The flora of California, a global biodiversity hotspot, includes 2387 endemic plant taxa. With anticipated climate change, we project that up to 66% will experience >80% reductions in range size ...within a century. These results are comparable with other studies of fewer species or just samples of a region's endemics. Projected reductions depend on the magnitude of future emissions and on the ability of species to disperse from their current locations. California's varied terrain could cause species to move in very different directions, breaking up present-day floras. However, our projections also identify regions where species undergoing severe range reductions may persist. Protecting these potential future refugia and facilitating species dispersal will be essential to maintain biodiversity in the face of climate change.
The Literature of Satire is an accessible but sophisticated and wide-ranging study of satire from the classics to the present in plays, novels and the press as well as in verse. In it Charles Knight ...analyses the rhetorical problems created by satire's complex relations to its community, and examines how it exploits the genres it borrows. He argues that satire derives from an awareness of the differences between appearance, ideas and discourse. Knight provides illuminating readings of such satirists familiar and unfamiliar as Horace, Lucian, Jonson, Molière, Swift, Pope, Byron, Flaubert, Ostrovsky, Kundera, and Rushdie. This broad-ranging examination sheds light on the nature and functions of satire as a mode of writing, as well as on theoretical approaches to it. It will be of interest to scholars interested in literary theory as well as those specifically interested in satire.
Across eukaryotes phenotypic correlations with genome size are thought to scale from genome size effects on cell size. However, for plants the genome/cell size link has only been thoroughly ...documented within ploidy series and small subsets of herbaceous species. Here, the first large-scale comparative analysis is made of the relationship between genome size and cell size across 101 species of angiosperms of varying growth forms. Guard cell length and epidermal cell area were used as two metrics of cell size and, in addition, stomatal density was measured. There was a significant positive relationship between genome size and both guard cell length and epidermal cell area and a negative relationship with stomatal density. Independent contrast analyses revealed that these traits are undergoing correlated evolution with genome size. However, the relationship was growth form dependent (nonsignificant results within trees/shrubs), although trees had the smallest genome/cell sizes and the highest stomatal density. These results confirm the generality of the genome size/cell size relationship. The results also suggest that changes in genome size, with concomitant influences on stomatal size and density, may influence physiology, and perhaps play an important genetic role in determining the ecological and life-history strategy of a species.
Ice Growth from the Vapor at -5°C KNIGHT, Charles A
Journal of the atmospheric sciences,
06/2012, Volume:
69, Issue:
6
Journal Article
Peer reviewed
Open access
Abstract
Results are summarized and illustrated from a long series of experiments on ice growth from the vapor, nearly all in a very small range of conditions: −5°C, slightly below liquid water ...saturation, with minimal environmental gradients and no imposed ventilation. The temperature was chosen because c-axis ice needles grow in a narrow temperature interval there, which coincides with the temperature at which the Hallett–Mossop ice multiplication process operates most effectively, and one may suspect that this coincidence is likely to be meaningful. The ice growth habit is poorly reproducible in these conditions, dictating many runs with little change. Growth as plates can persist for hours, and two distinct types of needle growth occur, called sheath needles and sharp needles. Both are distinct from thin columns in that they taper to a point, with no discernible basal face. Both deviate slightly from parallel to the c axis. Sharp needles have been reported before, but only as occurring with an applied high DC voltage. New crystal orientations nucleate occasionally at the tips of the sharp needles; this also has been seen before in the presence of strong electric fields. There appears to be an ice multiplication mechanism in these conditions that does not involve riming.
Tree crowns are spatially heterogeneous, sometimes resulting in significant variation in microclimate across the canopy, particularly with respect to temperature. Yet it is not known whether such ...localised temperature variation equates to intracanopy variation in leaf-level physiological thermal tolerance. Here, we studied whether microclimate variation across the canopy of a dominant desert tree equated to localised variation in leaf thermal thresholds (T₅₀) among four canopy positions: upper south, upper north, lower south, lower north. Principal component analysis was used to generate a composite climatic stress variable (CSTRESS) from canopy temperature, vapour pressure deficit, and relative humidity. We also determined the average number of days that maximum temperatures exceeded the air temperature equating to this species’ critical threshold of 49 °C (AT₄₉). To estimate how closely leaf temperatures track ambient temperature, we predicted the thermal time constant (τ) for leaves at each canopy position. We found that CSTRESS and AT₄₉ were significantly greater in lower and north-facing positions in the canopy. Differences in wind speed with height resulted in significantly longer predicted τ for leaves positioned at lower, north-facing positions. Variation in these drivers was correlated with significantly higher T₅₀ for leaves in these more environmentally stressful canopy positions. Our findings suggest that this species may optimise resources to protect against thermal damage at a whole-plant level. They also indicate that, particularly in desert environments with steep intracanopy microclimatic gradients, whole-plant carbon models could substantially under- or overestimate productivity under heat stress, depending on where in the canopy T₅₀ is measured.
Our understanding of the effects of heat stress on plant photosynthesis has progressed rapidly in recent years through the use of chlorophyll a fluorescence techniques. These methods frequently ...involve the treatment of leaves for several hours in dark conditions to estimate declines in maximum quantum yield of photsystem II (F V/F M), rarely accounting for the recovery of effective quantum yield (ΔF/F M′) after thermally induced damage occurs. Exposure to high temperature extremes, however, can occur over minutes, rather than hours, and recent studies suggest that light influences damage recovery. Also, the current focus on agriculturally important crops may lead to assumptions about average stress responses and a poor understanding about the variation among species’ thermal tolerance. We present a chlorophyll a fluorescence protocol incorporating subsaturating light to address whether species’ thermal tolerance thresholds (T ₅₀) are related to the ability to recover from short-term heat stress in 41 Australian desert species. We found that damage incurred by 15-min thermal stress events was most strongly negatively correlated with the capacity of species to recover after a stress event of 50 °C in summer. Phylogenetically independent contrast analyses revealed that basal divergences partially explain this relationship. Although T ₅₀ and recovery capacity were positively correlated, the relationship was weaker for species with high T ₅₀ values (>51 °C). Results highlight that, even within a single desert biome, species vary widely in their physiological response to high temperature stress and recovery metrics provide more comprehensive information than damage metrics alone.
