Nitric oxide (NO) is an important signalling molecule with diverse physiological functions in plants. In plant cell, it is synthesised in several metabolic ways either enzymatically or nonenzymatically. Due to its high reactivity, it could be also cytotoxic in dependence on concentration. Such effects could be also mediated by NO-derived compounds. However, the role of NO in photosynthetic apparatus arrangement and in photosynthetic performance is poorly understood as indicated by a number of studies in this field with often conflicting results. This review brings a short survey of the role of exogenous NO in photosynthesis under physiological and stressful conditions, particularly of its effect on parameters of chlorophyll fluorescence.

Abstract:The experiment assessed the variability of in seven clones of willow plants of high biomass production (Salix smithiana S-218, Salix smithiana S-150, Salix viminalis S-519, Salix alba S-464, Salix 'Pyramidalis' S-141, Salix dasyclados S-406, Salix rubens S-391). They were planted in a pots for three vegetation periods in three soils differing in the total content of risk elements. Comparing the calculated relative decrease of total metal contents in soils, the phytoextraction potential of willows was obtained for cadmium (Cd) and zinc (Zn), moderately contaminated Cambisol and uncontaminated Chernozem, where aboveground biomass removed about 30% Cd and 5% Zn of the total element content, respectively. The clones showed variability in removing Cd and Zn, depending on soil type and contamination level: S. smithiana (S-150) and S. rubens (S-391) demonstrated the highest phytoextraction effect for Cd and Zn. For lead (Pb) and arsenic (As), the ability to accumulate the aboveground biomass of willows was found to be negligible in both soils. The results confirmed that willow plants show promising results for several elements, mainly for mobile ones like cadmium and zinc in moderate levels of contamination. The differences in accumulation among the clones seemed to be affected more by the properties of clones, not by the soil element concentrations or soil properties. However, confirmation and verification of the results in field conditions as well as more detailed investigation of the mechanisms of cadmium uptake in rhizosphere of willow plants will be determined by further research.

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The aim of this work was to estimate the changes in contents of different sulfur (S) fractions in soils under conditions of lowering inputs of S from emissions together with the influence of application of manure and mineral fertilizers. Soil samples from long-term field experiments were used for this purpose. The samples were taken from 10 sites from precise long-term field experiments with different soil-climatic conditions in the Czech republic. The samples were analyzed using the following fractionation: (i) water soluble S (H 2 o extracts), (ii) sorbed S (0.032M naH 2 Po 4 extracts) and (iii) S occluded with carbonates (1M HCl extract). Furthermore, the concentration of total S (S tot ) and organic S (S org ) was determined. Soil samples were taken in the years 1981 and 2007. During 26 years a decrease of S tot by about 3-8%, water soluble S by 65-68% and sorbed S by 39-44% were observed in the topsoil of the evaluated soils. Furthermore, a low increase in the content of organic S was observed. The estimated ratio of S org reached 78.7-80.9% from S tot in the year 1981 and 87.7-89.8% in 2007. Farmyard manure (40 t/ha) applied every 4 years did not have a significant influence on S fractions and S tot contents in soils; intensive S fertilizing increased S tot and mobile S forms contents in soils. very close correlations were obtained especially between S tot and water soluble S and organic S.