Facilitated Diffusion Of CO2 Research Articles

Tissue-specific accumulation of PIP aquaporins of a particular heteromeric composition is part of the maize response to mycorrhiza and drought

The systemic coordination of accumulation of plasma membrane aquaporins (PIP) was investigated in this study in relation to mycorrhized maize response to a rapid development of severe drought followed by rewatering. In non-mycorrhizal roots, drought led to a drop in PIP abundance, followed by a transient increase under rewatering, whereas leaves showed an opposite pattern. In contrast, mycorrhiza contributed to maintenance of high and stable levels of PIPs in both plant organs after an initial increase, prolonged over the irrigation period. Isoelectric focusing electrophoresis resolved up to 13 aquaporin complexes with highly reproducible pl positions across leaf and root samples, symbiotic and non-symbiotic, stressed or not. Mass spectrometry recognized in leaves and roots a different ratio of PIP1 and PIP2 subunits within 2D spots that accumulated the most. Regardless of symbiotic status, drought regulation of aquaporins in roots was manifested as the prevalence of complexes that comprise almost exclusively PIP2 monomers. In contrast, the leaf response involved enrichment in PIP1s. PIP1s are thought to enhance water transport, facilitate CO2 diffusion but also affect stomatal movements. These features, together with elevated aquaporin levels, might explain a stress tolerance mechanism observed in mycorrhizal plants, resulting in faster recovery of stomatal water conductance and CO2 assimilation rate after drought.

Effect of hollow natural fiber (HNF) content on the CO2 diffusion, carbonation, and strength development of reactive magnesium cement (RMC)-based composites

Reactive magnesia cement (RMC) is an emerging class of green cement that hardens by sequestering CO2. However, CO2 diffusion into RMC is restricted to a few millimeters by the carbonation-induced dense microstructure on the outer layer, which severely slows down the strength growth and CO2 sequestration. To address this issue, this work employed hollow natural fibers (HNFs) to facilitate CO2 diffusion into the deep regions of RMC. The effects of HNFs contents on the mechanical strength development, holistic porosity, CO2 sequestration, CO2 diffusivity, and microstructure of RMC were investigated through different techniques. The findings revealed that the compressive strength could be more than doubled with the addition of adequate sisal fiber. Moreover, the CO2 sequestration and diffusivity could be continuously enhanced with the increasing HNFs content. However, overdosage of HNFs could induce a higher porosity and additional defects, which slightly compromises the mechanical strength. Finally, the durability of HNFs in simulated RMC and Portland cement (PC) environment was compared by accelerated aging test, showing that the alkaline-induced deterioration of HNFs could be almost eliminated in RMC. Therefore, this preliminary study reinforces the function of RMC as a carbon reservoir and lays the foundation for the large-scale utilization of HNFs in RMC.

Leaf and wood functional traits explain the strategies developed by Byrsonima sericea (Malpighiaceae) to survive in Atlantic Forest ecosystems under water and light variations

The Atlantic Forest is a heterogeneous biome comprised of different phytophysiognomies with contrasting microclimatic and edaphic characteristics, such as sandbanks and forests. Sandbanks are ecosystems with low water availability and high irradiance, requiring leaf and wood specific adjustments from species to survive. On the other hand, tropical rain forests lack a pronounced dry season, providing enough resources to allow competition from light-demanding trees and sustaining a spectrum of shade tolerance for understory species. To better understand how functional traits are determined, it is necessary to evaluate variables that are site-specific, i.e. that are displayed within an organism in different environments. We aimed to assess how does variation in the functional traits of the leaf and wood of Byrsonima sericea influence the survival abilities of this species to thrive under contrasting scenarios of light and water availability. Also, which set of morpho-anatomical and physiological traits are considered to be site-specific responses that are affecting positively the capacity of the species to adapt in these contrasting scenarios of the Atlantic Forest? The high irradiance in sandbank shaped functional traits of B. sericea leaves that allowed an allocation strategy of the available resources, with investment in leaf mass rather than in trunk biomechanics and hydraulic efficiency. The higher leaf density through smaller and numerous cells along with higher stomatal density and area, facilitating CO2 diffusion, were associated with a greater photosynthetic capacity and greater intrinsic water use efficiency. As in the forest, light is a limiting factor for species to grow, the fluctuating light over a short timescale can influence whole plant performance, thus requiring an investment in trunk biomechanics. Additionally, a set of wood traits in the forest was related to water availability favoring wider vessel elements with thicker walls, increasing the theoretical hydraulic conductivity, even though it implicated a higher vulnerability to cavitation. Our study has demonstrated that variation of traits of different plant structures, such as the leaf and wood, within a species has direct implications in the survival strategies at each environmental conditions of light and water availability. It is also stated that there are different sets of functional traits which are responsible for allocation strategies, leading to specific trade-offs that allow the species to display site-specific responses in order to survive.

