bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultrastructural and cytochemical studies of zoospores, cysts, and germinating cysts of Phytophthora palmivora
Authors: Bimpong Christina E. , Hickman C. J.
Published: September 2008

Studies have been made of the ultrastructure and cytochemistry of zoospores, cysts, and germinating cysts of Phytophthora palmivora. The bulk of the zoospore cytoplasm is occupied by lipid bodies, crystalline vesicles containing lipid plus other unknown material(s), and granular vesicles containing protein. During a 6-h motile period after zoospore release no noticeable changes occur in crystalline and granular vesicles or in lipid bodies. Granular vesicles are retained if encystment is caused by centrifugation or agitation, but few remain when zoospores encyst under undisturbed conditions. Cysts begin to germinate 15 min after encystment is complete. Granular vesicles begin to disappear 30 min after germination starts and the process is complete 60 min later. Crystalline vesicles and lipid bodies also begin to disintegrate 30 min after germination begins, resulting in osmiophilic network-like breakdown products. The breakdown of these products increases with time but is not complete 90 min after germination.
The invertase complement of cold-hardy and cold-sensitive wheat leaves
Authors: Roberts D. W. A.
Published: September 2008

The invertase (EC 3.2.1.26) of leaves from two cultivars of wheat (Triticum aestivum L. emend Thell. ssp. vulgare), Rescue (cold-sensitive) and Kharkov 22 MC (cold-hardy), grown at 20 °C (non-hardening conditions) and at 4–6 °C (cold-hardening conditions), has been separated into three different forms by gel filtration. In Rescue wheat, the complement of different forms of invertase from the leaves did not change greatly when the plants were grown at different temperatures. In Kharkov 22 MC grown at 20 °C, the quantity of the medium-molecular-weight form of invertase was much greater than that of the high-molecular-weight form of invertase; however, when this variety was grown at 4–6 °C, the relative quantities of these two forms of invertase were reversed. This change in the ratio of the different forms of invertase in the leaves appears to be associated with the process of cold-hardening.
Orseillin BB and crystal violet: a staining technic for paraffin sections and water mounts of fungi
Authors: Corlett Michael , Kokko E. G.
Published: September 2008

A saturated solution of orseillin BB in 3% acetic acid and a 1% aqueous solution of crystal violet, in series, are an excellent differential staining combination for sections of ascomycetous fructifications. The technic stains a wide variety of fungus and host cells, often producing a vivid polychromatic effect and revealing considerable morphological and cytological detail; it is appropriate for microscope slides both of unfixed material mounted in water and of picric-acid-fixed paraffin sections.
Peroxidase, polyphenoloxidase, and endopolygalacturonate transeliminase activity in different tissues of sugar beet infected with Phoma betae
Authors: Bugbee W. M.
Published: September 2008

The storage rot pathogen Phoma betae normally attacks the exposed stem pith of harvested sugar beets (Beta vulgaris L.) before invading adjacent stem and taproot tissues. A comparison of rotted and sound tissues of nonselected roots showed that increased polyphenoloxidase activity occurred in rotted stem tissue, but peroxidase decreased. Endopolygalacturonate transeliminase (endoPGTE) was more active in rotted pith tissue compared with other rotted tissue. Comparison of rotted tissue from resistant and susceptible inbreds showed the greatest difference in oxidase activity occurred in resistant taproot tissue. Higher polyphenoloxidase activity was associated with resistant stem tissue of nonselected roots when catechol was the substrate rather than chlorogenic acid. Phoma betae growth in liquid culture was inhibited more by oxidation products of catechol than by those of chlorogenic acid. Peroxidase activity was associated with resistance only in stem and taproot tissue of inbreds. Endo PGTE activity was low in infected resistant tissue. When isolated cell walls of nonselected sugar beets were used as the carbon source, P. betae grew more and endo PGTE activity was greater on cell walls from pith than cell walls from adjacent stem or taproot tissue after 6 days incubation.
Wound regeneration in the lamina of magnoliaceous leaves
Authors: Tucker Shirley C.
Published: September 2008

Reparative tissue was observed around healed natural wounds in leaves of 53 species of 9 of the 12 magnoliaceous genera: Aromadendron, Elmerrillia, Kmeria, Liriodendron, Magnolia, Manglietia, Michelia, Paramichelia, and Talauma. Additional evidence was obtained from wounding experiments carried out on attached leaves of two evergreen species, Magnolia grandiflora and Michelia figo. Regeneration was studied over a 6-week period. Evergreen leaves produced more abundant regenerative tissues than deciduous leaves; a narrow-to-broad periderm forms consistently in all evergreen magnoliaceous leaves around wounds, but wounds in the deciduous species invoke little or no periderm development. The healing process in these leaves consists of three steps: (1) cells die along the wound, and cells immediately adjacent become physiologically altered; (2) a callus forms by randomly oriented cell divisions throughout mesophyll, vein sheath, and (in most species) epidermis; and (3) a periderm eventually forms in the band of callus parallel to the wound. The complete process takes 4 to 6 weeks in the evergreen magnoliaceous plants studied. The differences in healing processes are contrasted between evergreen and deciduous leaves. Of special interest is the observation that guard cells of mature leaves in several taxa dedifferentiate and undergo division in the area of wound repair.
Observations on chytridiaceous parasites of phanerogams. XXIV. The epibiotic stage of Physoderma
Authors: Sparrow Frederick K.
Published: September 2008

