pN Sensitivity Research Articles

Elevated [CO2] raises the temperature optimum of photosynthesis and thus promotes net photosynthesis of winter wheat and rice

AbstractAtmospheric CO2 concentration ([CO2]) has increased by 49% since the pre‐industrial era, and this increase will continue. Photosynthesis has long been recognized as one of the most temperature‐sensitive processes, while far less is known about how elevated [CO2] (e[CO2]) affect crop photosynthesis response to short‐term temperature increase. To reveal the effect, we measured gas exchange of winter wheat and rice with various leaf temperatures (TL) under different [CO2] conditions (ambient, +120 μmol mol−1 in wheat, +160 μmol mol−1 in rice, and +200 μmol mol−1 in both) using open‐top chamber facility. Analysis of the measurements showed that e[CO2] generally increased net photosynthesis (Pn) by 10–40% across various TL at different developmental stages. The temperature sensitivity of Pn was negatively correlated with TL. Elevated [CO2] raised the temperature optimum (Topt) of Pn by 1.8–5.6°C for wheat and 2.2–4.8°C for rice, resulting in a wider range of TL that can promote Pn. The responses of stomatal conductance, the maximum rate of carboxylation and the ratio of intercellular to growth environment [CO2] to Topt are not only crop‐specific but also stage‐dependent. Furthermore, there is a divergence in the relationships between photosynthetic parameters for wheat and rice at Topt. We conclude that e[CO2] raises Topt of leaf photosynthesis and thus promotes Pn of winter wheat and rice in a humid subtropical climate. Further research on the coordination of leaf hydraulic and photosynthetic parameters in upland wheat and irrigated rice, as well as their response to e[CO2] should be made in the context of climate change.

Differential responses of leaf photosynthesis to insect and pathogen outbreaks: A global synthesis

Outbreak of insects or pathogens (referred to as biotic disturbance), which is projected to continually increase in a warmer climate, may profoundly affect plant photosynthesis and production. However, the response of plant photosynthesis to biotic disturbance remains unclear, especially differences in response between insects and pathogens, which hinders the prediction of plant productivity in future climate. In this study, a meta-analysis approach was used to examine effects of insects and pathogens on photosynthetic rate per unit leaf area (Pn) and the associated characteristics from 115 studies. Our results showed that biotic disturbance significantly decreased Pn by 34.8% but increased Rd by 26.2%. Most of parameters associated with Pn were significantly reduced by biotic disturbance, including gs, Tr, photosynthetic pigments (e.g., a+b, a, and b), and chlorophyll fluorescence properties (Fv/Fm, qp). The disturbance type (insects vs pathogens) was the most important factor affecting the response of Pn, with a greater decrease in Pn by pathogens (−37.5%) than insects (−28.0%). The response ratio of Pn was positively correlated with that of gs and Tr for both insects and pathogens, while negatively with Ci and positively with Chl a+b, ΦPSII, and qp for only pathogens. In addition, the higher sensitivity of Pn to biotic disturbance in crop than non-crop plants poses a great challenge to agricultural system in the future. The weighted response ratio of Pn and relationships of Pn with other associated paramerters under insect and pathogen disturbance will facilitate vegetation models to integrate the effects of biotic disturbance on primary production, improving predicition of the ecosystem carbon cyling in combining with leaf area measurement.

Time-Amplifier Enhanced Phase Noise Filter

This letter presents a time-amplifier (TA) enhanced phase noise filter (TAPNF). The PN improvement strategy and resettable low noise TA design are presented. The 10-GHz TAPNF achieves 13.6/13.4/14.4-dB PN suppression and −125/−129/−132-dBc/Hz PN sensitivity at 1-MHz offset with the 20/40/80-ns delay lines, respectively. Compared with the PNF without TA, the TAPNF demonstrates 9 dB better PN sensitivity. This TAPNF is fabricated in a 65-nm CMOS process with 1.4 mm $\times \,\, 1.6$ mm chip area and consumes 94.6-mW power.

Gluten neuropathy: prevalence of neuropathic pain and the role of gluten-free diet.

