bluuebunny/crossref_metadata_2025 huggingface dataset:
Cyanide-resistant respiration in isolated Asparagus mesophyll cells
Authors: Shadeed Nancy M. , Bown Alan W.
Published: September 2008

The inhibitors of oxidative phosphorylation antimycin A (0.5 μg/mL), oligomycin (0.01 mg/mL), and sodium azide (3 mM) eliminated energy-dependent H+ efflux from isolated Asparagus mesophyll cells. Antimycin A and oligomycin also reduced ATP levels by 60% or more. In contrast the same concentrations of inhibitors had little or no effect on respiratory O2 consumption. The sequential addition of potassium cyanide to give a final concentration of 5.2 μM resulted in a 60% maximum inhibition of O2 consumption. Subsequent addition of 0.2 mM disulfiram (tetraethylthiuram disulfide), a potent inhibitor of cyanide-resistant respiration, resulted in a further reduction of the oxygen consumption rate. In the absence of cyanide, 0.2 mM disulfiram inhibited O2 consumption by 40 to 80%, depending on the suspension medium. Disulfiram had little or no effect on the ATP levels which varied between 0.7 and 2.2 nmol ATP/106 cells. The results indicate that disulfiram inhibits a non-energy-conserving cyanide-resistant alternative pathway in Asparagus mesophyll cells.
Leaf development in the anisophyllous shoots of Pellionia daveauana (Urticaceae)
Authors: Mueller Petra A. , Dengler Nancy G.
Published: September 2008

The dorsiventral shoot system of Pellionia daveauana (Godefr.) N.E. Br. is characterized by opposite pairs of dimorphic leaves. The small dorsal leaves differ from the large ventral leaves by having a reduced leaf blade, fewer tissue layers in the epidermis and mesophyll, a reduced vascular system and significantly smaller cell size in all tissue layers. The observations reported here document the developmental basis of these morphological and histological differences. Although both dorsal and ventral leaves appear to be initiated simultaneously, the volume of the ventral leaf primordium is greater than that of the dorsal leaf primordium and growth in length occurs over a longer time period. Early plate meristem activity results in the elaboration of the ventral leaf blade, while plate meristem activity is lacking in dorsal leaves. During ventral leaf expansion periclinal divisions in adaxial and abaxial protoderm and ground meristem give rise to multiple epidermis and new mesophyll layers, respectively. Similar periclinal divisions in dorsal leaves occur at an earlier developmental stage and are restricted in extent. Measurements of cell dimensions show that cell enlargement also ceases at an early developmental stage in dorsal leaves. Development of the ventral leaf is characterized by a relatively long period of cell division and enlargement. In contrast, early cessation of cell division and precocious cell maturation result in the distinctive structural features of the dorsal leaf blade.
Cytological variation in zoospores of Spizellomyces (Chytridiomycetes)
Authors: Barr Donald J. S.
Published: September 2008

The principal cytological features and their variations are described in zoospores of 38 isolates belonging to seven species of Spizellomyces. This genus is distinguished from others in the Spizellomycetaceae by the orientation of the microtubules and the position of the nucleus relative to the kinetosome in the zoospore. Microtubules run apparently at random into the cytoplasm from a microtubule-organizing center (spur) on one side of the kinetosome. The nucleus is anteriorly or centrally positioned with a heel-like process extending to near the proximal face of the kinetosome, or it can be posteriorly positioned and elongate with one end close to the kinetosome. Differences between species are reflected by the position and shape of the nucleus, the extent of the endoplasmic reticulum which in some species circumscribes lipid globules, the presence or absence of an apparent connection by fibrillar material between the kinetosome and a nonfunctional centriole, and the morphology of the microtubule-organizing center. The zoospores of Spizellomyces punctatus (Koch) D. Barr, S. plurigibbosus (D. Barr) D. Barr, and S. palustris (Gaertner) D. Barr are cytologically similar, but those of S. acuminatus (D. Barr) D. Barr, S. dolichospermus D. Barr, S. lactosolyticus D. Barr and S. pseudodichotomus (Umphlett) D. Barr each have one or more distinctive characteristic. Spizellomyces dolichospermus and S. pseudodichotomus also have some cytological characteristics in common with the genus Kochiomyces.
The genetics of pathogenic aggressiveness in three dikaryons of Ustilago hordei
Authors: Caten C. E. , Person C. , Groth J. V. , Dhahi S. J.
Published: September 2008

The genetic determination of a quantitative component of pathogenicity, aggressiveness, was examined in progeny populations derived from three parent dikaryons of Ustilago hordei. Aggressiveness was assessed as the proportion of smutted plants produced from inoculated seed of a compatible barley cultivar. The parents differed in their origins and cultural histories and this was reflected in the variability of their progenies. A standard race-10 strain appeared to be homozygous for genes affecting aggressiveness, while a dikaryon produced by mating two unrelated sporidia was heterozygous and produced highly variable progeny populations. In these populations, aggressiveness was determined by a polygenic system which involved both additive and dominance gene effects. It was not possible to estimate the number of genes involved, but segregation was apparent in individual tetrads. Furthermore, a difference between opposite mating-type segregants suggested the presence of a factor which affected aggressiveness and was linked to mating type. The dominance effects were ambidirectional suggesting that genotypes giving an intermediate level of aggressiveness are the most fit. The aggressiveness of a pathogen strain is an important factor determining the severity of epidemics on compatible hosts. It is also a major component of fitness and may influence the frequency of virulence factors in pathogen populations and the evolution of new races.
Interactive effect of ammonia and pH on viability and 14C-labeled exudation from fungal propagules
Authors: Chun D. , Filonow A. B. , Lockwood J. L.
Published: September 2008

