bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultrastructural studies on the oil bodies of Marchantia paleacea Bert. II. Advanced stages of oil-body cell differentiation: synthesis of lipophilic material
Authors: Galatis B. , Katsaros Chr. , Apostolakos P.
Published: May 2008

At the onset of the active synthesis of oil-body (OB) lipophilic material, the oil-body cells (OBC's) appear to have gained a high degree of specialization towards a specific type of secretory cell. They possess a dense ribosomal cytoplasm, an active Golgi apparatus, abundant rough endoplasmic reticulum (ER) membranes, ER-ensheathed chloroplasts, a peculiar compartment encompassed by a membrane resembling the plasmalemma, small vacuoles, and OB-associated microtubules as well as some subplasmalemmal ones. At these stages intimate associations between ER membranes and OB's are established, while another class of cytoplasmic tubules, some of which are associated with microbodies, is formed in the cytoplasm.Initially, some material (matrix) starts being accumulated in the OB compartment as well as on the inner face of its limiting membrane, where it forms a distinct layer. This accumulation is followed by the appearance of minute opaque lipophilic globules. The number and the size of the globules increase considerably, their structure is gradually differentiated, and matrix fills the globule-free space in scale and epidermal OB's. Each of them is not surrounded by a true membrane but is delimited by a thin layer of dense material. Some of the epidermal and a few scale OB's of the young thalli follow a diverse differentiation process and form one or a few large globules surrounded by a very thin layer of matrix. Ultimately, these OB's are destroyed and force the OBC's to break down. The mature inner OB's generally contain small globules, the membrane-associated material, and traces of matrix. A structural diversity exists between the OB's of young and mature thalli. In the latter all the OB's exhibit small globules only.The globules are exclusively elaborated in the OB which is an active cell element; cytoplasmic or plastidic lipophilic material has never been observed entering the OB. After the completion of their development, the OB's occupy most of the cell space; the protoplasm diminishes while the dictyosome and ER activity gradually ceases.The OB's are well preserved with osmium tetroxide fixation or with the double one with glutaraldehyde, performed at 0 °C, 4 °C, or at room temperature for 20 min, followed by osmium tetroxide. On the contrary, a prolonged glutaraldehyde prefixation at room temperature causes a destruction of the OB containing large globules, a partial degradation of the ones containing smaller globules, and removes the matrix almost totally.
Coelomomyces canadense stat. et comb. nov. (Blastocladiales: Coelomomycetaceae) from Psectrocladius sp. G (Diptera: Chironomidae)
Authors: Nolan Richard A.
Published: May 2008

Resistant sporangia of Coelomomyces chironomi var. canadense Weiser and McCauley were examined by bright-field, phase-contrast, and scanning electron microscopy (SEM). The use of SEM facilitated the observation of previously undescribed complex furrows in the sporangial wall. The taxonomic criterion for varietal status is discussed, and the variety is elevated to species status. Coelomomyces canadense (Weiser and McCauley) Nolan stat. et comb. nov. is described with an emended Latin diagnosis.
Characterization of Agrobacterium isolates from stone fruits in Ontario
Authors: Dhanvantari B. N.
Published: May 2008

Isolations made from 68 naturally infected peach, plum, and sweet cherry nursery stock from the Niagara Peninsula and southwestern Ontario yielded 30 pathogenic isolates of Agrobacterium. These isolates were separated into two groups by 17 physiological and biochemical tests. The predominant group, consisting of 27 isolates, was 3-ketolactose negative and corresponded to biotype 2, and the other, consisting of only three isolates, corresponded to biotype 1 of Agrobacterium radiobacter var. tumefaciens sensu Keane, Kerr, and New (1970). Among the pathogenic isolates, 25 were sensitive and 5 were resistant to the bacteriocin produced by strain 84 of A. radiobacter var. radiobacter sensu Keane. Kerr, and New (1970).
Response of carbonicolous ascomycetes to aerated steam temperatures and treatment intervals
Authors: Zak J. C. , Wicklow D. T.
Published: May 2008

This laboratory study was designed to examine the response of a postfire ascomycete community to elevated temperatures and treatment intervals corresponding to those recorded during the burning of a tallgrass prairie. Aerated steam treatment of prairie soil samples (35, 40, 55, 70, 85, or 100 °C) for intervals of 60, 100, 140, or 180 s enabled us to examine the response of individual species comprising the carbonicolous ascomycete community.Simulation of a grassland fire by aerated steam treatment of prairie soils promoted the development of 20 species of ascomycetes. Generalists such as Sporomiella subtilis Ahmed and Cain occurred at high frequencies over most of the temperature range while specialists Podospora curvispora (Cain) Cain, Sordaria macrospora Awd., and Leptosphaeria sp. were important at only one temperature. Species diversity, richness, and number of species per sample were significantly affected by the temperature of the steam treatment. The temperature–treatment interval combination allowing for the greatest expression of diversity in the carbonicolous ascomycete community was 55 °C for 60 s. Since a grassland fire does not uniformly heat the soil surface, the environmental patchiness created by this physical perturbation may be an important factor in determining the composition of the carbonicolous ascomycete community in prairies.
Germination of Entomophthora aphidis resting spores under constant temperatures
Authors: Payandeh Bijan , MacLeod D. M. , Wallace D. R.
Published: May 2008

