Heterogeneity of soil and soil solution chemistry under Norway spruce (Picea abies Karst.) and European beech (Fagus silvatica L.) as influenced by distance from the stem basis

The present study aims at characterizing plant water status under field conditions on a daily basis, in order to improve operational predictions of plant water stress. Ohm's law analog serves as a basis for establishing daily soil-plant relationships, using experimental data from a water-limited soybean crop: 227-1. The daily transpiration flux, T, is estimated from experimental evapotranspiration data and simulated soil evaporation values. The difference, 227-2, named the effective potential gradient, is derived from i) the midday leaf potential of the uppermost expanded leaves and ii) an effective soil potential accounting for soil potential profile and an effectiveness factor of roots competing for water uptake. This factor is experimentally estimated from field observation of roots. G is an apparent hydraulic conductance of water flow from the soil to the leaves. The value of the lower potential limit for water extraction, required to assess the effective soil potential, is calculated with respect to the plant using the predawn leaf potential. It is found to be equal to –1.2 MPa. It appears that over the range of soil and climatic conditions experienced, the daily effective potential gradient remains constant (1.2 MPa), implying that, on a daily basis, transpiration only depends on the hydraulic conductance. The authors explain this behaviour by diurnal variation of osmotic potential, relying on Morgan's theory (1984). Possible generalization of the results to other crop species is suggested, providing a framework for reasoning plant water behaviour at a daily time step.     

Gas exchange characteristics and nitrogen relations of two Mediterranean root hemiparasites:Bartsia trixago andParentucellia viscosa

Plant height, light-saturated rates of photosynthesis (A _max) and foliar nitrogen concentration (N ₁) were measured forBartsia trixago under field conditions in Mallorca. All three variables were postively correlated, and were also positively related to the abundance of nitrogen-fixing legumes in the associated vegetation (putative host species).A _max forB. trixago ranged from 7.7 to 18.8 mol m^-2 s^-1; similar rates were measured for a second hemiparasiteParentucellia viscosa, and both species were within the range of rates measured for six putative hosts (10.6–19.2 mol m^-2 s^-1). Fertilization of unattachedB. trixago plants with inorganic nitrogen (ammonium nitrate) elicited neither the growth nor the photosynthetic responses observed in plants considered to be parasitic on legumes and in receipt of an enriched organic nitrogen supply. Both hemiparasites had high diurnal leaf conductances (g _s) (469–2291 mmol m^-2 s^-1) and were at the upper end of the range of those measured in putative hosts (409–879 mmol m^-2 s^-1). In contrast with the latter, high nocturnal rates ofg _s were also recorded for the two hemiparasites (517–1862 mmol m^-2 s^-1). There was no clear relationship between eitherA _max orN ₁ and eitherg _s, transpiration (E) or water use efficiency (A _max/E) inB. trixago plants. The economics of water loss appear to be independent of both the supply of nitrogen from the host and autotrophic carbon fixation.     

The Pro-inflammatory Role of TGFβ1: A Paradox?

TGFβ1 was initially identified as a potent chemotactic cytokine to initiate inflammation, but the autoimmune phenotype seen in TGFβ1 knockout mice reversed the dogma of TGFβ1 being a pro-inflammatory cytokine to predominantly an immune suppressor. The discovery of the role of TGFβ1 in Th17 cell activation once again revealed the pro-inflammatory effect of TGFβ1. We developed K5.TGFβ1 mice with latent human TGFβ1 overexpression targeted to epidermal keratinocytes by keratin 5. These transgenic mice developed significant skin inflammation. Further studies revealed that inflammation severity correlated with switching TGFβ1 transgene expression on and off, and genome wide expression profiling revealed striking similarities between K5.TGFβ1 skin and human psoriasis, a Th1/Th17-associated inflammatory skin disease. Our recent study reveals that treatments alleviating inflammatory skin phenotypes in this mouse model reduced Th17 cells, and antibodies against IL-17 also lessen the inflammatory phenotype. Examination of inflammatory cytokines/chemokines affected by TGFβ1 revealed predominantly Th1-, Th17-related cytokines in K5.TGFβ1 skin. However, the finding that K5.TGFβ1 mice also express Th2-associated inflammatory cytokines under certain pathological conditions raises the possibility that deregulated TGFβ signaling is involved in more than one inflammatory disease. Furthermore, activation of both Th1/Th17 cells and regulatory T cells (Tregs) by TGFβ1 reversely regulated by IL-6 highlights the dual role of TGFβ1 in regulating inflammation, a dynamic, context and organ specific process. This review focuses on the role of TGFβ1 in inflammatory skin diseases.     

