bluuebunny/crossref_metadata_2025 huggingface dataset:
Control of rapid stipe elongation by the lamellae in fruit bodies of Flammulina velutipes
Authors: Gruen Hans E.
Published: November 2007

Flammulina velutipes fruit bodies only grew normally if the pileus remained on the stipe until the end of rapid elongation when about 80% of the final length had been reached. During the same period lamellae alone increased stipe growth significantly compared with total decapitation. The stipes attained three-quarters of the length of intact fruit bodies with only about one-third of all lamellae. Near the end of the normal growth period, the stipe became independent of the pileus and lamellae. Small amounts of lamellae excised during rapid elongation produced diffusate in dilute potato glucose agar which promoted growth of decapitated stipes of the same age. The activity could be detected when fruit bodies had completed two-thirds of their normal growth but was much less than at the onset of rapid elongation. Tests of diffusates from young and old lamellae on stipes of different ages showed that the declining influence of lamellae in aging fruit bodies is associated both with decreasing production of the growth-promoting factor and decreasing response of stipes to an external supply of active diffusate. Neither pilear context nor any part of young or old stipes released growth-promoting diffusate.
The rare planktonic diatom Eunotia zasuminensis in Canada
Authors: Nicholls Kenneth H. , Carney Elaine C.
Published: November 2007

The planktonic diatom Eunotia zasuminensis (Cab.) Körner is reported from eight locations in Ontario, Canada. It is previously known from only four other localities in Europe and Africa and from two rivers in the U.S.A. The taxonomy of E. zasuminensis is discussed relative to similar species. Observations on the rudimentary raphe in this species emphasize its proper taxonomic position within the Eunotiales. The distribution of E. zasuminensis seems to be controlled by its apparent preference for slightly acidic or dystrophic waters.
Néoformation de racines, de bourgeons végétatifs et de boutons floraux sur des fragments de hampe florale de Nicotiana tabacum cultivar Basma S.31 cultivés in vitro
Authors: Ebrahimzadeh Hassan , Tarighi Ghollam-Hassan
Published: November 2007

The necessary conditions for the expression of the potentiality of neoformation of roots, vegetative buds, and flowers have been determined for the segments of flower stalk of a new cultivar of Nicotiana tabacum: cv. Basma S.31. The origin of these neoformated organs has also been demonstrated.
Acid phosphatase activity of six ectomycorrhizal fungi
Authors: Ho Iwan , Zak Bratislav
Published: November 2007

Six ectomycorrhizal fungi commonly associated with Douglas-fir were tested in vitro for acid phosphatase activity by measuring the amount of p-nitrophenyl phosphate converted to p-nitrophenol and by examining their production of isoenzymes detectable by starch gel electrophoresis. Both test methods showed acid phosphatase activity to be highest in Hebeloma crustuliniforme, followed by progressively lower activity in Laccaria laccata, Amanita muscaria, and Thelephora terrestris. Rhizopogon vinicolor and Piloderma bicolor showed low activity. We discuss the significance of these fungi in the utilization of complex phosphates by tree roots.
Isolation of the virus inhibitor from the root extract of Boerhaavia diffusa inducing systemic resistance in plants
Authors: Verma H. N. , Awasthi L. P. , Saxena K. C.
Published: November 2007

An antiviral agent, active against spherical and tubular viruses in hypersensitive and systemic hosts, has been isolated from the roots of Boerhaavia diffusa. Partial purification of inhibitor by organic solvents, Sephadex gel, and protein precipitants has been achieved. Preliminary analysis indicates that the inhibitor may be a glycoprotein with a molecular weight of 16 000–20 000 daltons.
On sowing wild oats
Authors: Stinson R. H. , Peterson R. L.
Published: November 2007

The awn of the wild oat (Avenafatua L.) twists into a helix on drying and untwists when wetthereby burrowing the seed into the soil. It is suggested that the unusual thick-walled outer eel Is ofthe awn increase in length upon drying. Since they remain attached to inner cells which undergono significant change in length, the awn is twisted into a helix to accommodate the longer outercells.
A method for the extraction of chlorophyll from leaf tissue without maceration
Authors: Hiscox J. D. , Israelstam G. F.
Published: November 2007

A simple, rapid method requiring few manipulations for the extraction of chlorophylls from fragmented leaf tissue of angiosperms and gymnosperms is compared with the widely used acetone method. Unlike the acetone method where grinding and subsequent centrifugation are essential, this method makes use of incubation at 65 °C of leaf tissue immersed in dimethyl sulphoxide. The new method was found to be as efficient as acetone for chlorophyll extraction and superior in terms of chlorophyll stability.
Microsurgical isolation of intact plant cell wall appositions for microanalyses
Authors: Kunoh Hitoshi , Aist James R. , Israel Herbert W.
Published: November 2007

Little is known about the chemical components of the plant cell wall apposition as they relate to its structure and function. The small sizes (5–15 μm diameter) of the appositions, their low frequencies in the cells, and their intimate connections to the cell wall have almost precluded meaningful cytochemical and (or) biochemical analyses. With the development of analytical techniques using the electron microprobe it is now feasible to discover the elemental composition of minute cellular structures, such as the wall apposition, but problems in specimen preparation remain. As a necessary and critical first step in microprobe analysis we have found it best to microsurgically remove fresh wall appositions from their mother cells and then admit them directly into the scanning electron microscope (SEM) after air drying and gold coating. This paper describes the requisite technologies of specimen preparation, microtool fabrication, specimen selection and isolation which are involved. The technique described could find ready application in the microanalyses of many other subcellular structures.
Nematophagous fungi: a new Arthrobotrys with nonseptate conidia
Authors: Barron G. L.
Published: November 2007

