Influence Of Different Environmental Factors Research Articles

Photocontrol of Weeds

AbstractThe reduction of weed emergence resulting from night‐time tillage in worldwide conducted field trials was very variable. The efficacy of night‐time tillage ranged from a reduction of weed ground cover of 97.5 % to an increase in weed seedling emergence of 80 % compared with daytime tillage. In most of the field trials, the reduction in the weed density as a result of night‐time tillage was <30 %. Important factors affecting this variation were: (1) the different light sensitivity of weed species, (2) the different light sensitivity of populations within the same species, (3) the dormancy status of the seeds, (4) the seasonal and short‐term variation of light sensitivity of seeds, (5) the variation of soil water content and (6) the type of soil tillage implement used. Less important were the small light intensity during night‐time tillage which cannot be excluded, and the penetration of light into the soil the days following night‐time tillage. The influence of different environmental factors on the effect of photocontrol of weeds is rather unclear because there are presumably complex interactions between environmental factors and the light‐dependent germination of weed seeds under field conditions. However, some field trials indicate that dry soil conditions reduce the efficacy of photocontrol of weeds. Several trials in the literature suggest that photocontrol of weeds during daytime using implements with a light‐proof cover was as effective as night‐time tillage. This review summarizes the results in research of photocontrol of weeds (soil cultivation in darkness), particularly those derived from field trials. Moreover, important factors are discussed, which might influence the effect of photocontrol of weeds.

Essential oil composition and variability of Hypericum perforatum L. growing in Lithuania

The composition of essential oils obtained from flowers and leaves in 11 accessions of Hypericum perforatum L. was analysed by GC and GC–MS. All the analysed oils were dominated by their oxygenated sesquiterpene fraction. Differences were attributed to the main components: caryophyllene oxide, spathulenol and viridiflorol. There were only a few monoterpenes in essential oil of all accessions. The data indicated some differences in sesquiterpene and aliphatic hydrocarbons, as well as in oxygenated aliphatics biosynthesis in flowers and leaves. The concentrations of β-caryophyllene and caryophyllene oxide in essential oils from leaves were higher than those from flowers, whereas dodecanol, spathulenol, viridiflorol, carotol and tetradecanol were present in higher quantities in flowers. Cluster analysis of all identified components grouped oils from flowers and from leaves into three clusters that corresponded with their major components: caryophyllene oxide, tetradecanal, tetradecanol and manool. Chemical variability of the analysed accessions seems likely to result from the genetic variability, since the influence of different environmental factors has been eliminated.

Experimental Native Tree Seedling Establishment for the Restoration of a Mexican Cloud Forest

Abstract The cloud forests of Mexico have been degraded and severely fragmented, and urgently require restoration. However, progress with restoration has been constrained by a lack of information concerning the seedling ecology of native tree species. An experiment was therefore conducted to assess the influence of different environmental factors on the seedling survival and growth of four native tree species (Fagus grandifolia var. mexicana, Carpinus caroliniana, Symplocos coccinea, and Quercus acutifolia). The seedlings were established on three sites, in two contrasting environments: inside forest fragments and on adjacent agricultural land. Highly significant differences were recorded in seedling survival and growth among sites, environments, species, and interactions between these factors. Highest survival was recorded for Quercus, which uniquely among the four species displayed the same survival percentage inside and outside the forest. Survival of the other species was higher inside the forest. In contrast, growth rates of all four species were higher outside the forest. The most important cause of mortality outside the forest was desiccation, although significant seedling predation was also observed on two sites. Results indicate that all four species can be established successfully both within forest fragments and in neighboring agricultural areas, emphasizing the scope for forest restoration. However, the interactions observed between species, sites, and environments highlight the importance of accurate species–site matching if optimum rates of growth and survival are to be obtained. Quercus spp. have great potential for establishment on agricultural sites.

Environmental factors influencing attenuation of methane and hydrochlorofluorocarbons in landfill cover soils.

