Photoacoustic spectra (PAS) were obtained for the cyanobacterium Synechococcus (Anacystis nidulans) cells embedded in isotropic and stretched polyvinyl alcohol films. The polarized radiation with the electric vector changing in 30° intervals with respect to given direction in a sample plane was used. Two cyanobacterium strains, one with very low biliprotein content, second with normal amount of biliproteins were investigated. The polarized absorption and fluorescence spectra were also measured. Conclusions were drawn about the thermal deactivation occurring in differently oriented pools of chromophores and about mutual orientation of their transition moments. Thermal deactivation in carotenoids (Cars) of both strains was different. The ratio of Car thermal deactivation to the thermal deactivation of chlorophyll (Chl) was higher in cyanobacteria with lower content of biliproteins than in the strain with normal amount of these complexes. Hence biliproteins can play the role in excitation energy transfer from Cars to Chls. For complex biological samples, polarized PAS can be a more sensitive method to investigate the directions of the absorption transition moments than the widely used polarized absorption spectra. and A. Planner ... [et al.].
Photon-induced absorbance changes at 830 nm (ΔA830) related to redox transformations of P700, primary electron donor of photosystem 1 (PS1), were examined in barley leaves treated with diuron and methyl viologen. In such leaves, only soluble reductants localized in chloroplast stroma could serve as electron donors for P700+. Δ A830 were induced by 1-min irradiation of leaves with "actinic light" (AL, 700±6 nm) of various irradiances. Two exponentially decaying components with half-times of 2.75 (fast component, relative magnitude of 62 % of ΔA830) and 11.90 s (slow one, 38 % of ΔA830) were distinguished in the kinetics of dark relaxation of ΔA830 after leaf irradiation with saturating AL. The components reflecting P700+ dark reduction in two units of PS1 differed in the rate of electron input from stromal reductants. The decline in AL irradiance reduced steady state δA830 magnitude, which was also accompanied by a decrease in the contribution of fast component to the overall P700+ dark reduction kinetics. The photon-response curves were obtained separately for rapidly and slowly decaying δA830. The values of half-saturating irradiance were 0.106 and 0.035 μmol m-2 s-1 for rapidly and slowly reduced PS1 units, respectively. The ratio of rate constants of P700+ dark reduction for rapidly and slowly reduced PS1 units was 1.4 times higher than the ratio of their half-saturating irradiances thus indicating higher relative antenna size in rapidly reduced PS1 units. The latter finding, taken together with higher relative amount of P700, favours the view that rapidly and slowly reduced PS1 units reflect P700+ reduction by stromal reductants in spatially separated PS1α and PS1β complexes. and E. A. Egorova, N. G. Bukhov.
The aim of our study was to answer whether any positive correlation exists between K+ uptake and salt tolerance in wheat. We carried out a sand-culture experiment with salt-tolerant, DK961 (ST), and salt-sensitive, JN17 (SS), wheat cultivars, where photosynthesis, the K+/Na+ ratio, growth, and the biomass yield were examined. The seeds were exposed for four weeks to six NaCl concentrations (50, 100, 150, 200, 250, and 300 mM), which were embodied in the Hoagland solution. Salinity-induced decrease of K+ or increase in the Na+ content was much smaller in ST than that in SS. The reductions in the light-saturated photosynthetic rate (P Nmax) and chlorophyll content caused by salinity were smaller in the ST compared to SS. Stomatal conductance decreased in both cultivars under saline conditions; nevertheless, it was lower in SS than in ST. The antioxidative capacity was higher in ST than that in SS under saline conditions. Significant positive correlations were observed in both cultivars between K+ contents and P Nmax/biomass yields. We suggest that higher-affinity K+ uptake might play a key role in higher salt tolerance and it might be a reliable indicator for breeding new species of salt-tolerant wheat., D. Cheng, G. Wu, Y. Zheng., and Obsahuje seznam literatury
We demonstrate the feasibility of assaying and predicting post-harvest damage in lemons by monitoring chlorophyll (Chl) fluorescence. Fruit quality was assayed using a commercial instrument that determines photosynthetic performance by imaging Chl fluorescence parameters under different irradiances. Images of Chl fluorescence from individual lemons reveal that photosynthesis is active throughout the post-harvest ripening process. Because photosynthesis is highly sensitive to biotic and abiotic stress, variations in Chl fluorescence parameters over the surface of a lemon fruit can be used to predict areas that will eventually exhibit visible damage. The technique is able to distinguish between mould-infected areas that eventually spread over the surface of the fruit, and damaged areas that do not increase in size during ripening. This study demonstrates the potential for using rapid imaging of Chl fluorescence in post-harvest fruit to develop an automated device that can identify and remove poor quality fruit long before visible damage appears. and L. Nedbal ... [et al.].
The subject of this paper is a typological classification of the acanthus ornamentation of the Czech manuscripts from the 14th – 15th centuries. The definition of the four types of Czech acanthus ornaments is studied in relation to their genesis and their sources in the illumination in Bohemia, Italy and Western Europe. The ornamentation of the manuscripts of the followed period is confronted with its resources and parallels in the contemporary sculpture and applied arts. The modifications of the types of acanthus is followed in the context of the relations of the Prague workshops with the regional production in the Czech Lands and also from the standpoint of their possible influence on the evolvement of acanthus ornament in the illumination of the Western and Central Europe of the 15 and early 16th centuries. The paper deals also with the possibilities of the content interpretation of the ornament decoration of the Medieval manuscripts and offers other questions and problems to be solved in the further study of this theme.
By a detailed analysis of decoration and collation of this manuscript it was found out that three principal masters participated in its decoration. The top quality of the decoration can be found in the work of the first master continuing the Byzantine, Venetian, and Saxon-Thuringian creation. The second master uses the first master´s work. The work of the third master is quite different as it is connected with original Bohemian production – with the Mater verborum manuscript. This different quality of illuminations allows to suppose that the codex originated in a scriptorium acting somewhere in Bohemia and employing a number of artists and their helpmates.
On the basis of the formal and iconographical analysis, after evaluation of the existing literature and taking in consideration hypothetical cultural historical circumstances of the creation of the manuscript, the author of the paper suggests to consider the manuscript a Bolognese school product – from the style group dating to the turning of 1320s and 1330s (in connection with Master from 1328 and his circle and with ties to painters active before Vitale da Bologna, as a point of departure for further development in Val Padana and in Veneto) and supposes that the cardinal Bertrand du Pojet might be a receiver of the manuscript. Dating is shift ed between 1331–1333 on the basis of the research results and on connections with the historical activities of the Luxembourg dynasty members in Italy in that time.
The paper focuses on the patronage of Cardinal Jacoppo Stefaneschi (died 1343) viewed from the perspective of book and monumental painting in the context of more general problems. First it analyses the relationship between the aesthetically discerning patron and Giotto, a celebrated artist tending towards a different style orientation and then it outlines some conceivable ramifications of this association for the further development of Giotto´s workshop. It examines the possible iconographic significance of the Stefaneschi altar in the period political context, and following this proposes more precise dating of the Stefaneschi Triptych and the Codex of St George. This layer of Italian art is immensely inspiring for the subsequent development of Bohemian painting in the period of the Luxembourgs.