Enhancing MgO efficiency in CO2 capture: engineered MgO/Mg(OH)2 composites with Cl-, SO42-, and PO43- additives.

The formation of a MgCO3 shell hampers CO2 capture efficiency in MgO. Our previous studies developed MgO/Mg(OH)2 composites to facilitate CO2 diffusion, improving capture efficiency. However, MgCO3 still formed along the interfaces. To tackle this issue, we engineered the MgO/Mg(OH)2 interfaces by incorporating Cl-, SO42-, and PO43- additives. Novel MgO-H2O-MgX (X = Cl-, SO42-, and PO43-) composites were synthesized to explore the role of additives in preventing MgCO3 formation. MgO-Mg(OH)2-MgCl2 nano-composites displayed enhanced CO2 adsorption and stability. This breakthrough paves the way for effective bio-inspired strategies in overcoming CO2 transport barriers in MgO-based adsorbents.

Hyper cross‐linked polymers containing amino group functionalized polyimide mixed matrix membranes for gas separation

AbstractThe design and synthesis of porous materials with novel structures and functional groups to prepare mixed matrix membranes (MMMs) is an effective way to break through trade‐off effect of membrane technology. Here, hyper cross‐linked polymers containing amino groups (HCPs‐NH2) with philic‐CO2 frame were successfully prepared for the fabrication of polyimide (PI)/HCPs‐NH2 MMMs. The separation performance of pure gas is studied in order to explore NH2 groups facilitating CO2 diffusion and transmission and enhancing CO2 permeability. Consequently, the permeability of the PI/HCPs‐NH2 MMMs toward CO2 and O2 are 77.56 Barrer and 17.91 Barrer versus pure PI film toward CO2 and O2 (62.42 Barrer and 13.85 Barrer). The selectivity for CO2/CH4 and O2/N2 pairs is 24.44 and 4.01, and the selectivity of pure PI film toward CO2/CH4 and O2/N2 pairs is 20.76 and 3.29, respectively. The permeability and selectivity of PI/HCPs‐NH2 MMMs are higher than pure PI film breaking through the trade‐off effect. Moreover, the PI/HCPs‐NH2 MMMs show better separation performance on the CO2/CH4 pair than the O2/N2 pair, indicating HCPs‐NH2 with philic‐CO2 frame plays a very important role in promoting CO2 permeability. Thus, the PI/HCPs‐NH2 MMMs have potential applications in the field of natural gas purification.

Aquaporin expression and cholesterol content in eel swimbladder tissue.

