External CO2 Concentration Research Articles

Effects of atmospheric CO2 on canopy uptake of gaseous ammonia by tomato (Lycopersicum esculentum Mill.) in polytunnel vegetable production systems

Plant-atmosphere NH3 exchange is normally present in plastic-shed vegetable production systems, very limited information is currently available on how NH3 absorption responds to CO2 concentration changes. Tomato plants at the fruit setting stage were randomly selected from a field and transferred to a closed circulation system. Using an isotope gas dilution procedure (1:50-fold dilution) to inject different volumes of 13CO2 and 15NH3, we maintained the CO2 concentration in the system at 200, 400 or 800 ppm for 1 h, while the NH3 concentration was maintained at 20 or 100 ppm. Using this system, we studied the effects of different CO2 concentration on NH3 absorption by tomato leaves during the planting period in autumn and winter. With an increased carbon dioxide (CO2) concentration, the ammonia (NH3) uptake of a tomato (Lycopersicum esculentum Mill.) canopy increased significantly (P < 0.05) and carbon (C) accumulation increased accordingly. Compared with a low NH3 environment, a high NH3 environment significantly increased the NH3 uptake of a plant canopy (P < 0.05), but under a C800 treatment it decreased significantly. Under two different NH3 environments, the NH4+ concentration and pH in tomato leaf apoplasts decreased significantly with an increase in the CO2 concentration (P < 0.05), and the NH3 compensation point (χNH3) gradually decreased (P < 0.05). In a low NH3 environment (N20), compared with the C400 treatment, NH3 absorption was reduced by 34.9% in the C800 treatment, whereas in a high NH3 environment (N100) it was reduced by 32.2%. A redundancy analysis (RDA) and path analysis showed that the influence of the CO2 concentration on canopy NH3 absorption was mainly achieved by changing the direct effect of the χNH3 [although the stomatal conductance (Gs) decreased with an increase in the CO2 concentration]. The response of a lower χNH3 to elevated CO2 will increase the absorption and utilization of NH3volatilised from the soil into the air by tomato leaves in a greenhouse. It was therefore shown that the NH3 absorption by a greenhouse tomato canopy was simultaneously affected by changes in the external NH3 and CO2 concentrations, and increased with an increase in C accumulation.

Lima Bean Growth, Leaf Stomatal and Nonstomatal Limitations to Photosynthesis, and 13C Discrimination in Response to Saline Irrigation

Soil salinization is a widespread problem severely impacting crop production. Understanding how salt stress affects growth-controlling photosynthetic performance is essential for improving crop salt tolerance and alleviating the salt impact. Lima bean (Phaseolus lunatus) is an important crop, but little information is available on its growth and leaf gas exchange in relation to a wide range of salinity. In this study, the responses of leaf gas exchange and whole plant growth of lima bean (cv. Fordhook 242) to six salinities with electrical conductivity (EC) of 2.9 (control), 5.7, 7.8, 10.0, 13.0, and 15.5 dS·m−1 in irrigation waters were assessed. Significant linear reduction by increasing salinity was observed on plant biomass, bean yield, and leaf net carbon assimilation rate (A). As EC increased from the control to 15.5 dS·m−1, plant biomass and A decreased by 87% and 69%, respectively, at the vegetative growth stage, and by 96% and 83%, respectively, at the pod growth stage, and bean yield decreased by 98%. Judged by the linear relations, the reduction in A accounted for a large portion of the growth reduction and bean yield loss. Salinity also had a significantly negative and linear effect on leaf stomatal conductance (gS). Leaf intercellular CO2 concentration (Ci) and leaf C13 isotope discrimination (Δ13) declined in parallel significantly with increasing salinity. The A-Ci curve analysis revealed that stomatal limitation [Lg (percent)] to A increased significantly and linearly, from 18% to 78% and from 22% to 87% at the vegetative and pod-filling stages, respectively, as EC increased from the control to the highest level. Thus, relatively nonstomatal or biochemical limitation [Lm (percent), Lm = 100 − Lg] to A responded negatively to increasing salinity. This result is coincident with the observed Δ13 salt-response trend. Furthermore, leaf carboxylation efficiency and CO2-saturated photosynthetic capacity [maximum A (Amax)] were unaffected by increasing salinity. Our results strongly indicate that the reduction in lima bean A by salt stress was mainly due to stomatal limitation and biochemical properties for photosynthesis might not be impaired. Because stomatal limitation reduces A exactly from lowering CO2 availability to leaves, increasing CO2 supply with an elevated CO2 concentration may raise A of the salt-stressed lima bean leaves and alleviate the salt impact. This is supported by our finding that the external CO2 concentration for 50% of Amax increased significantly and linearly with increasing salinity at the both growth stages. Leaf water use efficiency showed an increasing trend and no evident decline in leaf chlorophyll soil plant analysis development (SPAD) readings was observed as salinity increased.