Arthrobotrys botryospora is described as new. Conidia are produced in successive clusters on a sympodially elongating main axis. Conidia are mostly nonseptate. Most nematodes are captured by adhesive nets but smaller nematodes are frequently captured by adhesion directly to the vegetative hyphae.
Fire recurrence in the subarctic and its implications for vegetation composition
Authors: Johnson E. A.
Published: November 2007

The Weibull distribution is shown to fit well with empirical data of fire intervals for a population of sites. The distribution demonstrates that the recurrence of fire in the subarctic forests of the Northwest Territories, Canada, is predictable. The three parameters of the distribution describe in ecological terms the lag before reburning can occur, the expected recurrence time of fire, and the shape of the variation around the expected recurrence. The parameters behave consistently with logically independent empirical evidence related to the regional and local climate and topography. The relationship of the distribution's hazard of burning function to vegetation composition and r–K selection is discussed.
Delay of hypersensitive necrosis by thermal treatment and fungal development in powdery-mildewed barley leaves
Authors: Toyoda Hideyoshi , Yano Tetsuo , Shishiyama Jiko
Published: November 2007

Before hypersensitive necrosis is observed in incompatible barley leaves inoculated with Erysiphe graminis hordei, the appearance of fluorescent epidermal or mesophyll cells is successfully detected by the fluorescent microscope. As this hypersensitive necrosis was considerably delayed by higher temperature treatment (25 °C), the effect of temperature on the appearance of fluorescent or browning cells and the fungal development was examined in powdery-mildewed barley leaves. Fluorescent epidermal cells were induced by both treatments of 20 and 25 °C after inoculation, whereas the appearance of fluorescent mesophyll cells was prominently delayed and the conversion of fluorescent to browning mesophyll cells was enhanced by the higher temperature treatment. On the other hand, fungal development was conspicuously promoted in the leaves grown at 25 °C. These results suggest that mesophyll fluorescing, rather than epidermal fluorescence, is a major factor restricting fungal development and that the promotive fungal development by higher temperature treatment is dependent upon both the delayed production of a fluorescent compound and the higher case of conversion of this compound into browning material which may be inactive to the fungus.
Organogenesis in Triglochin striata
Authors: Lieu S. M.
Published: November 2007

The blanching pattern of Triglochin striata is simple and is similar to that of the Alismataceae with upright vegetative axes. The inflorescence is formed from the leaf-opposed product of apical bifurcation. There is, however, no morphologically distinct prophyll on the leaf-subtended continuation shoot. Vegetative reproduction is by sympodial stolons developing from irregularly distributed axillary buds.Floral development consists of the sequential initiation of alternating, trimerous whorls of floral appendages in acropetal succession: two whorls of tepals, two of stamens, and two of carpels (of which the first is abortive) in the typical monocotyledonous pattern. Differential timing and rates of growth of the inner tepals and outer stamens result in the former appearing to be located internal to the latter in the mature flower. Suppression of all but the lowermost median stamen as staminodes and extensive development of the lowermost median tepal, together resulting in zygomorphy of the flower, occurs frequently. The common base of the stamen and its opposing tepal is a result of subsequent intercalary upgrowth. The evidence does not support the interpretation of the flower of Triglochin as a reduced lateral branch of the inflorescence.
Chemistry of root exudates and rhizosphere soils of prairie plants
Authors: Bokhari U. G. , Coleman D. C. , Rubink Amy
Published: November 2007

Root exudates may have important effects on microbial growth and nutrient cycling in many ecosystems. We examined exudation patterns of two dominant plants in the shortgrass prairie.Root exudates of mature blue grama plants contained greater amounts of carbohydrates than younger plants, whereas the latter exuded slightly more amino N than the older plants. Axenic seedlings exuded larger amounts of sugars than normal seedlings; however, there was no difference in the amounts of amino N exuded. Among the amino acids exuded by axenic seedlings the levels of proline, methionine, and glutamic acids were higher than those of the other amino acids. The rhizosphere soil of both blue grama and fringed sagewort had more soluble sugars than the nonrhizosphere soil while the latter had more nonsoluble sugars. Both soluble and nonsoluble amino N were in greater concentrations in the nonrhizosphere soil of blue grama and fringed sagewort than in the rhizosphere soil of the same species. Rhizosphere soil of the above two species contained more polyphenols than the nonrhizosphere soil. Trace amounts of terpenes were found only in the soil associated with fringed sagewort.
Mecoprop as a growth factor in wheat and rye tissue cultures
Authors: Jiménez Estela Sánchez de , Murillo Ezequiel
Published: November 2007

