bluuebunny/crossref_metadata_2025 huggingface dataset:
Electron microscopic study of oospore maturation and germination in an emasculate isolate of Saprolegnia ferax. 1. Gross changes
Authors: Beakes Gordon W.
Published: April 2011

The main morphological and cytological changes which accompany oospore maturation and germination in an emasculate isolate of Saprolegnia ferax have been followed by light and transmission electron microscopy. Oospore development proved similar to that described in antheridiate species except for the absence of motile granules within the central ooplast vacuole. Germination followed within a few days of maturation although it did not occur synchronously within a single oogonium. The ending of dormancy is indicated by a thinning of the oospore wall and a decrease in cytoplasmic refractivity. A new germination wall is secreted around the protoplast and the contents of the central ooplast break down and are partially dispersed into the peripheral cytoplasm as it becomes transformed into a typical somatic vacuole. Oospores swell slightly before the emergence of between one and four germ tubes. These often grow extensively within the oogonium, occasionally infesting and possibly parasitizing neighbouring germlings, before rupturing either the thin-walled pits or basal septa. After emergence most germ tubes continue to grow vegetatively in a sparsely branched fashion, although a few develop terminal sporangia. Oospore germination in this isolate is compared with that described in other oomycete species.
Une méthode de planification expérimentale appliquée aux cultures de tissus végétaux. Exemple de la canne à sucre (Saccharum sp.)
Authors: Sauvaire Didier , Galzy Rose
Published: April 2011

Fragments of roots and shoot tips were taken from sugarcane (Saccharum sp., clone Q 75) plants propagated in vitro. The effects of light, 2, 4-dichlorophenoxyacetic acid and 6-benzyl-aminopurine on initiation and growth of calli were observed. These factors were first studied at two levels in an experiment based on a factorial design. Light appears to inhibit callus formation. Thus, the next experiments were carried out in the dark. Optimization of the concentrations of growth substances was attained using a more complete factorial plan, according to Box and Wilson's method. Mathematical models were established and used in the calculation of the most favourable combinations of these growth substances. The diffusion of phenolic compounds in the media never occurred. Neoformation of plants was obtained by transferring calli of stem origin to a medium with a low concentration of auxin.
In situ localization and morphology of the bacterium associated with ratoon stunting disease of sugarcane
Authors: Kao J. , Damann Jr. K. E.
Published: April 2011

Freshly sectioned tissues of sugarcane with ratoon stunting disease (RSD) were examined with the scanning electron microscope. The RSD-associated bacterium was recognized by its diameter, pleomorphism, and xylem association. It commonly occupied the protoxylem and metaxylem vessels. The bacterium was observed in the gaps between secondary wall thickenings of xylem vessels and also adhering to the secondary wall. The lacunae, tracheids, and xylem parenchyma cells also were invaded by the bacterium. The lumen of some infected xylem elements was filled with a dense network of bacterial cells; Remnants of a supporting matrix were observed in some of these lumina. Unicellular forms were most frequently observed; however, swollen forms, filamentous branching forms, and microcolonies consisting of tightly aggregated bacterial cells which we have previously described from extracts of diseased tissue also were observed.
Bryophytes of northern Quebec and Labrador
Authors: Ireland Robert R. , Bellolio-Trucco Gilda , Kallio Paavo
Published: April 2011

A large collection of bryophytes from northern Quebec and Labrador, Canada, made in 1967 is reported to consist of 29 liverworts and 147 mosses, including 17 Sphagna. New to Quebec are Aongstroemia longipes (Somm.) B.S.G., Ceratodon heterophyllus Kindb. ex J.M. Mac, Marsupella brevissima (Dumort.) Grolle, and Polytrichum sexangulare Brid. New to Labrador are Aulacomnium palustre var. imbricatum B.S.G., Bryum pallescens Schleich. ex Schwaegr., Dicranella schreberiana var. robusta Schimp. ex Braithw., Hypnum bambergeri Schimp., and Splachnum luteum Hedw.
Studies of root function in Zea mays I. Apparatus and methods
Authors: Miller D. M.
Published: April 2011

An apparatus is described to which the cut end of an excised root may be sealed and the developing root pressure measured by a transducer as a function of time. In addition to measurements of pressure under zero volume flow, flow rates at various applied pressures may also be obtained. By applying an instantaneous pressure change which is just sufficient to terminate flow, the true osmotic driving force within the root can be determined. This provides a measurement of the hydraulic conductivity of the root which is independent of the presence of unstirred layers and of osmotically active species whose reflection coefficients may not be one. The technique also separates the effects which changes in hydraulic conductivity (Lp) and solute flux (Js) exert on volume flow(Jv)
The role of malate in nitrate reduction in spinach leaves
Authors: Woo K. C. , Canvin D. T.
Published: April 2011

In spinach leaf discs the accumulation of nitrite from nitrate reduction under anaerobic conditions in the light in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) was inhibited by air. The inhibition of nitrate reduction by air was reversed by antimycin A but not by rotenone or amytal. The nitrate-reducing system of DCMU-inhibited leaf discs in the light appeared similar to noninhibited leaf discs in the dark. In aerobic conditions, the addition of malate stimulated nitrite accumulation. This stimulation was unaffected by malonate. Under anaerobic conditions, malate reversed the inhibition of nitrate reduction caused by either iodoacetate or arsenite to rates similar to those observed in the dark and in the light with DCMU. Malate can apparently provide a direct source of cytosolic NADH for nitrate reduction.
Effect of sugars on microconidium production by macroconidia and primordial hyphae of Fusarium acuminatum
Authors: Neish G. A.
Published: April 2011

