bluuebunny/crossref_metadata_2025 huggingface dataset:
Testing the accuracy of using peroxidase activity to indicate stigma receptivity
Authors: Galen Candace , Plowright R. C.
Published: September 2008

Stigma peroxidase activity was tested in flowers of Pedicularis canadensis and Clintonia borealis at discrete age-classes during the course of anthesis. For recipient flowers of each age-class pollen adhesion, rate of pollen germination, and total number of grains germinating on stigmas were scored following hand-pollination. In P. canadensis, the onset of detectable peroxidase activity occurred at the transition from the juvenile to pollen-dehiscing age-class. Concurrently, the stickiness of the stigma surface and total number of grains germinating on the stigma increased significantly. Stigma peroxidase was present to some degree throughout anthesis in C. borealis. However, the percentage of the stigma surface in which peroxidase was detectable increased significantly between straight-sided and medium-curled flower age-classes. Again, corresponding increases occurred in the stickiness of the stigma surface and total number of grains germinating. Results suggest that for both species stigma peroxidase activity is a reliable indicator of receptivity.
Lack of gravitropic response of tumour roots of Forsythia intermedia: cytological evidence for this behaviour
Authors: Bronner R. , Dreger-Jauffret F. , Pfirsch E.
Published: September 2008

Tumours of Forsythia intermedia Zab. consist of clusters of roots characterized by limited growth. These roots are agravitropic and have a nontypical cap without starch. Placed in moisture, the roots elongate in the same direction as they had on the plant, without any gravitropic curvature. Elongated roots have a caplike area, the cells of which exhibit amyloplasts. The absence of gravitropic response of the elongated roots was confirmed experimentally. Amyloplasts of the columella cells do not sediment in the direction of gravity, even after modification of the position of the root with respect to gravity. The reason for this agravitropism of Forsythia intermedia tumour roots is discussed in relation to their cytological features.
The ecology of Ramalina menziesii. VI. Laboratory responses of net CO2 exchange to moisture, temperature, and light
Authors: Matthes-Sears U. , Nash III T. H. , Larson D. W.
Published: September 2008

The response of net CO2 exchange to thallus water content, thallus temperature, and photosynthetically active radiation was measured in the laboratory for two morphologically different forms of Ramalina menziesii collected from a coastal and an inland habitat in central California. Equations describing the response curves are fitted to the data and compared statistically for the two sites during two seasons. Significant differences were present for all responses both in summer and winter but were more pronounced for net photosynthesis than for dark respiration. The main differences between the two forms were in the absolute rates of net photosynthesis; a maximum of 6.2 was measured for the inland form but only 3.6 mg∙g−1∙h−1 for the coastal form. Chlorophyll contents were also different between the two forms, indicating that chlorophyll is the likely cause for the difference in net photosynthetic rates. Net photosynthetic rates were higher at low temperatures during winter than during summer, but otherwise seasonal variations in the gas exchange responses were relatively minor. Both forms of the lichen are light saturated at quantum fluxes greater than 200 μE∙m−2∙s−1. Both show an optimum temperature for maximum CO2 exchange at 25 °C, well above the mean operating temperature of R. menziesii in the field.
A reevaluation of Wrightoporia and Amylonotus (Aphyllophorales, Polyporaceae)
Authors: David Alix , Rajchenberg Mario
Published: September 2008

New species of Wrightoporia Pouz. from Africa and Asia have features that overlap the limits of Amylonotus Ryv. We found dextrinoidicity, wall coloration of the skeletal hyphae, and the general morphology of the fruit bodies to be variable features in both genera. Gloeopleurous hyphae and gloeocystidia or pseudocystidia occur in all species of these genera so far studied. The synonymy of Amylonotus with Wrightoporia is proposed. The following new taxa are described: Wrightoporia dimidiata David & Rajch., W. gillesii David & Rajch., and W. ramosa David & Rajch. Two new combinations are proposed: W. flava (Ryv.) David & Rajch. and W. ochrocrocea (Henn. & Nyman) David & Rajch.; W. pouzarii David & Rajch. is a new name for A. africanus Ryv. Cultural characters of W. flava (Ryv.) David & Rajch., W. gillesii David & Rajch., and W. tropicalis (Cke.) Ryv. are described. The position of W. cylindrospora Ryv. and W. tropicalis (Cke.) Ryv. in the context of the genus and the relationships of Amylosporus Ryv., Heterobasidion Bref., and Wrightoporia Pouz. are discussed. Rigidoporopsis Johans. & Ryv. is considered a synonym of Amylosporus Ryv.
The phenomenon of "nonmycorrhizal" plants
Authors: Tester M. , Smith S. E. , Smith F. A.
Published: September 2008

Most species of plants are normally infected by mycorrhizal fungi, but some plant taxa do not usually form generally recognisable mycorrhizas. The identity and relationships of these "nonmycorrhizal" or weakly mycorrhizal taxa are considered in this review. Mechanisms that are used by the plants for avoiding infection are discussed. Exudation of fungitoxic compounds or simply low levels of exudation are not believed to inhibit infection. Similarly, the presence of fungitoxic compounds in root cortex cells is not believed to prevent mycorrhizal fungi from infecting weakly mycorrhizal plants. It is proposed that the control of mycorrhizal fungal penetration is exerted by interactions between the organisms at the level of the cell wall and (or) middle lamella.
Control of nitrogen assimilation in Stichococcus bacillaris by growth conditions
Authors: Ahmad Iftikhar , Hellebust Johan A.
Published: September 2008

