bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of the pressure chamber technique for measurement of leaf water potential in cassava (Manihot species)
Authors: Ike I. F. , Thurtell G. W. , Stevenson K. R.
Published: May 2008

The pressure chamber technique was evaluated as a method for estimating leaf water potential in cassava (Manihot esculenta Crantz). Xylem pressure potentials (ψP) measured with the pressure chamber were compared with leaf water potential (ψL) obtained for the same leaf with the in situ dew-point hygrometer.In both cassava varieties studied, ψL and ψP were linearly related (r2 = 0.87 and 0.98 for CMC9 and CMC40 respectively). The length of petiole exposed outside the chamber affects the relation between ψL and ψP and should be kept at between 1 and 3 cm for better agreement. In CMC40, ψP was consistently lower (drier) than ψL by about 1.0 bar (1 bar = 100 kPa) in the entire range of water potential studied, but was not the case in CMC9. The reason for this difference is unclear but may be due to a filling of tissues other than xylem tissues (Boyer 1967) during the measurement of ψP in CMC40. Average xylem osmotic potentials (ψS) were low (−1.0 ± 0.2 bars and −1.0 ± 0.4 bars for CMC9 and CMC40 respectively). It is, therefore, unnecessary to correct for ψS when using the pressure chamber to estimate leaf water potentials in cassava.
Late Quaternary pollen record from the Sanpoil River Valley, Washington
Authors: Mack Richard N. , Rutter N. W. , Valastro S.
Published: May 2008

An 8.5-m core from Simpsons Flats, Ferry Co., Washington, includes at least four pollen zones spanning the last 10 000 years. With retreat of the Sanpoil lobe of Pinedale continental ice in the river valley, vegetation with low pollen influx (zone I) and dominated by Artemisia, Gramineae, and Pinus became prominent. Owing to the narrowness of the valley near Simpsons Flats, it is not clear whether pines were in the valley or on the adjacent upland sites.Mazama ash (ca. 6700 years before present (B.P.)) probably lies disconformably atop zone I and is included within a long-term warmer drier period (zone II) characterized by diploxylon pine pollen. Evidence for an effect of the Mazama ashfall on the vegetation is inconclusive. Zone III (4050–2700 years B.P.) marks a comparatively short period in which climatic conditions were slightly moister (although not necessarily cooler) than today, and the vegetation was dominated by diploxylon pine but with increased influx and frequency of Picea, Abies, and some haploxylon pine. The modern vegetation in the vicinity of the mire is dominated by Pinus ponderosa and Gramineae (including Festuca idahoensis) and seems to have emerged within the last 2700 years (zone IV).
Mycorrhizal fungi associated with Festuca in the western United States and Canada
Authors: Molina Randolph J. , Trappe James M. , Strickler Gerald S.
Published: May 2008

Vesicular–arbuscular mycorrhizal infection and associated mycorrhizal fungi were examined for Festuca viridula, Festuca idahoensis, Festuca scabrella, Festuca thurberi, Festuca ovina, and Festuca arizonica occurring in Festuca-dominated grasslands in the western United States and Canada. All plants were mycorrhizal. Nearly all had mycorrhizal infection in 75% or more of their fine root length. Although levels of infection were consistently high, spore numbers were generally low. No differences in the degree of infection between Festuca species or habitats were observed.Eleven mycorrhizal fungi were identified and ranked by decreasing frequency as follows: Glomus fasciculatus, Glomus tenuis, Gigaspora calospora, Acaulospora laevis, Glomus macrocarpus var. macrocarpus, Glomus microcarpus, Acaulospora scrobiculata, Glomus mosseae, Glomus macrocarpus var. geosporus, Sclerocystis rubiformis, and an unidentified Acaulospora species. It was common to find two or more species infecting an individual plant. The mean number of fungal associates per community site ranged from 2.7 species for F. idahoensis to 5.0 species for F. arizonica. We found no evidence for specificity of any of the mycorrhizal fungi for any particular Festuca host.
Comparison of soil microfungal populations in disturbed and undisturbed forests in northern Wisconsin
Authors: Wicklow Donald T. , Whittingham W. F.
Published: May 2008

Soil dilution plates were used to isolate populations of microfungi associated with the different soil horizons of five secondary successional forests, which arose after fire or clear-cutting, and three virginal (reference) stands. Ordinations of the populations within each horizon, based on similarities in the species composition of the microfungal communities, revealed the disturbed stands differed from their respective reference stands, although there was no consistent displacement of the stands in the ordinations. Most of the differences entailed alterations in frequency and (or) density, although a few species were predominant in one forest type but not in its counterpart. The most recently disturbed areas exhibited the greatest displacements from their reference stands. The ordinations suggested there is a sequential recovery of the mycoflora in the disturbed stands on loamy sand soils which would eventually result in a population similar to that in the reference stand.
Heterostyly in a tropical weed: the reproductive biology of the Turnera ulmifolia complex (Turneraceae)
Authors: Barrett S. C. H.
Published: May 2008

