bluuebunny/crossref_metadata_2025 huggingface dataset:
Cryptic population genetic structure: the number of inferred clusters depends on sample size
Authors: FOGELQVIST JOHAN , NIITTYVUOPIO ANNE , ÅGREN JON , SAVOLAINEN OUTI , LASCOUX MARTIN
Published: August 2009

Clustering methods have been used extensively to unravel cryptic population genetic structure. We investigated the effect of the number of individuals sampled in each location on the resulting number of clusters. Our study was motivated by recent results in Arabidopsis thaliana: studies in which more than one individual was sampled per location apparently have led to a much higher number of clusters than studies where only one individual was sampled in each location, as is generally done in this species. We show, using computer simulations and microsatellite data in A. thaliana, that the number of sampled individuals indeed has a strong impact on the number of resulting clusters. This effect is smaller if the sampled populations have a hierarchical structure. In most cases, sampling 5–10 individuals per population should be enough. The results argue for abandoning the concept of ‘accessions’ in partially selfing organisms.
Significant improvements in near vision, reading speed, central visual field and related quality of life after ranibizumab treatment of wet age‐related macular degeneration
Authors: Frennesson Christina , Nilsson Ulla L. , Peebo Beatrice B. , Nilsson Sven E. G.
Published: August 2009

Purpose:  To investigate the effects on near visual acuity, reading speed, central visual field and related quality of life of ranibizumab treatment of wet age‐related macular degeneration (AMD).

Methods:  The study was a prospective, non‐comparative consecutive case series, followed for 3 months and investigator‐driven. Thirty eyes of 30 patients with wet AMD were included, mean age 75 years (range 69–95 years). In addition to a full ophthalmological examination – including best‐corrected visual acuity (BCVA; Early Treatment Diabetic Research Study chart), fundus biomicroscopy, fundus photography, fluorescein angiography, indocyanine green angiography (occult cases) and ocular coherence tomography – near visual acuity, reading speed, central visual field and quality of life for related activities were also investigated at baseline and at 3 months after ranibizumab treatment.

Results:  Mean BCVA increased from 62 ± 11 to 66 ± 14 letters at 3 months (7%; p = 0.018). Near vision improved from 9 ± 5 to 6 ± 3 points (33%; p = 0.0006) and reading speed increased from 59 ± 40 to 85 ± 50 words/min (44%; p < 0.0001). The mean deviation from normal of the visual field improved from −9 ± 7 to −6 ± 5 dB (33%; p < 0.0001). Quality of life improved for distance activities from 54 ± 28 to 63 ± 28 points (17%; p < 0.0001) but significantly (p = 0.024) more for near activities, from 49 ± 26 to 63 ± 26 points (29%; p < 0.0001). Reading newspaper text in the group in which the better eye was treated showed the highest increase in quality of life score of all: 116%.

Conclusion:  The increase in BCVA after ranibizumab treatment is well established. The present study also showed significant improvements in other important visual qualities, such as near visual acuity, reading speed, central visual field and several activities influencing quality of life. The improvement was greater for near activities than for distance activities. Therefore, the beneficial effects of ranibizumab treatment shown here are more extensive than those reported previously.
Combination Chemotherapy with Continuousl‐Asparaginase, Lomustine, and Prednisone for Relapsed Canine Lymphoma
Authors: Saba C.F. , Hafeman S.D. , Vail D.M. , Thamm D.H.
Published: August 2009

Background:The combination of lomustine,l‐asparaginase, and prednisone (LAP) is an effective rescue treatment for canine lymphoma (LSA). In a previous study, we reported that remission was typically lost around the timel‐asparaginase was discontinued.

Hypothesis:Use ofl‐asparaginase with each lomustine treatment will be well tolerated and efficacious as a rescue therapy for canine LSA.

Animals:Forty‐eight client‐owned dogs with cytologically confirmed multicentric LSA whose disease had relapsed after a cyclophosphamide, doxorubicin, vincristine, and prednisone‐based chemotherapy protocol were included.

Methods:Lomustine was administered orally at 3‐week intervals, concurrently with subcutaneous or intramuscularl‐asparaginase for a total of 5 doses or until disease progression. Prednisone was administered at a tapering dose for the duration of the protocol.

Results:The overall response rate (ORR) for dogs treated with this protocol was 77%, with 65% achieving a complete response (CR). The median time to progression (TTP) was 70 days. Based on loose comparison, these findings are not significantly different from our previously reported historical control. The actual CCNU dosage administered did not affect response rate or remission duration.

Conclusions/Clinical Importance:These findings support previous data concluding that the LAP protocol is a viable rescue treatment option for dogs with LSA. However, results from this study suggest that continued use ofl‐asparaginase with each lomustine treatment does not significantly increase remission duration and toxicity appears greater.
Remission of Histiocytic Ulcerative Colitis in Boxer Dogs Correlates with Eradication of Invasive Intramucosal Escherichia coli
Authors: Mansfield C.S. , James F.E. , Craven M. , Davies D.R. , O'Hara A.J. , Nicholls P.K. , Dogan B. , MacDonough S.P. , Simpson K.W.
Published: August 2009

Background: Historically, histiocytic ulcerative (HUC) (or granulomatous) colitis of Boxer dogs was considered an idiopathic immune‐mediated disease with a poor prognosis. Recent reports of dramatic responses to enrofloxacin and the discovery of invasive Escherichia coli within the colonic mucosa of affected Boxer dogs support an infectious etiology.

