bluuebunny/crossref_metadata_2025 huggingface dataset:
Cell and nucleomorph division in the alga Cryptomonas
Authors: McKerracher Lisa , Gibbs Sarah P.
Published: April 2011

An ultrastructural investigation of cell and nuclear division in Cryptomonas sp. (θ) was made with particular emphasis on the mode of division of the chloroplast and nucleomorph. Mitosis is similar to that in other cryptomonads except that the nuclear envelope remains mostly intact. Division of the single chloroplast occurs in preprophase by constriction through the dorsal bridge. Frequently there is a lag between the division of the chloroplast and the division of its envelope of chloroplast endoplasmic reticulum. In addition, the inner membrane of the chloroplast endoplasmic reticulum may infold well in advance of the outer membrane.The nucleomorph is a unique double membrane limited organelle which is found in the periplastidal compartment of cryptomonads. It divides in preprophase following basal body replication but before division of the chloroplast and its chloroplast endoplasmic reticulum is complete. The inner membrane of the nucleomorph envelope invaginates first forming a double membraned baffle. The outer membrane invaginates next and completes division. Microtubules are not involved in nucleomorph division. None were observed and colchicine, which inhibited nuclear division, did not inhibit nucleomorph division. The theory that the nucleomorph is the residual nucleus of a former eukaryotic endosymbiont is reevaluated in light of these new observations.
Spore studies in the genus Gymnocarpium
Authors: Pryer Kathleen M. , Britton D. M.
Published: April 2011

Scanning electron microscopy was used to examine the variation in perispore characters within and between six currently recognized taxa of the genus Gymnocarpium Newm. in North America. Representative scanning electron micrographs are presented and depict the perispore features observed. Spores of those taxa studied here do not each possess a distinctive morphology providing practical species discrimination, rather they all exhibit similar patterns of variation. Spore size was also examined and shown to be correlated to ploidy level, permitting positive identification of the diploid taxon G. dryopteris ssp. disjunctum from the tetraploid G. dryopteris ssp. dryopteris.
La caractérisation d'herbiers aquatiques du lac des Deux-Montagnes (Québec) à partir de paramètres physiques de l'eau
Authors: Vincent Gilles A. , Bergeron Yves
Published: April 2011

Forty-four sites of aquatic plant communities of lac des Deux-Montagnes were studied during the summer of 1981 for floristic composition and six physical parameters (depth, pH, amount of phosphate, conductivity, alkalinity, and amount of dissolved oxygen). In a first step, the percent cover of every species in each community served to calculate the similarity between the 44 sites. The data were then analysed by principal coordinate analysis and hierarchic agglomeration cluster analysis. The study of the ordination and the dendrogram revealed 12 principal groups. Subsequently, a discriminant analysis, based upon six physical parameters, identified the parameters which most contribute to discrimination between the groups. Those parameters are pH, depth, alkalinity, and amount of dissolved oxygen. The classification resulting from the discriminant analysis agrees in a proportion of 72.97% with the original classification based on the floristic composition. A contingency table has been analysed to establish the role of each individual parameter on every one of the groups. Finally, the causality of this discrimination is discussed in relation to fine partitioning of shallow waters in the littoral zone.
Lignicolous marine fungi from São Paulo, Brazil
Authors: Booth Tom
Published: April 2011

Lignicolous substrates, i.e., wood and leaves, were collected from 10 São Paulo State locations and 2 Pernambuco State sites. These were subsequently surveyed and incubated and (or) washed, macerated, and plated on culture media. Six types of wood and mangrove leaves were placed in exposed and buried digestors, recovered, surveyed, incubated, and resurveyed for marine fungi. Of a total of 69 isolated taxa, 32 species, including 24 ascomycetes, seven fungi imperfecti, and one basidiomycete, are discussed. Included are Ceriosporopsis cambrensis; C. halima; Corollospora lacera; C. maritima; C. pulchella; C. trifurcata; Crinigera maritima; Didymosphaeria enalia; Haligena viscidula; Halosarpheia fibrosa; Halosphaeria appendiculuta; H. cucullata; H. galerita; H. hamata; H. maritima; H. mediosetigea; H. quadricornuta; H. salina; Leptosphaeria cfr. marina, Leptosphaeria sp.; Lignincola laevis; Lulworthia medusa (f. grandispora); Mycosphaerella sp.; Torpedospora radiata; Ceriosporopsis halima anamorphic form; Cirrenalia tropicalis; Clavariopsis bulbosa; Periconia prolifica; Scolecobasidium? arenarium; Septoria sp.; Trichocladium achrasporum; and Nia vibrissa. Morphological features, collection sites, substrates, slides, cultures, taxonomic deposition, and ecological considerations are presented for each species. A possible Scolecobasidium–Septoria–Mycosphaerella anamorphic–teleomorphic association is suggested.
Comparison of cyst and sporangium wall widths in species of Dictyuchus, Brevilegnia, and Achlya
Authors: Armbruster Barbara L. , Johnson Jr. T. W.
Published: April 2011