The effect of ammonia on exudation and viability of 14C-labeled propagules of Cochliobolus victoriae, Cochliobolus sativus, and Macrophomina phaseolina was studied in a model fungistatic system with nutrient-independent or nutrient-dependent propagules or in soil amended with urea from which ammonia was generated. In soil, ammonia stimulated exudation of 14C-labeled compounds, but their metabolism by the soil microbiota was suppressed. Short-term exposures of a few hours in a model fungistatic system with high free ammonia concentrations (up to 10 000 mg/L) stimulated a burst of exudation which was usually associated with death of the propagules. Lower concentrations increased exudation less, but exudation tended to be maintained at a level greater than that in nontreated controls. Viability was reduced when the propagules were continuously exposed to long-term doses which were nonlethal for shorter durations. High pH by itself increased exudation, but it did not account for the greater exudation effected by ammonia, nor for its lethal effects. In a fixed-volume system, which imposed low nutrient stress, ammonia (10–100 mg/L) had a sparing effect on the increased exudation brought on by high pH alone; as ammonia concentration was increased (100–1000 mg/L), the sparing effect was lost and exudation increased, accompanied by decreased viability.
Le contenu en ADN nucléaire des bourgeons latéraux actifs, inhibés et en cours de réactivation chez le Polypodium vulgare
Authors: Michaux-Ferriere N.
Published: September 2008

Relative DNA contents of active, inhibited, or reactivated buds of Polypodium vulgare L. were determined by staining the nuclei with the Feulgen reagent and measuring their optical density with a microspectrophotometer; from the obtained data, percentages of nuclei in G1 or G2 phase were calculated. In active buds, the majority of cells of the axial zone were in G2 phase and cells of the lateral zone were essentially in G1 phase. In inhibited buds, nuclei of the axial zone were blocked in G2 phase as were the greatest number of the nuclei of the lateral zone. The 6-benzylaminopurine (6-BAP) treated axillary buds exhibited the same evolution with 24 h of delay as those reactivated by decapitation of the terminal bud. Cells arrested in G2 phase passed synchronously through M and then G1. The reactivation cell cycle was peculiar; it was not in agreement with that of a normal active cell. These data point out the great peculiarity of Pteridophytes compared with what it is known about apical dominance in Angiosperms.
Geographic variation in the pollen of Silene latifolia (S. alba, S. pratensis): a quantitative morphological analysis of population data
Authors: Prentice H. C. , Mastenbroek O. , Berendsen W. , Hogeweg P.
Published: September 2008

There is a geographic separation of the two pollen morphs in European Silene latifolia, with the changeover zone running northwest – southeast from the Netherlands to Greece. Reticulate grains are characteristic of western populations and microechinate grains are characteristic of eastern populations. The present study is based on a sample of one pollen grain from each of the male individuals from each of 32 greenhouse-grown populations representing the distribution of S. latifolia across Europe. The 316 grains were scored for 11 morphological characters (61 character states) under the light microscope. Population character-state frequencies were analysed using cluster analysis and principal components analysis. The results support the geographic distribution of pollen morphs, but the populations with the typical eastern and western morphs are linked by a belt of populations with intermediate pollen morphology. Intermediate pollen is characteristic of populations in a zone from Belgium to Italy; the zone represents a region of relatively rapid morphological change and is coincident with a similar zone of change in seed and flavonoid characters in S. latifolia. Scanning electron micrographs from each population provided further information on the pollen morphology and complemented the light microscopical observations. The variation pattern is illustrated by scanning electron micrographs from selected populations.
Leaf conductance responses of Viola species from sun and shade habitats
Authors: Curtis William F. , Kincaid Dwight T.
Published: September 2008

The diurnal pattern of leaf conductance was measured extensively for two Viola species from New England forest and meadow habitats throughout the growing season. The amount of light available to the two species constituted the major micrometeorological difference between their habitats. In the forest, light intensity was highly variable and composed of low-intensity, foliage-filtered light with brief, periodic bursts of high-intensity sun flecks. These contributed less than 25% of total photosynthetically active radiation reaching the forest floor. Comparatively unobstructed, high-intensity light was measured at the meadow site. The forest canopy also buffered air temperature to a greater extent than the grass and shrub vegetation in the meadow, although leaf temperatures in the forest increased briefly during sun flecks. High morning conductance values decreased during the day, perhaps in response to increasing heat load (meadow species) or decreasing light levels (forest species) during the late afternoon. A greater amount of intraspecific variation in leaf conductance was detected for the forest species than for the meadow species. No water stress was observed for either species.
Photosynthetic potential of sun and shade Viola species
Authors: Curtis William F.
Published: September 2008