Peripheral neuropathy is a common extraintestinal manifestation of gluten sensitivity (gluten neuropathy). We aimed to establish the prevalence of neuropathic pain in patients with otherwise idiopathic PN and gluten sensitivity (positive antigliadin, endomysial, and/or transglutaminase antibodies, with or without enteropathy) and to describe any contributory factors. All consecutive patients with gluten neuropathy (GN) attending a specialist gluten/neurology clinic were invited to participate. Pain was assessed via the DN4 questionnaire and the visual analog scale. Overall Neuropathy Limitations Scale was used to assess the severity of neuropathy. The Mental Health Index (MHI-5) was used to measure participants' general mental health status. In total, 60 patients (76.7% males, mean age 69.9 ± 10.1years) with GN were recruited. Neuropathic pain was present in 33 patients (55.0%). Comparison between groups of painful and not painful GN did not show significant differences regarding age, gender, neuropathy severity and neuropathy type. Patients with painless GN were more likely to be on a strict gluten-free diet (55.6 versus 21.2%, p = 0.006). Patients with painful GN presented with significantly worse MHI-5 score (75.9 ± 13.8 versus 87.4 ± 8.1, p < 0.001). Multivariate analysis showed that, after adjusting for age, gender and MHI-5, strict gluten-free diet was associated with lowering the odds of peripheral neuropathic pain by 88.7% (95% CI 47.2-97.6%, p = 0.006). Neuropathic pain is very prevalent in GN and is associated with poorer mental health status. Strict gluten-free diet might be protective as it is associated with a significant reduction of the odds of peripheral neuropathic pain associated to GN.

Molecular Tension Probes for Imaging Forces at the Cell Surface.

Mechanical forces are essential for a variety of biological processes ranging from transcription and translation to cell adhesion, migration, and differentiation. Through the activation of mechanosensitive signaling pathways, cells sense and respond to physical stimuli from the surrounding environment, a process widely known as mechanotransduction. At the cell membrane, many signaling receptors, such as integrins, cadherins and T- or B-cell receptors, bind to their ligands on the surface of adjacent cells or the extracellular matrix (ECM) to mediate mechanotransduction. Upon ligation, these receptor-ligand bonds transmit piconewton (pN) mechanical forces that are generated, in part, by the cytoskeleton. Importantly, these forces expose cryptic sites within mechanosensitive proteins and modulate the binding kinetics (on/off rate) of receptor-ligand complexes to further fine-tune mechanotransduction and the corresponding cell behavior. Over the past three decades, two categories of methods have been developed to measure cell receptor forces. The first class is traction force microscopy (TFM) and micropost array detectors (mPADs). In these methods, cells are cultured on elastic polymers or microstructures that deform under mechanical forces. The second category of techniques is single molecule force spectroscopy (SMFS) including atomic force microscopy (AFM), optical or magnetic tweezers, and biomembrane force probe (BFP). In SMFS, the experimenter applies external forces to probe the mechanics of individual cells or single receptor-ligand complexes, serially, one bond at a time. Although these techniques are powerful, the limited throughput of SMFS and the nN force sensitivity of TFM have hindered further elucidation of the molecular mechanisms of mechanotransduction. In this Account, we introduce the recent advent of molecular tension fluorescence microscopy (MTFM) as an emerging tool for molecular imaging of receptor mechanics in living cells. MTFM probes are composed of an extendable linker, such as polymer, oligonucleotide, or protein, and flanked by a fluorophore and quencher. By measuring the fluorescence emission of immobilized MTFM probes, one can infer the extension of the linker and the externally applied force. Thus, MTFM combines aspects of TFM and SMFS to optically report receptor forces across the entire cell surface with pN sensitivity. Specifically, we provide an in-depth review of MTFM probe design, which includes the extendable "spring", spectroscopic ruler, surface immobilization chemistry, and ligand design strategies. We also demonstrate the strengths and weaknesses of different versions of MTFM probes by discussing case studies involving the pN forces involved in epidermal growth factor receptor, integrin, and T-cell receptor signaling pathways. Lastly, we present a brief future outlook, primarily from a chemists' perspective, on the challenges and opportunities for the design of next generation MTFM probes.