Physiological aspects and yield in coffee progenies with large beans

Genetic coffee breeding is aimed at increasing yield associated with tolerance or resistance to biotic and abiotic factors, besides providing a better beverage quality and supplying the demand for bigger beans. The efficiency in photosynthetic activity can limit produce and diversify genotypes, mainly under adverse environmental conditions. Consequently, the importance of selection of Coffea arabica L. regarding these characteristics stands out. Therefore, the objective of this paper was to measure the physiological characterization and yield of Coffea arabica L. progenies with large beans “Big Coffee VL”. Twelve productive progenies were selected and classified according to fruit size (“small”, “medium” and “large”), which were: S14, S23, S34, S36, M4, M5, M14, M20, L10, L12, L17 and L31. Net photosynthetic rate (A), stomatal conductance (gs), transpiration rate (E), water use efficiency (WUE), internal carbon (Ci), intercellular CO2 concentration in the mesophyll were evaluated on the current external CO2 concentration (Ci/Ca), besides vapor pressure deficit (VPD), leaf temperature (Tleaf), indirect determination of the relative levels of chlorophylls a, b and total, in addition to bean yield in two crops. The Tocher grouping resulted in the formation of 4 groups, and progenies M4, L10 and S34 remained in isolated groups. Progeny L10 stood out for higher mean values of A, gs and Ci; the opposite behavior was observed in progeny S34. Progeny M4 is noteworthy as the one with the highest yield in the two years considered, in addition to presenting high photosynthetic rate and chlorophyll indexes. It is concluded that the progenies of “Big Coffee VL” show variability for physiological parameters and productivity. Progenies S14, M4 and L10 stood out, and S14 was more efficient in the use of water; M4 was the most productive and L10 stood out in terms of gas exchange. Key words: Chlorophyll; Coffea arabica L.; Gas exchange; Genetic breeding.

Cell size influences inorganic carbon acquisition in artificially selected phytoplankton.

Cell size influences the rate at which phytoplankton assimilate dissolved inorganic carbon (DIC), but it is unclear whether volume-specific carbon uptake should be greater in smaller or larger cells. On the one hand, Fick's Law predicts smaller cells to have a superior diffusive CO2 supply. On the other, larger cells may have greater scope to invest metabolic energy to upregulate active transport per unit area through CO2 -concentrating mechanisms (CCMs). Previous studies have focused on among-species comparisons, which complicates disentangling the role of cell size from other covarying traits. In this study, we investigated the DIC assimilation of the green alga Dunaliella tertiolecta after using artificial selection to evolve a 9.3-fold difference in cell volume. We compared CO2 affinity, external carbonic anhydrase (CAext ), isotopic signatures (δ13 C) and growth among size-selected lineages. Evolving cells to larger sizes led to an upregulation of CCMs that improved the DIC uptake of this species, with higher CO2 affinity, higher CAext and higher δ13 C. Larger cells also achieved faster growth and higher maximum biovolume densities. We showed that evolutionary shifts in cell size can alter the efficiency of DIC uptake systems to influence the fitness of a phytoplankton species.