Turnera ulmifolia (Turneraceae) is a polymorphic complex native to the New World tropics which is composed of heterostylous and homostylous forms. The distylous varieties elegans, intermedia, and surinamensis exhibit the typical expression of heterostyly. Floral dimorphism is associated with a strong self-incompatibility system and size dimorphism of pollen. Approximately equal representation of floral morphs occurred in 24 out of 28 New World populations surveyed. In 9 out of 10 populations studied, there were no significant differences between the seed fecundity of floral forms. Populations of the homostylous variety angustifolia are self-compatible and produce monomorphic pollen.In contrast to the majority of heterostylous species, some varieties of T. ulmifolia are ruderal weeds. Varieties angustifolia, elegans, and intermedia are also used as garden ornamentals, and man has played a major role in the expansion of their ranges. Weediness in T. ulmifolia is not associated with features commonly found in other weed species, such as self-compatibility, vigorous clonal propagation, and long-distance seed dispersal. However, the continuous year-round flowering of T. ulmifolia plants gives populations a high reproductive capacity. Seed dispersal is by ants which transport seeds relatively short distances. Local seed dispersal favors the establishment of dense populations and increases the likelihood of seed set. Hence the dispersal system of T. ulmifolia appears to be coadapted with the population requirements of the breeding system.
A dwarf coastal variety of maidenhair fern, Adiantum pedatum
Authors: Wagner Jr. W. H. , Boydston Kathryn E.
Published: May 2008

A new variety of the maidenhair fern, Adiantum pedatum var. subpumilum W. H. Wagner, is described. Known previously only as a garden plant, a natural population has been discovered on coastal rock cliffs on the Brooks Peninsula of NW Vancouver Island. The basic frond structure is like the typical variety, but the plant is extremely dwarfed, the fronds are only 6–12 cm tall with imbricated pinnules. The venation pattern is much simplified. Horticultural plants of var. subpumilum yield n = 29 pairs of chromosomes, like the typical variety. The diminutive stature of var. subpumilum is genetically fixed.
Comparative gas exchange physiology in the Daucus carota complex
Authors: Small Ernest , Desjardins R. L.
Published: May 2008

Rates of net photosynthesis, transpiration, and dark respiration of seven populations representing the diversity of the Daucus carota complex were measured. The two taxonomic groups of this complex proved physiologically distinguishable, with subspecies aggregate gingidium possessing lower capacities for photosynthesis and transpiration and a lower frequency of stomata than subspecies aggregate carota. In comparison with wild populations of the complex, cultivars manifested greater efficiency of photosynthesis with respect to water use, possibly the result of an increased demand for photosynthate in domesticated populations. The highest rate of photosynthesis was exhibited by a vigorous, primitive, Asian cultivar, which also possessed the highest stomatal frequency.
Seasonal changes in the major ash constituents of leaves and some woody components of trembling aspen and red osier dogwood
Authors: James T. D. W. , Smith D. W.
Published: May 2008

Concentrations of N, P, K, Ca, and Mg were determined at monthly intervals over the growing season in the leaves, twig bark, and twig wood of Populus tremuloides Michx. (trembling aspen) and in the leaves and stems of Cornus stolonifera Michx. (red osier dogwood) in southern Ontario. Concentrations of N, P, and K in the leaves of both species decreased from May to August. Levels of Mg and Ca increased. Nutrient changes in aspen twigs during the May to September period, with the exception of magnesium, followed the reverse direction to those in the leaves. Seasonal changes in all of the nutrients in twigs were very small. Seasonal nutrient variability in red osier stems was also slight, but concentrations of Mg and Ca showed a July peak, and K showed a peak in June. N and P declined from early spring to midsummer but by September in dogwood the levels had returned to the April values.
Seasonal changes in the caloric value of the leaves and twigs of Populus tremuloides
Authors: James T. D. W. , Smith D. W.
Published: May 2008

Seasonally averaged caloric values (kilocalories per gram dry weight) of Populus tremuloides Michx. (trembling aspen) in southern Ontario were 5.17 for leaves, 5.04 for twig bark, and 4.55 for twig wood. The marked difference between leaves and twig wood reflects the differing composition of these tissues. The caloric levels of all the aspen components were highest in May. Levels decreased markedly from May to June, increased to a second peak in August, and then declined again between August and September. The caloric value of twig bark and wood also showed a decline from September to November. Seasonal fluctuations in caloric value of trembling aspen leaves and twigs were large compared with changes reported for other forest tree species and it is suggested that aspen is relatively sensitive to environmental effects.
Filobasidiella arachnophila sp. nov.
Authors: Malloch D. , Kane J. , Lahaie D. G.
Published: May 2008

A new species of Filobasidiella Kwon-Chung is described and illustrated. This species, F. arachnophila, was isolated from a dead spider and appears to be nonpathogenic. It differs from previously described species in being homothallic and in lacking a yeast-like phase of growth.
Assessment of receptivity and urediospore production as components of wheat stem rust resistance
Authors: Mortensen K. , Green G. J.
Published: May 2008