Leakiness of the swimbladder wall of teleost fishes must be prevented to avoid diffusional loss of gases out of the swimbladder. Guanine incrustation as well as high concentrations of cholesterol in swimbladder membranes in midwater and deep‐sea fish has been connected to a reduced gas permeability of the swimbladder wall. On the contrary, the swimbladder is filled by diffusion of gases, mainly oxygen and CO2, from the blood and the gas gland cells into the swimbladder lumen. In swimbladder tissue of the zebrafish and the Japanese eel, aquaporin mRNA has been detected, and the aquaporin protein has been considered important for the diffusion of water, which may accidentally be gulped by physostome fish when taking an air breath. In the present study, the expression of two aquaporin 1 genes (Aqp1aa and Aqp1ab) in the swimbladder tissue of the European eel, a functional physoclist fish, was assessed using immunohistochemistry, and the expression of both genes was detected in endothelial cells of swimbladder capillaries as well as in basolateral membranes of gas gland cells. In addition, Aqp1ab was present in apical membranes of swimbladder gas gland cells. The authors also found high concentrations of cholesterol in these membranes, which were several fold higher than in muscle tissue membranes. In yellow eels the cholesterol concentration exceeded the concentration detected in silver eel swimbladder membranes. The authors suggest that aquaporin 1 in swimbladder gas gland cells and endothelial cells facilitates CO2 diffusion into the blood, enhancing the switch‐on of the Root effect, which is essential for the secretion of oxygen into the swimbladder. It may also facilitate CO2 diffusion into the swimbladder lumen along the partial gradient established by CO2 production in gas gland cells. Cholesterol has been shown to reduce the gas permeability of membranes and thus could contribute to the gas tightness of swimbladder membranes, which is essential to avoid diffusional loss of gas out of the swimbladder.

Synthesis and evaluation in the CO2 capture process of potassium-modified lithium silicates produced from steel metallurgical slags

Lithium silicate-based CO2 sorbents were successfully synthesized using steel metallurgical slags as silica sources, with and without K2CO3 addition (10−30 wt%). The CO2 capture efficiency improved with K2CO3 addition because of the formation of a eutectic phase between K2CO3 and Li2CO3, which facilitated CO2 diffusion into the material bulk. The best capture capacity value (104 mgCO2/gmaterial) was obtained using the material produced from steel metallurgical slag with 20 wt% K2CO3 (SK0.2) at 600 °C and with either 5 or 20 vol% CO2. In addition, the CO2 capture rate increased up to four orders of magnitude in the diffusion-controlled stage compared to material prepared with fumed silica or F (K2 = 2.89 E-3 s−1 for SK0.2 and K2 = 4.21 E-8 s−1 for F). After 20 adsorption-desorption cycles using 20 vol% CO2, the CO2 capture capacity of SK0.2 was reduced by only 10 %, indicating excellent thermal stability.

CO2 capture and mineralization using carbide slag doped fly ash

AbstractA novel direct gas–solid mineral carbonation process using carbide slag doped fly ash to capture and mineralize CO2 from flue gas was developed to overcome the barriers of long reaction time and large reactor size from aqueous processes. A laboratory‐scale fixed bed reactor with a thermogravimetric analyser and a pilot‐scale circulating entrained‐flow bed (CEB) rector system were constructed to investigate the intensification method and reaction parameters. The carbonation efficiency (ζCa [%]) was improved four times by carbide slag doped fly ash in a semi‐dry atmosphere; thus, the active calcium hydroxide from carbide slag and fly ash can react with CO2 in a thin liquid film through an ionic reaction route. The key reaction parameters, such as temperature, steam addition and water injection, were studied to promote Ca(OH)2 formation and to facilitate CO2 diffusion. As a result of the pilot‐scale experiment, carbonation efficiency achieved a maximum value of 55% with 15% steam addition in the feed and 6 kg h–1 water injection into CEB at 550 °C. © 2019 Society of Chemical Industry and John Wiley & Sons, Ltd.