Wheat and rye calli were induced on Murashige–Skoog medium by the addition of 2, 4-D[(2,4-dichlorophenoxy)acetic acid]. The effect of Mecoprop [2(4-chloro-2-methyl)phenoxy propionic acid], an analogue of this auxin, was also tested and the rates of callus growth were compared with the ones obtained with 2, 4-D. On Murashige–Skoog medium, Mecoprop induced and supported callus growth of the various cereals tested more efficiently than did 2, 4-D. This effect was more pronounced on wheat callus. When both auxins were present in the culture medium, the enhancing effect of Mecoprop was slightly higher. The specific affinity of both auxins for wheat chromatin was measured. The results indicated that both substances, 2, 4-D and Mecoprop, selectively dissolve wheat chromatin. However, lower concentrations of Mecoprop than of 2, 4-D are required to dissolve the same amount of chromatin. It is concluded that in cereal cell cultures, Mecoprop is a more efficient growth factor than 2, 4-D.
Foliar borne stems in Anachoropteris gillotii from the lower Westphalian of Belgium
Authors: Holmes John C.
Published: November 2007

Two new specimens of Anachoropteris from Belgian coal balls from the Bouxharmont coal seam are described. Anatomically the specimens are characterized by very slight abaxial curvature of a uniformly thick, foliar vascular strand corresponding to the species A. gillotii Corsin, and morphologically, by a type of trifurcation of a foliar member which gives rise to two lateral foliar organs and a median, slightly adaxial cauline strand which shows the initiation of a petiole trace. The foliar members bear secondary pinna traces which immediately divide to give basiscopic tertiary traces. Metaxylem tracheidal pitting is simple scalariform in the stem and scalariform bordered in the leaves. One foliar specimen clearly supports Corsin's idea that in this genus there are two persistent adaxial protoxylem poles which divide alternately to supply pinna traces.
Plasmolysis of rusted flax: a fine-structural study of the host–pathogen interface
Authors: Allen Frances H. E. , Coffey Michael D. , Heath Michèle C.
Published: November 2007

Plasmolysis of rust-infected flax tissue after treatment with sucrose, mannitol, or calcium chloride solutions caused withdrawal of the host plasmalemma from the cell wall and movement of the host protoplast towards the haustorium. The extrahaustorial membrane, however, was not displaced from its position along the haustorial neck or around the haustorial body. In sucrose and mannitol solutions the extrahaustorial matrix was unchanged in volume, which suggests that it is either a more rigid structure than has usually been suggested or an artifact of fixation. After calcium chloride treatment, the matrix was frequently slightly distended and some plasmolysis of the haustorial protoplast was generally observed; this did not occur in the sucrose or mannitol solutions. The possible significance of these findings is briefly discussed.
Functional relationships between soil fungi and environment in alpine tundra
Authors: Bissett J. , Parkinson D.
Published: November 2007

Temperature, moisture, available potassium, and soil pH were the most important abiotic variables influencing the distribution and community composition of soil fungi from three diverse alpine habitats. The major differences in species composition occurred among the sites. An ordination contrasting the sites, based on the species composition of the mycoflora, was correlated with a gradient contrasting temperature and moisture with potassium. The observed differences in species composition among the sites were concluded to have resulted from conflicting demands on the species for efficiency and adaptability. Relatively few species were isolated from the more exposed summit ridge site (2840 m). and these were probably genetically diverse species capable of adapting to environmental extremes. Alternatively, dominant species may be specialists adapted to limiting dimensions that are widely distributed in the environment. Dominant species at the drought-prone grassland site (1900 m) appeared adapted to low moisture, and those of the alpine meadow site (2530 m) to low temperature.Seasonal changes in mycoflora composition were related to changes in the moisture and temperature status of the soils, with low temperature limiting in the spring and low moisture in the fall. Chrysosporium pannorum and Penieillium janthinellum were adapted to combined low temperature and moisture. Cylindroearpon didymuin, Glioeladium deliquescens, Fusarium merismoides. Penicillium steckii, and Cylindrocarpon destructans occurred only in soils with a relatively high temperature–moisture status. Changes in mycoflora composition with soil depth were attributed to an environmental gradient combining temperature, moisture, and K without contrasts. Sterile fungi, apparently adapted to the adverse conditions of low temperature. moisture, and K. were dominant in the lower horizons at all three sites. Soil K appeared to be a limiting factor for many species restricted to the surface horizons, including the frequently isolated species Fusarium acuminatum. Penicillium janthinellum. Penicillium simplicissimum. Penicillium steckii. Phoma eupyrena. and Trichoderma liamatum.
A cytological study of intraspecific variation in Ceratopteris thalictroides
Authors: Hickok Leslie G.
Published: November 2007

A cytological study of meiotic pairing behavior in intraspecific hybrids was undertaken utilizing seven different collections of Ceratopteris thalictroides. Two mutant gametophyte stocks with nonfunctional spermatozoids were utilized to facilitate the synthesis of intraspecific hybrids. Low levels of univalent and quadrivalent formation were found in most of the hybrids, indicating that some structural differences existed, but major pairing homologies were still evident. The fertility of hybrids ranged from 10 to 75% spore germination. One collection, from Hawaii, showed high levels of univalent formation and very low spore viability. In that this stock is both biologically and morphologically distinct, it should be given taxonomic recognition. The study, in general, is in agreement with the most recent taxonomic treatment of Ceratopteris in that it shows a significant amount of cytological variation within the polymorphic species C. thalictroides.
Leaf senescence as a factor in the competitive and synergistic interactions of Drechslera sorokiniana and Curvularia geniculata on Poa pratensis
Authors: Hodges Clinton F. , Madsen James P.
Published: November 2007