Stichococcus bacillaris Naeg. (Chlorophyceae) grown on a 12 h light: 12 h dark cycle divides synchronously under photoautotrophic conditions and essentially nonsynchronously under mixotrophic conditions. Photoassimilation of carbon under photoautotrophic conditions was followed by a decline in cell carbon content during the dark period, whereas under mixotrophic conditions cell carbon increased throughout the light–dark cycle. The rates of nitrogen assimilation by cultures grown on either nitrate or ammonium declined sharply during the dark, and these declines were most pronounced under photoautotrophic conditions. Photoautotrophic cells synthesized glutamine synthetase and NADPH – glutamate dehydrogenase (GDH) exclusively in the light, whereas in mixotrophic cells about 20% of the total synthesis of these enzymes during one light–dark cycle occurred in the dark. NADH–GDH was synthesized almost continuously over the entire light–dark cycle. In the dark, both under photoautotrophic and mixotrophic conditions, the alga contained more than 50% of glutamine synthetase in an inactive form, which was reactivated in vitro in the presence of mercaptoethanol and in vivo after returning the cultures to the light. The thermal stability of glutamine synthetase activity was less in light-harvested cells than in dark-harvested cells. The inactivation of glutamine synthetase did not occur in cultures growing either heterotrophically in continuous darkness or photoautotrophically in continuous light. This enzyme appears to be under thiol control only in cells grown under alternating light–dark conditions, irrespective of whether this light regime results in synchronous cell division or not.
Organization of the kinetosomes and associated structures of zoospores of the rumen chytridiomycete Neocallimastix patriciarum
Authors: Munn E. A. , Greenwood C. A. , Orpin C. G.
Published: September 2008

The structure of the kinetosomes of zoospores of the Babraham isolate of Neocallimastix (N. patriciarum, previously described as N. frontalis) both free and in the later stages of zoosporogenesis have been determined from electron micrographs of thin sections. The zoospores have up to 20 flagella. At the base of each, within a circular ridge of the plasma membrane, is a circumflagellar ring. There are no props connecting the triplets of the kinetosome to the plasma membrane, but there are two connections from the skirt around the kinetosome to the circumflagellar ring. In developing zoospores, within sporangia, the circumflagellar ring is perpendicular to the long axis of the flagellum, but in free zoospores it is tilted at an angle of about 60°. The skirt is continued proximally to form a cowl-shaped structure below the kinetosome. The spur has longitudinal and transverse components; microtubules radiate from both. Some microtubules intersect the nucleus, but there is no specific association. The classification of Neocallimastix is discussed.
Mycorrhizae in a California serpentine grassland community
Authors: Hopkins Natalie A.
Published: September 2008

The grassland community on serpentine soil was found to have vesicular–arbuscular mycorrhizae. Twenty-seven species made up the herbaceous cover; 23 were annuals. Two annual species were from nonmycorrhizal families, but one had some colonization. Twenty-five species had colonization in over half the length of the roots. Annuals had especially heavy colonization, which frequently filled the cortex of the root. Of the herbaceous cover in the community 98% was mycorrhizal; 97% was colonized in over half the length of the roots; and 91% was colonized in over three-fourths the length of the roots. The common fungal symbionts were Glomus fasciculatum and Glomus tenue.
Intracellular activity of mycelial proteinases during fruit-body development in Flammulina velutipes
Authors: Chao Ema E. , Gruen Hans E.
Published: September 2008

In the mycelium of Flammulina velutipes cultured on potato–glucose solution the concentration of water-soluble protein began to decrease steeply before fruit bodies formed, but the total amount of protein per culture decreased only when fruit bodies began to elongate rapidly. The level remained very low during rapid elongation. Proteinase activity per unit weight of mycelium against milk protein and azoalbumin decreased in parallel with the concentration of mycelial protein. Activity against azure blue – hide powder was low until the onset of rapid fruit-body elongation and reached a maximum later during that phase. Azoalbumin was hydrolyzed more actively than hide powder. Proteolytic activity per gram of mycelium against mycelial protein was almost the same before fruiting as during rapid fruit-body elongation. Specific activities per milligram protein against the three types of nonnative substrates increased in parallel to a maximum late during rapid elongation when protein concentration was lowest. Specific activity against native mycelial protein was also higher in extracts from older mycelia. Proteolysis was optimal near neutral pH and very low at pH 3.2. Tests with group-specific proteinase inhibitors showed that metallo-proteinases predominate in the mycelium. Serine, and to a lesser extent carboxyl and thiol proteinases, were also present. Neither endogenous inhibitors nor activators of proteolysis were detected.
Étude d'une situation de sympatrie entre diploïdes et tetraploïdes de Dactylis glomerata (Gramineae), sur la base du polymorphisme enzymatique et phénolique
Authors: Ardouin P. , Jay M. , Lumaret R.
Published: September 2008