Qualitative and quantitative analyses of wall widths in Achlya debaryana, Dictyuchus anomalus, D. pseudodictyon, and Brevilegnia minutandra reveal statistically significant differences among the isolates. Achlya debaryana has the thickest sporangium walls, followed in order by D. anomalus, D. pseudodictyon, and B. minutandra. A correlation exists between wall widths and the type of spore release characteristic of the genus. The results are discussed in terms of variation in spore release patterns in saprolegniaceous fungi.
Relations entre spectres polliniques contemporains et topographie dans la vallée de la Coppermine, Territoires du Nord-Ouest
Authors: Geurts M.-A.
Published: April 2011

Thirty six moss polster samples from forest tundra and shrub tundra collected along the Coppermine River Valley, N.W.T., result in six pollen assemblages associated with type landforms. Forest sites on moderately steep slopes of approximately 12° yield spectra dominated by spruce. Spectra dominated by Salix (>50%) exist only at isolated sites where the shrub is the principal species found. Flat, well-drained surfaces on gentle slopes exposed to wind produce spectra dominated by more than 50% Betula. The assemblage Betula–Ericales corresponds to gentle slopes actively modified by cryogenic processes. The assemblages Betula–Salix and Salix–Betula are found on gentle, poorly drained slopes or in zones of shrub tundra where Salix is a pioneer species on surfaces newly exposed to weathering. The assemblage Betula–Picea is not a specific indicator since it is found on various topographic sites. The paper proposes one example of the utilization of these relationships between pollen spectra and landforms, for the interpretation of fossil pollen samples. This example shows that the variations in pollen spectra of a stratigraphic diagram do not exclusively reflect climatic variations or ecologic successions, but may be due to environmental change brought about by geomorphologic processes.
Light, oxygen, and temperature requirements for Typha latifolia seed germination
Authors: Bonnewell V. , Koukkari W. L. , Pratt D. C.
Published: April 2011

Typha latifolia L. seed germination required high temperatures, low O2 concentration, and relatively long exposure to light to induce high percentages of seed germination. A greater percentage of seeds germinated at 35 °C than at lower temperatures. Less than 10% of the seeds germinated at 15 °C and none at 10 °C. For submerged seeds exposed to red light (R), maximum germination was achieved when the O2 concentration in the water was reduced to between 2.3 and 4.3 mg L−1 at 30 °C. Seeds were most sensitive to R when imbibed for 6–24 h. At least 10 h of continuous R (2.5 × 10−8 W m−2) was needed for maximum germination. However, when seeds were exposed to light of the same intensity for four 30-min periods over a 12-h span, the effect was nearly the same as 12 h of continuous light. The germination percentage after the intermittent irradiation was nine times that produced by a single 2-h exposure. Five minutes of far-red light (FR) reversed the effect of 6 h of R to the level of dark controls. The photoreversible effect of FR was less pronounced for seeds imbibed prior to illumination. When spans of R and FR were alternated (FR–R–FR, R–FR–R, FR–R–FR–R, R–FR–R–FR), repeated reversibility was observed. However, FR was progressively less effective in reversing the effect of R.
Localisation cytochimique des activités phosphatasiques acides de champignons mycorhiziens développés sur milieu complet ou carencé en phosphate
Authors: Lacaze Bernadette
Published: April 2011

The mycelia of three mycorrhizal basidiomycètes (Pisolithus tinctorius (Pers.) Coker et Couch., Suillus granulatus (L. ex Fr.) O. Kuntze and S. bellinii (Izenga) Watling) were grown on media with or without inorganic phosphate. A cytochemical study of the distribution of acid phosphatase activity was made using light and electron microscopy. Highly enhanced enzyme activity was observed in the phosphorus-deficient mycelia. Precipitates were located primarily at the surface of the fungal cells. Cell walls appear devoid of reaction products in most cases.
Variation in achene weight in Aster acuminatus
Authors: Pitelka Louis F. , Thayer Mary E. , Hansen Sandra B.
Published: April 2011

In the forest understory herb Aster acuminatus, achene weight varies approximately 1.4-fold among achenes collected from single flower heads and 2.5-fold among achenes collected from numerous plants from three field sites. Inner and outer achenes in one flower head are normally similar in weight. Achenes collected from different flower heads on one plant usually vary significantly in weight. Significant variation in achene weight among plants from one patch was always observed. Variation among patches and field sites was small. Taller plants as a group had slightly heavier achenes than shorter plants. Lighter achenes were less likely to germinate and survive than heavier achenes and produced significantly smaller seedlings. The patterns of variation in achene weight indicate that most of it is nongenetic. The variation may be a consequence of short-term environmental variation during the time of achene maturation.
Histology, amino acid leakage, and chemical composition of normal and abnormal sclerotia of Sclerotinia sclerotiorum
Authors: Huang H. C.
Published: April 2011

This comparative study investigated the structure, amino acid leakage, and chemical composition of normal, slightly abnormal, and grossly abnormal sclerotia of Sclerotinia sclerotiorum collected from diseased sunflower heads. Histological studies showed that the normal sclerotia contained a relatively intact rind layer two or three cells wide, a cortex two to four cells wide, and a large white medullary region with numerous darkly stained, loosely arranged interwoven hyphae embedded in an amorphous matrix. In contrast, the abnormal sclerotia had a severely fractured rind and a brown medullary region with sparse, lightly stained filamentous hyphae embedded in the amorphous matrix which was often highly vacuolated. Cultural studies showed that the viable cells in abnormal sclerotia are mainly confined to the white medullary region and there is little evidence of hyphal growth from the brown-colored medullary tissue. Paper chromatographic analyses indicated that leakage of amino acids is greater in abnormal sclerotia than in normal ones. Chemical analyses revealed that protein, alcohol-soluble substances, and oil content are similar in normal and abnormal sclerotia, but the amount of ash is significantly higher in the abnormal ones. The effect of structural malformation on viability and survival of sclerotia is discussed.
La végétation forestière du Parc du Mont-Orford, Québec
Authors: Gauvin Claire , Bouchard André
Published: April 2011

