Peroxidases in Relation to Removal of Dormancy and Germination of Apple Embryos

The changes in germination, peroxidase activity and isoperoxidase spectrum have been studied in apple embryos at 5°C (stratification) and at 20°C in the presence or absence of seed coats. The embryo dormancy is progressively released at 5°C, but not at 20°C. The peroxidase activity in embryos covered with seed coats is very low at 5°C as well as at 20°C which corresponds to a restricted number of isoenzymes. In isolated embryos the peroxidase activity increases significantly. This is due to an increase in both the number and the activity of the isoperoxidases and it is more pronounced at 20°C than at 5°C. The obtained results suggest that the soluble peroxidases are not involved in the process of the release of embryo dormancy. The variations observed are attributed to the growth process following germination, which can occur even at low temperature.     

The influence of the light environment and photosynthesis on oxidative signalling responses in plant–biotrophic pathogen interactions

Plants grow in a constantly fluctuating environment, which has driven the evolution of a highly flexible metabolism and development necessary for their sessile lifestyle. In contrast to the situation in the natural world, the detailed dissection of the regulatory networks that govern plants' responses to abiotic insults and their interaction with pathogens have been studied almost exclusively in controlled environments where a single challenge has been applied. However, the question arises of how such pathways operate when the plant is subjected to multiple stresses, especially where the expression of overlapping gene sets and common signalling molecules, such as reactive oxygen species (ROS), are implicated. This review will focus on the responsiveness of leaves to their light environment and how this might influence both basal and induced resistance to infection by biotrophic pathogens. While several signalling pathways operate in a complex network of defence responses, the functioning of the salicylic acid (SA) signalling pathway will receive specific consideration. This is because information is becoming available of its role in abiotic stress responses and it dependency on light. This article covers several topics, some of which formerly have received scant attention. These include the effects of infection on photosynthetic performance and carbohydrate metabolism, the parallels between the induction of acclimation to high light and immunity to pathogens, the role of light in the functioning of the SA signalling pathway and the light sensitivity of lesion formation and the use of lesion mimic mutants and transgenic plants. Finally, a model is proposed that attempts to extrapolate these controlled environment-based studies to the functioning of defences against pathogens in a field-grown crop.     

Shell structure and affinity of the Carboniferous microproblematicurn Saccamminopsis

Extremely well preserved specimens of the Carboniferous microproblematicum Saccamminopsis Sollas, 1921, from the Visean of Poland reveal a primary structure of the chamber wall, different from that hitherto suggested in hypothetical reconstructions. The calcareous wall is regularly perforated by fine pores which sometimes appear to be bifurcated, but no larger holes are present. The new observations, however, do not resolve the question of affiliation to algae or foraminifers. Similarity of general morphology and shell microstructure justifies a synonymization of Saccam-minopsis the Famennian genus Baculella Conil & Dreesen, 1985. Saccamminopsis is indicative of an extremely shallow marine sedimentary environment.□ Algae, Carboniferous, Foraminifera, problematica , Saccamminopsis.     

NEURAL METHODS OF CALIBRATION OF SENSORS FOR GAS MEASUREMENTS AND AROMA IDENTIFICATION SYSTEM

The article presents the neural methods of calibration of gas sensors for use in an artificial electronic nose for gas measurements. Different neural network solutions will be presented and compared. They include the classical multilayer perceptron, neuro-fuzzy networks and support vector machines. The other aspect illustrated in the article is the introductory preprocessing of the measured sensor signals in order to attain the highest possible efficiency of the gas measuring system. The theoretical considerations will be supported by the numerical experiments concerning the application of the electronic nose. The first practical aspect is concerned with the application of the developed system for classification problems and will be illustrated in the examples of the recognition of the biocomponents in the gasoline and the recognition of smells of cosmetic cream at the aging process. The second one belongs to the estimation problem and is concerned with the determination of the concentration of the particular gas components in the mixture of gases.

PRACTICAL APPLICATIONS

The results presented in the article may find practical application for calibration of the electronic nose in gas measurements. The electronic nose is widely used for smell recognition. It may find practical application in the petroleum, cosmetics or food industry for the assessment of the quality of their products. Military application is also of great interest.