Hypothesis: Invasive E. coli is associated with colonic inflammation in Boxer dogs with HUC, and eradication of intramucosal E. coli correlates with clinical and histologic remission.

Animals: Seven Boxer dogs with HUC.

Methods: Prospective case series. Colonic biopsies were obtained at initial evaluation in 7 dogs, and in 5 dogs after treatment with enrofloxacin. Biopsies were evaluated by standardized histopathology, and fluorescence in situ hybridization (FISH) with probes to eubacteria and E. coli.

Results: Intramucosal E. coli was present in colonic biopsies of 7/7 Boxers with HUC. Clinical response was noted in all dogs within 2 weeks of enrofloxacin (7±3.06 mg/kg q24 h, for 9.5±3.98 weeks) and was sustained in 6 dogs (median disease‐free interval to date of 47 months, range 17–62). FISH was negative for E. coli in 4/5 dogs after enrofloxacin. E. coli resistant to enrofloxacin were present in the FISH‐positive dog that relapsed.

Conclusions and Clinical Relevance: The correlation between clinical remission and the eradication of mucosally invasive E. coli during treatment with enrofloxacin supports the causal involvement of E. coli in the development of HUC in susceptible Boxer dogs. A poor response to enrofloxacin treatment might be due to colonization with enrofloxacin‐resistant E. coli.
Transcatheter Atrial Septal Defect Closure with the AMPLATZER® Atrial Septal Occluder in 13 Dogs: Short‐ and Mid‐Term Outcome
Authors: Gordon S.G. , Miller M.W. , Roland R.M. , Saunders A.B. , Achen S.E. , Drourr L.T. , Nelson D.A.
Published: August 2009

Background: Transcatheter atrial septal defect (ASD) closure in the dog was first reported in 2005.

Objectives: Describe the technique and both short‐ and mid‐term outcome of transcatheter ASD closure with the Amplatzer® atrial septal occluder (ASO).

Animals: Thirteen client‐owned dogs with ASD.

Methods: Records of the initial 13 dogs in which transcatheter ASD closure was attempted at Texas A&M University were reviewed.

Results: All dogs had hemodynamically relevant septum secundum ASD. Two dogs had concurrent congenital abnormalities. ASOs were deployed in 13 dogs and released in 12. Eleven were released by a right jugular approach and 1 by a transatrial approach through a right lateral thoracotomy. Transthoracic echocardiographic estimates of ASD size were 14.0 ± 5.4 mm (mean ± 1 standard deviation) with a range of 7–22 mm. Accidental right atrial release occurred in 1 dog and embolization after release occurred in 2 dogs. Transcatheter ASD closure was successful in 10 dogs. Transthoracic color Doppler echocardiography the day after ASD closure indicated complete occlusion in 5 dogs, trivial to mild residual shunting in 4 dogs, and moderate residual shunting in 1 dog. Follow‐up echocardiograms (mean of 12.4 ± 7.4 months postprocedure) were available for 9 dogs. There was no residual ASD shunting in 6 dogs. In 3 of the 5 dogs with postoperative residual shunting it was judged to be decreased and hemodynamically unimportant relative to the dogs' postoperative evaluations. The mean length of event‐free survival in the 10 dogs that underwent successful transcatheter ASD closure was 22.2 ± 10.2 months.
Temporal Variability of Ventricular Arrhythmias in Boxer Dogs with Arrhythmogenic Right Ventricular Cardiomyopathy
Authors: Scansen B.A. , Meurs K.M. , Spier A.W. , Koplitz S. , Baumwart R.D.
Published: August 2009

Background: Arrhythmogenic right ventricular cardiomyopathy (ARVC) is prevalent in the Boxer. There is little information on the temporal variability of ventricular arrhythmias within affected dogs.

Objective: To evaluate ambulatory electrocardiograms (AECG) from Boxers with ARVC for hourly variation in premature ventricular complexes (PVC) and heart rate (HR).

Animals: One hundred and sixty‐two Boxer dogs with ARVC.

Methods: Retrospective, observational study of 1,181 AECGs collected from Boxer dogs at The Ohio State University from 1997 to 2004 was evaluated. The proportion of depolarizations that were PVCs was compared across each hour of the day, during six 4‐hour periods of day, to the time after AECG application, and to the maximum and minimum HR.

Results: A lower proportion of PVCs was noted during early morning (midnight to 0400 hours) as compared with the morning (0800–1200 hours) and late (1600–2000 hours) afternoon (P= .012). There was no increase in PVC proportion in the 1st hour after AECG application as compared with all other hours of the day (P= .06). There was poor correlation between maximum (ρ= 0.19) and minimum (ρ= 0.12) HR and PVC proportion.

Conclusions and Clinical Importance: The likelihood of PVC occurrence in Boxer dogs with ARVC was relatively constant throughout the day, although slightly greater during the hours of 0800–1200 and 1600–2000. A biologically important correlation with HR was not apparent. The role of autonomic activity in the modulation of electrical instability in the Boxer with ARVC requires further study.
Effect of Transvenous Electrical Cardioversion on Plasma Cardiac Troponin I Concentrations in Horses with Atrial Fibrillation
Authors: Jesty S.A. , Kraus M. , Gelzer A. , Rishniw M. , Moïse N.S.
Published: August 2009

Background:Whether electrical cardioversion of cardiac arrhythmias results in cardiomyocyte damage is unknown.

Objective:To describe effect of transvenous electrical cardioversion (TVEC) on plasma cardiac troponin I (cTnI) concentration in horses.

