Lower Gas Exchange Research Articles

Engineering metal-covalent organic framework-based hybrid oxygenation membranes for facilitated blood-gas exchange

Oxygenation membranes operate as indirectly contacting barriers between blood and gas in extracorporeal membrane oxygenation (ECMO), improving oxygenation and removing carbon dioxide from blood. However, the low gas exchange efficiency of the current poly (4-methyl-1-pentene) (PMP) artificial lung membrane results in a high prime volume. Facilitated transport membrane is a fascinating strategy to construct high-performance membranes for blood-gas exchange. This study put forward hybrid strategy by using metal-covalent organic frameworks (MCOFs) to construct facilitated transport membrane of PMP flat membranes and hollow fiber membranes (HFMs) via thermally induced phase separation (TIPS) to achieve facilitated blood-gas exchange. Cu-TAPB-COF nanosheets (CuCON) with framework structure and abundant active metal sites were synthetized and introduced into PMP to construct hybrid oxygenation membranes, reducing the resistance of gas exchange channels and ensuring the high affinity toward CO2 and O2. Cu+ and benzene rings existed in aromatic skeleton as well as the tunable structure, that could ensure the stability of MCOF and the uniform distribution of facilitated transport sites. The prepared PMP-CuCON-1 HFMs exhibited O2 and CO2 exchange rate of ∼467.5 ml min−1 m−2 and ∼309.1 ml min−1 m−2 in blood gas exchange process, which was 143.1% and 261.3% higher than the commercial PMP HFM, respectively. Asymmetric structure ensured resistance to plasma leakage for more than two weeks, and Cu+ kept stable in CuCON and hybrid membranes. The hybrid membrane exhibited superior blood-gas exchange performance and good hemocompatibility, possessing great potential for application.

Unexpected low CO2 emission from highly disturbed urban inland waters

Constituents and functionality of urban inland waters are significantly perturbed by municipal sewage inputs and tailwater discharge from wastewater treatment plants. However, large knowledge gaps persist in understanding greenhouse gas dynamics in urban inland waters due to a lack of in situ measurements. Herein, via a 3-year field campaign (2018–2020), we report river and lake CO2 emission and related aquatic factors regulating the emission in the municipality of Beijing. Mean pCO2 (546 ± 481 μatm) in the two urban lakes was lower than global non-tropical freshwater lakes and CO2 flux in 47% of the lake observations was negative. Though average pCO2 in urban rivers (3124 ± 3846 μatm) was among the higher range of global rivers (1300–4300 μatm), average CO2 flux was much lower than the global river average (99.7 ± 147.5 versus 358.4 mmol m−2 d−1). The high pCO2 cannot release to the atmosphere due to the low gas exchange rate in urban rivers (average k600 of 1.3 ± 1.3 m d−1), resulting in low CO2 flux in urban rivers. Additionally, eutrophication promotes photosynthetic uptake and aquatic organic substrate production, leading to no clear relationships observed between pCO2 and phytoplankton photosynthesis or dissolved organic carbon. In consistence with the findings, CO2 emission accounted for only 32% of the total greenhouse gas (GHG) emission equivalence (CO2, CH4 and N2O) in Beijing waters, in contrast to a major role of anthropogenic CO2 to anthropogenic GHG in the atmosphere in terms of radiative forcing (66%). These results pointed to unique GHG emission profiles and the need for a special account of urban inland waters in terms of aquatic GHG emissions.

Absence of aluminium compromises root integrity, reduces leaf hydration and Rubisco performance in Qualea grandiflora, an Al-accumulating species.

Aluminium (Al) is toxic to most plants. Nevertheless, some species accumulate Al without showing toxicity symptoms. Previous studies have evidenced Al in chloroplasts of Al-accumulating species from the Cerrado vegetation in South America. We ask whether Al increases carbon assimilation through enhanced apparent efficiency of Rubisco. Seedlings of the Al-accumulator Qualea grandiflora (Vochysiaceae) were grown in nutrient solution with 0, 740, and 1480 μm Al. Growth parameters, relative leaf water content, Al concentration in organs, gas exchange and apparent carboxylation efficiency (measured from A/Ci curves) were evaluated for 60 days. Plants without Al showed no root growth, necrotic roots, low gas exchange rates, and decreased apparent carboxylation efficiency. Al-treated plants, however, showed new white roots and increased root biomass leading to higher leaf hydration, and apparent carboxylation efficiency was higher in these plants. Increased Al available in the nutrient solution increased Al accumulation in plant organs. Absence of Al compromised root integrity in Q. grandiflora, thus limiting leaf hydration. No positive direct effect of Al on Rubisco was evidenced in Al-treated plants.