Mechanobiological dysregulation of the epidermis and dermis in skin disorders and in degeneration

During growth and development, the skin expands to cover the growing skeleton and soft tissues by constantly responding to the intrinsic forces of underlying skeletal growth as well as to the extrinsic mechanical forces from body movements and external supports. Mechanical forces can be perceived by two types of skin receptors: (1) cellular mechanoreceptors/mechanosensors, such as the cytoskeleton, cell adhesion molecules and mechanosensitive (MS) ion channels, and (2) sensory nerve fibres that produce the somatic sensation of mechanical force. Skin disorders in which there is an abnormality of collagen [e.g. Ehlers–Danlos syndrome (EDS)] or elastic (e.g. cutis laxa) fibres or a malfunction of cutaneous nerve fibres (e.g. neurofibroma, leprosy and diabetes mellitus) are also characterized to some extent by deficiencies in mechanobiological processes. Recent studies have shown that mechanotransduction is crucial for skin development, especially hemidesmosome maturation, which implies that the pathogenesis of skin disorders such as bullous pemphigoid is related to skin mechanobiology. Similarly, autoimmune diseases, including scleroderma and mixed connective tissue disease, and pathological scarring in the form of keloids and hypertrophic scars would seem to be clearly associated with the mechanobiological dysfunction of the skin. Finally, skin ageing can also be considered as a degenerative process associated with mechanobiological dysfunction. Clinically, a therapeutic strategy involving mechanoreceptors or MS nociceptor inhibition or acceleration together with a reduction or augmentation in the relevant mechanical forces is likely to be successful. The development of novel approaches such as these will allow the treatment of a broad range of cutaneous diseases.     

Atmospheric CO2 enrichment increases growth and photosynthesis of Pinus taeda: a 4 year experiment in the field

Forest trees are major components of the terrestrial biome and their response to rising atmospheric CO₂ plays a prominent role in the global carbon cycle. In this study, loblolly pine seedlings were planted in the field in recently disturbed soil of high fertility, and CO₂ partial pressures were maintained at ambient CO₂ (Amb) and elevated CO₂ (Amb + 30 Pa) for 4 years. The objective of the study was to measure seasonal and long-term responses in growth and photosynthesis of loblolly pine exposed to elevated CO₂ under ambient field conditions of precipitation, light, temperature and nutrient availability. Loblolly pine trees grown in elevated CO₂ produced 90% more biomass after four growing seasons than did trees grown in ambient CO₂. This large increase in final biomass was primarily due to a 217% increase in leaf area in the first growing season which resulted in much higher relative growth rates for trees grown in elevated CO₂. Although there was not a sustained effect of elevated CO₂ on relative growth rate after the first growing season, absolute production of biomass continued to increase each year in trees grown in elevated CO₂ as a consequence of the compound interest effect of increased leaf area on the production of more new leaf area and more biomass. Allometric analyses of biomass allocation patterns demonstrated size-dependent shifts in allocation, but no direct effects of elevated CO₂ on partitioning of biomass. Leaf photosynthetic rates were always higher in trees grown in elevated CO₂, but these differences were greater in the summer (60–130% increase) than in the winter (14–44% increase), reflecting strong seasonal effects of temperature on photosynthesis. Our results suggest that seasonal variation in the relative photosynthetic response to elevated CO₂ will occur in natural ecosystems, but total non-structural carbohydrate (TNC) levels in leaves indicate that this variation may not always be related to sink activity. Despite indications of canopy-level adjustments in carbon assimilation, enhanced levels of leaf photosynthesis coupled with increased total leaf area indicate that net carbon assimilation for the whole tree was greater for trees grown under elevated CO₂ compared with ambient CO₂. If the large growth enhancement observed in loblolly pine were maintained after canopy closure, then these trees could be a large sink for fossil carbon emitted to the atmosphere and produce a negative feedback on atmospheric CO₂.     

Ecophysiological responses to simulated canopy gaps of two tree species of contrasting shade tolerance in elevated CO2

1. One-year-old seedlings of shade tolerant Acer rubrum and intolerant Betula papyrifera were grown in ambient and twice ambient (elevated) CO₂, and in full sun and 80% shade for 90 days. The shaded seedlings received 30-min sun patches twice during the course of the day. Gas exchange and tissue–water relations were measured at midday in the sun plants and following 20 min of exposure to full sun in the shade plants to determine the effect of elevated CO₂ on constraints to sun-patch utilization in these species.
2. Elevated CO₂ had the largest stimulation of photosynthesis in B. papyrifera sun plants and A. rubrum shade plants.
3. Higher photosynthesis per unit leaf area in sun plants than in shade plants of B. papyrifera was largely owing to differences in leaf morphology. Acer rubrum exhibited sun/shade differences in photosynthesis per unit leaf mass consistent with biochemical acclimation to shade.
4. Betula papyrifera exhibited CO₂ responses that would facilitate tolerance to leaf water deficits in large sun patches, including osmotic adjustment and higher transpiration and stomatal conductance at a given leaf-water potential, whereas A. rubrum exhibited large increases in photosynthetic nitrogen-use efficiency.
5. Results suggest that species of contrasting successional ranks respond differently to elevated CO₂, in ways that are consistent with the habitats in which they typically occur.     

