bluuebunny/crossref_metadata_2025 huggingface dataset:
Soybean flavonol glycosides: identification and biochemical genetics
Authors: Buttery B. R. , Buzzell R. I.
Published: September 2008

The products of controlled hydrolysis and oxidation of the flavonol 3-O-glycosides in soybean leaves were studied. From the study the kaempferol and quercetin glycosides were identified as the glucoside, sophoroside, gentiobioside, rutinoside, neohesperidoside, 2G-glucosylrutinoside, 2G-glucosylgentiobioside, 2G-rhamnosylrutinoside, and 2G-rhamnosylgentiobioside. The last three glycosides have not been reported before. The probable mode of biosynthesis is outlined; each of the four diglycosides is formed by a dominant flavonol glycoside gene, while the four triglycosides are formed by duplicate gene action. When glucose is added to the monoglucoside in the biosynthesis of diglycosides and triglycosides, Fg1 codes for a β(1–6) linkage and Fg3 codes for a β(1–2) linkage. Similarly, with rhamnose addition, Fg2 codes for an α(1–6) and Fg4 codes for an α(1–2) linkage. Hence, Fg1 or Fg2 can interact with Fg3 or Fg4 to form the branched triglycosides because they code for linkage to different carbons of the basic glucose unit. On the other hand Fg1 and Fg2 both code for a linkage to carbon-6 of the glucose, and Fg3 and Fg4 both add to carbon-2 of the glucose, thus there is no interaction within each of these pairs of genes to form branched triglycosides.
Growth of suspension cultures of plant cells (Ipomoea sp.) at various temperatures
Authors: Rose Dyson , Martin S. M.
Published: September 2008

Studies on the growth of batch suspension cultures of a plant cell line, initiated from Ipomoea sp. root explants, at temperatures ranging from 15 to 34 °C are reported. Maximum growth of cultures of this cell line occurred between 25 and 32 °C, with temperature variations within this range having little effect on growth rates based on dry cell yields. Cultivation at 20 °C substantially reduced the growth rate. However, cells grown at 20 °C failed to grow on transfer to fresh medium at 20 °C. Thus cultivation at suboptimum temperatures is not a satisfactory method for routine maintenance of the suspension culture.
An analysis of the vegetation of Sphagnum-dominated kettle-hole bogs in relation to environmental gradients
Authors: Vitt Dale H. , Slack Nancy G.
Published: September 2008

Eight Sphagnum -dominated kettle-hole bogs in northern Michigan were analyzed to elucidate vegetation patterns of both vascular plants and Sphagnum species in relation to measured bog gradients. Methods of both direct and indirect gradient analysis, including ordination and cluster analysis, were used. Community types as delineated in the ordination are discussed, including species distribution for Sphagnum and vascular plants. Segregation of community types followed gradients of pH, light, and calcium and magnesium ion concentrations. Two types of kettle-hole bogs were distinguished surrounding acid and alkaline bog lakes respectively, each with its own continuum of community types.
Recherches sur les Alaria (Phaeophyceae) de l'est canadien. II. Traitement de sporocystes de Laminariales par la réaction nucléale de Feulgen "in toto"
Authors: Demalsy P. , Feller-Demalsy M.-J.
Published: September 2008

The authors describe a method for the caryological study of whole sporocysts of Laminariales after treatment by the nucleal Feulgen reaction in toto.
Differential sensitivity of Verticillium dahliae, V. albo-atrum, and V. nigrescens to benomyl
Authors: Hall Robert
Published: September 2008

Small but significant (P = 0.05) differences in sensitivity to benomyl in vitro were observed among collections of Verticillium dahliae (21 isolates), V. albo-atrum (9 isolates), and V. nigrescens (8 isolates). Mean species effective dose (milligrams per liter) (ED50) values were, respectively, 0.36, p.26, and 0.19 (significantly different from one another). The corresponding mean species values for the slope of the probit inhibition – log dose curve were 10.55, 12.55 (not significantly different), and 6.87 (significantly different). However, positive identification of an isolate by its ED50 value or the slope of the dose–response curve was not possible because of overlap in the range of values within species.
Structural hybridity and supernumerary chromosomes in a diploid Tradescantia hirsuticaulis
Authors: Chinnappa C. C.
Published: September 2008

Cytological study of a diploid (2n = 12) population of Tradescantia hirsuticaulis Small from Stone Mountain, Georgia, revealed striking variation in four plants growing in a cluster, indicating that they constitute different genotypes. The occurrence of B chromosomes, fragments, and aneusomaty in the plants is associated with structural hybridity in the chromosomes. Two plants were homozygotes with simple meiotic pairing, one was heterozygous for a reciprocal translocation, and the other was a heterozygote for two interchanges as well as for inversions. The behavior and the origin of B chromosomes, fragments, and structural hybridity are discussed.
Initial stages of cell wall formation in the dinoflagellate Peridinium trochoideum
Authors: Kalley John P. , Bisalputra Thana
Published: September 2008