Numerical simulation of the CO2 diffusion effect on low turbulent mixed convection in a ventilated room heated by the bottom

A double-diffusive mixed convection within low turbulent regime in a ventilated cavities filled with an air CO2 mixture and heated from below has been numerically investigated. The lower wall was sustained at a uniform temperature and CO2 concentration. The vertical and upper walls were kept at external temperature and CO2 concentration. To analyze the behavior of flow, the ventilation effectiveness for temperature distribution and removal of CO2 contaminant, four configurations were dealt. These differ from each other by the location of the mixture inlet and outlet gaps. Likewise, three CO2 concentrations were considered (103, 2?103, and 3?103 ppm) to investigate the influence of the CO2 diffusion on the ventilation effectiveness. The numerical simulations were performed by considering closed Reynolds averaged-Navier-Stokes equations using the Reynolds-normalization group k-? model. The governing equations? set was then solved using the finite volume method, in which the pressure-velocity coupling was handled using the SIMPLEC algorithm. Validation of the numerical model was achieved by comparing our results with available experimental data. The obtained results indicate that the CO2 diffusion effect on the air movement and the ventilation effectiveness for temperature distribution can be neglected in the present study. However, the CO2 diffusion remains a key parameter in terms of indoor air quality index. Also, it was found that one of the studied configurations provides a better ventilation effectiveness to remove heat and CO2 contaminant, and insures a homogeneous temperature and CO2 concentration in the occupied zone. The three other configurations maintain an acceptable level of heat and can be used in temperate climate to ensure good indoor air quality.

LCI1, a Chlamydomonas reinhardtii plasma membrane protein, functions in active CO2 uptake under low CO2.

In response to high CO2 environmental variability, green algae, such as Chlamydomonas reinhardtii, have evolved multiple physiological states dictated by external CO2 concentration. Genetic and physiological studies demonstrated that at least three CO2 physiological states, a high CO2 (0.5-5% CO2 ), a low CO2 (0.03-0.4% CO2 ) and a very low CO2 (< 0.02% CO2 ) state, exist in Chlamydomonas. To acclimate in the low and very low CO2 states, Chlamydomonas induces a sophisticated strategy known as a CO2 -concentrating mechanism (CCM) that enables proliferation and survival in these unfavorable CO2 environments. Active uptake of Ci from the environment is a fundamental aspect in the Chlamydomonas CCM, and consists of CO2 and HCO3- uptake systems that play distinct roles in low and very low CO2 acclimation states. LCI1, a putative plasma membrane Ci transporter, has been linked through conditional overexpression to active Ci uptake. However, both the role of LCI1 in various CO2 acclimation states and the species of Ci , HCO3- or CO2 , that LCI1 transports remain obscure. Here we report the impact of an LCI1 loss-of-function mutant on growth and photosynthesis in different genetic backgrounds at multiple pH values. These studies show that LCI1 appears to be associated with active CO2 uptake in low CO2 , especially above air-level CO2 , and that any LCI1 role in very low CO2 is minimal.

Productive and physiological performance of lettuce cultivars under hydroponic cultivation in the semi-arid region of the Northeast

Lettuce is the most-produced leafy vegetable in Brazil; however, to achieve satisfactory production in the different regions, it is necessary to choose the correct cultivar. The aim of this work was to evaluate the productive and physiological performance of lettuce cultivars in a hydroponic system located in Caucaia, in the state of Ceará. A completely randomised design was used, with four cultivars (Isabela, Vanda, Elba and Summer Crisp) and four replications. The following were evaluated: plant height and diameter (PH and PD), total fresh and dry weight (TFW and TDW), commercial fresh weight (CFW), internal CO2 concentration (Ci), stomatal conductance (gs), photosynthesis (A), ratio between internal and external CO2 concentration (Ci/Ca), and transpiration (E). Differences were seen between cultivars in the production and physiological characteristics, except for Ci and Ci/Ca. The ‘Elba’ and ‘Summer Crisp’ cultivars were the first to show signs of bolting (32 and 36 days) and greater height, 38.7 and 31.8 cm respectively. The ‘Isabela’ and ‘Vanda’ cultivars obtained the greatest values for CFW (43.5 and 41.13 g) and TFW (49.38 and 46.46 g). In relation to physiological performance, the ‘Isabela’ and ‘Summer Crisp’ cultivars presented the most photosynthesis. The ‘Isabela’ cultivar had the best productive and physiological performance, in addition to being the only cultivar that presented no signs of bolting, and is therefore strongly suggested for hydroponic production under the conditions of this study.