In the context of a biophysical inventory of Mount Orford Park, the vegetation was sampled in 55 stations distributed throughout the territory, using the methodology of Bray and Curtis. Analysis with polar ordination points to altitudinal and humidity gradients as the main components responsible for the spatial distribution of the plant communities. Mesic forests of low altitude are dominated mostly by Acer saccharum, while the summits of the Orford massif support mixed stands of balsam fir, white birch, and red spruce. Some xeric forests of small areal extent, dominated by Pinus strobus or Quercus rubra, occupy the steep slopes of western or southwestern exposure. Tsuga canadensis or Abies balsamea dominate the communities of moist habitats. Finally, successional forests are found in some sectors of the park disturbed by fire or cutting. The description of each community is based on the structure, floristic composition, and dynamics of the vegetation as well as on environmental factors.
Ultrastructural aspects of cellular differentiation in the root cap of Zea mays
Authors: Moore Randy , McClelen C. Edward
Published: April 2011

The root cap of primary roots of Zea mays is composed of five distinctive types of cells: (i) the calyptrogen, or cap meristem, (ii) columella statocytes, located in the center of the root cap and characterized by the presence of sedimented amyloplasts, (iii) peripheral cells (PC) I, cells adjacent to the columella statocytes characterized by a more random distribution of amyloplasts and the absence of mucilage, (iv) PCII, cells containing mucilage between the cell wall and plasmalemma, and (v) PCIII, highly vacuolate cells typically detached from the root cap proper. As cells of the calyptrogen differentiate into columella statocytes, proplastids differentiate into amyloplasts which sediment to the bottom of the cell. Sedimented amyloplasts do not contact plasmodesmata in the bottom of columella statocytes. The starch content of amyloplasts decreases as columella statocytes differentiate into PCI. As PCI differentiate into PCII, mucilage is secreted into the space between the outer tangential cell wall and plasmalemma. As PCII differentiate into PCIII, numerous small vacuoles fuse into a large central vacuole. This vacuolation may be at least partially responsible for the movement of mucilage through the cell wall.
Vegetation studies at Polar Bear Pass, Bathurst Island, N.W.T. I. Classification of plant communities
Authors: Sheard J. W. , Geale Dorothy W.
Published: April 2011

Vegetation communities at Polar Bear Pass, Bathurst Island, are described with the aid of agglomerative classification using chord distance and the minimum variance criterion. Two classification levels were determined, one of 15 clusters and the other at the more generalized seven-community level. These community types are described in terms of statistically defined diagnostic species. The boundaries between the communities are identifiable on color mosaic aerial photographs, allowing the preparation of vegetation maps. The community types identified in this study are compared with previous studies in the high arctic.
Sensitivity of lichen phycobionts to dissolved air pollutants
Authors: Marti Jakob
Published: April 2011

Cultured phycobionts of various epiphytic lichens were exposed to aqueous solutions of either sulfite, nitrite, sulfate, or nitrate, simulating an acute pollutant stress for a short time. The impact of these pollutants was determined by measuring the chlorophyll content and the 14C-incorporation rates. Nitrate and sulfate proved to be nontoxic at pH 4, whereas distinct differences were noted in the sensitivity of the various phycobionts to sulfite and nitrite. In many of the species examined there were clear correlations with data available on the sensitivity of the whole lichen thallus. In some species, however, the phycobiont was either distinctly less sensitive or less tolerant than would be expected from ecological studies on the geographical distribution of the lichen.
Resource allocation in high-arctic vascular plants of differing growth form
Authors: Maessen O. , Freedman B. , Nams M. L. N. , Svoboda J.
Published: April 2011

Resource allocation strategies are described for a range of vascular plant species of a high-arctic lowland oasis, located adjacent to Alexandra Fjord, Ellesmere Island, N.W.T. The patterns of allocation of biomass and major nutrients (N, P, K, Ca, and Mg) differed greatly among the 16 species, which represented six growth forms (biennial herbs, perennial herbs, graminoids, cushion plants, deciduous dwarf shrubs, and evergreen dwarf shrubs). The dominant growth strategy was that of the stress tolerator, well adapted to cold, dry, and exposed situations. This strategy is characterized by low annual net production, a small proportion of resources allocated belowground, a large proportion of resources allocated to the attached litter compartment, and internal nutrient cycling. Ruderal growth strategies were evident in such species as Cochlearia fenestrata and Draba groenlandica, which occupied disturbed habitats. These species had a large proportion of resources allocated to sexual reproductive tissues. Perennial herbs exhibited intermediate strategies, and they occupied a wide range of habitats.
Vascularisation de la fleur de Calla palustris (Araceae)
Authors: Barabé Denis , Labrecque Michel
Published: April 2011

