Structure and pattern in temperate seasonal forests

Demography, spatial pattern, and diversity of canopy and subcanopy trees, shrubs, and lianas were compared in two cool and two warm temperate North American forests, paired at 30° and 40° north latitudes. All woody stems 1 cm dbh in 16 randomly located, non-contiguous plots totalling 1 ha at each of the four sites were measured, mapped, and identified. Basal area and overall density did not differ between latitudes. Demographic and spatial analyses revealed remarkable similarity in spatial dispersion, irrespective of density or species composition. At all sites, dispersion of canopy trees was random but all understory stems were uniformly distributed relative to all canopy trees. Species diversity and vertical structure differed between the warm and cool temperate sites, especially in species composition of individual strata. Associations of understory species relative to canopy species were more random at 30° than at 40° north, where a higher degree of association between canopy and understory species' patterns, coupled with their size class distributions, suggested more lengthy regeneration cycles and an alternation of species assemblages. The forests at 30°, those subject to periodic canopy disturbance by hurricanes, had more vertical mixing of species (i.e., canopy species represented in all size classes), more tree saplings, and significantly more shrub and liana species.     

The resistance of tubificid worms to three common pollutants

Summary Tubificid worms have been shown to be quite tolerant to toxic materials such as lead, phenol, and zinc. Their median tolerance limit (Tl_m) for pH levels in modified Knop solution has been shown to be 5.8 to 9.7. Their Tl_m for lead was 49.0 pp, at pH 6.5 and 27.5 at a pH of 8.5. For sodium pentochlorophenate (PCP) the Tl_m was found to be 0.31 ppm at pH 7.5, 0.67 ppm at pH 8.6 and 1.4 ppm at pH 9.5. The Tl_m determined for zinc was 46.0 ppm at pH 7.5. The interactions of pH and these substances has been examined and discussed, and the importance of definition of the solution has been shown. The mechanism of toxicity for lead and zinc probably is the mucousmetal complex which precipitates on the body wall blocking the exchange of oxygen and carbon dioxide. This is similar to the reaction of these metals observed in the gills of fish. The toxic mechanism of PCP is possibly a biochemical interruption of oxidative phosphorylation. It is not a mucous-effecting mechanism because no mucous precipitate forms as with the metals. In each instance these experiments show tubificids with a quantitative resistance to lead, zinc and phenol greater than similar resistance recorded for various fish species. This provides a basis for quantitative evaluation of the resistant nature of these organisms that may be valuable in future studies of their association to polluted habitats.

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Zusammenfassung Tubificiden haben sich giftigen Materialen wie Blei, Phenyl-säure und Zink gegenüber ziemlich duldsam gezeigt. Ihre Durchschnitts-Duldsamkeitsgrenze (Tl_m) für pH Werte in modifizierter Knop-Lösung sind, wie gezeigt wurde, 5.8 bis 9.7. Ihre Tl_m für Blei war 49.0 ppm bei pH 6.5 and 27.5 bei pH 8.5. Es wurde gefunden, dass das Tl_m für Natrium Pentochlorophenate (PCP) 0.31 ppm bei pH 7.5, 0.67 ppm bei pH 8.5 und 1.4 ppm bei pH 9.5 war. Die festgestellte Tl_m für Zink war 46.0 ppm bei pH 7.5. Die Wechselwirkungen von pH and diesen Substanzen sind geprüft and diskutiert worden und die Wichtigkeit von Erklärung der Auflösung gezeigt. Der Giftigkeits-Mechanismus für Blei and Zink is wahrscheinlich der Schleim-Metall-Komplex, der, den Austausch von Sauerstoff und Kohlenstoffdioxyd blockend, an der Körperwand verflüssigt. Dieses ähnelt der Gegenwirkung der beobachteten Metalle in den Kiemen von Fischen. Der Gift-Mechanismus von PCP ist möhcherweise eine biochemische Unterbrechung sauerstoffartiger Phosphorilation. Es ist kein Schleim-wirkender Mechanismus, weil sich kein Schleim-Präpicitat formt wie bei den Metallen. In jedem Beispiel zeigen diese Experimente bei Tubifiziden einen grösseren quantitativen Widerstand für Blei, Zink und Phenylsäure als ähnliche Widerstände, die bei verschiedenen Fisch-Species registriert wurden. Dieses bildet eine Basis für quantitative Abschätzung des Widerstandes dieser Organismen, die vielleicht in späteren Studien mit ihrer Verbindung mit verunreinigten Fundorten wertvoll sein kann.

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Supported by Grant WP 00937-02. National Institute of Health.     

Variation of cyanogenesis in some plant species of the midwestern United States

The frequency of cyanogenesis of 48 species of vascular plants was examined by testing 30 individuals from five populations of each species for release of cyanide. The rate at which cyanide was released and the amount of cyanide released varied widely among individuals of a population and among populations of a species. For many taxa, the frequency of cyanogenesis was highly variable among populations. Of the species examined, 20 have not been reported previously as being cyanogenic.     

Haploid plant regeneration from anther cultures of three north american cultivars of strawberry (Fragaria x ananassa Duch.)