Ordovician cyanobacterial calcification: A marine fossil proxy for atmospheric CO2

Ordovician atmospheric CO2 level was an important influence on climate and life. However, modelled estimates of Ordovician CO2 differ widely and, in contrast to much of the subsequent Phanerozoic, they lack fossil proxy constraints. In vivo cyanobacterial sheath calcification, promoted by carbon dioxide concentrating mechanisms (CCMs), creates distinctive microfossils. These provide a direct ecophysiological link to ambient concentrations of CO2 and, to a lesser extent, O2. Cyanobacteria do not calcify at high CO2 concentrations. Experiments show that CCMs can be induced in present-day cyanobacteria at CO2 levels below ∼10 times present atmospheric level (PAL) and that this promotes sheath calcification. We compiled a global database of cyanobacterial calcification in marine environments throughout the Ordovician (485-443 Myr ago) and compared it with modelled estimates of atmospheric CO2 and O2. These data show that many genera of marine calcified cyanobacteria reappeared from Cambrian Series 2 or first appeared globally during the late middle to late Upper Ordovician (late Darriwilian to late Katian) in carbonate platform facies, resulting in a previously unrecognized ten-fold increase in global diversity. Such a large increase in calcification suggests widespread induction of CCM expression in cyanobacteria, consistent with sustained decline in external CO2 concentrations below ∼10× PAL, together with increase in dissolved O2 level, during the late Darriwilian, Sandbian and Katian stages, ∼460-445 Myr ago. These cyanobacterial calcification fossil proxy data provide a first order constraint on modelled estimates of atmospheric CO2 for the Ordovician. Estimated CO2 outputs from COPSE and recent GEOCARB-based models are broadly consistent with this cyanobacterial calcification proxy for the Ordovician. In view of the long history of cyanobacteria, the calcified cyanobacterial proxy offers potential to assist interpretation of CO2 deeper into geological time.

Variation in Responses of Photosynthesis and Apparent Rubisco Kinetics to Temperature in Three Soybean Cultivars.

Recent in vivo assays of the responses of Rubisco to temperature in C3 plants have revealed substantial diversity. Three cultivars of soybean (Glycine max L. Merr.), Holt, Fiskeby V, and Spencer, were grown in indoor chambers at 15, 20, and 25 °C. Leaf photosynthesis was measured over the range of 15 to 30 °C, deliberately avoiding higher temperatures which may cause deactivation of Rubisco, in order to test for differences in temperature responses of photosynthesis, and to investigate in vivo Rubisco kinetic characteristics responsible for any differences observed. The three cultivars differed in the optimum temperature for photosynthesis (from 15 to 30 °C) at 400 μmol mol−1 external CO2 concentration when grown at 15 °C, and in the shapes of the response curves when grown at 25 °C. The apparent activation energy of the maximum carboxylation rate of Rubisco differed substantially between cultivars at all growth temperatures, as well as changing with growth temperature in two of the cultivars. The activation energy ranged from 58 to 84 kJ mol−1, compared with the value of 64 kJ mol−1 used in many photosynthesis models. Much less variation in temperature responses occurred in photosynthesis measured at nearly saturating CO2 levels, suggesting more diversity in Rubisco than in electron transport thermal properties among these soybean cultivars.