Germination tests at a wide range of constant temperatures show that the upper and lower thresholds for E. aphidis resting spores are about 3.5 and29.5 °C, respectively. Good germination was obtained over the range 10–22 °C with an optimum at about 16.5 °C. It is not known if spores exposed to temperatures above the optimum and failing to germinate are inactivated or killed. An empirical model is presented that describes the time–temperature–germination relationships of one test population. A similar modeling approach may be also applied to other spore populations.
Effect of fertilization on production of epigeous basidiocarps by mycorrhizal fungi in loblolly pine plantations
Authors: Menge J. A. , Grand L. F.
Published: May 2008

Basidiocarps of 39 epigeous species of proven or potential mycorrhizal fungi were found in three fertilized Pinus taeda plantation s during 1972 and 1973. The largest numbers of basidiocarps on all three plantations were found on nonfertilized plots or plots fertilized with P only. Fewest basidiocarps were found on plots fertilized with N. Numbers of basidiocarps of Suillus hirtellus were decreased by N fertilization. Numbers of basidiocarps of some other potential mycorrhizal fungi were not altered substantially by fertilization treatments. The average numbers of total living mycorrhizal tips were correlated well with average numbers of epigeous basidiocarps of proven or potential mycorrhizal fungi on fertilized plots. However, if mycorrhizal tips formed by Cenococcum geophilum, which do not form visible basidiocarps, were ignored, the remaining mycorrhizal tips were not well correlated with numbers of basidiocarps of proven or potential mycorrhizal fungi.
Botryosporium madrasense
Authors: Hughes S. J. , Conway K. E.
Published: May 2008

Botryosporium madrasense, recorded originally from Madras, India, is illustrated and described from collections made in Florida, U.S.A. and Britain.
Relation of weather variables and host factors to incidence of airborne spores of Botrytis squamosa
Authors: Sutton J. C. , Swanton C. J. , Gillespie T. J.
Published: May 2008

Weather variables, leaf blight, and airborne spores of Botrytis squamosa were monitored in onion field plots at the Holland–Bradford Marsh, Ontario, in 1976. Incidence of spores showed marked daily periodicities with peaks normally between 0900 and 1200 hours Eastern Standard Time (EST). Daily spore counts were low (< 85 spores) during 7 to 28 July, often high (> 1000 spores) during29 July to 16 August, and moderate (100 to 1000 spores) between 17 and 28 August. Spore production was observed only on necrotic portions of onion leaves. Circumstantial and correlative evidence indicated that spore production was promoted by persistent leaf wetness (> 13 h), high temperatures during wetness periods (14 to 20 °C), and by leaf dieback but was restricted by brief wetness periods [Formula: see text] and by cool temperatures [Formula: see text]. Linear correlation analyses of 2- to 4-day running means of data indicated that important limiting factors in spore production were wetness duration during 7 to 28 July, temperature during 29 July to 28 August, and severity of dieback during 7 July to 16 August. Lodging appeared to suppress incidence of spores after 16 August. Spore release was promoted largely by declining relative humidity (RH) and by rain but occasionally by increasing RH. Striking peaks of airborne spores occurred during rain showers. Spore counts when leaves were dry failed to correlate with wind speed, and many spores were dispersed when wind speeds were low(1 to 4 km/h).
Cyanogenic potential of Trifolium repens L. in relation to pepper spot caused by Stemphylium sarciniforme
Authors: Wilkinson H. T. , Millar R. L.
Published: May 2008

White clover (Trifolium repens L.) contains two cyanogenic β-glucosides (G), linamarin and lotaustralin. Upon injury to the tissues a β-glucosidase (E) effects the release of cyanide from the β-glucosides. Four selections of white clover differing in cyanogenic properties (G+E+, G+E−, G−E+, G−E−) were examined for differences in susceptibility to Stemphylium sarciniforme. Symptom development was determined at 24, 48, 72, 96, and 120 h after the leaves were inoculated. Symptoms for all four selections consisted initially of small brown flecks (1 mm in diameter), then dark spots (1–2 mm in diameter) with definite borders, and finally senescence and wilt of the interlesion tissue. Plants containing both β-glucosidase (EC 3.2.1.21)and cyanogenic glucosides (G+E+) and those with only glucosides (G+E−) developed symptoms 24 h earlier than did the G−E+ and G−E− selections. The earliest symptoms were observed at 48 h; by 96 h all four selections showed comparable degrees of senescence and wilt. Pathogen development in infected leaves prepared as whole mounts was examined microscopically. Through 72 h after inoculation, development of S. sarciniforme in the G+E+ and G+E− selections was slower than in the G−E+ selections. By 96 h, however, fungal development in all four selections was comparable; commencement of leaf senescence coincided with extensive fungal colonization of necrotic tissue. Accelerated rates of symptom expression and retarded pathogen development apparently were positively correlated with cyanogenic potential of each white clover selection. Necrosis of suscept tissue was not correlated with cyanogenic potential of each selection.
Morphological variation in white and black spruce: investigation of natural hybridization between Picea glauca and P. mariana
Authors: Parker William H. , McLachlan David G.
Published: May 2008