Based on floral vascular system, the authors analysed the problem of pseudomonomeria, and the inter-generic relationships within the Calloideae. The hermaphrodite flowers of Calla do not have a perianth. The superior, unilocular ovary is surrounded by 10 to 12 extrorse stamens. Most of these flowers have an ovary wall which receives three carpellary traces. These three traces divides again to produce 9–12 bundles. At the base of the ovules, an oval vascular plexus can be seen on which the traces of the ovules are inserted. It originates from three carpellary bundles, even though it is connected to certain staminal traces. The anatomical study showed that the syncarpous gynoecium of Calla is composed of three carpels that are joined edge to edge. The bitegmic, anatropous, apotropous ascending ovules are located on a basal placenta. The number of ovules varies from 4 to 10. The basal placentation of Calla is of the basal-axile type. It derives from an axile placentation which is similar to that found in Lysichitum. Among the Calloideae, it is with Orontium aquaticum that Calla palustris shares the greatest number of characters: superior ovary, unilocular, tricarpellate gynoecium, basal placentation, and a reticulate pollen. In Orontium, the existence of 6 tepals and 6 stamens was noted while in Calla, 10–12 stamens were observed. It is possible that 6 of the 12 stamens of Calla, correspond to the 6 tepals of Orontium. The subfamily Calloideae is a heterogeneous taxon at the level of floral morphology.
A comparison of cone and needle characters in Abies: a test of a new theory of evolution
Authors: Maze Jack
Published: April 2011

One part of a new theory of evolution proposed by Wiley and Brooks is that evolution results in continually increasing complexity. This leads to the unique prediction that once speciation occurs and species are embarked on independent histories, developmentally independent characters will become more correlated. This was tested by comparing cone and needle characters for some Abies species from different levels in a hierarchy, i.e., from the population level, where one would predict low correlations, to the supraspecific level, where one would predict high correlations. In a general sense, these predictions were realized. The results also indicated approximately equal correlations between cone and needle characters at levels below the species. These results were unexpected since one would predict that allopatric populations in the analyses would be embarked on independent histories because they are reproductively isolated and this would show correlations between cone and needle characters. This implies that reproductive isolation may not be a basic evolutionary event but that the dynamic interaction between entropic decay of information and reproductive linkages, the view presented in the new theory of evolution mentioned above, may be.
Changes in cytokinin concentration during early development of American sycamore leaves
Authors: Renfroe Michael H. , Brown R. W.
Published: April 2011

Concentrations of cytokinin-like substances (CKs) change rapidly during early leaf expansion of American sycamore (Platanus occidentalis L.). Endogenous CKs, measured by bioassay, are highest in the smallest leaves and decline several hundredfold as leaves rapidly enlarge. These rapid phytohormone changes during development demonstrate the need to carefully standardize sample collection. For some developmental or comparative studies leaf size may be a suitable criterion.
The influence of preinfection cold hardening and disease development period on the interaction between barley yellow dwarf virus and cold stress tolerance in wheat
Authors: Andrews C. J. , Paliwal Y. C.
Published: April 2011

Cold hardness and ice encasement tolerance of 'Fredrick' and 'Norstar' winter wheats as affected by infection with barley yellow dwarf virus (BYDV) were determined during inoculation, disease development periods, and low-temperature growth. Plants were either prehardened to cold, or warm grown before infection; two disease development periods (DDP) were utilized. A long DDP induced greater pathogenesis and greater hardiness reduction than a short DDP. The effect of virus infection on the final level of hardiness of prehardened plants was generally greater than on that of nonprehardened plants. Viral infection reduced hardiness up to 3.5 °C in 'Fredrick' wheat, but reductions of 6–10 °C below hardiness potential were recorded after certain environmental regimes allowing disease development. Ice tolerance was reduced by BYDV infection in early low-temperature growth but was increased by infection after 4 months at low temperature. This increase in survival was associated with higher dry matter content in infected than in noninfected plants.
Recent trophic changes in Kootenay Lake, British Columbia, as recorded by fossil diatoms
Authors: Ennis G. L. , Northcote T. G. , Stockner J. G.
Published: April 2011

Short sediment cores (ca. 40 cm long) were collected from three locations within Kootenay Lake, B.C., and the occurrence of diatoms within the cores was recorded and analyzed. This analysis of fossil diatoms in the sediments of Kootenay Lake has provided evidence for environmental change as a result of man's activities in the drainage basin. Changes to the trophic status of the lake are related to operation of a phosphate fertilizer plant (beginning in 1953) on the major southern inlet river and to more recent water regulation on both the southern and northern major inlet rivers. Diatom numbers and volumes at the deeper core depths were lowest. Diatom species in the deeper core depths consisted of an assemblage of oligotrophic and eutrophic indicators corresponding to high (but not critically high) phosphorus loading to the lake. Above the 5-cm depth, numbers increased and peaked at the 3-cm depth in samples nearest the south end of the lake. At other locations within the lake, where sedimentation rates were lower, numbers peaked in the top centimetre of sediment. Concomitant with increased phosphorus loading diatom species indicative of oligotrophic conditions such as Cyclotella ocellata declined, while eutrophic indicators including Cyclotella glomerata, Melosira granulata v. angustissima, Stephanodiscus spp., Asterionella formosa, and Fragilaria crotonensis increased. Asterionella formosa and Fragilaria crotonensis showed highest abundances in the top 2 cm of the core. These species, which form a major component of the spring and fall diatom blooms, were responding to both increased nutrients and improved light conditions resulting from decreased freshet turbidity. The Araphidineae/Centrales ratio was not useful in classifying trophic changes in Kootenay Lake since numbers of centric diatoms did not decline with nutrient enrichments (although there was a dominance shift from oligotrophic centrics to eutrophic centrics). Shannon–Wiener diversity values remained high throughout the recent history of the lake.
Modelling geographic variation in the timing of shoot extension by ericaceous shrubs
Authors: Reader R. J.
Published: April 2011