In a field experiment the wheat cultivars Glenwari, Exchange, Thatcher, Warigo, Idaed 59, and Hopps were assessed as having slow rusting abilities when artificially inoculated with a mixture of 22 physiologic races of stem rust. Resistance that resulted in slow rusting was demonstrated in growth cabinets with adult plants of these six cultivars after standardized inoculation with three stem rust races followed by uniform incubation and growth conditions. The investigation revealed that the following different kinds of resistance were involved: (1) 'specific' resistance effective against race C17 was observed in tests with seedlings and adult plants of Thatcher, Hopps, and Idaed 59; (2) low receptivity was observed in tests with adult plants of Glenwari, Warigo. Hopps, and Idaed 59; and (3) low urediospore production per pustule was evident in tests of the cultivar Exchange. The resistance of the cultivar Thatcher appeared complex, involving slow and nonuniform pustule development.Resistance expressed as low receptivity and low urediospore productivity varied in effectiveness against different physiologic races. In many instances significant interactions occurred between cultivars and races. Temperature changes appeared to affect the expression of resistance in many race–cultivar combinations. Thus, this type of resistance does not fit the definition of horizontal resistance proposed by van der Plank. Nevertheless, field investigations indicate that the resistance is effective against many rust races and could be potentially valuable in breeding programs.
The lipase activity of Talaromyces emersonii
Authors: Oso B. A.
Published: May 2008

Studies were carried out on the ability of Talaromyces emersonii Stolk to produce extracellular lipase in stationary liquid medium under various conditions. The best temperatures for lipase synthesis and activity were 40–45 °C, and at all the temperatures (37–55 °C) tested for lipase production, maximum enzyme was produced 8 days after incubation. Lipase synthesis was induced when various carbohydrates were used as carbon sources both in the presence and absence of yeast extract. The significance of lipase production in relation to the natural habitat is discussed.
Asci of the Pezizales. I. The apical apparatus of iodine-positive species
Authors: Samuelson Don A.
Published: May 2008

Morphological, developmental, and cytochemical studies on the apical apparatuses of five species, i.e., Peziza succosa, Ascobolus crenulatus, Saccobolus depauperatus, Thecotheus pelletieri, and Iodophanus granulipolaris, were performed with light and electron microscopy. Asci of all species, except A. crenulatus, stain blue in Melzer's reagent. The site of the iodine-positive reaction is believed to be an exogenous mucilaginous coat in P. succosa, S. depauperatus, and T. pelletieri. In I. granulipolaris, the reaction site appears to be the ascal wall. The presence of an annular indentation was found in the ascal tips of all species except I. granulipolaris. A line of dehiscence was found in the lower region of the annular indentation in T. pelletieri and S. depauperatus. The development of the apical apparatuses of all species occurs during and after late ascosporogenesis. The apical apparatus of I. granulipolaris diverged significantly in morphology and cytochemistry from the other species.
Thylakoid development and chlorophyll distribution in water-stressed and hormone-treated wheat leaves
Authors: Duysen M. E. , Freeman T. P.
Published: May 2008

An osmotic stress imposed by polyethylene glycol reduced the number and length of stroma thylakoids, the total thylakoid length, and chlorophyll (Chl) accumulation in pigment–protein complex II during the greening of wheat, Triticum aestivum L. cv. Chris, chloroplasts. The combination treatment of benzyladenine and gibberellic acid applied with the imposed stress increased the number of thylakoids per granum, number and length of stroma thylakoids, total thylakoid length, and accumulation of Chl in pigment–protein complex II but reduced plastid number. Abscisic acid reduced the number and length of stroma thylakoids and the total thylakoid length of developing chloroplasts.
Hypoxylon conostomum: cytology of the ascus
Authors: Rogers Jack D.
Published: May 2008

The haploid chromosome number of Hypoxylon conostomum is seven. Ascosporesare uninucleate when formed, becoming binucleate after a mitosis. One of the two nuclei is cut off in a cellular appendage which degenerates before the ascospore becomes colored. These observations are discussed in relation to the taxonomic position of this fungus.
Local dispersal of Limnanthes nutlets: an experiment with artificial vernal pools
Authors: Jain S. K.
Published: May 2008

Local dispersal of nutlets in Limnanthes species was studied by seeding four taxa per pool in nine pools from among a total of 12 experimental vernal pools. Dispersal within a pool was measured by the relative frequency of migration from seeded area to the remainder of a pool and dispersal between pools was measured by the frequency of invasions by a taxon into three unseeded pools. These relative measures showed that Limnanthes alba had the highest dispersability; however, all Limnanthes taxa seemed to have a rather low dispersability. The observed patterns of distribution show that pools within a pasture have frequently only one of the Limnanthes taxa and often show a lack of sympatry. Low dispersability along with high persistence of local populations through seed carry-over and perhaps local habitat selection would account for the observed pattern of species distributions in vernal pools.
Growth during microsporogenesis in hexaploid triticale
Authors: White R. L. , Kaltsikes P. J.
Published: May 2008

During the 100-h period from quartet breakup until first pollen grain mitosis, mean cell, nuclear, and nucleolar volumes were calculated at 10-h intervals in hexaploid triticale (× Triticosecale Wittmack cv. Rosner). Changes in DNA content per microspore were also measured to determine the time of DNA synthesis. From 0 to 30 h (G1), (1) cell volume increased at a constant rate from 9400 to 48 297 μm3, (2) nuclear volume initially increased from 1674 to 3261 μm3 but then returned to 1568 μm3. and (3) nucleolar volume did not change. From 30 to 70 h (S), cellular volume increased to 79 090 μm3, nuclear volume did not change, and nucleolar volume initially increased twofold but then returned to the G1 value. From 70 to 100 h (G2), there was no change in cell volume, while nuclear and nucleolar volumes increased to 4365 and 344 μm3, respectively. Regression analysis throughout microsporogenesis indicated a constantly changing significant relationship between the volume of a cell and its nucleus and nucleolus. However, no significant regression coefficients were obtained during early prophase. These results are interpreted as indicating that critical cellular, nuclear, or nucleolar volumes are not necessary for the development of a cell through interphase.
Thin sectioning, freeze fracturing, energy dispersive x-ray analysis, and chemical analysis in the study of inclusions in seed protein bodies: almond, Brazil nut, and quandong
Authors: Lott John N. A. , Buttrose Mark S.
Published: May 2008