The trajectory in catalytic evolution of Rubisco in Posidonia seagrass species differs from terrestrial plants.

The CO2-fixing enzyme Ribulose bisphosphate carboxylase-oxygenase (Rubisco) links the inorganic and organic phases of the global carbon cycle. In aquatic systems, the catalytic adaptation of algae Rubiscos has been more expansive and followed an evolutionary pathway that appears distinct to terrestrial plant Rubisco. Here, we extend this survey to differing seagrass species of the genus Posidonia to reveal how their disjunctive geographical distribution and diverged phylogeny, along with their CO2 concentrating mechanisms (CCMs) effectiveness, have impacted their Rubisco kinetic properties. The Rubisco from Posidonia species showed lower carboxylation efficiencies and lower sensitivity to O2 inhibition than those measured for terrestrial C3 and C4-plant Rubiscos. Compared with the Australian Posidonia species, Rubisco from the Mediterranean Posidonia oceanica had 1.5-2-fold lower carboxylation and oxygenation efficiencies, coinciding with effective CCMs and five Rubisco large subunit amino acid substitutions. Among the Australian Posidonia species, CCM effectiveness was higher in Posidonia sinuosa and lower in the deep-living Posidonia angustifolia, likely related to the 20%-35% lower Rubisco carboxylation efficiency in P. sinuosa and the two-fold higher Rubisco content in P. angustifolia. Our results suggest that the catalytic evolution of Posidonia Rubisco has been impacted by the low CO2 availability and gas exchange properties of marine environments, but with contrasting Rubisco kinetics according to the time of diversification among the species. As a result, the relationships between maximum carboxylation rate and CO2- and O2-affinities of Posidonia Rubiscos follow an alternative path to that characteristic of terrestrial angiosperm Rubiscos.

Light Spectrum Variably Affects the Acclimatization of Grafted Watermelon Seedlings While Maintaining Fruit Quality

In many countries of Europe and Eastern Asia, watermelon production is mainly based on the use of grafted seedlings. Upon grafting, seedlings undergo a period of healing where artificial lighting is provided by light-emitting diodes in controlled chambers in order to accelerate and improve the healing process. The objective of our study was to test the effect of light quality on the final product (i.e., seedlings ready for transplanting) in the nursery, as well as to evaluate the possible implications on fruit quality after field cultivation. Narrow-band blue (B) and red (R) wavelengths, 64–36% R-B (36B), 76–24% R-B (24B), 88–12% R-B (12B), and 83–12% R-B plus 5% far-red (12B+FR) wavelengths were tested. 12B+FR enhanced the root dry weight, root architecture, and maximum photosynthetic rate, while RB combinations generally showed better root system development with increased blue portion. R light induced inferior root dry weight and quality indices (root/shoot and shoot–dry–weight/length ratios), lower gas exchange parameters, and chlorophyll content, but high shoot length and leaf area. B light led to inferior root architecture, lower stem diameter, leaf area, and maximum photosynthetic rate. Both R and B wavelengths showed decreased concentration of macronutrients and trace elements. After field cultivation, fruit quality (i.e., morphology and color), and valuable nutritive characteristics (i.e., phenolics, carotenoids, lycopene, antioxidants) maintained high quality irrespective of light treatments. Overall, 12B+FR performed well in almost all qualitative parameters including the morphology, the root development, and photosynthesis, while also maintaining high fruit quality.

Mitigating negative effects of long-term treated wastewater irrigation: Leaf gas exchange and water use efficiency response of avocado trees (Persea americana Mill.)