Sympatric diploid and tetraploid cocksfoots (Dactylis glomerata L.) were analyzed from a biochemical and phytochemical point of view: the distribution of 15 isozymes and 40 phenolic compounds have been studied on about 40 individual plants. Results indicate that the two cytotypes have developed different isozymic and phenolic patterns; nevertheless, several biochemical markers bore witness to affinity between both ploidy levels and gave support to the hypothesis of an autopolyploidy process.
Cell and nuclear area, RNA and protein content, and chromosome counts in meristematic cells of secondary roots and callus of Cocos nucifera
Authors: Armstrong S. W. , Francis D.
Published: September 2008

The relationships between cell area, nuclear area, and cellular RNA and protein content were determined for mitotic cells in callus lines D-80, D-81, H-81, and H-83, for which ploidy levels were determined, and compared with the corresponding relationships for cells in the secondary root meristem of dwarf, hybrid, and tall varieties of Cocos nucifera L. Mitotic cells in hypotetraploid line D-80 and diploid H-83 showed increases in cell size and cellular RNA and protein content compared with mitotic cells from dwarf and hybrid root tips. However, there was a disproportionate increase in cell size in lines D-80 and H-83. Probit analysis revealed that cell size and protein and RNA content per cell were less tightly coupled in these callus lines. Apart from line D-80, nuclear area for prophase cells in the other three diploid callus lines was very similar to that in cells of the variety from which each was established. Overall, our results suggest that nuclear and cellular parameters are free to change independently of each other when cells are transferred to culture media. Furthermore, the failure to increase RNA and protein contents by amounts equivalent to changes in cell size may have detrimental effects on the cell cycle in callus cells.
The occurrence of infected cells, with persistent infection threads, in legume root nodules
Authors: Faria Sergio M. de , McInroy Shona G. , Sprent Janet I.
Published: September 2008

A survey of the structure of nodules from primitive legume trees was conducted. All genera examined in the subfamily Caesalpinioideae, some from the Papilionoideae, but none from the Mimosoideae had cells in the central, nitrogen-fixing region in which bacteria were confined by host cell wall material in structures resembling infection threads. However, infection of these cells occurred by intercellular spread of rhizobia rather than by infection threads. It is suggested that infection threads may have evolved in infected cells and later extended to early stages of the infection process including entry into root hairs.
A new species of the genus Cerinomyces
Authors: Maekawa Nitaro
Published: September 2008

A new species, Cerinomyces aculeatus, is described and illustrated. The fungus is macroscopically characterized by having resupinate, effused, nongelatinous, and odontoid basidiomes and microscopically by hyphal pegs, dacrymycetaceous Y-shaped basidia and nodose-septate hyphae. Cerinomyces aculeatus differs from all previously described species in the combination of these characteristics. Basidiospores of this fungus are unicellular when liberated but become septate during germination. The monokaryotic mycelia produce an anamorph of Sporothrix sect. Luteoalba in culture. The hyphal septum possesses a dolipore with nonperforated parenthesomes. These characteristics suggest that C. aculeatus should be placed in the Dacrymycetaceae.
Neotypification of Fusarium tricinctum
Authors: Neish Gordon A.
Published: September 2008

DAOM 194693, a dried culture obtained from CBS 449.67, is designated as the neotype for Fusarium tricinctum (Corda) Sacc. The two extant authentic specimens of the basionym Selenosporium tricinctum Corda and cultures of the anamorph of Gibberella tricincta El-Gholl et al. were also examined. Reasons are given for not designating as type either of Corda's specimens or a specimen obtained from one of El-Gholl et al.'s cultures.
Bryophytes from Nahanni National Park and vicinity, Northwest Territories, Canada. III
Authors: Talbot Stephen S.
Published: September 2008

Forty-four bryophytes are added to the flora of Nahanni National Park and vicinity. Seven species are new to the Northwest Territories.
CO2-fixation enzymes in maize (Zea mays) and grain yield
Authors: Loza-Tavera Herminia , Serrano Bernardo , Molina José D. , Ortega-Delgado Ma. Luisa , Sanchez-de-Jiménez Estela
Published: September 2008

Maize variety Zacatecas 58 (Z0), was used to select, after 12 cycles of mass selection for grain yield, an improved population (Z12). Some agronomical traits were characterized at the end of the selected period in both populations. Ribulose-1,5-bisphosphate carboxylase–oxygenase (RuBPcase) activity, phosphoenolpyruvate carboxylase (PEPcase) activity, protein content, and chlorophyll content were measured in the leaves above the ear, throughout the grain filling period (from anthesis to 40 days afterwards). Various agronomical traits associated with increase in yield, such as length and diameter of ear, rows per ear, and kernels per row, were greater in the Z12 than in the Z0 population. Likewise, the Z12 population showed 50% more yield than Z0, although days to anthesis did not increase significantly. During the grain filling period the leaves of the Z12 population had more activity of RuBPcase but not PEPcase compared with the Z0 population. It is suggested that the higher level of RuBPcase activity observed in the Z12 population might be related to its improved grain yield.
Injection of growth regulators into seeds growing in situ on plants of Phaseolus vulgaris with a double-fruit sink system
Authors: Clifford P. E. , Offler C. E. , Patrick J. W.
Published: September 2008

An injection procedure to deliver growth substance solutions continuously to developing seeds of dwarf bean plants for periods of up to 10 days with minimal damage to seed development is described. Its use in conjunction with experimental plants having a double-fruit sink system enabled a comparison for any growth substance effect within the plant. It was demonstrated that supply of 6-benzylaminopurine (10−5 M) and abscisic acid (10−6 M) singly or in combination to seeds increased seed dry weight significantly but only in plants that were defoliated severely beforehand.
Induction of embryogenesis in callus from immature embryos of Persea americana
Authors: Mooney P. A. , Staden J. Van
Published: September 2008