The photosynthetic responses of a forest floor violet (Viola blanda) and a related meadow species (Viola flmbriatula) grown under controlled conditions were measured to test the prediction that these two species were photosynthetically shade and sun adapted, respectively. Based on their low photosynthetic and dark respiration rates, and low light saturation and compensation points, both violets can be classified as shade-tolerant. The forest species was photosynthetically and morphologically inflexible when grown under high light conditions, which led to chlorosis and greatly decreased photosynthetic performance. Conversely, the meadow species was both photosynthetically and morphologically flexible; its photosynthetic performance allowed it to grow well under both high and low light regimes. As a consequence, morphological flexibility may play a greater role than physiological (i.e., photosynthetic) plasticity in regulating the distribution of these two violets under field conditions.
The effect of pollination intensity and incompatible pollen on seed set in Turnera ulmifolia (Turneraceae)
Authors: Shore Joel S. , Barrett Spencer C. H.
Published: September 2008

Controlled pollination experiments were performed on the self-incompatible distylous herb Turnera ulmifolia L. to investigate the effects of pollination intensity and large amounts of incompatible pollen on seed set. In the first experiment, known numbers of compatible pollen grains ranging from 1 to 100 were applied to stigmas of the floral morphs. In both morphs, increasing amounts of pollen generally resulted in increased levels of seed set, although considerable variance was observed at all pollination intensities. Approximately two to seven pollen grains are required to produce a single seed and more than 95 grains are required to achieve maximum seed set in T. ulmifolia. Regression analysis of the seed set data failed to detect a difference in the response of the floral morphs to pollination intensity. In the second experiment, known proportions of compatible and incompatible pollen were applied to stigmas at various time intervals. Most treatments involving mixtures of compatible and incompatible pollen had no significant effect on seed set when compared with the controls. Clogging was only observed in the long-styled morph when one anther of compatible pollen was applied to stigmas 1.5 and 3.0 h after pollination with five anthers of incompatible pollen. The clogging of stigmas by incompatible pollen seems unlikely to have played a major role in the evolution and maintenance of distyly in Turnera ulmifolia.
Copper and nickel tolerance in Typha latifolia clones from contaminated and uncontaminated environments
Authors: Taylor Gregory J. , Crowder A. A.
Published: September 2008

Plants of Typha latifolia L. derived from overwintering rootstocks collected from a site contaminated with copper and nickel and an uncontaminated control location were maintained in the laboratory for a minimum of three vegetative generations. Uptake of copper and nickel by both clones from contaminated nutrient solutions was greater than from control solutions. Growth of both clones was inhibited by 100 μg g−1 Cu–EDTA, and 600 μg g−1 Ni–EDTA. Evidence suggesting that copper and nickel tolerance has evolved in the population from the contaminated site could not be detected. Indeed clones from the uncontaminated site showed greater growth under copper stress than clones from the contaminated site, while growth of both clones was equally depressed under conditions of nickel stress.
The development of cotyledon and shoot apex in monocotyledons
Authors: Guignard J.-L.
Published: September 2008

Monocotyledonous embryos have a single cotyledon which is initiated very early. During development the differential growth in the cotyledon results in a lateral shoot apical meristem; its quiescent central zone, at first axial as in Palmae, becomes more lateral in the course of evolution owing to earlier development of the cotyledon. One can establish a phyletic sequence from a dicotyledonous embryo to an advanced monocotyledonous embryo through the Palmae.
Development of tensile strength in conventional and approach grafts in Sedum telephoides
Authors: Moore Randy
Published: September 2008

Conventional autografts between severed internodes of Sedum telephoides attained a tensile strength of approximately 75 g breaking weight (BW)/mm2 graft area (GA) by 20 days after grafting. Approach grafts between cut surfaces were characterized by a tensile strength of approximately 42 g BW/mm2 GA by 10 days after grafting. Approach grafts in which membrane filters were inserted between the grafting surfaces attained a tensile strength of approximately 10 g BW/mm2 GA by 5 days after grafting. These results indicate that the cell wall deposition responsible for the initial cohesion of the stock and scion contributes approximately 13% of the tensile strength of the graft union in compatible Sedum autografts. Similarly, the interdigitation of callus cells and vascular redifferentiation (and the relatively small amount of wall deposition associated with each) contribute approximately 44 and 43%, respectively, to the tensile strength of the Sedum graft union. The data suggest synergistic interaction between different mechanisms of graft formation.
A contribution to the taxonomy of the Carex macloviana aggregate (Cyperaceae) in western Canada and Alaska
Authors: Whitkus Richard , Packer John G.
Published: September 2008

The Carex macloviana aggregate consists of several phenetically similar taxa in western Canada and Alaska. Small morphological differences among the taxa have led to treatments recognizing either one more inclusive or six less inclusive species. A detailed morphotaxonomic investigation was initiated to delimit species and describe phenetic relationships among them. Results from study of herbarium specimens from the entire geographic range of each taxon and various numerical analyses of Canadian and Alaskan material indicate the taxa C. microptera Mack., C. festivella Mack., and C. limnophila Hermann comprise one species; C. haydeniana Olney is another species, phenetically similar to the first, and C. macloviana D'Urv. and C. pachystachya Cham. ex Steud. are two similar but distinct species. The species were also determined to have different chromosome numbers, geographic distributions, and ecological preferences. A previously unrecognized group of specimens, designated "stubby," was recognized and included in all the analyses to determine its phenetic position within the aggregate. It is concluded that "stubby" represents an extreme form of the variable C. pachystachya.
Induction of plantlets in axenically cultivated rhizoids of Fucus spiralis
Authors: Fries Lisbeth
Published: September 2008