Summary A study was conducted to maximize plant regeneration frequencies from cultured anthers of Chandler, Honeoye, and Redchief strawberries (Fragaria x ananassa Duch.). A comparison of auxins (IAA, NAA), cytokinins (BA, BPA, KIN) and carbohydrates (sucrose, glucose, maltose) in MS medium showed that the highest shoot regeneration across cultivars (8%) occurred when using a medium containing 2 mg/l IAA, 1 mg/l BA, and 0.2 M glucose. A comparison of MS, NN, and H1 inorganic medium (a new formulation based on the anther culture literature) solidified with either agar or gellan gum and containing IAA, BA, and glucose, showed the highest shoot regeneration across cultivars (19%) when using H1 and gellan gum. Lastly, media containing Fe-EDTA yielded more shoots than media containing Fe-Metalosate, and anthers cultured on Fe-EDTA media in darkness for 30d followed by 30d in white light produced more shoots (16% average regeneration) than those cultured on Fe-EDTA media under white or yellow light (16h photoperiod) for the initial 30d (0.3% and 5% respectively). Plants were acclimated ex vitro where they flowered and set fruit. Chromosome counts of root tip cells confirmed that haploid plants were obtained from all three cultivars.Abbreviations IAA indoleacetic acid - NAA naphthaleneacetic acid - BA 6-benzylaminopurine - BPA N-benzyl-9-(2-tetrahydropyranyl)-adenine - KIN 6-furfurylaminopurine - MS Murashige & Skoog (1962) - NN Nitsch & Nitsch (1969)     

Larger trees may support larger Indiana bat maternity colonies in a dynamic landscape

Indiana bats (Myotis sodalis), federally listed as endangered, are of management concern in eastern North America. While researchers quantified the habitat affinities of the species throughout the range, few studies have occurred in regions where populations are at high risk for wind energy development and changing climes. Central Illinois, USA, is a dynamic landscape where forest area has been increasing in recent decades (on public and private land) because of changing farming practices and increased habitat protections. The increasing availability of large diameter trees, increasing forest biomass, and changing forest compositions have the potential to influence Indiana bat roost habitat preferences. We assessed Indiana bat maternity roost selection at the tree and forest plot scale to characterize patterns of use in this region from 2017–2018. We predicted that large trees on the landscape would support large colonies of Indiana bats. We located bats in multiple species of trees including elm (Ulmus spp.), cottonwood (Populus deltoides), and shagbark hickory (Carya ovata). We documented larger maternity colonies sharing roosts than in previous studies from the 1980s in the same region. We suggest managers and regulatory agencies monitor Indiana bats in dynamic landscapes such as those with changing forest composition and biomass.     

An improved assay method for a pseudomurein-degrading enzyme of Methanobacterium wolfei and the Protoplast formation of Methanobacterium thermoautotrophicum by the enzyme

An improved assay method of a pseudomurein-degrading enzyme and its properties are described. The pseudomurein-degrading enzyme purified from Methanobacterium wolfei autolysate under an anoxic condition was assayed with the cell wall of Methanobacterium thermoautotrophicum as a substrate. By this improved method the enzyme activity was measured quantitatively and reproducibly. Moreover, the cell wall substrate can be stored in a freezer and used as needed, and the time required for an assay was as short as 1 h. The optimum pH and temperature of the enzyme was pH 6.8-7.4 and 75°C, respectively. Although the enzyme lost 50% of the activity upon heating at 75°C for 10 min in the absence of the cell wall substrate, it was more stable against heat inactivation in the presence of the substrate. Furthermore the inactivated enzyme recovered some of the activity by incubating with the substrate. Although the enzyme lost most of the activity under aerobic conditions, the activity was recovered under reducing conditions with Na₂S·9H₂O or DTT (dithiothreitol). The enzyme was also purified under aerobic conditions retaining the same specific activity as the anoxically purified enzyme. Using the partially purified enzyme the conditions preparing protoplasts of M. thermoautotrophicum was established.     

Reprint of “Functional overlaps between XLF and the ATM-dependent DNA double strand break response”

Developing B and T lymphocytes generate programmed DNA double strand breaks (DSBs) during the V(D)J recombination process that assembles exons that encode the antigen-binding variable regions of antibodies. In addition, mature B lymphocytes generate programmed DSBs during the immunoglobulin heavy chain (IgH) class switch recombination (CSR) process that allows expression of different antibody heavy chain constant regions that provide different effector functions. During both V(D)J recombination and CSR, DSB intermediates are sensed by the ATM-dependent DSB response (DSBR) pathway, which also contributes to their joining via classical non-homologous end-joining (C-NHEJ). The precise nature of the interplay between the DSBR and C-NHEJ pathways in the context of DSB repair via C-NHEJ remains under investigation. Recent studies have shown that the XLF C-NHEJ factor has functional redundancy with several members of the ATM-dependent DSBR pathway in C-NHEJ, highlighting unappreciated major roles for both XLF as well as the DSBR in V(D)J recombination, CSR and C-NHEJ in general. In this review, we discuss current knowledge of the mechanisms that contribute to the repair of DSBs generated during B lymphocyte development and activation with a focus on potential functionally redundant roles of XLF and ATM-dependent DSBR factors.