Both the external morphology and internal anatomy of developing somatic embryoids and plantlets of Persea americana (avocados) were studied. The embryogenic callus, which is embryoidal in origin, was made up of normal parenchymatous tissue toward the centre of a clump of cells and numerous proembryoidal cells on the periphery of the callus mass. Embryogenesis appeared to begin in single cells on the periphery of the callus and from cells on the surface of existing proembryoids. Embryo initials could be recognised by their conspicuous starch contents and by their thickened walls, which lack plasmodesmata. Cell divisions occurred in cells with thickened walls to give rise to globular proembryoids. Proembryoids developed into heart-shaped, torpedo-shaped and cotyledonary embryoids and finally into complete plantlets.
Fungi associated with Onychiurus subtenuis (Collembola) in an aspen woodland
Authors: Visser Suzanne , Parkinson D. , Hassall M.
Published: September 2008

The collembolan Onychiurus subtenuis was extracted from the litter (L), fermentation (F1, F2), and humus (H) layers of an aspen woodland and the fungi associated with the body and faeces were determined. Over 100 species of fungi belonging mainly to the Zygomycotina and Deuteromycotina were isolated, with the number of propagules and taxa per animal tending to decrease from the L to H layers. The fungi having the highest frequency on the greatest number of Collembola were organisms that sporulate prolifically in laboratory culture, including Beauveria bassiana, Cladosporium spp., Mortierella alpina, Penicillium raistrickii, and Verticillium spp. These organisms also occurred on animals extracted from all litter layers. Most taxa, however, were isolated from Collembola extracted from only one or two litter layers. Fungal taxa associated with Collembola from the F1 and F2 and F2 and H were layers most similar, while those associated with Collembola from the L and F2–H layers were least similar. Of the 97 faecal pellets plated on synthetic media, approximately 50% exhibited fungal growth with the fungi being similar to those present on the collembolan body. The fungi most frequently associated with O. subtenuis could be categorized into three functional groups: (i) litter–soil saprophytes; (ii) the insect parasite Beauveria bassiana; and (iii) mycoparasites. The role of O. subtenuis in dispersing fungal propagules as it relates to the life-history strategies of the fungi involved is discussed.
Determinations of chromosome numbers in Viola (Violaceae)
Authors: Canne J. M.
Published: September 2008

Mitotic chromosome counts are given for 73 populations of 14 species of Viola collected mostly from south central Ontario, Canada. The chromosome numbers of all species of acaulescent, blue- to purple-flowered Viola were recorded at 2n = 54; caulescent yellow- and white-flowered species at 2n = 12 and 24, respectively; and acaulescent, white-flowered taxa at 2n = 24 and 44.
Systématique du taxon Arctostaphylos uva-ursi, Ericaceae, en Europe: données nouvelles concernant les populations pyrénéennes et circumpyrénéennes
Authors: Fromard François
Published: September 2008

The common bearberry (Arctostaphylos uva-ursi), a circumboreal trailing shrub belonging to the Ericaceae, has a broad distribution in Europe (from Spain to Iceland) and can grow in areas which are biogeographically and ecologically very varied (from mediterranean to subalpine, from calcareous to siliceous substrata). In this paper, new data are presented on specific variability in these populations based on cytology and phytochemistry. The results, when compared with those previously reported, point to the existence of at least two main population groups: a "nordic" diploid (2n = 26) group, characterised by the flavanols cyanidin and quercetin and the heteroside arbutin and a southwest European tetraploid (2n = 52) group, richer in flavanols (cyanidin, delphinidin, quercetin, and myricetin) and heterosides (arbutin and methylarbutin). These results also allow a discussion of the validity of the subspecies crassifolia recognized within the taxon A. uva-ursi in its Spanish range and of the phylogeny of different European populations of the group. [Translated by the journal]
Ovule maturity in relation to blossom age of a diploid clone of Solanum tuberosum
Authors: Olson A. Randall
Published: September 2008

Numerous ovules from preanthesis and postanthesis gynoecia of a diploid clone of Solanum tuberosum L. were examined with the light microscope. In prefertilization female gametophytes, the formation of a secondary nucleus in the central cell in conjunction with the conspicuous vacuolation of the egg apparatus was identified as a consistent criterion for determining whether or not ovules were mature. There is a gradual increase in the percentage of mature, nonabortive ovules beginning on the day of anthesis and reaching a maximum 3 days later. In terms of pollination biology, mature ovules are available for pollen tube penetration over an extended period of several days.
An improved conductivity method for the measurement of frost hardiness
Authors: Zhang M. I. N. , Willison J. H. M.
Published: September 2008

