Bio-CO2 fixation with formate dehydrogenase from Saccharomyces cerevisiae and water-soluble zinc porphyrin by visible light

The CO₂ fixation system, that is formic acid production from CO₂ with FDH from Saccharomyces cerevisiae and reduced Methyl viologen produced by the visible light photosensitization of zinc tetrakis(4-methylpyridyl) porphyrin, was investigated. When the sample solution containing triethanolamine, zinc tetrakis(4-methylpyridyl) porphyrin, Methyl viologen, NaHCO₃ and FDH in phosphate buffer was irradiated, formic acid was produced. The amount of formic acid production and the yield of CO₂ to formic acid were estimated to be 0.104 ± 0.008 mM and 10.4%, respectively.     

Oxygen Exchange in Relation to Carbon Assimilation in Water-stressed Leaves During Photosynthesis

In a study on metabolic consumption of photosynthetic electronsand dissipation of excess light energy under water stress, O₂and CO₂ gas exchange was measured by mass spectrometry in tomatoplants using ¹⁸O₂ and ¹³CO₂. Under water stress, gross O₂ evolution(E_O), gross O₂ uptake (U_O), net CO₂ uptake (P_N), gross CO₂ uptake(TPS), and gross CO₂ evolution (E_C) declined. The ratio P_N/E_Ofell during stress, while the ratios U_O/E_O and E_C/TPS rose.Mitochondrial respiration in the light, which can be measureddirectly by ¹²CO₂ evolution during ¹³CO₂ uptake at 3000 µll^{–1 13}CO₂, is small in relation to gross CO₂ evolutionand CO₂ release from the glycolate pathway. It is concludedthat PSII, the Calvin cycle and mitochondrial respiration aredown-regulated under water stress. The percentages of photosyntheticelectrons dissipated by CO₂ assimilation, photorespiration andthe Mehler reaction were calculated: in control leaves morethan 50 % of the electrons were consumed in CO₂ assimilation,23 % in photorespiration and 13 % in the Mehler reaction. Undersevere stress the percentages of electrons dissipated by CO₂assimilation and the Mehler reaction declined while the percentageof electrons used in photorespiration doubled. The consumptionof electrons in photorespiration may reduce the likelihood ofdamage during water deficit.     

Development of a semi-automatic system for pollen recognition

A semi-automatic system for pollen recognitionis studied for the european project ASTHMA. The goal of such a system is to provideaccurate pollen concentration measurements. This information can be used as well by thepalynologists, the clinicians or a forecastsystem to predict pollen dispersion. At first,our emphasis has been put on Cupressaceae, Olea, Poaceae and Urticaceae pollen types. The system is composed of two modules: pollengrain extraction and pollen grain recognition. In the first module, the pollen grains areobserved in light microscopy and are extractedautomatically from a pollen slide coloured withfuchsin and digitized in 3D. In the secondmodule, the pollen grain is analyzed forrecognition. To accomplish the recognition, itis necessary to work on 3D images and to usedetailed palynological knowledge. Thisknowledge describes the pollen types accordingto their main visible characteristerics and tothose which are important for recognition. Somepollen structures are identified like the porewith annulus in Poaceae, the reticulum in Oleaand similar pollen types or the cytoplasm inCupressaceae. The preliminary results show therecognition of some pollen types, likeUrticaceae or Poaceae or some groups of pollentypes, like reticulate group.     

Interspecific variation in plumage colour among birds: species recognition or light environment?

Abstract The traditional explanation for interspecific plumage colour variation in birds is that colour differences between species are adaptations to minimize the risk of hybridization. Under this explanation, colour differences between closely related species of birds represent reproductive character displacement. An alternative explanation is that interspecific variation in plumage colour is an adaptive response to variation in light environments across habitats. Under this explanation, differences in colour between closely related species are a product of selection on signal efficiency. We use a comparative approach to examine these two hypotheses, testing the effects of sympatry and habitat use, respectively, on divergence in male plumage colour. Contrary to the prediction of the Species Isolation Hypothesis, we find no evidence that sympatric pairs of species are consistently more divergent in coloration than are allopatric pairs of species. However, in agreement with the Light Environment Hypothesis, we find significant associations between plumage coloration and habitat use. All of these results remain qualitatively unchanged irrespective of the statistical methodology used to compare reflectance spectra, the body regions used in the analyses, or the exclusion of areas of plumage not used in sexual displays. Our results suggest that, in general, interspecific variation in plumage colour among birds is more strongly influenced by the signalling environment than by the risk of hybridization.     

