A comparative physiologico-genetical study of activities of some enzymes in a heterotic single cross hybrid of maize (Zea mays L.)

Summary In field trials conducted over three growth seasons I studied the differences in activities of the enzymes: polyphenoloxidase, ascorbateoxidase and peroxidase, with a heterotic single-cross hybrid of maize and its pollen-sterile analogue. Additional observations were made for differences between the single-cross hybrids and their parental lines. The samples (staminate spikelets) were taken at random just before and after tasselling. Significant differences could be established concerning the object set. Comparison of the self-pollinating line of maize with the pollen-sterile analogue revealed the down ward trend in peroxidase (P) activity with the pollen-sterile line; the upward trend in polyphenoloxidase (PPO) activity and the downward trend in ascorbateoxidase (A) activity were observed with the pollen-sterile line before tasselling. After tasselling, activity of PPO showed a downward and that of A an upward trend. The single-crospollen-sterile hybrid revealed, compared to the parental lines, an upward trend in its PPO and A activities before tasselling and a downward trend in the same enzymes after tasselling; while activity of P in this single-cross, pollen-sterile hybrid indicated the downward trend in general. Compared with the parental forms, the pollen-fertile hybrid of maize showed a trend towards lower activities of the studied enzymes for all seasons and periods under observation. Comparing results in the single-cross hybrids there was an indication of higher activities of PPO and A in the pollen-sterile analogue; whereas the same analogue revealed a lower activity of P before tasselling and higher value after tasselling.     

Inorganic and organic carbon dynamics in forested soils developed on contrasting geology in Slovenia—a stable isotope approach

Purpose

Soil carbon dynamics were studied at four different forest stands developed on bedrocks with contrasting geology in Slovenia: one plot on magmatic granodiorite bedrock (IG), two plots on carbonate bedrock in the karstic-dinaric area (CC and CD), and one situated on Pleistocene coalluvial terraces (FGS).

Materials and methods

Throughfall (TF) and soil water were collected monthly at each location from June to November during 2005–2007. In soil water, the following parameters were determined: T, pH, total alkalinity, concentrations of Ca²⁺ and Mg²⁺, dissolved organic carbon (DOC), and Cl^? as well as δ¹³C_DIC. On the other hand, in TF, only the Cl^? content was measured. Soil and plant samples were also collected at forest stands, and stable isotope measurements were performed in soil and plant organic carbon and total nitrogen and in carbonate rocks. The obtained data were used to calculate the dissolved inorganic carbon (DIC) and DOC fluxes. Statistic analyses were carried out to compare sites of different lithologies, at different spatial and temporal scales.

Results and discussion

Decomposition of soil organic matter (SOM) controlled by the climate can explain the ¹³C and ¹⁵?N enrichment in SOM at CC, CD, and FGS, while the soil microbial biomass makes an important contribution to the SOM at IG. The loss of DOC at a soil depth of 5 cm was estimated at 1 mol m^?2 year^?1 and shows no significant differences among the study sites. The DOC fluxes were mainly controlled by physical factors, most notably sorption dynamics, and microbial–DOC relationships. The pH and pCO₂ of the soil solution controlled the DIC fluxes according to carbonate equilibrium reactions. An increased exchange between DIC and atmospheric air was observed for samples from non-carbonate subsoils (IG and FGS). In addition, higher δ¹³C_DIC values up to ?19.4?‰ in the shallow soil water were recorded during the summer as a consequence of isotopic fractionation induced by molecular diffusion of soil CO₂. The δ¹³C_DIC values also suggest that half of the DIC derives from soil CO₂ indicating that 2 to 5 mol m^?2 year^?1 of carbon is lost in the form of dissolved inorganic carbon at CC and CD after carbonate dissolution.

Conclusions

Major difference in soil carbon dynamics between the four forest ecosystems is a result of the combined influence of bedrock geology, soil texture, and the sources of SOM. Water flux was a critical parameter in quantifying carbon depletion rates in dissolved organic and inorganic carbon forms.

     

Throughfall quality and quantity in polluted and damaged ecosystems in Northern Bohemia

The interaction between high concentrations of polluting gases (SO₂ and NO_x) and damaged forest ecosystems was observed by studying throughfall precipitation in the Erzegebirge Mountains, Northern Bohemia. Qualitative and quantitative data on throughfall for the period November 1989–October 1990 are presented. Weighted averages of SO ₄ ^2? and NO ₃ ^? concentrations in the throughfall were 23.05 mg L^?1 and 13.61 mg L^?1 in a beech and 34.41 mg L^?1 and 11.03 mg L^?1 in a spruce forest respectively. Three variables (the molar ratios of K/Na, N_tot/S and N-NO₃/N-NE₄) were used to compare the spruce throughfall quality to that observed in areas with similar however, less damaged spruce stands. Both K/Na and N-NO₃/N-NH₄ ratios clearly decreased with increasing tree damage, the N_tot/S ratio increased. The results suggest that the throughfall in damaged ecosystems of the Erzegebirge region becomes more like a wet precipitation as the tree canopies get sparser and the trees reduce canopy leaching.     