A suspension culture of Bromus inermis Leyss was grown under a variety of conditions to provide a range of frost hardiness. The growth conditions involved both low-temperature treatment and the addition of abscisic acid to the culture medium. Frost hardiness (LT50, i.e., subzero temperature causing 50% mortality) was estimated by both fluorescein diacetate vital staining and by a conventional method involving estimation of ion leakage from frost-damaged cells by measurement of the conductivity of a bathing solution. It was found that the latter method always underestimated the frost hardiness by comparison with the former. Evidence that the vital staining estimates were reliable is presented. A subsequent time-course study of ion leakage from frost-stressed cultures showed that leakage increased with time of immersion in deionized water, and that the extent of the difference was dependent upon the growth conditions and the minimum temperature experienced. Analysis of the experimental data showed that this ion leakage differential can be used to estimate LT50 reliably by comparison with the vital staining estimates, and it is proposed that the protocol might be useful as an improved standard method in testing the frost hardiness of plant tissues. The physiological basis for this test is discussed.
Chlorophyll metabolism in higher plants. VII. Chlorophyll degradation in senescing tobacco leaves; phenolic-dependent peroxidative degradation
Authors: Kato Misako , Shimizu Seki
Published: September 2008

Not only solubilized chlorophyll but also membrane (thylakoid) and protein (light-harvesting chlorophyll–protein complex) bound chlorophyll of tobacco plants was bleached by a phenolic–peroxidase–H2O2 system. The bleaching rate of thylakoid membranes in old leaves was higher than in young leaves. A similar phenomenon was observed in thylakoid membranes prepared from aged leaves. Peroxidase activity, peroxide content, and total phenolic content were high in senescent tobacco leaves. The defence mechanism against peroxidative chlorophyll degradation was less active in senescent leaves than in young leaves. These results suggest that deterioration of the subcellular environment induced by senescence accelerates chlorophyll bleaching by a peroxidase-catalyzed reaction.
Terverticillate penicillia isolated from underground seed caches and cheek pouches of banner-tailed kangaroo rats (Dipodomys spectabilis)
Authors: Frisvad J. C. , Filtenborg O. , Wicklow D. T.
Published: September 2008

Terverticillate penicillia were important colonists of the underground seed caches and the external cheek pouches of the banner-tailed kangaroo rat (Dipodomys spectabilis) from the North American desert. Two taxa representing the dominant Penicillium populations are described as new varieties of well-known ubiquitous species. Penicillium chrysogenum var. dipodomyis var.nov. produces the antibiotic penicillin but does not produce mycotoxins (PR-toxin and roquefortine C) known from P. chrysogenum. The new variety is further distinguished by having rough-walled stipes. Penicillium aurantiogriseum var. neoechinulatum var.nov. isolates produce penicillic acid, viridicatin, and cyclopenin, metabolites with antibiotic properties, but not the potent nephrotoxins xanthomegnin and viomellein or tremorgenic mycotoxins (e.g., penitrem A). The variety is also distinguished by conspicuously rough-walled conidia. Three additional new varieties which do not produce mycotoxins normally associated with their species are also reported: P. griseofulvum var. dipodomyicola var.nov. produced the antibiotically active compounds patulin and griseofulvin but not cyclopiazonic acid and roquefortine C; P. glandicola var. mononematosa var.nov. and P. glandicola var. confertum var.nov. did not produce roquefortine C, penitrem A, or patulin. Infrequently isolated strains of the species P. viridicatum and P. griseofulvum duplicated the mycotoxin profiles of the cultures ex type. It is suggested that the evolution of seed-caching behaviour in D. spectabilis may have guided the selection of less-toxic terverticillate penicillia as colonists in rodent seed caches.
Destruction of nematodes by species of Pleurotus
Authors: Barron G. L. , Thorn R. G.
Published: September 2008

On water agar, Pleurotus ostreatus produces tiny droplets of toxin from minute spathulate secretory cells. Nematodes touching such droplets show a sudden and dramatic response. The head region shrinks considerably; this is accompanied by displacement of the oesophagus and (or) disruption of the tissues surrounding the oesophagus. In as little as 30 s, and usually within several minutes, the nematode becomes more or less immobilized but is not killed. Stimulated by leakage products from the immobilized host, directional hyphae converge on the body orifices of the nematode. These hyphae penetrate one or more body orifices and colonize and digest the host. Pleurotus strigosus, P. subareolatus, and P. cornucopiae behave in a similar way. On potato dextrose agar, P. cystidiosus produces numerous secretory cells, but the toxin is much less potent. On water agar directional hyphae of Pleurotus ostreatus can also be attracted to minute bacterial colonies, which are invaded and apparently digested.
Application of the sucrose inversion method to delineation of region-wide temperature patterns
Authors: Denton Shirley R. , Barnes Burton V.
Published: September 2008

The sucrose inversion method is an inexpensive tool for estimating mean temperature. Heretofore, the method has been limited to use in ecological studies where field placement of samples and duration of exposure of all samples of sucrose solution could be identical. A procedure was developed to relax the restriction of simultaneous field placement and exposure. Michigan, where conventional weather station data are available, was used to test the suitability of the sucrose inversion method for wide-area ecological use. The procedure presented uses daily maximum and minimum temperature data from a reference weather station, as well as the amount of sucrose inverted, to estimate the mean temperature in the study environment. When applied to 596 sites throughout Michigan, uncorrected sucrose inversion estimates gave nonsensical estimates of mean temperatures for the growing season of 1983. Estimates using as few as four reference weather stations plus the amount of sucrose inverted at each sample site gave results on the same order of accuracy as weather station data.
Electrophoretic variation in cross-compatible wild diploid species of Cucumis
Authors: Staub J. E. , Fredrick L. , Marty T. L.
Published: September 2008