The formation of the cell wall in the marine dinoflagellate Peridinium trochoideum was studied using light and electron microscopy. In mature, interphase cells, densely staining inclusions termed ‘prothecal bodies’ were found distributed throughout the cytoplasm. Before ecdysis each amorphous prothecal body developed into many vesicles, each of which contained fibrous material in an electron-transparent matrix. The vast number of vesicles so formed may have increased the cell's osmotic pressure enough to initiate ecdysis. At ecdysis the thecal plates and overlying membranes were lost and a new wall was formed by deposition of intact prothecal vesicles at the protoplast surface. The newly formed wall was continuous over the protoplast and no plates existed as such
Classification of vegetation data from an open beach environment in southwestern Ontario: cluster analysis followed by generalized distance assignment
Authors: Bradfield Gary E. , Orlóci László
Published: September 2008

Vegetation data from a tract of open beach in southwestern Ontario were classified in two stages to aid in the description and mapping of the plant communities of the area. Firstly, the similarity matrix generated for half the sample was analyzed by a method of similarity clustering designed to produce homogeneous and distinct groups. The four groups that emerged conformed with the main topographic features in the study area, these being the shoreline zone, the middle beach zone, the wet slack zone, and the upper beach zone. This four-type classification was then imposed upon the rest of the sample, using generalized distance (D2) as the assignment function. The problem faced in the inversion of the singular group covariance matrix (5k) for each group was overcome by orthogonal transformation. Although considerable computation was involved, the results indicated that D2, when used in a deterministic sense, has much potential in helping to allocate individuals to groups.
Inorganic pyrophosphatase activity during rice leaf senescence
Authors: Kar M. , Mishra D.
Published: September 2008

The activities of the acid and alkaline inorganic pyrophosphatases (EC. 3.6.1.1) were determined in attached and detached senescing rice leaves. The acid inorganic pyrophosphatase had the pH optimum at 5.0 and was inhibited by Mg2+, while the alkaline inorganic pyrophosphatase had the pH optimum at 8.6 and had an absolute requirement for Mg2+. The activity of the acid inorganic pyrophosphatase increased, but the activity of the alkaline inorganic pyrophosphatase decreased during senescence of both attached and detached rice leaves. Benzimidazole and kinetin treatment prevented the changes, during senescence, in the activities of both the enzymes. Regression analysis showed strong correlation between chlorophyll, α-amino nitrogen, and acid and alkaline inorganic pyrophosphatase activity during senescence.
Conidial states of some Pragmopora and Tympanis species
Authors: Sutton B. C. , Funk A.
Published: September 2008

Pragmopycnis pithya gen. et sp. nov. is introduced for the conidial state of Pragmopora pithya (Fr.) Groves and is characterized by simple, solitary, brown pycnidia, integrated polyphialides, and hyaline, allantoid, aseptate conidia. A comparison is made with Sirodothis Clements, which provides an earlier name for Pleurophomella Höhnel, a name currently adopted for the conidial states of Tympanis Tode ex Fr. Sirodothis populnea (Thüm.) comb, nov., S. saligna (Höhn.) comb, nov., S. inversa (Fr.) comb, nov., and S. columnaris (Wallr.) comb. nov. are proposed for the named conidial states of four Tympanis species.
Etude ultramicroscopique des modifications cytologiques chez le blé d'hiver lors de l'endurcissement au froid
Authors: Rochat E. , Therrien H. P.
Published: September 2008

This paper describes a few cytological and ultrastructural modifications during the hardening process of two varieties of winter wheat differing in frost resistance. In leaf cells of the hardier variety, Kharkov, subjected to hardening conditions, the quick and complete disappearance of starch grains in chloroplasts, the undulation of nuclear and chloroplast membranes, and an increase in osmiophilic granules have been observed. In the less-hardy variety, Selkirk, after a month of hardening, starch grains persist in chloroplasts, osmiophilic granules diminish in number and intensity, and vesicles are formed between the double membrane surrounding the chloroplasts. These vesicles are finally liberated in the ground cytoplasm. Their role could be the elimination of substances such as denatured proteins of the chloroplasts.
Fine structure of teliospores of the cedar-apple rust Gymnosporangium juniperi-virginianae
Authors: Mims Charles W. , Seabury Frank , Thurston E. L.
Published: September 2008

Teliospores of the cedar-apple rust Gymnosporangium juniperi-virginianae were examined using transmission electron microscopy. Each ellipsoid spore is divided into two cells by a transverse septum. A second septum separates the basal cell of the teliospore from a long, hyaline, cylindrical pedicel. The fine structure of these septa is considered. The cytoplasm of the teliospore is very dense and contains a complement of cellular structures including ribosomes, vacuoles, mitochondria, and a large number of structures thought to be lipid bodies. Each cell of the teliospore contains a single nucleus, in which the chromatin is often considerably condensed. Two germ pore regions are present in each cell. The spore wall is thinnest in these regions and is different in structure than elsewhere around the spore.
Etude au niveau cellulaire de la différenciation in vitro et de novo de bourgeons végétatifs, de racines, ou de cal a partir de couches minces de cellules de type épidermique de Nicotiana tabacum Wisc. 38
Authors: Van M. Tran Thanh , Dien Nguyen Thi
Published: September 2008

not available
A new species of Triangularia from Ohio soil
Authors: Huang L. H.
Published: September 2008