Protein bodies from almond (Prunus dulcis), Brazil nut (Bertholletia excelsa), and quandong (Santalum acuminatum) have been studied in thin sections of fixed and embedded tissue, in freeze-fracture replicas of unfixed tissue, by chemical analysis of tissue for P, K, Mg, and Ca, and by energy dispersive x-ray (EDX) analysis of both sections of glutaraldehyde-fixed tissue and freeze-dried tissue powders. The protein bodies in all three species contained globoid crystals, protein crystalloids, and proteinaceous matrix regions. Results of EDX analyses were consistent with globoid crystals being rich in phytin. Variation in both the structure and the elemental composition of globoids was common. In almond some globoids were lobed rather than spherical, and large globoid crystals often contained considerable calcium whereas small globoid crystals contained little if any calcium. The globoid crystals of Brazil nut often contained barium in addition to P, K, Ca, and Mg. Protein crystalloids of Brazil nut were compound crystals. Protein bodies of quandong seed, which is largely endosperm rather than embryo, were unexceptional.
Inclusions in seed protein bodies in members of the Compositae and Anacardiaceae: comparison with other dicotyledonous families
Authors: Buttrose Mark S. , Lott John N. A.
Published: May 2008

Thin sections, freeze-fracture replicas, energy dispersive x-ray (EDX) analyses, and chemical analyses of cotyledon tissue from seeds of sunflower (Helianthus annuus), golden everlasting daisy (Helichrysum bracteatum), cashew (Anacardium occidentale), and pistachio nut (Pistacia vera) showed that in all four species the protein bodies consisted of a proteinaceous matrix surrounding numerous globoid crystals. Some variation in globoid crystal size did occur, but they were generally small in relation to the size of the protein body. No protein crystalloids were found in the cotyledon protein bodies of these four species. EDX analysis results were consistent with the globoid crystals being phytin rich. Results of this study, combined with an evaluation of protein body structure in other dicot embryos that have been studied, support the theory that protein body structure is related to taxonomic grouping.
Calcium oxalate druse crystals and other inclusions in seed protein bodies: Eucalyptus and jojoba
Authors: Buttrose Mark S. , Lott John N. A.
Published: May 2008

Druse crystals of calcium oxalate are known to occur in some protein bodies of some plant seeds. This paper reports observations on crystals, and other contents, of protein bodies of Eucalyptus erythrocorys and Simmondsia chinensis (jojoba). Results are presented from thin section studies of glutaraldehyde–OsO4 fixed, dehydrated, and embedded tissue; freeze-fracture studies; energy dispersive x-ray (EDX) analysis studies of freeze-dried tissue powders (Eucalyptus only); and chemical analysis studies of P, Mg, K, and Ca content (Eucalyptus only). Many Eucalyptus protein bodies contained large druse crystals rich in Ca but devoid of P, K, and Mg, and an occasional protein body from jojoba contained some dispersed crystals. Eucalyptus seeds were exceptionally high in Ca content. EDX analysis results provide evidence favouring the phytin-rich nature of globoid crystals in the two species. Structural variation in the globoid crystals was great, especially in jojoba. Eucalyptus, whose protein bodies contained very large globoid crystals rich in P, Mg, and K, was found to have higher levels of these elements than most species investigated to date.
Histopathological and ultrastructural comparison of Stemphylium sarcinaeforme and S. botryosum on red clover foliage
Authors: Higgins Verna J. , Lazarovits G. L.
Published: May 2008

As part of a continuing study of non-host resistance, red clover leaves inoculated with the clover pathogen Stemphylium sarcinaeforme, or the closely related alfalfa pathogen S. botryosum, were examined by light and electron microscopy to compare the events occurring in the initial stages of infection. Stemphylium botryosum penetrated leaves primarily via the stomata with resultant death of the guard cells and with varying effects on adjacent epidermal cells. Appressoria were frequently formed, and although they rarely resulted in successful penetrations, the contacted epidermal cells were often markedly affected as judged by toluidine blue staining. Growth of hyphae was intercellular but very limited in its extent. At some infection sites, one to several mesophyll cells underwent extensive plasmolysis and cytoplasmic disruption. Less severely affected mesophyll cells contained large lipid bodies, abundant rough endoplasmic reticulum, and Golgi vesicles and had wall appositions at points of contact with necrotic cells or with hyphae. Stemphylium sarcinaeforme generally penetrated between or directly through the epidermal cells, causing death of the contacted cells. Hyphae grew intercellularly or intracellularly in the palisade tissue and hyphal elongation was considerably more rapid than that of S. botryosum. Palisade cells adjacent to, or containing, the hyphae underwent several different types of cytoplasmic deterioration. Mesophyll cells surrounding these areas showed the same features as comparable cells in tissue infected by S. botryosum. In tissue infected by either fungus, the exterior of host cell walls was coated with a layer of extracellular material.
Taxonomy and relationship within the genus Octospora
Authors: Khare K. B. , Tewari V. P.
Published: May 2008