The development of the epibiotic sporangium from resting spore zoospores of 18 Physoderma spp. has been examined to determine whether or not this stage can assist in delimiting groups of species within the genus when associated with other morphological characters. It was found that 11 entities had a "bilateral" type of sporangial development and 7 had a "unilateral" type. These types could not be associated with other morphological features of either epibiotic or endobiotic stages to produce taxonomic groupings. Type of epibiotic sporangial development, at the moment, is regarded as simply another morphological parameter.
Virulence changes in Puccinia graminis f. sp. tritici in Canada
Authors: Green G. J.
Published: September 2008

Virulence differences on “standard” Puccinia graminis tritici differentials are not chronologically related and do not form evolutionary series. Chronologically related virulence differences between strains of "standard" race 15B-1L on "single-gene" differentials form an evolutionary series of single-step virulence changes, while virulence differences between strains of "standard" race groups 11-32, 17-29, and 56-125 do not. Most virulence changes were from avirulence to virulence, or vice versa, but on varieties with resistance genes Sr7a and Sr11 intermediate virulence occurred, which suggests that there was more than one kind of genetic change. There was no indication of an overall increase or decrease in the number of virulence genes present in all races, although virulence on genes Sr7a and Sr5 has increased. Random virulence changes on single host resistance genes, probably the result of mutations, seem to occur frequently and may be the most common kind of change in North America under present conditions. They permit the rust to overcome single-gene resistance, but they are not very effective in overcoming complex resistance. The stability of complex resistance in North America suggests that other processes capable of producing a wider range of variability occur infrequently in nature.
Nitrogen fixation in soils of Truelove Lowland, Devon Island, Northwest Territories
Authors: Stutz R. C. , Bliss L. C.
Published: September 2008

Biological nitrogen fixation was studied on Truelove Lowland, Devon Island, N. W. T., in three different habitats. Raised beach ridges, resulting from postglacial uplift, form well-defined xeric habitats, which are dominated by dwarf shrubs and cushion plants. Hummocky sedge meadows with associated mosses and forbs comprise the second intensively studied habitat. Waterlogged wet sedge meadows with moss were studied less intensively.Nitrogen fixation was estimated using acetylene-reduction assay. Incubation temperatures were moderated by burying the jars in soil pits (10 cm) on site.Available nitrogen was determined by microkjeldahl analysis of KCl soil extracts.Symbiotic nitrogen fixation by vascular plants is nil on Truelove Lowland. One lichen species, Peltigera aphthosa, reduced acetylene (5.1 μμmol∙mg−1∙h−1). Nostoc commune, a prominent blue-green alga on meadow soils, reduced acetylene at a rate 10 times that of P. aphthosa. An estimated 30 and 7 mg N∙m−2∙year−1 was fixed by bacteria and soil algae in beach ridge soil in 1971 and 1972 respectively, and 380 and 120 mg N∙m−2∙year−1 was fixed in meadow soils in the same years.
Changes in metabolic reserves and enzyme activities during zoospore motility and cyst germination in Phytophthora palmivora
Authors: Bimpong Christina E.
Published: September 2008

Lipids measured as acyl glycerides and free fatty acids provided the major energy source during a 6-h motile and a 2-h germination period in zoospores and cysts, respectively, of Phytophthora palmivora. Carbohydrates and proteins decreased slightly during the 6-h motile period but increased significantly during germination. Specific activity of isocitrate lyase decreased both during zoospore motility and cyst germination. Only trace amounts of malate synthase activity were detected in zoospores and cysts. The activities of both NAD-isocitrate and malate dehydrogenases increased slightly, while those of NADP-isocitrate and succinate dehydrogenases decreased during the 6-h motile period. During the 2-h germination period the specific activities of NAD- and NADP-isocitrate, malate, and succinate dehydrogenases increased. It appears that during the motile stage the glyoxylate cycle provided more metabolites for the Krebs cycle than it did during germination.
Observations on the growth and morphology of Emerson's Saprolegnia sp. 47-15a
Authors: Neish Gordon A.
Published: September 2008

Emerson's Saprolegnia sp. 47-15a most closely resembles Saprolegnia ferax (Gruith.) Thuret. Temperature is an important factor in determining the morphology of the isolate. At 21C oogonium development is inhibited and gemma production is enhanced. At 14C or less, oogonia are produced abundantly and gemma production is inhibited. The linear growth rate of the isolate doubles as the temperature doubles within a temperature range of 3 to 21C.
Anther-derived haploids of the African violet
Authors: Hughes Karen W. , Bell Sandra L. , Caponetti James D.
Published: September 2008

Anther culture of the African violet, Saintpaulia ionantha (Gesneriaceae), produces haploid plants directly from anthers at a low frequency. Successful anther culture for either this species or family has not been previously reported. Anthers between 3 mm and 5 mm in diameter are most suitable for culture. Root formation must be induced by the addition of indoleacetic acid to the medium.
Bestblock: optimizing grid size in biogeographic studies
Authors: Phipps J. B.
Published: September 2008

This paper describes a method for optimizing grid scale when presence–absence records are to be used in a numerical biogeographic study. Optimality is held to reside at that size of grid square which maximizes the number of matches in presence–absence comparisons over all pairwise species comparisons. The paper is illustrated with an example from Turkish poppies (Papaver).
On the copper content of some northern conifers
Authors: Stone Earl L. , Timmer Victor R.
Published: September 2008