Animals:All horses presented to the Cornell University Hospital for Animals for cardioversion of atrial fibrillation between May 2006 and October 2008 were eligible for inclusion in the study. Owners of 14 horses elected for TVEC and each horse was then enrolled (16 procedures).

Methods:Prospective observational study measuring concentrations of plasma cTnI before and after TVEC.

Results:Median cTnI concentration increased from 0.045 ng/mL at baseline (range 0.0–0.20 ng/mL) to 0.11 ng/mL after TVEC (range 0.0–3.73 ng/mL) (P= .036). This increase was not associated with the number of shocks delivered, maximal energy delivered, cumulative energy delivered, chronicity of atrial fibrillation before cardioversion, or positioning of the pulmonary artery catheter.

Conclusions:The increase in cTnI is unlikely to be clinically important. The increase might be correlated with persistent atrial dysfunction after TVEC, suggesting that a longer convalescent period after the procedure could be warranted.
Effect of Experimental Hypothyroidism on Glomerular Filtration Rate and Plasma Creatinine Concentration in Dogs
Authors: Panciera D.L. , Lefebvre H.P.
Published: August 2009

Background:Hypothyroidism affects renal function in a manner opposite the effects of hyperthyroidism.

Objective:To evaluate the effects of experimentally induced hypothyroidism on glomerular filtration rate (GFR) and basal plasma creatinine concentration in dogs.

Animals:Sixteen anestrous, female dogs.

Methods:Hypothyroidism was induced by administration of131I in 8 dogs, and 8 healthy euthyroid dogs acted as controls. Exogenous plasma creatinine clearance (an estimate of GFR) was measured in all dogs before (control period) and 43–50 weeks after induction of hypothyroidism (posttreatment period). Other pharmacokinetic parameters of creatinine were also determined.

Results:No significant difference was observed for basal plasma creatinine concentration and creatinine clearance between control and hypothyroid dogs in the control period. In the posttreatment period, mean ± SD creatinine clearance in the hypothyroid group (2.13 ± 0.48 mL/min/kg) was lower (P< .001) than that of the control group (3.20 ± 0.42 mL/kg/min). Nevertheless, basal plasma creatinine concentrations were not significantly different between the hypothyroid and control groups (0.74 ± 0.18 versus 0.70 ± 0.08 mg/dL, respectively) because endogenous production of creatinine was decreased in hypothyroid dogs (22 ± 3 versus 32 ± 5 mg/kg/d,P=.001).

Conclusion and Clinical Importance:Hypothyroidism causes a substantial decrease in GFR without altering plasma creatinine concentrations, indicating that GFR evaluation is needed to identify renal dysfunction in such patients.
Paleomyrtinaea, a new genus of permineralized myrtaceous fruits and seeds from the Eocene of British Columbia and Paleocene of North Dakota
Authors: Pigg Kathleen B. , Stockey Ruth A. , Maxwell Suzette L.
Published: August 2009

Paleomyrtinaea princetonensis gen. et sp.nov. Pigg, Stockey & Maxwell is described from the Middle Eocene Princeton Chert of British Columbia, Canada. Anatomically preserved fruits are berries up to 1.6 × 0.78 cm with a fleshy fruit wall that consists of a three-layered pericarp. The exocarp is composed of a uniseriate epidermis of tabular cells and an outer hypodermis of small cells and the mesocarp is aerenchymatous. Some seeds are invested in a pulpy endocarp. The seeds are campylotropous, 1.8 mm long and 1.6 mm wide, and contain a curved embryo cavity about 1.5 mm long and 0.64 mm wide. Four distinct integumentary zones can be recognized, an outermost zone two to three cells thick of tangentially elongate cells, a second zone, constituting the bulk of the integument, of small, isodiametric cells, a third zone of uniseriate, columnar cells that extends into the germination valve, and an innermost zone of five to six layers of tangentially elongate cells. The genus is also represented by fruits and seeds from the Upper Paleocene Sentinel Butte Formation, Almont, North Dakota. Affinities of these fruits are with the berrylike guavas of the Myrtaceae, tribe Myrteae, subtribe Myrtinae, and in particular, with the closely related genera Mosiera Small and Psidium L. A brief review of the fossil record of the Myrtaceae is also presented. Key words: Myrtales, Myrtaceae, Tertiary, permineralization, fruit, seed.
Genetic diversity in Aspergillus flavus: association with aflatoxin production and morphology
Authors: Bayman Paul , Cotty Peter J.
Published: August 2009

Isolates of Aspergillus flavus belonging to at least 12 vegetative compatibility groups were characterized by aflatoxin production in vitro, morphology, and random amplified polymorphic DNAs. Aflatoxin B1 production differed significantly among vegetative compatibility groups; closely related isolates were similar intoxigenicity regardless of geographic origin. Cladistic analysis of DNA polymorphisms was consistent with vegetative compatibility data. A previously described dichotomy between S and L isolates of A. flavus based on morphology and physiology was strongly associated with both vegetative compatibility groups and DNA polymorphisms. All S isolates formed a single clade, apparently derived from the L group. Southern hybridizations of eight DNA amplification products showed that comigrating bands amplified by the same primer were always homologous within A. flavus but were not always homologous between A. flavus and closely related species. Results suggest that A. flavus is a species aggregate, that genotypes are dispersed over wide areas, and that aflatoxin production is more stable in nature than in culture. Key words: vegetative compatibility groups, random amplified polymorphic DNA, sclerotia, aflatoxin.
Ultrastructure of the vascular responses of cotton to Verticillium dahliae
Authors: Mueller W. C. , Morgham A. T.
Published: August 2009