Germinating macroconidia from a strain of Fusarium acuminatum can produce microconidia either directly from the macroconidium or from the primordial hyphae. The most abundant microconidial production occurs when the macroconidia are allowed to germinate on media containing raffinose or sucrose. Moderate microconidium production occurs when the medium contains lactose, but on media containing fructose, galactose, glucose, trehalose, or mixtures of some of these, microconidium production is generally low.
Dimorphism in bud regeneration in flax (Linum usitatissimum)
Authors: Chlyah H. , Sqalli-Khalil M. , Chlyah A.
Published: April 2011

The study of the expression of morphogenetic potential in stem segments of flax (Linum usitatissimum L.) was undertaken as a function of donor plant age and level (basal, median, or apical) on the stem axis and in the absence of growth regulatory substances. Neoformation of normal buds (resembling seedlings) gave rise to shoots with no visible axillary buds, and a few roots were obtained from explants taken from young, vegetative plants; these organs were more numerous on basal than on apical explants. If the donor plant was in a prefloral or floral state, thus older and at a different physiological stage, a "modified" bud was formed, characterized by its slow growth, short thick stem and leaves, and sometimes with visible axillary buds. This type of bud was more numerous in apical than in basal segments. Callus was also formed and was reduced in size and limited to the cut extremities of explants when the donor plant was young, but was large and covered almost all the explant when the plant was older.
Cyptotrama asprata (Agaricales) from North America and notes on the five other species of Cyptotrama sect. Xerulina
Authors: Redhead S. A. , Ginns J.
Published: April 2011

Cyptotrama asprata comb.nov. is described from basidiomes and a single mycelial culture. Nine names are accepted as synonyms of C. asprata. The fungus is circumglobal but absent from Europe and northwestern North America. Five other species are accepted in section Xerulina, namely: C. costesii (synonym is Marasmius echinatus), C. deseynesiana comb.nov., C. granulosa comb.nov., C. lachnocephala, and C. verruculosa.
Comparative effects of phalloidin and cytochalasin B on motility and morphogenesis in Allium
Authors: Palevitz Barry A.
Published: April 2011

Cytochalasin B (CB), thought to disaggregate F-actin in animal cells, and phalloidin (Phal), known to stabilize F-actin in vivo and in vitro, have nearly identical effects on cotyledon epidermal cells of Allium cepa. Both drugs rapidly induce cessation of streaming and both, by preventing normal telophase reorientation movement, lead to abnormal division planes in dividing guard mother cells. Neither, however, prevents normal microtubule deposition, wall thickening, and cellulose orientation during guard cell differentiation. Furthermore, both drugs have no effect on spindle formation and anaphase chromosome motion. Examination of Nitella and Chara cells, in which streaming had been stopped by either agent, shows that microfilament cables are still present. With both drugs, the minimum effective concentrations were routinely used (CB, 2 μM; Phal, 100–200 μM). Our results are discussed in terms of the mode of action of these drugs and their possible role in host-fungus interactions. Implications for the mechanisms underlying cell plate alignment, cellulose orientation, and cytoplasmic streaming are discussed.
Fine structural and biochemical characterization of phloem proteins
Authors: Kollmann Rainer
Published: April 2011

The heterogeneous group of proteins occurring in the exudate of cut phloem tissue will be termed phloem proteins. Their molecular weights range from less than 30 000 to over 100 000. The protein pattern is a species-specific constant. Depending on the plant species the bulk of phloem proteins is either basic or acidic. In Cucurbita maxima up to 40% of the total phloem proteins are basic proteins with a molecular weight of 116 000; it shows G–F transition properties in vitro and represents the so-called P-protein in the sieve tubes of angiosperms. Depending on the stage of cell differentiation the P-protein shows various conformational changes in situ: amorphous, filamentous tubular, and paracrystalline structures are described. P-protein differs from actin- or tubulinlike proteins with regard to their molecular weight and most biochemical characteristics. The main discrepancy is the failure to bind either heavy meromyosin or any nucleotides and colchicine. No structural evidence exists for cytoplasmic streaming in mature sieve tubes based on an actin–myosin system. The function of P-protein is still questionable; sieve pore plugging after wounding, sites of enzymatic activity, and surface interaction are discussed.
Ultrastructural and biochemical effects of endopectate lyase on cell walls from cell suspension cultures of bean and rice
Authors: Baker Con J. , Aist James R. , Bateman Durward F.
Published: April 2011