Triangularia backusii n. sp. was isolated from a soil sample collected in Ohio, U.S.A., and was subjected to alcohol treatment. Triangularia backusii is characterized by oval to pyriform perithecia, elongate-clavate asci, and obovoid ascospores with hyaline, gelatinous appendages. The ascospores are two-celled with a transverse septum; the upper cell is obovoid with a truncate base and brownish black to black and the lower cell is triangular and pale brown to brown. The conidial state is assignable to the genus Phialophora. The new species differs from other known Triangularia species in having the largest ascospores.
The effect of climate on the photosynthesis of Picea mariana at the subarctic tree line. 1. Field measurements
Authors: Vowinckel T. , Oechel W. C. , Boll W. G.
Published: September 2008

Field measurements of the diurnal rates of photosynthesis of Picea mariana, the dominant tree species at the subarctic tree line, were made during the summers of 1972 and 1973 at Schefferville, Quebec (latitude 55° N). All relevant plant physiological and environmental parameters were also monitored. Photosynthesis was measured with an open gas analysis system with temperature-controlled cuvettes. Maximum daily rates were 2.0–3.5 mg CO2 g−1 dry weight h−1. Daily totals were between 15 and 30 mg CO2 g−1 dry weight. Temperature was unimportant in affecting daily photosynthesis totals during the summer months. The photosynthesis vs. needle temperature curve had an optimum of 15C. Dark respiration rates were 0.2–0.4 mg CO2 g−1 dry weight h−1 at 15C. The photosynthesis vs. light intensity curve was saturated at 0.8 ly min−1 (1.0 μE cm−2 s−1 PhAR.). As a result, heavy cloud cover considerably reduced daily photosynthesis. No seasonal variations in photosynthesis over June, July, and August were observed. No differences in maximum rates occurred between the three experimental sites. Needle temperatures within the cuvettes were 2–4C above air temperature under full sunlight (1.2 ly min−1). Needle temperatures under natural conditions were up to 7C above Stevenson screen temperatures and fluctuated rapidly with changes in turbulence.
Studies on lichen-dominated systems. XI. Lichen–heath and winter snow cover
Authors: Larson D. W. , Kershaw K. A.
Published: September 2008

Several tundra beach ridges, adjacent sedge meadows, and forested areas some distance inland were examined in midwinter, late winter, and early spring to assess the potential importance of variations in snow cover to the underlying vegetation.Tops of beach ridges were found to be nearly snow-free all winter and were fully exposed early in the spring. Sedge meadows and forested areas had a thicker cover.The vegetational characteristics of each area appear adapted to the winter snow conditions.
Ultrastructural changes in nuclear membranes and organelle associations during mitosis of the aquatic fungus Entophlyctis sp.
Authors: Powell Martha J.
Published: September 2008

Electron microscopic observations on an endobiotic chytrid, Entophlyctis sp., have revealed a mitotic apparatus which is presently unique among fungi. Daughter nuclear envelopes are reconstituted from cisternae apparently proliferated by the inner membrane of the nuclear envelope. Before nuclear division, centrioles replicate and migrate to the poles of the nucleus. Large pores appear at this time in a depression of the nuclear envelope opposite the paired centrioles. This region of the envelope fragments and leaves polar fenestrae as spindle microtubules appear in the nucleus. The inner membrane of the nuclear envelope then invaginates and proliferates cisternae until a layer of inner membrane cisternae lines the original nuclear envelope at late metaphase. Connections between the inner membrane of the original nuclear envelope and the cisternae persist until telophase. As the spindle elongates and the inner membrane cisternae fuse centripetally to form a reticulum around the chromatin mass, the original nuclear envelope opens more at the poles. The reticulum becomes the nuclear envelope of the new daughter nuclei. When the original envelope finally disperses, it is distinguishable from the endoplasmic reticulum only by the presence of pores. Microbodies are consistently associated with the original nuclear envelope and appear adjacent to the new daughter envelopes at the end of telophase. Densely staining arms project from the sides of the primary centrioles toward the polar mitochondria.
A method for controlling plant water potentials for studies on the influence of water stress on disease susceptibility
Authors: Schoeneweiss Donald F.
Published: September 2008

A simple, inexpensive humidity cabinet is described which can be assembled inside a standard walk-in growth chamber. When container-grown tree or shrub seedlings were placed in the cabinet and held under complete darkness, high humidity, and constant temperature, xylem water potentials were at or near equilibrium after 2 days and remained relatively constant throughout a subsequent 7-day incubation period. Rapid, reproducible measurements of xylem water potentials of leaves and (or) shoots were made with a pressure bomb, leaving plants basically intact for studies on the influence of water stress on disease susceptibility.
The lichen, bryophyte, and vascular plant flora and vegetation of the Landing Lake area, Prince Patrick Island, Arctic Canada
Authors: Bird Charles D.
Published: September 2008

The relative abundance and ecology of 123 lichens, 12 liverworts, 1 peat moss, 59 mosses, and 40 vascular plants are described from the southeastern part of Prince Patrick Island, 76° N latitude. One hundred and three of the lichens, 25 of the bryophytes, and 6 of the vascular plants are first reports for the island. One lichen, Blastenia arctica, is reported for the first time from North America. One hundred and seventy of the species were found on the ground, 51 on rock, 9 on decaying plant material, 9 on bone, 5 on fossil wood, 4 on caribou dung, and 2 on mosses. Sixteen habitat types are described, based upon a relevé analysis of 31 different sites. A percentage of the lichens (95.1%), of the bryophytes (95.8%), and of the vascular plants (60.0%) encountered have a Circumpolar distribution. A percentage of the lichens (3.3%), of the bryophytes (1.4%), of the vascular plants (22.5%) have an American distribution. Eight species have an Amphi-Beringian distribution: lichens, 1.6%; bryophytes, 1.4%; vascular plants, 12.5%. One bryophyte (1.4%) and two vascular plants (5.0%) have an Amphi-Atlantic distribution.
Rhytidiella baranyayi n.sp., associated with cork-bark of aspen
Authors: Funk A. , Zalasky H.
Published: September 2008