Ultrastructural examination of cotton plants infected with Verticillium dahliae showed responses in the vascular tissue similar to those reported earlier in cotton infected with Fusarium oxysporum f.sp. vasinfectum. Contact cells reacted vigorously to infection, but the nature of the response depended on the location of the cells. The majority of the contact cells adjacent to initially infected vessels showed a reorganization of the cytoplasm with the formation of an apposition layer, a partitioning of the central vacuole into smaller vacuoles, and the appearance of osmiophilic material that was secreted through the plasmalemma and deposited in the apposition layer and in the pit regions of the vessels. The remainder of the contact cells adjacent to initially infected vessels contained a degenerated cytoplasm but no fungal hyphae. Contact cells adjacent to secondarily infected vessels responded with increased cytoplasmic activity and the direct secretion of osmiophilic material into the vessel lumens where it accumulated to form aggregates of various sizes and shapes that occluded the vessels. The fungus in these vessels was coated and embedded in this secreted material. Key words: contact cells, Gossypium hirsutum, Gossypium barbadense, vascular wilt, vessel occlusion.
A lack of heterosis in natural poplar hybrids from southern Alberta
Authors: Campbell John S. , Mahoney John M. , Rood Stewart B.
Published: August 2009

Shoot cuttings were collected from 56 native poplars along 11 rivers and creeks in southwestern Alberta, a region where Populus angustifolia, Populus balsamifera (sspp. balsamifera and trichocarpa), and Populus deltoïdes form a disectional, trispecific hybrid swarm. Cuttings were rooted and established in an irrigated nursery plot. After 3 years, stem diameters and heights were measured from 381 trees and whole shoots were harvested from 74 trees to establish a regression equation relating basal diameter and shoot wet weight. Shoot wet weight varied by more than an order of magnitude across the clones, and P. angustifolia clones tended to grow more slowly than clones of the other two species. There was no significant correlation between shoot growth rate and the degree of hybridization, as determined by a prior multivariate analysis of leaf form that has been substantiated by chemotaxonomic data. Thus, the interspecific hybrids were not generally more vigorous than clones with leaf forms typical of the parental species P. deltoides or P. balsamifera. Conversely, in the same environment, artificial hybrids of P. deltoides from Illinois and P. balsamifera (ssp. trichocarpa) from Washington expressed heterosis. It is theorized that introgressive genetic exchange accompanying the natural interbreeding of these three poplar species in southern Alberta minimizes their genetic distance, preventing heterosis. Key words: heterosis, hybridization, poplars, Populus, biomass.
Phenotypic variation in cone and needle characters of Pinus banksiana (jack pine) in northwestern Ontario
Authors: Maley Madeline L. , Parker William H.
Published: August 2009

To investigate the pattern of natural variation of jack pine (Pinus banksiana Lamb.), 64 natural stands from northwestern Ontario were compared based on phenotypic variation of cone and needle morphology. Cone and needle traits were determined for 10 trees from each stand. Vegetation and soil data for the stands were determined following the procedures established by the Ontario Ministry of Natural Resources Forest Ecosystem Classification program. Climatic data for each stand were interpolated using a geographic information system based on 1951 to 1980 data for Ontario and Minnesota weather stations. Nested analyses of variance indicated that most of the variation was expressed between trees and within trees, with relatively little (1.6 – 18.9% depending on the trait) expressed between sampled populations. Discriminant analysis of cone and needle data indicated that the 64 populations generally varied longitudinally with a steep cline in the Nipigon area (ca. 88°15′W) apparent for cone data. A corresponding irregularity in the pattern of needle variation suggested that the modern pattern may be the result of separate lineages, i.e., descendents from two migration routes along eastern and western shores of Lake Superior or from two refugia. However, temperature data follows a similar pattern in this area of Ontario, and multiple regression of the discriminant analysis score means for the 64 sampled populations against elevation, climatic, and soil data indicated that much of the cone and needle variation expressed between populations could be accounted for by the regressions. Thus, the observed patterns of phenotypic variation may simply be the result of local adaptations to a variable environment. Key words: jack pine, Pinus banksiana, phenotypic variation, cone traits, needle traits, northwestern Ontario.
On the subdivision of Ceratocystis s.l., based on partial ribosomal DNA sequences
Authors: Hausner G. , Reid J. , Klassen G. R.
Published: August 2009

Analyses of partial rDNA sequences from both the small and large subunit genes of species of Ceratocystis s.l. support the contention that species that lack Chalara anamorphs, are resistant to cycloheximide, and have rhamnose in their cell walls should be assigned to Ophiostoma, whereas only species with Chalara anamorphs should be accommodated in Ceratocystis s.s. The data also show that Ceratocystiopsis is polyphyletic, and Sphaeronaemella fimicola appears to have little relation to either Ceratocystis or Ophiostoma. Key words: Ceratocystis, Ophiostoma, phylogeny, partial rDNA sequences.
The effect of environmental conditions on the annual dormancy pattern of seeds of Spergula arvensis
Authors: Bouwmeester Harro J. , Karssen Cees M.
Published: August 2009

