and transmission electron microscopy. Pieces of compact callus were also prepared for light microscopy to compare the structural organization of both callus types. Friable callus develops from a thin layer of abaxial scutellum cells, including the epidermis. During further development the callus cells dissociate, owing to the breakdown of the middle lamellae, while older vacuolated cells degenerate. This results into long cell aggregates separated by large intercellular spaces, giving the callus its friable appearance. The microscopical sections showed a striking difference between friable and compact callus. Vascular elements were not found in the friable callus. On the contrary, vascular bundles were prominent in compact callus. Friable callus is therefore correlated with a less differentiated state than compact callus. The embryogenic potential of friable callus is situated in embryogenic units. These are aggregates of small isodiametric cells containing a central nucleus, an electron-dense cytoplasm, and many organelles. Proliferation was only observed in these cells, which are therefore presumed to generate new embryogenic units, somatic embryos, and vacuolated callus cells. The results further indicate that discrete masses of embryogenic cells, possibly early embryoids, have a unicellular origin. Key words: in vitro culture, callus, somatic embryogenesis, ultrastructure, Zea mays.
Implications of phenotypic plasticity for numerical taxonomy of Ornithogalum montanum (Liliaceae)
Authors: Pigliucci M. , Politi M. G. , Bellincampi D.
Published: April 2011

Implications of phenotypic plasticity in a subspecific numerical taxonomic study of Ornithogalum montanum Cyr. (Liliaceae) are discussed. Clones belonging to six natural populations were grown in a glasshouse, and their morphological response to three water dosages was analyzed by means of principal component analysis. PC-1 ranks the three groups of replicated populations, suggesting a high degree of phenotypic plasticity; on the other hand, PC-3 is almost environmentally independent. Proximities in the phenetic space are shown to be at least partially environmentally dependent, suggesting a reaction norm for the character correlation matrix. The results do not corroborate a previous recognition of six subspecies of O. montanum. Key words: phenotypic plasticity, numerical taxonomy, Ornithogalum, reaction norm, principal component analysis.
Tissue response induced by Heterodera schachtii (Nematoda) in susceptible and resistant white mustard cultivars
Authors: Golinowski Władysław , Magnusson Christer
Published: April 2011

The anatomy and ultrastructure of syncytia induced in white mustard (Sinapis alba L.) by the beet cyst nematode (Heterodera schachtii Schmidt) were studied in the nematode-susceptible cultivar Trico and the nematode-resistant cultivar Maxi. Although syncytia in both cultivars could reach similar volumes, they differed considerably in their ultrastructure. In the susceptible cultivar, xylem parenchyma cells responded with extensive hypertrophy, an increase in plastids and tubular smooth endoplasmic reticulum, and formation of elaborate ingrowths of the cell walls abutting the xylem tracheary elements. In the resistant cultivar, xylem parenchyma cells, occasionally incorporated into the syncytium, necrotized. Normally, however, these cells resisted incorporation and stopped the syncytia from reaching the xylem tracheary elements. This resulted in the differentiation of cell wall ingrowths on the inner tangential walls of neighbouring stelar parenchyma cells. The improper coordination of syncytium differentiation with xylem morphogenesis, the malfunction in the symplast–apoplast interaction with an abnormal deposition of protoplasmic constituents into the apoplast, the small number of plastids, the lack of tubular smooth ER and degradation processes, further demonstrated the incompatible nature of the host–parasite interaction in the resistant cultivar Maxi. Key words: Sinapis alba, Heterodera schachtii, ultrastructure, resistance.
Ultrastructure of the developing embryo sac of sunflower (Helianthus annuus) before and after fertilization
Authors: Yan Hua , Yang Hong-Yuan , Jensen William A.
Published: April 2011

The ultrastructure of the embryo sac of the sunflower (Helianthus annuus) was investigated before and after fertilization. In the young embryo sac, walls were observed that completely surrounded the egg, synergids, and the central cell. However, as maturation continued, the extent of the wall changed. By the time the embryo was mature, the chalazal portion of the walls of the egg and synergids had disappeared so these cells have a plasma membrane to plasma membrane contact. This is also true for the central cell, which has plasma membrane contact with the egg and synergids. However, the chalazal and lateral walls of the central cell become considerably thicker at this time. Before the entry of the pollen tube, the synergid that is located toward the placenta degenerates. After fertilization, a wall forms over the chalazal portion of the zygote and the persistent synergid. The endosperm appears to play an active role in this process, contributing substantial amounts of wall material. However, the wall covering the chalazal portion of the zygote is not complete by the time the zygote divides. In the proembryo, ribosome density increases and lipid bodies decrease in number. The suspensory cell has autophagic vacuoles that encircle some of the organelles. Our results support the concept that the egg, synergids, and central cell form a single functional unit, the female germ unit. Key words: sunflower, ultrastructure, embryo sac, female germ unit.
Adaptations of root structure in relation to biotic and abiotic factors
Authors: Peterson R. L.
Published: April 2011