The competitive and synergistic interactions of Drechslera sorokiniana and Curvularia geniculata on pathogenesis of leaf spot was evaluated on sequentially senescent leaves of Poa pratensis. Leaf age had no effect on the mean number of lesions produced from inoculations with D. sorokiniana or C. geniculata alone. The combination of D. sorokiniana and C. geniculata produced a significant increase in the mean number of lesions between the youngest and oldest leaves at 20, 25, and 30 °C. Disease severity on leaves of all ages resulting from inoculations at 20 and 25 °C was greatest in response to D. sorokiniana alone, followed by the combination of organisms, and by C. geniculata alone, in descending order. No difference in disease severity occurred on leaves of different ages in reponse to the inoculations at 20 °C, but a significant increase in disease occurred on the two oldest leaves at 25 °C in response to inoculations with D. sorokiniana and to the combination of organisms. At 30 and 35 °C, disease severity on leaves of all ages was greatest in response to inoculations with the combination of organisms, D. sorokiniana alone, and C. geniculata alone, in descending order. Disease severity increased from the youngest to the oldest leaves at 30 °C in response to inoculations with the combination of organisms or with D. sorokiniana alone. Reisolations established that inoculations with D. sorokiniana alone resulted in successful establishment of the pathogen in the tissue of leaves of all ages at 20, 25, and 30 °C. At these temperatures, inoculations with C. geniculata alone produced a significantly higher level of reisolation from the youngest to the oldest leaves of the shoot. Reisolation of the individual organisms from leaves inoculated with both organisms showed that C. geniculata established more successfully than D. sorokiniana in leaves of all ages as temperatures were increased. It was concluded that the synergistic increase in disease produced by the combination of D. sorokiniana and C. geniculata at high temperatures is the result of increased high-temperature growth of C. geniculata which is probably more saprophytic than parasitic on senescing, heat-stressed leaves and does not reflect a high-temperature increase in virulence of this organism.
The regenerative capacity of root cuttings of Taraxacum officinale under natural conditions
Authors: Mann H. , Cavers P. B.
Published: November 2007

Plants of Taraxacum officinale Weber were grown from the seeds of a single parent. At monthly intervals during two successive growing seasons, and commencing [Formula: see text] months after germination in June 1974, randomly selected plants were excavated and the roots divided into 2 cm long fragments. Fragments were replanted at different depths and in different orientations.Percentage survival (regeneration and survival for at least 4 months) displayed seasonal variation with a minimum of 5–32% survival for fragments obtained in May 1975 at the time of maximum flowering of the source plants and for very young fragments obtained in the first treatment in July 1974. The highest percentage survival, 60–100%, occurred for fragments obtained in the second growing season from June to September, inclusive. Weather conditions appear to exert a significant effect on the magnitude of the flowering response, but not the timing of the spring flowering peak.Regenerative capacity declined consistently down the length of the root in relation to a concomitant decrease of fragment volume, but increased with respect to age for cuttings of a given volume. Rotation of cuttings away from the normal planting orientation resulted in a decline in percentage survival, and an increase in regeneration time. Depth of planting down to 10 cm did not consistently influence either percentage survival or time for regeneration.The time taken for regeneration was largely dependent on climate, with fragments planted in September 1974 regenerating most quickly (an average of 20 days), and fragments obtained in October 1974 taking the longest time to regenerate (174 days). In addition, time for regeneration was positively correlated with fragment volume. These results show that under natural conditions survival of fragments is not independent of season, and is significantly lower than 100% as previously reported from laboratory studies of regeneration.
Structural studies of the development of infection structures of cowpea rust, Uromyces phaseoli var. vignae. II. Vacuoles.
Authors: Heath I. Brent , Heath Michèle C.
Published: November 2007

During development of infection structures of cowpea rust, Uromyces phaseoli var. vignae, migration of cytoplasm from one structure to the next is accompanied by production of vacuoles. The developmental pathway of these vacuoles appears to differ in different sites of production. In germinating uredospores, appressoria, and substomatal vesicles, their development includes the formation and enlargement of electron-opaque globule-containing vesicles, termed vacuole precursor vesicles (VPVs). In contrast, in the elongating germ tubes and vacuolating haustorial mother cells, VPVs do not appear during vacuolation. During development of VPVs into vacuoles there seems to be a control system which selectively activates only a portion of the VPV population.
Salvinia leaves. II. Morphogenesis of the floating leaf
Authors: Croxdale Judith G.
Published: November 2007

The floating leaves of Salvinia arise in a manner not previously described in plants. Leaf morphogenesis is the result of meristematic activity in the leaf apical cell and two abaxial meristems. These abaxial meristems originate in the dorsal sectors of the primordium and are separated from one another by a notch which runs the length of the primordial blade region. Each meristem consists of a single longitudinal file of cells which increases the width of the blade panel by strict anticlinal divisions. These anticlinal derivatives divide periclinally to establish the cell layers of the lamina. Unlike most dorsiventral leaves in which the blade is produced by a marginal meristem. Salvinia floating leaf blade panels increase radially by the action of these abaxial meristems. Thus, the leaf surface exposed to the air is morphologically the abaxial surface and that in contact with the water is the adaxial surface. Leaf differentiation and maturation are acropetal in the longitudinal direction and from the midvein to the margins in the horizontal direction.
Etude du bourgeonnement in vitro de l'écaille du bulbe de Tulipe
Authors: Rivière Simonne , Muller Jean-François
Published: November 2007