The effect of environmental factors on the germination of exhumed seeds of Spergula arvensis L. after variable periods of burial in soil was investigated. Seeds were buried in the field and exhumed at regular intervals after which germination was tested over a range of conditions. These tests showed clear seasonal changes in dormancy during 3 successive years. Dormancy was broken in spring and reinduced in autumn at rising and falling temperatures, respectively. In experiments in incubators, greater loss of dormancy occurred at 10 and 15 °C than at 2 and 6 °C. As in the field, induction of dormancy occurred when the preincubation temperature was lowered. The expression of the dormancy pattern was strongly influenced by the germination tests conditions. At 15 °C, seeds germinated during a longer period of the year than at 2 or 30 °C. Irradiation with red light, addition of nitrate, and desiccation of the seeds prior to the germination test strongly stimulated germination. All three factors enabled germination of exhumed seeds during a longer period of the year. When light, nitrate, and desiccation were combined, exhumed seeds could germinate in all seasons. The seasonal germination pattern was modelled with a descriptive model based on the dual effect of temperature, which regulates dormancy and also affects germination. This model closely simulated germination at field temperatures. Germination of exhumed seeds in the field was restricted to the period of overlap between the germination temperature range computed with the model and field temperature. The features of the model supported the hypothesis that dormancy of S. arvensis is regulated by the actual changes in temperature rather than the combined effects of a cold and heat sum. Key words: Spergula arvensis, dormancy pattern, germination, regression model, weed seeds.
Floral development of Rosa setigera
Authors: Kemp James R. , Posluszny Usher , Gerrath Jean M. , Kevan Peter G.
Published: August 2009

The development of the flower of Rosa setigera from initiation to the onset of anthesis is described. Rosa setigera is the only known member of the genus Rosa to exhibit dioecy. Flowers of functionally staminate (male) and functionally carpellate (female) plants appear identical, a condition referred to as cryptic dioecy. Discrete sepals and petals are formed on the floral meristem. As the hypanthium forms, stamens are initiated in alternating whorls on the wall of the hypanthium and continue to develop as the hypanthium extends. Carpel primordia arise individually on the remainder of the floral meristem and show neither adnation to the hypanthial wall nor coalescence to one another as they give rise to the styles and stigmas that are exserted above the hypanthium lip. The only observable fusion in this species appears to be the postgenital fusion of the margins of the carpel primordia to form the enclosed locule. Although historically the hypanthium has been variously interpreted as either axial and (or) appendicular in nature, resulting from congenital fusion of sepals, petals, and stamens, this paper uses a more realistic, testable and functional approach to the development of the hypanthium that is in keeping with current concepts such as process morphology. Key words: Rosa setigera, dioecy, floral development, fusion, hypanthium.
Utilization of induction and quenching kinetics of chlorophyll a fluorescence for in vivo salinity screening studies in wheat (Triticum aestivum vars. Kharchia-65 and Fielder)
Authors: KrishnaRaj Sankaran , Mawson Bruce T. , Yeung Edward C. , Thorpe Trevor A.
Published: August 2009

The potential of utilizing induction and quenching kinetics of chlorophyll a fluorescence as consistent and reliable markers for in vivo salt (sodium sulphate) tolerance screening studies was investigated by comparing two wheat (Triticum aestivum L.) varieties with varying responses to salinity, viz. Kharchia-65 (salt-tolerant) and Fielder (salt-susceptible). Three-week-old seedlings were treated with a range of salt concentrations (0 to 2%) over a 1- to 2-week period. Both the maximum rates of fluorescence induction and quenching measured from leaf sections decreased significantly in Fielder compared with Kharchia-65 as the salt concentration increased. Alterations in other fluorescence parameters, such as the maximum yield of fluorescence signal in the absence and presence of 3(3,4-dichlorophenyl)-1,1-dimethylurea by the variety Fielder indicated a minimal reduction in the size of the primary electron acceptor pool associated with photosystem II following salt stress. In contrast, these parameters were altered to a lesser extent by salt treatments in Kharchia-65. The effect of salinity stress on leaf morphology of both varieties indicated no major anatomical alterations apart from a negligible increase in leaf thickness. Total chlorophyll content of Kharchia-65 increased significantly as a result of salt stress, owing to an increase in both chlorophyll a and chlorophyll b, whereas Fielder showed no significant variations. The results indicate that total fluorescence quenching and maximum rates of both induction and quenching appear to be reliable indicators for in vivo screening of salt-tolerant wheat genotypes. Key words: Triticum aestivum L., wheat, chlorophyll a fluorescence, salt stress, in vivo screening.
Intersterility groups in the Pleurotus ostreatus complex from the continental United States and adjacent Canada
Authors: Vilgalys Rytas , Smith Ajiri , Sun Bao Lin , Miller Jr. Orson K.
Published: August 2009

Mating compatibility studies using strains from 170 North American collections in the Pleurotus ostreatus complex reveal three intersterile species of oyster mushrooms in the United States and Canada. Initial pairings among monokaryotic single spore isolates were performed to determine the number of intersterile groups. Dikaryon – monokaryon pairings using monokaryotic tester strains were then used to screen additional dikaryotic cultures of the oyster mushroom. Pairings of tester strains from Europe indicate that two European taxa, P. ostreatus and Pleurotus pulmonarius, are also widely distributed in North America. A third intersterility group occurring primarily on aspen in North America was intersterile with all other known species, and is described as a new species, Pleurotus populinus. All three species differ from one another in their morphology, growth characteristics, geographic distributions, and host ranges. Other than mating compatibility tests, however, no single type of character was found to be completely reliable for distinguishing these species in the field or under laboratory conditions. Furthermore, morphological characters used to distinguish European species of the P. ostreatus complex were not useful when applied to corresponding mating-compatible groups from North America. Key words: oyster mushroom, species concept, mating incompatibility.
Comparative foliage and twig chemistry of co-occurring Myrica gale and Chamaedaphne calyculata
Authors: Mackun I. R. , McNaughton S. J. , Raynal D. J. , Leopold D. J.
Published: August 2009

