The Fine Structure of Saprodinium dentatum Lauterborn, 1908 as a Representative of the Odontostomatida (Ciliophora)

The fine structure of the sapropelic ciliate Saprodinium dentatum is described based on phase-contrast microscopy, silver-staining techniques, cryo-fracture scanning electron microscopy, and thin sections. The study concentrates on a detailed analysis of the somatic cortex and the oral ciliature of this highly asymmetric, laterally compressed ciliate. The cell shape is dominated by a number of site-specific spines and the curving course of 10 somatic kineties (SK 1–10). The SK, composed of dikinetids, show an intrakinety differentiation that seems characteristic for other odontostomes as well. The anterior segment of the SK is mostly ciliated, followed by a non-ciliated segment in which the kinetosomes lack all typical fiber systems. Except for SK 4–6, the posterior segment is ciliated again, forming the spine kinetics associated with particular caudal spines. The anterior segment of SK 3 through SK 7 form the frontal band, which together with the two frontal kineties constitutes the main locomotory organelle for a ciliate that creeps on the substratum. A short kinety with inverse polarity, not seen in earlier light microscopical studies, was observed near the oral spine. We made particular effort to find a logical explanation for the observed association of the SK with the various caudal spines. The oral ciliature consists of nine adoral organelles located in a tripartite oral cavity. The absence of a paroral ciliature together with the position of the cytostome anterior to the adoral organelles may be the result of rotational movement of the oral apparatus during the evolution of these bizarre ciliates. Results are discussed with special reference to the phylogenetic relationship of the Odontostomatida to the Heterotrichida and no conclusive answer was found in this first electron microscopical study of an odontostomatid ciliate.     

Regulation of adenosine 5'-phosphosulfate sulfotransferase by sulfur dioxide in primary leaves of beans (Phaseolus vulgaris)

SO₂ inhibited the light-induced increase of extractable adenosine 5′-phosphosulfate sulfotransferase in greening primary leaves of bean seedlings (Phaseolus vulgaris L. cv. Saxa (Radio) Stamm Vatter). In green primary leaves containing appreciable extractable adenosine 5′-phosphosulfate sulfotransferase activity, SO₂ treatment for 20 h decreased the activity of the enzyme to between 10 and 20% of the initial level. After removal of SO₂ from the air, the extractable adenosine 5′-phosphosulfate sulfotransferase activity increased after a lag, both in green and greening primary leaves, and was back to the control level after about 48 h. The sulfate concentration was increased about fourfold during SO₂ treatment. An increase in sulfate sulfur accompanied by a decrease in adenosine 5′-phosphosulfate sulfotransferase was also observed when bean seedlings, after excision of the roots, were transferred to nutrient solutions containing high sulfate concentrations, suggesting that sulfate is involved in the regulation of the enzyme.     

Multiple Forms of the Constitutive Wheat Cinnamyl Alcohol Dehydrogenase

Three cinnamyl alcohol dehydrogenase (CAD) isoenzymes were separatedfrom etiolated wheat seedlings (Triticum aestivum L.) and examinedby native gel electrophoresis. Two of these enzymes (CAD-1 andCAD-2) were purified to apparent homogeneity. They exhibiteda marked difference in substrate affinity. On sodium dodecylsulphate-acrylamide gel the isolated isoenzymes showed onlyone protein band each with an M_r 45000 and 40000 daltons, respectively,whereas on native gel two bands were identified for each protein.Isoenzymes from a variety of diploid, tetraploid, and hexaploidwheats were compared. The results indicated that the CAD polymorphismcould be genetically determined. Key words: Cinnamyl alcohol dehydrogenase, lignin, Triticum aestivum L     

Gravity induces fast electrical field change in soybean hypocotyls

Abstract. Measurement of the electrical field along soybean hypocotyls shows the development of a positive electrical potential in the lower side approximately 1 min after horizontal placement. The time is as fast or faster than the geotropic presentation time of soybean seedlings. The maximum positive electrical field potential is produced in a zone 1–2 cm below the hook, which is the region showing the geotropic curvature.     

Thirty years of in situ tree growth under elevated CO2: a model for future forest responses?