Rhytidiella baranyayi n.sp. is described from corky proliferations of aspen (Populus tremuloides Michx.) in British Columbia, Canada, and from its growth in culture. A bitunicate ascomycete, it is suspected of being the causal agent of the disease with which it is consistently associated.
Mating patterns in self-compatible distylous populations of Amsinckia (Boraginaceae)
Authors: Ganders Fred R.
Published: September 2008

Progeny tests of naturally pollinated pin- and thrum-form plants of two species of Amsinckia were conducted to determine whether net selfing, random mating, or net disassortative mating occurred in natural populations. The locus determining flower form was used as a marker gene. Amsinckia spectabilis experienced close to random mating in a dense population, but in a small, diffuse population a high rate of selfing was indicated. Pin plants of Amsinckia vernicosa var. furcata experienced 44.3% net disassortative mating, and thrum plants in this species experienced complete (100%) disassortative mating.Compared with A. spectabilis, stigmas and anthers are about twice as far apart in A. vernicosa var. furcata; yet the pollinators are essentially similar, suggesting that greater separation of stigmas and anthers greatly improves the efficiency of distyly at promoting disassortative pollination. The two populations of A. spectabilis studied indicate that autogamy and (or) geitonogamy is much higher in diffuse populations. The results support previous studies that disassortative pollination is greater in thrum-form flowers than in pin flowers. Distyly without self-incompatibility can be an effective outbreeding system but is much more sensitive to variations in floral structure, population density, and pollinator behavior than are self-incompatible breeding systems.
Some notes concerning the measurement of water potentials of leaf tissue with specific reference to Tsuga canadensis and Picea abies
Authors: Talbot A. J. B. , Tyree M. T. , Dainty J.
Published: September 2008

Psychrometric measurements of the water potentials of leaves of Tsuga canadensis (L.) Carr. and Picea abies L. are compared with the water potentials of the shoots from which they came as measured by the pressure-bomb technique. Agreement between the two techniques is good when whole leaves are used in the psychrometer chamber, but deviations occur when bisected leaves are used in which the wound area to tissue volume is very small (1 to 2 cm2/cm3 of leaf tissue). Psychrometer determinations of water potential of these detached leaves are much more sensitive to cutting than in other species, e.g., sunflower and pepper (2). A more reliable means of measuring turgor and osmotic pressures in leaves is proposed.
The respiration and fertility of Pseudotsuga menziesii (Douglas fir) pollen
Authors: Binder Wolfgang D. , Ballantyne David J.
Published: September 2008

Respiration rate and fertility appeared to be closely correlated in Douglas-fir pollen. As the ability of the pollen to respire declined (with age or adverse storage conditions), so did the number of filled seed after pollination. A threshold value for loss of fertility in Douglas fir could be about 20 nmol O2 per 100 mg pollen per minute. Some Douglas-fir pollen lots with low respiration rates induced considerable seed cone abortion.
Changes in the peroxidase activity of subcellular fractions from aging Phaseolus hypocotyls
Authors: Truelove B. , Rodriguez-Kabana R. , Jones Larry R.
Published: September 2008

Changes in nitrogen contents and peroxidase activities of fractions isolated from hypocotyl tissue of Black Valentine bean (Phaseolus vulgaris L.) of increasing age were studied. As beans aged in darkness, a decreasing percentage of their nitrogen content was recovered in the isolated particulate fractions. Peroxidase activity of particulate fractions from dark-grown beans accounted for 49% of the total activity of both 3-day-old seedlings and 16-day-old senescing plants. Peroxidase specific activity of dark-grown tissue homogenates did not increase with plant age; however, after a certain period of growth, further aging resulted in increased peroxidase specific activity associated with the particulate fractions. Between day 3 and day 8 the patterns of peroxidase activity of the different fractions varied, but over the period day 9 to day 16, the patterns of all fractions were correlated. The nitrogen contents and peroxidase activities of fractions isolated from beans transferred from dark to light were different from those of fractions from beans of similar chronological age kept in darkness. Transfer of plants to light resulted in increased soluble peroxidase activity and prevention of the steep increase in particulate fraction activity recorded for dark-grown plants.
Ultrastructure of wilt syndrome caused by Verticillium dahliae. I. In chrysanthemum leaves
Authors: Robb Jane , Busch Lloyd , Lu B. C.
Published: September 2008

Ultrastructural changes occurred in chrysanthemum leaves infected by Verticillium dahliae Kleb. before and after the appearance of foliar symptoms. Before visual symptoms appeared, xylem vessels in the leaves contained large amounts of fungus and fibrillar material; by the time wilting occurred many vessels, particularly at the vein ends, were occluded by electron-dense plugs and swollen gelated vessel walls. Some of the chloroplasts in the mesophyll cells had started to degenerate before the first signs of flaccidity were noticeable, but other cytological changes were minimal until chlorosis occurred, at which time the xylem parenchyma had collapsed. Since plugging of leaf vessels preceded wilt and wilt preceded major ultrastructural changes in leaf mesophyll cells, we suggest that plugging of the xylem vessels is the major factor in inducing wilt in Verticillium-infected chrysanthemum.
Two physiological races of Tsuga canadensis in Wisconsin
Authors: Eickmeier William , Adams Michael , Lester Donald
Published: September 2008