Morphophysiological and Biochemical Responses of Lippia grata Schauer (Verbenaceae) to Water Deficit

In the present study, we investigated the morphophysiological and biochemical responses of the species Lippia grata Schauer to water deficit. Plants from cuttings were submitted to two water regimes, irrigation (control) and suspended irrigation (stress) for 15 days and were then rehydrated for 10 days. During water regimes, we performed physiological (gas exchange, growth parameters, and biochemical) and anatomical analyses. The water deficit negatively affected growth of the aerial part of the plant with reduction of approximately 72%. On the contrary, root system growth was stimulated by water deficit (increase of 205%). The drought caused a reduction in the physiological parameters (gs, E, and A), while leaf temperature and internal and external CO2 concentration ratio (Ci/Ca) increased. Plants subjected to drought had higher intrinsic efficiency of water use on the 10th day of deficit (A/gs). The levels of total chlorophyll, carotenoids, and soluble carbohydrates increased on the 10th and 15th days of water suspension. The levels of H2O2, proteins, and MDA were high in plants on the 15th day of water deficit. The levels of H2O2 in the control plants increased on the 20th and 25th day of rehydration, along with the activation of some enzymes of the antioxidative system SOD, CAT and APX. Plants under water deficit increased SOD activity on the 10th day and CAT on the 10th and 15th day under stress. Plants submitted to water deficit showed reduction of mesophilic thickness, smaller epidermal cells, reduction of intercellular spaces, more vascular bundles, greater lignification of xylem cells, morphological modification of cortical cells, and have more glandular trichomes in the abaxial face compared to plants always irrigated. During rehydration, the plants submitted to the water deficit recovered in all variables analyzed and have a higher density of glandular and the tector trichomes in both epidermises, adaxial and abaxial. We conclude that the rapid recovery of the parameters evaluated for Lippia grata are related to the absence of irreversible damage in the cellular structures, due to the efficiency of the antioxidative system, and metabolic processes involved with the dissipation of the excess energy because of the imposed water stress. In addition, other important morphophysiological strategies such as increased root growth, increased vascular bundles and density of trichomes improved soil water absorption and maintained the cellular water content in Lippia grata plants submitted to drought.

MORPHOPHYSIOLOGICAL AND NUTRITIONAL BEHAVIOR OF Hymenaea stigonocarpa Mart. ex Hayne (FABACEAE) SEEDLINGS SUBMITTED TO LIMING

ABSTRACT Liming is beneficial for plants as it promotes pH elevation, neutralization of toxic aluminum, increase in calcium (Ca²+) and magnesium (Mg²+) supply, and provides greater root systems. However, it is known that different species, mainly those native to the Cerrado, respond in different ways to this technique. Given the above, the objective of this study was to determine how Hymenaea stigonocarpa (“Jatobá-do-Cerrado”) seedlings respond to liming in Dystrophic Red Latosol. The plants were cultivated in four-liter pots, submitted to different base saturation (natural soil, 30, 45, 60 and 75% V) and maintained in a greenhouse. Biometrics, biomass, nutritional content and physiological parameters were evaluated. A difference in Ca²+ and Mg²+ contents between leaves and stems was observed, leading to significant reductions in stomatal conductance, transpiration, internal CO2 concentration and internal and external CO2 concentration ratios, resulting in a reduction of the investment in growth and biomass. Given these results, there is no need for liming in the production of H. stigonocarpa seedlings in a Dystrophic Red Latosol.