Mixed-matrix carbon molecular sieve membranes using hierarchical zeolite: A simple approach towards high CO2 permeability enhancements

Membrane process is a robust technology for CO2/CH4 separation. To achieve the energy-efficiency necessary for a cost-effective membrane-based CO2/CH4 separation, high-performance membranes are often desirable. There are several approaches that can be undertaken to realize such membranes. In this study, we amalgamated three strategies: 1) filler design optimization by synthesizing hierarchical zeolite 5A comprising micro and mesoporous domains to strengthen the second strategy; 2) mixed-matrix approach by incorporating zeolite fillers to facilitate CO2 diffusion and reduce transport resistance through a Matrimid® matrix; and 3) membrane carbonization to induce thermal rearrangement, and create free volumes and pore apertures for a faster CO2 transport. These efforts afforded mixed-matrix carbon molecular sieve membranes with results confirming that our membrane at 30 wt% loading of hierarchical zeolite 5A was able to surpass the 2008 Robeson upper bound limit given a performance of 2450 barrers CO2 permeability and 19.3 CO2/CH4 selectivity. Notably, at this loading, the negative effect brought by the interfacial nanogaps between the filler and carbon matrix diminished, unleashing the potential of the mesopores in facilitating CO2 diffusion, which led to a two orders of magnitude enhancement in the CO2 permeability relative to the unfilled carbon molecular sieve membrane. Despite a decrease in the CO2/CH4 selectivity, the hierarchical zeolite 5A is effective in alleviating the intensity of the permeability-selectivity trade-off. Also, benchmarking of the filler effectiveness is first demonstrated using a new filler enhancement index, Findex. The largest Findex value in this study was 1.97. This attaches a label of “competent” to our hierarchical zeolite 5A filler at 30 wt% loading, demonstrating the success of our strategies.

Influence of water vapor on cyclic CO2 capture performance in both carbonation and decarbonation stages for Ca-Al mixed oxide

Little research was carried out to study the effect of water vapor with different contents on the CO2 adsorption performance during extending cycles in both carbonation and decarbonation stages. This study described the CO2 adsorption performance of Ca-Al mixed oxides under different water vapor concentrations. The results revealed that the reactivity and durability of both fresh and spent sorbents were remarkably enhanced by adding water vapor. The initial CO2 carbonation capacity increased from 56 wt% without water to 70.7 wt% with 1.6% water vapor at the adsorption temperature of 600 °C. The stability of Ca-Al mixed oxides was also investigated during 220 cycles with 1% steam vapor. The CO2 adsorption capacity retained 55.6 wt% after 220 cycles, indicating an excellent long-term durability. The excellent CO2 adsorption capacity and stability of the mixed oxides in the existence of water vapor may be attributed to the following reasons: water vapor facilitated CO2 diffusion in the CaCO3 product layer during the carbonation stage as well as the decomposition rate of CaCO3 during the calcination stage; water vapor facilated the formation of the loose porous structure, which was favorable for the subsequent carbonation of CaO.

Li-LSX-zeolite evaluation for post-combustion CO2 capture

Lithium low silica X type (Li-LSX) zeolite is typically used for industrial N2/O2 separation processes, but its potential as a carbon dioxide capture sorbent has not been fully evaluated yet. In this work, Li-LSX zeolite was investigated as CO2 sorbent under post- combustion conditions in TGA and Fixed-bed configurations. The maximum adsorption capacity and CO2/N2 selectivity were determined to be 4.43 mmol g−1 and 85.7 at 60 °C and in presence of 14% CO2, using a packed bed configuration. The CO2 and N2 adsorption capacity was decreased of 10 mol% when the initial calcination temperature was raised from 60 to 300 °C due to a decreased micropore surface. However, the high calcination temperature increased the CO2 selectivity to 128.1 and increased the adsorption rates due to enhanced basicity (1 order of magnitude) and external surface (+75 to 80%) in the Li-LSX zeolite.The sorption stability at 60 °C was found to be excellent during 85 sorption cycles over 35 h period with Li-LSX showing negligible difference in adsorption capacity throughout the cycles and a working capacity of 2.45 mmolCO2/g after an initial calcination at 550 °C (2 min) and cyclic adsorption at 60 °C (6 min) and desorption at 420 °C (5 min). The Avrami kinetic model shows the coexistence of different adsorption mechanisms. CO2 adsorption rate increased with the increasing CO2 partial pressure, as a result of the facilitated CO2 diffusion processes. Film diffusion was determined as the rate-limiting step for CO2 adsorption. Therefore, based on these findings, Li-LSX represents a promising sorbent for post-combustion carbon capture.