Population differentiation in Tsuga canadensis (L.) Carr. from Wisconsin was tested by comparing seedlings grown from seed collected within the present range in the northeast and from seed collected in disjunct populations southwest of the present range. The seedlings, established in hydroponic culture, were subjected to two preconditioning temperature regimes and two water stress simulations. Net photosynthesis, dark respiration, and transpiration capacities were measured and internal leaf resistances were calculated.The southwestern Wisconsin population had a more favorable carbon dioxide balance at warmer tissue temperatures, particularly at low irradiance levels, and at higher osmotic potentials, than did the northeastern population, which was better adapted to lower tissue temperatures and lower osmotic potentials. Additional differences between seed sources in seedling morphology, transpiration rate, and water-use efficiency were found. These differences in morphology and physiological responses corresponded to the macroclimates in which these populations were found, southwestern Wisconsin being warmer and drier than the northeastern part of the state.
Transfer cells in tissues of the reproductive system of alfalfa
Authors: Johnson Lois E. B. , Wilcoxson Roy D. , Frosheiser F. I.
Published: September 2008

The reproductive system of alfalfa was studied for the presence of transfer cells. They were found in the tapetum of the anther, in the stylar canal, and along the ventral suture of the ovary wall. The cell wall of the filiform apparatus and the wall at the tip of the pollen tube resemble those of transfer cells.
Study of callus growth and organ formation in wheat (Triticum aestivum) tissue cultures
Authors: Dudits D. , Nemet G. , Haydu Z.
Published: September 2008

Callus cultures of wheat (Triticum aestivum L.) were established by incubation of segments from root tips, shoots of seedlings, and from rachis with B5 and T media. 2,4,5-Tri-chlorophenoxyacetic acid, Benazolin, and Banvel D (Dicamba) were found to be appropriate growth regulators for initiation and maintenance of wheat callus cultures. Cytokinins inhibited callus growth. This effect was less pronounced with zeatin than with kinetin and benzyladenine. Supplementation of media with cytokinins, however, increased the number of roots formed in the callus. Shoots and complete plants were regenerated from rachis and shoot callus.
Postinfectional inhibitors from plants. XV. Antifungal activity of the phytoalexin orchinol and related phenanthrenes and stilbenes
Authors: Ward E. W. B. , Unwin C. H. , Stoessl A.
Published: September 2008

Orchinol, loroglossol, and several related phenanthrenes and stilbenes obtained by laboratory synthesis were tested for antifungal activity, primarily in spore germination assays against Monilinia fructicola and Phytophthora infestons. The most active stilbene tested was 3,5-dimethoxy-3′-hydroxystilbene (mean effective dose (ED50) 5 × 10−5 M), at least comparable with the reported activity of the stilbene phytoalexin, pinosylvin. All the phenanthrenes and dihydrophenanthrenes tested were active, although assays were complicated by solubility problems. ED50 for orchinol was (5 × 10−5 M) and loroglossol had similar activity against P. infestons. Several phenanthrenes had higher activity, notably dehydroorchinol (ED50 vs. P. infestons 5 × 10−6 M), and warrant further study. A striking feature of the response of the test fungi to the phenanthrenes and dihydrophenanthrenes was the production of distorted and ruptured germ tubes, which may indicate a direct interference with growth processes at the tip. No evidence was obtained for translocation of orchinol in higher plant tissue.
Ultrastructure and cytology of pycnia, aecia, and aeciospores of Gymnosporangium clavipes
Authors: Kozar Frank , Netolitzky Hans J.
Published: September 2008

Aeciospores of Gymnosporangium clavipes Cooke & Peck have a surface characterized by a dense covering of baculate projections. Transmission electron micrographs (TEM) reveal a thick non-striated cell wall and a dense cytoplasm. Peridial cells have an inner surface studded with clavate projections. Scanning electron microscope (SEM) microgaphs confirmed earlier light microscopy studies of the existence of fiexious hyphae.
Morphological variation of achenes of Cannabis
Authors: Small Ernest
Published: September 2008

A number of authors have suggested that fruit characters are important in the taxonomic delimitation of Cannabis, particularly in contrasting wild and domesticated plants on the one hand and plants of limited and pronounced intoxicant potential on the other. Variation in achenes was assessed in plants cultivated for fiber and for drug purposes, and in plants growing outside of cultivation in various areas of the world. It was found that domesticated plants have large achenes which usually lack an adhering, patterned perianth and also lack an elongated base. In contrast, achenes of uncultivated plants are much more variable, ranging from those which closely resemble the fruits of domesticated plants to ones which are small and possess an adhering perianth and an elongated base. It appears that the latter morphological syndrome is adaptive in wild plants, and it is hypothesized that the degree of development of these characters in uncultivated plants is indicative of the extent of departure or independence from the effects of domestication.
Zonation des conditions d'enneigement en toundra forestière, Baie d'Hudson, Nouveau-Québec
Authors: Payette Serge , Ouzilleau Jacques , Filion Louise
Published: September 2008

