Quantifying the impact of current and future tropospheric ozone on tree biomass, growth, physiology and biochemistry: a quantitative meta-analysis

The northern hemisphere temperate and boreal forests currently provide an important carbon sink; however, current tropospheric ozone concentrations ([O₃]) and [O₃] projected for later this century are damaging to trees and have the potential to reduce the carbon sink strength of these forests. This meta‐analysis estimated the magnitude of the impacts of current [O₃] and future [O₃] on the biomass, growth, physiology and biochemistry of trees representative of northern hemisphere forests. Current ambient [O₃] (40 ppb on average) significantly reduced the total biomass of trees by 7% compared with trees grown in charcoal‐filtered (CF) controls, which approximate preindustrial [O₃]. Above‐ and belowground productivity were equally affected by ambient [O₃] in these studies. Elevated [O₃] of 64 ppb reduced total biomass by 11% compared with trees grown at ambient [O₃] while elevated [O₃] of 97 ppb reduced total biomass of trees by 17% compared with CF controls. The root‐to‐shoot ratio was significantly reduced by elevated [O₃] indicating greater sensitivity of root biomass to [O₃]. At elevated [O₃], trees had significant reductions in leaf area, Rubisco content and chlorophyll content which may underlie significant reductions in photosynthetic capacity. Trees also had lower transpiration rates, and were shorter in height and had reduced diameter when grown at elevated [O₃]. Further, at elevated [O₃], gymnosperms were significantly less sensitive than angiosperms. There were too few observations of the interaction of [O₃] with elevated [CO₂] and drought to conclusively project how these climate change factors will alter tree responses to [O₃]. Taken together, these results demonstrate that the carbon‐sink strength of northern hemisphere forests is likely reduced by current [O₃] and will be further reduced in future if [O₃] rises. This implies that a key carbon sink currently offsetting a significant portion of global fossil fuel CO₂ emissions could be diminished or lost in the future.     

Ozone-induced ultrastructural changes in the plasma membrane of Chlorella sorokiniana

Abstract. Modifications in plasma membrane structure and permeability were observed in Chlorella sorokiniana following exposure to 0.2 gm⁻³(140 p.p.m.) O₃ for 30 min. Sixty-eight per cent of the cells were plasmolysed after 15 min O₃ exposure with disruption of organelles similar to that previously described in higher plants. Freeze-fracture exposed large areas of plasma membrane in 90% of the control cells and those exposed to O₃for short periods. After 20 min O₃ 90% of the cells cross-fracture, which indicates a change in molecular interactions in the membrane exposed to O₃ The earliest observed ultraslructural alteration is an aggregation of particles on the plasma membrane P face, statistically significant after 10 min O₃ Changes in ⁸⁶Rb influx occur during a similar time. After more extended exposure to O³ the plasma membrane P face shows regions of lipid phase transition to the crystalline state.     

Predicting small‐mammal responses to climatic warming: autecology,geographic range,and the Holocene fossil record

Forecasting how species will respond to climatic change requires knowledge of past community dynamics. Here we use time‐series data from the small‐mammal fossil records of two caves in the Great Basin of the American West to evaluate how contrasting and variable local paleoclimates have shaped small‐mammal abundance dynamics over the last ～7500 years of climatic change. We then predict how species and communities will respond to future scenarios of increased warming and aridity coupled with continued spread of an invasive annual grass (Bromus tectorum). We find that most community‐level responses to climatic change occur in the mammalian abundance structure at both sites; the dominance of the community by individuals from species with a southern geographic affinity increases with climatic warming. This suggests that responses occurred in situ rather than by the immigration of new taxa over this time interval. Despite predictability at the community‐scale, species‐level relationships between abundance and climate are variable and are not necessarily explained by a species' geographic affinity. Species present at both sites, however, exhibit remarkably similar responses to climate at each site, indicating that species autecology (specifically dietary functional group) is important in determining response to climatic warming. Regression‐tree analyses show remarkable concordance between the two cave faunas and highlight the importance of a granivorous dietary strategy in this desert ecosystem. Under projections of increased temperature and decreased precipitation over the next 50 years, our results indicate that granivores should thrive as communities become more dominated by individuals with a southern geographic affinity. Granivores, however, are negatively impacted by the invasion of cheatgrass. The last century of anthropogenic impacts has thus placed granivores at a greater risk of extinction than predicted under climate‐only scenarios.     