Growth and gas exchanges of red pitaya under different shading conditions

Plants with yellow cladodes are commonly present in commercial red pitaya orchards, in Ceara, mainly during the warmer seasons of the year. Therefore, this study aimed to evaluate the effect of shading on the growth and gas exchanges of red pitaya. We tested five shading levels on stock plants (full sunlight, 35, 50; 65 and 80% shading) via randomized block design (RBD), with five replications and two plants per plot. After 180 days, the following characteristics were evaluated: sum of the length of the axillary shoots, number of axillary shoots, diameter, thickness of secondary shoots, photosynthetic rate, stomatal conductance of water vapor, transpiration, internal carbon dioxide concentration, ratio of internal to external CO2 concentration, instantaneous and intrinsic water use efficiency, and instantaneous carboxylation efficiency. The plants presents large and thin cladodes, apparently blanching under 80% shading; therefore, we concluded that cultivation in full sunlight caused a negative effect on gas exchanges and growth of red pitaya.. The use of 35% shading at 180 days increased the photosynthetic rate, water use efficiency and carboxylation, with increase vegetative growth.

RESIDUES OF FORAGE SPECIES AFFECT PHOTOSYNTHETIC CHARACTERISTICS OF THE PEQUIZEIRO

ABSTRACT Some forages release allelopathic substances into the environment, and may prevent consortium with arboreal species in pastures. The objective of this work was to evaluate photosynthetic characteristics of pequizeiro plants (hereafter pequi) influenced by concentrations of residues of the forage species Urocholoa decumbens, Melinis minutiflora and Paspalum notatum. The treatments consisted of pequi cultivation under aerial residues of the three forage species mixed to the substrate in four concentrations (1, 2, 3 and 4% mass/mass), plus an additional treatment (comparative control) with pequi cultivated on the substrate without waste. The following parameters were evaluated: photosynthetic rate, stomatal conductance, transpiration rate, relationship between internal and external CO2 concentration (Ci/Ca), maximum quantum yield, effective quantum yield of FS II, electron transport rate, nonchemical quenching and chlorophyll index, concerning the content of chlorophyll a, b and total in pequi plants at 50 and 100 days after transplanting (DAT), and the relative production of dry matter at 100 DAT. At 50 DAT, the following photosynthetic variables were affected in pequi plants: A, gs, chlorophyll a, chlorophyll b and total chlorophyll when cultivated in the presence of forage residues. At 100 DAT, the following photosynthetic variables were affected in pequi plants: A, Fv/Fm, ETR, NPQ, chlorophyll a, chlorophyll b and total chlorophyll, when cultivated in the presence of forage residues. Pequi plants had reduced relative dry matter yield when grown in the presence of U. decumbens. This variable was also affected when pequi was grown in increasing concentrations of residues of the species U. decumbens, M. minutiflora and P. notatum.

Effects of supplement with sanitary landfill leachate in gas exchange of sunflower (Helianthus annuus L.) seedlings under drought stress.

Sanitary landfill leachate is one of the major problems arising from disposal of urban waste. Sanitary landfill leachate may, however, have use in agriculture. This study, therefore, aimed to analyze initial plant growth and gas exchange in sunflower seedlings supplemented with sanitary landfill leachate and subjected to drought stress through variables of root fresh mass (RFM), shoot fresh mass (SFM), total fresh mass (TFM), relative chlorophyll content (CL), stomatal conductance (g s ), transpiration rate (E), net photosynthetic rate (A), ratio of internal to external CO2 concentration (Ci/Ca),water use efficiency (EUA), instantaneous carboxylation efficiency (A/Ci), and electron transport rate (ETR). The experimental design was a completely randomized 2 (irrigated and non-irrigated)×4 (sand, sand + 100kg Nha-1 organic fertilizer, sand + 100kg Nha-1 sanitary landfill leachate, and sand + 150kg Nha-1 sanitary landfill leachate) factorial with five replicates. Under drought stress conditions, leachate treatment supplemented with 100kg Nha-1 exhibited higher plant fresh weights than those of the treatment containing 150kg Nha-1. Increases in fresh mass in plant treatments supplemented with 100 and 150kgN ha-1 sanitary landfill leachate were related to higher photosynthetic rates.

The role of external carbonic anhydrase in photosynthesis during growth of the marine diatom Chaetoceros muelleri.