To investigate the possibility that white spruce (Picea glauca (Moench) Voss) and black spruce (P. mariana (Mill.) B.S.P.) produce natural hybrids, a morphological analysis of cone and twig characters was performed on 41 white and black spruce trees from three sites in northwestern Ontario and on the Rosendahl spruce from Cromwell, Minnesota. For each tree 13 quantitative and 10 qualitative characters were determined, and the diagnostic ability of all characters was tested by frequency histograms. Scatter diagrams and two hybrid indices were constructed; one index was based only on quantitative data left in continuous form, while the second index was based on all diagnostic characters. Scatter diagrams consistently separated the two taxa, and both hybrid indices clearly showed a bimodal distribution of trees coinciding with species boundaries and not correlating with site or environmental factors. Some spruce trees were intermediate in certain respects, but no tree exhibited a pattern of consistent intermediacy. These results strongly suggest that(1) no hybrids or introgressed spruces were sampled from northwestern Ontario and (2) the Rosendahl spruce is not an F1 hybrid between white and black spruce, contrary to several reports, but rather is a white spruce. Earlier conclusions that white and black spruce successfully hybridize in nature apparently have resulted from the use of nondiagnostic characters, underestimation of the variation present in both species, and a priori weighting inherent in the methods used to calculate conventional hybrid indices.
On the generality of methods to obtain single-cell plant suspension cultures
Authors: Kubek D. J. , Shuler M. L.
Published: May 2008

Several techniques employing mechanical, chemical, or enzymatic methods have been suggested for the production of essentially single-cell plant suspension cultures. If single-cell cultures can be obtained, the effects of the media composition on growth can be unambiguously determined. Additionally, such cultures would be amenable to optical and electronic methods for rapidly determining cell mass, number, and volume and could easily be used in experiments on continuous cultivation. Most methods to produce single-cell cultures have been applied to only one or two species. In this paper, these techniques are compared when extended to cultures of Paul's Scarlet Rose (Rosa sp.) cells and soybean cells (Glycine max L.). It is concluded that no technique will generally give sustained disaggregation without affecting the apparent biochemical state of the culture.
Resource allocation in young plants of two perennial species of Plantago
Authors: Hawthorn W. R. , Cavers P. B.
Published: May 2008

Growth patterns and biomass allocation to component plant parts in Plantago major and P. rugelii were compared under greenhouse conditions. Within 3 months of germination individuals of P. major were larger and had devoted more dry weight to seed and production of ramets than those of P. rugelii regardless of the number and kind of neighbours. No significant differences in percent resource allocation to roots, caudex, leaves, and spikes were observed between plants of P. major subjected to increased interference, although the actual biomass and number of leaves and spikes were reduced. Mean reproductive (spike) allocation in P. major was about 21%. Although the root biomass within a treatment was similar for the two species, the percent allocation to roots in P. rugelii was two and one-half times greater. Growth of P. major was depressed more by intraspecific neighbours and of P. rugelii by interspecific neighbours. These perennial herbs exhibit disparate allocation patterns as young plants that suggest adaptations to different temporary environments. Plantago major, with its early and sustained diversion of biomass to seed production, is distinctly adapted to exploitation of frequently disturbed sites, while P. rugelii, because of its more extensive root allocation and delayed seed production, seems better adapted to less frequent disturbance.
Sporogenesis of some fungal plant pathogens under intermittent light conditions
Authors: Cohen Yigal , Levi Yehouda , Eyal Helena
Published: May 2008

Alternating light and dark periods applied during the moist terminal phase of sporogenesis reduced conidial yield of Peronospora tabacina on tobacco, Pseudoperonospora cubensis on cucumbers, and Helminthosporium turcicum on maize but did not affect the yields of Erysiphe cichoracearum on tobacco. This photoinhibition of conidiation increased with increasing light intensity and duration and frequency of the interrupting light periods. It was also increased with increasing leaf temperature. Lengthening the dark intervals between lightening periods to 2, 3, and 4 h removed the photoinhibition in P. cubensis, P. tabacina, and H. turcicum, respectively. A suggestion is made to use illumination as a controlling device of fungal plant diseases in greenhouses.
Fine structural observations on substances attributable to Ceratocystis ulmi in American elm and aspects of host cell disturbances
Authors: Ouellette G. B.
Published: May 2008

Plugging of certain vessels may occur in elm shortly after inoculation with the Dutch elm disease pathogen, Ceratocystis ulmi (Buism.) C. Moreau. Plugging components include fibrillar material of varying density and fungal cells traceable mostly to inoculated spores. Some material is similar to fungal cell contents, and indications of extrusion of the latter through ruptured or unruptured walls were obtained. Other material is also attributable to disintegrating fungal walls. Radioautographs obtained from samples treated with [6-3H]thymidine indicate significant labeling of fungal cell contents and of similar material, free.Similar fibrillar material, some labeled, is present within pit membranes, in adjacent parenchyma cell walls, and in periplasmic areas associated with retraction of the plasmalemma and with other cytoplasmic disturbances. Host vessel walls are also altered in the presence of some fibrillar material but apparently release only limited amounts of disintegration products into vessels.The possible implications of these observations are discussed in relation to current hypotheses on wilt diseases.
Ultrastructural observations on pit membrane alterations and associated effects in elm xylem tissues infected by Ceratocystis ulmi
Authors: Ouellette G. B.
Published: May 2008