The seasonal timing of shoot extension by three ericaceous shrubs (Ledum groenlandicum, Chamaedaphne calyculata, and Kalmia polifolia) was monitored at eight peat bogs along an 800-km latitudinal transect through Ontario, Canada, and at a transplant garden containing plants from four of the peat bogs. The timing of shoot extension varied among plants from different locations, both in the transplant garden and in the field. A regression model containing two independent variables (heat units (i.e., degree-days) and either the average annual degree-day total for a plant's geographic origin or the average frost-free period) could account for 95 to 99% of the seasonal plus intersite variation in shoot extension recorded in the transplant garden. The seasonal pattern of shoot extension predicted for each of the eight peat bogs with the regression model was close to the observed pattern in most cases. The average difference between predicted and observed percentages of shoot extension ranged from 4% for L. groenlandicum to 7% for K. polifolia.
Peroxidase, indoleacetic acid oxidase, and amylase activity in necrotic wheat hybrid and its parents
Authors: Chaturvedi Neera , Laloraya M. M.
Published: April 2011

At the seedling stage, growth pattern and changes in the activity of enzymes were studied in "necrotic" hybrid of wheat (Triticum aestivum) and its parents HI 617 (female) and HD 2160 (male). Growth of the hybrid is less when compared with either parent in light as well as in dark. In dark the hybrid shows higher activity of amylase, peroxidase, and indoleacetic acid oxidase than either parent. In light, however, the activity of peroxidase and amylase is intermediate between the two parents in the axis and root and higher than the parents in the endosperm of the hybrid. It appears that light modulates gene activity of the hybrid and in light the male-parent gene is dominant.
The hydraulic architecture of Thuja occidentalis
Authors: Tyree M. T. , Graham M. E. D. , Cooper K. E. , Bazos L. J.
Published: April 2011

Leaf specific conductivities (LSC's) were measured on stem segments excised from various points within the canopy of eastern white cedar trees, Thuja occidentalis L. LSC is defined as the water flow rate (kilograms per second) through a stem caused by a unit of pressure potential gradient (megapascals per metre) per unit leaf surface area supplied by the stem (square metres). LSC's were measured on stems of various diameters and were found to vary over a factor of 30 in magnitude from 1 × 10−5 kg s−1 m−1 MPa−1 for stems 1 mm in diameter to 3 × 10−4 kg s−1 m−1 MPa−1 for stems 100 mm in diameter. LSC was found to be related to stem diameter (D (millimetres)) by the following empirical formula: LSC = 9.58 × 10−6 × D0.727. LSC's measured on stem segments including a node had significantly lower LSC's than internodal stem segments of the same length. Various water relations parameters were measured on cedar trees on a diurnal basis including evaporative flux, leaf resistance to evaporation, shoot water potential, air temperature, and air humidity. Water potential isotherms were also measured on excised green shoots. From the above data, we estimate that about 15% of the total water evaporated from green shoots comes from stored water while the shoot water potentials are growing progressively negative. The typical peak evaporative flux in midday was 1.5 × 10−5 kg s−1 m−2; using this value and our measured LSC's we estimate that the pressure potential gradients in the stems must be 50 kPa m−1 in stems 100 mm in diameter and 1500 kPa m−1 in stems 1 mm in diameter. Pressure potential gradients were measured in stems 30 to 50 mm in diameter by the pressure bomb technique and were found to be 69 kPa m−1 during a typical afternoon and this confirms the accuracy of the above estimates.
Influence de la température sur les membranes de sphérosomes de cellules méristématiques de luzerne
Authors: Bolduc Réginald
Published: April 2011

The radicular meristematic cells of Medicago sativa L., cv. Saranac, contain spherosomes 0.2–1.3 μm in diameter distributed throughout the cytoplasm. These organelles usually have a spherical shape, react positively with Sudan black and contain osmiophilic material. This material can be dissolved in ethyl ether – ethanol 2:1 but not in petroleum ether. In tissues fixed in different manners, from plants growing under different conditions, the spherosomes possess an envelope consisting of two unitary membranes. This envelope is in structural continuity with the endoplasmic reticulum. During senescence, membranes separate from spherosomes thus initiating the formation of one vacuole which surrounds this organelle. The spherosome dense material eventually undergoes degradation within this vacuole.
Variability of a water-insoluble protein fraction from maize pollen
Authors: Shortess David K.
Published: April 2011

