Are early somatic embryos of the norway spruce (Picea abies (L.) Karst.) organised?

Background Somatic embryogenesis in conifer species has great potential for the forestry industry. Hence, a number of methods have been developed for their efficient and rapid propagation through somatic embryogenesis. Although information is available regarding the previous process-mediated generation of embryogenic cells to form somatic embryos, there is a dearth of information in the literature on the detailed structure of these clusters. Methodology/Principal Findings The main aim of this study was to provide a more detailed structure of the embryogenic tissue clusters obtained through the in vitro propagation of the Norway spruce (Picea abies (L.) Karst.). We primarily focused on the growth of early somatic embryos (ESEs). The data on ESE growth suggested that there may be clear distinctions between their inner and outer regions. Therefore, we selected ESEs collected on the 56th day after sub-cultivation to dissect the homogeneity of the ESE clusters. Two colourimetric assays (acetocarmine and fluorescein diacetate/propidium iodide staining) and one metabolic assay based on the use of 2,3,5-triphenyltetrazolium chloride uncovered large differences in the metabolic activity inside the cluster. Next, we performed nuclear magnetic resonance measurements. The ESE cluster seemed to be compactly aggregated during the first four weeks of cultivation; thereafter, the difference between the 1H nuclei concentration in the inner and outer clusters was more evident. There were clear differences in the visual appearance of embryos from the outer and inner regions. Finally, a cluster was divided into six parts (three each from the inner and the outer regions of the embryo) to determine their growth and viability. The innermost embryos (centripetally towards the cluster centre) could grow after sub-cultivation but exhibited the slowest rate and required the longest time to reach the common growth rate. To confirm our hypothesis on the organisation of the ESE cluster, we investigated the effect of cluster orientation on the cultivation medium and the influence of the change of the cluster’s three-dimensional orientation on its development. Maintaining the same position when transferring ESEs into new cultivation medium seemed to be necessary because changes in the orientation significantly affected ESE growth. Conclusions and Significance This work illustrated the possible inner organisation of ESEs. The outer layer of ESEs is formed by individual somatic embryos with high metabolic activity (and with high demands for nutrients, oxygen and water), while an embryonal group is directed outside of the ESE cluster. Somatic embryos with depressed metabolic activity were localised in the inner regions, where these embryonic tissues probably have a very important transport function

Photoacoustic study of the effect of fuel oil on the photosynthetic system of algae Scenedesmus armatus

Photoacoustic (PA) spectroscopy was applied to study variability in the photosynthetic energy storage (ES) and changes in the PA-signal amplitude of the green alga Scenedesmus armatus, grown in a batch culture in the presence of aqueous fuel-oil extract (AFOE). The adaptation process of the alga was observed for 16 days by means of intercomparison between the PA-signal of the alga cultures in the polluted environment and a control culture. Characteristic changes in the ultrastructure of the alga have been observed

The role of photomodyfication in toxicity of policyclic aromatic hydrocarbons to microalgae Scenedesmus armatus

W 24-godzinnych testach badano wpływ antrachinonu (ANTQ) i fenantrenochinonu (PHEQ) na populację Scenedesmus armatus, napowietrzaną 0,1% lub 2% CO₂. Wyznaczono współczynnik EC₅₀ dla ANTQ (0,56 mg·dm⁻³) oraz PHEQ (0,1 mg·dm⁻³); stężenia te stosowano w dalszych badaniach. W kulturach napowietrzanych 0,1% CO₂, antrachinon nie wpływał na fotosyntezę i zawartość karotenoidów, stymulował oddychanie i aktywność dysmutazy ponadtlenkowej (SOD) oraz nieznacznie redukował zawartość chlorofili. Podwyższenie stężenia CO₂ do 2% podniosło toksyczność ANTQ i PHEQ - liczebność populacji osiągała jedynie 24% kontroli. ANTQ hamował oddychanie oraz aktywność SOD, niemal całkowicie blokował fotosyntezę i silnie redukował zawartość barwników fotosyntetycznych. W obydwu wariantach stężenia CO₂ PHEQ stymulował oddychanie, redukował intensywność fotosyntezy oraz zawartość chlorofili i karotenoidów. Wzrost aktywności SOD był wyraźniej widoczny w kulturach napowietrzanych 2% CO₂. Uzyskane wyniki wskazują, iż proces fotomodyfikacji fenantrenu prowadzi do drastycznego wzrostu toksyczności tego związku, podczas gdy toksyczny wpływ antrachinonu jest dwukrotnie mniejszy w porównaniu z antracenem. Niekorzystne działanie zarówno ANTQ jak i PHEQ jest prawdopodobnie skutkiem stresu oksydacyjnego, manifestującego się wyraźniej w intensywnie rosnących kulturach napowietrzanych 2% CO₂.The effects of anthraquinone (ANTQ) and phenanthrenequinone (PHEQ) on Scenedesmus armatus cells were examined in 24-h tests. Cells were grown in a batch culture system at low (0.1%) and elevated (2%) CO₂ concentrations. We found that ANTQ was less toxic to the algae (EC₅₀= 0.56 mg·dm⁻³) than PHEQ (EC₅₀= 0.1 mg·dm⁻³). In cultures aerated with 0.1% CO₂, ANTQ at 0.56 mg·dm⁻³ had no influence on photosynthesis and content of carotenoids, while dark respiration and superoxide dismutase (SOD) activity were stimulated. Chlorophyll a and b content was reduced only slightly. At 2% CO₂ the toxicity of ANTQ and PHEQ markedly increased. At 2% CO₂ ANTQ inhibited respiration and SOD activity, almost completely blocked growth and photosynthesis and strongly lowered chlorophyll content. Regardless of CO₂ concentration, PHEQ inhibited photosynthesis and diminished chlorophyll content, while respiration was stimulated. PHEQ stimulated the total SOD activity and this effect was generally higher at elevated CO₂. The results obtained suggest, that the toxicity of phenanthrene significantly increases after photomodyfication, while antraquinone is two times less toxic than anthracene. The harmful influence of both ANTQ and PHEQ probably resulted from oxidative stress, especially noted in the intensively growing cultures aerated with 2% CO₂