Vegetative propagation of tulips in vitro, not performed until now, is obtained using as explants scales of daughter bulbs collected in winter. Twenty-five percent of these explants give rise to neoformed buds within 6 months. These buds evolve into bulbs which are able to develop in the soil. Their ontogeny is studied histologically, from the beginning of the culture to the neoformed bulb formation. A treatment with low temperature and darkness at the beginning of the culture period promotes an earlier bud initiation.
Nonparasitic pathogenesis of germinating tomato by Pythium myriotylum
Authors: Csinos Alexander S.
Published: November 2007

Surface-disinfested seed of pepper, cowpea, sorghum, and three cultivais of tomato were placed onto petri dishes containing water agar amended with powdered, lyophilized mycelium of Pythium myriotylum cultured on a liquid, glucose–glutamate medium. Only the germinating seed of tomato cultivais were adversely affected. Hypocotyl length and root length of seedlings were reduced more than 42 and 74%, respectively, when grown on water agar amended with 25 μg/mL of P. myriotylum mycelium. At 250 μg/mL of mycelium, root tips and hypocotyls became necrotic, roots were discolored, and seedlings were killed. When we autoclaved the mycelium-amended water agar at pH values at or above 6.0, the activity of the mycelial toxin(s) was significantly decreased. Roots were affected more than hypocotyls by the toxin(s). Mycelial suspensions which were sterilized by sonication were more toxic than suspensions that were autoclaved. The data support the report that P. myriotylum produces toxin(s) active on tomato and suggest that P. myriotylum mycelium contains toxin(s) that may play a role in preemergence damping-off of tomato. Toxin(s) from soil-borne fungi may be involved in poor crop performance.
Coelomycetes on Liliales: Dothiorella smilacina and Stagonospora smilacis
Authors: Bissett J.
Published: November 2007

The fungi related to Dothiorella smilacina (Peck) Petrak & Sydow and Stagonospora smilacis (Ellis & Everh.) Saccardo were studied. Because of the continuity of variation observed in the available herbarium material and in numerous isolates, a large number of epithets are placed in synonymy with Macrophoma smilacina (Peck) Berl. & Vogl. Two varieties are distinguished for the species, with M. smilacina var. smilacis (Ellis & Everh.) comb. nov. differing from M. smilacina var. smilacina primarily in the production of a pigment in the walls of mature conidia of the former. Both varieties are widely distributed in North America with hosts in Liliaceae (Asparagoideae and Melanthioideae) and Smilacaceae.
Anomalous apetaly: localized character displacement in Ranunculus eschscholtzii
Authors: Fisher F. J. F. , Warner A. , Reimer E. M.
Published: November 2007

Apetaly is usually a rare variation in populations of the widespread hexaploid alpine Ranunculus eschscholtzii Schlecht. In certain high rainfall sections of the western Cascade Mountains of Washington, where populations of the hexaploid have been found in mixed association with those of a diploid relative, R. suksdorfii (elsewhere ecologically well separated though sympatric), the apetalous condition almost completely replaces the normal form. Any petal-bearing flowers of the hexaploid attract the flying pollen vectors (mainly syrphids) which also visit the overwhelmingly more numerous diploid species. Any resulting hybrids between the two species are sterile. Apetalous flowers are avoided by the syrphid pollinators. These flowers, nevertheless, regularly produce full sets of viable fruits. This may be attributed to the regular foraging visits of large terrestrial ants. The apetalous condition of R. eschscholtzii appears to have replaced the normal form in the high rainfall areas because only it can continue to reproduce and maintain the species in the presence of R. suksdorfii and the syrphid pollinators. This regional intensification of reproductive barriers between species already genetically isolated by their difference in ploidy, and between which hybrids have zero fitness, is interpreted as a case of character displacement involving both competition for a resource (pollinators) and hybrid sterility.
Hyphal tip growth in Achlya: Enzyme activities in mycelium and medium
Authors: Hill T. W. , Mullins J. T.
Published: November 2007

Achlya ambisexualis Raper is a coenocytic, hyphal water mold which exhibits apical vegetative growth when cultured on a denned liquid medium. Upon transfer to a medium containing only glucose, growth is reduced considerably as measured by changes in fresh weight, incorporation of exogenous glucose into hyphal walls, and secretion of cellulase. Of the enzymes tested, only cellulase and alkaline phosphatase exhibit higher specific activities in growing mycelia than in nongrowing mycelia; the specific activity of UDPG transferase remains about the same. All enzyme activities found in mycelial extracts also were present in the culture filtrate. The only enzymes showing much higher activities in the filtrate than in the mycelium were ATPase and cellulase. Possible roles for cellulase during growth are discussed.
On the persistence and dispersal of transantarctic Hepaticae
Authors: Schuster Rudolf M.
Published: November 2007

