Variability and Bimodal Distribution of Size in Microspores of Aesculus hippocastanum

Size variability of uninucleate microspores was studied in horse chestnut (Aesculus hippocastanum L.). Microspores were isolated from buds of different size (3, 4, and 5 mm) taken from lower, middle and upper segments of inflorescences. All analyzed buds showed bimodal distribution of microspore size which confirmed the presence of pollen dimorphism. This revised version was published online in July 2006 with corrections to the Cover Date.     

Zinc or Magnesium Supplementation Modulates Cd Intoxication in Blood,Kidney, Spleen,and Bone of Rabbits

The objective of this study was to examine the influence of oral supplementation with Zn or Mg on Cd content in the blood and organs of rabbits exposed to prolonged Cd intoxication. Rabbits were divided into the following groups: Cd group-received orally every day for 4 weeks 10 mg Cd/kg body weight (b.w.), Cd+Zn group and Cd+Mg group-exposed to Cd and supplemented with 20 mg Zn/kg b.w. or 40 mg Mg/kg b.w. 1 h after Cd treatment. Cd content in biological material was determined by atomic absorption spectrophotometry. Blood Cd concentration was determined in all investigated groups at time 0 and after 10, 14, 18, 22, 25, and 28 days, whereas Cd content in the brain, heart, lungs, liver, kidney, spleen, pancreas, skeletal muscle, and bone was determined after 28 days. Blood Cd concentration was significantly increased in all groups from the 14th day of Cd intoxication and lasted till the end of the experiment. Zn or Mg supplementation significantly reduced blood Cd content on the 18th and 25th days. Supplementation with Zn or Mg significantly decreased Cd concentration in the kidney, spleen, and bone and, in addition, Zn reduced Cd content in the brain. Supplementation with Zn or Mg in Cd-intoxicated rabbits caused similar reduction of blood Cd concentration; however, reduction of tissue Cd content was more pronounced in Zn- than in Mg-supplemented group.     

Age‐related parasite load and longevity patterns in the sedge warbler Acrocephalus schoenobaenus

We report the results from a nine‐year study on parasite infection in males of a small migrant passerine, the sedge warbler Acrocephalus schoenobaenus. Every year, for each male caught during territory establishment we estimated infection intensity of two lineages of Haemoproteus belopolskyi (SW1 and SW3), using molecular methods. We found a significant relationship between infection intensity and males’ longevity in both studied lineages. There was severe mortality of second‐year sedge warblers after their first breeding season, with lower parasite load in survivors. The lower infection intensity in older age classes was related to between‐individual change in both lineages, but was also a result of differences in infection intensity during the lifetime of individual males in the SW3. The relation between parasite load and longevity suggests that parasite load may be an age‐dependent factor influencing individual survival.     

Phylogenetic similarity and structure of Agaricomycotina communities across a forested landscape

The Agaricomycotina are a phylogenetically diverse group of fungi that includes both saprotrophic and mycorrhizal species, and that form species – rich communities in forest ecosystems. Most species are infrequently observed, and this hampers assessment of the role that environmental heterogeneity plays in determining local community composition and in driving β‐diversity. We used a combination of phenetic (TRFLP) and phylogenetic approaches [Unifrac and Net Relatedness Index (NRI)] to examine the compositional and phylogenetic similarity of Agaricomycotina communities in forest floor and surface soil of three widely distributed temperate upland forest ecosystems (one, xeric oak – dominated and two, mesic sugar maple dominated). Generally, forest floor and soil communities had similar phylogenetic diversity, but there was little overlap of species or evolutionary lineages between these two horizons. Forest floor communities were dominated by saprotrophic species, and were compositionally and phylogenetically similar in all three ecosystems. Mycorrhizal species represented 30% to 90% of soil community diversity, and these communities differed compositionally and phylogenetically between ecosystems. Estimates of NRI revealed significant phylogenetic clustering in both the forest floor and soil communities of only the xeric oak‐dominated forest ecosystem, and may indicate that this ecosystem acts as a habitat filter. Our results suggest that environmental heterogeneity strongly influences the phylogenetic β‐diversity of soil inhabiting Agaricomycotina communities, but has only a small influence on forest floor β‐diversity. Moreover, our results suggest that the strength of community assembly processes, such as habitat filtering, may differ between temperate forest ecosystems.     