New analyses of pine, spruce, fir, larch, and red maple tissue from the Tantramar Copper Swamp, New Brunswick, fail to confirm the exceptional high copper contents previously reported from this location. Foliar contents did not differ from those of nearby controls, and contents in 1st- and 2nd-year twigs were only two to three times higher than in controls, still within the normal range of values in the literature. In contrast, bulk samples of fine roots from the swamp contained over 2000 ppm Cu. Parallel comparisons of hemlock growing on Cu-enriched mineral soils from Long Island, New York, revealed that root Cu increased linearly with extractable soil content, whereas foliar Cu was unaffected. Thus, it appears that roots and twigs may be better indices of plant Cu status than foliage.
Plant species diversity in ravines of the southern Finger Lakes region, New York
Authors: Glenn-Lewin David C.
Published: September 2008

Vascular plant species diversity in the ravines of the southern Finger Lakes followed the ravine-side gradient and vegetation characteristics described by Lewin (1974). Bottom and lower-slope mesophytic communities were very rich in species, middle-to-upper hemlock stands were very poor in species, while the upper oak stands were again somewhat richer. Dominance followed an inverse pattern, being lowest in the low, mesophytic stands and high in the hemlock stands. The amount of hemlock in the canopy appeared to have an effect on diversity.
Observations on Canadian birches, Betula cordifolia, B. neoalaskana, B. populifolia, B. papyrifera, and B. × caerulea
Authors: Grant W. F. , Thompson B. K.
Published: September 2008

Ten morphological characters have been examined from 455 collections of B. papyrifera Marsh., 95 collections of B. cordifolia Regel, 56 collections of B. populifolia Marsh., 64 collections of B. neoalaskana Sarg., and 70 collections of B. × caerulea Blanch. taken from their ranges within Canada. The somatic chromosome numbers were found to be 70, 84, and more rarely 56 (possibly hybrids) for B. papyrifera, 28 and more rarely 42 and 56 for B. cordifolia, and 28 for B. populifolia, B. neoalaskana, and B. × caerulea. Observations on juvenile characters and growth rates indicated that it is possible to distinguish these taxa at an early age. Comparison of the characters on an interprovincial basis within species revealed no significant differences in B. populifolia (P < .05). However, significant differences were observed in one or more characters from the other species. No significant differences were found between species when B. papyrifera was either sympatric or allopatric with B. cordifolia and B. populifolia; when B. cordifolia was sympatric but B. populifolia was not; and when B. populifolia was sympatric but B. cordifolia was not. A canonical analysis of the New Brunswick data incorporating the 10 characters indicated clear distinctions among B. papyrifera, B. cordifolia, and B. populifolia and provided further evidence that B. × caerulea is a hybrid of B. populifolia and B. cordifolia. Considerable introgression of B. caerulea with B. populifolia was noted in these data.
Effect of air temperature on the flowering date of dogwood (Cornus florida)
Authors: Reader R. J.
Published: September 2008

The summation of air temperatures above 2.2 °C for a 6-week period before flowering explained most of the annual variation in the flowering date of dogwood (Cornus florida L.) at Wauseon, Ohio. The same total was a fairly accurate predictor of flowering date throughout dogwood's native range, which suggests that geographical variation in flowering time is environmentally rather than genetically controlled. Results of the current study are inconclusive concerning spatial variation in the probability of frost on the date of flowering.
Fungal antisporulant activity of a complex lipid fraction extracted from pea seeds
Authors: Pfleger F. L. , Harman G. E.
Published: September 2008

A substance was isolated from dry whole pea seeds (Pisum sativum 'Alaska') that inhibited sporulation, but not growth, of Alternaria alternata, Aspergillus ruber, Ascochyta pisi, Phyllosticta antirrhini, Rhizoctonia solani, Nectria haematococca var. cucurbitae, and Fusarium oxysporum f. sp. pisi race 2. The substance had no effect on sporulation or growth of Aphanomyces euteiches. The mean effective dose (ED50) of the partially purified material was 30 μg/ml when tested against Alternaria alternata. The partially purified substance was soluble in petroleum ether, chloroform, and hexane but formed an emulsion in water. The partially purified material contained amino acids, lipids, phosphorus, and carbohydrate. Its molecular weight was in excess of 14 000. These properties indicate that it is a complex lipid with properties similar to many proteolipids.
A new species of Ochroconis isolated from pelagic tar fragments
Authors: Wellman A. M.
Published: September 2008

A new species of Ochroconis with muriform conidia, isolated from tar fragments collected in the Atlantic Ocean, is described.
Fungal succession on aspen poplar leaf litter
Authors: Visser Suzanne , Parkinson D.
Published: September 2008

Fungi from the litter, fermentation, and humus (LFH) layers of a mature aspen tree stand were qualitatively assessed using the soil-washing method and quantitatively assessed using the agar-film technique. Fungi were isolated and identified at two sampling times, June and October. From the isolation data obtained, it was concluded that the pattern of fungal succession in aspen litter followed the general succession schemes proposed by Garrett (1963) and Hudson (1968). The parasites on living aspen leaves included a sterile dark organism and Pleurophomella spermatiospora, while the common primary saprophytes, thought to be existing on sugars and simple carbon compounds in the leaf, included Penicillium janthinellum, Cladosporium spp., and Aureobasidium pullulans. The secondary saprophytes, such as the cellulose and lignin decomposers and associated fungi, were dominated by Penicillium syriacum, Trichoderma spp., Mucor spp., Volutella ciliata, Cylindrocarpon spp., and Phoma spp.The quantitative study revealed that the fungal length and biomass per gram dry weight of litter in each layer studied were much higher in October than in June. The amount of fungal mycelium in the humus in each of the two sampling times was not significantly different. The difference in standing crop of mycelium from June to October in the aspen LFH horizon was estimated to be at least 58 g wet mycelium per square metre of dry litter.
Ontogeny of the protophloem fibers and secondary xylem fibers within the stem of Coleus. I. A light microscope study
Authors: Pizzolato Thompson Demetrio , Heimsch Charles
Published: September 2008