The dispersal of a considerable number, if not the vast majority, of southern hemisphere Hepaticae chiefly belonging to "old" families and suborders can be visualized as resulting primarily from short-range or "step-wise" dispersal, as part of structural communities, before the final disassembly of the presently fragmented Gondwanaland. Often with the disruption of gene flow, disjunct populations of once continuously distributed Gondwanalandic taxa have undergone speciation, in most cases as physical disruption occurred. Significant relict and disjunct distribution patterns for 21 hepatic taxa are mapped and discussed. A discussion of (i) rate of speciation and genus formation, (ii) efficiency of long-distance dispersal, and (iii) the geological background is presented with the purpose of explaining the origins of antipodal distribution patterns within the Hepaticae.
The moss flora of the Auckland Islands, New Zealand, with a consideration of habitats, origins, and adaptations
Authors: Vitt Dale H.
Published: November 2007

The moss flora of the Auckland Islands (50°40′ S latitude and 166°00′ E longitude) consists of 145 species and seven varieties in 75 genera. A detailed description of the habitat of each taxon is given. The vegetation, climate, and history of the islands, as they pertain to bryology, are reviewed. Four broad vegetational zones are recognized: forest, scrub, tussock grassland, and tundra as well as areas of herbfields and mires. Phytogeographically, the most common pattern of distribution is Australasian with 29% of the moss species found in both New Zealand and Australia. Other patterns are common as well. Discussion is orientated toward species richness variability in polar regions. The origins and adaptations of mosses in subantarctic landscapes are reviewed and correlations drawn between particular growth forms and individual moss floras and habitats.
The phytogeographical relationships of the lichen flora of Tristan da Cunha (excluding Gough Island)
Authors: Jørgensen Per M.
Published: November 2007

Based on examination of some 700 specimens, the lichen flora of Tristan da Cunha is reported to consist of 82 species. Of these, about 5% are endemics. Approximately 20% of the lichens belong to a Southern Hemisphere element, while about 70% are widespread in their distribution, most of the latter being temperate "oceanic" species. It is suggested that the lichen flora is young in age and the result of long-distance dispersal; mostly Magellanic in origin.
Habitats of circumboreal–subarctic sphagna: I. A quantitative analysis and review of species in the Caribou Mountains, northern Alberta
Authors: Horton Diana G. , Vitt Dale H. , Slack Nancy G.
Published: November 2007

A quantitative analysis of the habitats of 14 species of Sphagnum found in the Caribou Mountains of northern Alberta and a literature review are the basis for a discussion of the habitats of these species as they occur in circumboreal–subarctic regions. Despite the implication inherent in the name, the Caribou Mountains are not mountains; the formation is an extensive, elevated plateau, which is underlain by more-or-less continuous permafrost. Three habitat types predominated in our study area: an upland "treed-tundra" (which is dominant over much of the plateau) with scattered Picea mariana and a hummocky bottom layer of sphagna; rounded "thaw-pocket" depressions dominated by carpets of Sphagnum and some carices; and streams defined by a dense zone of shrubs with the narrow water channel bordered by more-or-less firm lawns of Sphagnum species. Three gradients, which are considered to have a predominant influence on the occurrence of Sphagnum species, are wet to dry, ombrotrophic to minerotrophic, and shaded to exposed. The relative importance of each of these factors varies with each species of Sphagnum. Sphagnum jensenii, S. majus, S. riparium, and S. lindbergii occur exclusively in weakly minerotrophic to ombrotrophic, aquatic habitats where populations form loose, floating carpets. Such habitats are generally not much shaded. Such species as S. angustifolium, S. teres, and S. russowii are characteristic of somewhat less moist conditions, but all have a broad amplitude along the ombrotrophic to minerotrophic gradient. However, S. angustifolium is most abundant under poorly minerotrophic conditions where there is less shade, while S. teres predominates under highly minerotrophic conditions and is more-or-less equally tolerant of shade and exposure. Sphagnum warnstorfii apparently is restricted to habitats which are highly minerotrophic, but is tolerant of both shade and exposure. The sphagna most characteristic of densely shaded, woodland habitats where there is little peat development are S. squarrosum, S. wulfianum, and S. girgensohnii. All three species generally form low mounds. Sphagnum fuscum and S. nemoreum form well-defined hummocks and are most prevalent under ombrotrophic conditions.
Effects of short-term temperature fluctuations on leaf photosynthesis in corn (Zea mays)
Authors: Thiagarajah M. R. , Hunt L. A. , Hunter R. B.
Published: November 2007

The effects of short-term temperature fluctuations on net photosynthetic rates (Pn) are described for a single-cross corn (Zea mays L.) hybrid (Harrow 691). The hybrid was grown at 25 °C and subjected to 4 days at either 15 or35 °C, and then maintained at 25 °C. Genotypic differences in tolerance of Pn to low temperature were studied using 12 hybrids of different maturities grown at 25 °C and subjected to 4 days at 15 °C.Following low temperature treatment. Pn was initially reduced by about 15% for leaves 5. 9. and 13 of hybrid Harrow 691. but completely recovered after 1 day at 25 °C. Following high temperature treatment, leaves 5 and 9 showed similar reductions in Pn whereas leaf 13 was not affected. The photosynthetic activity of the heat-stressed leaf 9 recovered after 1 day, but that of leaf 5 showed no recovery for 14 days at 25 °C.Among 12 hybrids. Pn of the newly matured leaf 7 was reduced after the low temperature treatment, but the reduction was more drastic for two late hybrids than for three early hybrids. Most hybrids showed complete recovery of Pn after 1 day at 25 °C. but genotypic differences were evident. The results reported indicate that further evaluation of the amount of genetic variation in temperature stability in corn could be carried out usefully.
Effect of sodium chloride and seawater in Sabouraud dextrose agar medium on some human-pathogenic fungi
Authors: Ekundayo Comfort A.
Published: November 2007

