Mesophyll conductance (gm) is essential to determine accurate physiological parameters used to model photosynthesis in forest ecosystems. This study aimed to determine the effects of time of day on photosynthetic parameters, and to assess the effect of using either intercellular CO2 concentration (Ci) or chloroplast CO2 concentration (Cc), on maximum carboxylation velocity of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), Vcmax. We used Amazonian saplings of Myrcia paivae and Minquartia guianensis. Photosynthetic parameters were measured using an infrared gas analyzer (IRGA); gm was determined using both gas exchange and chlorophyll (Chl) a fluorescence and gas-exchange data alone. Leaf thickness (LT) and specific leaf area (SLA) were also measured. Air temperature, relative humidity or understory light did not correlate with gm and on average daily IRGA-fluorometer-determined gm was 0.04 mol(CO2) m-2 s-1 for M. paivae and 0.05 mol(CO2) m-2 s-1 for M. guianensis. Stomatal conductance (gs), gm, electron transport rate (JF), and light-saturated net photosynthetic rate (PNmax) were lower in the afternoon than in the morning. However, no effect of time of day was observed on Vcmax. LT and SLA did not affect any of the examined parameters.
IRGA-determined g m was almost the double of the value obtained using the IRGA-fluorescence method. Vcmax values determined using Cc were about 25% higher than those obtained using Ci, which highlighted the importance of using Cc in Vcmax calculation. Decline in PNmax at the end of the afternoon reflected variations in gs and gm rather than changes in Vcmax. Diurnal variation in gm appeared to be associated more with endogenous than with atmospheric factors. and H. C. S. Nascimento, R. A. Marenco.
The elected large cave spider Meta me nar - di occurs throughout the Palaearctic re - gion. In Central Europe, it is usually found in upland regions, and is particularly common in karst areas. The spider lives in subterranean caves, cellars, mineshafts and stone runs. and Milan Řezáč.
The Asian ladybird Harmonia axyridis is an invasive insect in Europe and the Americas and is a great threat to the environment in invaded areas. The situation is exacerbated by the fact that non native species are resistant to many groups of parasites that attack native insects. However, very little is known about the complex microbial community associated with this insect. This study based on sequencing 16S rRNA genes in extracted metagenomic DNA is the first research on the bacterial flora associated with H. axyridis. Lady beetles were collected during hibernation from wind turbines in Poland. A mean ± SD of 114 ± 35 species of bacteria were identified. The dominant phyla of bacteria recorded associated with H. axyridis were Actinobacteria, Proteobacteria, Firmicutes and Bacteroidetes. Representatives of these phyla are common in the environment, e.g. in the soil, and are often identified as the dominant bacteria associated with arthropods. We also identified animal pathogenic bacteria, such as Burkholderia, Rhodococcus, Chlamydiae and Anaplasmataceae spp. (Neorickettsia helminthoeca and Ehrlichia ovina). We also identified Wolbachia pipientis in a single beetle. This bacterium is a causative agent of reproductive alterations in arthropods. These results support the enemy release hypothesis in the case of this ladybird invasion. Pathogenic bacteria were recorded in only a few samples. Moreover, male-killing bacteria such as Spiroplasma spp., Wolbachia spp. and Rickettsia spp. were only recorded in single insects so they cannot be responsible for the observed alterations in the sex-ratio of the ladybird population studied., Krzysztof Dudek, Kinga Humińska, Jacek Wojciechowicz, Piotr Tryjanowski., and Obsahuje bibliografii
Při studiu interakcí bakterií a prvoků se používají zejména metody fluorescenční mikroskopie v kombinaci se značenými bakteriemi, nebo i vysoce specifické fluorescenčně značené RNA-sondy (fluorescence in situ hydridizace), které umožňují i přesnou taxonomickou identifikaci druhů bakterií, pohlcovaných prvoky. Můžeme tak studovat nejenom rychlost, ale i selektivitu eliminace bakterií heterotrofními a mixotrofními bičíkovci a nálevníky v různých přírodních vodách., Trophic interaction between bacteria and protozoa is mainly studied by means of fluorescence microscopy exploiting various fluorescence labelling of bacteria, including highly specific RNA-probes for fluorescence in situ hybridization, which allows precise identification of bacterial species grazed by protozoa. By combining these approaches we can examine not only the total rate of protozoan bacterivory, but also the grazing selectivity of heterotrophic and mixotrophic flagellates and ciliates feeding on bacteria in a broad array of aquatic ecosystems., Karel Šimek., and autor: Redakce a Karel Šimek
In November 2009, the United Nations declared 2010 to be the International Year of Biodiversity. It has been a celebration of life on earth and of the value of biodiversity for our lives. The world has been invited to take action in 2010 to safeguard biodiversity, i. e., the variety of life on earth. Throughout the year countless initiatives were organized to disseminate information, promote the protection of biodiversity and encourage organizations, institutions, companies and individuals to take direct action to reduce the constant loss of biological diversity worldwide. and Petr Petřík.