Cotyledons of several collections of each taxon of Cucumis africanus Lindley f., C. anguria L. var. anguria, C. anguria var. longipes Meeuse, C. dipsaceus Ehrenb. ex Spach, C. metuliferus E. Mey ex Schrad., C. myriocarpus Naud., C. zeyheri Sond. (2x, 4x), and C. melo L. were surveyed using horizontal starch gel electrophoresis to characterize interspecific and intra-specific variation and to furnish preliminary phylogenetic information with regard to the cross-compatible group of wild African Cucumis species. Eight enzyme systems were studied: shikimate dehydrogenase, triose-phosphate isomerase, glutamic-pyruvic transaminase, glucose-phosphate isomerase, phosphogluconate dehydrogenase, isocitrate dehydrogenase, peptidase with phenylalanyl-L-proline, and phosphoglucomutase. All enzymes were polymorphic. Although C. anguria var. anguria accessions from Brazil and Ethiopia were similar, zymograms of C. anguria var. longipes were more similar to the C. melo collections. Results from var. anguria and var. longipes support previous data with regard to their varietal nature. The relative similarity among patterns of C. anguria var. longipes, C. metuliferus, and C. myriocarpus suggests a closer phylogenetic relationship than had previously been proposed. Isozyme similarities between C. anguria var. anguria, C. africanus, and C. dipsaceus suggest some phylogenetic affinities.
The effect of three osmotic agents on free proline and amino acid pools in Atriplex canescens and Hilaria jamesii
Authors: Cress William A. , Johnson Gordon V.
Published: September 2008

Three commonly used osmotic agents, mannitol, sucrose, and polyethylene glycol 4000, were used to simulate water stress in two arid region plant species, Hilaria jamesii (Torr.) Benth. and Atriplex canescens (Pursh) Nutt. Large amounts of mannitol (300–1400 μmol/g dry wt.) and sucrose (450–660 μmol/g dry wt.) were absorbed by both plant species, while insignificant amounts of polyethylene glycol 4000 were absorbed. During osmotic stress, Hilaria jamesii accumulated large quantities of proline, while A. canescens accumulated only a small amount. Shoot proline content of both species varied significantly with the osmotic agents used to simulate water stress. These results indicate that use of absorbable osmotic agents to simulate water stress may have important metabolic effects on the concentration of free proline and other metabolites.
A scanning electron microscopic study on the influence of temperature on the expression of cytoplasmic male sterility in Brassica napus
Authors: Polowick P. L. , Sawhney V. K.
Published: September 2008

The stamens of the ogu CMS line of B. napus L. exhibited different patterns of differentiation in response to temperature but were not fertile under any conditions. Three types of CMS stamens were recognized. Type 1 stamens had a distinct anther and filament and, in some cases, microspores were observed. These stamens were found most frequently under a high temperature regime (28:23 °C, light:dark). Type 2 stamens bore features of both stamens and carpels and were most common under intermediate temperature conditions (23:18 °C, light:dark). Type 3 stamens were carpelloid bearing a stigmatic surface and external ovules, lacked a filament, and were predominant under low temperature conditions (18:15 °C, light:dark). Normal stamens retained the same morphology under all temperature conditions. The sizes of the floral organs of normal and CMS flowers were also influenced by temperatures. Sepals, petals, and stamens were longer under low temperature conditions than intermediate and under intermediate temperature conditions than high temperature conditions. The floral organs of normal plants were generally larger than those of the CMS line.
Flow cytometric identification of Brassica napus protoplast fusion products
Authors: Pauls K. P. , Chuong P. V.
Published: September 2008

A flow cytometric method to identify Brassica somatic hybrids has been developed. The procedure is based on the use of fluorescein isothiocyanate stained hypocotyl protoplasts and unstained mesophyll protoplasts as partners for polyethylene glycol induced protoplast fusion. The fluorescein isothiocyanate stained hypocotyl protoplasts and unstained mesophyll protoplasts were passed through the flow cytometer – cell sorter separately to maximize the sensitivity of the red and green detectors to chlorophyll and fluorescein isothiocyanate fluorescence, respectively, and to ensure that there was no spillover of chlorophyll fluorescence into the green detector or fluorescein isothiocyanate fluorescence into the red detector. When adjusted properly, suspensions of a single protoplast type gave populations that fell on either the green or red axis of a two-dimensional green versus red fluorescence plot. With the same machine settings three populations of protoplasts could be identified in fusion mixtures of the two types of protoplasts: namely, the parental protoplasts that fell on the green or red axis as well as a third that had significant green and red fluorescence.
Seed germination of wild mustard (Sinapis arvensis): factors required to break primary dormancy
Authors: Goudey J. Stephen , Saini Hargurdeep S. , Spencer Mary S.
Published: September 2008

The regulatory actions of light, temperature, and various nitrogenous compounds on germination of dormant Sinapis arvensis L. seeds were examined to evaluate possible strategies for manipulating germination of soil-bome weed seeds. These treatments, when given singly, had little or no promotive effect on germination. However, KNO3 plus NH4Cl combined with irradiation and a change in temperature to 20 °C after 2 days of incubation at 5 °C induced over 90% germination. The effects of NH2OH∙HCl, KNO2, CS(NH2)2, KCN, and NaN3 were also significantly enhanced when given in combination with a brief exposure to red light and a temperature shift. However, these sources of nitrogen were less effective than KNO3 or NH4Cl in stimulating germination. The promotive effect of light, a temperature shift, and KNO3 and NH4Cl declined when the period of incubation at 5 °C was less than 2 days. This combined treatment was also less effective when the treatment with nitrogen or light was delayed beyond the first 48 h of incubation. Our results indicate that applications of nitrogen fertilizers in combination with surface tillage to expose the seed to light could promote germination of dormant S. arvensis seeds in the field.
Species patterns, edaphic characteristics, and plant water potential in a high-arctic brackish marsh
Authors: Dawson Todd E. , Bliss L. C.
Published: September 2008