The maturation of the primary phloem fibers and secondary xylem fibers in Coleus stems was studied using Nomarski optics. The phloem fiber initials differentiate from the procambium at the same time as the earliest sieve-tube elements and companion cells. Lateral expansion and intrusive growth by the fiber primordia, which obliterate most of the other primary phloem cells, continue until the young fibers begin forming secondary walls. The single nucleus divides a few times and cytokinesis occurs by the formation of septa. After a few septa are formed, cytokinesis may not follow additional mitoses. The cell wall continues to thicken, and the septa may develop secondary layers. Although there is some nuclear degeneration, the fibers remain alive after maturity. During their maturation small groups of protophloem fibers in the corner sectors become consolidated into fewer, larger groups by the crushing of intervening cells. The maturation of xylem fibers is more rapid than that of phloem fibers. Secondary wall thickening begins in the second cell from the cambium. After wall thickening ceases, the single fusiform nucleus undergoes mitosis followed by septum formation. The septate wood fiber is alive at maturity.
The hepatic flora of Alberta: a phytogeographical analysis
Authors: Bird Charles D. , Hong Won Shic
Published: September 2008

A survey of the literature combined with field studies and the reexamination of many historical collections reveals that the hepatic flora of Alberta is composed of 114 taxa, consisting of 26 families and 46 genera. Two species. Gymnomitrion corallioides and Scapania mucronata, are reported as new to the province. Two species are excluded from the hepatic flora as they have been incorrectly attributed to Alberta. Twenty-five taxa have been designated as hypothetical for the province as no valid voucher specimens have been located. Most (109) of the 114 taxa present are Circumpolar in distribution, 4 are American, and 1 is Amphi-Atlantic. The range of most (98) of the Alberta species includes the Boreal Forest and forested areas in the mountains; however, 57 of these species also occur in Arctic and in Alpine regions, and 22 of them occur south into temperate areas. Only a few species have other distributions: 10 are Arctic Alpine. 3 are Cordilleran, 3 are Temperate, 2 are Boreal, and 1 is Boreal-Temperate. One hundred and two species have been found in the Rocky Mountains, 59 in the Boreal Forest, 7 in the Cypress Hills, 6 in the Aspen Parkland, and 3 in the Prairies.
On the specificity of sucrose for the growth of excised tomato roots
Authors: Weston Geoffrey D.
Published: September 2008

The growth and respiration rate of excised tomato roots was determined using the following sugars as substrate: sucrose, maltose, raffinose, glucose, α-methylglucoside, fructose, β-methylfructoside, cellobiose, trehalose, melibiose, melezitose, turanose, palatinose, and inulobiose. The ability of these sugars to inhibit the growth of roots in sucrose and the ability of the roots to hydrolyze the oligosaccharides were also determined. The results are discussed in terms of the possible limiting factors for growth on different substrates.
Effect of gibberellic acid on growth and photosynthesis in Abies balsamea
Authors: Little C. H. A. , Loach K.
Published: September 2008

The hypothesis that exogenous gibberellic acid (GA3) increases height growth in tree species partly because it stimulates the rate of net photosynthesis (PN) was investigated in the conifer balsam fir (Abies balsamea L.). In long-term experiments, the normal growth pattern of 4- and 5-year-old potted trees was changed by GA3 applied in both an aqueous soil drench (20 mg per tree, thrice weekly; or 50 mg per tree, twice weekly) and a foliar spray (1000 ppm, weekly) for about 3 months. Effects included increased longitudinal and radial growth in the leader and longest lateral in the uppermost whorl, enhancement of shoot apical dominance, increased needle length, and decreased root weight – top weight ratio. Nevertheless, the Pn and productive capacity of the current and 1-year-old needles in the GA3-treated and control trees were the same, measured during and at the end of the treatment period. In short-term experiments, the 1000-ppm GA3 spray did not affect PN of current-year needles, measured 3 h up to 7 days after one or two applications. PN of current-year cuttings also was not altered by feeding through the basal end (1) 0.25, 2.5, 25, or250 ppm GA3 for 4 h; or(2) 10 or 100 ppm GA3 for24 h. Feeding25 or250 ppm GA3 for 48 h through the distal portion of an attached, current shoot decreased PN in the proximal portion. Collectively, the results indicate that exogenous GA3 increases height growth in balsam fir by altering the normal distribution of photosynthate, not through increasing photosynthate production.
Additions to the genus Delitschia
Authors: Luck-Allen E. Robena , Cain Roy F.
Published: September 2008