An aqueous-insoluble protein fraction has been extracted from maize pollen using a solvent containing phenol, acetic acid, and water (2:1:1, w/v/v) in 3 M urea. The solvent extracted 26% of the total protein from the pollen. The proteins of this fraction were subjected to polyacrylamide gel electrophoresis using the same solvent system. A comparison of the banding patterns of 10 inbred lines and a commercial hybrid revealed a high level of variability among the lines. Some variability was also observed within lines. The degree of variability was similar to that observed in maize seed proteins extracted with the same solvent. However, a comparison of overall banding patterns and individual band intensity differences among the lines examined revealed no apparent homology between the proteins of the two tissues.
The mineral nutrition of Luffa aegyptiaca
Authors: Okusanya Olubukanla T.
Published: April 2011

Five greenhouse experiments and a field experiment were carried out to determine the nutrient requirements of Luffa aegyptiaca L. by quantitatively determining the effects of nitrogen, phosphorus, potassium, and calcium on its growth in sand culture and in poor lateritic soil. The effects of three pH regimes were also investigated. The species grew best at pH 6.5. When grown in a medium of pH 3.5, there was a significant reduction in growth at low nutrient levels, but at high nutrient levels there was no appreciable reduction in growth. The lack of any of the four nutrient elements limited growth in sand culture, but nitrogen and phosphorus seem to be the major elements limiting growth in the poor lateritic soil with calcium being required in lesser quantities. Suggestions were also made as to the possible application of these results to increase the production of L. aegyptiaca fruits, the fibrous interiors of which are now in great demand as sponges.
Effect of cycloheximide on the freezing tolerance and ultrastructure of cortical parenchyma cells from mulberry twigs
Authors: Niki T. , Sakai A.
Published: April 2011

Experiments were performed using cycloheximide (CHI) on cortical parenchyma cells from mulberry twigs (Morus bombyciz cv. Gorogi) to understand the relationship between the sequence of cytological changes suggesting replacement of the plasmamembrane and the rapid increase in freezing tolerance. Cortical cells from twigs collected on October 16 and 27, which were hardy to −10 and −15 °C, respectively, were still alive after cooling to −70 °C if they had been exposed to −3 °C for 10 to 12 days. In these hardened cells, appearance of microvesicles (MVs) in the peripheral cytoplasm and fusion of these MVs with plasmamembrane were characteristically observed. Neither cytological change nor increase of freezing tolerance was observed in cells treated by CHI before their exposure to −3 °C for 10 to 12 days. However, the suppression of such changes by CHI treatment was effective only in cells which were hardy at −10 to −15 °C and not in the cells of twigs collected on November 4, which were hardy to −20 °C. Consequently, synthesis of some functional proteins during hardening was required for the further development of freezing tolerance, and synthesis had been accomplished before the cells became hardy to −20 °C. Ultrastructural changes brought about by CHI treatment suggest that synthesis of some functional proteins related to the presumed changes of plasmamembrane occurs during hardening.
Resistance to Septoria nodorum in a durum wheat cultivar as determined by stage of host development
Authors: Mullaney E. J. , Scharen A. L. , Bryan M. D.
Published: April 2011

Seedlings of the spring durum wheat cv. Giorgio 396 (CI 15111), show a high level of resistance to S. nodorum while the mature plants are very susceptible. Tests under greenhouse conditions showed seedlings of this cultivar to have a significantly higher level of resistance to isolates of S. nodorum than seedlings of a susceptible cultivar in its seedling stage; but field and greenhouse inoculations of the mature plant showed it to be susceptible in terms of both disease symptoms expressed and reduction in weight of the kernels produced. This seedling resistance may be of potential value if it can be incorporated into cultivars grown in environments where seedling resistance is essential, or incorporated along with other genes for resistance to produce cultivars with a high level of resistance to S. nodorum over several growth stages.
Isoforms of glutamine synthetase in Panicum species having C3, C4, and intermediate photosynthetic pathways
Authors: Hirel B. , Layzell D. B. , McCashin B. , McNally S. F. , Canvin D. T.
Published: April 2011

The number, relative activity, and immunological nature of glutamine synthetase (GS) isoforms were studied in three species of Panicum, each differing in the nature of their photosynthetic system: P. bisulcatum, a C3 plant; P. milioides, a C3–C4 intermediate; and P. miliaceum, a C4 plant. Ion-exchange chromatography of leaf extracts for all three species revealed a peak of GS activity eluting at 0.23–0.32 M NaCl. These peaks had similar elution characteristics to GS isolated from chloroplasts of barley. Also, as in the barley chloroplastic GS, they were poorly recognized by antibodies from barley cytosolic GS (GS1). These peaks were therefore identified as GS2 and were thought to be chloroplastic in origin. A second peak of GS activity eluting at 0.18 M NaCl was found to account for 0, 21, and 45% of the total GS activity in the C3, C3–C4 intermediate, and C4 leaves, respectively. It had similar elution characteristics to the cytosolic GS from barley and was readily bound by the antibodies made against barley cytosolic GS (GS1). This enzyme, identified as GS1, was thought to be cytosolic in origin. The results demonstrate that even within a single genus, the GS isoform composition is closely related to the type of photosynthetic pathway present within the leaf tissue.
Seedling morphology and anatomy of eight Cicer species and their taxonomic value
Authors: Nozzolillo Constance
Published: April 2011