Rhizoids of Fucus spiralis were cultivated axenically in the artificial seawater ASP6 F2. Experiments were made to increase the filamental growth as well as to induce adventive primordia (plantlets). Additions of such carbon compounds as glucose, acetate, and formate had no favourable effects even in concentrations as low as 1∙10−4 M. Mannitol killed the rhizoids in higher concentrations and inhibited growth even in a concentration as low as 1∙10−5 M. Higher concentrations of glycerol also inhibited growth, but 1∙10−4 M was an exception as it initiated plantlets. Many simple phenolic compounds induced plantlets. Among the most active substances were phenylacetic acid, p-hydroxyphenylacetic acid, 3,4-dihydroxybenzoic acid, o-hydroxybenzoic acid, and o-acetoxybenzoic acid, with optimal effects in the concentration range of 1∙10−7 to 1∙10−6 M. β-Indolylacetic acid strongly influenced the dry weight as well as plantlet formation at concentrations of 1∙10−8 to 1∙10−7 M, with 1∙10−8 M favouring plantlet induction. It is obvious that β-indolylacetic acid plays an important role in the earlier stages of the development of Fucus.
Ontogeny of somatic embryos of Pennisetum americanum. II. In cultured immature inflorescences
Authors: Botti Claudia , Vasil Indra K.
Published: September 2008

Embryogenic callus was induced from young, unemerged inflorescences of Pennisetum americanum cultured on Murashige and Skoog's medium supplemented with different concentrations of 2,4-dichlorophenoxyacetic acid (2,4-D). The amount and quality of the embryogénie callus and the rapidity with which it was formed depended on the age of the explant and the concentration of 2,4-D. Best results were obtained from explants with floral primordia at the earliest stages of development and with 2.5 mg/L 2,4-D. The compact, embryogenic callus originated from the floral primordia. Subsequent differentiation of the callus led to the formation of subepidermal layers of embryogenic cells. These richly cytoplasmic cells contained numerous starch grains. Increase in cell wall thickness, cell separation, and a sequence of internal segmenting divisions in single embryogenic cells led to the formation of embryoids.
The flavonoids of Lithophragma (Saxifragaceae)
Authors: Nicholls K. W. , Bohm B. A.
Published: September 2008

Flavonoid profiles have been determined for all nine species of Lithophragma recognized by R. L. Taylor. Kaempferol, quercetin, isorhamnetin, and myricetin occurred in various combinations of 3-mono-, 3-di-, and 3-tri-glycosides, 3,7-diglycosides, and 7-monoglycosides although not all taxa had all such derivatives. The dihydrochalcone glucoside phloridzin was found in three populations of L. affine (of 18 examined) which marks the first report of this flavonoid type in the family. Other than the variation in phloridzin occurrence, flavonoid patterns were homogeneous within species. Each species exhibited a unique pattern of flavonol glycosides. Flavonoid data agree with Taylor's grouping together of L. parviflorum and L. trifoliatum and their close similarity to L. affine, and the placement of L. Cymbalaria in its own group. Flavonoid data do not, however, support the view that L. glaborum and L. tenellum are closely related, or that L. campanulatum may have arisen through hybridization between taxa similar to L. Bolanderi and L. heterophyllum.
Ethylene production and morphological adaptation of woody plants to flooding
Authors: Tang Z. C. , Kozlowski T. T.
Published: September 2008

Seedlings of Ulmus americana, Fraxinus pennsylvanica, Melaleuca quinquenervia, and Eucalyptus camaldulensis exhibited greater morphological adaptation to flooding than did Eucalyptus globulus or Pinus halepensis seedlings. Formation of hypertrophied lenticels and production of adventitious roots on submerged portions of stems were characteristic of the flood-tolerant species only. Ethylene production was greatly stimulated by the flooding of all species except P. halepensis. In flooded F. pennsylvanica seedlings ethylene production was higher in stems with well-developed hypertrophy than in those without stem hypertrophy. Lack of a vertical gradient in ethylene content of the stems of flooded Eucalyptus plants indicated either that waterlogging of soil indirectly stimulated ethylene production in stems above the waterline or that ethylene was translocated upward from submerged portions of stems. Application of indoleacetic acid stimulated ethylene producton in submerged portions of M. quinquenervia and U. americana stems. The data indicate an important role for ethylene in the morphological adaptation of woody plants to flooding. The additional involvement of several other compounds in such adaptation is discussed.
Effects of temperature and tissue age on gel strength and composition of agar from Gracilaria tikvahiae (Rhodophyceae)
Authors: Craigie James S. , Wen Zong C.
Published: September 2008

Agars were prepared from a wild type and two morphological mutants of Gracilaria tikvahiae grown at 17, 22, and 27 °C, and from apical segments, main axis segments, and lateral branches of the wild type clone MP-2 grown at 17 and 27 °C. The yield of native agar was 9–11% from the young parts and 19–23% from the most mature parts of the MP-2 thallus. The gel strengths of alkali-modified agars showed a strong inverse relationship with increasing temperature of growth in each of the three clones examined. The modified agar produced from plants grown at high temperature contained more sulfate and less 3,6-anhydro-L-galactose than agars produced at lower temperatures. The increase in 4-O-methyl-L-galactose content of the agars as the growth temperature increased was especially marked. Dissection experiments on clone MP-2 showed that agar with the maximum gel strength and 3,6-anhydro-L-galactose content and the minimum sulfate and 4-O-methyl-L-galactose content was produced at low temperature by apical segments and young lateral branches. The poorest quality agar was prepared from mature segments of the thallus, especially those grown at high temperatures. Agars prepared from mature parts of the thallus were greatly enriched in 4-O-methyl-L-galactose, which reached 8.8% of the weight of the agar at 27 °C. Changes in 6-O-methyl-D-galactose were smaller, but this sugar was lowest in agar prepared from young tissues of plants grown at 17 °C.
A comparative study of the insoluble storage proteins and the lectins of seeds of the Euphorbiaceae
Authors: Lalonde Louise , Fountain David W. , Kermode Allison , Ouellette Francis B. , Scott Kelly , Bewley J. Derek , Gifford David J.
Published: September 2008