Species included in the taxon Delitschia are loculoascomycetes with dark, two-celled ascospores. Each cell of the ascospore is provided with an elongated germinal slit and each spore is surrounded by a hyaline gelatinous layer. A total of 46 species of Delitschia are recorded in an analytical key. Descriptions and illustrations are provided for the following 26 new species of Delitschia found on diverse substrata of herbivores from Canada, United States, and Mexico: D. anisomera, D. anomala, D, arestospora, D. chodocola, D. chorizomera, D. chrysina, D. crinita, D. didymastra, D. didymella, D. flavida, D. hexaspora, D. illinoisensis, D. intonsa, D. lachnothecium, D. lamprorhynchia, D. limasepta, D. megatetraspora, D. melanotricha, D. nephrospora, D. oligospora, D. pachylospora, D. simulans, D. tetrasporella, D. tomentosa, D. variispora, D. xanthodera.The remaining 20 species represent established and recognized taxa; for 11 of these, descriptions are vague and (or) inadequate. Species descriptions have been emended and illustrations are provided for 11 species: D. canina Mout., D. chaetomioides Karst., D. consociata Mout., D. excentrica Griff., D. furfuracea Niessl, D. marchalii Berl. & Vogl., D. niesslii Speg., D. perpusilla Speg., and D. polyspora Griff. Data are provided for one recently published species, D. myriaspora Breton & Faurel. For nine well-known species included in the key there are no descriptions provided; however, literature citations and photographs of type species are included. These species are as follows: D. araneosa Cain, D. didyma Auersw., D. gigaspora Cain, D. griffithsii Cain, D. leporina Griff., D. leptospora Oud., D. timagamensis Cain, D. vulgaris Griff., and D. winteri Phill. & Plowr.
Chimeras, hyperplasia, and hypoplasia in frost burls induced by low temperature
Authors: Zalasky Harry
Published: September 2008

The process of frost burl formation is explained on a cellular and somatic level. Somatic changes in cells consisting of fragmentation, loss of translocatable centromeres, formation of micronuclei. and numerical changes and rearrangement of chromosomes lead to the establishment of a chimeral condition induced by low temperatures. Chimeral tissue is characterized by deformed cells with complete and incomplete cell plates, hyperplasia, hypoplasia, senescence of storage cells, and realignment of tissues.
Contribution à la tératologie des Chèvrefeuilles et au problème des fusions. III. Association de cymules biflores par gamophyllie ontogénique
Authors: Lamond M. , Vieth J.
Published: September 2008

In this paper, the authors describe the main features of more than 100 teratological samples spontaneously produced, during the past 5 years, by the hybrid No. 6488-37 of the Montreal Botanical Garden's collection of honeysuckles. The unusual appearance of all these specimens is due to the union, by gamophylly, of flowering twigs, which are most often inserted in foliar axils vertically separated by a well-developed internode.The constant position of the united flowering twigs' insertion point on the main axis of all these samples, the normal or subnormal morphological and anatomical structure of those twigs, and the very small junction area (maximum length 500 μm) of their fused leaves, as also the relative initial position, and (or) the time interval between the respective periods of initiation of the united organs, indicate (1) that these gamophyllies undoubtedly have an ontogenetic or postgenital origin and (2) that the adhesion of the fused foliar areas must have occurred during the intensive intercalary growth of the flowering branches.The histocytological study of areas of gamophylly of the samples shows also that the intimate fusion of the leaves' parts, accidentally brought together, is generally accompanied by a local cellular dedifferentiation and an intensive cell proliferation. The first of these phenomena would correspond in a way to a contact allergy, whereas the second would result from injuries.
Inhibition of phosphoenolpyruvate carboxylase from C4 plants by malate and aspartate
Authors: Huber S. C. , Edwards G. E.
Published: September 2008

The activity of phosphoenolpyruvate carboxylase in leaf extracts of C4 plants has been shown to be inhibited by the C4 acids malate and aspartate. The magnitude of inhibition observed with phosphoenolpyruvate carboxylase from Digitaria sanguinalis leaves was dependent on the pH of the assay mixture and the concentration of phosphoenolpyruvate (PEP), Mg2+. and the C4 acid inhibitor. The percentage inhibition decreased with increasing pH up to 8.5. At rate-limiting concentrations of phosphoenolpyruvate the pH optimum of the enzyme was 7.8, whereas the enzyme partially inhibited by malate or aspartate had a pH optimum of roughly 8.3. Malate and aspartate inhibited the enzyme by increasing the apparent Km for phosphoenolpyruvate without altering the maximum velocity, such that inhibition was greatest at rate-limiting concentrations of PEP but was not observed at saturating (3 mM) substrate levels. Glucose-6-P. an activator of PEP carboxylase, decreased the apparent Km for PEP and reversed the inhibition by malate and aspartate. Inhibition was also dependent on the concentration of Mg2+. At 1 mM Mg2+, 1 mM malate caused 60% inhibition, but at 5 mM Mg2+ the inhibition was reduced to 15%. Mg2+ at concentrations from 1 to 5 mM had no effect on the apparent Km for PEP. With Sephadex extracts of PEP carboxylase from leaves of D. sanguinalis, malate and aspartate were equally inhibitory, with roughly 2 mM levels required for 50% inhibition. Both malate and aspartate were inhibitory with PEP carboxylase extracted from leaves of a variety of C4∙ but not C3∙ plants. The significance of the observed inhibition and activation of PEP carboxylase by metabolites is discussed in relation to C4 photosynthesis.
Relations entre bourgeons dans les plantes inoculées avec Corynebacterium fascians
Authors: Roussaux Jean , Hoffelt Michèle
Published: September 2008