Photosynthesis of alfalfa (Medicago sativa) in response to landfill leachate contamination

Thousands of unlined landfills and open dumpsites have put great threat on the security of soil and ground water due to leachate leakage. Alfalfa is believed potential as a phytoremediation plant for leachate contamination based on strong root system and the excellent capacity of removing various kinds of pollutants. A lab-scale investigation was conducted to figure out the sensitiveness of alfalfa photosynthesis in response to leachate contamination. The results demonstrated that both of the maximum photosynthetic efficiency (Fv/Fm) and net photosynthetic rate (Pn) were slightly inhibited in the high-dosage group. Based on statistical analysis, higher sensitivity of Pn to leaching parameters than Fv/Fm was observed. There were significant correlations between most of leaching parameters (pH, ammonium and COD) and Pn with correlation coefficients of 0.530, −0.580 and −0.578 (p < 0.01), respectively. Therefore, Pn is potential for acting as an effective indicator for staple leaching characteristics of leachate contaminated soils.

Carbon gain optimization in five broadleaf deciduous trees in response to light variation within the crown: correlations among morphological, anatomical and physiological leaf traits

AbstractLeaf trait variations in five deciduous species (Quercus robur, Corylus avellana, Populus alba, Acer campestre, Robinia pseudoacacia) growing in an old broadleaf deciduous forest in response to light variation within the tree crown was analyzed. Net photosynthetic rate (PN), leaf respiration rate (R) and the photosynthetic nitrogen use efficiency were, on average, more than 100% higher in sun than in shade leaves. A. campestre and C. avellana sun leaves had the highest specific leaf area (SLA, 156.0 ± 17.9 cm2 g-1) and the lowest total leaf thickness (L, 101.9 ± 8.8 μm) underlining their shade-tolerance. Among the shade-intolerant species (Q. robur, P. alba and R. pseudoacacia), Q. robur had the lowest SLA and the highest L in sun leaves (130.6 ± 10.0 cm2 g-1 and 160.8 ± 9.6 μm, respectively) since shade-intolerant species typically have thicker leaves. The higher PN decrease in respect to R decrease from sun to shade leaves attested the higher sensitivity of PN than R to light variations within the crown. This determined a 69% lower R/PN in sun than in shade leaves. This result is further attested by the significant correlation between PN and the relative photosynthetic photon flux density. The shade-tolerant species have a 76% higher R/PN ratio than the shade-intolerant ones. The measured leaf phenotypic plasticity (PI = 0.35) was in the range of broadleaf deciduous species. Plasticity is a key trait useful to quantify plant response to environmental stimuli. It is defined as the ability of a genotype to produce different phenotypes depending on the environment. Among the considered species, Q. robur showed the highest PI (0.39) and P. alba the lowest (0.29). Knowledge on phenotypic plasticity is important in making hypotheses about the dynamics of the studied forest in consideration of environmental stress factors, including invasive species competition and global climate change.

Differential Sensitivity of Growth and Net Photosynthetic Rates in Five Tree Species Seedlings under Simulated Acid Rain Stress

This study investigated the effect of simulated acid rain (SAR) (heavy: pH 2.5; moderate: pH 4.0; and control: pH 5.6) stress on the growth and net photosynthetic rate (Pn) of five tree species, namely Castanopsis sclerophylla, Cinnamomum camphora, Manglietia fordiana, Pinus massoniana, and Elaeocarpus glabripetalus. Results showed variable responses to SAR with different pH values depending on the type of plants. P. massoniana seedlings exhibited significant growth reduction in response to all of the SAR treatments. The net photosynthetic rate of P. massoniana treated by SAR decreased by 20 and 34% under pH 4 and 2.5, suggesting that P. massoniana was susceptible when exposed to acid rain. These results indicate that P. massoniana was the highest sensitivity inhibitory type to SAR and should be protected. However, the growth, chlorophyll content, and Pn of three species (C. sclerophylla, C. camphora, M. fordiana) revealed the following result: moderate acid rain > control > heavy acid rain, suggesting that moderate acid rain promoted photosynthesis and growth to some extent. Among the five species, E. glabripetalus exhibited the highest extent of tolerance to acid rain. The sensitivity of growth and Pn of E. glabripetalus was significantly higher than that of the control, indicating that SAR promoted rather than inhibited its seedling, E. glabripetalus belonging to the promotional type. The stress tolerance of five species of trees to SAR was observed in the following order: E. glabripetalus > C. sclerophylla, C. camphora, M. fordiana > P. massoniana. But exposure to SAR at PH 2.5 to 5.6 did not affect the final mortality of five tree species.