Data on snow depth and snow density of various forest–tundra coniferous stands are presented in this paper. A latitudinal pattern in snow conditions is observed in the forest–tundra environment, as predicted from the facts that are obtained when this phytogeographical region is subdivided, firstly, into a forested subzone in the southern part and a shrub subzone (or krummholz) in the northern part and, secondly, into a maritime ecoclimatic area near Hudson Bay and a continental ecoclimatic area inland. The most snowy coniferous stands are located in the shrub subzone; snow density rises gradually from the taiga to the tundra. The highest values in snow properties are found in the maritime ecoclimatic area. These data suggest the following observations: (1) maximum snow depth measured in the northern part of the forest–tundra is explained by an increase of barren ground cover and by the presence of more open coniferous stands, which favor snow drifting and snow trapping; (2) the gradual increase in snow density is related to more rigorous climatic conditions; wind exposure is rather important since these sites are getting more open; and (3) the differences in snow conditions between the ecoclimatic areas show that the maritime environment is more windy; the presence of scattered and erected white spruce (Picea glauca (Moench) Voss) in various krummholz formations in that area favors more efficient snow traps than those of krummholz formations located in the continental area. The latter is dominated by prostrate and erect black spruce (Picea mariana (Mill.) BSP.) always densely agglomerated. The latitudinal pattern in snow conditions reflects the climatic conditions of the forest–tundra, and this determines the specific ecological distribution of coniferous stands.
The epidemiology of leaf spot disease in a native prairie. I. The progression of disease with time
Authors: Howard R. J. , Morrall R. A. A.
Published: September 2008

Leaf spot disease caused principally by Pyrenophora tritici-repentis was studied in 1969, 1970, and 1971 at Matador, Saskatchewan, in a native prairie dominated by Agropyron dasystachyum and A. smithii. The proportion of leaf area diseased (x), the lesion area per square metre of plot area, and the number of lesions per square metre of plot area were all used to measure disease on the total graminoids in the ecosystem. Disease progress curves for the first two variables differed considerably. The maximum x values in 1969, 1970, and 1971 were 0.034, 0.043, and 0.027 respectively. However the maximum lesion area per square metre of plot in 1970 was about twice that of the other 2 years. In 1970 there was less disease in an irrigated treatment and in a treatment in which the grass had been burned in late summer 1969, than in non-treated grassland. In 1970 and 1971 the distribution of individual leaf spots in 13 size classes varied at each sampling date, but most lesions were always less than 0.31 mm2. Overall, disease intensities were always low, despite sometimes apparently favorable environmental conditions. The results are discussed in relation to (inter alia) the study of plant disease epidemics in natural ecosystems and the variables generally used to measure diseases.
The distribution and fine structure of the epicuticular leaf wax of Pseudotsuga menziezii
Authors: Thair B. W. , Lister G. R.
Published: September 2008

Observations were made by scanning and transmission electron microscopy on the distribution and fine structure of epicuticular wax crystals on the hypostomatic needles of Douglas fir (Pseudotsuga menziezii (Mirb.) Franco.). The wax crystals were aggregated in tufts of variable area and density in discontinuous but uniform distribution along the adaxial surface, abaxial midrib, and stomatal regions. The stomatal region showed the greatest density of wax crystals, filling the stomatal antechambers formed by subsidiary cells. Wax crystals were present on the abaxial margins in a gradient of density from that of the abaxial stomatal region to that of the adaxial surface. The epicuticular wax crystals on Douglas-fir needles are of open tubular form exclusively, with a mean outer diameter of 136 ± 12 nm, wall thickness of about 35–40 nm, and average length of 2.3 μm. In view of the helical striae observed on the outer crystal surface, an interpretation of possible substructure is discussed.
Peripheral structures of plastids and ultrastructural localization of acid phosphatase and succinic dehydrogenase in a variegated Betula pubescens mutant
Authors: Valanne Niina
Published: September 2008

In white leaf tissue from a variegated Betula pubescens mutant, acid-phosphatase activity is seen only in the vacuoles and the cell wall and no precipitation is evident inside the mutant plastids. The electron-microscopic localization of succinic dehydrogenase reveals activity in the intracristal spaces of mitochondria and the envelopes of both mitochondria and plastids. Since precipitation is not apparent inside the protrusions of the plastids and only the membrane occasionally shows a typical mitochondrial reaction, evidence seems to be lacking which indicates that mitochondria originate from plastids. The mitochondrion-like particles budding from the mutant plastids are considered to be proplastids. Peripheral vesicular structures are also seen in the chloroplasts of green leaf tissue from plants growing at high light intensities.
The water relations of hemlock (Tsuga canadensis). V. The localization of resistances to bulk water flow
Authors: Tyree M. T. , Caldwell C. , Dainty J.
Published: September 2008