Gradations in the degree of pit membrane alteration in tissues infected by Ceratocystis ulmi (Buism.) C. Moreau and collected at various intervals after inoculation are described. Membranes of bordered pit pairs are coated and apparently impregnated with bands or masses of osmiophilic material; this coating may be thick and stratified and the pit cavities completely occluded. Similar osmiophilic material also occurs in decreasing amounts over and within membranes of simple or half-bordered pits and within the adjacent protective layer. Various degrees of distention and cavity formation in these pit membranes are associated with the osmiophilic material. Products released into vessels from disintegrating pit membranes seem to be sparse. Host cytoplasm in contiguous parenchyma cells can have diverse reactions.Examination of specimens at various angles established the interrelationship between osmiophilic material and remnants of pit membranes. Variously oriented lamellar-like structures and a fibrillar material intermixed with a more amorphous one characterize the osmiophilic material. The significance of these observations is discussed.
A carbon-13 biosynthetic study of stress metabolites from carrot roots: eugenin and 6-methoxymellein
Authors: Stoessl Albert , Stothers J. B.
Published: May 2008

Sodium [1,2-13C2]acetate was readily incorporated into the stress compounds 6-methoxymellein (I) and eugenin (III) after their formation in carrot roots had been induced by treatment with ethrel. The complete incorporation patterns were revealed by 13C nuclear magnetic resonance spectroscopy and confirm a polyketide origin for both metabolites. In the formation of the heterocycle of eugenin, two different C atoms are utilized to the same extent. This implies that an intermediate on the biosynthetic pathway is not firmly enzyme bound.
Axenic culture of Cronartium fusiforme from three spore forms
Authors: Hare Robert C.
Published: May 2008

Axenic cultures of the fusiform rust fungus (Cronartium fusiforme) were initiated from basidiospores, aeciospores, and uredospores. The morphology, cytology, and nuclear condition of the mycelium from the three spore stages are described and illustrated. Cultures derived from aeciospores and uredospores of C. fusiforme are reported for the first time. An improved culture medium is described. Inoculation of slash pine (Pinus elliottii var. elliottii) seedlings with suspensions of mycelium from basidiospores induced some typical galls which produced pycnial exudates and aeciospores. On synthetic medium, cultures from basidiospores were monokaryotic. Mostly dikaryotic mycelium was produced from aeciospores and uredospores, but some monokaryotic hyphae were observed.
Contribution à l'étude des carences en cuivre chez les Abiétacées
Authors: Strullu D. G. , Bonneau M.
Published: May 2008

The authors have described the morphological deformations owing to copper deficiency in Pseudotsuga menziesii and Picea sitchensis. The experimental studies entered upon have enabled us to determine the copper deficiency level for both species. With Douglas fir, the deficiencies occur under 4 ppm in the leaves; with spruce, the level is set at 2.5 ppm. Treatment of the plantations with 20 g of copper sulphate per tree increases the copper content in the leaves. This treatment also brings about the straightening of the distorted axes; the recorded effects depend upon the state of the saplings before treatment.
8-Azaguanine-resistant variants of cultured cells of Haplopappus gracilis
Authors: Horsch Robert B. , Jones Gary E.
Published: May 2008

Cultured cell lines of Haplopappus gracilis resistant to the purine analog 8-azaguanine (AG) have been isolated. One such line is 50 times more resistant to the drug than are wild-type cells. This line of AG-resistant cells also exhibits increased resistance to 8-azaadenine, but it responds to kinetin in a manner identical with that of wild-type cells. The resistance phenotype is stable for many generations in the absence of selection. In cultures of wild-type or mutant cells, more than 95% of cells are diploid.
Light and electron microscope studies on cell wall breakdown in American elm xylem tissues infected with Dutch elm disease
Authors: Ouellette G. B.
Published: May 2008

Seven years (1970–1977) of comparative light and electron microscope studies show that extensive cell wall disruption and breakdown occur consistently in elm xylem tissues infected by Ceratocystis ulmi (Buism.) C. Moreau. These alterations, noticeable even in incipient infection, can be related to the severity of wilting development and occur in association with the presence of an unbound osmiophilic material containing fine fibrillar material, dense particles of approximately 15 nm, and multilamellate structures. Masses of unbound osmiophilic material in host walls and walled fungal cells with which it is sometimes continuous are highly and exclusively labeled following injection of [6-3H]thymidine.The presence of osmiophilic material in host walls and the interrelation between the two was further established by examining stereoscopic pairs of prints taken at various angles with a goniometer. This type of cell wall breakdown seems difficult to relate to other known types of wood rots. Further discussion on the possible nature and origin of the osmiophilic material is presented.
Helicoidal branching in Dianthus caryophyllus
Authors: Emino Everett R.
Published: May 2008

The carnation, Dianthus caryophyllus L., a species with decussate phyllotaxis, has a helicoidal one-quarter cladotaxis branching pattern. This pattern may be either a right-or left-handed spiral. Morphological studies of the axillary bud primordia area show a well developed lateral branch primordium along one helix and none along the other helix. Rooted cuttings from right-handed spiral branching plants produced plants in approximately equal numbers with right- and left-handed spirals. Similar results were observed for left-handed spiral plants. This equal distribution from a clone indicates that the branching pattern of the lateral shoot is independent of the branching pattern of the shoot of origin.
The growth of Easter lily (Lilium longiflorum) as influenced by vesicular–arbuscular mycorrhizal fungi, Fusarium oxysporum, and fertility level
Authors: Ames R. N. , Linderman R. G.
Published: May 2008