Declining performance of avocado orchards growing in a clayey soil irrigated with treated wastewater (TWW) for more than 5 years has been observed in Israel. Measures studied to mitigate this were freshwater (FW), blended TWW:FW in a 1:1 ratio (MIX), low-frequency TWW-irrigation (LFI), TWW irrigated tuff trenches (TUF) and TWW as the control treatment. This study reports on the response of avocado leaf gas exchange, intrinsic water use efficiency, leaf water potential and leaf hydraulic conductance (Kleaf) to the mitigation measures applied to a 'Hass' avocado orchard (Persea americana Mill.) previously irrigated with TWW for 7 years. Stomatal conductance (gs) of FW, MIX, TUF and LFI was greater than that for TWW on most measurement dates, which increased net leaf CO2 assimilation rate (Aleaf) and intercellular CO2 concentration (Ci). Increased gs reduced intrinsic water use efficiency [WUE, determined from either 13C discrimination (iWUE) or gas exchange (WUEi)] as compared to TWW. Although the WUE in TWW was higher than that in mitigation treatments on most measurement dates, the lower assimilation rates at leaf (Aleaf) and whole tree (Atree) levels observed in TWW indicate that TWW irrigation had negative effects on tree physiological performance. A strong negative relationship between WUEi (Aleaf/gs) and gs was found in all treatments, with highest WUEi and lowest gs in TWW. Leaf hydraulic conductance was also lowest for TWW, which may indicate that lower gas exchange was linked to lower water availability to the leaves. Overall, the increased gs, Aleaf, Atree and Kleaf in FW, MIX and TUF relative to TWW indicate that these mitigation measures are good candidates for improving orchard performance negatively affected by long-term irrigation with TWW in clayey soils. Comparing all treatments, FW was the most effective.

The distinct roles of water table depth and soil properties in controlling alternative woodland-grassland states in the Cerrado.

Open grassy vegetation and forests share riparian zones across the Neotropical savannas, characterizing alternative stable states. However, factors determining the occurrence and maintenance of each vegetation type are yet to be elucidated. To disentangle the role of environmental factors (soil properties and groundwater depth) constraining tree colonization of wet grasslands in the Cerrado, we assessed tree establishment during the early seedling and sapling stages and the influence of these factors on leaf gas exchange and leaf water potential of tree saplings. Three functionally distinct tree species were studied: (1) flood-tolerant species characteristic of gallery forests, (2) flood-intolerant species characteristic of seasonally dry savannas, and (3) generalist species found in both gallery forests and seasonally dry savannas. Savanna species was constrained by waterlogging, especially at the sapling stage, with restricted stomatal conductance and leaf water potential, resulting in low carbon assimilation, decreased plant size, and high mortality (above 80%). The gallery forest and the generalist species, however, were able to colonize the wet grasslands and survive, despite the low seedling emergence (below 30%) and sapling growth constrained by low gas exchange rates. Soil waterlogging is, therefore, an effective environmental filter that prevents savanna trees from expanding over wet grasslands. However, colonization by trees adapted to a shallow water table cannot be constrained by this or other soil properties, turning the wet grasslands dependent on natural disturbances to persist as an alternative state, sharing the waterlogged environments with the gallery forests in the Cerrado region.

NCED expression is related to increased ABA biosynthesis and stomatal closure under aluminum stress

Aluminum (Al)-induced decrease in leaf hydration has been associated with low gas exchange, especially stomatal conductance (gs). However, the mechanisms explaining these responses are unclear. Citrus limonia was exposed to 0 and 1480 μM Al in nutrient solution for 90 days to test whether the low gs and leaf hydration in plants exposed to Al is associated with increased 9-cis-epoxycarotenoid dioxygenase (NCED) gene expression and abscisic acid (ABA) biosynthesis. Relative leaf water content (RWC), water potential (Ψw) and gas exchange in the leaves, as well as leaf and root ClNCED3, ClNCED1 and ClNCED5 expression and accumulation of ABA and its metabolites (phaseic acid, dihydrophaseic acid, (+)-7′-hydroxy-ABA and ABA-β-d-glucosyl ester) were measured. Aluminum up-regulated ClNCED3 and induced ABA accumulation in the roots before impairments in leaf water status (low Ψw, RWC and gs) could be observed. Leaf ABA concentration increased from 7 to 90 days and this could be partially explained by the up-regulation of ClNCED3, ClNCED1 and ClNCED5 in this organ. Stomatal closure occurred concomitantly with the increase of ABA concentration, and this result provides further evidence of the role of ABA modulation of plant hydration under Al stress.