Effects of boundary layer conductance on substomatal pressures of carbon dioxide

Abstract. Gas exchange measurements were made on single leaves of three C₃ and one C₄ species at air speeds of 0.4 and 4.0 m s⁻¹ to determine if boundary layer conductance substantially affected the substomatal pressure of carbon dioxide. Boundary layer conductances to water vapour were 0.4 to 0.5 mol m⁻² s⁻¹ at the lower air speed, and 1.2 to 1.5 mol m⁻² s⁻¹ at the higher air speed. Substomatal carbon dioxide pressures were about 5 Pa lower at low boundary layer conductance in the C₃ species, and about 3 Pa lower in the C₄ species when measurements were made at high and moderate photosynthetic photon flux densities. No evidence of stomatal adjustment to altered boundary layer conductance was found. Photosynthetic rates at high photon flux densities were reduced by about 20% at the low air speed in the C₃ species. The commonly reported values of substomatal carbon dioxide pressure for C₃ and C₄ species were found to occur only when measurements were made at the higher air speed.     

miRNA expression profiling uncovers a role of miR-302b-3p in regulating skin fibroblasts senescence

Numbers of emerging evidence suggest that variable microRNA (miRNA) expression facilitates the aging process. In this study, we distinguished aberrant miRNA expression in aged skin and explored the biological functions and potential mechanism of upregulated miR-302b-3p. At first, miRNA microarray analysis was examined to explore miRNA expression profiling in the skin of aging mice model by D -galactose (d -gal) injection. We identified 29 aberrant miRNAs in aged mice skin. Next, KEGG enrichment analysis was conducted with DIANA-miPath v3.0, which was revealed that enrichment pathways involved in such processes as extracellular matrix-receptor interaction, MAPK signaling pathway, and mammalian target of rapamycin (mTOR) signaling pathway. The target genes of deregulated miRNAs were predicted from four bioinformatic algorithms (miRDB, Targetscan, miRwalk, and Tarbase). The interaction network of miRNAs and their targets were visualized using Cytoscape software. As a result, we found that some hub genes (including JNK2, AKT1/2/3, PAK7, TRPS1, BCL2L11, and IKZF2) were targeted by 12 potential miRNAs (including miR-302b-3p, miR-291a-5p, miR-139-3p, miR-467c-3p, miR-186-3p, etc.). Subsequently, we identified five upregulated miRNA via quantitative polymerase chain reaction and all of them were confirmed increased significantly in aged skin tissues compared with young control tissues. Among them, high expression of miR-302b-3p was verified in both aged skin tissues and senescence fibroblasts. Furthermore, miR-302b-3p mimic accelerated skin fibroblast senescence and suppressed the longevity-associated gene Sirtuin 1(Sirt1) expression, whereas miR-302b-3p inhibitor could delay skin fibroblast senescence and contribute Sirt1 expression. In addition, we demonstrated that c-Jun N-terminal kinase 2(JNK2) is a direct target of miR-302b-3p by a luciferase reporter assay. An inverse correlation was verified in fibroblasts between miR-302b-3p and JNK2. Most importantly, siRNA JNK2 confirmed that low expression of JNK2 could accelerate fibroblasts senescence. In conclusion, our results indicated that overexpressed miR-302b-3p plays an important biological role in accelerating skin aging process via directly targeting JNK2 gene.     

基于Gabor滤波器的皮肤纹理图像增强

在疗效化妆品中,常常需要对护肤品的性能和效果进行分析。皮肤纹理的检测是客观衡量疗效化妆品的有效手段。基于计算机视觉技术的皮肤纹理分析,对拍摄的皮肤图像要进行图像预处理,增强图像,为后续的分析提供有效的数据。采用经过微调的定向的Gabor滤波器进行增强图像,通过实验得出Gabor滤波器不仅抑制噪声的效果好,还保留了皮肤图像的整体和局部特征。     

Differential leaf expansion can enable hydraulic acclimation to sun and shade

Although leaf size is one of the most responsive plant traits to environmental change, the functional benefits of large versus small leaves remain unclear. We hypothesized that modification of leaf size within species resulting from differences in irradiance can allow leaves to acclimate to different photosynthetic or evaporative conditions while maintaining an efficient balance between hydraulic supply (vein density) and evaporative demand. To test this, we compared the function and anatomy of leaf hydraulic systems in the leaves of a woody angiosperm (Toona ciliata M. Roem.) grown under high and low irradiance in controlled conditions. Our results confirm that in this species, differential leaf expansion regulates the density of veins and stomata such that leaf hydraulic conductance and stomatal conductance remain proportional. A broader sample of field-grown tree species suggested that differences in leaf venation and stomatal traits induced by sun and shade were not regulated by leaf size in all cases. Our results, however, suggest that leaf size plasticity can provide an efficient way for plants to acclimate hydraulic and stomatal conductances to the contrasting evaporative conditions of sun and shade.