Easter lily bulbs were inoculated in the greenhouse with pot-culture inoculum containing a mixture of four vesicular–arbuscular (VA) mycorrhizal fungi as well as other fungi and bacteria, including pathogens. These organisms had multiplied in association with roots of lily, onion, and clover in pot cultures inoculated with sievings from lily field soils. Growth, as measured by bulb weight gain, root volume, and total leaf area, was determined on lily bulb plants inoculated at two inoculum levels and grown under three fertilizer regimes. Growth of plants inoculated with pot-culture inoculum was less than that of controls, especially in plants given the high inoculum (which included pot-culture plant roots) and the high rate of fertilization. The growth reduction apparently was due to the combined effect of greater incidence of Fusarium oxysporum root rot infections, damage to roots from fertilizer, and lower incidence of VA mycorrhizal infections. More mycorrhizal infections occurred in the low-fertilizer treatment than in the high- or no-fertilizer treatments at both high and low inoculum levels, but more F. oxysporum root rot occurred in the high-inoculum, high-fertilizer treatment.In a second experiment, lily seedlings that lacked bulb nutrient reserves were grown at a low fertilizer level and inoculated with Acaulospora trappei without any pathogens. Mycorrhizal plants were significantly larger than nonmycorrhizal control plants, and their tissues contained more N, P, K, Ca, and Mg than control plant tissues.
A new species of Verrucispora (Hyphomycetes) from India
Authors: Singh Kamal , Singh R. P.
Published: May 2008

Verrucispora indica, a new species of Hyphomycetes parasitizing the living leaves of Smilax prolifera Roxb., is described and illustrated.
Guard cell ontogeny in leaf stomata of the fern Ophioglossum petiolatum
Authors: Peterson R. L. , Hambleton Sarah
Published: May 2008

Guard cells in Ophioglossum petiolatum leaves are initiated by a single division of a stomatal initial with no subsidiary cells being formed. The stomatal initials have few vacuoles, plastids with little starch, and a large nucleus with much heterochromatin and prominent nucleoli. Young guard cells are similar cytologically to stomatal initials; their common cell walls are thin and traversed by plasmodesmata. Plasmodesmata are also present within guard cell and adjacent epidermal cell walls. With increasing age, guard cells develop a lenticular thickening in the median portion of the common cell walls, larger vacuoles, and plastids with several starch grains. Numerous microtubules are present near the thickening wall which also has an electron-translucent region between the cell wall and the plasmalemma. Many dictyosomes and mitochondria are present in the cytoplasm. Older guard cells become more vacuolated, with some of the vacuoles containing fibrillar or dense deposits. Plastids become very large as a result of storing several large starch grains. In the thickened portion of the cell walls, the middle lamella and some of the adjacent cell wall appear to be degraded during stomatal pore formation. Mature guard cells are highly vacuolated and have very thick electron-dense cell walls without plasmodesmata. Fluorescence microscopy following aniline blue staining shows that aniline blue positive materials are present around and within the thickened portion of the cell walls, at the junction of guard cells with epidermal cells, and as distinct spots in guard cell and epidermal cell walls during the early stages of ontogeny. Mature guard cells, however, lack the distinct fluorescent spots, which are interpreted as plasmodesmata, in their walls.
The effect of cycloheximide and cycloheximide analogues on protein, asparagine, and glutamine synthesis in corn root tips
Authors: Wheatley W. George , Oaks Ann
Published: May 2008

Cycloheximide treatment (3.6 × 10−6 M) inhibits the incorporation of [2-14C]acetate into protein, asparagine, and the organic acids and sugars fraction. At the same time, it enhances the release of 14CO2 and the incorporation of carbon into glutamine and the neutral and basic amino acid fraction. Eight structural analogues of cycloheximide were tested for their effects on protein, asparagine, and glutamine formation in corn root tips. Two analogues, cycloheximide acetate and streptovitacin A (at a concentration of 1.8 × 10−5 M), acted in a manner similar to cycloheximide. Their effect was to inhibit protein and asparagine synthesis and to enhance glutamine formation. Six other analogues (1.8 × 10−5 M) had no marked effect on these fractions. The results of this investigation indicate that the structural analogues which inhibit asparagine formation in corn root tips also inhibit protein synthesis. The results suggest that the hydroxyl group of the hydroxyethylglutarimide portion of the cycloheximide molecule and the ketone-carbonyl group of the cyclohexanone ring are important for their action on protein synthesis in corn root tips.
The preservation of membranes of tubular bodies associated with mycoplasmalike organisms by tannic acid
Authors: Chen M. H. , Hiruki C.
Published: May 2008

Fixation with a mixture of tannic acid and paraformaldehyde–glutaraldehyde resulted in an increased electron density of the membrane structure of tubular bodies that were associated with mycoplasma organisms (MLO) in Vinca rosea plants infected with the Alberta isolate of the aster yellows agent. The tubular bodies, 25.5 ± 4.3 nm in diameter, were bounded with membranes in contrast with the hollow cylinders of 12.3 ± 3.0 nm in conventional fixation. In the study of physical relationships, the tubular bodies were often connected with MLO by a common unit membrane. Some subtubules were formed from a main tubular body.
Anthocyanin pigmentation in roots of Impatiens species
Authors: Thakur Mira , Nozzolillo Constance
Published: May 2008