Validation of a Field Technique and Characterization of Fecal Glucocorticoid Metabolite Analysis in Wild Chimpanzees (Pan troglodytes)

Monitoring adrenocortical activity in wild primate populations is critical, given the well‐documented relationship between stress, health, and reproduction. Although many primate studies have quantified fecal glucocorticoid metabolite (FGM) concentrations, it is imperative that researchers validate their method for each species. Here, we describe and validate a technique for field extraction and storage of FGMs in wild chimpanzees (Pan troglodytes). Our method circumvents many of the logistical challenges associated with field studies while yielding similar results to a commonly used laboratory method. We further validate that our method accurately reflects stress physiology using an adrenocorticotropic hormone challenge in a captive chimpanzee and an FGM peak at parturition in a wild subject. Finally, we quantify circadian patterns for FGMs for the first time in this species. Understanding these patterns may allow researchers to directly link specific events with the stress response. Am. J. Primatol. 75:57‐64, 2013. © 2012 Wiley Periodicals, Inc.     

Comparative labellum micromorphology of the sexually deceptive temperate orchid genus Ophrys: diverse epidermal cell types and multiple origins of structural colour

Labellum micromorphology was imaged via scanning electron and light microscopy in 32 microspecies and one artificial hybrid of the European terrestrial orchid genus Ophrys, together representing all ten macrospecies circumscribed in the genus via molecular phylogenetics. Imaging of homologous regions of the adaxial surface, paying particular attention to the diagnostic feature of the comparatively reflective speculum, revealed the presence of between three and seven epidermal cell types on each labellum, the less complex labella being plesiomorphic. Epidermal protuberances range from short, domed papillae to long, twisted unicellular filaments. Multiple origins are inferred for pale labellar margins, large yellow appendices (both putative osmophores exuding pseudopheromones), broad flat labella and long lateral horns. Homoplasy in the speculum is manifested in unusually complex or simple outlines and the presence or absence of a pale margin or iridescence. The reflectivity of the speculum is caused by a combination of chemical and physical colour, whereas iridescence can be caused only by physical properties. The specula of most microspecies studied bear striated trichomes, albeit maturing comparatively late in ontogeny and being sufficiently narrow to allow light to reach the flat polygonal trichome bases. Reflectivity appears to be negatively correlated with the convexity and degree of cuticular corrugation shown by these epidermal cells. Two clades (the Speculum + Tenthredinifera + Bombyliflora group and Bertolonii subgroup of the Sphegodes group) have lost specular trichomes and include the most iridescent species; their flat, polygonal, nonstriated cells resemble those observed on the paired pseudoeyes that bracket the stigmas of all Ophrys except the Fusca group. The smooth thick‐layered cuticle and dense layers of organelles and starch bodies revealed by preliminary transmission electron microscopy study provide alternative candidates for the primary reflective surface of the speculum; in contrast, the trichomes and conical cells that dominate Ophrys labella, and occur on the specula of all but the most reflective species, absorb and/or diffuse light. Multiple MYB family genes are hypothesized to control epidermal micromorphology. The relative contributions of olfactory, visual and tactile cues to the sophisticated pseudocopulatory pollination mechanism that characterizes Ophrys remain unclear, but the degree of reproductive isolation achieved, and thus the speciation rate, have certainly been greatly exaggerated by most observers. © 2010 The Linnean Society of London, Botanical Journal of the Linnean Society, 2010, 162 , 504–540.     

Effects of fishing and acidification‐related benthic mortality on the southeast Australian marine ecosystem

Oceanic uptake of anthropogenic carbon dioxide (CO₂) is altering the carbonate chemistry of seawater, with potentially negative consequences for many calcifying marine organisms. At the same time, increasing fisheries exploitation is impacting on marine ecosystems. Here, using increased benthic‐invertebrate mortality as a proxy for effects of ocean acidification, the potential impact of the two stressors of fishing and acidification on the southeast Australian marine ecosystem to year 2050 was explored. The individual and interaction effects of the two stressors on biomass and diversity were examined for the entire ecosystem and for regional assemblages. For 61 functional groups or species, the cumulative effects of moderate ocean acidification and fishing were additive (30%), synergistic (33%), and antagonistic (37%). Strong ocean acidification resulted in additive (22%), synergistic (40%), and antagonistic (38%) effects. The greatest impact was on the demersal food web, with fishing impacting predation and acidification affecting benthic production. Areas that have been subject to intensive fishing were the most susceptible to acidification effect, although fishing also mitigated some of the decline in biodiversity observed with moderate acidification. The model suggested that ocean acidification and long‐term fisheries exploitation could act synergistically with the increasing sensitivity to change from long‐term (decades) fisheries exploitation potentially causing unexpected restructuring of the pelagic and demersal food webs. Major regime shifts occur around year 2040. Greater focus is needed on how differential fisheries exploitation of marine resources may exacerbate or accelerate effects of environmental changes such as ocean acidification.     