The deciduous N-fixing shrub Myrica gale L. and the evergreen sclerophyllous shrub Chamaedaphne calyculata (L.) Moench sometimes intermingle in small patches in boreal peatlands. The mineral element composition of adjacent plants and plant parts may differ owing to the distinctive morphology and physiology of each species. We compared the elemental composition and allocation patterns of Myrica and Chamaedaphne co-occurring in 1-m2 plots in a western Adirondack peatland. Current foliage and twigs of each species were analyzed for Al, B, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Mo, Na, Ni, P, Pb, Se, V, and Zn. Fourteen elements differed significantly among tissues. Chamaedaphne foliage was highest in Al, Mn, and P, and Chamaedaphne twigs were highest in Cu, whereas Myrica foliage was highest in K and Ni, and Myrica twigs were highest in Mo and Zn. Elemental differences were interpreted with respect to possible physiological roles in each species. Additionally, a multivariate discriminant function analysis yielded two canonical variables: (i) a structural – functional component correlated with Al, B, Ca, Cu, Fe, and K that distinguished Myrica from Chamaedaphne, and (ii) a metabolic component correlated with Al, B, Mo, P, and Zn that separated foliage from twigs. Key words: peatland, sclerophylly, nitrogen fixer, tissue chemistry, Chamaedaphne calyculata, Myrica gale.
Development of a resistance test for winter rye to snow mold (Microdochium nivale) under controlled environment conditions in regard to field inoculations
Authors: Miedaner T. , Höxter Henriette , Geiger H. H.
Published: August 2009

Twenty-one winter rye inbred lines (Secale cereale) were tested for resistance to Microdochium nivale under artificial inoculation conditions in a 2-year field experiment. Significant genotypic variation was found for snow mold rating, plant loss rating, number of spikes, and grain yield relative to the noninoculated plants. Heritability was highest for snow mold rating (h2 = 0.79). The inbred lines showed a continuous distribution of all characters assessed for both years. Genotype × year interactions were significant for most traits. A reproducible growth chamber test for the evaluation of inbred lines with snow mold was developed. Best results were obtained under the following conditions: (i) hardening of plants by cultivation at low temperatures prior to inoculation, (ii) inoculation at plant growth stage of advanced tillering, (iii) use of actively growing mycelium from shaken liquid culture as inoculum, (iv) cold incubation at a temperature of 1 °C for inoculated plants, and (v) plant recovery period after incubation for at least 1 week in the greenhouse. The length of the cold incubation period of inbred lines at 1 °C was only 11 days due to an incubation of fungal mycelium prior to inoculation and a 2-day incubation of the inoculated plants at 13 °C and 100% relative humidity. For assessing the optimal length of the cold incubation period, the optimal character for disease assessment, the significance of plant recovery after cold incubation, and the correlation to field results, a recently developed species specific enzyme-linked immunosorbent assay (ELISA) was used. A significant correlation between the growth chamber test and the 2-year field trial was found with 19 inbred lines for snow mold rating (0.51 < r < 0.57). The correlation could be improved by using the ELISA (0.69 < r < 0.80) to evaluate disease intensity. Key words: Secale cereale, quantitative resistance, growth chamber test, enzyme-linked immunosorbant assay.
Phenotypic plasticity and genetic variability in annual Zizania spp. along a latitudinal gradient
Authors: Counts Rebecca L.
Published: August 2009

Bulk seed collections were made from six populations of Zizania spp. (two Z. palustris and four Z. aquatica) along the Atlantic seaboard from northern New Brunswick, Canada, to southern Georgia, U.S.A. Ten plants per population were cultivated in each of two greenhouse chambers differing in temperature, and 20 – 80 seedlings from each population were assayed for 14 isozyme loci. Mean values for a suite of phenological and morphometric traits showed clinal variation in association with the latitudinal gradient. Magnitudes and patterns of plasticity for the same traits did not show clinal variation in response to varying temperature regimes but were different in the two species. Plants from Z. palustris populations responded to elevated temperatures by delaying flowering, increasing stem size, and decreasing proportional reproductive effort; Z. aquatica populations were generally much less sensitive to the temperature differential, but where responses were observed they were typically opposite to those described for Z. palustris. The species were also differentiated by allelic composition of the populations. There was no systematic relationship between degree of heterozygosity at isozyme loci and magnitudes of plasticity for morphometric traits. There was no evidence for the coordinated divergence of Zizania populations for trait means and magnitudes and patterns of plasticity. It is suggested that ecological differences, possibly characteristic differences in intensity and consistency of competitive pressure, may account for the contrasting patterns of plasticity in Z. palustris and Z. aquatica. Key words: Zizania, phenotypic plasticity, latitude, genetic variability.
Ecology of a forest weed of Newfoundland: vegetative regeneration strategy of Kalmia angustifolia
Authors: Mallik A. U.
Published: August 2009

