bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of anatomical variations of bone and vascular structures around the posterior atlantal arch using three-dimensional computed tomography angiography
Authors: Hong Jae Taek , Lee Sang Won , Son Byung Chul , Sung Jae Hoon , Yang Seung Ho , Kim Il Sub , Park Chun Kun
Published: February 2008

Object

The current study evaluates the incidence of anatomical variations of the V3segment of the vertebral artery (VA) and the posterior arch of the atlas (C-1). Failure to appreciate these types of anatomical variations can cause catastrophic injury to the VA during posterior approaches to the upper cervical spine.

Methods

In the present study, the authors analyzed the records of 1013 Korean patients who underwent computed tomography (CT) angiography to evaluate the incidence of anomalous variations in the third segment of the VA and to determine the incidence and morphometric characteristics of any detected posterior ponticuli. The authors also hoped to determine any specific imaging features that might indicate a VA anomaly around the craniovertebral junction.

Results

The mean age of the patients was ~ 55.7 years and the prevalence of a posterior ponticulus was 15.6%. The incidence rate of a posterior ponticulus in the male population was 19.3%, whereas in the female population it was 12.8%. The incomplete type of posterior ponticulus was more common than the complete type. The mean age of the patients with an incomplete posterior ponticulus (55.7 years) was significantly younger (p = 0.018) than the mean age of patients with a complete posterior ponticulus (57.6 years). The incidence rate of a persistent first inter-segmental artery was 4.7% and the incidence rate of a fenestrated VA was 0.6%. The area of the C-1 transverse foramen on the abnormal side was significantly smaller than that of the contralateral normal side.

Conclusions

The shape of the C-1 posterior arch and the third segment of the VA are heterogeneous. Therefore, preoperative radiological studies should be performed to identify any anatomical variations. Using preoperative 3D CT angiography, we can precisely identify an anomalous VA and significantly reduce the risk of VA injury.
Kyphosis recurrence after posterior short-segment fixation in thoracolumbar burst fractures
Authors: Wang Xiang-Yang , Dai Li-Yang , Xu Hua-Zi , Chi Yong-Long
Published: February 2008

Object

Recurrent kyphosis has been commonly seen after posterior short-segment pedicle instrumentation for a thoracolumbar fracture, but studies on this issue are relatively scarce, and the clinical significance of recurrent deformity is uncertain. No study has addressed the associations between the reduction of a burst fracture vertebra and the final recurrent kyphosis after implant removal. The aim of this study was to investigate the recurrent kyphosis after short-segment pedicle screw fixation in thoracolumbar burst fractures and to evaluate the effect of the degree of a vertebral reduction on the recurrent kyphotic deformity after implant removal.

Methods

Twenty-seven patients who had undergone posterior short-segment pedicle screw fixation for thoracolumbar junction burst fractures (T12–L2) were investigated retrospectively. The minimum follow-up period was 2 years (mean 2.7 years). Pain status was evaluated using the Denis pain scale. Changes in the anterior vertebral height ratio, vertebral wedge angle, upper intervertebral angle, lower intervertebral angle, Cobb angle, regional angle, and sagittal index were measured preoperatively, postoperatively, before implant removal, and at final follow-up. The correlation between the reduction of a fractured vertebra and the recurrent kyphotic deformity was also analyzed.

Results

After the initial surgical correction, the reduced vertebral body (VB) height (anterior vertebral height ratio and vertebral wedge angle) remained stable until final follow-up, whereas the intervertebral disc space (the upper and lower intervertebral angles) collapsed, resulting in a progressive kyphotic deformity (Cobb angle, regional angle, and sagittal index). No significant correlation was found between the final kyphosis and pain scale, but the 8 patients with a sagittal index > 15° showed a higher incidence of moderate to severe pain (P3–5 on the Denis pain scale) compared with the remaining 19 patients with a sagittal index < 15°. Significant positive correlation was found between recurrent kyphosis and vertebral wedge angle (r = 0.850, p < 0.001) and the reduced vertebral height (r = −0.727, p < 0.001).

Conclusions

Given that the correction loss occurs primarily through disc space collapse, the amount of the final kyphotic deformity was predictable by the degree of the fractured vertebral reduction as seen on the lateral x-ray study. Surgeons who perform posterior reduction and fixation procedures should pay more attention to reducing the fractured vertebral wedge angle to its intact condition, rather than the segmental angular parameters. If the wedge angle of the fractured VB is unacceptable after reduction, additional reconstruction of the anterior column may be necessary.
Effect of intraoperative position used in posterior lumbar interbody fusion on the maintenance of lumbar lordosis
Authors: Lee Jae Hyup , Lee Ji-Ho , Yoon Kang-Sup , Kang Seung-Baik , Jo Chris H.
Published: February 2008

Object

The objective in this study was to compare retrospectively the use of different operating tables with different positions for posterior lumbar interbody fusion (PLIF) and the effect on intraoperative and postoperative lumbar lordosis and segmental lordosis.

Methods

One hundred seventy-two patients with degenerative disease of the lumbar spine who underwent posterior decompression and PLIF in which a 0° polyetheretherketone cage and pedicle screw fixation were used were evaluated. Ninety-one patients underwent surgery on a Wilson table (Group I) and 81 patients were treated on an OSI Jackson spinal table (Group II). Preoperative standing, intraoperative prone, and postoperative standing lateral radiographs were obtained in each patient. The total lumbar and segmental lordosis were compared and analyzed according to the position in which the patients were placed for their operation.