Circular rDNA Replicons Persist in Tetrahymena thermophila Transformants Synthesizing GGGGTC Telomeric Repeats

Site-directed mutagenesis of the telomerase RNA from Tetrahymena thermophila was used previously to demonstrate the templating function of a sequence within this RNA; this sequence specifies the sequence of telomeric DNA in vivo. The possible functional importance of a phylogenetically conserved nucleotide outside the telomerase RNA template region was investigated by a similar experimental approach. The telomerase RNA gene was altered by site-directed mutagenesis, cloned in a circular selectable transformation vector consisting of an rRNA gene carrying a selectable drug resistance marker, and introduced into macronuclei of vegetatively dividing Tetrahymena thermophila by microinjection. Changing an invariant A to U at position 16 of the telomerase RNA (A16U) had no effect detectable by phenotype on telomerase function in vivo. However these experiments showed that a telomerase template alteration that dictates the synthesis of the mutant telomeric DNA sequence GGGGTC leads to a profound change in the population of rDNA replicons. The addition of GGGGTC mutant repeats leads to selective pressure for the loss of high copy linear rDNA, and the rRNA genes are maintained in the form of the circular rDNA replicons introduced during transformation.     

Intraspecies Variability in the Esterases and Acid Phosphatases of Paramecium jenningsi and Paramecium multimicronucleatum: Assignment of Unidentified Paramecia; Comparison with the P. aurelia Complex1

ABSTRACT. Enzyme electrophoresis was exploited to identify stocks of paramecia previously not identified to particular species. Stocks collected in India and one from Panama belong to Paramecium jenningsi, while others collected in Panama or in Brazil are assignable to syngen 2 of P. multimicronucleatum on the basis of similarity of their esterase and acid phosphatase phenotypes. Inclusion of these doubled the numbers of stocks available in the two species, thereby facilitating examination of intraspecies variation and comparison of particular features of intraspecies variation found for the P. aurelia complex. Variant stocks were observed in P. jenningsi and in syngens 2, 3, and 4 of P. multimicronucleatum. In some cases the variant lacked the enzyme; in others, a change in mobility of the enzyme occurred that resulted in an electrophoretic form similar to one common in another species. Unique phenotypes were displayed by the variants of syngen 2 in P. multimicronucleatum. Hypervariability for Esterase B was observed in this syngen, where, in addition, several subtypes were seen for three other esterases. Unique phenotypes and hypervariability were also noted in P. biaurelia. Clustered variations were observed in these species and in the P. aurelia species. Unlike the situation for members of the aurelia complex, where lack of geographical differentiation between stocks in the same species is a unique feature, some such differentiation does occur in P. multimicronucleatum-2. The frequency of variant stocks in P. jenningsi was similar to that observed in the aurelia sibling species. In contrast, a significantly higher frequency of variant stocks was found in syngens 2, 3, and 4 of P. multimicronucleatum.     

Origin and Role of Collagen in the Embryo

The first collagen recognizable in the embryo is in the formof an incomplete basal lamina under the epiblast and hypoblast.We suggest that this collagen acts as a railroad track to guidethe migration of the primitive streak mesenchyme. The mesenchymeaggregates into chordamesoderm, a layer which is said to "induce"the overlying epiblast (now ectoderm) to develop into neuralfolds. This tissue interaction may be mediated by the formationof complete basal laminas separating the two tissues and bydeposition of sulfated mucopolysaccharides in the interveningextracellular space. At the very least, the collagenous basallamina serves to give the elongating cells of the developingneural tube a firm foothold. The fully formed neural tube andadjacent notochord are said to induce the sclerotome of thesomite to migrate medially and differentiate into cartilage.Notochord and neural tube basal lamina and collagen fibrilsmay play a role by guiding the migrating cells and stabilizingthe already existing chondrogenic bias of the cells. We wereunable to prove this hypothesis directly (by adding collagento somite cultures), because in our hands the somites died invitro even in the presence of neural tube and notochord. Wedid obtain direct evidence, however, that the basal lamina ofthe lens can promote the differentiation of the cornea in vitro.     

Decay Rates of Different mRNA in <Emphasis Type="Italic">E. coli</Emphasis> and Models of Decay

THE basis for messenger RNA instability in bacteria is not understood. Both functional capacity^1,2 and mass of messages for a given protein are lost at constant exponential rates which can differ, indicating independent processes³.