Cell walls prepared from suspension cell cultures of bean and rice in log-phase growth were used to examine the effects of endopectate lyase (PL) on the solubilization of cell wall carbohydrates and concomitant ultrastructural alterations. Cell wall preparations from both plant sources were heterogeneous and contained a range of wall types from primary walls to xylem elements with spiral, secondary wall thickenings. Marked differences in wall thickness and number of wall laminations typified both preparations.Bean cell walls were more susceptible to degradation by PL than were those of rice. Upon treatment of the former with 2.3 × 10−3 units/mL of PL (1 unit released 1 μmol of unsaturated uronide/min at 30 °C from polygalacturonic acid at pH 8.5), 27% of the noncellulosic wall carbohydrate was solubilized in 1 h. This represented 50% of the PL susceptible carbohydrate in the preparation. Only 3% of the noncellulosic carbohydrate was released from rice cell walls in 1 h when treated with 115 × 10−3 units of PL/mL. This accounted for 60% of the PL susceptible wall fractions. Only uronic acid, rhamnose, galactose, and arabinose were solubilized from both preparations by PL.Cell walls in the bean and rice preparations were affected differentially by the PL. Those walls with secondary thickenings did not appear to be degraded, while the distinct fibrillar appearance of both bean and rice walls tended to fade or disappear. The middle lamella tended to dissolve to varying degrees in the presence of PL. Bean walls were more severely degraded than were the rice walls and many exhibited swelling, separation of wall layers, markedly reduced staining intensity, and (or) a granular ultrastructure.This study has demonstrated that as PL acts on susceptible cell walls there are major changes evoked in cell wall structure which suggest that the rhamnogalacturonan fraction of the higher plant cell wall contributes significantly to cell wall integrity. This study also emphasizes the need for cell wall material of proven uniformity for investigations of both cell wall composition and effects of specific polysaccharide degrading enzymes on cell wall integrity. Preliminary studies indicate that tobacco pith may provide more uniform cell walls than do cell suspension cultures.
Effects of annual burning on grassland in the aspen parkland of east-central Alberta
Authors: Anderson Howard G. , Bailey Arthur W.
Published: April 2011

Annual early spring burning has markedly altered the physiognomy and species composition of aspen parkland vegetation of east-central Alberta. Burning was conducted in April for at least 24 years when soil moisture was normally high. The number of herbaceous species per quadrat doubled while a number of woody species declined slightly. Forest cover declined while grassland increased. In the grass and shrublands, cover of the shrub Symphoricarpos occidentalis and the cool season grass Festuca scabrella declined greatly. Major increases in Calamovilfa longifolia, Carex obtusata, C. heliophylla, and Solidago missouriensis were noted. While the cover of Festuca scabrella and Stipa spartea var. curtiseta decreased; frequency of these species increased. Cover of all shrubs decreased, Populus tremuloides suckers excepted, while density of the fire adapted Elaeagnus commutata, Amelanchier alnifolia, Prunus virginiana, and Populus tremuloides suckers increased. Burning reduced the leaf blade length of all major grasses and sedges. Effect of burning on inflorescence production varied from species to species. Annual herbage production was reduced by burning with the grass and sedge component experiencing about a 50% reduction. Burning caused an increase in organic matter and phosphorus content of the Ah horizon. Burning did not appear to detrimentally affect the nitrogen status of the Ah horizon.
The maceration of deciduous leaf litter by aquatic hyphomycetes
Authors: Suberkropp Keller , Klug M. J.
Published: April 2011

Isolates of five species of aquatic hyphomycetes were grown in pure culture with hickory leaf material as the sole source of carbon and energy. Enzymatic activity by all five species resulted in the skeletonization of leaves through maceration of the leaf matrix and subsequent release of leaf cells as fine particulate organic matter. Fractionation and analysis of leaf material after incubation indicated that all five species metabolized (degraded) cellulose and two species metabolized (degraded) hemicelluloses. In cultures inoculated with Tetracladium marchalianum, fine particulate release coincided with increases in fungal biomass (ATP) and activity of enzymes in the supernatant which degraded carboxymethylcellulose, xylan, and polygalacturonic acid. Macerating activity increased with increasing pH suggesting involvement of pectin trans-eliminase in the softening of leaf tissue by this fungus.
Control of morphogenesis in the gametophyte of a fern by light and growth hormones
Authors: Swami Piyush , Raghavan V.
Published: April 2011

The effects of 2,4-dichlorophenoxyacetic acid (2,4-D), gibberellic acid (GA), and abscisic acid (ABA) on the morphogenesis of gametophytes of Lygodium japonicum growing as longer-than-broad biplanar plates in red light and as broader-than-long biplanar plates in blue light were studied. Addition of 2,4-D or GA to the medium induced a change in the form of gametophytes from biplanar to filamentous in red light. Gametophytes growing in a medium containing 2,4-D in blue light were longer than broad, very much like gametophytes growing in the basal medium in red light. Although ABA generally retarded the growth of gametophytes in both light regimes, its presence in a medium containing 2,4-D nullified the effect of the latter, causing gametophytes to become plate-like in red light and short and stunted in blue light. Changes in the morphology of gametophytes induced by growth hormones were accompanied by corresponding changes in their length:width ratio and cell number.
Characterization of the single protein and two nucleic acids of peach rosette mosaic virus
Authors: Dias H. F. , Allen W. R.
Published: April 2011