Results

The intraoperative total lumbar lordosis was significantly decreased compared with the preoperative value. The postoperative total lumbar lordosis was similar, however, to the preoperative values in both groups. In Group I, the intraoperative segmental lordosis of L2–3 and L3–4 was significantly decreased compared with the pre-operative segmental lordosis. In Group II, the intraoperative segmental lordosis of L3–4, L4–5, L5–S1, and L4–S1 was significantly decreased compared with the preoperative segmental lordosis. The postoperative segmental lordosis of L4–5 was significantly decreased and L2–3 was significantly increased compared with the preoperative lordosis in both groups.

Conclusions

Intraoperative position does not affect postoperative total lumbar lordosis and segmental lordosis in short-segment PLIF of the lumbar spine in a retrospective analysis of the surgical procedure to maintain lordosis.
Does spinal surgery improve the quality of life for those with extradural (spinal) osseous metastases? An international multicenter prospective observational study of 223 patients
Authors: Ibrahim Ahmed , Crockard Alan , Antonietti Pierre , Boriani Stefano , Bünger Cody , Gasbarrini Alessandro , Grejs Anders , Harms Jürgen , Kawahara Norio , Mazel Christian , Melcher Robert , Tomita Katsuro
Published: February 2008

Object

Opinions vary widely as to the role of surgery (from none to wide margin excision) in the management of spinal metastases. In this study the authors set out to ascertain if surgery improves the quality of remaining life in patients with spinal metastatic and tumor-related systemic disease.

Methods

The authors included 223 patients in this study who were referred by oncologists and physicians over a 2-year period. All underwent surgery. Surgery was classified according to extent of excision ranging from en bloc excision or debulking to palliative surgery. All patients had a histologically confirmed diagnosis of epithelial spinal metastasis, and an oncology specialist undertook appropriately indicated adjuvant therapy in almost half of the patients.

Results

The mean patient age was 61 years. Excisional en bloc or debulking surgery was performed in 74%; the rest had (minimal) palliative decompression. All patients considered for surgery were included in the study. Patients presented with pain in 92% of cases, paraparesis in 24%, and abnormal urinary sphincter function in 22% (5% were incontinent). Breast, renal, lung, and prostate accounted for 65% of the cancers, and in 60% of patients there were widespread spinal metastases (Tomita Type 6 or 7).

The incidence of perioperative death (within 30 days of surgery) was 5.8%. Postoperatively 71% of the entire group had improved pain control, 53% regained or maintained their independent mobility, and 39% regained urinary sphincter function. The median survival for the cohort was 352 days (11.7 months); those who underwent excision survived significantly longer than those in the palliative group (p = 0.003). As with survival results, functional improvement outcome was better in those who underwent excision.

Conclusions

Surgical treatment was effective in improving quality of life by providing better pain control, enabling patients to regain or maintain mobility, and offering improved sphincter control. Although not a treatment of the systemic cancer, surgery is feasible, has acceptably low mortality and morbidity rates, and for many will improve the quality of their remaining life.
Evidence on magnetic resonance imaging of Brown–Séquard spinal cord injury suffered indirectly from a gunshot wound
Authors: Fassett Daniel R. , Harrop James S. , Vaccaro Alexander R.
Published: February 2008

✓The authors describe a rare case of Brown–Séquard syndrome as a result of indirect, concussive trauma to the spinal cord from a gunshot wound (GSW) and present the magnetic resonance (MR) imaging evidence obtained in this interesting case. The patient was shot in the anterior neck and the bullet passed through the lateral aspect of the C-7 lateral mass and transverse process. Bone fragments from the lateral aspect of C-7 were displaced posteriorly into the soft tissues, but no abnormalities were noted within the spinal canal except for high-intensity signal on T2-weighted MR imaging within the right side of the spinal cord. This is the first reported case to provide MR imaging evidence of a Brown–Séquard spinal cord injury as a result of indirect trauma (concussive injury) from a GSW.
Comparative analysis of late floral development and mating‐system evolution in tribe Collinsieae (Scrophulariaceae s.l.)
Authors: Armbruster W. Scott , Mulder Christa P. H. , Baldwin Bruce G. , Kalisz Susan , Wessa Bridget , Nute Helen
Published: February 2008

Species ofCollinsiaandTonella, the two sister genera of self‐compatible annuals that constitute tribe Collinsieae, show extensive variation in floral size and morphology and in patterns of stamen and style elongation during the life of the flower (anthesis). We used a nuclear ribosomal ITS phylogeny, independent contrasts, and phylogenetically corrected path analysis to explore the patterns of covariance of the developmental and morphological traits potentially influencing mating system. Large‐flowered taxa maintain herkogamy (spatial separation of anthers and stigmas) early in anthesis by differential elongation of staminal filaments, which positions each of the four anthers at the tip of the “keel” upon dehiscence. Small‐flowered taxa do not show this pattern of filament elongation. The styles of large‐flowered taxa elongate late in the 2–5 d of anthesis, resulting in late anther‐stigma contact and delayed self‐pollination. Anther‐stigma contact and self‐pollination occur early in anthesis in small‐flowered species/populations. Thus, we found complex covariation of morphological and developmental traits that can be interpreted as the result of multitrait adaptation for early selfing and high levels of autogamy, delayed selfing and higher levels of outcrossing, or intermediate levels of outcrossing. Continuous variation in these traits suggests the operation of continuous variation in selective optima or the combined effects of divergent selection and phylogenetic inertia.
Spectral reflectance and photosynthetic properties of Betula papyrifera (Betulaceae) leaves along an elevational gradient on Mt. Mansfield, Vermont, USA
Authors: Richardson Andrew D. , Berlyn Graeme P.
Published: February 2008