Nine human-pathogenic fungal isolates from Nigeria were cultured on Sabouraud dextrose agar prepared with seawater and solutions containing different concentrations of sodium chloride. Growth was determined by measuring colony diameter after incubation for a maximum of 15 days at 30 °C. The fungi grew and sporulated on seawater, Sabouraud dextrose agar, and Sabouraud dextrose agar containing up to 3.4% NaCl. Growth, however, decreased with increasing concentrations of sodium chloride in the basal medium. Little or no growth occurred in media containing 6.4% NaCl.Aspergillus fumigatus Link, Candida albicans (Robin) Berkh, and Geotrichum candidum Link remained viable for up to 8 weeks in distilled water, 0.85 and 1.7% NaCl solutions, 5 weeks in 3.4% NaCl and sterile seawater, and 4 weeks in 6.8% NaCl.
Massariothea and Paramassariothea gen. nov.
Authors: Subramanian C. V. , Muthumary J.
Published: November 2007

Paramassariothea form-gen.nov., typified by P. falcata form-sp.nov., is proposed to accommodate a pyenidial fungus collected on fallen twigs of Ficus asperima from Coorg, India. The taxonomy of the closely allied form-genus Massariothea H. Sydow and of the three form-species assigned to it is briefly discussed.
Evidence for sexual reproduction in the red algae Palmaria palmata and Halosaccion ramentaceum
Authors: Meer J. P. van der , Chen L. C-M.
Published: November 2007

Plants believed to be female gametophytes of Palmaria palmata and Halosaccion ramentaceum have been discovered in culture. Tetraspores of diploid tetrasporophytes gave rise to two types of haploid sporelings, one of which grew much more robustly and was less branched than the other. A 1:1 ratio of the two types was obtained from random spores and a 2:2 segregation occurred within individual meiotic tetrads. The more robust plants proved to be males which matured relatively quickly and produced abundant spermatangia. The smaller plants, those believed to be females, grew much more slowly and eventually formed sporangia. However, these aborted without releasing viable spores. Nuclear division within the sporangia appeared to be a haploid meiosis. Fertile tetrasporic fronds of P. palmata were obtained from gametophytes in culture on one occasion, and these gave rise to a second generation of segregating sporelings. A life history for P. palmata and H. ramentaceum roughly comparable to that of Liagora tetrasporifera is suggested by the results.
Activité mitotique et croissance des bourgeons axillaires provoquées par la décapitation de jeunes plants de fève (Vicia faba)
Authors: Couot-Gastelier Jeanne
Published: November 2007

Buds of intact plants of Vicia faba L. are partially inhibited. Decapitation of the terminal bud of plants with four leaves leads to the reactivation of all the axillary buds, but to the growth of only the basal ones. The first events induced by the terminal bud excision do not occur at the level of the axillary buds, but affect rather the main axis.The kinetic study of the mitotic reactivation shows that the activation begins in cell layers of the cambial zone in the subapical internodes of the stem 1 h after decapitation and after 4 h in the more basal ones.The subapical axillary buds are first reactivated, but only temporarily, 8 h after the principal bud excision. The lower axillary buds are reactivated later, after 12 h, and their growth then becomes autonomous.These results are discussed with regard to the regulatory role of the main axis on axillary bud growth.
Studies of the powdery-mildew fungus, Leveillula taurica, on green pepper. II. Light and electron microscopic observation of the infection process
Authors: Kunoh Hitoshi , Kohno Mitsuru , Tashiro Sadayoshi , Ishizaki Hiroshi
Published: November 2007

Almost all ultrastructural studies of powdery-mildew fungi have been focused on the epiparasitic fungi. In this paper, one of the endoparasitic powdery-mildew fungi, Leveillula taurica (Lev.) Arn., on green pepper (Capsicum annuum L. var. angulosum Mill.) leaves was investigated by light and electron microscopy. Most germinated conidia formed a lobed adhesion body (similar to the appressorium in morphology but different in function) before stomatal invasion. The track of the adhesion body on the leaf epidermis was depressed, and no cuticular perforations were observed in it. After stomatal invasion, infection hyphae grew extensively into the intercellular spaces of the leaves and formed haustoria in the spongy- and palisade-parenchyma cells. The haustorium was flask shaped with a neck arising from the intercellular hypha. The overall profiles of the haustorium resembled those of epiphytic powdery-mildew fungi of other authors; the haustorium was composed of a nucleate central body and many anucleate lobes, and the entire structure was bounded by an extrahaustorial membrane. Papillae consisting of three distinct regions formed against the outer cell walls at the site of penetration. The most obvious alteration in infected host cells was a marked increase in the number of large lipid bodies. Lipid bodies increased in number with time after haustorial formation. They appeared first in the host cytoplasm near the extrahaustorial membrane, then in the extrahaustorial matrix and haustorial body.
Mise en évidence d'activités enzymatiques au niveau de l'haustorium d'une phanérogame parasite : Striga hermonthica (Scrophulariaceae)
Authors: Ba Amadou Tidiane , Kahlem Guy
Published: November 2007