Purified preparations of peach rosette mosaic virus (PRMV), were shown by rate-zonal centrifugation in sucrose and equilibrium centrifugation in CsCl to be composed of two nucleoprotein components with buoyant densities of 1.47 (middle) and 1.51 (bottom) g/cm3. The virus contains two RNA species with molecular weights of 2.5 × 106 (RNA 1) and 2.2 × I06 (RNA 2), and a single protein subunit with a molecular weight of 57 000. RNA 1 and RNA 2 reside separately in components B and M, respectively. Both RNAs are required for infection thus indicating that the virus has a divided genome. The nucleotide composition of both RNAs is similar except for cytidilic acid. The hyperchromic profile for the M component is broader than that of B and the Tm value is higher (for M Tm = 55 °C; for B Tm = 48 °C). Particle disruption and release of RNA progresses slowly over the absorbance–temperature transition. Only half of the particles were dissociated at the Tm value. Freezing dissociates most of M component into RNA 2 and protein but had no effect on the B component. Sodium chloride protected the M particles from low temperature disruption. The data support the conclusion that PRMV is a nepovirus with particular properties of the tomato ring-spot virus (TomRSV) subgroup.
The genus Cicuta in North America
Authors: Mulligan Gerald A.
Published: April 2011

Four species of Cicuta (family Umbelliferae) are recognized for North America: C. maculata L. (2n = 22), C. douglasii (DC.) Coult. & Rose (2n = 44), C. virosa L. (2n = 22), and C. bulbifera L. (2n = 22). Cicuta maculata has 22 large somatic chromosomes, C. virosa has 22 small somatic chromosomes, C. bulbifera has 22 medium sized chromosomes, and C. douglasii has 22 large chromosomes and 22 small chromosomes. Four varieties of C. maculata are recognized: var. maculata, var. angustifolia Hook., var. victorinii (Fernald) Boivin, and var. bolanderi (S. Wats.) G. A. Mulligan, stat. nov. Cicuta mackenzieana Raup is considered conspecific with C. virosu. The nomenclature, distribution, and relationships of the North American species are given together with an identification key to species and varieties.
Effets de deux types de refroidissements sur l'ultrastructure des ébauches foliaires du Picea abies. I. Etude après fixation chimique
Authors: Dereuddre Jean
Published: April 2011

Deep freezing of Norway Spruce twigs alters the cell ultrastructure of leaf buds. Upon progressive cooling down, contraction of the protoplasm, the formation of clear areas in the cytoplasm and in organelles, and a condensation of the heterochromatin occur. These changes are reversible; they result from the partial dehydration of the buds caused by the freezing of the twigs and from the conditions of fixation. A continuous and quick cooling of the twigs brings about a fatal intracellular crystallisation and then breaks the cytomembranes.
Dimorphic incompatibility and gender in Nymphoides indica (Menyanthaceae)
Authors: Barrett S. C.H.
Published: April 2011

Nymphoides indica (Menyanthaceae) is a distylous, aquatic perennial of pantropical distribution. Controlled field pollinations in a Lower Amazon rice field population demonstrated the presence of a strong self- and intramorph-incompatibility system in the 20 individuals tested. The average seed fertility of short-styled individuals was significantly greater than long-styled individuals, although significant variation among individuals within morphs was also evident. Fertility data obtained from experimental crosses are utilized for developing a new method for the estimation of gender in plants. The potential for gender specialization in N. indica populations and its significance to the evolution of dioecy from distyly in the genus Nymphoides is discussed.
Hypostase development in Ornithogalum caudatum (Liliaceae) and notes on other types of modifications in the chalaza of angiosperm ovules
Authors: Tilton Varien R.
Published: April 2011

Seven types of chalazal modifications have been reported to occur as normal developmental changes in angiosperm ovules. Among them is the hypostase, a group of usually lignified cells. In Ornithogalum, hypostase differentiation becomes evident during the meiotic–mitotic interphase. Differentiation proceeds toward the micropylar end of the ovule at first but later becomes bidirectional. Differentiation is usually completed after the third mitotic division of the megagametophyte has occurred. One to three hypostase cells per ovule have what appears to be a nonstarch carbohydrate storage product. The greatest proportion of starch reserves in the mature ovule occurs in the chalazal end of the nucellus and, although the hypostase does not seem to be an important storage tissue, it probably has an integral function in the translocation of nutrients into the megagametophyte and, after fertilization, into the embryo sac.
On Dichodontium pellucidum and D. olympicum
Authors: Tan B. C. , Schofield W. B.
Published: April 2011

A detailed morphological comparison was made between Dichodontium pellucidum (Hedw.) Dix. and D. olympicum Ren. & Card, in search for new taxonomic features. The two species are found to differ distinctively in cellular details of the ventral surface of the leaf costa, exothecial cells, and in sexuality. A distribution map is prepared for D. olympicum, a western North American endemic. Comparisons of anatomical features are also made between the two taxa of Dichodontium and European specimens of Oreoweisia serrulate (Funck) DeNot. The results support the assertion that all North American specimens of Oreoweisia serrulata should be referred to Dichodontium pellucidum.
Floraison et réversion chez Sinapis alba. II. Caractères morphologiques de plantes porteuses de réversions
Authors: Bagnard Clémence
Published: April 2011