The major storage protein within seeds of the Euphorbiaceae is the 11S crystalloid, which is only completely soluble in buffer or salt solutions if sodium dodecylsulphate or urea is present. Prior to this study, only the storage proteins of the castor bean had been characterized. The nonreduced crystalloid protein complex in all species tested has a molecular weight of 50 000 – 55 000, and in reduced form the proteins migrate on polyacrylamide gels as two distinct groups of polypeptides, one in the molecular weight range 20 000 – 25 000 and the other in the 29 000 – 35 000 range. In this respect the proteins have the general characteristics of those of castor bean, but only the proteins of Jatropha gossypifolia show striking similarities. Within any one genus, the storage proteins appear to be more or less identical (e.g., Manihot spp.) or show distinct differences (e.g., Euphorbia spp.). The soluble lectin proteins of J. gossypifolia have very similar haemagglutination properties to those of castor bean lectins, and the glycoproteins of both species separate similarly on polyacrylamide gels. Few other species contain glycoproteins or lectins that can cause agglutination.
Fruit-set after pretreatment with foreign compared with killed compatible pollen
Authors: Lane W. David
Published: September 2008

A mechanism based on pollen growth-promoting substances has previously been proposed to explain the effects of mentor (killed compatible) pollen when it improves fertility of crosses between nearly incompatible parents. Similarly, pioneer pollination (two pollinations a day apart) stimulates growth of the last applied pollen and increases fruit-set. In the present experiments the effects of foreign-pollen pioneer treatments on fruit-set of apple, sweet cherry, and apricot were compared with the control, killed compatible pollen. All treatments were followed 24 h later with viable compatible pollen. The foreign pollen, Balsamorrhiza sagittata, did not inhibit fruit-set. When the foreign pollen was heat killed, fruit-set was at least as high as when untreated B. sagittata was used. Two other foreign pollens, Taraxacum officinale and Juniperus communis, resulted in lower fruit-set than B. sagittata but still more than the control. This effect was consistent with a previously hypothesized relationship for mentor pollen, relating size and degree of stimulation. The two nonpollen treatments examined, dried yeast and pectinase solution, slightly inhibited fruit-set. Mineral analysis of a composite of pollen and anther tissue indicated that boron and calcium were not deficient in the control pollen, and incompatibility mechanisms and heat-labile metabolites also were unlikely to have been the cause. No direct evidence was obtained, but pollen growth promotion by a diffusible growth regulator (such as gibberellin) is suggested as plausible and an area worthy of further study.
A clarification of the Medicago blancheana–bonarotiana–rotata complex
Authors: Small Ernest
Published: September 2008

The most recent comprehensive monograph of Medicago (K. A. Lesins and I. Lesins. 1979. Genus Medicago (Leguminosae). A taxogenetic study. Dr. W. Junk bv Publishers, The Hague.) narrowed the circumscriptions of M. blancheana (as M. bonarotiana) and M. rotata of the previous monograph (C. C. Heyn. 1963. The annual species of Medicago. Magnes Press, Jerusalem.) by interpreting the removed components as interspecific hybrids. The present study of the distribution and association of the same characters judged by both monographs to be taxonomically important in the complex supports Heyn's conclusions.
Ultrastructure of actinorhizal root nodules of Chamaebatia foliolosa (Rosaceae)
Authors: Newcomb William , Heisey Rod M.
Published: September 2008

The structure of the root nodules of Chamaebatia foliolosa Benth. (Rosaceae) has been studied by optical and transmission electron microscopy. The prokaryotic endophyte exhibits two morphological forms: septate hyphae and nonseptate elliptically shaped endophytic vesicles. This microorganism resembles the actinomyceteous endophytes of other actinorhizal root nodules especially those present in Ceanothus, Dryas, and Purshia. The endophyte is always surrounded by a polysaccharide capsule and possesses glycogen granules, lipid droplets, and prominent nucleoids. The infected host cells contain prominent lobed nuclei, numerous small vacuoles, and many plastids which possess numerous granular inclusions and osmiophilic droplets. No endophytic sporangia were observed in these nodules.
Changes of plasmolysis form in epidermal cells of Hordeum vulgare infected by Erysiphe graminis: evidence for increased membrane–wall adhesion
Authors: Lee-Stadelmann O. Y. , Bushnell W. R. , Stadelmann E. J.
Published: September 2008