Seedling characters including anthocyanin pigmentation of eight species of Cicer, C. arietinum, C. pinnatifidum, C. judaicum, C. cuneatum, C. chorassanicum, C. anatolicum, C. montbretii, and C. pungens, representing all four sections of the genus were examined. The results support the concept of a separate monogeneric tribe, the Cicereae Alef.
Early development of Rhizobium-induced root nodules of Parasponia rigida. II. Nodule morphogenesis and symbiotic development
Authors: Lancelle Susan A. , Torrey John G.
Published: April 2011

The Rhizobium-induced root nodules of Parasponia rigida (Ulmaceae) outwardly resemble those formed on actinorhizal plants, being coralloid in shape and consisting of multiple, branched lobes. The details of nodule morphogenesis also resemble more closely those which occur in an actinorhizal association than a typical Rhizobium–legume association and include prenodule formation, initiation of modified lateral roots which are termed nodule lobe primordia, and rhizobial colonization of tissues derived from the nodule lobe primordia to form the primary nodule lobes. Mature nodule lobe structure is actinorhizallike. Each lobe has an apical meristem and a central vascular cylinder which is surrounded by an uninfected inner cortex and then a zone of infected tissue. Peripheral to the infected tissue is an uninfected outer cortex. Infection threads and intercellular rhizobia progress continuously toward the apical meristem but do not infect the meristem itself. The establishment of the symbiosis in the host cells involves continuous thread formation after the initial infection until the host cells are nearly filled with rhizobia enclosed in threads. The rhizobia remain in threads throughout the symbiotic relationship and are not released from the threads as occurs in bacteroid formation in legumes.
Disseminative fitness of Endothia parasitica containing different agents for cytoplasmic hypovirulence
Authors: Russin J. S. , Shain L.
Published: April 2011

Three different agents for cytoplasmic hypovirulence (CH) were transferred individually to a virulent (V) isolate (EP 155) of Endothia parasitica. The CH agent HI2 obtained from an Italian isolate of E. parasitica had little effect on the ability of EP 155 to sporulate asexually or to cause cankers on American chestnut. CH agent HM2 from a Michigan isolate reduced these parameters by 60 and 80%, respectively, whereas CH agent HT2 from a Tennessee isolate reduced both parameters almost totally. Agent HT2 was markedly less efficient than HI2 or HM2 at conversion of mycelium and stromata in cankers incited by EP 155. Agent HT2 also was transmitted through a much lower percentage of conidia than were HI2 or HM2. This did not appear to be a barrier to the spread of cytoplasmic hypovirulence, however, as very few CH conidia in droplets of condial suspensions were required for conversion of resultant colonies to CH. Frequency of transmission of CH agents through conidia produced in vivo and in vitro was similar and did not change over time. Longevity of conidia containing agent HI2 was similar to that for V conidia on all substrates tested.
Evaluating allometric shrub biomass equations fit to generated data
Authors: Brand Gary J. , Smith W. Brad
Published: April 2011

Several published allometric biomass equations may be available for a particular species. For some applications a method is needed to produce a single equation for the species. Several investigators have produced such an equation by refitting the combined original data used to develop the separate equations. We evaluated a method, previously examined for several hardwood tree species, for producing an equation fit to data generated from the published equations when the original data are not available. For the three tall shrub species groups (Acer spicatum Lam., Amelanchier spp., and Salix spp.) examined, the generated weighted data equation fit the combined weighted data as well as or better than the published equations.
Optimisation de la croissance et de la sporulation de Conidiobolus obscurus en milieu défini
Authors: Latgé J. P. , Sanglier J. J.
Published: April 2011

Physical and nutritional factors influencing the growth and sporulation of Conidiobolus obscurus (Hall et Dunn) Remaudière et Keller were studied using simple and fragmented factorial designs and centered composite designs. Culture conditions allowing maximum sporulation were a temperature of 20 °C, complete darkness, and a near neutral pH of around 6.5. Under our experimental conditions, dextrose influenced neither the growth nor the sporulation of C. obscurus. The cations stimulating the formation of azygospores were magnesium and to a lesser extent zinc and manganese. Sulphur must be added to the medium in a reduced or oxydized form. Phosphates must be present in the culture medium, but at a concentration less than 30 mM/L. Vitamins stimulating sporulation were thiamine, biotin, and folic acid while pantothenic acid favoured growth. Among the 20 amino acids tested, proline, leucine, methionine, glutamic and aspartic acids, glutamine, asparagine, histidine, phenylalanine, lysine, and arginine were the most favourable for growth and sporulation of C. obscurus. Growth and sporulation in the optimized defined medium containing 11 amino acids, four vitamins, four salts, and dextrose were comparable to the best results obtained in a nondefined medium composed of dextrose and yeast extract.
Cytologie ultrastructurale de l'anthère de Saxifraga. I. Période d'initiation des précurseurs des sporopollénines au niveau des principaux types exiniques
Authors: Hideux Michel , Abadie Michel
Published: April 2011