The pressure-bomb technique has been used to measure the kinetics of water exchange while a plant enclosed in a pressure bomb evolves from one equilibrium balance pressure to another. In earlier studies two observations were made. (1) The kinetics of water exchange appeared to be described by an exponential process in which three populations of cells exchange water with apoplast independently of each other. (2) The temperature dependence of the tempo of water exchange yielded an activation energy of 25.9 ± 0.6 × 103 J/mol, which is higher than the activation energy for laminar flow of water in pipes (= 17 × 103 J/mol). These results have been repeated and a more careful analysis has been conducted involving infiltration of air spaces in leaves with water and the selective removal of the leaves. It now appears that the xylem network up to (but not including) the leaves contributes about two thirds of the resistance to water flow in whole shoots 15 to 40 g in fresh weight. Presumably leaves near the cut basal end of the shoot experience a smaller xylem resistance than leaves near the apex. The kinetics of water exchange from water in the air spaces of infiltrated shoots indicates that there is a barrier at the air–water interface of leaves that equals the normal shoot resistance to bulk water flow. The activation energy for water flow through the xylem alone was measured to be about 17 × 103 J/mol. Although the leaves contribute a measurable amount to the overall resistance to water flow, the mathematical description of the system is much more complicated than previously supposed.
Further observations on the mechanisms involved in primary spore cleavage in Aphanomyces euteiche
Authors: Hoch H. C. , Mitchell J. E.
Published: September 2008

The delineation of primary asexual spores from hyphal protoplasm in Aphanomyces euteiches was studied by both light and electron microscopy. The observations indicate that the tonoplast of the central vacuole, present before induction of the sporulation process, was incorporated into the plasma membrane that ultimately surrounded the primary spores, and that cytoplasmic microtubules may be involved in condensation of the spore's cytoplasm. A diagrammatic interpretation of the cleavage process is presented.
Attraction et répulsion des bactéries par les spores de Cladosporium cladosporioïdes en cours de germination
Authors: Diem Hoang G.
Published: September 2008

Germinating spores of Cladosporium cladosporioïdes induce bacteria to respond in ways which are similar to positive and negative taxis. Attraction and repulsion of bacteria by the fungus appear to be dependent on the nature of the substrate. [Translated by the journal]
Accumulation of rare earths and circulation of cerium by mockernut hickory trees
Authors: Thomas William A.
Published: September 2008

Mockernut hickory (Carya tomentosa) trees accumulate the rare-earth elements in foliage in far greater concentrations than do other species on the same site (1350 ppm in ash, compared with less than 60 ppm by red maple, tulip tree, white oak, and black gum). Inoculation of hickory trees with,144Ce showed that this typical rare-earth element moves slowly through woody tissues, with only a small percentage of total-tree cerium lost annually by leaf abscission. Slow decomposition of hickory litter further limits losses of rare earths from the tree–soil system. These processes create centers of rare-earth concentration that perpetuate themselves, exemplifying the role of accumulator species in determining the distribution of elements within ecosystems.
Light and electron microscopy localization of chloride ions in cells of Salicornia pacifica var. utahensis
Authors: Hess W. M. , Hansen D. J. , Weber D. J.
Published: September 2008

Light and electron microscopy was used to determine the distribution of chloride ions in cells and tissues of Salicornia pacifica Standl, var. utahensis (Tidestrom) Munz. Chlorenchyma cells with chloroplasts around the periphery and sclereid-like cells with distinct wall thickenings which extended from the anastomosing vascular system to near the epidermis were present in the cortex. The vascular bundles or stelar strands were surrounded by several layers of large parenchyma cells. Tissues were treated with silver acetate for silver chloride precipitation. Silver chloride precipitation sites were present in all cell types. Precipitation sites were readily evident in the vacuoles but not in other organelles.
In vitro germination of Entomophthora aphidis resting spores
Authors: Tyrrell David , MacLeod Donald M.
Published: September 2008

On germination, resting spores of Entomophthora aphidis produce a septate sporogenous germ tube, which in turn gives rise to two or occasionally three germ conidia, one conidium being formed by the terminal cell and the others from cells lower down the tube. The resting spores possess sufficient endogenous nutrient reserves to complete the germination process.
A study of the flavonoids of certain species of Cassiope (Ericaceae)
Authors: Denford K. E. , Karas I.
Published: September 2008

A survey of the leaf flavonoids of the major taxa of Cassiope D. Don has been carried out resulting in the identification of eight simple glycosides: myricetin 3-O-glucoside, 3-O-rhamnoside, 3-O-arabinoside (two isomers), and 7-O-glucoside; quercetin 3-O-rhamnoside, 3-O-arabinoside, and 3-O-rhamno-glucoside. Two 5-methoxy derivatives of myricetin have also been identified. The implications of such findings from a phytogeographic and taxonomic standpoint have been commented upon.
Sageria, a new genus of Helotiales
Authors: Funk A.
Published: September 2008

Sageria tsugae gen. et sp. nov. (Helotiales) is described from western hemlock (Tsuga heterophylla (Raf.) Sarg.) in British Columbia, Canada. The imperfect state is Ascoconidium tsugae Funk.
Incorporation of 14CO2 in amides and amino acids in rusted bean leaves
Authors: Raggi Vittorio
Published: September 2008

Free amino acids were analyzed in healthy and rust-infected bean leaves incubated for 180–200 min in light, with 14CO2. In rusted leaves the radioactivity of the pool diminishes gradually to 42% in the flaking stage and the beginning of sporulation and then gradually increases in the following days to values of 197% after the secondary sporulation 11 days from infection. An increase in percentage of total labelling of aspartic acid, glutamic acid, and asparagine was noted, except just before sporulation, but above all, a marked and gradual increase in the labelling of glutamine was observed. This amide is probably assimilated to a greater degree by the fungus for the synthesis of its cell wall glucosamine. Diminution in the labelling of glycine and even more in the labelling of serine would instead be ascribed to the decrease in the photorespiratory activity.
Stimulation of transpiration by nitrogenous materials
Authors: Minshall Wm. Harold
Published: September 2008