The influence of different environmental factors on methane oxidation and degradation of hydrochlorofluorocarbons (HCFCs) was investigated in microcosms containing soil sampled at Skellingsted Landfill, Denmark. The soil showed a high capacity for methane oxidation resulting in a maximum oxidation rate of 104 microg CH4 g(-1) h(-1) and a low affinity of methane with a half-saturation constant of 2.0% v/v. The hydrochlorofluorocarbons HCFC-21 (dichlorofluoromethane) and HCFC-22 (chlorodifluoromethane) were rapidly oxidized and the oxidation occurred in parallel with the oxidation of methane. The maximal HCFC oxidation rates were 0.95 and 0.68 microg g(-1) h(-1) for HCFC-21 and HCFC-22, respectively. Increasing concentrations of HCFCs resulted in decreased methane oxidation rates. However, compared with typical concentrations in landfill gas, relatively high HCFC concentrations were needed to obtain a significant inhibition of methane oxidation. In general, the environmental factors studied influenced the degradation of HCFCs in almost the same way as they influenced methane oxidation. Temperature had a strong influence on the methanotrophic activity giving high Q10 values of 3.4 to 4.1 over the temperature range of 2 to 25 degrees C. Temperature optimum was around 30 degrees C; however, oxidation occurred at temperatures as low as 2 degrees C. A moisture content of 25% w/w yielded the maximum oxidation rate as it allowed good gas transport together with sufficient microbial activity. The optimum pH was around neutrality (pH = 6.5-7.5) showing that the methanotrophs were optimally adapted to the in situ pH, which was 6.9. Copper showed no inhibitory effect when added in relatively high concentrations (up to 60 mg kg(-1)), most likely due to sorption of copper ions to soil particles. At higher copper concentrations the oxidation rates decreased. The oxidation rates for methane, HCFC-21, and HCFC-22 were unaltered in ammonium-amended soil up to 14 mg kg(-1). Higher ammonium concentrations inhibited the oxidation process. The most important parameters controlling oxidation in landfill cover soil were found to be temperature, soil moisture, and methane and oxygen supply.

Environmental Factors Influencing Attenuation of Methane and Hydrochlorofluorocarbons in Landfill Cover Soils

The influence of different environmental factors on methane oxidation and degradation of hydrochlorofluorocarbons (HCFCs) was investigated in microcosms containing soil sampled at Skellingsted Landfill, Denmark. The soil showed a high capacity for methane oxidation resulting in a maximum oxidation rate of 104 μg CH4 g−1 h−1 and a low affinity of methane with a half-saturation constant of 2.0% v/v. The hydrochlorofluorocarbons HCFC-21 (dichlorofluoromethane) and HCFC-22 (chlorodifluoromethane) were rapidly oxidized and the oxidation occurred in parallel with the oxidation of methane. The maximal HCFC oxidation rates were 0.95 and 0.68 μg g−1 h−1 for HCFC-21 and HCFC-22, respectively. Increasing concentrations of HCFCs resulted in decreased methane oxidation rates. However, compared with typical concentrations in landfill gas, relatively high HCFC concentrations were needed to obtain a significant inhibition of methane oxidation. In general, the environmental factors studied influenced the degradation of HCFCs in almost the same way as they influenced methane oxidation. Temperature had a strong influence on the methanotrophic activity giving high Q10 values of 3.4 to 4.1 over the temperature range of 2 to 25°C. Temperature optimum was around 30°C; however, oxidation occurred at temperatures as low as 2°C. A moisture content of 25% w/w yielded the maximum oxidation rate as it allowed good gas transport together with sufficient microbial activity. The optimum pH was around neutrality (pH = 6.5–7.5) showing that the methanotrophs were optimally adapted to the in situ pH, which was 6.9. Copper showed no inhibitory effect when added in relatively high concentrations (up to 60 mg kg−1), most likely due to sorption of copper ions to soil particles. At higher copper concentrations the oxidation rates decreased. The oxidation rates for methane, HCFC-21, and HCFC-22 were unaltered in ammonium-amended soil up to 14 mg kg−1 Higher ammonium concentrations inhibited the oxidation process. The most important parameters controlling oxidation in landfill cover soil were found to be temperature, soil moisture, and methane and oxygen supply.