The genera Byssonectria Karst. (= Inermisia Rifai) and Kotlabaea Svrček, segregates from Octospora Hedw. ex Gray, are reduced to subgenera in view of the presence of intermediate characters which overlap the generic limits. Revised descriptions of the genus Octospora along with the three subgenera are provided. A key for the identification of the subgenera as well as the species examined by the authors is given. Thirteen species from other genera have been transferred to Octospora.
La photorespiration se déroulant dans un air sans CO2 a-t-elle une fonction?
Authors: Cornic Gabriel
Published: May 2008

Long-term effects of a low O2 and CO2, atmosphere on photosynthesis were studied on Sinapis alba L. It was shown that this could induce strong and durable changes on the subsequent photosynthesis measured at different CO2 and O2 concentrations. Two mains effects were observed: (1) an inhibition of net assimilation measured at 21% or 0.1% O2; (2) a qualitative change of the Warburg effect. After the treatment, high CO2 concentrations did not reverse the inhibitory effect of O2 on photosynthesis.The effect of the low O2 and CO2 atmosphere, characterized by the inhibition of net assimilation, was analyzed by varying the following factors during plants treatment: light intensity, temperature, and CO2 and O2 concentrations. The inhibition was higher under high light intensity, increased with temperature, and was apparent within the following limits of CO2 and O2 concentration, respectively, 0 to 0.018% CO2 and 0.1 to 4% O2.The results are discussed to determine if they showed that an inhibition of photorespiration in a low CO2 atmosphere has a function in the photosynthetic apparatus.
Patterns of change in the late-Quaternary vegetation of the Western Interior of Canada
Authors: Ritchie J. C. , Yarranton G. A.
Published: May 2008

Principal components analysis (PCA) of pollen data from 14 sites reveals five types of sequence. All begin from an early spruce-dominated assemblage, now apparently extinct, with subsequent differentiation into patterns of forested and grassland vegetation. A comparison of the PCA ordinations of these subfossil zones with those of modern pollen samples illustrates the uniqueness of the early spruce zone and the similarities between subsequent zones and modern spectra. The technique demonstrates the time transgressive nature of the early spruce forest assemblage in this region.
The effect of 2,4-D and kinetin on the activity and isoenzyme pattern of various enzymes in cotyledon cell suspension cultures of bush bean (Phaseolus vulgaris cv. Contender)
Authors: Arnison Paul G. , Boll W. G.
Published: May 2008

Changes in the activity and isoenzyme patterns of acid phosphatase, leucine aminopeptidase, glutamate-oxaloacetate transaminase, esterase, and malate and glutamate dehydrogenases were studied in cotyledon cell suspension cultures of Phaseolus vulgaris grown in the presence and absence of the growth regulators 2,4-dichlorophenoxyacetic acid and kinetin. With all enzymes studied, the pattern of isoenzymes and total enzymatic activity changed with the different phases of the culture cycle. In particular, the patterns of esterase, malate dehydrogenase, and glutamate dehydrogenase changed markedly with the inoculation of cells into fresh medium.The differences in isoenzyme patterns of cells grown with and without regulators were predominantly quantitative. However, certain minor isoenzymes of acid phosphatase, glutamate-oxaloacetate transaminase, esterase, and malate dehydrogenase were only detected in cultures grown in the presence of the regulators, while one isoenzyme of leucine aminopeptidase and two of esterase were unique to cells cultured in the absence of regulators.Three cathodic isoenzymes of acid phosphatase were released from wall material by 1 M NaCl. Such isoenzymes were also detected in the medium and in cytoplasmic extracts. Increase in the wall isoenzymes following inoculation into fresh medium was correlated with a decrease in anodic, cytoplasmic acid phosphatase.
Dormancy studies in seed of Avena fatua. 8. Genetic diversity affecting response to temperature
Authors: Naylor J. M. , Fedec P.
Published: May 2008

Experiments are reported which demonstrate the interaction of temperature with genotype in controlling germination in wild oats. In some pure lines germination of newly matured seeds occurs at all temperatures in the range 4–32 °C. Other pure lines exhibit strong suppression of germination in the midportion of this temperature range. The possible adaptive significance of this dimorphism in nature is discussed.
Phytoalexin production by high- and low-coumarin cultivars of Melilotus alba and Melilotus officinalis
Authors: Ingham John L.
Published: May 2008

The isoflavonoid phytoalexin medicarpin has been found to accumulate in leaflets of high- and low-coumarin cultivars of Melilotus alba and Melilotus officinalis following inoculation with the fungus Helminthosporium carbonum. Little or no medicarpin was isolated from leaflets treated with deionised water. Medicarpin was also produced when leaflets were irradiated with short-wavelength ultraviolet light. Elimination of the high-coumarin character from sweet clover cultivars does not appear to affect phytoalexin production, and in consequence, low-coumarin varieties should not be more susceptible to fungal colonisation than their high-coumarin counterparts.
Studies on hyphal development and appressorium formation of Colletotrichum graminicola
Authors: Kozar F. , Netolitzky Hans J.
Published: May 2008