We studied relationships between spectral reflectance and photosynthesis of mountain paper birch, Betula papyrifera var. cordifolia (Regel) Fern., leaves from three different elevations on Mt. Mansfield (summit elevation 1339 m above sea level) in the Green Mountains of Vermont, USA. The different reflectance indices we used all suggested progressively increasing stress with increasing elevation. The photochemical reflectance index (PRI) indicated lower photosynthetic radiation use efficiency at higher elevations, the red edge position (λRE) indicated lower chlorophyll concentrations at higher elevations, and the structure‐independent pigment index (SIPI) indicated a higher carotenoid : chlorophyll a ratio at higher elevations. The rate of change in these indices with changes in elevation was much higher than we have observed in our studies of red spruce and balsam fir reflectance along a similar elevational gradient; we take this to be an indicator of the greater susceptibility of paper birch to elevation‐related stressors compared to the very stress‐tolerant conifers. At all light levels, photosynthesis decreased with increasing elevation; this pattern was most noticeable in the light‐saturated rate of photosynthesis (Asat), which was nearly twice as high in low‐elevation leaves (17.0 ± 1.0 μmol·m−2·s−1) than in high‐elevation leaves. The quantum yield of photosynthesis (Φ) exhibited a similar trend. Furthermore, the highest elevation leaves showed a much sharper transition from the light‐limited to the light‐saturated part of the light response curve than did the lowest elevation leaves. The photochemical reflectance index was highly correlated with Asat (r2 = 0.99) and Φ (r2 = 0.96). In addition to contributing to our knowledge of the ecophysiology of paper birch along a steep environmental gradient, these results are further evidence of the usefulness of reflectance measures for the rapid and noninvasive detection of plant stress, especially when used in conjunction with direct measurements of photosynthesis.
Floral ontogeny of Lecointea, Zollernia, Exostyles, and Harleyodendron (Leguminosae: Papilionoideae: Swartzieae s.l)
Authors: Mansano Vidal de Freitas , Tucker Shirley C. , Tozzi Ana Maria Goulart de Azevedo
Published: February 2008

Floral initiation and development were examined using scanning electron microscopy in Exostyles venusta, Harleyodendron unifoliolatum, Lecointea hatschbachii, and Zollernia ilicifolia. Common features include (1) unidirectional sepal initiation, (2) simultaneous petal initiation, (3) unidirectional initiation of each stamen whorl (except in the antesepalous whorl in Lecointea and Exostyles), (4) overlap in time of initiation of the two stamen whorls, and (5) initiation of the carpel concurrently with petals. Significant developmental features include (1) the first sepal median abaxial in all except Lecointea where it is non‐median abaxial; (2) intraspecific variation in petal aestivation in Exostyles, Harleyodendron, and Lecointea; (3) initiation of antepetalous stamens before the antesepalous ones in Zollernia, Exostyles, and Lecointea; and (4) ovule initiation before the carpel margins are fused in Exostyles. The stamen sequence has not been found in any other legumes. The following late developmental events distinguish the four genera from each other: copious hairs hold the anthers together as a domelike structure at anthesis in Harleyodendron; zygomorphy in Zollernia results from differing petal reflexion; late hypanthium in Exostyles, Lecointea, and Holocalyx (no hypanthium in Harleyodendron or Zollernia); and reflexed sepal lobes in Exostyles, Harleyodendron, and Zollernia but not in Holocalyx and Lecointea. The genera studied here are ontogenetically more similar to taxa of Sophoreae than to other Swartzieae that have been investigated. None of the taxa studied here has a ring meristem, the structure that characterizes the remaining swartzioid taxa studied elsewhere.
Origin of the Hawaiian endemic mints within North American Stachys (Lamiaceae)
Authors: Lindqvist Charlotte , Albert Victor A.
Published: February 2008