Coastal brackish and salt marshes in the High Arctic are very limited floristically and in areal extent. Small marshes located on the northeast coast of Devon Island are dominated by distinct zones of Puccinellia phryganodes nearest the sea with Carex ursina, C. stans, Dupontia fisheri, and Alopecurus alpinus dominated zones landward. Soil salinity and chloride ion content increase seaward, but plant water potential becomes less negative, opposite to the expected pattern. Fresh water from the melting pack ice forms a lens over the more dense seawater below it. This meltwater dilutes the salts in the upper soil layer, creating a low salinity condition for the plants that inhabit the zones nearest the sea. We hypothesize that it is this "fresh" water that comes into contact with the roots of Puccinellia and Carex ursina, and thus, less-negative water potentials are maintained in these species. Although plant zonation can be explained in part by such considerations, we conclude that edaphic characteristics are not the only factors involved. A number of hypotheses are entertained.
Backscattered electron imaging as a tool for histochemically localizing calcium oxalate with the scanning electron microscope
Authors: Traquair J. A.
Published: September 2008

The scanning electron microscope and a backscattered electron detector were used for the first time to identify calcium oxalate in leaf tissues after labelling crystals with silver. Freehand sections fixed in formalin – acetic acid – alcohol or glutaraldehyde were treated with 5% acetic acid to remove background calcium carbonate and calcium phosphate and were silver stained by calcium-substitution techniques. Two standard staining techniques, Pizzolato (AgNO3–H2O2) and Yasue (AgNO3 – rubeanic acid) tests, were compared. Druses and raphides were identified morphologically and histochemically in the leaves of Anthurium scherzeranum and Dieffenbachia maculata. The Pizzolato procedure was the best method for staining calcium oxalate for scanning electron microscope studies. Excessive deposition of granular material in the Yasue staining method tended to obscure crystal morphology in scanning electron microscope preparations.
Effects of ozone and acid rain on white pine (Pinus strobus) seedlings grown in five soils. I. Net photosynthesis and growth
Authors: Reich Peter B. , Schoettle Anna W. , Stroo Hans F. , Troiano John , Amundson Robert G.
Published: September 2008

Four replicated factorial experiments were conducted to assess the response of potted white pine (Pinus strobus L.) seedlings to combined acid rain, ozone, and soil treatments. The objectives of the study were to quantify plant response to each pollutant alone and to determine whether the pollutants and edaphic factors interact in affecting physiological processes in white pine. In these studies, seedlings were grown in five forest soils and exposed for 4 months to realistic levels of acid rain and ozone. Acid rain treatments consisted of exposure to simulated rain of pH 5.6, 4.0, 3.5, or 3.0, while ozone treatments consisted of exposure to 0.02, 0.06, 0.10, or 0.14 ppm ozone. Minimal interaction between acid rain and ozone was observed with regard to photosynthesis or growth. Acid rain and soil type had a strong interaction in determining plant response. In general, acid rain caused increased growth and net photosynthesis as a result of nitrogen fertilization from the simulated rain. However, the extent of this response was inversely correlated with the availability of nitrogen in each soil. Ozone treatments caused decreased net photosynthesis in pine seedlings.
Diversity for virulence in a sexually reproducing population of Puccinia coronata
Authors: Al-Kherb S. M. , Roelfs A. P. , Groth J. V.
Published: September 2008

Diversity for virulence in a sexually reproducing population of Puccinia coronata Cda. was studied among isolates collected at three distances from a buckthorn hedge at six sampling periods during the summer. Among 360 isolates, 155 distinct phenotypes were identified on 28 differential oat cultivars. About 60% of the phenotypes were represented by a single isolate. The number of phenotypes found decreased with time and distance from the hedge. Host responses were classified into low (0 and 0;), intermediate (1 and 2), and high (3 and 4) infection type classes. The Shannon–Wiener index of diversity decreased with distance from the buckthorn hedge from 2.58 at the 1-m site to 1.35 at the 10-m site and decreased with time from 3.42 in the second to 2.71 in the sixth sampling period. The mean number of virulence differences among phenotypes in each collection ranged from 4 to 12 with 28 hosts. Both distance and time contributed significantly to the decrease in Shannon–Wiener index and number of phenotypes in multiple regression analyses.
Les inflorescences des Melastomataceae guyanaises, leur filiation et leur valeur taxonomique
Authors: Sell Yves , Cremers Georges
Published: September 2008