The period of initiation of sporopollenin precursors studied by transmission electron microscopy in the anthers of three species of the genus Saxifraga (S. cymbalaria ssp. huetiana, sempervivum and clusii) reveals two main phases. They are characterized successively by the elaboration of the ectexine (outer layer of the exine composed of sporopollenin) and endexine (inner layer of the same wall). This phenomenon has been observed in the tapetal periplasm and the sporal periplasm; the latter has been chosen as the reference point in establishing the chronology of the ontogenetic stages as well as the terminology of the sporopollenin structures. Proectexine and proendexine are distinctly stratified in the microspore while they become intermingled in the proorbicules. Proendexine could be elaborated according to a fluid mosaic model in relation to the plasmalemma. During this period, the relationships revealed between the plasmalemma–glycocalyx system (glycolemma) and the cytoskeleton (microtubules, microfilaments, and microfibrils) are emphasized. Thus, their functional role in the setting up of sporopollenin precursors is suggested.
A comparison of the flagellar apparatus in Phytophthora, Saprolegnia, Thraustochytrium, and Rhizidiomyces
Authors: Barr Donald J. S. , Allan Paula M. E.
Published: April 2011

The rootlet systems, kinetosomes, and transition zones in zoospores of Phytophthora parasitica, Thraustochytrium aureum, and Rhizidiomyces apophysatus and secondary zoospores of Saprolegnia diclina are compared. Rootlet systems in P. parasitica and S. diclina are very similar and there are only minor differences between these taxa in morphology of their transition zones. In P. parasitica and T. aureum a number of differences exist in the rootlet systems, but the position and orientation of individual rootlets are similar. There are also differences between these taxa in the alignment of their kinetosomes, the morphology of their kinetosome cores, and transition zones. Rhizidiomyces apophysatus has rootlets that correspond in position and orientation to P. parasitica, but there are not as many rootlets and these are morphologically distinctive. However, R. apophysatus and S. diclina have flagellar transition zones that are morphologically alike. Thus, probably the Hyphochytriomycetes are phylogenetically quite closely related to the Saprolegniales and more distantly related to the Peronosporales. In contrast, the Thraustochytriales are distantly related to the Oomycetes and Hyphochytriomycetes, but nonetheless similarities in the flagellar apparatus indicate that all have a common ancestor.
Extrême précocité et conditions thermiques du développement apical et floral chez Claytonia caroliniana var. caroliniana
Authors: Grandtner Miroslav M. , Gervais Camille
Published: April 2011

The apical and floral development of Claytonia caroliniana var. caroliniana has been studied concurrently with soil temperature, in a sugar maple forest of the Stoneham mountain, Québec. Apical cellular activity begins early in May, while the flowering stems of the year are present. At the beginning of July, external apical development becomes visible. In the first days of August, 9 months before flowering, the foliar and floral structures of the next year are already present in the soil. Meiosis takes place at the beginning of October and first pollen mitosis follows shortly after, in the middle of the same month. From that time, well developed individuals, without chlorophyll, are present just under the litter. They can occasionally turn green and reach the upper surface of the litter in November or December, where they will spend wintertime under the snow, at a temperature oscillating between 0 and −4 °C. This behaviour is quite close to the survival strategy of hemicryptophytes. The active epigeous growth period begins in the middle of April, with the melting of snow. Second pollen mitosis and flowering take place at this time, rapidly followed by seed setting, dissemination, and destruction of the aerial portion of the plant. Cytoecological investigations to study possible influence of environmental factors on chromosomal anomalies in primordia should thus be conducted during the year preceding the flowering of Claytonia.
Evaluation of the infectivity and effectiveness of indigenous vesicular–arbuscular fungal populations in some agricultural soils in Burgundy
Authors: Gianinazzi-Pearson V. , Gianinazzi S. , Trouvelot A.
Published: April 2011

Infectivity, measured as propagule numbers and root colonization rates, and effects on plant growth of indigenous vesicular–arbuscular fungal populations varied among soils from 10 different localities in Burgundy. These three characteristics of the populations were not necessarily related to each other nor to the physicochemical properties of the soils. It was possible, using relatively simple methods, to assess the potential for vesicular–arbuscular fungal inoculation in the different soils.
Cytological studies of the early stages of powdery mildew in barley and wheat. XI. Autofluorescence and haloes at penetration sites of appressoria of Erysiphe graminis hordei and Erysiphe pisi on barley coleoptiles
Authors: Kunoh H. , Kuno K. , Ishizaki H.
Published: April 2011

Cytological and physiological comparisons between autofluorescence and haloes which appeared at penetration sites of appressoria of Erysiphe graminis and Erysiphe pisi on barley coleoptiles were made using dye stains and fluorescence microscopy. Haloes induced by these fungi on barley coleoptiles were successfully detected by various dyes when the inoculated coleoptiles were treated with 70% ethanol at 80 °C for 30 min before staining. Responses of haloes on coleoptiles to basic and acid dyes were very similar to those on barley leaves which have been reported earlier. In time-course studies, haloes were not detected until at least 15 min after initiation of cytoplasmic aggregation. The occurrence of haloes was suppressed by supplemental Ca2+, but unaffected by K+, Na+, and Li+. Similar results were obtained in haloes induced by both fungi. Autofluorescent regions remained in situ after the inoculated coleoptile cells were plasmolyzed, suggesting that this phenomenon might be closely associated with host cell walls. As reported earlier, autofluorescence preceded the appearance of cytoplasmic aggregates by 1–10 min and, moreover, its appearance was enhanced by divalent cations such as Ca2+, Mg2+, and Mn2+, but not by monovalent cations such as K+, Na+, and Li+. Based on these results and earlier studies, it was concluded that the autofluorescence and haloes represented different responses in host cell walls to the penetration activities of both pathogenic and nonpathogenic fungi.