The fine structure of actively growing hyphae of Colletotrichum graminicola was investigated. The hyphae were found to secrete a mucilaginous sheath into which melanizing particles and fibrils were deposited. Classical ubiquitous mitochondria, multipored doublewalled nuclei, ribosomes, mesosome-like structures, lomosomes, vacuoles, and inclusions such as lipids, closely associated with vacuoles, especially noticeable during germination, as well as glycogen were present. During maturation, vacuoles appeared and enlarged. In addition, a few endoplasmic reticulum profiles were observed in actively growing hyphae. Mitochondrial profiles changed from spherical to elongate. A plasmalemma, perhaps double in nature, was present. Penetration of one hypha by another was also observed.The mature appressorium exhibited a thick three-layered cell wall. This thick wall appeared to play a part in poor fixation and embedding, resulting in a poor definition of such cellular organelles as ribosomes, nuclei, etc. Internally, appressoria, depending on the stage of development, exhibited many vacuoles and osmiophilic deposits indicative of lipid reserve material. A germ pore through which a germ tube and migrating organelles and cytoplasm emerged was also observed.
Gliocladium catenulatum: hyperparasite of Sclerotinia sclerotiorum and Fusarium species
Authors: Huang H. C.
Published: May 2008

Gliocladium catenulatum parasitizes Sclerotinia sclerotiorum and Fusarium spp. It kills the host by direct hyphal contact causing the affected cells to collapse or disintegrate. Pseudoappressoria are formed by the hyperparasite but hyphae derived from them do not penetrate the host cell walls. Vegetative hyphae of all species tested and macroconidia of Fusarium spp. are susceptible to this hyperparasite but chlamydospores of Fusarium equiseti are resistant.
Initiation of resistant responses in bean by mycelial wall fractions from three races of the bean pathogen Colletotrichum lindemuthianum
Authors: Anderson Anne
Published: May 2008

Phytoalexin production and browning were elicited in Dark Red Kidney bean cotyledons by application of mycelial walls isolated from three races of Colletotrichum lindemuthianum. Two races, α and δ, were avirulent on this bean cultivar and a third, β, was virulent. Heat treatment of aqueous suspensions of the α, (β, and δ mycelial walls released soluble polysaccharides that elicited browning and phytoalexin production on bean cotyledons. These polysaccharides were not adsorbed by anion or cation exchange resins and ranged in size up to at least a molecular weight of 106. The highest molecular weight fractions were predominantly glucans and showed elicitor activity on cotyledons with application of less than 10−6 g glucose equivalents. The soluble polysaccharide extracts also possessed minor amounts of sugars which differed among the α, β, and δ races.
Hydraulic architecture of some diffuse-porous trees
Authors: Zimmermann Martin H.
Published: May 2008

The rate of flow of a dilute KCl solution through sections of stem, branches, and twigs was measured and expressed in microlitres per hour, under conditions of gravity flow, per gram fresh weight of leaves supplied by that section of xylem. This is called leaf-specific conductivity (LSC). It is not uniform throughout the tree, LSC of the stem being higher than that of branches. Furthermore, vascular junctions, such as the path from stem to branch, represent hydraulic constrictions. Distribution of LSC in the tree is primarily based on varying vessel diameters. Vessel diameters increase from top to bottom in the tree stem. They are smaller in branches than in the main stem, and there is a distinct constriction of diameters at the base of each branch. Functionally this means that when transpiration begins the pressure has to drop more rapidly in the xylem of lower lateral leaves than in those at the top of the tree. It also means that under conditions of water stress peripheral parts of the tree are more vulnerable than the trunk.
Contributions to the floras of British Columbia and the Yukon Territory. I. Vascular plants
Authors: Douglas George W. , Ruyle-Douglas Gloria
Published: May 2008

Ten taxa new to British Columbia and eight new to the Yukon are reported. Five of the British Columbia taxa also represent first records for Canada. In addition, 36 other extremely rare British Columbia or Yukon taxa are also discussed.
Comparative roles of soil and air temperatures in the timing of spring bud flush in seedling Douglas-fir
Authors: Sorensen Frank C. , Campbell Robert K.
Published: May 2008

Outdoor cold frame tests in which air and soil temperatures were modified showed both to be involved in the timing of spring bud flush. The results indicated that warming the soil advanced the date of growth initiation and warming the air increased the rate of bud development once initiated. The latter had a 5.7:0.45 greater effect per degree celsius change in temperature.
Parasitic and nonparasitic pathogenesis of tomato plants by Pythium myriotylum
Authors: Csinos Alex , Hendrix James W.
Published: May 2008

Tomato plants grown in soil infested with Pythium myriotylum or in soil containing nonviable mycelium were severely stunted. Mycelium of P. myriotylum was produced on a glucose–glutamate–cholesterol medium, separated from the medium, lyophilized, and ground into a fine powder in a Waring blendor. Tomato plants transplanted into steam-pasteurized soil with the addition of 200 mg of the nonviable mycelium developed foliar necrosis and were severely stunted. Seedlings with roots immersed in an autoclaved aqueous suspension of the mycelium (100 μg/ml) developed laminar collapse and dehydration within 12 h and were killed within 24 h. Detached tomato leaves behaved similarly. On autoclaving, the toxin associated with the mycelium of P. myriotylum was relatively stable below pH 6 but labile at pH values above 6. Treated leaves lost more fresh weight at 35 °C than at 27 or 22 °C. Evidence for variability in toxin production within P. myriotylum was obtained. Toxin(s) in the mycelium of P. myriotylum may be involved in reduced growth and death of tomato plants. This is the first known report of toxin production by P. myriotylum.
A rapid quantitative method to measure growth of plant cell suspension cultures
Authors: Kubek D. J. , Shuler M. L.
Published: May 2008