When coleoptile epidermal tissues of Hordeum vulgare were plasmolyzed with α-methylglucose or mannitol, 24–72 h after inoculation with Erysiphe graminis f. sp. hordei, host protoplasts tended to pull away from one or more sites on longitudinal host cell walls producing a concave pocket at each site. This contrasted with the usual convex form of plasmolysis in uninfected tissue in which protoplasts pulled from the short transversal end walls of host cells forming protoplasts with convex ends. The tendency for concave plasmolysis encompassed entire inoculated areas at 5 colonies/mm2 and above. The concave response occurred in coleoptiles inoculated 7–12 days after planting, but not in ones inoculated at 5 days. It occurred in four of five barley lines tested at 48 h postinoculation. Treatment before plasmolysis with 10 mM Ca2+ promoted the disease-induced concavities; treatment with 15 mM K+ partially inhibited them. The concave form in plasmolyzed infected tissue was changed to the convex form by addition of 250 μM octylguanidine to the plasmolyticum or by replacement of α-methylglucose with isosmolar urea or methyl urea solutions. The results suggest that Erysiphe graminis infection increased adhesion of the host plasmalemma to the cell wall, probably as a consequence of change in membrane structure and bridging by Ca2+ ions.
Taxonomy and nomenclature of rough fescues, Festuca altaica, F. campestris (F. scabrella var. major), and F. hallii, in Canada and the adjacent part of United States
Authors: Pavlick Leon E. , Looman Jan
Published: September 2008

Three species of rough fescues occur in Canada and the adjacent part of the U.S.A.: Festuca altaica, F. campestris (F. scabrella var. major), and F. halli. Festuca altaica, a wide-ranging species of eastern Asia and northern North America, extends southward in the Canadian Cordillera to about latitude 52° N and is disjunct in eastern Canada (northern Québec, Gaspé Peninsula, western Newfoundland, etc.). Festuca scabrella Torr. in Hook, is a synonym of the earlier published F. altaica Trin. in Ledeb. Rough fescues of southern British Columbia, the southern prairie provinces of Canada, and northwestern U.S.A. that have been called F. scabrella belong to F. campestris and F. hallii, a neglected species. A key to the three taxa and a map of their distribution is presented.
An ultrastructural study of feeding techniques in three protostelids
Authors: Whitney K. D. , Bennett W. E.
Published: September 2008

Ultrastructural observations on the feeding techniques of the protostelids Ceratiomyxella tahitiensis, Nematostelium gracile, and Schizoplasmodium cavostelioides are presented. In agar culture the multinucleate amoebae of these sporocarp-forming protistans feed on bacteria and yeast. Bacterial cells are engulfed intact in typical food vacuoles. When a feeding amoeba encounters a yeast cell, however, a pseudopodial process penetrates the yeast cell wall and enters the cell lumen. The protoplasm of the yeast cell is then engulfed, and the pseudopodium withdraws. The cell wall of the yeast is left intact, except for the point of penetration. The occurrence of similar feeding behavior in the amoeboid protozoan family Vampyrellidae is discussed. The use of feeding techniques to assess mycetozoan phylogeny is considered.
Isoenzyme and protein patterns of isolates of Cryphonectria cubensis differing in virulence
Authors: Alfenas A. C. , Jeng R. , Hubbes M.
Published: September 2008

Isoenzyme and protein patterns of five isolates of Cryphonectria cubensis were determined by polyacrylamide gel electrophoresis. Differences in esterase, peroxidase, phosphoglucomutase, and hexokinase were detected between the Hawaiian (HW) isolate and the Brasilian (BR22) and African (AF100) isolates. These differences coincided with the virulence of the isolates tested on Eucalyptus pellita. The same tendency was also observed in their soluble protein patterns.
Stable carbon isotope ratios of flooded and nonflooded sunflowers (Helianthus annuus)
Authors: Guy Robert D. , Wample Robert L.
Published: September 2008

The current view regarding stable carbon isotope ratios (δ13C values) of C3 plants is that they can be related to the ratio of intercellular (leaf) to ambient partial pressures of CO2. Flooded sunflowers (Helianthus annuus L.) have recently been shown to have reduced photosynthetic rates without significant increases in diffusive resistance. This should lead to higher ratios of intercellular over ambient partial pressures of CO2 and, consequently, more negative δ13C values. Although whole apices and leaves of flooded and nonflooded sunflowers show no differences in δ13C, the aqueous fractions of leaf extracts (partitioned against chloroform) do, particularly when expressed relative to the total tissue δ13C. This shift (−0.6‰) is in the direction expected and provides confirmation that the lower photosynthetic rates of flooded sunflowers are not due simply to stomatal closure. Chloroform-soluble fractions were depleted in 13C by about 4.4‰ relative to the aqueous fractions.
A study of the germination responses of a Sardinian population of sea fennel (Crithmum maritimum)
Authors: Marchioni-Ortu Alba , Bocchieri Emanuele
Published: September 2008

Germination tests have been carried out on seeds of a Mediterranean population of sea fennel (Crithmum maritimum L.) collected from plants in Santa Margherita di Pula, in the southwest of Sardinia, Italy. Germination was evaluated in the dark at different temperatures and at various salt concentrations. The optimal conditions for germination were a constant 20 °C in deionized water or at a very low salt concentration. These conditions are strikingly different from those necessary for the germination of seeds from the Atlantic coast (Meadfoot Bay, England). The presence of dormancy in the seeds is analyzed and discussed in terms of ecophysiological control and mechanisms which prevent germination under adverse environmental conditions.
Lophophacidium dooksii n. sp., a phacidiaceous fungus on needles of white pine
Authors: Corlett Michael , Shoemaker R. A.
Published: September 2008