Vehicular emissions effect on the physiology and health status of five tree species in a Bogotá, Colombia urban forest

ABSTRACT. Introduction: Thanks to filtration by foliage, urban trees have a crucial role in air depuration. However, the exposure to pollutants could reduce their health and physiological performance, mainly because of low access to light and clogging of stomata by particulate matter. Objective: The accumulation of particulate matter on leaves (PMAL) and physiological traits of five urban tree species (Croton bogotanus Cuatrec., Eugenia myrtifolia Sims., Ficus soatensis Dugand, Schinus mole L., and Sambucus nigra L.) were quantified in sixty points in Bogotá, with the aims to (1) build a model explaining the PMAL based on traffic variables, (2) establishing the effect of vehicle pollution on physiological and phytosanitary variables, and (3) to evaluate the susceptibility of seedlings and trees to vehicle pollution. Methods: The physiological parameters: photochemical efficiency, stomatal conductance, chlorophyll content, leaf area, and specific leaf mass were measured and correlated with phytosanitary condition, PMAL and traffic variables: number of lanes, vehicular flow and tree-to-avenue distance. Additionally, tree physiological responses were measured in control, residential streets (RS), low traffic avenues (LTA), and high traffic avenues (HTA), and these last were compared with physiology of seedlings planted by three months in HTA. Results: PMAL was strongly associated with physiological responses. Ficus soatensis and C. bogotanus were the species with the maximum and the minimum PMAL. The exposure to traffic increased the photochemical efficiency and specific leaf mass, which could be related to the enrichment of nitrogen and atmospheric CO2. The stomatal conductance followed a bell pattern of low gas exchange in control sites, high values in RS and LTA, and decreasing again in HTA, which suggests an optimization in CO2 fixation at intermediate levels of pollution and susceptibility to stomatal clogging by extreme vehicle emissions. The chlorophyll a/b ratio, leaf area, and specific leaf mass were significantly related to the severity of leaf symptoms, and S. molle was the species with the healthiest leaves in HTA. Seedlings were more susceptible to pollution than trees, and fruits size and seedlings growth were affected by vehicular pollution. Conclusions: Ficus soatensis optimizes particle filtration and C. bogotanus is ideal for planting in HTA, although only as saplings. By contrast, the fast-growing E. myrtifolia and S. nigra seedlings should not be planted in HTA because of susceptibility of pigment contents, leaf area, and stomatal conductance to pollutants. Finally, because of its persistent high stomatal conductance and its low leaf symptoms, S. molle is the species with the best adaptation to vehicle pollution. A complete analysis of interactions among traffic, physiology, and health will help to improve the urban forestry planning.

Physiological, anatomical and ultrastructural effects of aluminum on Styrax camporum, a native Cerrado woody species.

Styrax camporum Pohl. (Styracaceae) is a woody species that grows on acidic soils from the Brazilian savanna with high aluminum (Al) saturation (m% > 50%), where it accumulates ~ 1500mg Al per kg dry leaves. Using nutrient solution, a previous study showed that 1480μM Al causes toxicity symptoms, which raises the question whether less than 1480μM Al could cause beneficial effects on this species. Here, we checked possible altered gas exchange rates, damage to organelles in root tips and the association between Al exposure and mitochondria occurrence in cells of root tips, once organic acids from Krebs cycle exuded by the roots of this species when exposed to Al have been recently evidenced. Five-month-old plants were grown in nutrient solution with 0, 740 and 1480μM Al for 90days. Plants exposed to 1480μM Al showed less developed root system, reduced plant height and low gas exchange rates in relation to those exposed to 0 and 740μM Al, confirming that 1480μM Al is toxic to S. camporum. However, plants exposed to 0 and 740μM Al had similar number of leaves, plant height, root biomass, root length, total plant biomass and gas exchange rates, indicating that no beneficial effects from 740μM Al could be noted on this species. In plants exposed to 0 and 740μM Al, mitochondria were noted at the root tip, while at 1480μM Al these organelles were not evident due to the conspicuous vacuolation of root cells. S. camporum shows limited tolerance to Al in nutrient solution. In addition, this species is not dependent on Al to grow and develop because the plants grew well under 0 and 740μM Al.