Acid phosphatase, ATPase, peroxidase, succinate dehydrogenase, and cytochrome oxidase activities have been demonstrated in the haustorium of Striga hermonthica, a parasitic phanerogam on millet (Pennisetum typhoideum var. Sonna 3). Their localization has been specified and their possible role discussed. These enzymatic activities seem to be related to the host penetration mechanism and also with the process of active transport of solutes between host and parasite. A tracheid radial system has also been discovered in the mature haustorium.
Developmental studies on Euphorbia esula. Evidence of competition for water as a factor in the mechanism of root bud inhibition
Authors: McIntyre Gordon I.
Published: November 2007

Seedlings of leafy spurge (Euphorbia esula L.) were grown in sand culture under controlled conditions and experiments were designed to test the hypothesis that competition for water between the root buds and the parent shoot is a significant factor in the mechanism of root bud inhibition. It was shown that the water content of the root buds increased by approximately 25% within 24 h of the removal of the parent shoot. Root bud length increased significantly between 24 and 48 h from shoot removal but while some of the buds continued to grow others were apparently reinhibited. Shoots with all immature tissue removed continued to exert a high degree of root bud inhibition but this inhibition was markedly reduced by keeping the plants in a high humidity. Increasing the humidity from approximately 50 to 95% also caused a significant increase in the rate of emergence and elongation of shoots produced from root buds following the removal of the parent shoot. This effect on emergence was suppressed by conditions presumed to reduce the degree of root bud aeration. Taken as a whole, the results lend considerable support to the concept of internal competition for water as a factor in the mechanism of root bud inhibition.
Reproductive strategies in intertidal populations of two co-occurring seagrasses (Zostera spp.)
Authors: Harrison Paul Garth
Published: November 2007

Reproductive strategies were analyzed in intertidal populations of two seagrasses of the genus Zostera to test the application of r–K selection theory to a novel habitat. Zostera americana has appeared in the study area recently and is spreading rapidly. It grows in the mid to upper intertidal regions and is an r-strategist; i.e., a rapidly growing, essentially annual plant that uses a large proportion (up to 25%) of its resources for flowering. Zostera marina, the native eelgrass, grows in the mid to low intertidal regions and is a K-strategist; i.e., a perennial that uses a large proportion of its resources for maintenance via rhizomes and roots. Considering that the environment becomes less predictable for marine plants on a gradient from the lower to the upper end of the intertidal zone, then the two seagrasses behaved as predicted by the theory.
The effect of the hydrocarbon naphthalene on the morphology of the green flagellate Chlamydomonas angulosa
Authors: Soto C. , Hellebust J. A. , Hutchinson T. C. , Sheath R. G.
Published: November 2007

The morphological changes of Chlamydomonas angulosa, when incubated with a 50% saturated solution of the aromatic hydrocarbon naphthalene, have been studied. Comparisons are made with the effects of crude oil. Observations under the light microscope reveal a totally inhibited motility, loss of flagella, an increase in the activity of the contractile vacuoles, and the appearance of cytoplasmic granulation. The cells were found to develop a surrounding transparent envelope. With electron microscopy, the following ultrastructural changes were revealed: the cell wall became partially thickened and a widened space developed between the cell wall and the plasmalemma; abnormal chloroplast lamellae developed, composed of numerous thylakoids; starch grains increased in number and in size; the osmiophilic granules of the stigma became a hollow core with peripheral structure and electron-dense material became heavily deposited inside the cytoplasmic vacuoles. This material stained deeply with Sudan black B, indicating its lipid nature. No recovery of cells was found during the 8-day incubation period with naphthalene, in contrast to recoveries noted with crude oil treatment. The lipid deposits in the vacuole also showed no indication of migration or reduction during this period.
Roles of endogenous and exogenous growth regulators in dormancy of Utricularia vulgaris
Authors: Winston Robert D. , Gorham Paul R.
Published: November 2007

The roles of endogenous and exogenous growth regulators on dormancy control of Utricularia vulgaris were investigated by extraction and bioassay of endogenous levels of four classes at various developmental stages and by measuring the effects of synthetic regulators on these stages. The bioassays used were oat coleoptile for auxins, abscisic acid and other inhibitors; lettuce hypocotyl for gibberellins; and soybean callus for cytokinins. Two weeks before turion formation and during innate dormancy abscisic acidlike and bound gibberellinlike levels were high while free gibberellinlike and auxinlike levels were low. Abscisic acid exogenously applied to actively growing plants rapidly induced turion formation even under noninductive environmental conditions. Kinetin rapidly and completely caused sprouting in innately dormant turions but would not promote continued vegetative growth. These plants formed new turions within 2 weeks of sprouting. During imposed dormancy, when turions rapidly sprouted, there was a low level of abscisic acidlike inhibitor and high levels of gibberellinlike and auxinlike compounds. Turions collected during this state could be maintained in a dormant condition by incubation with abscisic acid even at high temperatures which normally induce sprouting. During sprouting the endogenous growth regulator pattern was similar to that described for imposed dormancy. A model of the environmental and growth regulator factors which control dormancy is presented.