DNA-Based “Digital” Tension Probes with Pn Sensitivity Reveal Early Cell Adhesion Mechanics at the Single Molecule Level

Mechanical forces are involved in important processes such as cell division, migration and gene expression, signifying their critical importance to living systems. However, the lack of methods to visualize cellular forces at the molecular scale has hampered the study of mechanotransduction. To address this need, we developed a new class of DNA-based molecular tension fluorescence microscopy (MTFM) probes that function as a reversible digital switch, and are ideally suited to investigate the pN-range forces applied by individual integrins. We show that focal adhesion maturation involves an increase in tension per molecule coupled with recruitment of a greater density of integrins. By engaging cells to sensor chips presenting mixtures of spectrally-encoded probes with different mechanical responses, we find that integrins display both chemical and mechanical specificity at the single-molecule level. Integrins show mechanical preference for more rigid ligands within nascent adhesions, thus suggesting focal adhesions function as rigidity sensors at the single integrin level. Moreover, this observation may be related to the catch bond model, where the integrin-ligand bond lifetime increases under a mechanical load.

Impairment of Leaf Photosynthesis After Insect Herbivory or Mechanical Injury on Common Milkweed, &lt;I&gt;Asclepias syriaca&lt;/I&gt;

Insect herbivory has variable consequences on plant physiology, growth, and reproduction. In some plants, herbivory reduces photosynthetic rate (Pn) activity on remaining tissue of injured leaves. We sought to better understand the influence of leaf injury on Pn of common milkweed, Asclepias syriaca (Asclepiadaceae), leaves. Initially, we tested whether Pn reductions occurred after insect herbivory or mechanical injury. We also (1) examined the duration of photosynthetic recovery, (2) compared mechanical injury with insect herbivory, (3) studied the relationship between leaf Pn with leaf injury intensity, and (4) considered uninjured leaf compensatory Pn responses neighboring an injured leaf. Leaf Pn was significantly reduced on mechanically injured or insect-fed leaves in all reported experiments except one, so some factor(s) (cardiac glycoside induction, reproductive investment, and water stress) likely interacts with leaf injury to influence whether Pn impairment occurs. Milkweed tussock moth larval herbivory, Euchaetes egle L. (Arctiidae), impaired leaf Pn more severely than mechanical injury in one experiment. Duration of Pn impairment lasted > 5 d to indicate high leaf Pn sensitivity to injury, but Pn recovery occurred within 13 d in one experiment. The degree of Pn reduction was more severe from E. egle herbivory than similar levels of mechanical tissue removal. Negative linear relationships characterized leaf Pn with percentage tissue loss from single E. egle-fed leaves and mechanically injured leaves and suggested that the signal to trigger leaf Pn impairment on remaining tissue of an injured leaf was amplified by additional tissue loss. Finally, neighboring uninjured leaves to an E. egle-fed leaf had a small (approximately 10%) degree of compensatory Pn to partly offset tissue loss and injured leaf Pn impairment.

Impairment of Leaf Photosynthesis After Insect Herbivory or Mechanical Injury on Common Milkweed,Asclepias syriaca