The analysis of dissolved inorganic carbon in liquid using a microfluidic conductivity sensor with membrane separation of CO2

Autonomous continuous analysis of oceanic dissolved inorganic carbon (DIC) concentration with depth is of great significance with regard to ocean acidification and climate change. However, miniaturisation of in situ analysis systems is hampered by the size, cost and power requirements of traditional optical instrumentation. Here, we report a low-cost microfluidic alternative based on CO2 separation and conductance measurements that could lead to integrated lab-on-chip systems for ocean float deployment, or for moored or autonomous surface vehicle applications. Conductimetric determination of concentration, in the seawater range of 1000–3000 µmol kg−1, has been achieved using a microfluidic thin-film electrode conductivity cell and a membrane-based gas exchange cell. Sample acidification released CO2 through the membrane, reacting in a NaOH carrier, later drawn through a sub-µL conductivity cell, for impedance versus time measurements. Precision values (relative standard deviations) were ~ 0.2% for peak height measurements at 2000 µmol kg−1. Comparable precision values of ~ 0.25% were obtained using a C4D electrophoresis headstage with similar measurement volume. The required total sample and reagent volumes were ~ 500 µL for the low volume planar membrane gas exchange cell. In contrast, previous conductivity-based DIC analysis systems required total volumes between 5000 and 10,000 µL. Long membrane tubes and macroscopic wire electrodes were avoided by incorporating a planar membrane (PDMS) in the gas exchange cell, and by sputter deposition of Ti/Au electrodes directly onto a thermoplastic (PMMA) manifold. Future performance improvements will address membrane chemical and mechanical stability, further volume reduction, and component integration into a single manifold.

Physiological Mechanisms of Foliage Recovery after Spring or Fall Crown Scorch in Young Longleaf Pine (Pinus palustris Mill.)

We hypothesized that physiological and morphological responses to prescribed fire support the post-scorch foliage recovery and growth of young longleaf pine. Two studies conducted in central Louisiana identified three means of foliage regrowth after fire that included an increase in the gas exchange rate of surviving foliage for 3 to 4 months after fire. Saplings also exhibited crown developmental responses to repeated fire that reduced the risk of future crown scorch. Starch reserves were a source of carbon for post-scorch foliage regrowth when fire was applied in the early growing season. However, the annual dynamics of starch accumulation and mobilization restricted its effectiveness for foliage regrowth when fire was applied late in the growing season. As such, post-scorch foliage regrowth became increasingly dependent on photosynthesis as the growing season progressed. Additionally, the loss of foliage by fire late in the growing season interrupted annual starch dynamics and created a starch void between the time of late growing season fire and mid-summer of the next year. The occurrence of drought during both studies revealed barriers to foliage reestablishment and normal stem growth among large saplings. In study 1, spring water deficit at the time of May fire was associated with high crown scorch and poor foliage and stem growth among large saplings. We attribute this lag in stem growth to three factors: little surviving foliage mass, low fascicle gas exchange rates, and poor post-scorch foliage recovery. In study 2, May fire during a short window of favorable burning conditions in the tenth month of a 20-month drought also reduced stem growth among large saplings but this growth loss was not due to poor post-scorch foliage recovery. Application of this information to prescribed fire guidelines will benefit young longleaf pine responses to fire and advance efforts to restore longleaf pine ecosystems.

Mycorrhizal inoculation on compost substrate affects nutritional balance, water uptake and photosynthetic efficiency in Cistus albidus plants submitted to water stress

The use of composted manure as alternative substrate can be suitable to produce ornamental potted plants. However, under water stress this substrate can result an additional stress for plants due to its physicochemical properties. In these conditions, mycorrhizae application can improve water and nutrients efficiency. The experiment was carried out in a growth chamber with a first phase (I) in which both inoculated and non-inoculated Cistus albidus L. plants at two substrates (commercial and mixtures of composted manure) were well irrigated and a second phase (II) in which the plants were submitted to water stress. Glomus iranicum (Blaszk., Kovacs & Balazs) var. tenuihypharum sp. nova was well established in cistus roots, but water stress hindered mycorrhizal proliferation in compost, which resulted in plants with smaller leaf and root biomass. The plants in compost had the highest Cl, K, Na, P and Zn contents in leaf; mycorrhizae reduced the Na and increased phosphorus, especially when the substrate was well-watered. Water stress decreased leaf water potential (Ψl), and mycorrhizae induced higher Ψl values in both substrates. Compost induced leaf osmotic adjustment, lower gas exchange and photochemical quenching parameters (Fv/Fm, Y(II)) values. Mycorrhizal plants had higher Y(II) and qP values than non-inoculated plants. Compost decreased relative chlorophyll content in both phases, but in inoculated plants these values increased under water stress. C. albidus plants growing in compost maintain a good nutritional balance and efficient osmotic regulation. Under water stress, plants suffer more stress than plants in commercial substrate, as reflected by the lipid peroxidation and Pn values.