When plants have been submitted to a short inductive phase, then to a long dysperiodic phase, and finally to inductive conditions again, one or several branches, with or without subtending leaves, develops on some inflorescences above a series of flowers. These branches constitute a morphological inflorescence reversion, and the axis which carries them is called "α axis." Maximal vegetative characteristics are found at the basal part of a reversion. When several consecutive axes are a axes, the most vegetative reversion (maximal reversion) is developed on the lowest of these axes. Some more or less abnormal structures, such as a series of bracts, an axis with a "terminal" flower, proliferated flowers, or virescences, are sometimes inserted between typical flowers and branches on the edge of the reversed region.Apart from inflorescences, some gradients are different from those shown by plants maintained in inductive conditions: the slope of the "axillary relativity" curve is reversed, and the final length gradient of the six upper leaves of the main axis is attenuated.
An outline for the reclassification of the Chytridiales, and for a new order, the Spizellomycetales
Authors: Barr Donald J. S.
Published: April 2011

An outline is presented for the reclassification of the Chytridiales into two orders based on fundamental differences in zoospore ultrastructure. The new order Spizellomycetales includes species with the Phlyctochytrium–Entophlyctis type of zoospore and also Karlingia, Olpidium, and Rozella. Four new genera, Spizellomyces, Gaertneriomyces, Triparticalcar, and Kochiomyces replace the Phlyctochytrium complex. The revised Chytridiales includes species with the Rhizophydium–Chytridium–Nowakowskiella type of zoospore, as well as Synchytrium,
Measurement of cultured plant cell growth on filter paper discs
Authors: Horsch Robert B. , King John , Jones Gary E.
Published: April 2011

To measure growth of cell cultures with minimal or no disturbance, a thin layer of cells can be separated from the agar medium by a disc of filter paper. The disc and adhering cells are removed periodically, weighed, and replaced. With this filter paper growth assay it is possible to produce a complete growth curve from a single culture without sacrificing that culture. It provides immediate measurement of wet weight, and allows for transfer of cultures to different media without interruption of growth. During the initial stages of growth, cells are spread thinly over a large surface with relatively uniform exposure to the medium, thus combining some of the benefits of growth in suspension with the lower cost and simplicity of callus culture.
Somatic hybridization between Nicotiana rustica and N. tabacum. III. Biochemical, morphological, and cytological analysis of somatic hybrids
Authors: Douglas G. C. , Wetter L. R. , Nakamura C. , Keller W. A. , Setterfield G.
Published: April 2011

The hybrid nature of parasexually produced plants of Nicotiana rustica L. + N. tabacum L. has been verified by biochemical, morphological, and cytological analysis. The isozyme banding patterns for esterase, aspartate aminotransferase, and superoxide dismutase of 10 somatic hybrid lines were compared with the parent species. The banding patterns were complex and for any given enzyme they varied among the hybrid lines. For each enzyme assayed a number of isozyme bands derived from both parental species were found in the hybrids. The aspartate aminotransferase zymogram of the hybrids was particularly interesting consisting of a unique hybrid band and also a dense band which appeared as a result of the presence of both parental bands. Leaf and flower morphology of a further 17 hybrid plant lines was analyzed and found to be generally intermediate with respect to the parents though the variability between lines was great considering the small statistical sample. A heterosis effect for plant vigor and height was observed among one-third of the lines. Self-fertility was low among the hybrid lines with only two yielding viable seeds. Only one hybrid line had the expected chromosome complement of 96; all the others contained less. The chromosome complement of the hybrids was unstable ranging from 2n = 68 to 96 between different lines and also varied among different members of the same line ranging from 2n = 68 to 92. The genetic instability indicated by variable chromosome complements can account for the variability found in the biochemical and morphological analyses.
Isolation from legume tissues of an agglutinin of saprophytic pseudomonads
Authors: Jasalavich Claudia A. , Anderson Anne J.
Published: April 2011

Water extracts from leaves, roots and stems of green bean and leaves of mung bean, soybean, and lima bean caused agglutination of cells of a saprophytic bacterium, Pseudomonas putida. The agglutinin from each source was purified in an identical manner using procedures of ion exchange, gel, and affinity chromatography. Purified preparations contained both carbohydrate and protein, were of high molecular weight (at least 106), required Mg2+ for activity and were heat stable. Less than 1 μg of hexose or protein of the purified preparations was required to completely agglutinate about 109P. putida cells. Arabinose, galactose and galacturonic acid were the predominant glycosyl residues detected in the purified agglutinin preparations. Agglutination tests with the crude and purified preparations from each legume showed strong and consistent agglutination with only pseudomonad saprophytes, P. putida, P. fluorescens, and P. aeruginosa. No agglutination of other plant pathogenic bacteria or nonpseudomonad saprophytes was observed.
Two action sites of AM-toxin I produced by apple pathotype of Alternaria alternata in host cells: an ultrastructural study
Authors: Park Pyoyun , Nishimura Syoyo , Kohmoto Keisuke , Otani Hiroshi , Tsujimoto Kazuyuki
Published: April 2011

