How do bryophytes govern generative recruitment of vascular plants?

Interactions between vascular plants and bryophytes determine plant community composition in many ecosystems. Yet, little is known about the importance of interspecific differences between bryophytes with respect to their effects on vascular plants. We compared the extent to which species-specific bryophyte effects on vascular plant generative recruitment depend on the following underlying mechanisms: allelopathy, mechanical obstruction, soil moisture and temperature control. We sowed 10 vascular plant species into monospecific mats of six chemically and structurally diverse bryophytes, and examined 1-yr seedling recruitment. Allelopathic effects were also assessed in a laboratory phyto-assay. Although all bryophytes suppressed vascular plant regeneration, there were significant differences between the bryophyte species. The lack of interactions indicated the absence of species-specific adaptations of vascular plants for recruitment in bryophyte mats. Differences between bryophyte species were best explained by alterations in temperature regime under bryophyte mats, mostly by reduced temperature amplitudes during germination. The temperature regime under bryophyte mats was well predicted by species-specific bryophyte cushion thickness. The fitness of established seedlings was not affected by the presence of bryophytes. Our results suggest that climatically or anthropogenically driven changes in the species' composition of bryophyte communities have knock-on effects on vascular plant populations via generative reproduction.     

Synthesis and antioxidative activity of metalloporphyrins bearing 2,6-di-tert-butylphenol pendants

The novel metalloporphyrins (M = HH, Fe, Mn, Co, Cu, Zn) bearing 2,6-di-tert-butylphenol pendants as antioxidant substituents, and a long chain hydrocarbon palmitoyl group have been synthesized. The oxidation of compounds by PbO₂ leads to the formation of the corresponding 2,6-di-tert-butylphenoxyl radicals studied by EPR. The activity of porphyrins in lipid peroxidation has been examined using (1) in vitro lipid peroxidation induced by tert-butylhydroperoxide in respiring rat liver mitochondria, (2) in vitro lipid peroxidation in liver homogenates of Wistar strain rats, and (3) a model process of peroxidation of (Z)-octadec-9-enic (oleic) acid as a structural fragment of lipids. The activity of these compounds depends dramatically on the nature of metal and might be changed from antioxidative (M = HH, Mn, Cu, Zn) to indifferent (M = Co), and to pro-oxidative one (M = Fe). The anti- or pro-oxidative action of these compounds may be derived from the concurrence between the involvement of 2,6-di-tert-butylphenol pendants acting as radical scavengers and redox active metal center promoting oxidation processes. The results of this study suggest that the polytopic compounds combining in one molecule 2,6-di-tert-butylphenol pendants, metalloporphyrin moiety, and a palmitoyl group, are membrane active compounds and might be studied in an effort to find novel pharmaceutical agents.     

Monkey viral pathology in the Sukhum colony and modeling human viral infections

The data characterizing spontaneous infections of Old World monkeys: measles, poliomyelitis, hepatitis A (HPA), encephalomyocarditis, coronavirus infection, simian hemorrhagic fever (SHF), are presented. The experimental infections were reproduced with the isolated pathogens. On these models, pathogenesis and epidemiology of these diseases were studied. The efficiency of poliomyelitis, measles and HPA vaccines is shown. The priority of data on the discovery of earlier unknown disease—SHF and “Sukhumi” virus—are emphasized. Several important pathogenic mechanisms common for various hemorrhagic fevers were studied on experimental SHF of macaques. This model is uniquely safe and adequate for the assessment of therapy of hemorrhagic fevers dangerous for humans.     

reflection of stimulus orientation in reactions of visual cortex neurons

A mathematical model of neuronal target structure with spatial anisotropy of lateral inhibition is discussed. The positions of the neuronal target to oriented sensory stimuli are investigated by computer simulation. It is suggested that visual stimuli orientation is coded in the late phase of dynamic responses of cortical neurons. This idea is in agreement with the data obtained in experiments on guinea pig visual cortex neurons.     

The role of tetrapyrrol photosensitizers in photoinduced variation of free radical characteristics of rat blood in endotoxic shock

The main goal of the present study was to evaluate the comparative effectiveness of tetrapyrrol photosensitizers (protoporphyrine IX and chlorine e ₆) in red (632.8 nm) and green (532.5) spectrum bands on rat blood free radical status, using the experimental model of endotoxic shock. Endotoxic shock was produced by intraperitoneal injection of lipopolysaccharide B. Irradiation effectiveness was estimated by leukocyte activation (measured with luminol-dependent chemiluminescence), superoxide dismutase activity of blood plasma (nitro blue tetrasolium assay) and lipid peroxidation (assay with cis-parinaric acid). It was found that laser irradiation has multidirectional effects on leukocyte activation, membrane lipid peroxidation and plasma SOD activity and all these effects were more pronounced in the case of endotoxic shock. Protoporphyrin was more effective in leukocyte activation and chlorine e ₆ demonstrated maximal effects on blood SOD activity.     