Säkularer Trend bei der Körperhöhe seit dem Neolithikum

The body height of children and adults is estimated on the basis of skeleton material from the middle Elbe-Saale region since the Neolithic period. The men's body height was calculated according to Breitinger (1938), the women's body height according to Bach (1965), and the children's body height according to Telkkä et al. (1962). These estimates are compared with the mean body height of living persons from the adult population and of Jena schoolchildren, respectively. These are the following essential results: 1. Since 7000 years ago changes of body height can be observed. There was an increase of the mean body height from the Neolithic period until the Bronce age. In the A.D. era no clear changes of the average values can be found until about the 12th century, after which there occurred decreases seen until the 19th century. 2. The greatest secular trends in children and adults arise in our century. 3. The influence of different environmental factors on the body height in past and present is discussed and the sex-specific reactions to changes of these environmental factors are described. 4. It is pointed out that social, and/or geographic influences can cause changes of the body height calculated from skeleton material.

Test facility in Port Said-Egypt for photovoltaic solar generators

In framework of an applied research project a test facility for evaluating the performance of photovoltaic (PV) solar generators has been implemented at the Faculty of Engineering in Port Said-Egypt. The goals of the project is to perform the different required tests on photovoltaic (PV) solar generators in order to verify the fulfillment of the international standard specifications and to verify the characteristics given by the manufacturer. This will be achieved determining the electrical, the thermal and the mechanical characteristics of the module. This test can be considered to be a preparation for Egyptian PV market helping for propagation and harmonisation of standards. The developed test facility is including the main tests of PV systems, e.g. the electrical output under normal operating conditions and the influence of different environmental factors.

Associations d'Ostracodes et paléoenvironnements au passage cénomanien-turonien dans les régions d'Agadir (Haut Atlas) et de Boulmane (Moyen Atlas), Maroc

The stratigraphic and sedimentological study of two sections in the Agadir (High Atlas) and Boulmane (Middle Atlas, Morocco) regions, and the examination of ostracod associations reveal the palaeoenvironments at the Cenomanian-Turonian boundary and specify the influence of different environmental factors on ostracod populations. Ostracod polymorphism appears to reflect adaptative strategies in response to environmental modifications. Cladogenetic and anagenetic polymorphism developed within Oertliella? tarfayaensis and Veenia (Nigeria) rotunda species respectively.

Influence of Larval Rearing Conditions on the Body Size and Flight Capacity of Epiphyas-Postvittana Moths

Effects of rearing conditions of larvae on the body weight and flight duration of the light brown apple moth, Epiphyas postvittana (Walker), were evaluated in the laboratory. The body weight of both male and female moths at emergence decreased with increasing temperature from 15 to 28-degrees-C during larval stages; in contrast, flight duration increased with rising temperature. There was no effect of larval density on flight duration, although the body weight of moths decreased as density increased. Variation in water content of artificial diet showed a significant influence on flight duration of female moths, but not on body weight in either sex. Flight duration was different only for females when their larvae were reared on young leaves of four host plants. Female moths from larvae on Rumex crispus and Plantago lanceolata flew for significantly longer periods than those from larvae on Trifolium repens and Pyrus malus. Larvae fed on young leaves yielded adults that flew for longer periods than those fed on senescent leaves. Inconsistency in relationships between body weight and flight duration of moths with respect to influences of different environmental factors during the larval stages indicates that flight capacity is unlikely to be influenced by body size in this species.

Studies on the evaluation of preservative efficacy ∗: III. The determination of antimicrobial characteristics of benzalkonium chloride

Aspergillus niger, Candida albicans, Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus were used as test organisms for the study of preservation efficacy of benzalkonium chloride alone, or in combination with 0.1% EDTA. The influence of different environmental factors, such as the pH of the solution and the temperature and the concentration of the preservative, on the antimicrobial activity of benzalkonium chloride were also investigated. D-value, activation energy ( E a ), temperature coefficient ( Q 10) and concentration exponent (η) were used as parameters in determining the preservative effect. The results showed that the kinetic approach to the screening of the antimicrobial activity of benzalkonium chloride — a quaternary ammonium compound — is feasible and appropriate.