The localization of primary action sites of AM-toxin I in host cells was examined by ultrastructural investigation and electron microscopic autoradiography. In susceptible apple leaves, the first effect of the toxin appeared 1 h after treatment in the plasma membranes and chloroplasts of mesophyll and vascular bundle sheath cells and in the plasma membranes of phloem and epidermal cells. Membranes and vesicles which were stained positively with a specific staining solution for grana lamellae were found in the matrix of the chloroplasts, showing that the membranous materials were derived from the disrupted grana. Cell wall lesions were formed around plasmodesmata where plasma membranes were invaginated. The invaginated sites were filled with amorphous materials from degraded cell walls, including membranes derived from plasma membranes and the desmotubules extending from plasmodesmata. The modified chloroplasts and plasma membranes were observed more often as the time after the toxin treatment was prolonged. Modified plastids were not found in the leaf cells. The other cellular membranes appeared normal even 10 h after the treatment. Resistant leaf cells were rarely affected by the toxin. Not all tissues from susceptible apples were sensitive as the toxin caused no necrosis or ultrastructural changes in petal cells. Resistant petal cells were also insensitive to the toxin, but the toxin causes necrosis and ultrastructural changes in moderately resistant petal cells in which the primary effect of the toxin appeared as plasma membrane modifications. Plastids were not affected by the toxin. These results indicate that the action sites of the toxin may be located on the plasma membrane – cell wall association in susceptible leaf cells and in moderately resistant petal cells and also on the chloroplasts of susceptible cells. The results of electron microscopic autoradiography also provided evidence that the action sites of the toxin were present on chloroplasts and the plasma membrane –cell wall association of susceptible leaf cells.
Elemental composition of globoid crystals in protein bodies of wheat grain grown on soil treated with sewage sludge
Authors: Spitzer Ernest , Webber Mel , Lott John N. A.
Published: April 2011

Wheat grain grown on soil treated with a heavy application rate of sewage sludge exhibited higher iron, zinc, copper, and cadmium contents than did wheat grain grown on an unfertilized control treatment. The sludge supplied more than the maximum amounts of zinc, copper, cadmium, and lead recommended for addition to Ontario agricultural lands.Globoid crystals, which are inclusions in protein bodies, are the major mineral storage component of wheat grain. The elemental composition of globoid crystals in wheat grain grown with and without sludge treatment was determined using energy dispersive X-ray (EDX) analysis. Globoid crystals from sludge-treated and control grains exhibited similar elemental compositions with the following exceptions. When comparing sludge-treated grains versus the controls: more globoid crystals in the aleurone layer farthest from the peduncle contained calcium; more coleoptile mesophyll globoid crystals contained calcium, manganese, and (or) iron; some globoid crystals in the young foliage leaves contained manganese; and some globoid crystals in the stele of the radicle contained calcium. The globoid crystals exhibited no tendency to accumulate toxic metals supplied by the sludge indicating that the mineral storage system in wheat is remarkably specific despite varying soil conditions.
A simplified method for identifying Fusarium spp. occurring on wheat
Authors: Nirenberg Helgard I.
Published: April 2011

The 18 Fusarium species or varieties (F. acuminatum, F. anthophilum, F. avenaceum, var. avenaceum, F. culmorum, F. dimerum var. dimerum, F. equiseti var. equiseti, F. graminearum, F. merismoides var. merismoides, F. nivale var. nivale and var. majus, F. oxysporum var. oxysporum, F. poae, F. sacchari var. subglutinans, F. sambucinum var. sambucinum, F. solani var. solani, F. sporotrichoides var. sporotrichoides, F. tricinctum, and F. verticillioides) most frequently isolated from wheat are described and illustrated. The experimental conditions used in this study, such as medium, near ultraviolet irridiation at a wave-length of λ = 300–400 nm (black light), and temperature, cause some alteration of the morphology of some of the taxa to which plant pathologists are accustomed if the strains are grown on richer media and (or) without black light. This does not matter, however, because the method described here allows each species or variety to develop a unique and stable set of morphological features, which distinguishes it from all other taxa.
CO2 is essential for colony initiation by flax rust fungus grown in vitro
Authors: Boasson Rosalinda , Shaw Michael
Published: April 2011

Cultures were grown under a constant stream of gas of known composition to eliminate accumulation of any volatiles produced by the fungus. CO2-free air completely inhibits colony initiation. Air containing 1% CO2 allows colony initiation to the same extent as occurs in plugged, nonaerated controls, while "normal air" (ca. 0.03% CO2) causes initiation to be delayed to a variable extent.
The structural basis for infection of root hairs of Trifolium repens by Rhizobium
Authors: Callaham Dale A. , Torrey John G.
Published: April 2011

Root hair infection of Trifolium repens L. by Rhizobium trifolii was investigated with regard to the structural basis of infection thread origin. Most infected root hairs were shown to have in common an enclosed region at-the site of thread origin formed by specialized root hair growth or contacts. Electron micrographs of diverse infection sites showed in every case a degradation of the root hair wall at the site of thread origin within the enclosure. The thread wall is a new layer formed by apposition of material by the host cytoplasm near the penetrated wall and surrounding the break as encapsulation of the invading rhizobia. It is suggested that rhizobial enzymes provide for degradative penetration of the root hair cell wall and that localized concentrated activity of hydrolytic enzymes as well as protection from cell lysis is favored by physical constraints provided by the deformed root hair enclosures.
Aerial root cap structure of an orchid, Epidendrum
Authors: Blackman Susan J. , Yeung Edward C.
Published: April 2011