After a temporary decrease in transpiration on the day of treatment, the addition of urea or of potassium nitrate to the soil of potted plants of tomato (Lycopersicon esculentum Mill) increased the rate of transpiration from 10 to 40%. This increase was proportional to the amount of nitrogen applied and lasted for several days. The temporary decrease on the day of addition was a salt effect similar to the depression caused by sodium chloride or mannitol. Unlike potassium nitrate, neither potassium phosphate nor sodium chloride increased transpiration, indicating that the stimulation was a nitrogen effect. The increase in transpiration is thought to be linked to an increased nitrogen metabolism in the plants.
Formation of sporangia by Phytophthora drechsleri in soil at high matric potentials
Authors: Duniway J. M.
Published: September 2008

The formation of sporangia by Phytophthora drechsleri was examined in soil at constant matric potentials (ψm) between 0 and −0.3 bar, corresponding to soil water contents between saturation and field capacity. At ψm = −0.3 bar, P. drechsleri required 1.5 days to form a significant number of sporangia in soil. After 3–11 days in soil, when maximum numbers of sporangia were found, all ψm values from −0.025 to −0.3 bar were optimum for the formation of sporangia in both sterilized and unsterilized soil. In contrast, few sporangia were formed in soil at ψm values of 0 and −0.01 bar. Mycelia on the soil surface at ψm = 0 formed many sporangia, indicating that aeration at a depth of 5 mm in saturated soil was inadequate for sporangia to form. Viable sporangia were recovered from soil as long as 35 days after mycelial disks were placed in soil. Evidence is presented for the release of zoospores by sporangia in soil at all ψm values tested.
The ecology of pigweeds (Amaranthus) in Ontario. I. Interspecific and intraspecific variation in seed germination among local collections of A. powellii and A. retroflexus
Authors: Frost Roger A. , Cavers Paul B.
Published: September 2008

In southwestern Ontario, Powell's pigweed (Amaranthus powellii S. Wats.) is represented by two morphologically distinct variants. The species is nearly as frequent as redroot pigweed (A. retroflexus L.) in cultivated fields and the two species have often been confused with each other.A germination test was performed with seeds of five local collections of A. retroflexus, two of one variant of A. powellii and four of the second variant of A. powellii. Very little variation in germination behavior was revealed between the collections of A. retroflexus, but great variability occurred between the collections of the latter species. Further germination tests under contrasting light regimes with seeds of two collections of each species affirmed these findings.Seeds of A. retroflexus stored from 5 to 20 weeks before testing yielded more than 75% germination in all tests except in continuous darkness at alternating temperatures (30–18 °C), when 56 to 63% germinated. The total percentage germination of seeds of A. powellii varied between 19% and 95% over the range of test regimes and collections examined. In one collection of A. powellii significantly more seeds germinated in alternating light and darkness than in continuous darkness while the reverse was true in another collection. Seeds from this latter collection developed secondary dormancy when put to germinate in alternating light and darkness.
Ultrastructural features of the haustorial apparatus of the white blister fungus Albugo candida
Authors: Coffey Michael D.
Published: September 2008

The small spherical haustorium of the white blister fungus is connected to the much larger haustorial mother cell by a slender cylindrical neck. The haustorium contains mitochondria with tubular cristae as well as ribosomes and occasional cisternae of rough endoplasmic reticulum. Nuclei and perinuclear dictyosomes are found in the mother cells but are absent from haustoria. No discontinuity is found in the fungal cell wall in the haustorial neck. Immediately adjacent to the fungal wall and extending through the penetration site to a point about midway along the neck is a dark-staining layer continuous with the host cell wall. A collar consisting of fibrillar material, also continuous with the host cell wall, is commonly found around the proximal portion of the neck external to this dark-staining layer. An electron-dense sheath surrounds the thin wall of the haustorial body but is absent from the neck region. A series of tubules is continuous with the invaginated host plasmalemma which surrounds the haustorial body. These tubules contain an electron-dense core similar in appearance to, and continuous with, the sheath matrix. No evidence was obtained for the involvement of host dictyosomes and their secretory vesicles in the formation of the haustorial sheath. A constant feature of the haustorial apparatus is the association of flattened cisternae of host endoplasmic reticulum with the distal portion of the haustorial neck. The significance of this finding is discussed in relation to the endomembrane concept.
Competitive relationships of some bog ericads for major insect pollinators
Authors: Reader R. J.
Published: September 2008

A study was conducted at two peatland sites in southern Ontario to test the hypothesis that flowering-time diversification among ericaceous plants has resulted from interspecific competition for pollinators. Exclusion of pollinators from plants indicated that insect visitation was important to the seed set of all species tested. The species composition of insects visiting five ericaceous species overlapped considerably, which suggested that interspecific competition could be responsible for observed differences in peak flowering times. While previous experimentation has demonstrated that seed set is influenced by intraspecific competition for pollinators, evidence of interspecific competition is lacking. The inconstancy of pollinators rather than their low numbers is proposed as an additional explanation of why the peak flowering times of ericaceous shrubs do not overlap.