The anatomy of the stigma and style from Cyclamen persicum (Mill.) cv. "pure white" and its relation to pollination success.

Old flowers of Cyclamen generate few or no seeds. To understand the pollination problems of Cyclamen we investigate the general anatomy of the stigma and the style of Cyclamen persicum by scanning electron microscopy at different stages of floral maturity. Our investigations confirm that there is a hollow style. Against data commonly found in the literature, we present evidence of pollen germination and tube growth that show the stigma is not outside the style but inside it. Furthermore the maturation process of the style during the flowering time indicates a mechanism by which the stigma becomes shut off through closure at the terminal aperture of the style. At 3 to 5 days after anthesis there was the beginning closure of the style which was nearly completed at 21 days. The substance which leads to the closure is still unknown. The closure of the hollow style is a probable cause for failure of seed set in flowers not pollinated early in anthesis.

Dentin Protection of Different Desensitizing Varnishes During Stress Simulation: An In Vitro Study.

OBJECTIVE: The aim of this study was to investigate dentin protection of different desensitizing varnishes (light- and self-curing) during acid action/abrasion stress and thermocyclic loading in vitro. METHODS: Dentin discs of 2 mm thickness were cut from 120 human molars, embedded, and polished. Specimens were randomized into five groups (n=24): A, negative control; B, Gluma Desensitizer; C, Cervitec plus (self-curing); D, Seal&Protect; and E, Admira Protect (light-curing). In groups B-E, varnish was applied on two-thirds of the dentin surface, and one-third acted as internal control. Stress cycle (2 cycles/day) for specimens were as follows: 1, acid action (pH: 2.9: five minutes); 2, remineralization (synthetic saliva: 60 minutes); 3, brushing (100 strokes); 4, thermocycling (five cycles); and 5, remineralization (synthetic saliva: six hours) for each group (n=12) for 30 (15 days) or 60 times (30 days). Specimens were analyzed using an incident light microscope. Substance loss was measured in micrometers. Statistical analysis was performed with the multiple contrast test (p<0.05). RESULTS: Groups B and C had a significantly lower dentin loss than A (p<0.01). After 30 days, group A showed the highest dentin loss (p<0.01), whereas the other groups lacked a significant difference regarding their substance loss (dentin and/or varnish; p>0.05). Varnish layer loss was shown for groups D and E with a remaining protective layer; groups A-C showed dentin removal. CONCLUSION: All four varnishes are protective compared with an untreated control. Light-curing varnishes might provide higher dentin protection than self-curing materials.

Morphology and nrITS phylogeny of the genus Pinguicula L. (Lentibulariaceae), with special attention to embryo evolution.

The genus Pinguicula (Lentibulariaceae) is unusual within the dicot order Lamiales because of the occurrence of both embryos with two cotyledons and those with just one cotyledon. In order to elucidate the infrageneric relationships and the evolutionary history of the embryo, we analysed (1) the internal transcribed spacers ITS1 and ITS2 of the nuclear ribosomal DNA (nrITS) of 29 Old and New World taxa of Pinguicula, and (2) the morphological and anatomical characters of the seeds. We suggest that the cotyledon number and spermoderm structure were quite unstable in the evolution of Pinguicula. Although basal nodes of the nrITS tree are sensitive to taxon sampling, all tree topologies found in this study imply homoplasy in the cotyledon number.

Hip joint degeneration due to cam impingement: a finite element analysis.

The goal of this study was to investigate the impact of cam impingement, a biomechanical risk factor, on hip joint degeneration and ultimately coxarthrosis. 3D finite element solid models of a healthy and a pathologic hip were developed based on clinical reports. The biphasic characteristics of cartilaginous tissues were considered to identify localised solid matrix overloading during normal walking and sitting down (SD). Localised femoral intrusion at the anterior-superior pelvic horn was revealed in the pathologic hip during SD, where the radial and meridional solid stresses in the acetabular cartilage and circumferential solid stresses within the acetabular labrum increased by 3.7, 1.5 and 2.7 times, respectively. The increased solid-on-solid stresses, reduction in fluid-load support and associated higher friction during articulation may result in joint wear and other degenerative changes in the hip.

Genetic differentiation in the genus Lithops L. (Ruschioideae, Aizoaceae) reveals a high level of convergent evolution and reflects geographic distribution.

Southern Africa is one of the hot spots for plant biodiversity, with ca. 80% of species endemic to this area. Rapid and recent radiations in Southern African plant genera were triggered by fine-scale differences in climate, topography and geology. The genus Lithops (Ruschioideae, Aizoaceae) contains 37 species and is widely distributed in Southern Africa. Species delimitation within the genus is challenging because the limited number of morphological characters in these reduced succulents varies intensely between populations, presumably as adaptations to local geological environments. We analysed phylogenetic relationships within Lithops using non-coding chloroplast DNA (trnS-trnG intergenic spacer), nuclear ribosomal internal transcribed spacer (nrITS) sequences and AFLP data. Genetic variability of the sequence data was very low, but AFLP data detected nine clades within Lithops that do not fit current morphology-based taxonomy. Two of these clades are separated by their distribution on the northern and eastern border of the distribution area, and four clades are found in the Gariep Centre in the estuary of the Orange River. Morphological similarities, especially colour of leaves, evolved repeatedly within the clades, thus we hypothesise that closely related species became adapted to different soil types in a mosaic-like geological environment. One-third of the species are found in the Gariep Centre, characterised by extremely diverse edaphic habitats.

Genetic diversity in natural and anthropogenic inland populations of salt-tolerant plants: random amplified polymorphic DNA analyses of Aster tripolium L. (Compositae) and Salicornia ramosissima Woods (Chenopodiaceae).

Eight populations of Aster tripolium (Compositae) and six of Salicornia ramosissima (Chenopodiaceae) from inland, naturally salt-contaminated habitats and anthropogenic salt-polluted sites in central Germany (Thuringia, Anhalt-Saxony) were analysed using random amplified polymorphic DNA (RAPD) markers to investigate the patterns of genetic variation. In both species, the genetic diversity observed in the younger, anthropogenic sites caused by potash mines during the last century was found to be not significantly lower than in the older, naturally salt-contaminated habitats. Therefore, it is speculated that the loss of genetic diversity caused by founder effects on the anthropogenic habitats was balanced by successive colonization events, actual gene flow between populations, or the rapid growth of populations on the secondary habitats after colonization. Analyses of molecular variance (amova) of the RAPD markers, neighbour-joining clustering of populations based on Reynolds' co-ancestry distances, and Mantel tests indicate that: (i) anthropogenic habitats were colonized independently; (ii) genetic differentiation among populations of S. ramosissima is more pronounced than in A. tripolium, which is considered to be mainly due to biological differences between the two species; and (iii) the geographical pattern of genetic diversity was considerably modulated by historical events and/or population genetic effects.

A neural correlate of syntactic encoding during speech production.

Spoken language is one of the most compact and structured ways to convey information. The linguistic ability to structure individual words into larger sentence units permits speakers to express a nearly unlimited range of meanings. This ability is rooted in speakers' knowledge of syntax and in the corresponding process of syntactic encoding. Syntactic encoding is highly automatized, operates largely outside of conscious awareness, and overlaps closely in time with several other processes of language production. With the use of positron emission tomography we investigated the cortical activations during spoken language production that are related to the syntactic encoding process. In the paradigm of restrictive scene description, utterances varying in complexity of syntactic encoding were elicited. Results provided evidence that the left Rolandic operculum, caudally adjacent to Broca's area, is involved in both sentence-level and local (phrase-level) syntactic encoding during speaking.