The root cap of Epidendrum ibaguense has a rounded profile with a root cap junction present between the cap and meristem. A distinct columella region is lacking. Mitotic figures are infrequent in the root cap initial cells. The root cap initials and their immediate derivatives show few dictyosomes, little endoplasmic reticulum, plastids lacking starch, and few vacuoles. As the cells age they increase in size and show increasing vacuolation. Plastids increase by division and accumulate large starch grains. Throughout the root cap, amyloplasts maintain a random orientation in the cell. Endoplasmic reticulum also becomes more abundant as the cells age. In older cells, hypertrophied dictyosomes are evident and cell wall material begins accumulating between the distal cell wall and the plasmalemma. Wall thickening progresses with age though radial walls remain largely unthickened. Vacuolation progresses and is followed by complete senescence leaving only the cell walls.
Understorey–canopy affinities in boreal forest vegetation
Authors: Carleton T. J. , Maycock P. F.
Published: April 2011

One hundred and ninety-seven boreal forest stands, in a region of Ontario and Quebec south of James Bay, were examined. Tree species were summarized as relative density of each of five stem size classes. These data formed the basis for an exclusive polythetic divisive stand classification into 10 groups. Most of these groups were characterized by a single tree species. The affinity of each of 410 understorey taxa was assessed with respect to each canopy stand group or natural combination of groups. Only 121 understorey taxa showed specificity to the canopy classes identified. This apparent lack of tight overstorey–understorey affinity is discussed in relation to site nutrient status and regeneration following forest fire.
Variation in seed germination inhibition of Chenopodium bonus-henricus in relation to altitude of plant growth
Authors: Dorne Albert-Jean
Published: April 2011

Chenopodium bonus-henricus achenes have poor germination whatever the temperature; this phenomenon is reinforced with increasing elevation of seed harvest. Since the excised embryo is never dormant, germination of intact seeds is prevented by the seed coat. The seed coat thickens and contains more polyphenols with increasing elevation. This process appears to be responsible for the reduced permeability of the seed coat. High germination temperatures reduce the gas solubility in water and, at the same time, increase polyphenol oxidation in the seed coat. The embryos of seeds collected at low elevation thus receive a reduced O2 flux. When high temperature is applied to seeds from high elevation, the O2 flux is drastically reduced because of the thicker seed coat and increased levels of oxidizable polyphenols.There is a high correlation between germination and the mean of the average daily temperature for the 30 days preceding harvest, high temperature prior to harvest being correlated with high germination.Progenies of plants transferred from high to low elevation (and the inverse) show the direct influence of the new environment on the seed coat inhibition of germination.
Genera coelomycetum. XIX. Discosiella, a lichenized mycobiont
Authors: Raj T. R. Nag
Published: April 2011

New information strongly suggests that species of the anamorph-genus Discosiella are mycobionts of lichens. Discosiella is revised and four species: D. cylindrospora, D. diospyri comb. nov. (≡ Ceuthospora diospyri), D. indica comb. nov. (≡ Shanoria indica), and D. novae-zelandiae sp. nov. are fully described and illustrated. Strigula nitidula is regarded as the teleomorph of D. indica. An unnamed species of Strigula is the teleomorph of D. cylindrospora.
Ergot alkaloid biosynthesis by isolates of Balansia epichloë and B. henningsiana
Authors: Bacon Charles W. , Porter James K. , Robbins Joe D.
Published: April 2011

Two endophytic clavicipitaceous fungi, Balansia epichloë and B. henningsiana, were isolated from several grasses, cultured on laboratory media, and assessed for their ability to produce the major ergot alkaloids agroclavine, chanoclavine (I), ergonovine, and ergonovinine. Data indicated that the ability of these two species of fungi to biosynthesize ergot alkaloids was host related. All isolates of B. epichloë from smut-grass (Sporobolus poiretii) and 59% of the isolates of B. henningsiana from broom-sedge (Andropogon virginicus) produced the major alkaloids in culture. All isolates of B. epichloë from Eragrostis secundiflora and E. hirsuta, and all isolates of B. henningsiana from Panicum tenerum failed to produce alkaloids. The total yield and chemical species of individual alkaloids varied among isolates from a sampling site.
Leaf free space analysis and vein loading in Cucurbita pepo
Authors: Madore Monica , Webb John A.
Published: April 2011

To determine the role of the apoplast in the loading of the minor veins of Cucurbita pepo L., leaves were examined either for the ability to release selectively the transport sugars, sucrose and stachyose, from the metabolic space (MS) to the free space (FS) or to accumulate selectively exogenously fed transport sugars from the FS into the minor veins. FS extracts collected by vacuum infiltration and centrifugation of specially trimmed leaves were found to contain all sugars also present in ethanol extracts of the MS of the same leaves, but in amounts two orders of magnitude lower. Similarly, 14C activity in FS extracts from 14CO2-labelled leaves, which was distributed between all sugars, amino acids, and organic acids also found labelled in the MS, was nearly three orders of magnitude lower than in MS ethanol extracts. No excess of the transport sugars was evident in FS extracts. When 14C-labelled sucrose, stachyose, or galactose (all 1–2 mM) were infiltrated into the FS a rapid accumulation of these sugars into the mesophyll was apparent, as all sugars were rapidly interconverted into the various sugars normally found labelled in the MS after exposure of leaves to 14CO2. However, while leaves exposed to 14CO2 translocated label predominantly in the form of [14C]stachyose, label in exogenously fed leaves was translocated predominantly as [14C]sucrose, irrespective of the nature of the fed sugar. Exogenously fed transport sugars did not therefore appear to be taken up directly into the minor veins from the FS.The absence of significant levels of transport sugars in the FS as well as the failure of C. pepo leaves to load any appreciable amount of exogenously supplied [14C]stachyose, the predominant transport sugar in this species, would tend to preclude both a selective release of transport sugars into the apoplast and a selective uptake of transport sugars from the apoplast into the minor veins. A completely symplastic pathway for minor vein loading in C. pepo leaves therefore remains a possibility.
Biomass, nutrient distribution, and net production in alpine communities of the Kluane Mountains, Yukon Territory, Canada
Authors: Grier Charles C. , Ballard T. M.
Published: April 2011