The Hawaiian endemic mints constitute a major island radiation, displaying a remarkable diversity of floral, fruit, and vegetative features. Haplostachys and Phyllostegia have flowers associated with insect pollination, whereas Stenogyne has flowers typical of bird pollination. The three genera had been thought to be closely related to East Asian members of Lamioideae tribe Prasieae because of the fleshy nutlets borne by Phyllostegia and Stenogyne. We evaluated the origins of the Hawaiian mints using phylogenetic analyses of DNA sequence data from the plastid rbcL and trnL intron loci and the nuclear ribosomal 5S nontranscribed spacer. The Hawaiian genera were found to be monophyletic but deeply nested inside another lamioid genus, Stachys. In particular, they were found to be most closely related to a group of temperate North American Stachys from the Pacific coast, suggesting that the Hawaiian mints derived from a single colonization event from western North America to the Hawaiian Islands. Furthermore, Stachys, which contains amphiatlantic and transberingian clades, was found to be polyphyletic, with some species more closely related to Gomphostemma, Phlomidoschema, Prasium, and Sideritis than to other species of Stachys. Based on chromosomal evidence and our phylogenetic analyses, we hypothesize that the Hawaiian mints may be polyploid hybrids whose reticulate genomes predate the Hawaiian dispersal event and are derived from Stachys lineages with flowers exhibiting insect‐ vs. bird‐pollination characteristics. Thus, the Hawaiian endemic mints may provide yet another insular system for the combined study of polyploidy, hybrid cladogenesis, and adaptive radiation.
Response of an allergenic species, Ambrosia psilostachya (Asteraceae), to experimental warming and clipping: implications for public health
Authors: Wan Shiqiang , Yuan Tong , Bowdish Sarah , Wallace Linda , Russell Scott D. , Luo Yiqi
Published: February 2008

We examined the responses of an allergenic species, western ragweed (Ambrosia psilostachya DC.), to experimental warming and clipping. The experiment was conducted in a tallgrass prairie in Oklahoma, USA, between 1999 and 2001. Warming increased ragweed stems by 88% when not clipped and 46% when clipped. Clipping increased ragweed stems by 75% and 36% in the control and warmed plots, respectively. In 2001, warming resulted in a 105% increase in ragweed aboveground biomass (AGB), and the ratio of ragweed AGB to total AGB increased by 79%. Dry mass per ragweed stem in the warmed plots was 37% and 38% greater than that in the control plots in 2000 and 2001, respectively. Although warming caused no difference in pollen production per stem, total pollen production increased by 84% (P < 0.05) because there were more ragweed stems. Experimental warming significantly increased pollen diameter from 21.2 μm in the control plots to 23.9 μm in the warmed plots (a 13% increase). The results from our experiment suggest that global warming could aggravate allergic hazards and thereby jeopardize public health.
Delayed and carryover effects of salinity on flowering in Iris hexagona (Iridaceae)
Authors: Van Zandt Peter A. , Mopper Susan
Published: February 2008

Saltwater intrusion into wetland ecosystems has destroyed or damaged many native plant populations. Iris hexagona is a salt‐sensitive species that exhibits intraspecific variation in salinity tolerance. To investigate the effect of salinity on flowering, we exposed I. hexagona collected from natural populations to salt treatments in a common garden. Experimental salinity additions strongly delayed flowering phenology, but the effect was not apparent until the second year, when less than 4 g/L NaCl delayed flowering up to 3 d. In the field, soil salinity and flowering phenology varied substantially within I. hexagona populations. Iris flowers are receptive to pollinators for 2 d or less, therefore a 3‐d delay could affect outcrossing dynamics, and ultimately, the evolutionary ecology of iris populations. Salinity also had a carryover effect; prior salinity exposure delayed flowering in irises that had been replanted in freshwater conditions for 6 mo. This is an important result because it suggests that episodic stress (such as tropical storms) can influence performance well after the stress has disappeared. Our research further underscores the importance of long‐term studies because a 1‐yr experiment would have failed to reveal the strong effects of salinity that emerged in the second year.
A QTL controlling stem morphology and vascular development in Lycopersicon esculentum × Lycopersicon hirsutum (Solanaceae) crosses is located on chromosome 2
Authors: Coaker Gitta L. , Meulia Tea , Kabelka Eileen A. , Jones Adriana K. , Francis David M.
Published: February 2008

The vascular tissue of higher plants is organized into a continuous and unified system that undergoes a transition between two highly differentiated structures, the root and the shoot. This transition was studied in tomato by investigating the genetic basis of morphological variation between Lycopersicon esculentum and L. hirsutum LA407. Our analysis concentrated on morphology in stem cross sections, and we detected heritable genetic differences in an inbred backcross population having L. esculentum as the recurrent parent and LA407 as the donor parent. Inbred backcross line (IBL) 2353 contained a donor segment from chromosome 2 and retained features of the LA407 stem vascular morphology. Marker‐trait analysis of vascular structure in a cross between IBL 2353 and L. esculentum showed significant (0.0001 ≤ P ≤ 0.0375) associations between markers on chromosome 2 and the size of primary vascular bundles, the shape of the vascular system, and the thickness of the secondary vascular tissue. Families with LA407 DNA for the markers on chromosome 2 had larger primary vascular bundles, more developed secondary vascular tissue, and a triangular vascular shape. These results suggest that the distal portion of chromosome 2 in LA407 contains a locus or loci affecting vascular morphology and development.
The vulnerability to freezing‐induced xylem cavitation of Larrea tridentata (Zygophyllaceae) in the Chihuahuan desert
Authors: Martínez‐Vilalta Jordi , Pockman William T.
Published: February 2008