A rapid and accurate method for the determination of cell mass of soybean (Glycine max) and Paul's Scarlet rose (Rosa sp.) cells is reported using sonication and optical density. Results may be obtained within 20 min and would be of particular use in providing cell mass (i.e., dry weight) information quickly.
Fungi of the Canadian boreal forest region: Catulus aquilonius gen. et sp.nov., a hyperparasite on Seuratia millardetii
Authors: Malloch D. , Rogerson C. T.
Published: May 2008

A new genus and species of ascomycetes, Catulus aquilonius, is described, illustrated, and tentatively assigned to the Mycosphaerellaceae. It grows as a parasite on stromata of Seuratia millardetii (Raciborski) Meeker and is characterized by two-celled, setulose ascospores.
Ultrastructure of a palmelloid-forming strain of Chlamydomonas eugametos
Authors: Nakamura Kazuo , Bray Douglas F. , Wagenaar Emile B.
Published: May 2008

A palmelloid-forming mutant of the unicellular green alga Chlamydomonas eugametos has been studied ultrastructurally. The repetition, within the palmelloid envelope, of four-celled groups surrounded by wall layers suggests that normal asexual cytokinesis occurs but successive cell generations are unable to separate. Individual palmelloid cells are smaller than wild-type cells and possess flagella which are short (1–2 μm) and occasionally bulbous at the tip but appear normal with regard to internal microtubular, transitional region, and basal body structure. The association of granules with the outer surface of the palmelloid envelope and the tendency of palmelloids to form large aggregates in culture indicate a change in the adhesive properties of the cell walls of this mutant. A comparison of the ultrastructure of mutant palmelloids with previously described chloroplatinic-acid-induced palmelloids shows that the two types differ in both flagellar development and in the extent of cell wall formation.
Caloscypha fulgens (Ascomycetidae, Pezizales): the perfect state of the conifer seed pathogen Geniculodendron pyriforme (Deuteromycotina, Hyphomycetes)
Authors: Paden J. W. , Sutherland Jack R. , Woods T. A. D.
Published: May 2008

Results of comparative cultural, conidiophore and conidia morphology, growth–temperature, and pathogenicity studies proved that Geniculodendron pyriforme Salt is the imperfect state of Caloscypha fulgens (Pers.) Boudier. The results are discussed in relation to the etiology and ecology of the disease of conifer seeds caused by the fungus.
An energy dispersive x-ray analysis study of elemental loss from globoid crystals in protein bodies as a result of osmium tetroxide fixation
Authors: Lott J. N. A. , Greenwood J. S. , Vollmer C. M.
Published: May 2008

This study was undertaken to discover what elemental losses, if any, were occurring from globoid crystals in seed protein bodies during glutaraldehyde – osmium tetroxide fixation. Unfixed cotyledon and radicle tissue of Cucurbita maxima seed, or tissue after glutaral–dehyde–OsO4 treatment, was quick frozen in liquid N2, ground with a cold mortar and pestle, and low-temperature freeze-dried. Globoid crystals in the freeze-dried powder were subjected to energy dispersive x-ray (EDX) analysis. OsO4 fixation resulted in a major loss of P, Mg, and K from cotyledon globoid crystals and a major loss of P, Mg, K, and Ca from radicle globoid crystals. Despite the loss of elements, the OsO4-fixed globoid crystals were still electron dense. When globoid crystals from glutaraldehyde-fixed, dehydrated, and embedded cotyledon tissue were compared with globoid crystals from glutaraldehyde–OsO4-fixed, dehydrated, and embedded tissue, some extraction was found. The degree of extraction varied from complete loss of P, K, and Mg to loss of K only.Effects of glutaraldehyde–OsO4 fixation upon elemental composition of globoid crystals in several other species was also determined. Brazil nut (Bertholletia excelsa) radicle tissue or cotyledon tissue from walnut (Juglans regia), hazelnut (Corylus avellana), sunflower (Helianthus annuus), golden everlasting daisy (Helichrysum bracteatum), cashew (Anacardium occidentale), pistachio (Pistacia vera), and the Western Australian red-capped gum (Eucalyptus erythrocorys) were fixed either in glutaraldehyde or in glutaraldehyde–OsO4. In these species, EDX analysis of globoid crystal sections showed that OsO4 fixation results in major loss of Mg, K, and Ca. Generally, phosphorus levels were reduced from control values as well. When carrying out EDX analysis studies of globoid crystals, we recommend (1) avoiding any use of OsO4, (2) keeping all fixation, washing, and dehydration times as short as possible, and (3) checking all observations with freeze-dried powders.
Organogenesis of the male inflorescence and flowers of Myrica esculenta
Authors: Macdonald Alastair D.
Published: May 2008