Al-Stabilized Double-Shelled Hollow CaO-Based Microspheres with Superior CO2 Adsorption Performance

Novel, double-shelled hollow Al-stabilized CaO-based microspheres were successfully prepared through a facile, green method using carbonaceous microspheres as sacrificial templates. Both the morphological and adsorption performance differences, between employing organic and inorganic calcium salt as calcium precursors, to fabricate the double-shelled hollow microspheres were exhibited. Derived from calcium acetate, the Al-stabilized double-shelled hollow microspheres with denser shells showed excellent stability. This was ascribed to the shells that were composed of small CaCO3 nanocrystallite (grain size of <50 nm) and homogeneously distributed stabilizer, Al2O3. Well-spherical, porous hollow structures facilitated CO2 diffusion and buffered mechanical stresses generated by volume change during the calcium looping. The sorbent, CaA40Al1, exhibited a favorable high-temperature CO2 adsorption performance with the capacity of 0.40 g of CO2/g of ads over 60 carbonation/calcination cycles.

Creviced titanate nanotube modified with stearyl trimethyl ammonium bromide as a support for amine-based CO2 sorbent

In this paper, a series of protonated titanate nanotubes (PTNTs) modified by stearyl trimethyl ammonium bromide (STAB) were prepared as supports for Polyethyleneimine (PEI)-based sorbents. The CO2 adsorption performance was evaluated in a self-assembled fixed bed reactor. The typical sorbents were characterized by XRD, EDS, SEM, HR-TEM, N2 adsorption-desorption, FT-IR and TGA. Results indicate that the modification significantly improves CO2 adsorption capacity of the sorbents. The maximum CO2 adsorption amount of 2.22 mmol/g was obtained over the modified PEI-based sorbent in 2% CO2/air. Based on the characteristic analysis, the formation of creviced nanotubes, instead of intact nanotubes, is testified because of the modification. Such unique nanotubes possess the higher BET surface area and larger pore volume, which enables more PEI to uniformly distribute on the surface of modified PTNT supports. Especially, it is easier for PEI to enter the inner pores through the crevice than from tube orifices, avoiding pore blockage and facilitating CO2 diffusion in pores. The abundant amine-sites and small internal diffusion resistance endow the modified sorbent with large CO2 adsorption capacity. In addition, the PEI/PTNT adsorbent displays good thermal stability and reusability.

Molecular dynamics simulations of CO2 permeation through ionic liquids confined in γ-alumina nanopores

CO2 permeation through imidazolium-based ionic liquids (ILs, [BMIM][Ac], [EMIM][Ac], [OMIM][Ac], [BMIM][BF4], and [BMIM][PF6]) confined in 1.0, 2.0, and 3.5 nm γ-alumina pores was investigated using molecular dynamics simulation. It was found that the nanopore confinement effect influenced the structure of confined ILs greatly, resulting in a layered structure and anisotropic orientation of ILs. In the center of 2.0-nm pore, the long alkyl chain of [BMIM]+ tended to be parallel to the wall, providing a straight diffusion path benefiting the CO2 permeation. The CO2 diffusion coefficients in confined [EMIM][Ac], [BMIM][Ac], and [OMIM][Ac] were 2.3–4.1, 2.4–6.4, and 14.4–21.7 × 10−10 m2 s−1, respectively. This order was opposite to that in the bulk ILs, because the longer alkyl chain led to a more ordered structure, facilitating CO2 diffusion. In addition, the CO2 solubilities were 445–722 mol m−3 MPa−1 for the five ILs confined in 1.0 nm pore, which were larger than those in 2.0 and 3.5 nm pores (196–335 mol·m−3 MPa−1), due to the larger free volume. Both parallel orientation of alkyl chain and large free volume could increase the CO2 permeability in confined ILs.