Insect herbivory has variable consequences on plant physiology, growth, and reproduction. In some plants, herbivory reduces photosynthetic rate (Pn) activity on remaining tissue of injured leaves. We sought to better understand the influence of leaf injury on Pn of common milkweed, Asclepias syriaca (Asclepiadaceae), leaves. Initially, we tested whether Pn reductions occurred after insect herbivory or mechanical injury. We also (1) examined the duration of photosynthetic recovery, (2) compared mechanical injury with insect herbivory, (3) studied the relationship between leaf Pn with leaf injury intensity, and (4) considered uninjured leaf compensatory Pn responses neighboring an injured leaf. Leaf Pn was significantly reduced on mechanically injured or insect-fed leaves in all reported experiments except one, so some factor(s) (cardiac glycoside induction, reproductive investment, and water stress) likely interacts with leaf injury to influence whether Pn impairment occurs. Milkweed tussock moth larval herbivory, Euchaetes egle L. (Arctiidae), impaired leaf Pn more severely than mechanical injury in one experiment. Duration of Pn impairment lasted >5 d to indicate high leaf Pn sensitivity to injury, but Pn recovery occurred within 13 d in one experiment. The degree of Pn reduction was more severe from E. egle herbivory than similar levels of mechanical tissue removal. Negative linear relationships characterized leaf Pn with percentage tissue loss from single E. egle –fed leaves and mechanically injured leaves and suggested that the signal to trigger leaf Pn impairment on remaining tissue of an injured leaf was amplified by additional tissue loss. Finally, neighboring uninjured leaves to an E. egle –fed leaf had a small (≈10%) degree of compensatory Pn to partly offset tissue loss and injured leaf Pn impairment.

Direct Observation of Anisotropic Interparticle Forces in Nematic Colloids with Optical Tweezers

Interparticle forces in a nematic liquid-crystal colloid have been directly observed by the dual beam laser trapping method with pN sensitivity. We introduce two different types of spatial distributions of forces, detected between the particles accompanied by hyperbolic hedgehog defects. These force distributions lead to specific particle arrangements, which are both stabilized by the balance of the orientational stress field of nematics. On the basis of these results, we propose novel artificial construction for multiparticle regular arrangements.

Simultaneous measurement of the migration velocity and adsorption force of micro-particles using an electromagnetophoretic force under a high magnetic field.

A simultaneous measurement technique for determining the migration velocity of a micrometer-sized particle in a capillary and the adsorption force to the inner surface of the capillary has been proposed. This technique is based on an electromagnetophoretic force being exerted on a micro-particle in an electrolyte solution, which is governed mainly by the electromagnetic buoyancy, when a homogeneous magnetic field is applied at a right angle to the electric current through the medium. By the electromagnetic buoyancy, micro-particles such as polystyrene, carbon and yeast were migrated perpendicular to the direction of the electric current and reached a fused-silica wall. A switching of the current direction could desorb the particle from the wall, and allowed to calculate the detaching force from the desorbing current. The migration velocity normalized to the size in the magnetic field of 10 T was increased in the order of yeast, carbon and polystyrene, while reflecting the decreasing order of the apparent conductivity of the particles. The desorption force could be measured up to 1 nN with a sensitivity of pN. The observed interaction forces of polystyrene and carbon were in the range of 250-600 pN with large deviations.

Seasonal trends in leaf photosynthesis and stomatal conductance of drought stressed and nonstressed pearl millet as associated to vapor pressure deficit

Single leaf photosynthesis (Pn) and stomatal conductance (Cg) of drought stressed and nonstressed pearl millet [Pennisetum americanum (L.) Leeke] were measured across growth stages to determine if a pattern exists in Pn and Cg during the growing season and to evaluate the influence of air vapor pressure deficit (VPDa) on the seasonal variations of Pn and Cg. Leaf photosynthesis and Cg were measured independently on pearl millet plants grown at the driest (drought stressed) and wettest (nonstressed) ends of a line-source irrigation gradient system. Well defined and predictable variations in both Pn and Cg were found across two growing seasons. Leaf photosynthesis of the nonstressed plants declined from a maximumof 25.8 μmol m(-2) s(-1) at the flag leaf emergence (48 days after planting, DAP) to a minimum of 14.5 μmol m(-2) s(-1) at physiological maturity. Stomatal conductance of the nonstressed plants peaked at the flowering and early grain fill stages and declined as plants approached maturity. In contrast, Pn and Cg of the stressed plants declined from a maximum at flag leaf emergence to a minimum at flowering and increased as plants approached maturity. High VPDa during the flowering and grain fill stages induced stomatal closure and decreased Pn in the stressed plants. High mid-season VPDa did not induce stomatal closure and did not reduce leaf photosynthesis in nonstressed plants. The lack of sensitivity of Pn to VPDa in the nonstressed treatment suggests large air VPD such as that prevalent in southern Arizona does not limit the growth of irrigated pearl millet by limiting CO2 assimilation.