Organogenesis of the male inflorescence and flowers of Myrica esculenta is described. The inflorescence is a panicle of spikes. The myricaceous flower consists of up to five stamens and two transversal bracts. The organography and organogenesis of the flowers of the distal region of the inflorescence are similar to the organography and organogenesis of the flowers of the secondary inflorescence axes in the intermediate region of the inflorescence. The presence of a transversal pair of bracts on the floral axis is variable. Only in monostaminate flowers does a stamen terminate an axis. This is a function of the monostaminate flower being positioned at the extreme distal region of the primary inflorescence or secondary inflorescence axis. Five-, four-, three-, and two-stamened flowers occur as an acropetal reduction series along the primary inflorescence or secondary inflorescence axis. Whether or not floral bracts are present, the stamens arise simultaneously in a whorl on the flank of a flattened floral apex. The stamens do not form in the axils of the floral bracts. The pattern of male flower development is the same in all other species examined. It is concluded that this pattern of flower development illustrates a conservative sequence of ontogenetic events within the family. This is of taxonomic and phylogenetic significance.
Seasonal dynamics of epiphytic algal growth in a marsh pond: composition, metabolism, and nutrient availability
Authors: Hooper-Reid Nina M. , Robinson G. G. C.
Published: May 2008

Seasonal growth and succession of epiphytic algae on artificial substrates in a marsh pond were related to nutrient levels (N, P, and Si) and to various physiological indicators of nutrient availability, including chlorophyll content, protein to carbohydrate and lipid ratio, Si debt, storage phosphate levels, alkaline phosphatase activity, and nitrogenase activity. Low standing crops in June and early July coincided with indications of deficiency in terms of chlorophyll a content and protein to carbohydrate and lipid ratios at chosen Scirpus and Potamogeton sites. Low available N may have been limiting growth. In July and August, when available N, P, and Si were low, there was evidence of Si limitation of diatom growth at both sites. Growth of heterocystous, N2-fixing. blue-green algae and high alkaline phosphatase activity occurred in July at the Potanwgeton site. Increased standing crop of epiphytic algae in September and October at the Scirpus site coincided with higher nutrient levels and an absence of deficiency symptoms. A delay in the standing crop increase at the Potamogeton site correlated with low nutrient levels and various physiological deficiency symptoms.
Mycoparasitism by Piptocephalis unispora (Mucorales): host range and reaction with Phascolomyces articulosus
Authors: Jeffries P. , Young T.W.K.
Published: May 2008

Using light and electron microscopy, mycoparasitism by Piptocephalis unispora was investigated. Parasitism by P. unispora is restricted to certain members of the Mucorales. Piptocephalis unispora is also shown to infect germinating spores and hyphae of the potential thamnidiaceous host, Phascolomyces articulosus. Appressoria, penetration pegs, and haustoria are formed during the infection process but further development of the mycoparasite ceases. Reaction papillae and material present at infection sites and around degenerate haustoria are associated with the mechanism of resistance. The process of infection is compared with previous studies of the infection of Cokeromyces recurvatus (Thamnidiaceae) by Piptocephalis unispora.
Root growth in a polar semidesert environment
Authors: Bell Katherine L. , Bliss L. C.
Published: May 2008

Within the northwestern islands of the High Arctic, the vegetation and flora of King Christian Island are very representative. Five plant communities were recognized in a moisture gradient from a moss–rush moist meadow with 22 species of vascular plants and 13% cover (total plant cover 93%) to lichen barrens on low ridges with 8 species of vascular plants and 3% cover (total plant cover 24%). Root systems of 30 of the 34 known vascular plant species were examined. Root:shoot ratios (alive) are generally 0.2 to 0.7. Roots are estimated to live 1.5 years in Phippsia algida, 3.4–3.7 years in Alopecurus alpinus and Puccinellia vaginata, and 7–13 years in Luzula nivalis, L. confuse), and Cerastium arcticum. Optimal root growth occurs at 12 to 20 °C but cold field soils (1 to 3 °C) reduce these rates by 90%. Root growth was also reduced by low soil water potentials (< − 14 bars (1 bar = 100 kPa)), conditions seldom encountered in these sites. Limited root growth due to cold soils is combined with the adaptive advantages of small roots to produce small plants and sparse cover in these polar semidesert lands.
The life history and phenology of Callithamnion corymbosum (Rhodophyta: Ceramiaceae) in Newfoundland
Authors: Whittick Alan
Published: May 2008

Callithamnion corymbosum (Sm.) Lyngb, reaches its known northern limits in the western Atlantic on the south and southwest coast of insular Newfoundland where it occurs only as tetraspore-bearing plants which reproduce by vegetative fragmentation. It is abundant in the immediate subtidal in late summer and fall but is not an obvious component of the algal flora in the winter and spring when it occurs principally as detrital fragments. Tetrasporangia occur in the fall and their production in culture is temperature dependent. Discharged tetraspores have only limited viability in culture and their behaviour in nature is unknown.
Cytological studies of early stages of powdery mildew in barley and wheat. V. Effects of calcium on the infection of coleoptiles of barley by Erysiphe graminis hordei
Authors: Takamatsu Susumu , Ishizaki Hiroshi , Kunoh Hitoshi
Published: May 2008

Some effects of calcium salts on the infection process of Erysiphe graminis hordei in coleoptiles of barley were investigated. Calcium chloride enhanced the incidence of haustoria but depressed that of papillae. Calcium bromide and calcium nitrate likewise enhanced the incidence of haustoria. Calcium chloride treatment at varied times and with varied durations during incubation after inoculation showed that events occurring in coleoptiles between 9 and 13 h after inoculation were most affected by the treatment. This period included the times that appressoria matured, cytoplasm aggregated, papillae were produced, and haustoria were formed, and the effect of calcium might be associated with one or more of these events.