BACKGROUND AND AIMS: Early observations that genome size was positively correlated with cell size formed the basis of hypothesized consequences of genome size variation at higher phenotypic scales. ...This scaling was supported by several studies showing a positive relationship between genome size and seed mass, and various metrics of growth and leaf morphology. However, many of these studies were undertaken with limited species sets, and often performed within a single genus. Here we seek to generalize the relationship between genome size and the phenotype by examining eight phenotypic traits using large cross-species comparisons involving diverse assemblages of angiosperm and gymnosperm species. These analyses are presented in order of increasing scale (roughly equating to the number of cells required to produce a particular phenotypic trait), following the order of: cell size (guard cell and epidermal), stomatal density, seed mass, leaf mass per unit area (LMA), wood density, photosynthetic rate and finally maximum plant height. SCOPE: The results show that genome size is a strong predictor of phenotypic traits at the cellular level (guard cell length and epidermal cell area had significant positive relationships with genome size). Stomatal density decreased with increasing genome size, but this did not lead to decreased photosynthetic rate. At higher phenotypic scales, the predictive power of genome size generally diminishes (genome size had weak predictive power for both LMA and seed mass), except in the interesting case of maximum plant height (tree species tend to have small genomes). There was no relationship with wood density. The general observation that species with larger genome size have larger seed mass was supported; however, species with small genome size can also have large seed masses. All of these analyses involved robust comparative methods that incorporate the phylogenetic relationships of species. CONCLUSIONS: Genome size correlations are quite strong at the cellular level but decrease in predictive power with increasing phenotypic scale. Our hope is that these results may lead to new mechanistic hypotheses about why genome size scaling exists at the cellular level, and why nucleotypic consequences diminish at higher phenotypic scales.
To prospectively evaluate percutaneous image-guided nerve cryoablation for treatment of refractory phantom limb pain (PLP) in a pilot cohort for purposes of deriving parameters to design a larger, ...randomized, parallel-armed, controlled trial.
From January 2015 to January 2016, 21 patients with refractory PLP underwent image-guided percutaneous cryoneurolysis procedures. Visual analog scale scores were documented at baseline and 7, 45, and 180 days after the procedure. Responses to a modified Roland Morris Disability Questionnaire were documented at baseline and 7 and 45 days after the procedure.
Technical success rate of the procedures was 100%. There were 6 (29%) minor procedure-related complications. Disability scores decreased from a baseline mean of 11.3 to 3.3 at 45-day follow-up (95% confidence interval 5.8, 10.3; P < .0001). Pain intensity scores decreased from a baseline mean of 6.2 to 2.0 at long-term follow-up (95% confidence interval 2.8, 5.6; P < .0001).
Image-guided percutaneous nerve cryoablation is feasible and safe and may represent a new efficacious therapeutic option for patients with phantom pains related to limb loss.
The strong positive relationship evident between cell and genome size in both animals and plants forms the basis of using the size of stomatal guard cells as a proxy to track changes in plant genome ...size through geological time.
We report for the first time a taxonomic fine-scale investigation into changes in stomatal guard-cell length and use these data to infer changes in genome size through the evolutionary history of land plants.
Our data suggest that many of the earliest land plants had exceptionally large genome sizes and that a predicted overall trend of increasing genome size within individual lineages through geological time is not supported. However, maximum genome size steadily increases from the Mississippian (c. 360 million yr ago (Ma)) to the present.
We hypothesise that the functional relationship between stomatal size, genome size and atmospheric CO2 may contribute to the dichotomy reported between preferential extinction of neopolyploids and the prevalence of palaeopolyploidy observed in DNA sequence data of extant vascular plants.
In eukaryotes, ribosome biosynthesis involves the coordination of ribosomal RNA and ribosomal protein (RP) production. In S. cerevisiae, the regulation of ribosome biosynthesis occurs largely at the ...level of transcription. The transcription factor Ifh1 binds at RP genes and promotes their transcription when growth conditions are favorable. Although Ifh1 recruitment to RP genes has been characterized, little is known about the regulation of promoter-bound Ifh1.
We used a novel whole-cell-extract screening approach to identify Spt7, a member of the SAGA transcription complex, and the RP transactivator Ifh1 as highly acetylated nonhistone species. We report that Ifh1 is modified by acetylation specifically in an N-terminal domain. These acetylations require the Gcn5 histone acetyltransferase and are reversed by the sirtuin deacetylases Hst1 and Sir2. Ifh1 acetylation is regulated by rapamycin treatment and stress and limits the ability of Ifh1 to act as a transactivator at RP genes.
Our data suggest a novel mechanism of regulation whereby Gcn5 functions to titrate the activity of Ifh1 following its recruitment to RP promoters to provide more than an all-or-nothing mode of transcriptional regulation. We provide insights into how the action of histone acetylation machineries converges with nutrient-sensing pathways to regulate important aspects of cell growth.
•Ifh1 and Spt7 are highly acetylated proteins in yeast•Ifh1 is acetylated by Gcn5 and deacetylated by sirtuins•Acetylation of Ifh1 is inhibited by cell stress•Acetylation in an N-terminal domain inhibits Ifh1’s function as a transactivator
PDF