Lophophacidium dooksii n. sp. (Phacidiaceae) occurring on needles of Pinus strobus L. is described, illustrated, and compared with Lophophacidium hyperboreum Lagerberg, the type species. Ascomata of L. dooksii mature during the spring and summer on attached 2nd-year needles.
Compétition entre la spargoute des champs (Spergula arvensis) et la sétaire glauque (Setaria glauca). I. Production de matière sèche
Authors: Lemieux C. , Deschênes J. M. , Morisset P.
Published: September 2008

Interspecific and intraspecific competition was studied between corn spurry (Spergula arvensis L.) and yellow foxtail (Setaria glauca (L.) Beauv.) both in a greenhouse and in a field community. De Wit replacement series were used to investigate dominance relationships under both conditions. In the greenhouse experiment, yellow foxtail was found to be dominant. On the other hand, corn spurry was the dominant species in the field experiment. Two factors seem to explain the field data: low soil nitrogen levels and the earlier emergence of corn spurry in the spring.
Compétition entre la spargoute des champs (Spergula arvensis) et la sétaire glauque (Setaria glauca). II. Production de graines
Authors: Lemieux C. , Deschênes J. M. , Morisset P.
Published: September 2008

Seed production of corn spurry (Spergula arvensis L.) and yellow foxtail (Setaria glauca (L.) Beauv.) was studied in various situations of competition. Intraspecific competition affected both species in the same way; each plant produced fewer seeds when the density was increased. In such situations, the overall seed production (seeds per square metre) also increased. However, seed production of yellow foxtail (seeds per square metre) reached a plateau. Interspecific competition affected seed production of corn spurry and yellow foxtail in different ways. Firstly, for corn spurry, the number of seeds produced per plant increased with interspecific pressure while for yellow foxtail it decreased. Secondly, the total number of seeds produced per unit area is larger for corn spurry than for yellow foxtail. This suggests that corn spurry may dominate mixed populations. However, at high density, yellow foxtail seed production per unit area seems to suffer less from interspecific pressure than does corn spurry. At this level, yellow foxtail obtain a slight advantage. However, conclusion on long-term changes of the populations cannot be drawn without a study of viable seeds.
CO2 and H2O exchanges in response to alteration of photoperiod in Anagallis arvensis, a long-day flowering plant
Authors: Mousseau Marianne
Published: September 2008

Rooted cuttings of Anagallis arvensis grown in short days (SD) were given 1 to 4 long days (LD) consisting of nights interrupted by red light. Just after LD treatment, young upper leaves showed a lower net photosynthetic rate than leaves of SD control plants, measured at various light intensities and CO2 concentrations. Respiratory CO2 output decreased during the first interrupted night and remained lower for one or two SD after treatment. Net CO2 uptake during the light period decreased similarly, so that the total CO2 balance of the entire plant was the same as for SD plants during and immediately after the treatment. After one interrupted night, the transpiration rate was lower, especially in the morning. The water saturation deficit similarly decreased in young upper leaves after the LD treatment, but leaf water potential did not change. The observed changes in CO2 and H2O exchanges with alteration of photoperiod were associated with, and may be explained in terms of, stomatal movements.
Nectria tuberculariformis, Nectriella muelleri, Nectriella sp., and Hyponectria sceptri: low-temperature tolerant, alpine–boreal fungal antagonists
Authors: Samuels G. J. , Rogerson C. T. , Rossman A. Y. , Smith J. D.
Published: September 2008

The ascomycetes Nectria tuberculariformis, Nectriella muelleri sp. nov., Nectriella sp., and Hyponectria sceptri comb. nov. were collected in alpine–boreal habitats. They were low temperature tolerant, growing at 0 °C and poorly or not at all at temperatures above 18 °C. Optimum temperature for spore germination and growth was 10–15 °C. Nectria tuberculariformis was found to be the teleomorph of Acremonium boreale; Nectriella muelleri and Nectriella sp. each had Acremonium anamorphs. No anamorph formed in cultures of Hyponectria sceptri. All four species produced a diffusible substance or substances that inhibited growth of the mesophilic plant parasites Chondrostereum purpureum, Fusarium solani, Glomerella cingulata, and Phoma medicaginis var. pinodella. Nectria tuberculariformis, Nectriella muelleri, Nectriella sp., and Hyponectria sceptri are described and illustrated.
Postharvest recovery of beds of the edible red alga Porphyra perforata
Authors: Roland William G. , Coon L. Michael
Published: September 2008

Recovery of intertidal Porphyra beds following hand harvest was studied near the northwest tip of the Queen Charlotte Islands, B.C. Twenty-six percent of the standing crop of Porphyra perforata J. Ag. was removed in a large plot in June 1981; no negative effect on standing crop was apparent in May 1982 as compared with the adjacent control area. There was no negative impact on percent cover of Porphyra (mostly P. perforata) within 1 year after hand harvest of seven, approximately 1-m2 plots, as compared with respective controls. Annual fluctuation in cover, biomass, and relative mix of Porphyra species was large. Porphyra cover in a small plot harvested in early June 1981 increased to 86% of the June value by mid-July 1981, indicating substantial growth of the remaining thallus fragments and small, whole plants within one season. It was concluded that sustained yield of Porphyra beds can be assured if harvest is restricted to gathering by hand.
Seismic stress effects on vegetative and reproductive development of ‘Alaska’ pea
Authors: Akers Stuart W. , Mitchell Cary A.
Published: September 2008