Physiological activity and biomass production in crop canopy under a tropical environment in soybean cultivars with temperate and tropical origins

In order to explore the plant factors facilitating better adaptation of soybean to high temperatures, genotypic variability till the beginning of seed filling (R5) were examined with reference to biomass production, relative transpiration activity and relevant plant factors under a tropical environment. Twenty-nine (in 2014 and 2015) and 20 (in 2016) soybean cultivars of temperate (Japan and USA) and tropical (Indonesia-old, Indonesia-modern, and Others) origin were grown in Serang, Banten (2014 and 2015; Experiment 1) and in Bogor, West Java (2016; Experiment 2), Indonesia. In Experiment 1, aboveground biomass at R5 (TDWR5) of the temperate cultivars was one-third to one-fourth of that of the tropical cultivars. This was associated with less than half the amount of the cumulative intercepted radiation to R5 (CIRR5) due to their shorter growth duration and lower value of the mean fraction of canopy light interception till R5 (mean FVE-R5). In addition, the radiation use efficiency (RUE) at R5 of the temperate cultivars was also as low as 0.54gMJ−1, as compared to 0.87gMJ−1 in the tropical cultivars. The value of canopy temperature minus air temperature (CTd), as an indicator of relative transpiration activity, of temperate cultivars was markedly larger than that of the tropical cultivars, indicating lower transpiration activity in temperate cultivars, which was associated with the low RUE. In Experiment 2, greater activity of transpiration in tropical cultivars was attributed to their higher stomatal conductance (gs) and greater stomatal density (Nstoma) of upper leaves than that in those from the temperate regions. These results indicate that low biomass production in temperate cultivars occurs not only due to the cumulative intercepted radiation in the canopy but also due to low RUE and that the low RUE in temperate cultivars is associated with low gas exchange activity, in which leaf morphological traits are involved. Within temperate cultivars, US cultivars tended to perform better than the Japanese cultivars with respect to gas exchange activity.

Tortoise or hare: Will resprouting oaks or reseeding pines dominate following severe wildfire?

Abstract Post-fire shifts in species composition and growth are driven in part by alterations in resource availability. However, less is known about the extent to which differences in fire severity will affect leaf-level physiological responses in co-occurring species. Therefore, this study tested loblolly pine (Pinus taeda L.) saplings’ and resprouting oaks’ (Quercus stellata Wangenh. (post oak) and Q. marilandica Muenchh. (blackjack oak)) responses to various stresses following a catastrophic wildfire in 2011 that occurred in the Lost Pines region in Texas, USA. General plant responses (height, stem number, and plant density) and leaf-level stress indicators [gas exchange (photosynthesis (A), transpiration (E) and stomatal conductance (gs), pressure-volume parameters, and leaf biochemistry] were monitored along resource availability gradients (two burn severities and three soil types) in the summer of 2016. Nearly 5 years after the fire, there were 180% more pines in moderate severity transects than high severity transects. However, pines in high severity areas were similar in height to those growing in moderate severity areas. Pines consistently had low A, E, and gs rates when compared to co-occurring oaks. Pine osmotic potential at full turgor (ΠFT), turgor loss point (ΠTLP), and bulk modulus of elasticity (e) were 33, 30, and 58% greater, respectively, than those of oaks. Loblolly pine leaf-level gas exchange and pressure-volume results suggest this species adopts a drought-avoidance strategy for survival. Low gas exchange rates in pine saplings may reflect greater stomatal control, which could reduce cavitation risks, or may have arisen from reduced access to water resources by saplings’ shallow roots. Gas exchange and pressure-volume parameters of the oaks reflect greater drought tolerance than pine, with post oak being the more tolerant of the two oak species. Leaf-level gas exchange and pressure-volume measurements were coordinated, and results suggest that post oak utilized osmotic adjustment to maintain gas exchange in the more exposed, high severity areas. Additionally, differences in foliar nutrient and phenolic contents between oaks and pines may reflect differences in their leaf-level gas exchange capabilities. Results suggest loblolly pine regeneration may be slower in high burn-severity areas, and that differences in physiological strategies to cope with water stress among the three species may shift stand composition to oak dominance in parts of this region following wildfire.