The temperature dependence of freezing‐induced xylem cavitation was studied in a Chihuahuan desert population of Larrea tridentata (Zygophyllaceae). Field measurements of wood temperature and xylem embolism were combined with anatomical studies and laboratory measurements of embolism in stem and root samples frozen under controlled conditions. Our laboratory experiments corroborated the previously observed relationship between minimum freezing temperature and embolism. The area of the low‐temperature exotherms produced during the freezing treatments was correlated with the resulting embolism, suggesting that the freezing of water inside parenchyma cells is associated with the occurrence of xylem embolism. In the laboratory experiments, embolism in stems increased only at temperatures below −14°C. Although this meant that the studied population was more resistant to freezing‐induced xylem embolism than a previously studied population from the Sonoran desert, the impact of freezing was nevertheless greater because of much lower environmental temperatures. This result suggests that dieback associated with periodic extreme freezes may contribute to limiting the present distribution of L. tridentata in central New Mexico. Although laboratory experiments showed that root xylem embolism increased after freezing to less negative minimum temperatures than stems (significant effects at T = −7°C), root embolism in the field was lower than shoot embolism in accordance with measured soil temperatures throughout the study.
Phylogenetic relationships in the cactus family (Cactaceae) based on evidence from trnK/ matKandtrnL‐trnFsequences
Authors: Nyffeler Reto
Published: February 2008

Cacti are a large and diverse group of stem succulents predominantly occurring in warm and arid North and South America. Chloroplast DNA sequences of thetrnKintron, including thematKgene, were sequenced for 70 ingroup taxa and two outgroups from the Portulacaceae. In order to improve resolution in three major groups of Cactoideae,trnL‐trnFsequences from members of these clades were added to a combined analysis. The three exemplars ofPereskiadid not form a monophyletic group but a basal grade. The well‐supported subfamilies Cactoideae and Opuntioideae and the genusMaihueniaformed a weakly supported clade sister toPereskia. The parsimony analysis supported a sister group relationship ofMaihueniaand Opuntioideae, although the likelihood analysis did not.Blossfeldia, a monotypic genus of morphologically modified and ecologically specialized cacti, was identified as the sister group to all other Cactoideae. The tribe Cacteae was found to be sister to a largely unresolved clade comprising the generaCalymmanthium,Copiapoa, andFrailea, as well as two large and well‐supported clades.Browningiasensu stricto (excludingCastellanosia), the two tribes Cereeae and Trichocereeae, and parts of the tribes Notocacteae and Rhipsalideae formed one clade. The distribution of this group is largely restricted to South America. The other clade consists of the columnar cacti of Notocacteae, various genera of Browningieae, Echinocereeae, and Leptocereeae, the tribes Hylocereeae and Pachycereeae, andPfeiffera. A large portion of this latter group occurs in Central and North America and the Caribbean.
Aluminum in the opal silica reticule of phytoliths: a new tool in palaeoecological studies
Authors: Carnelli Adriana L. , Madella Marco , Theurillat Jean‐Paul , Ammann Brigitta
Published: February 2008

X‐ray microanalysis was employed to screen biogenic plant silica extracted from the aboveground tissues of 20 species (Gramineae, Cyperaceae, Ericaceae, and Coniferae) occurring in subalpine and alpine grasslands, heaths, and woodlands on siliceous bedrock in the Valaisan Swiss Alps. Among the taxa investigated, only woody species produced a high proportion of phytoliths containing aluminum in the form of aluminosilicates. This difference between the chemical composition of wood and that of herbaceous phytoliths has important implications for the sourcing of phytoliths. As applications for palaeoenvironmental studies can be expected to be far‐reaching, the potential of this microanalytical technique is discussed.
Green light reversal of blue‐light‐stimulated stomatal opening is found in a diversity of plant species
Authors: Talbott Lawrence D. , Nikolova Ganka , Ortiz Arisa , Shmayevich Irene , Zeiger Eduardo
Published: February 2008

Reversal by green light of blue‐light‐stimulated stomatal opening was found across a number of plant species, including leguminous and nonleguminous dicots and grass and nongrass monocots. Simultaneous exposure to equal fluence rates of blue and green light resulted in ∼50% reversal of normal blue light opening. Complete reversal occurred when the fluence rate of green light was approximately twice that of blue light. These results suggest that blue–green reversibility of stomatal opening is a basic photobiological property of guard cells. The blue–green reversibility of stomatal opening has been hypothesized to ensue from the cycling of two interconvertible, isomeric forms of the blue‐light photoreceptor, zeaxanthin. Testing of blue–green reversibility could provide a valuable diagnostic tool for zeaxanthin‐mediated blue‐light photoperception.
Weedy adaptation in Setaria spp. V. Effects of gaseous environment on giant foxtail (Setaria faberii) (Poaceae) seed germination
Authors: Dekker Jack , Hargrove Mark
Published: February 2008