A red anthocyanin pigmentation has been investigated in root tips and mature roots of seedlings and potted plants of Impatiens (Balsaminaceae): I. balfourii, I. balsamina, I. capensis, I. flaccida, I. linearifolia, I. platypetala, I. repens, I. schlechteri, I. sultani, I. uguenensis, and several hybrid cultivars. Reddening of root tips when present in young seedlings occurs also in mature plants and seems to be a continuing feature of root development. The appearance of red pigmentation in mature root tissues was sporadic and independent of the reddening of root tips. Leucoanthocyanidins (proanthocyanidins) were invariably detected whether anthocyanins were present or not. The root anthocyanins of I, balsamina and I. platypetala include a cyanidin-3-glycoside plus an additional, as yet unidentified, minor constituent.
Spartina alterniflora seed fungi
Authors: Gessner Robert V.
Published: May 2008

The filamentous fungi occurring on Spartina alterniflora seeds attached to inflorescences, on marsh sediments, and submerged in estuarine waters were studied. Seed-borne fungi commonly found on grain crops and graminicolous Ascomycetes were found on the seeds attached to the panicles. After 2 months on the marsh surface or in the adjacent sound and tidal creek, additional species, including marine fungi, were observed on the seeds. After 5–7 months marine fungi and graminicolous Ascomycetes were the only fungi found by direct observation, although seed-borne species could still be isolated by incubation methods. The seeds were completely degraded or barely recognizable after 11 months on the marsh sediments or in seawater. Claviceps purpurea parasitized the seed heads at all the marsh areas sampled. The greatest number of sclerotia were found on the tall S. alterniflora near the lower edge of the marsh in exposed areas and on inflorescences from dredge spoil areas. Up to 183 sclerotia/m2 and sclerotia dry weight values of up to 2.72 g/m2 were found. Eight Ascomycetes, one Basidiomycete, and 16 Fungi Imperfecti were identified. Ceriosporopsis halima, Corollospora maritima, Cirrenalia macrocephala, Halosphaeria hamata, and Trichocladium achrasporum, primarily known as 'wood-inhabiting' marine fungi, occur on submerged Spartina alterniflora seeds, suggesting that these fungi are general decomposers of plant debris in marine habitats.
Seed yield and quality in Populus tremuloides following pollination with gamma-irradiated pollen
Authors: Rudolph T. D.
Published: May 2008

A pollen mixture from three male quaking aspen (Populus tremuloides Michx.) trees was irradiated at exposures of 484, 968, 1453, 1937, 3874, 7747, and 15 494 R and used to control-pollinate cut branches from three female trees. The pollen radiosensitivity was determined from various seed yield and seed quality factors. The pollen LD50 exposure varied with the end point evaluated, ranging from 255 R for number of 50-mesh seed per catkin to 8800 R for total seeds per catkin. The mean LD50 for nine seed yield and seed quality end points was 3995 R. A significant stimulatory response in seed yield was noted at low pollen irradiation levels, particularly at the 484-R exposure. The LD100 was approached but not reached at 15 494 R. Irradiated quaking aspen pollen may be useful in breeding experiments.
Le phloème de Lycopodium clavatum : organisation, ultrastructure et histochimie
Authors: Hébant Charles , Guiraud René , Barthonnet Joëlle , Ba Amadou Tidiane
Published: May 2008

Metaphloem sieve elements of Lycopodium clavatum L. are elongated cells with steeply inclined end walls. Numerous pores of small diameter are present on all contact walls between sieve elements. At maturity, these elements lack a normal-looking nucleus, and their protoplast is partially degenerated. Parenchyma cells with a well-structured protoplast are associated with them, the symplastic continuity between the two types of elements being assured by plasmodesmata. Intense phosphatase and respiratory enzyme activities are identifiable in the parenchyma cells. A functional association appears to exist between sieve elements and parenchyma cells.The absence of refractive spherules from the phloem of all the Lycophyta studied up to now is underlined: this fact is in agreement with the hypothesis that the Lycophyta constitute a relatively isolated group amongst primitive Tracheophytes.
Delayed expression of aster yellows symptoms in celery
Authors: Chiykowski L. N.
Published: May 2008

Two strains of aster yellows agent, one resembling a typical 'noncelery-infecting' or eastern type (EAYA) and the other a 'celery-infecting' or western type (CAYA), were compared for their ability to infect celery. Seventy-four percent of the plants inoculated with EAYA and 100% inoculated with CAYA developed symptoms. An average of 115.7 days was required for symptoms of EAY to appear while only 40.6 days were required for CAY. In aster, this difference was much less pronounced. EAYA was less efficiently acquired from celery than was CAYA. The status of this EAYA in the aster yellows complex found in nature is discussed.
Fine structure of tissue bordering lesions induced by wounding and virus infection
Authors: Faulkner G. , Kimmins Warwick C.
Published: May 2008

Tissue in Phaseolus vulgaris L. cv. Pinto bean bordering local lesions induced by tobacco mosaic virus showed cell wall deposition associated with paramural body formation in a narrow ring of viable cells extending one to three cell diameters around the lesions. Deposition, which led to secondary cell wall thickening, was greatest 3–4 days after inoculation, the time when the lesion stopped expanding. Secondary cell wall thickening, of similar appearance but less pronounced, was seen in tissue bordering local lesions which continued to expand; no significant secondary cell wall thickening was observed in leaves with a nonlocalized infection. Cells bordering mechanical lesions differed markedly in fine structure from cells bordering virus and chemical lesions. It is suggested that the deposition of extra cell wall material in the wall regions of cells bordering fully expanded local lesions is associated with virus localization.
Cross-incompatibility of common wheat with rye: effect of varying the day of pollination on seed set and development
Authors: Thomas Julian B. , Anderson R. Glenn
Published: May 2008