Short-term physiological changes in roots and leaves of sugarcane varieties exposed to H2O2 in root medium

The aim of this study was to evaluate the differential sensitivity of sugarcane genotypes to H2O2 in root medium. As a hypothesis, the drought tolerant genotype would be able to minimize the oxidative damage and maintain the water transport from roots to shoots, reducing the negative effects on photosynthesis. The sugarcane genotypes IACSP94-2094 (drought tolerant) and IACSP94-2101 (drought sensitive) were grown in a growth chamber and exposed to three levels of H2O2 in nutrient solution: control; 3mmolL−1 and 80mmolL−1. Leaf gas exchange, photochemical activity, root hydraulic conductance (Lr) and antioxidant metabolism in both roots and leaves were evaluated after 15min of treatment with H2O2. Although, root hydraulic conductance, stomatal aperture, apparent electron transport rate and instantaneous carboxylation efficiency have been reduced by H2O2 in both genotypes, IACSP94-2094 presented higher values of those variables as compared to IACSP94-2101. There was a significant genotypic variation in relation to the physiological responses of sugarcane to increasing H2O2 in root tissues, being root changes associated with modifications in plant shoots. IACSP94-2094 presented a root antioxidant system more effective against H2O2 in root medium, regardless H2O2 concentration. Under low H2O2 concentration, water transport and leaf gas exchange of IACSP94-2094 were less affected as compared to IACSP94-2101. Under high H2O2 concentration, the lower sensitivity of IACSP94-2094 was associated with increases in superoxide dismutase activity in roots and leaves and increases in catalase activity in roots. In conclusion, we propose a general model of sugarcane reaction to H2O2, linking root and shoot physiological responses.

Fractal analysis of alveolarization in hyperoxia-induced rat models of bronchopulmonary dysplasia

Many morphometric approaches have been proposed for quantitative evaluation of alveolarization in experimental models of bronchopulmonary dysplasia (BPD), such as alveolar number, alveolar size and variability, mean linear intercept (Lm), surface-to-volume ratio, or radial alveolar count. Conversely, no papers are available about potentiality of fractal analysis in this matter. Thus, in the present study, we performed a comparative analysis between Lm and fractal parameters (fractal dimension (D) and lacunarity (λ)), in experimental hyperoxia-induced models of BPD. At birth the newborn rats were randomly distributed between the following experimental groups: a) rats raised in ambient air for 2 weeks; b) exposed to 60% oxygen for 2 weeks; c) raised in normoxia for 6 weeks; d) exposed to 60% hyperoxia for 2 weeks and then to room air for further 4 weeks. Normoxic 6-weeks rats showed a significant decrease of Lm and a significant increase of D and λ with respect to normoxic 2-weeks rats, indicative of alveolar development. Hyperoxia-exposed rats of 2 weeks did not show significant changes in Lm and D with respect to normoxic rats equal in age, although λ was significantly lower in hyperoxic group. Conversely, in the comparison between 6-week rats, the hyperoxia-exposed group showed higher value of Lm and lower values of D and λ, when compared to the normoxic group, confirming a lower alveolar gas exchange surface-to-volume ratio and an airspace morphology of lower complexity. The analysis of the ROC curves showed a comparable discriminatory power of Lm and D as binary classifiers of the airspace morphology (areas under the curves of 0.815 and 0.753, respectively). Moreover, the values exhibited by the parameters when different segmentation thresholds were applied suggested that fractal parameters are less sensitive (D and λ showed a coefficient of variation of 0.005 and 0.009, respectively) than Lm (exhibiting a coefficient of variation of 0.05) to the bias eventually introduced in the analysis by approximations or errors in tissue segmentation. In conclusion, the present study demonstrated the ability of fractal analysis (D and λ) to identify developmental and hyperoxia-induced changes in alveolarization with discriminatory power similar to Lm. The fractal approach, however, appears more fit to automatic image analysis, being less influenced by approximations in thresholding and image editing.