The effects that naturally occurring gases (oxygen, nitrogen, carbon monoxide) may cause in dormant giant foxtail (Setaria faberii) seed germination under favorable temperature and moisture conditions were investigated. The germination responses to gas mixtures supported the hypothesis that S. faberii germination behavior is regulated by the amount of oxygen taken into hydrated seed over time. Setaria faberii seed germination was markedly affected by O2 concentration (in N2) above and below that of air (20% O2): the largest increase in germination (from 37 to 60%) occurred between 20–25% O2; between 0–10% O2, germination increased from 0–30%; and surprisingly germination at 10 and 20% O2 was similar. These observations reveal an asymmetrical response to incremental changes in O2 above and below that typically found in agricultural soils. Carbon monoxide had opposite effects on S. faberii germination in air depending on concentration, stimulation, and inhibition: germination increased from 37 to 56% with the addition of 1% CO, but decreased from 37 to 14% with 75% added CO. An explanation may be that there are two separate effects of CO, each occurring in different physiological systems of dormant seeds at the same time. At high concentrations (75%) in air CO inhibited seed germination, probably by inhibiting mitochondrial respiration. But low CO concentrations (0.1 or 1%) in air stimulated seed germination. It was not apparent which physiological system(s) CO and O2 affected. It seems unlikely that CO‐stimulated germination arises from effects on the respiratory apparatus, but may be a consequence of CO interactions with an as yet unknown physiological factor in the seed. We provide a model of Setaria spp. dormancy consistent with its seed morphology, the gas‐germination data, and the hypothesized second physiological factor that may be involved in CO stimulated germination.
Microscopy of a cytoplasmic male‐sterile soybean from an interspecific cross between Glycine max and G. soja (Leguminosae)
Authors: Smith Marianne B. , Palmer Reid G. , Horner Harry T.
Published: February 2008

Cytoplasmic male sterility has been found independently in soybean three times since 1995, but no microscopic investigation has been published. The purpose of this microscopic study was to establish the developmental sequence leading to sterility in a cytoplasmic male‐sterile soybean line that has been found to be stable under all environmental conditions tested and to demarcate the temporal and spatial parameters that result in degeneration of the microspores and pollen grains. Light microscopy showed an abnormal development and/or premature degeneration of the tapetum after meiosis II, but some pollen grains persisted until after microspore mitosis. The pollen grains never completely filled with reserves. Premature formation of the endothecium also was evident. Histochemical staining for water‐insoluble carbohydrates revealed an abnormal pattern of starch deposition in anther walls that coincided with lack of pollen filling. Electron microscopy showed degeneration of the inner mitochondrial membrane in the tapetal cells as the first detectable change leading to cell degeneration. Subsequently, the tapetal endoplasmic reticulum exhibited atypical concentric rings. Pollen grains displayed mitochondria with unusually enlarged inner mitochondrial spaces, degraded plastids, a rudimentary intine, and no starch or lipid reserves. Results link mitochondrial degeneration, premature formation of the endothecium, and energy deprivation to male sterility.
A comparison of two methods of calculating GST, a genetic measure of population differentiation
Authors: Culley Theresa M. , Wallace Lisa E. , Gengler‐Nowak Karla M. , Crawford Daniel J.
Published: February 2008

GST is a genetic statistic describing differentiation of populations and has frequently been compared with Hamrick and Godt's (1989) review of the plant literature. We show here that some comparisons may be inappropriate if GST was calculated in a different way than that used by Hamrick and Godt (HG). An alternative method advocated by Nei is mathematically different from the HG technique, occasionally resulting in different GST values. We reviewed 695 studies that appeared between 1990 and September 1999 that cited Hamrick and Godt (1989) and found that many of these calculated GST according to Nei's method (46%), with the majority of these papers (61%) including comparisons to Hamrick and Godt's review. We suggest that if GST estimates are compared across studies, it is most appropriate to calculate them the same way. However, we found that in most cases, the magnitude of difference in GST values was small, suggesting that qualitative comparisons of GST estimates between most studies are probably valid. Nevertheless, we have identified theoretical and empirical situations in which large differences in GST values are likely to arise. Thus, we advise future investigators to carefully consider which method to use in calculating GST for a given data set.
Role of warm stratification in promoting germination of seeds ofEmpetrum hermaphroditum(Empetraceae), a circumboreal species with a stony endocarp
Authors: Baskin Carol C. , Zackrisson Olle , Baskin Jerry M.
Published: February 2008

The broad objective of this research was to define the role of warm (≥15°C) stratification in breaking dormancy in seeds with stony endocarps that require warm‐plus‐cold (∼0°–10°C) stratification for germination. This question was addressed using seeds (true seed + endocarp, hereafter called seeds) ofEmpetrum hermaphroditum. Only 2–5% of freshly matured seeds collected in September and October at five sites in Sweden germinated in light at daily alternating temperature regimes of 15°/6°, 20°/10°, and 25°/15°C. Dormancy was not due to impermeability of the stony endocarp surrounding each seed, and embryos did not grow prior to radicle emergence. Thus, seeds did not have physical, morphological, or morphophysiological dormancy. Long periods of either cold stratification (20 or 32 wk) or warm stratification (16 wk) resulted in a maximum of 22–38 and 10% germination, respectively, in light at 25°/15°C. After 12 wk warm stratification plus 20 wk cold stratification, 83–93% of the seeds germinated in light at the three temperature regimes. For a cold stratification period of 20 wk, germination increased with increase in length of the preceding warm stratification treatment. Gibberellic acid (GA3) promoted germination of 77–87% of the seeds. Based on dormancy‐breaking requirements and response to GA3, 62–78% of the seeds had intermediate physiological dormancy; the others had nondeep physiological dormancy. Contrary to suggestions of several other investigators that warm stratification is required to make the endocarp permeable to water via its breakdown by microorganisms, our results withE. hermaphroditumshow that this is not the case. In this species, warm stratification is part of the dormancy‐breaking requirement of embryos in seeds with intermediate physiological dormancy.
Phylogenetic relationships in Selaginellaceae based on RBCL sequences
Authors: Korall Petra , Kenrick Paul
Published: February 2008