Vegetative and reproductive growth responses of pea (Pisum sativum L. cv. Alaska) to periodic seismic (shaking) stress were investigated during fall, winter, and spring seasons in a greenhouse. Growth changes caused by equivalent shaking treatment varied quantitatively among seasons, with the least response occurring during winter, but they were qualitatively similar during all three seasons. Shaking caused significant reduction in all growth parameters measured except root dry weight and leaf number after 16 days of treatment. Reproductive growth responses to shaking (occurring from 16 to 35 days of treatment) included delay of anthesis but no difference in number of fruits set after as much as 35 days of treatment. Seismic stress significantly reduced the number but not the weight of individual seeds per pod. Mean relative shoot growth rate was reduced by shaking during reproductive as well as vegetative growth. During both periods of development this response was caused almost entirely by inhibition of net carbon assimilation rate.
Isozyme variability among isolates of Phytophthora cinnamomi from Australia and Papua New Guinea
Authors: Old K. M. , Moran G. F. , Bell J. C.
Published: September 2008

Genetic variation in 183 isolates of Phytophthora cinnamomi from a wide range of hosts and locations in Australia and Papua New Guinea (PNG) was assessed at 20 isozyme loci. Low levels of isozyme variation were found in both the A, and A2 mating types within Australia. Only two A2 multilocus genotypes were detected among Australian and PNG isolates, the more common one being found throughout the range. Fourteen of the 15 A1 isolates from 12 locations in Australia were identical at all 20 isozyme loci. In contrast there was much higher variability in the eight PNG A1 isolates compared with the Australian Ai isolates and all A2 isolates. The A1 and A2 mating types can be distinguished isozymically suggesting that they are genetically isolated and that sexual reproduction involving both mating types does not occur in the field.
Light and scanning electron microscopic observations of calcium oxalate crystals produced during growth of Sclerotium rolfsii in culture and in infected tissue
Authors: Punja Z. K. , Jenkins S. F.
Published: September 2008

Crystals produced during growth of Sclerotium rolfsii on cellophane overlaying water agar were identified as calcium oxalate based on their solubility characteristics in certain acids, positive staining reaction with silver nitrate – dithiooxamide, and characteristic energy-dispersive X-ray emission spectrum. Addition of calcium salts to water agar enhanced crystal formation. Similar crystals of calcium oxalate were observed with the light and scanning electron microscopes in sugar beet and carrot leaf tissues infected by Sclerotium rolfsii. They frequently formed along the infecting hyphae or were associated with hyphal aggregates and were observed in abundance within the tissue. Addition of oxalic acid solutions to leaf discs resulted in necrosis of the tissue, and crystals similar in all respects to those produced in infected tissues were formed. These observations indicate that the oxalic acid produced by Sclerotium rolfsii in culture or in diseased tissue may sequester available calcium to form calcium oxalate, and provide evidence for the role of oxalic acid in pathogenesis.
Interaction of gibberellic acid, abscisic acid, and phenolic compounds in the control of hypocotyl growth of Amaranthus caudatus seedlings
Authors: Ray S. D. , Laloraya M. M.
Published: September 2008

Abscisic acid, a potent growth inhibitor, inhibits hypocotyl growth of Amaranthus caudatus (L.) seedlings. Phenolic compounds when applied with ABA (abscisic acid), antagonize ABA action and restore normal seeding growth. GA (gibberellic acid) promotes hypocotyl growth and on combined application with ABA, the ratio of their concentrations determines the course of the resultant growth. This interaction can be modulated by phenolic compounds. Phenolic compounds in low concentrations when present together with GA and ABA favour GA-induced growth by antagonizing the inhibitory effect of ABA. Inhibitory action of abscisic acid on growth is so far known to be counteracted only by growth-promoting hormones. Antagonistic action of phenolic compounds imparts a dual role to this class of compounds, balancing the effect of growth-promoting and growth-inhibiting hormones.
Effect of frond age on frond elongation, gas exchange, and water relations in the ostrich fern (Matteuccia struthiopteris)
Authors: Prange R. K. , Ormrod D. P. , Proctor J. T. A.
Published: September 2008

The effect of frond age in the ostrich fern (Matteuccia struthiopteris) upon changes in frond elongation, frond water status (osmotic, pressure, and total water potential), and gas exchange (diffusive resistance, net photosynthesis rate, and dark respiration rate) was examined. The maximum elongation rate in the youngest fronds was 2.83 mm h−1 and occurred between 1500 and 2100 hours. Growth of individual fronds was completed in ca. 16–20 days after emergence from the apical bud. As a frond approached final length, both the dark respiration rate and rate of daily elongation decreased. Compared with mature fronds, young fronds (5 to 8 days old) had higher dark respiration rates and lower net photosynthesis rates. They also had higher osmotic potentials and lower pressure potentials and predawn diffusive resistances. In the youngest fronds (3 and 6 days old) the fastest elongation rates occurred at the lowest water potentials. This phenomenon may be an example of "growth-induced water potential." The increase in pressure potential and decrease in osmotic potential as the frond approached full expansion on day 16 indicates an "apparent" osmotic adjustment which was probably due to a decrease in the yielding properties of the cell walls while solutes continued to accumulate in the tissue. At full expansion further accumulation appeared to stop, suggesting that the frond had increased net solute export.