A low-cost alternative membrane system that promotes growth in nodal cultures of Brazilian ginseng [Pfaffia glomerata (Spreng.) Pedersen

In vitro propagated plants under conditions of low gas exchange generally show morphological and physiological anomalies that lead to high mortality rates during ex vitro acclimatization. The use of gas-permeable membranes increases natural ventilation in culture vessels, photosynthesis and growth rates. However, commercial membranes are expensive, which limits their application. In this study, low-cost, simple to manufacture, alternative membranes were developed to promote gas exchange in jars used for in vitro plant tissue culture. The membranes were developed using polytetrafluoroethylene film and two or three layers of microporous tape (Missner & Missner®), and were designed to increase the growth of nodal cultures of Pfaffia glomerata (Brazilian ginseng). Conditions that provided higher gas exchange led to an increase in plant growth and content of photosynthetic pigments compared to a closed system without a gas-permeable membrane. The alternative membranes showed similar results for water vapor loss rate and photosynthetic pigments when compared to a commercial membrane. The alternative membranes were also an efficient barrier against contamination and remained intact after being autoclaved multiple times. Among the membranes tested, the traits of the P. glomerata in vitro-derived plants were similar when propagated using the alternative membrane with three layers of microporous tape or the commercial membrane. However, the alternative membrane has a unit cost that is ten times lower than the commercial membrane.

Fossil evidence for low gas exchange capacities for Early Cretaceous angiosperm leaves

The photosynthetic gas exchange capacities of early angiosperms remain enigmatic. Nevertheless, many hypotheses about the causes of early angiosperm success and how angiosperms influenced Mesozoic ecosystem function hinge on understanding the maximum capacity for early angiosperm metabolism. We applied structure-functional analyses of leaf veins and stomatal pore geometry to determine the hydraulic and diffusive gas exchange capacities of Early Cretaceous fossil leaves. All of the late Aptian—early Albian angiosperms measured possessed low vein density and low maximal stomatal pore area, indicating low leaf gas exchange capacities in comparison to modern ecologically dominant angiosperms. Gas exchange capacities for Early Cretaceous angiosperms were equivalent or lower than ferns and gymnosperms. Fossil leaf taxa from Aptian to Paleocene sediments previously identified as putative stem-lineages to Austrobaileyales and Chloranthales had the same gas exchange capacities and possibly leaf water relations of their living relatives. Our results provide fossil evidence for the hypothesis that high leaf gas exchange capacity is a derived feature of later angiosperm evolution. In addition, the leaf gas exchange functions of austrobaileyoid and chloranthoid fossils support the hypothesis that comparative research on the biology of living basal angiosperm lineages reveals genuine signals of Early Cretaceous angiosperm ecophysiology.

How does moss photosynthesis relate to leaf and canopy structure? Trait relationships for 10 Hawaiian species of contrasting light habitats

Mosses are an understudied group of plants that can potentially confirm or expand principles of plant function described for tracheophytes, from which they diverge strongly in structure. We quantified 35 physiological and morphological traits from cell-, leaf- and canopy-level, for 10 ground-, trunk- and branch-dwelling Hawaiian species. We hypothesized that trait values would reflect the distinctive growth form and slow growth of mosses, but also that trait correlations would be analogous to those of tracheophytes. The moss species had low leaf mass per area and low gas exchange rate. Unlike for tracheophytes, light-saturated photosynthetic rate per mass (A(mass)) did not correlate with habitat irradiance. Other photosynthetic parameters and structural traits were aligned with microhabitat irradiance, driving an inter-correlation of traits including leaf area, cell size, cell wall thickness, and canopy density. In addition, we found a coordination of traits linked with structural allocation, including costa size, canopy height and A(mass). Across species, A(mass) and nitrogen concentration correlated negatively with canopy mass per area, analogous to linkages found for the 'leaf economic spectrum', with canopy mass per area replacing leaf mass per area. Despite divergence of mosses and tracheophytes in leaf size and function, analogous trait coordination has arisen during ecological differentiation.