In witches' brooms induced by C. fascians ((Tilford) Dowson) after a systemic infection or a local infection at leaf axillae, no mutual inhibition is observed between shoots stimulated by bacteria. The growth of these abnormal shoots is reduced and finally stops. This is not determined by a trophic competition but by an accumulation of inhibitors in buds. During their development witches' brooms inhibit healthy buds of the host by a deviation of nutrients from their normal destination, as is shown by the repartition of 32P in inoculated plants.
Effect of ammonium on growth of plant cells (Ipomoea sp.) in suspension cultures
Authors: Rose Dyson , Martin S. M.
Published: September 2008

Maintenance of the ammonium level in batch cultures of a plant cell line initiated from Ipomoea root tissue resulted in cells with a higher nitrogen content and a greater total accumulation of nitrogen in the cells. Utilization of nitrate was not suppressed. The increased supply of ammonium did not, by itself, increase the yield of dry cells, but it did permit a twofold or greater increase in cell yield when sucrose was added subsequently.Supplementary feeding of ammonium and sucrose to a batch culture that had exhausted the initial supply of ammonium rapidly returned the cells to a state of high nitrogen content, favored further utilization of nitrate, and greatly increased cell yield.These results are discussed in terms of growth phases. The presence of ammonium in the medium appeared to induce and maintain a growth phase characterized by a high nitrogen level in the cells. After the ammonium supply was depleted a second phase occurred, characterized by a rapid increase in dry weight without proportional accumulation of nitrogen. This second phase was not caused by a limiting rate of nitrate utilization, nor was it directly related to observed pH changes. We conclude that the two phases relate to the presence and absence of ammonium in the medium.
Ultrastructure, composition, and biogenesis of the encapsulation material surrounding the endophyte in Alnus crispa var. mollis root nodules
Authors: Lalonde Maurice , Knowles Roger
Published: September 2008

The encapsulation material surrounding the endophyte of Alnus crispa var. mollis Fern. root nodule was studied by means of a variety of staining methods in light and in electron microscopy. The enzymatic degradation of the capsular material was obtained and the degradation products were studied by thin-layer chromatography. The endophyte capsule was composed mainly of granular and fibrillar non-sulfated and de-esterified polygalacturonic acid or its salts. An endophyte pectic capsule was also demonstrated in 11 additional species of non-leguminous root nodules. Small secretory vesicles, containing electron-dense material similar to that of the endophyte capsule, occurred in free multivesicular bodies throughout the host cell cytoplasm. Ultrastructural observations are consistent with the view that these bodies migrate to the host membrane envelope surrounding the endophyte, fuse with it, and deposit the contents of the small vesicles toward the endophyte cell wall. These small secretory vesicles appeared to originate as blebs from cisternae tips; dictyosomes were abundant in the infected cortical cells. The possible significance of the pectic capsule in the host–endophyte nutritional interactions is discussed.
Variation in susceptibility of stored cabbage tissues to infection by Botrytis cinerea
Authors: Yoder O. C. , Whalen M. L.
Published: September 2008

Cabbage cultivars which differed in ability to withstand storage showed differential susceptibility to Botrytis cinerea. For a given cultivar, outer leaves on the head were less susceptible than inner leaves, thick areas on leaves were less susceptible than thin areas, and adaxial surfaces of leaves were less susceptible than abaxial surfaces. Uncontrolled variability in rate of decay was reduced by standardizing these parameters. Susceptibility was not related to the location of tissues within individual leaves and appeared to be independent of the dry matter content of tissues.
An ultrastructural study of 'phialospore' formation in Fusarium culmorum grown in continuous culture
Authors: Marchant Roger
Published: September 2008

The macroconidia of Fusarium culmorum can be produced in a semisynchronous way in continuous culture by manipulating the medium pH. Ultrastructure studies of conidiogenesis have shown that the macroconidia are not conventional phialospores, as has long been believed. The first and subsequent conidia are delimited by the fusion of vesicles in the peripheral cytoplasm in the apex of the conidiophore. The conidium wall, including the basal delimiting septum, is formed endogenously. At a late stage of development the expanding conidium ruptures the conidiophore wall and is released by an abscissional splitting of the basal septum. Internal septation of the conidium normally occurs after its release.
A quantitative investigation of symplasmic transport in Chara corallina. III. An evaluation of chemical and freeze-substituting techniques in determining the in vivo condition of the plasmodesmata
Authors: Fischer R. A. , MacAlister T. J.
Published: September 2008

We present data on a comparison of plasmodesmata in the nodal complexes of Chara corallina prepared for electron microscopy by chemical fixation of specimens at room temperature and those that have been freeze-substituted. The freeze-substitution technique was applied to intact nodal complexes with the internodal cells on either side intact and showed that most plasmodesmata in the cell walls joining a nodal cell with an internodal cell were free of any occluding substance. We feel that the nonoccluded plasmodesma is the in vivo condition and that previous results using chemical fixation at room temperature where occlusions were reported in Nitella translucens and Chara corallina are artifacts of preparation.
Etude ultrastructurale des interactions hôte–parasite. I. L'hétérosporiose de l'Iris
Authors: Delon R. , Mangenot F.
Published: September 2008

not available
Ultrastructural alterations observed in isolated apple leaf cuticles
Authors: Hoch H. C.
Published: September 2008