A phylogenetic framework is developed for the clubmoss family Selaginellaceae based on maximum parsimony analyses of molecular data. The chloroplast gene rbcL was sequenced for 62 species, which represent nearly 10% of living species diversity in the family. Taxa were chosen to reflect morphological, geographical, and ecological diversity. The analyses provide support for monophyly of subgenera Selaginella and Tetragonostachys. Stachygynandrum and Heterostachys are polyphyletic. Monophyly of Ericetorum is uncertain. Results also indicate a large number of new groupings not previously recognized on morphological grounds. Some of these new groups seem to have corresponding morphological synapomorphies, such as the presence of rhizophores (distinctive root‐like structures), aspects of rhizophore development, and leaf and stem morphology. Others share distinctive ecological traits (e.g., xerophytism). For many groups, however, no morphological, ecological, or physiological markers are known. This could reflect patchy sampling and a lack of detailed knowledge about many species. Despite a lengthy fossil record dating from the Carboniferous Period, cladogram topology indicates that most of the living tropical species are probably the products of more recent diversifications. Resurrection plants, extreme xerophytes characterized by aridity‐driven inrolling of branches and rapid revival on rehydration, have evolved at least three times in quite different clades.
Maintenance of sexually dimorphic preadult traits in Marchantia inflexa (Marchantiacae)
Authors: Fuselier Linda , McLetchie Nicholas
Published: February 2008

Marchantia inflexa, a dioecious thallose liverwort, is sexually dimorphic in clonal expansion traits. We used selection analyses to measure the magnitude and direction of selection on clonal fitness to uncover possible mechanisms for the maintenance of preadult sexually dimorphic characters. We planted replicates of genotypes of female and male M. inflexa in two light environments in a greenhouse and measured morphological and phenological characters associated with growth and asexual reproduction. Timing to onset of asexual reproduction and plant size early in development were under sex‐specific selection in a low light environment. Additionally, females exhibited a sex‐specific cost of plasticity in the timing of their onset of asexual reproduction in high light. Selection on asexual fitness tended to shift traits toward monomorphism rather than sexual dimorphism, whereas the expressed phenotype of females was congruent with patterns of selection acting on sexual fitness. We detected negative trade‐offs between asexual and sexual fitness components in females in one light environment. Opposing selective forces acting on asexual and sexual fitness components may explain how sexual dimorphisms persist in the face of selection for monomorphism in the preadult phase.
Evolution of phenotypic integration inBrassica(Brassicaceae)
Authors: Murren Courtney J. , Pendleton Nicole , Pigliucci Massimo
Published: February 2008

Phenotypic integration is a necessary characteristic of living organisms that results from genetic, developmental, and functional relationships among traits. The nature of these relationships can be influenced by the environment. We examined patterns of phenotypic integration of six species of rapid cyclingBrassicaand ofRaphanus sativuswithin a phylogenetic context. Specifically, we tested the hypothesis that hybrid species show intermediate levels of integration in morphological and life‐history characters compared to their putative parentals. We used matrix correlation tests to examine if cytogenetic relationships or ecological similarities among species partially explained the patterns of phenotypic integration. There was a significant negative relationship between the ecological and cytogenetic matrices, suggesting that more closely related species were ecologically dissimilar. However, neither ecological nor cytogenetic matrices significantly explained differences among species in the pattern of their phenotypic correlations. Set correlation analysis indicated that important traits within the modules and the strength of the correlations within modules differed across species. We also found that there were a greater number of significant correlations between modules than within modules. Hybrid species were more integrated (had greater number of significant trait correlations) than either of their parents, both within and between modules. However, univariate analyses of character means of the hybrid species were not significantly different from the combined mean of their putative parents for 5, 6, or 7 of the 11 phenotypic characters (forBrassica napus,B. junceaandB. carinata, respectively); for the remaining characters, the hybrids were more similar to one of the parents.
Reproductive phenology, life‐forms, and habitats of the Venezuelan Central Plain
Authors: Ramírez Nelson
Published: February 2008

Reproductive phenology of 171 plant species belonging to 57 families of angiosperms was studied according to life‐forms in four habitat types in a savanna‐forest mosaic on the Venezuelan Central Plain. Flowering, unripe fruit, and mature fruit patterns were affected significantly according to life‐forms and habitats respectively. Production of flowers, unripe fruits, and mature fruits showed marked seasonality for all habitats except for the forest. Flowering peaked during the rainy season, and fruiting peaked toward the end of the rainy season. The savanna and the disturbed area had similar proportions of species that flowered over the year. The percentage of species with unripe fruits produced throughout the year was more seasonal for the disturbed area than for the other habitats. Mature fruit patterns showed an increase during the late rainy season for the ecotone and savanna. A large number of herbaceous (annual and perennial) and liana species flowered during the wet season, and a smaller fraction flowered during the dry season; and trees, shrubs, and epiphytes increased flowering activity during the dry season. Unripe fruit patterns were similar to those of flowering for all life‐forms, however, tree species were less seasonal. Mature fruit production by shrubs peaked in the period of maximum rainfall, while the peak for perennial herbs was in the late rainy season and the peak for annual herbs was during the transition between the rainy season and the dry season. The largest proportion of tree and liana species with ripe fruits occurred during the dry season. Differences among phenological patterns in habitats were caused mainly by life‐forms and promote a wider distribution of reproductive events in habitats and overall community in the Venezuelan Central Plain.
A method to estimate pollen viability from pollen size variation
Authors: Kelly John K. , Rasch Aaron , Kalisz Susan
Published: February 2008