Varieties of common wheat (Triticum aestivum L. em. Thell.) of low wheat–rye crossability showed increased seed set if pollinated with cultivated rye (Secale cereale L.) before the wheat spike attained maximum receptivity to wheat pollen (before the stage of first anthesis). After first anthesis the development of hybrid seed progressively deteriorated with increasing lateness of pollination. Premature or 'bud' pollination may be a useful approach for overcoming intergeneric cross-incompatibility barriers in the Triticineae.
The morphology of grain abscission in Zizania aquatica
Authors: Hanten H. B. , Ahlgren G. E. , Carlson J. B.
Published: May 2008

The anatomical development of the abscission zone in grains of Zizania aquatica L. was correlated with development of the embryo. The abscission zone is well developed when the embryo sac is mature. Soon after pollination, the first anatomical evidence of abscission appears as plasmolysis of the separation layer parenchyma cells. This is followed by separation of the layers by dissolution of the middle lamella and fragmentation of cell walls. Persistence of intact vascular tissue and presence of a surrounding cone-shaped mass of lignified cells may be involved in abscission of wild rice grains.
Isolation of a cationic peroxidase from cultured peanut cells
Authors: Maldonado B. A. , Huystee R. B. van
Published: May 2008

Medium that had supported the growth of a peanut cell suspension culture was found to be a rich source of peroxidase. Precipitation with acetone and ammonium sulfate, followed by a pH shift and ion exchange chromatography, led to the isolation of a single cationic peroxidase isozyme of high specific activity and high RZ of 2.91. The isolated peroxidase was shown to be a single peptide chain.
Sporogenesis in male plants of Chondrus crispus (Rhodophyta, Gigartinales)
Authors: Meer J. P. van der , Guiry M. D. , Bird C. J.
Published: May 2008

Chondrus crispus has a sexual life history of the Polysiphonia type and spores other than carpospores and tetraspores have not previously been reported. Several cultures of male plants from widely separated geographic locations have now been observed to produce large masses of spores in structures that superficially resemble cystocarps but whose origins do not appear to be sexual. Spores released from these masses were viable and gave rise to plants closely resembling normal tetrasporophytes, complete with tetrasporangial sori; however, the sori released no spores and it appears likely these unusual plants were haploid with an abortive haploid meiosis in the tetrasporangia. Like normal diploid tetrasporophytes, the plants with dysfunctional tetrasporangia reacted negatively in a standard resorcinol test for 3,6-anhydrogalactose and thus appeared to contain λ-carrageenan. These results suggest that carrageenan type is associated with reproductive phase and not the chromosome ploidy. The sporogenous male phenotype was transmitted in crosses, but the data are presently too limited to determine the exact mode of transmission. Nevertheless, it appears that at least two gene loci are involved, one of them being the sex-determining locus.
Effect of high temperatures on imbibition, germination, and thermal death of velvetleaf (Abutilon theophrasti) seeds
Authors: Horowitz M. , Taylorson R. B.
Published: May 2008

Seeds of velvetleaf (Abutilon theophrasti Medic.) were treated for various durations at temperatures from 40 to 60 °C. Rate of water uptake increased with temperature of imbibition. Germination of imbibed (soft) seeds was not affected by 40 °C imbibition for 30 h. At temperatures ≥ 43 °C, an inverse relationship was seen between temperature and time of imbibition required to reduce germination by a given level. Seeds exposed to temperatures up to 55 °C in dry or humid air or imbibed in osmotica of polyethylene glycol 6000 showed inhibitory effects on germination increased as time of exposure and seed water content increased. Seeds with low water content required longer exposures or higher temperatures to reduce germination. Heat treatments of <2 h caused greater germination reduction when applied after 24 h of imbibition than at the beginning. A heat stress of 1 h at 52 °C at the beginning and repeated after 24 h imbibition produced greater germination inhibition of soft seeds than a single 2 h 52 °C treatment at the beginning.
Stuartella suttonii n.sp., the teleomorph of Bactrodesmium obliquum var. suttonii
Authors: Funk A. , Shoemaker R. A.
Published: May 2008

Stuartella suttonii n.sp. is shown to be the teleomorph of Bactrodesmium obliquum Sutton var. suttonii Hughes & White. Cultures made from ascospores and conidia were identical; conidia sometimes formed on the ascomata and the two states occurred together consistently in the bark of Pseudotsuga menziesii (Mirb.) Franco.
Effects of nitrogen addition on the growth of Vaccinium uliginosum and Vaccinium vitis-idaea
Authors: Chester Ann L. , McGraw James B.
Published: May 2008