Rising concentrations of atmospheric carbon dioxide have been predicted to stimulate the growth of forest trees. However, long-term effects on trees growing to maturity and to canopy closure while exposed to elevated CO₂ have never been examined. We compared tree ring chronologies of Mediterranean Quercus ilex which have been continuously exposed to elevated CO₂ (around 650 μmol mol^–1) since they were seedlings, near two separate natural CO₂ springs with those from trees at nearby ambient-CO₂‘control’ sites. Trees grown under high CO₂ for 30 years (1964–93) showed a 12% greater final radial stem width than those growing at the ambient-CO₂ control sites. However, this stimulation was largely due to responses when trees were young. By the time trees were 25–30 y old the annual difference in tree ring width between low and high CO₂ grown trees had disappeared. At any given tree age, elevated CO₂ had a relatively greater positive effect on tree ring width in years with a dry spring compared to years with more rainfall between April and May. This indicates a beneficial effect of elevated CO₂ on tree water relations under drought stress. Our data suggest that the early regeneration phase of forest stands can be accelerated in CO₂-enriched atmospheres and that maximum biomass per land area may be reached sooner than under lower CO₂ concentrations. In our study, high CO₂ grown Q. ilex trees reached the same stem basal area at the age of 26 y as control trees at 29 y, i.e. three years earlier (faster turnover of carbon?). Reliable predictions of the future development of forests need to account for the variable responses of trees over their entire lifetime. Such responses to elevated CO₂ can presently only be assessed at such unique field sites.     

Carnivorous dental adaptations in tribosphenic mammals and phylogenetic reconstruction

The molar morphology and structure of seven groups of flesh-eating mammals (Deltatheroida, Borhyaenoidea, Stagodontidae, Dasyuroidea, Creodonta, Carnivora, and Prionogale ) are compared. The dental adaptations to carnivorous diet are remarkably similar in the seven groups. Derived taxa within these groups all possess a postvallum-prevallid shearing with a reduction of the paracone relative to the metacone (except in the Deltatheroida), a large postmetacrista, a reduced stylar shelf, a reduced protocone, a large blade-like paraconid and a reduced metaconid and talonid. The constancy of these features (regarded as a single functional complex) and of their evolutionary pattern in phylogenetically distant groups, is evidence of their high potential for homoplasy. Therefore these character states should be used with extreme care in reconstructing phylogeny and, when possible, associated to cranial features. Several phylogenetic interpretations using them are discussed, some of which are regarded as poorly supported.     

Role of ethylene in the regulation of cell death and leaf loss in ozone-exposed European beech

To test the involvement of ethylene in mediating ozone-induced cell death and leaf loss in European beech ( Fagus sylvatica L.), tree seedlings were exposed to proportionally increased or decreased field ozone levels for up to 6 months. Ozone treatment caused cell death and accelerated leaf loss at higher than ambient levels, but had only minor effects at ambient and no effects at subambient ozone levels. The emission of ethylene, the levels of its precursor, 1-aminocyclopropane-1-carboxylate (ACC), and mRNA levels of specific ACC synthase ( FS-ACS2 ) and ACC oxidase ( FS-ACO1 ) isoforms showed a persistent increase and preceded cell death by approximately 2 weeks. Inhibition of ethylene biosynthesis led to reduced lesion formation whereas application of ACC accelerated ozone-induced cell death and leaf loss. Similar results were obtained when adult beech trees were exposed to 2 × ozone by a whole tree free-air canopy exposure system. The results suggest a role of ethylene in amplifying ozone effects under field conditions in this major European broad-leaved tree species.     

Macro-alga population shows low but significant heterogeneity in developmental instability with no detectable association with individual fitness

We studied among-individual variation in developmental instability (DI) and fitness-related parameters in 80 individual plants of Fucus vesiculosus (Phaeophyta). To minimize differential environmental effects, plants were sampled from one environmentally homogenous population. DI was measured as fluctuating asymmetry (FA) of four bilaterally symmetric traits (branch length, receptacle length and width, and bladder width) for an average total of 30 structures per individual. FA levels varied significantly among individual plants, consistent with a coefficient of variation of 0.12 for organism-wide DI or 0.13–0.21 for trait-specific DI. These values are lower than estimates for other organisms, suggesting that the genetic heterogeneity in DI was low. The data provide some evidence for organism-wide DI, but simulations show that organism-wide and trait-specific variation cannot be conclusively separated. Growth rate of branch tips was determined experimentally, demonstrating significant variation among individuals. FA was not significantly correlated with growth rate or with morphological variables associated with fecundity, age, size, and health. At the same time, the signs of all the correlation coefficients were consistent with the expectation of a negative relationship between DI and fitness. The simulations indicated that the correlation between FA and the underlying DI was comparatively strong (high hypothetical repeatability), implying that the lack of significant associations between FA and fitness variables reflected a weak relationship between DI and these fitness parameters. This weak relationship may be related to the low amount of DI variation in the study population.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 92 , 277–286.