Roots are discussed less frequently than other plant organs in terms of their phylogenetic origin and evolutionary specialization because of limited paleobotanical information and few broad comparative studies of root structure and development. There is considerable diversity, however, in root structure among the major groups of vascular plants. Roots of many extinct and extant seedless vascular plants have a simple apical meristem (i.e., an apical cell), limited secondary growth, and in some genera, branching is accomplished by a true dichotomy of the apical meristem. Roots of seed plants evolved more complex apical meristems, branching from subterminal tissues, and in some groups extensive vascular cambium activity. Evolutionary developments related to nutrient availability include symbiotic interactions with soil fungi to form mycorrhizae, soil bacteria and cyanobacteria to form nitrogen-fixing nodules, and the modification of branching to form cluster roots. Concomitant with these specializations, root hair frequency and structure are often modified. All roots possess a suberized layer, the endodermis, and in many species, particularly among the angiosperms, a specialized suberized exodermis is present. Roots of aquatic species have evolved mechanisms either to tolerate or to avoid anaerobiosis. Roots growing in continuously wet environments possess constitutive aerenchyma whereas roots of periodically flooded plants are able to respond by forming lysigenous or schizogenous aerenchyma. Key words: roots, evolution, adaptations, structure, symbioses.
Precise flagellar configuration of the Rhizophlyctis harderi zoospore
Authors: Roychoudhury Sonali , Powell Martha J.
Published: April 2011

Rhizophlyctis harder is a questionable member of the genus Rhizophlyctis, and more stable and reliable characters are needed to establish the taxonomic position of this chytrid. As a source of such characters the flagellar apparatus of zoospores of R. harderi was reconstructed from serial sections, and the precise configuration was determined. The flagellar apparatus included two major microtubular roots, each with separate points of origin near the kinetosome. Root A extended laterally from one side of the kinetosome toward and around one rumposome and then continued anteriorly. The other, root B, originated between the kinetosome and secondary centriole near fibrillar connecting material and projected anteriorly into the cytoplasm. Each of these two major roots branched into two rootlets. This system of microtubular roots is more complex than that found in the flagellar apparatus of other Chytridiomycetes presently described. The structure of the flagellar apparatus and accompanying roots clearly separates this species from others in the genus Rhizophlyctis and indicates that it can be used to establish a new genus in the Chytridiales. Key words: Rhizophlyctis harderi, Chytridiales, zoospores, flagellar apparatus, ultrastructure.
Phosphatase activities and phosphorus uptake from inositol phosphate by ectomycorrhizal fungi
Authors: Antibus Robert K. , Sinsabaugh Robert L. , Linkins Arthur E.
Published: April 2011

To better understand the physiological importance of acid phosphatase activity we examined the effects of inorganic and organic phosphorus growth sources on enzyme activity and 32P uptake in several ectomycorrhizal fungi. Mycelium of eight isolates from four basidiomycete species demonstrated optimal p-nitrophenyl phosphatase activity at pH 4.5 or 5.0. Acid phosphatase activities varied between strains of Scleroderma citrinum and between the species examined. Interspecific differences in isozyme patterns of whole cell extracts were apparent in native polyacrylamide gels. The isoelectric points of the predominant phosphatases in whole cell extracts were in the pH 5.0 to 5.5 range. Growth of fungi on inositol hexaphosphate versus inorganic P did not affect the isozyme patterns detected by either electrophoretic method. Growth on inositol hexaphosphate affected surface and soluble activities towards p-nitrophenyl phosphate and inositol phosphate to different degrees in species examined. Phytase activity was sufficient to produce a net release of P in all isolates. Growth on inositol hexaphosphate was associated with increased uptake of 32P from inositol polyphosphate in four of five species examined. Acid phosphatase, measured with p-nitrophenyl phosphate, was positively correlated with 32P uptake. Decreased phytase activities measured for inositol hexaphosphate grown mycelium were associated with increased P influx in such mycelium. Both phosphatase activity and 32P uptake were subject to inorganic P inhibition with 32P uptake demonstrating a greater sensitivity. These results provide further evidence for the role of surface acid phosphatases in organic P utilization by ectomycorrhizal fungi. Key words: acid phosphatase, ectomycorrhizal fungi, phytase.
Distribution patterns and interthalline interactions of epiphytic foliose lichens
Authors: John Elizabeth
Published: April 2011

The foliose lichens of a corticolous epiphyte community were sampled using a grid of points and nearest neighbour sampling. Most species were found to have nonrandom distributions with respect to height and aspect on the tree trunk. The tendency of species to form exclusive patches and to contact other species showed large interspecific differences. Some formed monocultures and had fewer interspecific contacts than expected, while others did not form large patches and had more interspecific contacts than expected. Investigation of interspecific thallus overlaps revealed a hierarchy in which heavier species such as Flavoparmelia caperata (2.3 mg/mm2) overtop lighter ones such as Melanelia subaurifera (1.1 mg/mm2) more often than the converse is true. It is likely that being overtopped by another lichen puts a thallus at a disadvantage in competition for resources. The success of a species at overtopping another does not change according to location on the tree trunk. There was evidence that F. caperata excluded other species during succession. Key words: epiphytes, foliose lichens, thallus overlaps, interspecific competition, ecological strategies.
Germination and development of attachment structures by conidia of aquatic Hyphomycetes: light microscope studies
Authors: Read S. J. , Moss S. T. , Jones E. B. G.
Published: April 2011

The time scales of conidial germination and production of postgermination attachment structures in species of the aquatic Hyphomycetes were investigated. The conidia of most species germinated within 2 h and formed appressoria within 6 h of settlement. Subsequent to settlement, appressoria were formed by all of the tetraradiate and branched conidia at the poles of the conidial arms. It is suggested that appressorium formation is an adaptation to aid fungal attachment to a substratum. Conidial germination was not influenced by the substratum; however, appressoria were both more numerous and more complex on a glass substratum. Mucilage was present on conidia, and mucilaginous sheaths were frequently observed to be associated with germ tubes and appressoria. The majority of species produced mucilages composed primarily of polysaccharide(s) with neutral or carboxyl functional groups. Key words: aquatic Hyphomycetes, germination, appressorium, attachment, settlement.