Experimental warming enhances the carbon gain but does not affect the yield of maize (Zea mays L.) in the North China Plain

Temperature response and sensitivity of photosynthesis and respiration are critical for projection of changes in the carbon exchange and net primary production of terrestrial ecosystems under global warming. Understanding the mechanisms and processes of photosynthetic and respiratory acclimation in response to warming may shed further lights on the change of crop yield in agricultural ecosystems in a warmer climate regime. We examined the temperature responses and sensitivity of net photosynthetic rate (An) and dark respiration (Rd) for exploring the mechanisms of thermal acclimation associated with physiological and biochemical processes affecting maize yield in the North China Plain with a field manipulative warming experiment. We found that warming substantially enhanced the carbon gain of maize plants through facilitating CO2 diffusion from ambient air to chloroplasts by altering stomatal structure and spatial distribution pattern, and benefitting CO2 assimilation efficiency with smaller vascular bundles and bigger chloroplasts. Moreover, we also found that acclimation of An to temperature (T), evidenced by the upward shift of An–T, was determined by the maximum velocity of Rubisco carboxylation (Vcmax), the maximum rate of electron transport (Jmax), and the stomatal-regulated CO2 diffusion process, whereas the balance between respiration and gross photosynthetic rate (Rd/Ag), and/or regeneration of RuBP and the Rubisco carboxylation (Jmax/Vcmax) made little contribution to the thermal acclimation of An in maize plants. In addition, temperature response and sensitivity of Rd was closely associated with the changes in foliar N concentration induced by warming. As a result, experimental warming barely affected the yield and biomass of maize plants. These results suggest that the impacts of future climate warming on maize production may be mitigated or even offset by the leaf-level thermal acclimation of photosynthesis and respiration. Our findings may have important implications for improving the accuracy of process-based ecosystem models and advancing the understanding on the interactions between ecosystem functions and climate warming.

Fabrication of multi-shelled hollow Mg-modified CaCO3 microspheres and their improved CO2 adsorption performance

Novel multi-shelled hollow Mg-modified CaCO3 microspheres were successfully prepared through a facile, green method by using carbonaceous microsphere as a template with controllable Ca/Mg molar ratio, size and shells number. The triple-shelled hollow microspheres structure facilitated CO2 diffusion and buffered mechanical stresses of volume change during the carbonation/calcination process. Connected with sintering-resistance of inert Mg-modification, the Mg-doped CaCO3 triple-shelled hollow microspheres had collapse resistance, fast adsorption kinetics, improved CO2 adsorption capacity and calcium looping stability. The sorbent exhibited a favorable high temperature CO2 adsorption performance with the capacity of 0.51g-CO2/g-ads after 50 carbonation/calcination cycles and 92.4% of the initial maximal sorption in only 3min.

CO2 Sorption Durability of Zr-Modified Nano-CaO Sorbents with Cage-like Hollow Sphere Structure

Novel Zr-modified nano-CaO sorbents with cage-like hollow sphere structure were prepared for increasing the durability of CO2 sorption via an ion precipitation method using carbon spheres as a template. A thorough study on the influence of the Ca/Zr molar ratio and the effect of cage-like structure on the CO2 sorption durability of the prepared sorbents was performed using thermogravimetric analysis. It was found that the optimum Ca/Zr molar ratio of 5 maintained the most favorable CO2 sorption stability, which maintained a CaO conversion of 76% after 30 cycles, whereas the CaO conversion of a nano-CaO cage-like hollow sphere sorbent without Zr-modification decayed to 20%. The combination of the Zr-modification and the cage-like structure demonstrates a synergistic effect in enhancing the CaO conversion and sorption stability due to the formation of CaZrO3 with a cage-like porous structure, which facilitated CO2 diffusion and minimized thermal sintering. Furthermore, a detailed comparison was made among t...

