Small-scale and regional spatial dynamics of an annual plant with contrasting sexual systems

Plant demography is known to depend on both spatial dynamics and life history, but how these two factors interact is poorly understood. We conducted a longitudinal study of the wind-pollinated annual plant Mercurialis annua that varies geographically in its sexual system to investigate this interaction. Metapopulation demographic models predict that regular population turnover should be a more common feature of monomorphic than dimorphic populations because males and females cannot found new populations by selfing but hermaphrodites can. We tested the prediction that rates of population turnover would be higher in monomorphic compared to dimorphic regions. We surveyed 356 populations of M. annua along five regional transects in Morocco and the Iberian Peninsula over a 3-year period to examine their demography and persistence. Each transect crossed a transition in the sexual system, from a monomorphic region where almost all populations were hermaphroditic to a dimorphic one in which most populations had separate sexes (males with females or hermaphrodites). As predicted, rates of local apparent extinctions (i.e., the disappearance of adult plants) were nearly 50% higher in monomorphic compared to dimorphic regions. Local extinctions appeared to be driven by changes in vegetation cover, with extinctions tending to occur in sites in which perennial cover also declined. This suggests that disturbance is a primary agent of local extinctions. We further examined the influence of regional dynamics on local demographic properties by investigating patterns of spatial autocorrelation in population density across years. We found positive spatial autocorrelations in plant densities within regions for both sexual systems. However, these positive autocorrelations extended over shorter distances in monomorphic regions, perhaps as a result of greater population flux in these regions. Synthesis. Our study shows that population dynamics may be influenced by processes acting at a range of spatial scales: within patches, across patches within sites, and across sites within regions, as well as by life-history variation. In Mercurialis annua, regional variation in apparent extinction rates is affected by life history and implicated in regulating the geographical distribution of populations with different sexual systems

THE CONTENT OF SENSORY ACTIVE COMPOUNDS AND FLAVOUR OF SEVERAL TYPES OF YOGURTS

Abstract VÍTOVÁ, E., BABÁK, L., MOKÁŇOVÁ, R., HÝSKOVÁ, E., ZEMANOVÁ, J.: The content of sensory active compounds and fl avour of several types of yogurts. Acta univ. agric. et silvic. Mendel. Brun., 2010, LVIII, No. 5, pp. 407-412 The aim of this work was to identify and quantify several sensory active compounds in various types of yogurts using gas chromatography and simultaneously to judge their infl uence on fl avour of yogurts using sensory analysis. In total 4 types of white and 10 types of fl avoured yogurts (creamy and low-fat) with various fl avourings, produced in Dairy Valašské Meziříčí, Ltd., were analysed. The highest content of sensory active compounds (P < 0.05) was found in strawberry yogurts, with high amount of ethyl butyrate. Excepting ethanol no signifi cant diff erences (P < 0.05) were found between low-fat and creamy varieties. The total content of sensory active compounds in white yogurts was signifi cantly (P < 0.05) lower than in fl avoured fruit types. The highest content was in low-fat and lowest in white bio yoghurts. Flavour of yogurts was evaluated sensorially using scale and ranking test. All creamy yogurt varieties were evaluated as signifi cantly (P < 0.05) more tasty than low-fat ones. Similarly in case of white yogurts creamy yogurts were evaluated as the most tasty and low-fat ones as the worst. Bio yogurts were evaluated equally tasty as classic yogurts with the same fat content. yogurt, fl avour, sensory active compounds, GC, SPME, sensory analysi

Biosorption of Cu, Zn and Pb by thermophilic bacteria – effect of biomass concentration on biosorption capacity

The aim of this work was to study the biosorption capacity of metals copper, lead and zinc by Geobacillus thermodenitrificans and Geobacillus thermocatenulatus. Solution of each metal was mixed with dry biomass and incubated at room temperature. The supernatant was taken and used for complexometric titration. The sorption capacity for Cu2+ was highest when using 0.5 g·l−1 Geobacillus thermodenitrificans (57 ± 4 mg·g−1). The sorption capacity rapidly decreases with increased concentrations. Similarly for Zn2+ ions, the highest sorption capacity was for biomass concentration 0.5 g·l−1 (18 ± 3 mg·g−1) and slowly decreases. For Pb2+ ions, the decrease is almost linear to the biomass concentration 2 g·l−1, i.e. from 117 ± 13 mg·g−1 to 53 ± 3 mg·g−1.The sorption capacity of Cu2+ ions was highest at the lowest biomass concentration of Geobacillus thermocatenulatus (65 ± 3 mg·g−1), then it sharply decreased and at concentration of biomass of 1 g·l−1 did not changed. In the case of Zn2+ ions, we could seen a moderate drop with the increasing concentration with the range of 24 ± 3 to 12.3 ± 0.4 mg·g−1. For Pb2+ ions was the decrease slow, from 119 ± 8 mg·g−1 to 54 ± 4 mg·g−1.Affinity of metals to bacteria was determined in the order Pb2+ > Cu2+ > Zn2+. The results show, that Geobacillus thermocatenulatus has better sorption capabilities than Geobacillus thermodenitrificans