Nitrogen fertilization may affect plant growth by changing (i) shoot size and hence shoot weight,.(ii) shoot mortality, and (iii) shoot branching dynamics. This study assessed the effects of nitrogen addition on all three aspects of aboveground growth in cooccurring evergreen (Vaccinium vitis-idaea) and deciduous (Vaccinium uliginosum) species. Growth responses were used to estimate parameters for a model of overall shoot population growth. Shoot population size increased at similar rates in both species with nitrogen fertilization. However, the addition of nitrogen elicited a different type of response in each species. Vaccinium uliginosum showed an increase in the size of the shoots produced. This result, combined with the fact that larger shoots produced a greater number of daughter shoots, was responsible for the shoot population increase. In contrast, the addition of nitrogen increased the rate of lateral meristem release for shoots of all sizes in V. vitis-idaea. The ecological implications of the results are discussed with respect to evergreen and deciduous habits.
Comparative study on freezing resistance of conifers with special reference to cold adaptation and its evolutive aspects
Authors: Sakai A.
Published: May 2008

From extensive winter hardiness studies of conifers growing in different parts of the world, large differences in winter hardiness are evident among families and genera. Very hardy conifers have evolved from four northern genera of Pinaceae: Pinus, Picea, Larix, and Abies. Winter hardiness of conifers varies with the minimum winter temperature of their natural range. The freezing resistance of most conifers is characterized by the relative susceptibility of the shoot and flower primordia of buds to freezing. The shoot and flower primordia of conifers, except the genus Pinus, survive freezing by extraorgan freezing. The results are discussed with reference to evolution of cold hardiness of conifers.
Interaction between Glomus fasciculatum and Sclerotium rolfsii in peanut
Authors: Krishna K. R. , Bagyaraj D. J.
Published: May 2008

The interaction between the mycorrhizal fungus Glomus fasciculatum and the root pathogen Sclerotium rolfsii was studied in a pot culture experiment. The mycorrhizal fungus reduced the number of sclerotia produced by the pathogen and the pathogen reduced the percentage root infection and chlamydospore production by the mycorrhizal fungus. Root and shoot dry weights of the host and their P content was highest in plants inoculated with mycorrhiza only and lowest in plants inoculated with the pathogen only. Simultaneous addition of mycorrhizal inoculum and the pathogen reduced the severity of disease.
A critical assessment of criteria used in the taxonomy of the genus Rhizopus
Authors: Seviour R. J. , Pitt D. E. , McClure S. , Pyle J.
Published: May 2008

Scanning electron microscopy (SEM) and cultural physiology data have been used to assess their taxonomic applicability in delimiting species of the genus Rhizopus. SEM of the sporangiospores of a variety of isolates indicates that there is a continuum of patterns ranging from almost featureless surfaces to verruculose and deeply ridged or striated topologies. The degree of interspecific diversity was sufficient to reduce the diagnostic usefulness of this feature for interspecies delineation. Cultural characteristics, radial growth rate, sporulation pattern, and growth and viability at raised temperatures were also too variable for use in taxonomic studies.
Kinetics of first-cutting regrowth of alfalfa plants and nitrogenase activity in a controlled environment with and without added nitrate
Authors: Macdowall F. D. H.
Published: May 2008

Seedlings of Medicago sativa L. cv. Algonquin were grown in vermiculite and nodulated by Rhizobium meliloti strain 102F70 at two lower levels of N, until flowering when the tops were cut off to leave about 10% shoot stubble. Residual shoot dry matter immediately resumed first-order growth and maintained it throughout regrowth to second flowering. The rate constants of shoot regrowth were 34% lower (at 15 mM NO3−), 25% lower (at 1.5 mM NO3− symbiotically), or 220% higher (at zero NO3− symbiotically) than the values for 1 to 4-week-old seedlings, which indicated a radical change in physiology. Root dry matter resumed exponential growth after a 7-day recession and its recovery and yields were independent of N nutrition. The most pronounced minima occurred in the acetylene-reducing activity of nitrogenase, the kinetics of which paralleled root dry matter except that its redevelopment stopped after two-thirds of the regrowth time. The rate coefficient for the redevelopment of nitrogenase activity equalled that for its development during the seedling stage, which suggested unchanged limitations on that process until its redevelopment stopped.
Greffage in vitro du pin maritime (Pinus pinaster)
Authors: Tranvan H. , David A.
Published: May 2008

Besides adventitious budding in vitro, rejuvenation of meristems could possibly be achieved by micrografting. We report here successful auto- and homo-grafting in vitro in Pinus pinaster. Apices 5–7 mm in length either (i) collected from 2- to 3-month-old seedlings or (ii) produced in vitro from an 11 -year-old tree by means of successive axillary budding cycles over a 5-year period were successfully grafted onto the epicotyl of 2- to 3-month-old seedlings. Grafted plants have been successfully transfered to field conditions. If grafted onto the hypocotyl, plants did not survive.
Glyphosate as a probe of the pentafunctional arom protein of Euglena gracilis
Authors: Byng Graham S. , Whitaker Robert J. , Jensen Roy A.
Published: May 2008

Glyphosate (N-(phosphonomethyl)glycine) inhibited the growth of myxotrophically cultured Euglena gracilis. This inhibition was reversed by a combination of end products of the aromatic amino acid biosynthetic pathway, including the quantitatively minor vitamin precursors. This suggested a stringent inhibition of the early-pathway reactions, five consecutive reactions of which are catalyzed by the arom protein. Glyphosate was shown to affect the catalytic properties of the arom protein, thus providing a new means for studying the relationships of intrapathway catalytic sites to one another in this unique protein.