Light-Dependence of Phospholipase D Activity in Oat Seedlings

The effect of light on the activity of phospholipase D (PLD) in oat (Avena sativa L.) seedlings and the dependence of this enzyme activity on the regime of their illumination were studied. The PLD activity in etiolated seedlings was 1.5–2.0-fold higher than in green plants. The illumination of etiolated seedlings with white light resulted in a decrease in PLD activity to its level in the seedlings grown under light. In contrast, the transfer of green seedlings to darkness enhanced the activity of the enzyme up to its level in etiolated seedlings. The illumination of etiolated seedlings with red light inhibited the PLD as well. It was shown that this photoeffect decreased with seedling aging and correlated with a phytochrome content in plants. Far-red light reversed the effect of red light. The involvement of phytochrome in the control of the PLD activity is discussed.     

Secondary metabolism of hairy root cultures in bioreactors

Summary In vitro cultures are being considered as an alternative to agricultural processes for producing valuable secondary metabolites. Most efforts that use differentiated cultures instead of cell suspension cultures have focused on transformed (hairy) roots. Bioreactors used to culture hairy roots can be roughly divided into three types: liquid-phase, gas-phase, or hybrid reactors that are a combination of both. The growth and productivity of hairy root cultures are reviewed with an emphasis on successful bioreactors and important culture considerations. The latter include strain selection, production of product in relation to growth phase, media composition, the gas regime, use of elicitors, the role of light, and apparent product loss. Together with genetic engineering and process optimization, proper reactor design plays a key role in the development of successful large scale production of secondary metabolites from plant cultures.     

Changes in the Relative Number of Bipolar-Like Cells in the Retina of Pleurodeles waltl as a Function of Age and as a Result of Light Exposure

The study of the population of bipolar-like cells (displaced bipolars) was continued in order to establish their role in development and regeneration of the retina in lower vertebrates. The size of the population of these cells was estimated on serial semithin sections in the retina of normal eyes in adult and young newt Pleurodeles waltl, as well as in adult newts subjected to long-term bright illumination. The population of displaced bipolars was significantly increased with reference to all cells of the outer nuclear layer. In young and illuminated animals, their numbers were approximately 1.3 and 1.4 times that in the adult animals not exposed to constant light. The results obtained favor the earlier suggestion of the involvement of the displaced bipolars in growth and restoration of the outer nuclear layer in the retina of newts during development and after trauma.     

Conidioma production of the white root rot fungus in axenic culture under near-ultraviolet light radiation

 Conidiomata of the white root rot fungus were produced in axenic culture under near-ultraviolet light radiation. Pieces of sterilized Japanese pear twigs were placed on 7-day-old oatmeal agar culture in plates. The plates were further incubated for 5 days and then illuminated by near-ultraviolet light. Synnemata developed on the twigs within 5 weeks in 19 of 20 isolates tested, and conidia were observed in 12 of the 19 isolates. The synnemata and conidia produced were morphologically identical to those of Dematophora necatrix. Received: October 29, 2001 / Accepted: March 11, 2002     

Photogravitropic equilibrium in <Emphasis Type="Italic">Avena</Emphasis> coleoptiles: fluence rate–response relationships and dependence on dark adaptation and clinostating

Phototropism of Avena coleoptiles was measured in response to blue-light irradiation lasting between 2 and 24 h. During this time the coleoptiles established a bending angle of photogravitropic equilibrium that was dependent on the time of irradiation and also on the pretreatment in light or darkness prior to stimulation. The absolute threshold for the photogravitropic equilibrium in response to blue light was 10⁻⁸ μmol m⁻² s⁻¹. Photon fluence rate–response curves, which were generated after several hours of dark adaptation, had a characteristic shape with a prominent optimum in the middle of the dynamic range. Curves which were generated without prior dark adaptation displayed no such optimum. Clinostating dark-adapted coleoptiles caused an increase of sensitivity and responsiveness during a 2-h period of unilateral irradiation. The advantages and the drawbacks of long-term irradiation experiments for the investigation of phototropism and the generation of action spectra are discussed. Received: May 14, 2001 / Accepted: December 7, 2001