The vegetative regeneration characteristics of Kalmia angustifolia were studied by examining the near ground and below-ground structures of the plant. Three methods of vegetative regeneration were observed in Kalmia: layering, stem-base sprouting, and rhizomatous growth, which make the plant more resilient than other ericaceous plants of similar stature following disturbance. Layering occurred only in tall old Kalmia of undisturbed habitats. Stem-base sprouting and rhizomatous growth were found to be the most common and most effective modes of vegetative regeneration. These methods were common in both disturbed and undisturbed habitats. Three types of rhizome systems, namely primary, secondary, and tertiary rhizomes, were identified and described for the first time in Kalmia. Secondary rhizomes were found to be the most effective organ for vegetative spread of the plant. Some secondary rhizomes may grow more than 1 m in one growing season. A 5-year-old Kalmia may produce, on average, 36 secondary rhizomes with a total length of 750 cm. Secondary rhizomes of Kalmia first grow horizontally, then come aboveground growing vertically and exhibiting apical dominance. Large numbers of dormant vegetative buds (three at each node) and adventitious roots are produced at the rhizome nodes. Transverse sections of current-year rhizome showed many trichomes. The cells of the pith are thick-walled and are characterized by large lysigenous cavities. The anatomy of axillary buds and leaf primordia of the aboveground stems of Kalmia were similar to buds and bud scales of the rhizome. Key words: Kalmia, disturbance, fire, regeneration strategy, rhizome, trichomes.
Species and site differences in the decomposition of litters and roots from wet heathlands
Authors: Vuuren M. M. I. Van , Berendse F. , Visser W. De
Published: August 2009

The decomposition of litter and roots from a site dominated by Erica tetralix and a site dominated by Molinia caerulea was measured using mesh bags. Leaf litter and roots of each species were incubated on both sites. The experiments lasted up to 3 years. The weighted decomposition constant was 0.23 per year for Molinia litter, and 0.10 per year for Erica litter; the decomposition constants for roots were 0.29 per year for Molinia but only 0.03 per year for Erica. The decomposition rates of leaf litters and roots were similar on both sites, and the chemical composition of the materials determined the decomposition rate. Litters and roots with high lignin concentrations decomposed slowly. During the experiments, most materials showed a net retention of N and P. Large net N releases were measured only for Molinia roots and basal internodes, and a large net P release was measured only for Molinia roots. It was concluded that the rate of accumulation of soil organic matter per gram of plant debris is slower on the site dominated by Molinia than on the site dominated by Erica. In the long term, N and P are probably released faster from Molinia than from Erica plant debris. Key words: decomposition, heathlands, Molinia, Erica.
Ultrastructure of Chlamydomonas reinhardtii following exposure to paraquat: comparison of wild type and a paraquat-resistant mutant
Authors: Bray Douglas F. , Bagu John R. , Nakamura Kazuo
Published: August 2009

A mutant (NL-51) of the unicellular green alga Chlamydomonas reinhardtii Dangeard isolated from a wild-type strain (137c+) was shown to be resistant to the bipyridilium herbicide paraquat at the concentration at which growth of the wild type was inhibited. Tetrad analysis from a cross between the mutant and the wild type showed 2:2 segregation, indicating that the resistance is under control of a single gene. Cross-resistance of the mutant to methionine and to methionine combined with riboflavin suggested that the resistance is due to increased levels of one of the enzymes capable of detoxifying active oxygens. Ultrastructural examination of mutant and wild-type cells exposed to paraquat revealed that the mutant cells were 3 to 4 times more resistant, but both strains showed the same sequence of deterioration. Damage was first manifested as swelling of the mitochondria and dilation of the perinuclear space. This was followed by disintegration of the nuclear matrix and the chloroplast thylakoids. Key words: Chlamydomonas reinhardtii, methionine resistance, paraquat, paraquat-resistant mutant, ultrastructure.
Macrofossil magnetobiostratigraphy for the upper Santonian–lower Campanian interval in the Western Interior of North America: comparisons with European stage boundaries and planktonic foraminiferal zonal boundaries
Authors: Leahy G. D. , Lerbekmo J. F.
Published: August 2009

Magnetostratigraphic samples were collected from the Milk River and Pakowki formations of southeastern Alberta to determine the polarity chron 34–33 r boundary. This boundary was located in the upper half of the Deadhorse Coulee Member, and is below the first local occurrence of the Western Interior ammonite Baculites obtusus. Comparison with the laterally equivalent Eagle Sandstone of Montana and Niobrara Formation of Colorado indicates that the 34–33 r contact is within either the Baculites sp. (smooth) or Baculites sp. (weak flank ribs) ammonite zone in the Western Interior of North America. Direct correlation of the Desmoscaphites erdmanni through Baculites asperiformis Western Interior ammonite zones with magnetobiostratigraphic sections of the upper Santonian–lower Campanian stages in Europe suggests that (i) the Santonian–Campanian boundary as defined in Europe is within the lower Baculites obtusus Zone and (ii) the Western Interior appearance of some ammonites and crinoids (Scaphites hippocrepis, Trachyscaphites spiniger, Marsupites, Uintacrinus) is profoundly time transgressive relative to the appearance of these same species in Europe. The date of 84 Ma for the Santonian–Campanian boundary is too old, and a date of around 80 Ma may be more accurate. The Santonian–Campanian boundary defined by ammonites, crinoids, and belemnites in Europe is within the lower part of chron 33 r, and is younger than the Santonian–Campanian boundary as determined by planktonic foraminifera at Gubbio, Italy.
Constraints on the P–T conditions and age of emplacement of the Lizard ophiolite, Cornwall: amphibole–plagioclase thermobarometry and 40Ar/39Ar geochronology of basal amphibolites
Authors: Sandeman Hamish A. , Chen Yanshao , Clark Alan H. , Farrar Edward
Published: August 2009