Analysis of the inflorescence structures of 188 species from French Guyana belonging to the Melastomataceae (Myrtales) confirms that the panicle (of flowers or cymes) is the inflorescence which, under the effect of a homogenization process, gives rise to the determinate raceme (a single raceme of flowers or of cymes, or more rarely, a double raceme), and later by truncation, the indeterminate raceme. The impoverishment of these flowering units can give rise to triads which correspond to uninodal racemes morphologically identical with dichasia (triflorous cymes), albeit of a different origin, since the cyme is considered as resulting from the enrichment of a flower and thus assimilated to the latter as a flowering unit. Extreme impoverishment of these uninodal racemes gives rise to a single flower. Melastomataceae have two peculiar features: successively developing pauciflorous groups and long proliferous shoots with short side shoots specifically for flowering. Within the framework of intrafamily classification, all these inflorescences, by virtue of their great diversity and the series of links between their structural variations, may constitute an essential basis for research on phylogenetic links between taxonomic groups.
The structure of the periplast components and their association with the plasma membrane in a cryptomonad flagellate
Authors: Wetherbee Richard , Hill David R. A. , Brett Steven J.
Published: September 2008

The periplast of Cryptomonas sp. θ covers most of the cell surface and is composed of the plasma membrane sandwiched between inner and surface periplast components. The surface periplast component is tightly appressed to the plasma membrane and consists of irregularly shaped plates composed of subunits organized into a crystalline array. Noncrystalline material distinguishes plate borders, and changes in plate size and (or) shape may result from the addition or subtraction of subunits at the borders. The inner periplast component is difficult to discern, but normally appears as a thin sheet of material appressed to the cytoplasmic surface of the plasma membrane. The inner periplast component is not closely associated with the plasma membrane at the positions corresponding to plate borders in the overlying surface periplast component. Both periplast components end at the entrance to the vestibulum, which together with the gullet is covered by a surface layer of heptagonal "rosette scales." The size and shape of the surface periplast plates, as well as the degree of association of the inner periplast sheet with the plasma membrane, are mirrored in the P and, to a lesser degree, E fracture faces of the plasma membrane. The presence of distinct membrane domains suggests the plasma membrane may be directly involved in the assembly and subsequent development of the periplast layers.
Ascus and crozier development in the Balansiae
Authors: Jones John P. , Clay Keith
Published: September 2008

The morphological development of the croziers and asci of four species of the Balansiae were examined and compared with other members of the order Clavicipitales to evaluate the potential usefulness of these developmental sequences as a taxonomic criterion at the family or subfamily level. Balansia epichloë, B. henningsiana, and Atkinsonella hypoxylon were very similar in all details of development. Myriogenospora atramentosa does differ in some characteristics, but is included in the single family Clavicipitaceae with the other species examined. Division of the order beyond the single family Clavicipitaceae is not supported by our data.
Distributions and fates of oxygen in periphyton communities
Authors: Carlton Richard G. , Wetzel Robert G.
Published: September 2008

Direct measurements with oxygen microelectrodes demonstrated that the distribution of dissolved oxygen in periphyton communities varied on a diurnal basis and was markedly different among periphyton types. During illumination, photosynthesis in periphyton resulted in oxygen supersaturation in microzones that were subsaturated or anoxic during darkness. The fate of oxygen produced within periphyton depended on the relative rates of production and consumption, the diffusion characteristics of the periphyton, physical and chemical interactions with the substratum, and the transport rate across the boundary layer, which was affected significantly by water currents. During constant environmental conditions, steady-state oxygen distributions occurred within periphyton, but equilibrium with the surrounding water was rare.
Revision of the Aster lanceolatus complex, including A. simplex and A. hesperius (Compositae: Astereae): a multivariate morphometric study
Authors: Semple John C. , Chmielewski Jerry G.
Published: September 2008

The complex is treated as a single species, Aster lanceolatus, on the basis of fieldwork, garden studies, herbarium work, and multivariate analyses of morphological variation of reproductive structures among 200 representative specimens. Two subspecies are recognized: ssp. hesperius occurring in western North America and ssp. lanceolatus occurring in central and eastern North America. Subspecies lanceolatus is further divided into four varieties: var. hirsuticaulis, var. interior, var. lanceolatus (including A. simplex), and var. latifolius. The typical variety is the most diverse and is considered to include forms most like the ancestor of the species. A key to the five infraspecific taxa is presented along with full synonymy. The following new names and combinations are proposed: Aster lanceolatus ssp. hesperius, A. lanceolatus ssp. lanceolatus var. hirsuticaulis, A. lanceolatus ssp. lanceolatus var. interior, and A. lanceolatus ssp. lanceolatus var. latifolius.
Optimum growth temperature for Pilobolus
Authors: Foos K. Michael , Royer Judith
Published: September 2008

Optimum growth temperatures for Pilobolus have not been reported. This study of eight isolates of Pilobolus indicates that these fungi grow actively in a range of temperatures between 10 and 40 °C and that the optimum commonly lies between 25 and 35 °C.
Morphological and leaf anatomical variation in Festuca rubra sensu lato (Poaceae) from eastern Quebec
Authors: Dubé Martin , Morisset Pierre
Published: September 2008

The variation of 52 morphological and anatomical characters was analysed in 32 populations of Festuca rubra L. sensu lato from salt marshes, coastal rocks, coastal sands, and anthropogenic sites in eastern Quebec. The results show that the variation of characters is essentially continuous within and between populations, that some populations are much more variable than others, and that on the whole, character variation patterns are mainly related to ecological rather than geographical factors. The weak structure revealed by a similarity analysis of populations is the source of the classification problems within this species.