The mean diameter of viable pollen grains is approximately 13 μm greater than the mean diameter of inviable grains in Mimulus guttatus. We show that this difference is large enough to be detected by particle counters and that these machines can be used to obtain a rapid estimate of pollen viability. While requiring a separate calibration, a size‐based statistic is also strongly correlated with pollen viability in Collinsia verna. These results suggest that statistics derived from the size distribution of pollen grains may provide an alternative to more labor‐intensive methods for estimating pollen viability, particularly in cases where inviability results from inbreeding depression or hybrid failure.
Apical organization and maturation of the cortex and vascular cylinder inArabidopsis thaliana (Brassicaceae) roots
Authors: Baum Stuart F. , Dubrovsky Joseph G. , Rost Thomas L.
Published: February 2008

Developmental and physiological studies of roots are frequently limited to a post‐germination stage. In Arabidopsis, a developmental change in the root meristem architecture during plant ontogenesis has not previously been studied and is addressed presently. Arabidopsis thaliana have closed root apical organization, in which all cell file lineages connect directly to one of three distinct initial tiers. The root meristem organization is dynamic and changes as the root ages from 1 to 4 wk post‐germination. During the ontogeny of the root, the number of cells within the root apical meristem (RAM) increases and then decreases due to changes in the number of cortical layers and number of cell files within a central cylinder. The architecture of the initial tiers also changes as the root meristem ages. Included in the RAM's ontogeny is a pattern associated with the periclinal divisions that give rise to the middle cortex and endodermis; the three‐dimensional arrangement of periclinally dividing derivative cells resembles one gyre of a helix. Four‐ or 5‐wk‐old roots exhibit a disorganized array of vacuolated initial cells that are a manifestation of the determinate nature of the meristem. Vascular cambium is formed via coordinated divisions of vascular parenchyma and pericycle cells. The phellogen is the last meristem to complete its development, and it is derived from pericycle cells that delineate the outer boundary of the root.
Discordance of chloroplast and nuclear ribosomal DNA data in Osmorhiza (Apiaceae)
Authors: Yoo Ki‐Oug , Lowry Porter P. , Wen Jun
Published: February 2008

Phylogenetic studies were conducted to evaluate interspecific relationships in Osmorhiza (Apiaceae: Apioideae) using sequences of the ITS regions of nuclear ribosomal DNA, the chloroplast ndhF gene, and two noncoding regions (trnL intron, and trnL [UAA] 3′ exon‐trnF [GAA] intergenic spacer). All data sets suggest the monophyly of the New World taxa and showed that Osmorhiza aristata from Asia is relatively divergent from other members of the genus, even though it is morphologically similar to the eastern North American O. claytonii and O. longistylis. The ITS and chloroplast DNA trees differ in the relationships among the New World taxa, especially the phylogenetic position of O. occidentalis, O. glabrata, and O. depauperata. The lack of congruence between the two data sets may be a result of hybridization or introgression. Although there is high discordance between nrITS and two chloroplast DNA data sets, the latter two show similar topologies.
Phylogeny and classification of Naucleeae s.l. (Rubiaceae) inferred from molecular (ITS, rBCL, and tRNT‐F) and morphological data
Authors: Razafimandimbison Sylvain G. , Bremer Birgitta
Published: February 2008

Parsimony analyses of the tribe Naucleeae sensu lato (s.l.) using the noncoding internal transcribed spacer (ITS) regions of nuclear rDNA, the protein‐coding rbcL and noncoding trnT‐F regions of chloroplast DNA, and morphological data were performed to construct new intratribal classification, test the monophyly of previous subtribal circumscriptions, and evaluate the generic status of Naucleeae s.l. Fifty‐two ITS, 45 rbcL, and 55 trnT‐F new sequences are published here. Our study supports the monophyly of the subtribes Anthocephalidae, Mitragynae, Uncariae all sensu Haviland and Naucleinae sensu Ridsdale. There was no support for Cephalanthidae sensu Haviland and Adininae sensu Ridsdale. Naucleeae can be subdivided into six highly supported and morphologically distinct subtribes, Breoniinae, Cephalanthinae, Corynantheinae, Naucleinae, and Mitragyninae, Uncarinae, plus one, Adininae, which is poorly supported. The relationships among these subtribes were largely unresolved. We maintain the following 22 genera: Adina, Adinauclea, Breonadia, Breonia, Burttdavya, Cephalanthus, Gyrostipula, Haldina, Janotia, Ludekia, Metadina, Mitragyna, Myrmeconauclea, Nauclea, Neolamarckia, Neonauclea, Ochreinauclea, Pausinystalia, Pertusadina, Sarcocephalus, Sinoadina, and Uncaria. Pseudocinchona is reestablished. Corynanthe is restricted to C. paniculata and Hallea is reincluded in Mitragyna. Our results were inconclusive for assessing the relationships among Adina, Adinauclea, Metadina, and Pertusadina due to lack of resolution.