The ultrastructural integrity of adaxial apple leaf cuticles was studied after their isolation from subjacent leaf tissues by several widely used procedures. Cuticles isolated with pectinase and (or) cellulase appeared most similar to the control, non-isolated cuticles. Cutin-embedded microfibrils as well as the lamellar structure of the cuticles were preserved. Cuticles isolated by the zinc chloride – HCl method likewise retained the lamellar structure, but most cutin-embedded microfibrils were dissolved away with this treatment. The ammonium oxalate – oxalic acid reflux procedure for cuticle isolation appeared to yield the most unnatural cuticles. Neither the lamellae nor the cutin-embedded microfibrils were well preserved. Furthermore, the cuticle was fragmented laterally, especially near the anticlinal walls. The importance of understanding what ultrastructural alterations occur during cuticle isolation is discussed with respect to transcuticular movement studies.
Cytology of exceptional development of the male gametophyte in Ophiorrhiza mungos
Authors: Philip Omana , Mathew P. M.
Published: September 2008

In Ophiorrhiza mungos L. the first division of the microspore nucleus gives rise to a large vegetative nucleus and a smaller generative nucleus. The vegetative nucleus subsequently fragments into a number of irregularly sized particles. These vegetative nuclear bodies move to and flow out of the three germ pores to form three spherical buds on the developing pollen grains. The 'pollen buds' are shed off from the pollen proper before dehiscence. The uninucleate grains readily germinate in vitro, and the single generative nucleus undergoes normal division to give rise to two sperm nuclei.
Dendrogram topology: nomenclature
Authors: Phipps J. B.
Published: September 2008

A method of nomenclature for dendrograms of differing topology, based on arranging them from the most asymmetric to the most symmetric, is proposed. It permits the unequivocal identification of each ith topologically different member of the series.
Endosperm abnormalities in Triticum–Secale combinations. II. Addition and substitution lines
Authors: Kaltsikes P. J. , Roupakias D. G.
Published: September 2008

The relationships between kernel shrivelling and endosperm, embryo, and antipodal development were investigated in wheat–rye addition and substitution lines.A positive relationship was established between mature kernel shrivelling and the number of aberrant endosperm nuclei during the first 10–15 divisions after fertilization. The presence of aberrant nuclei was associated with specific rye chromosomes; chromosomes 5R, 4R, 6R, 3R, and 1R, in descending order of importance, are responsible for aberrant nuclei induction. The short arm of 4R was without effect and a major effect was noted for the long arm of 6R. Thus, the main effect of chromosomes 4R and 6R was not associated with the short arm.No relationship could be established between kernel shrivelling (or number of aberrant endosperm nuclei) and (1) amount of heterochromatin, as revealed by Giesma staining, or (2) rate of antipodal degeneration. A tentative negative relationship was found between early starch deposition in the endosperm and kernel shrivelling.
Ultrastructure of the cuticular membranes of the developing wheat grain
Authors: Morrison I. N.
Published: September 2008

The distribution of cuticular membranes within the mature wheat ovule (Triticum aestivum L. cv. Heron) and the subsequent changes in these layers during grain development were investigated at the ultrastructural level. At anthesis, the inner epidermis of the pericarp and the outer integument are separated by two, thin, osmiophilic, cuticle-like lamellae. Similar osmiophilic boundaries, also double in nature, are evident between the outer and inner integuments and between the inner integument and the nucellar epidermis. By 7 days after anthesis, only the outer layer of cells of the inner integument and the nucellar epidermis are bounded by cuticularized layers, which, by this time, are recognizable as the developing outer and inner cuticles, respectively, of the mature caryopsis. Between 7 and 14 days after anthesis, the outer cuticle assumes a highly reticulate appearance in section and is delineated on the outside by a cutin layer, 90–120 nm in thickness. By 17 days both the outer and inner cuticles have attained maximum thickness, varying from 3.0 to 3.6 μm and 0.8 to 1.1 μm, respectively. Unlike the outer cuticle, the inner cuticle has no distinct internal substructure. The two are closely appressed by 4 weeks after anthesis and show no further ultrastructural changes.
Nuclear fusion in intergeneric heterokaryons. A note
Authors: Constabel F. , Dudits D. , Gamborg O. L. , Kao K. N.
Published: September 2008

Protoplasts from soybean cell cultures were fused with those from pea mesophyll by treatment with polyethylene glycol. After fusion about 20% of the cells were heterokaryons. Differential staining indicated that most of the heterokaryons contained one or two nuclei of each parent. Fusion of heterospecific nuclei during interphase appeared as an alternate way to the formation of hybrid cells.
P-type sieve-element plastids and betalains in Portulacaceae (including Ceraria, Portulacaria, Talinella)
Authors: Behnke H.-Dietmar , Mabry Tom J. , Eifert Imre J. , Pop Liliana
Published: September 2008

The presence of specific P-type sieve-element plastids is reported for 16 and betalains for 14 species of Portulacaceae. The micromorphology of sieve-element plastids and the presence of betalains support a closer relationship of the Portulacaceae to the Aizoaceae than to the Caryophyllaceae. Three genera, Ceraria, Portulacaria, and Talinella, previously treated as doubtful members of the Portulacaceae, cannot be distinguished from members of the Basellaceae on the basis of plastid subtypes since the two families have identical subtypes; however, the data do confirm their alignment with the Portulacaceae–Basellaceae family group.
Fungal self-parasitism in Saprolegnia megasperma
Authors: Nolan Richard A.
Published: September 2008