Biomass and nutrient distribution and aboveground net primary production were determined for two communities growing at 1600 m elevation and five communities growing at about 2000 m elevation in the alpine zone of the Kluane Ranges, Yukon Territory, Canada. Living biomass accumulations ranged from 183 to 1350 g/m2, whereas total organic matter accumulations ranged from 2126 to 51120 g/m2. Nutrient distribution in general reflected organic matter distribution. Highest nutrient concentrations were in leaves and fine roots. Aboveground net primary production ranged from 18.3 to 185.5 g/m2. Primary production appeared to be related most to moisture during the growing season and temperature regimes.
Xylogenèse chez les Dicotylédones arborescentes. II. Evolution avec l'âge des modalités de la réactivation cambiale et de la xylogenèse chez le Hêtre et le Chêne
Authors: Lachaud Suzanne
Published: April 2011

Cambial reactivation and xylogenesis have been studied in young oaks (ring-porous trees) and young beeches (diffuse-porous trees). A basipetal gradient of xylogenesis can be observed in the majority of young oaks (5 to 10 years old) and in all young beeches (8 to 14 years old), during the 1st weeks following cambial reactivation. Cambial reactivation proceeds downwards in young beeches at the rate of about 6 cm a day. The study of cambial cell différenciation in young disbudded trees shows that buds are indispensable for reactivation in beeches, whereas they are not necessary in the case of oaks, except for their 1st-year shoots. Decapitation and disbudding prevent xylogenesis in young beeches, but they do not in the lowest part of old beeches. The simultaneous cambial reactivation, which occurs in oak axes more than 1 year old, appears between the 15th and the 30th year in beech trunks; it bears no relation to the growth of terminal buds and to the basipetally progressing cambial reactivation of the branches.
Effects of water stress on photosynthesis in relation to diurnal accumulation of carbohydrates in source leaves
Authors: Bunce James A.
Published: April 2011

Net photosynthetic rates, stomatal and mesophyll conductances to CO2 uptake, water soluble and total nonstructural carbohydrates contents, specific leaf weights of fully expanded source leaves, and elongation rates of rapidly expanding leaves were measured on 2 days during a period of water stress in soybean and sunflower plants in a controlled environment. Compared with control plants, elongation rates of expanding leaves and translocation rates of dry weight from source leaves in the light were more reduced by stress than were net photosynthetic rates of source leaves. Over the 8-h light period, the dry weight increase of source leaves was up to 23 mg dm−2 (1.5 × control) higher in stressed plants, but was not in all cases higher in stressed than control plants. In stressed plants a smaller fraction of the increase in dry weight in source leaves in the light was in nonstructural carbohydrates. At the end of the light period, water soluble and total nonstructural carbohydrates were up to 9 mg dm−2 higher in stressed than control leaves in sunflower, but were not higher in soybean. No differences in carbohydrate contents at the end of the light period were found in sunflower between the 2 days of stress, although stress became more severe in terms of lower rates of photosynthesis, translocation, and leaf elongation. The approximately threefold reductions in net photosynthetic rates in stressed leaves were related to both lower stomatal and lower mesophyll conductances. Mesophyll conductances of stressed leaves were not significantly correlated with water soluble carbohydrate content, total nonstructural carbohydrate content, or specific leaf weight in either species.
Potassium involvement not demonstrated in stomatal movements of Paphiopedilum. Qualified confirmation of the Nelson–Mayo report
Authors: Outlaw Jr. William H. , Manchester Jill , Zenger Vincent E.
Published: April 2011

Guard cells of Paphiopedilum leaves lack chlorophyll, a unique condition. Whether potassium fluxes are involved in stomatal movements is controversial. In attempting to resolve this controversy, we have dissected individual guard cell pairs from frozen-dried epidermal peels of three species. These samples were assayed for potassium using quantitative histochemical methodology. We were unable to detect a correlation between guard cell potassium content and stomatal aperture size. With certain reservations, these results indicate potassium is not the major osmoticum causing stomata of these species to open.
Laetisaria and Limonomyces species (Corticiaceae) causing pink diseases in turf grasses
Authors: Stalpers J. A. , Loerakker W. M.
Published: April 2011

Three pink species of Corticiaceae (Basidiomycetes) growing on living grasses are described: Laetisaria fuciformis, the causal organism of the red thread disease and two species classified in the new genus Limonomyces: Limonomyces roseipellis sp. nov. and Limonomyces culmigenus comb. nov. The morphology and disease symptoms of these species are described and their taxonomy discussed.