The SGNH-hydrolase of Streptomyces coelicolor has (aryl)esterase and a true lipase activity

The Streptomyces coelicolor A3(2) gene SCI11.14c was overexpressed and purified as a His-tagged protein from heterologous host, Streptomyces lividans. The purification procedure resulted in 34.1-fold increase in specific activity with an overall yield of 21.4%. Biochemical and physical properties of the purified enzyme were investigated and it was shown that it possesses (aryl)esterase and a true lipase activity. The enzyme was able to hydrolyze p-nitrophenyl-, α- and β-naphthyl esters and poly(oxyethylene) sorbitan monoesters (Tween 20–80). It showed pronounced activity towards p-nitrophenyl and α- and β-naphthyl esters of C₁₂–C₁₆. Higher activity was observed with α-naphthyl esters. The enzyme hydrolyzed triolein (specific activity: 91.9 U/mg) and a wide range of oils with a preference for those having higher content of linoleic or oleic acid (C18:2; C18:1, cis). The active-site serine specific inhibitor 3,4-dichloroisocoumarin (DCI) strongly inhibited the enzyme, while tetrahydrofurane and 1,4-dioxane significantly increased (2- and 4- fold, respectively) hydrolytic activity of lipase towards p-nitrophenyl caprylate. The enzyme exhibited relatively high temperature optimum (55 °C) and thermal stability. CD analysis revealed predominance of α-helical structure (54% α-helix, 21% β-sheet) and a T_m value at 66 °C.     

What do we know about salt stress in bryophytes?

Bryophytes are among the first plants that faced the terrestrial way of life. They settled almost all terrestrial habitats, but no extant seawater representatives are known. It is not widely documented how bryophytes cope with salt stress, but there are species inhabiting salty environments. Here, we present the current state of knowledge on salt stress biology in bryophytes.     

Antioxidant and Sensorial Properties of Linden Honey with Dried Apricots

The total phenol (TPh) and flavonoid contents (TFd), and antioxidant and sensorial properties of linden honey (LH) with dried apricots (20, 30, and 40%) were evaluated. TPh increased 4.3 times for LH40 (from 23.96 to 102.87 mg gallic acid equiv./100 g honey), while increase of TFd was slightly lower, ca. 2.9‐fold for LH40 (from 18.11 to 51.72 mg rutin equiv./100 g honey). Based on HPLC analysis, the most dominant phenolic compound was gallic acid (11.14 mg/100 g honey in LH and 42.65 mg/100 g honey in LH40). In three different assays, the antioxidant activity increased with increasing concentration of apricots in honey. The values varied from 13.36 for LH to 7.06 mg/ml for LH40; the values ranged from 189.83 for LH to 11.23 mg/ml for LH40; the RP_0.5 (reducing power) values ranged from 169.00 for LH to 27.60 mg/ml for LH40. Based on the correlation analysis, it is obvious that TPh and TFd were associated with the antioxidant activities of honey samples. A high degree of correlation existed between antioxidant activities of honey samples and TPh (R from 0.945 to 0.996) and TFd (R from 0.805 to 0.934). Obtained scores for individual sensory properties indicated very good quality of honey with dried apricots.     

Admixture facilitates adaptation from standing variation in the European aspen (Populus tremula L.), a widespread forest tree

Adaptation to new environments can start from new mutations or from standing variation already present in natural populations. Whether admixture constrains or facilitates adaptation from standing variation is largely unknown, especially in ecological keystone or foundation species. We examined patterns of neutral and adaptive population divergence in Populus tremula L., a widespread forest tree, using mapped molecular genetic markers. We detected the genetic signature of postglacial admixture between a Western and an Eastern lineage of P. tremula in Scandinavia, an area suspected to represent a zone of postglacial contact for many species of animals and plants. Stringent divergence‐based neutrality tests provided clear indications for locally varying selection at the European scale. Six of 12 polymorphisms under selection were located less than 1 kb away from the nearest gene predicted by the Populus trichocarpa genome sequence. Few of these loci exhibited a signature of ‘selective sweeps’ in diversity‐based tests, which is to be expected if adaptation occurs primarily from standing variation. In Scandinavia, admixture explained genomic patterns of ancestry and the nature of clinal variation and strength of selection for bud set, a phenological trait of great adaptive significance in temperate trees, measured in a common garden trial. Our data provide a hitherto missing direct link between past range shifts because of climatic oscillations, and levels of standing variation currently available for selection and adaptation in a terrestrial foundation species.