The basal slice of the Lizard Complex incorporates strongly foliated amphibolitic metabasites (Lower Landewednack Schists), interpreted as the remnants of a dynamothermal aureole formed beneath the ophiolite during intraoceanic thrusting. Structurally overlying the basal slice and occurring predominantly within the overlying Lizard peridotite is the Kennack Gneiss, a controversial, banded and gneissose unit comprising intimately mixed amphibolitic and granitic components, interpreted to represent commingled melts. Thermobarometry of hornblende–plagioclase pairs indicates that both the Landewednack Schists and the mafic component of the Kennack Gneiss recrystallized synkinematically at ca. 600 °C and 300–400 MPa. Three amphiboles, two from the Kennack Gneiss and one from the Landewednack Schists, yield disturbed 40Ar/39Ar age spectra characterized by low-temperature overprinting, but with good high-temperature plateaux with ages of 366.1 ± 4.2, 364.2 ± 4.8, and 359.8 ± 7.4 Ma, respectively. Theoretical diffusion modelling of the first of these spectra, based on a spherical geometry, indicates that it is best described by a 13% loss of argon during a thermal overprint, at ~220 Ma, on a primary cooling age (~500 °C) of 370 Ma. As has been documented in many ophiolite massifs, displacement of the Lizard Complex probably occurred promptly after its initial formation, but the imprecise crystallization age (ca. 375 ± 34 Ma) precludes construction of a precise cooling history.
A remarkable small ichthyosaur from the Upper Triassic of British Columbia, representing a new genus and species
Authors: McGowan C.
Published: August 2009

A small, nearly complete ichthyosaur skeleton is described from the Upper Triassic of Williston Lake, in northeastern British Columbia. The age of the material, based on conodonts, is early Norian. Although the length of the entire skeleton would probably not have exceeded 1 m, there is no evidence of immaturity–quite the contrary. Named Hudsonelpidia brevirostris, the new taxon shares some features with Triassic taxa, as exemplified by Mixosaurus from the European Middle Triassic, and with post-Triassic ichthyosaurs like Ichthyosaurus, from the English Lower Jurassic. Mixosaurian characters include an elongate tibia with emarginated pre- and postaxial margins, and phalanges in the hindfin with pre- and postaxial notches. Like Ichthyosaurus, the humérus is elongate rather than broad, so too is the pubis and ischium. Mixosaurus is unusual among Triassic ichthyosaurs for having a relatively large orbit, but the orbit is even more prominent in Hudsonelpidia, probably because of the shortness of the snout. Hudsonelpidia has an unusually large femur that approaches the length of the humérus, dwarfing the rest of the hindfin. The rostrum is unique in being perforated by foramina, but this could possibly be an abnormality.
A subaerial arthropod trackway from the Upper Silurian Clam Bank Formation of Newfoundland
Authors: Wright J. L. , Quinn L. , Briggs D. E. G. , Williams S. H.
Published: August 2009

Trackways are reported for the first time from Silurian rocks in Newfoundland. They occur in the Clam Bank Formation of the Port au Port Peninsula. At least one of the trackways represents one of the earliest known occurrences of a large subaerial arthropod trace fossil. It is preserved in hyporelief in a red fine-grained sandstone. The trackway, Diplichnites Dawson, 1873, consists of two parallel series of clearly defined imprints. It is attributed to a myriapod similar to the Lower Devonian Eoarthropleura. The sandstone contains halite pseudomorphs that indicate that the sediment horizon had been subject to desiccation immediately prior to the formation of the trackway. The arthropod walked on a red siltstone deposited in an alluvial flats environment. Analysis of the trackway suggests that the arthropod was approximately 23 cm long and had 17 pairs of walking appendages. It appears that a high-geared gait with a ratio of forestroke:backstroke of 8:2 was used in walking across the substrate, that is, approximately 20% of walking appendages were in contact with the substrate at any one time. This rapid gait, and the lack of a body drag mark, indicates that the arthropod was well adapted to subaerial locomotion. Knowledge of modern myriapod gaits has been used to extrapolate a theoretical trail, which compares well with the fossil trackway. Smaller, less well preserved trackways occur elsewhere in the Clam Bank Formation and may have been made by a similar arthropod.
Paleozoic fluidization, folding, and peperite formation, northern Sierra Nevada, California
Authors: Brooks Elwood R.
Published: August 2009

Recognition of peperite is important in establishing broad contemporaneity of magmatism and sedimentation. At an occurrence of peperite discovered recently among late Paleozoic island-arc deposits in the northern Sierra Nevada, it is possible to reconstruct the peperite-forming process largely from field observations alone. The generally concordant, upper margin of a basalt intrusion adjoins thinly laminated basaltic tuff in the Taylor Formation that was water saturated and unlithified at the time of intrusion. The water-saturated ash initially was heated by the intrusion at approximately constant, essentially hydrostatic pressure. Concurrently, the top of the intrusion was quenched and divided by shrinkage fractures. Pressure momentarily approached zero as the shrinkage fractures opened abruptly, causing vaporization of the pore water and substantial expansion and fluidizing flow of the resulting steam. The unlithified ash was swept into the shrinkage fractures, and, where the downward-propagating fractures intersected one another, basalt fragments were detached to form in situ peperite. Associated mesoscopic folds in thinly laminated tuff are shown to be a consequence of the peperite-forming process; they need not be attributed to forcible intrusion of the basaltic magma.