The phenomenon of self-parasitism in the aquatic phycomycetes has apparently been overlooked since it was first mentioned in the work of Klebs in 1899. This study documents fungal self-parasitism for the first time in Saprolegnia megasperma Coker (isolate 369A). The 369A isolate was grown for 48 h at 16 °C in shake cultures of a medium containing glucose, lactalbumin hydrolysate, phosphate, and micronutrients. The resulting vegetative growth was then transferred to shake-and-standing flasks at 16 °C and standing flasks at 4 °C containing either a dilute salts solution or double-distilled water to enhance the formation of both sexual and asexual structures. The results in both shake and standing cultures were comparable. When oogonia were produced in the absence of antheridial branches, the oospheres developed into normal oospores. When an antheridial branch was produced, an antheridial cell was never observed and the branch penetrated the oogonium via a pit and destroyed all or some of the oospheres (oospores?). This parasitic antheridial branch could reemerge from an oogonium via a pit and penetrate additional oogonia. The possible implications of self-parasitism for the relationship between S. megasperma and Saprolegnia unispora (Coker and Couch) Seymour are discussed.
Deuterium isotope effects in Nicotiana tabacum
Authors: Uphaus Robert A. , Blake Martin I. , Katz Joseph J.
Published: September 2008

The effects of increasing concentrations of heavy water (2H2O) on the growth, development, morphology, and transpiration patterns in Nicotiana tabacum L. were studied throughout the life cycle of the plant. The higher deuterium levels caused a marked reduction in size and flowering, together with extensive tissue necrosis. These observations are consistent with the literature on the effects of deuterium on plant development. The present study showed a deleterious effect of deuterium on alkaloid production, associated with heightened transpiration rates and decreased fractionation of carbon isotopes in photosynthesis. All of the observed effects are consistent with the established view of deuterium as a nonspecific chaotropic agent, whose effects are evident at every level of plant organization.
Fossil dinoflagellates: index to genera and species. Supplement 1
Authors: Lentin J. K. , Williams G. L.
Published: September 2008

Recently published fossil dinoflagellate taxa of and below the generic rank and not included in the authors' Fossil Dinoflagellates: Index to Genera and Species (published in 1973) are listed alphabetically. The dinoflagellates are classified as plants, so their taxonomy is governed by the provisions of the International Code of Botanical Nomenclature.
A key and annotated synopsis of the mosses of the northern lowlands of Devon Island, N.W.T., Canada
Authors: Vitt Dale H.
Published: September 2008

The moss flora of the northern lowlands of Devon Island (75°33′ N, 84°40′ W) is reported to consist of 131 species and 2 varieties. Forty-five of these are reported as new to the island. Sphagnum orientale L. Savicz. is reported as new to North America and Plagiobryum zierii (Hedw.) Lindb. and Polytrichum algidum Hag. & C. Jens, are reported as new to the Queen Elizabeth Islands.A key is given to the species and varieties, which is followed by a discussion of critical taxonomic and ecologic criteria for each species.
The zoospore of Rozella allomycis: ultrastructure
Authors: Held Abraham A.
Published: September 2008

The small (about 2 × 3.5 μm) zoospore of the obligately parasitic chytrid Rozella allomycis provides yet another ultrastructural variation on the basic pattern of posteriorly uniflagellate fungal zoospores. This zoospore contains the expected array of organelles: nucleus, mitochondria, "lipid sac" (including lipid globules, a microbody, and a backing membrane), kinetosome, and second centriole. Ribosomes are dispersed throughout the cytoplasm. In the disposition of its microbody Rozella resembles other chytrids, whereas in the occurrence and location of its gamma-like vacuoles it resembles certain blastocladialean fungi. Above all, the zoospore resembles that of Olpidium brassicae. Structural peculiarities of the zoospore include (i) bilateral symmetry; (ii) a helmet-shaped nucleus with extensive membranous projections which surmounts a large, spheroidal mitochondrion; and (iii) a particularly elongate cell shape because of the unusual length (about 1 μm) of the kinetosome and the presence of a 1-μm-long flagellar cavity which surrounds the base of the flagellum. Cytoskeletal elements include cytoplasmic microtubules, microfilaments which mainly reinforce the flagellar cavity, and props which anchor the kinetosome in the plasmalemma at the roof of the flagellar cavity. The role of these elements is discussed. A revision of the description of the olpidiaceous zoospore is suggested.
Fluctuations of phytoplankton biomass and its composition in a subarctic lake during summer
Authors: Sheath Robert G. , Munawar Mohiuddin , Hellebust Johan A.
Published: September 2008

Phytoplankton biomass was determined for a shallow subarctic lake from June to August, 1973, with one peak being observed at the beginning of July (300 mg m−3). Phytoplankton then declined until the end of August when a relatively high value of 240 mg m−3 was observed. The Chlorophyta and Diatomeae were the dominant taxa during periods of high biomass, whereas other algal groups had relative increases only during the minima. The early summer population was almost entirely composed of diatoms, followed by a mixed population of diatoms and cryptomonads, and then by the Chlorophyta, which dominated during midsummer. Subsequently, there were successive increases of chrysomonads, dinoflagellates, and then diatoms. Fluctuations of major species were examined in relation to changes in biomass of the algal groups. Net plankton species were dominant throughout most of the summer but nanoplankters were abundant for short periods in mid-June and July. Based on a few comparisons done in July, it was found that the species composition of phytoplankton was not similar to that of the benthic algae since only 15% of the species were common to both habitats and these species contributed to 21% of the phytoplankton biomass estimated.