Self-Activation Mechanism Investigations on Large K2CO3-Doped Li4SiO4 Sorbent Particles

This work investigated the self-activation behavior of large K2CO3-doped Li4SiO4 sorbent particles. In this self-activation mechanism, the sorption ability increased as the number of cycles increased. After the sorption–desorption cycles occurred, the sorption ability of the K2CO3-doped Li4SiO4 sorbent was remarkably enhanced from approximately 2.0 mmol CO2/g sorbent to approximately 5.0 mmol CO2/g sorbent at 565 °C in 10 vol % CO2 atmosphere. The fresh and used sorbents were then characterized through N2 adsorption and SEM methods. Results showed that the average pore size increased from 7 to 32 nm and the surface microstructure changed from dense to porous, because the molten eutectic mixture formed by Li2CO3 and Li2SiO3 can facilitate CO2 diffusion. The formed CO2 diffusion channel can provide more CO2 accessibility; this channel can also reduce the CO2 diffusion resistance through the product layer. Therefore, the sorption ability of the sorbent is enhanced. Meanwhile, the effects of the self-activation temperature were also investigated and the results revealed that the optimal self-activation temperature is 615 °C. Furthermore, under critical conditions, the self-activated sorbent performed more efficiently than the fresh sample. At 450 °C under 10 vol % CO2 atmosphere, the sorption capacity of the self-activated sorbent was approximately 20 times higher than that of the fresh sample. Finally, a pore–core model was also proposed to illustrate the K2CO3-doped Li4SiO4 self-activation mechanism.

Physiological and biochemical mechanisms of the ornamental Eugenia myrtifolia L. plants for coping with NaCl stress and recovery.

We studied the response of Eugenia myrtifolia L. plants, an ornamental shrub native to tropical and subtropical areas, to salt stress in order to facilitate the use of these plants in Mediterranean areas for landscaping. E. myrtifolia plants implement a series of adaptations to acclimate to salinity, including morphological, physiological and biochemical changes. Furthermore, the post-recovery period seems to be detected by Eugenia plants as a new stress situation. Different physiological and biochemical changes in Eugenia myrtifolia L. plants after being subjected to NaCl stress for up to 30 days (Phase I) and after recovery from salinity (Phase II) were studied. Eugenia plants proved to be tolerant to NaCl concentrations between 44 and 88 mM, displaying a series of adaptative mechanisms to cope with salt-stress, including the accumulation of toxic ions in roots. Plants increased their root/shoot ratio and decreased their leaf area, leaf water potential and stomatal conductance in order to limit water loss. In addition, they displayed different strategies to protect the photosynthetic machinery, including the limited accumulation of toxic ions in leaves, increase in chlorophyll content, changes in chlorophyll fluorescence parameters, leaf anatomy and antioxidant defence mechanisms. Anatomical modifications in leaves, including an increase in palisade parenchyma and intercellular spaces and decrease in spongy parenchyma, served to facilitate CO2 diffusion in a situation of reduced stomatal aperture. Salinity produced oxidative stress in Eugenia plants as evidenced by oxidative stress parameters values and a reduction in APX and ASC levels. Nevertheless, SOD and GSH contents increased. The post-recovery period is detected as a new stress situation, as observed through effects on plant growth and alterations in chlorophyll fluorescence and oxidative stress parameters.

Gas-tight triblock-copolymer membranes are converted to CO2 permeable by insertion of plant aquaporins

We demonstrate that membranes consisting of certain triblock-copolymers were tight for CO2. Using a novel approach, we provide evidence for aquaporin facilitated CO2 diffusion. Plant aquaporins obtained from heterologous expression were inserted into triblock copolymer membranes. These were employed to separate a chamber with a solution maintaining high CO2 concentrations from one with depleted CO2 concentrations. CO2 diffusion was detected by measuring the pH change resulting from membrane CO2 diffusion from one chamber to the other. An up to 21 fold increase in diffusion rate was determined. Besides the supply of this proof of principle, we could provide additional arguments in favour of protein facilitated CO2 diffusion to the vivid on-going debate about the principles of membrane gas diffusion in living cells.