The sensitivity of water extractable soil organic carbon fractions to land use in three soil types

Soil organic carbon (SOC) has a high impact on the sustainability of ecosystems, global environmental processes, soil quality and agriculture. Long-term tillage usually leads to SOC depletion. The purpose of this study was to determine the impact of different land uses on water extractable organic carbon (WEOC) fractions and to evaluate the interaction between the WEOC fractions and other soil properties. Using an extraction procedure at 20°C and 80°C, two fractions were obtained: a cold water extractable organic carbon (CWEOC) and a hot water extractable organic carbon (HWEOC). The results suggest that there is a significant impact from different land uses on WEOC. A lower relative contribution of WEOC in SOC and a lower concentration of labile WEOC fractions are contained in arable soil compared to forestlands. Chernozem soil was characterized by a lower relative contribution of WEOC to the SOC and thus higher SOC stability in contrast to Solonetz and Vertisol soils. Both CWEOC and HWEOC are highly associated with SOC in the silt and clay fraction (<53 µm) and were slightly associated with SOC in the macroaggregate classes. The WEOC fractions were highly and positively correlated with the SOC and mean weight diameter.     

Immediate Impact of the Flood (Bohemia, August 2002) on Selected Soil Characteristics

In August 2002 extreme floods affected Bohemia a part of the Czech Republic, along Vltava and Labe rivers. After the flood had culminated, soil samples of arable and meadow soil (flooded and control-non-flooded) have been collected in the surroundings of the cities of ?eské Budějovice (CB, South Bohemia, the Vltava river, the upper flood stream) and Ústí nad Labem (UL, the Labe river, the lower flood stream). Different parameters of arable soils have been affected more significantly than those of meadow soils. Soil texture e.g. has been shifted from sandy loam to loam (CB) and clay loam (UL). Organic carbon, total phosphorus and nitrogen contents have been increased as well as the content of some hazardous elements such as arsenic. A shift of soil pH from 6.1 to 4.8 has been noticed in CB and an opposite one from 5.1 to 7.1 was measured in UL. Available phosphorus decreased in CB by 56% while a four-fold increase was measured in UL. Chlorinated organic pesticides level was significantly reduced, but that of polycyclic aromatic hydrocarbons (PAH) increased up to the maximum values of legal limits. The UL arable soil also became heavily contaminated by PAH. The CB arable soil demonstrated high microbial activity, while UL arable soil suffered under stress conditions in this respect. The flooded meadow soils became covered with a layer of drifted soil sediment, which retained enhanced content of the PAH's different hazardous elements, and, in addition, the soil aeration was reduced.     

Composition rather than viscosity modifies the aroma compound retention of flavored stirred yogurt

The influence of thickening agents (modified starch/pectin mixture 0 and 7 g/L) and mechanical treatment (low, medium, and high) on the retention of esters (pentyl acetate and ethyl pentanoate), aldehydes (hexanal and (E)-2-hexenal), and a lactone (gamma-octalactone) in low-fat flavored stirred yogurts were investigated under equilibrium conditions. In the range studied, the thickening agent and mechanical treatment had little influence on aroma compound retention compared to the decreasing effect of increasing dairy protein concentration on aldehyde retention and the "salting out" effect of carbohydrates on esters. Moreover, experiments in dynamic mode (study of the release of hexanal when yogurts were heated) showed, in the conditions studied, that heat and mass transfer coefficients were not influenced by any of the studied factors (thickening agents and mechanical treatment). These results under static and dynamic conditions are not related to the significant decreasing effect of thickening agents on apple sensory scores associated with hexanal, observed in a previous sensory study. Thus, this sensory effect of thickening agents may be due to sensory interactions between perceptions rather than physicochemical interactions.     

Phosphorus-use efficiency of kale genotypes from coastal Croatia

Understanding the mechanisms of phosphorus (P)-use efficiency (PUE) may contribute to enhancing crop P nutrition because species growth variability at low-P is well known. The experiment was carried out to evaluate the response of kale genotypes to different P supply in randomized block design in three replications. Low-P supply led to a decrease in most parameters, whereas an increase was recorded in root growth parameters. Genotypes differed in shoot dry weight (DW), leaf area, root length and area, and shoot and root P content and concentration. Root traits significantly positively correlated with PUE. Genotypes Red Russian (RR) and IJK 17 were superior in terms of shoot DW production at low P supply, and had the highest uptake efficiency. Genotypes IJK 17 and 81 had the highest P utilization efficiency, while Vates blue curled (VBC) showed the lowest PUE. Genotypes had similar shoot P content and concentration at low P supply, but large PUE differences, implying the importance of P utilization efficiency.     

N. I. Vavilov — Persönlichkeit und Mensch

Ohne Zusammenfassung     

Hepatoprotective and TNF-α inhibitory activity of Zosima absinthifolia extracts and coumarins

Zosima absinthifolia (ZA) extracts and the coumarins (+)-columbianadin and (-)-deltoin were evaluated for their potential hepatoprotective and antiinflamatory effects in a CCl(4)-induced hepatotoxicity assay in rats and by the inhibition of TNF-α production on LPS-stimulated THP-1 macrophages, respectively. Both the ZA extracts and the coumarins showed hepatoprotective activity confirmed by monitoring the ALT/AST levels and by histopathological examination. The antiinflamatory activity, proved by the inhibition of TNF-α production, was found to be higher for the n-hexane root extract than for coumarins, suggesting synergic potential of the extract. The concentration of (-)-deltoin and (+)-columbianadin in extracts was determined by HPLC analysis.     

Trade-off between height growth and spring flushing in common beech (<Emphasis Type="Italic">Fagus sylvatica</Emphasis> L.)

• Introduction   

The annual development cycle of boreal and temperate trees results from an evolutionary trade-off between two opposing forces. These are namely, the adjustment of leaf phenology to the timing of frost occurrence at the beginning and/or the end of the growth season countered by an effective adjustment to the duration of the growth season to maximise photosynthesis and biomass production during the growing season.