Effects of long-term alleviation of nutrient limitation on shoot growth and foliar phenolics of Empetrum hermaphroditum

Alpine tundra ecosystems are characterised by low productivity, due in part to low nutrient availability. These ecosystems are often dominated by ‘stress tolerant’ species such as Empetrum hermaphroditum, which contribute to stress by producing and releasing biologically active phenolic compounds into the environment. In a nine‐year field experiment in alpine tundra, we investigated changes in growth and the levels (concentrations and contents) of foliar redox‐active phenolics of current‐year shoots of E. hermaphroditum in response to nine long‐term environmental manipulation treatments. The treatments were aimed at reducing ecological stresses commonly present in high‐latitude ecosystems, primarily stresses associated with low availability of N and other nutrients. Treatments included additions of various forms of N (single and combined applications of NH₄⁺ and NO₃^?, inorganic N as a component of a full nutrient treatment, and protein as a source of organic N), and additions of glucose, activated carbon, and lime. Shoot growth and levels of foliar phenolics varied greatly between years, but the variation was not clearly explained by the inter‐annual variation in macroclimate. Addition of inorganic N generally stimulated growth (especially stem biomass) and increased levels of leaf phenolics. The responses were, however, slow, and varied both between years and between individual inorganic N treatments. Compared to the other treatments, application of inorganic N as a component of a full nutrient treatment had the most consistent positive effect on shoot growth and phenolic content, but it did not affect the concentration of phenolics, suggesting that the treatment did not affect the net rate of phenolic production per unit shoot biomass. During some years of the experiment, the combined application of NH₄⁺ and NO₃^? resulted in increased production of phenolics per unit biomass accumulation. In contrast to inorganic N fertilisation, application of organic N generally reduced both shoot biomass and phenolic content. Non‐N treatments had no substantial effects on either the growth or levels of foliar phenolics of E. hermaphroditum. The observed long‐term responses of E. hermaphroditum to environmental manipulation treatments may be important for evaluating potential effects of variation in phenolics production and interference potential of this species under conditions of environmental change and for predicting long‐term responses of nutrient‐poor communities to environmental changes.     

The response of forest plant regeneration to temperature variation along a latitudinal gradient

Background and Aims

The response of forest herb regeneration from seed to temperature variations across latitudes was experimentally assessed in order to forecast the likely response of understorey community dynamics to climate warming.

Methods

Seeds of two characteristic forest plants (Anemone nemorosa and Milium effusum) were collected in natural populations along a latitudinal gradient from northern France to northern Sweden and exposed to three temperature regimes in growth chambers (first experiment). To test the importance of local adaptation, reciprocal transplants were also made of adult individuals that originated from the same populations in three common gardens located in southern, central and northern sites along the same gradient, and the resulting seeds were germinated (second experiment). Seedling establishment was quantified by measuring the timing and percentage of seedling emergence, and seedling biomass in both experiments.

Key Results

Spring warming increased emergence rates and seedling growth in the early-flowering forb A. nemorosa. Seedlings of the summer-flowering grass M. effusum originating from northern populations responded more strongly in terms of biomass growth to temperature than southern populations. The above-ground biomass of the seedlings of both species decreased with increasing latitude of origin, irrespective of whether seeds were collected from natural populations or from the common gardens. The emergence percentage decreased with increasing home-away distance in seeds from the transplant experiment, suggesting that the maternal plants were locally adapted.

Conclusions

Decreasing seedling emergence and growth were found from the centre to the northern edge of the distribution range for both species. Stronger responses to temperature variation in seedling growth of the grass M. effusum in the north may offer a way to cope with environmental change. The results further suggest that climate warming might differentially affect seedling establishment of understorey plants across their distribution range and thus alter future understorey plant dynamics.     

Revision of the European species of Omphale Haliday (Hymenoptera,Chalcidoidea, Eulophidae)

The European species of Omphale Haliday (Eulophidae: Entedoninae) are revised. The revision includes 37 species, of which eleven are newly described and the remaining 26 species are redescribed. The species are classified into six species groups, with six unplaced species. All species are fully diagnosed and thoroughly illustrated. Identification keys are provided for females and males. Two new morphological features to aid classification and identification are introduced: male genitalia and wing interference patterns (WIPs). The former has been used successfully in the classification of New World Omphale and the latter is used for the first time in a taxonomic revision. Male genitalia in Omphale have considerable interspecific variation, an unusual trait among chalcidoid Hymenoptera, and are demonstrated to be useful for classification of species and species-groups, and they also possess the only autapomorphy for Omphale. WIPs are useful to help separate some species, but cannot be used to define either the genus or species groups. Distributional data are compiled for each species and suggest a pan-european distribution for most species. Gall-midges are the known hosts for 14 species, and the absence of host overlap between species suggests that host specialization is a driving force for speciation. Several Omphale species are known only from females, or have a strong female biased sex ratio, suggesting thelytokous development. Apart from the 37 species included in this revision, the status for nine additional species (names) in species group aetius remain unsolved. For nomenclatorial stability, a neotype is designated for Eulophus lugens Nees (= Omphale lugens (Nees)). Elachestus obscurus Förster and Derostenus sulciscuta Thomson are transferred from Holcopelte to Omphale comb. n. Derostenus radialis Thomson and Achrysocharella americana Girault are synonymized with Omphale theana (Walker), and Omphale teresis Askew is synonymized with Omphale phruron (Walker), syn. n. The status of genus Pholema Graham is revised as it is removed from synonymy with Omphale and instead synonymized with Neochrysocharis Kurdjumov, syn. n., and the type species for Pholema, Pholema microstoma Graham, is transferred to Neochrysocharis, comb. n. Eugerium orbatum Szelényi, previously transferred to Omphale, is synonymized with Asecodes congruens (Nees), syn. n.