Carbon dioxide concentrating mechanisms (CCMs) act to improve the supply of CO2 at the active site of ribulose-1,5-bisphosphate carboxylase/oxygenase. There is substantial evidence that in some microalgal species CCMs involve an external carbonic anhydrase (CAext ) and that CAext activity is induced by low CO2 concentrations in the growth medium. However, much of this work has been conducted on cells adapted to air-equilibrium concentrations of CO2 , rather than to changing CO2 conditions caused by growing microalgal populations. We investigated the role of CAext in inorganic carbon (Ci ) acquisition and photosynthesis at three sampling points during the growth cycle of the cosmopolitan marine diatom Chaetoceros muelleri. We observed that CAext activity increased with decreasing Ci , particularly CO2 , concentration, supporting the idea that CAext is modulated by external CO2 concentration. Additionally, we found that the contribution of CAext activity to carbon acquisition for photosynthesis varies over time, increasing between the first and second sampling points before decreasing at the last sampling point, where external pH was high. Lastly, decreases in maximum quantum yield of photosystem II (Fv /Fm ), chlorophyll, maximum relative electron transport rate, light harvesting efficiency (α) and maximum rates of Ci - saturated photosynthesis (Vmax ) were observed over time. Despite this decrease in photosynthetic capacity an up-regulation of CCM activity, indicated by a decreasing half-saturation constant for CO2 (K0.5 CO2 ), occurred over time. The flexibility of the CCM during the course of growth in C.muelleri may contribute to the reported dominance and persistence of this species in phytoplankton blooms.

A new meta-model to calculate carbonation front depth within concrete structures

Carbonation processes cannot be ignored as regards durability and service-life of new concrete structures, and their correct understanding and quantification are essential for maintenance and repair works on existing structures. This paper initially presents a new meta-model developed to calculate carbonation front depth based on the analytic solution of Fick’s first law. The only input data required by this non numerical model are: (i) material variables (concrete mix design, maximum nominal aggregate size, cement type, and chemical composition of cement type CEM I and cement density); (ii) technological parameters (initial curing period (tc)); (iii) environmental parameters (ambient temperature (T), relative external humidity (RH) and CO2 concentration in the air ([CO2]ext)). Consequently, this model is fully suitable for the prediction of carbonation depth in the case of new reinforced concrete structures, for which these required parameters are well-known. The meta-model is validated using data from the literature on short and long-term natural carbonation exposure conditions. Most of the experimental data concern CEM I, CEM II, CEM III cement types, and CEM I additives (fly ash (FA)) with various water to cement (W/C) ratios and tc. The meta-model is also compared with two already available models: Papadakis’ model and Yang’s model. The three model predictions are compared with the corresponding values found in the literature. The results confirm that the prediction of the new meta-model proposed here for estimation of carbonation depth is the most accurate in every case.

The role of the intra- and extracellular protons in the photosynthetic response induced by the variation potential in pea seedlings

Local burning induces generation and propagation of variation potential (VP) in higher plants. VP induces transient inactivation of photosynthesis, which is possibly connected with proton signal in plant cell. Analysis of the role of changes in intracellular and extracellular pH in the VP-induced photosynthetic response in pea seedlings was the aim of this work. It was shown that local burning induced VP propagation, which was accompanied with a decrease of intracellular pH and increase of extracellular pH. VP induced photosynthesis inactivation that included an increase in the nonphotochemical fluorescence quenching and a decrease in the CO2 assimilation rate. Analysis of photosynthetic responses under control and low external CO2 concentration and changes in pH showed that there were two components in the responses. The first component appeared as a fast decrease of the CO2 assimilation and increase of nonphotochemical quenching. It depended on the activity of the dark stage of photosynthesis and was connected with apoplast alkalization. The second component was presented as a slow increase of nonphotochemical quenching. It weakly depended on a dark stage and was connected with a decrease of intracellular pH.

In vitro CO2 enrichment of CAM orchid plantlets

SummaryIncreased growth of an in vitro-propagated CAM orchid hybrid Mokara ‘White’ was obtained using a novel method of CO2 enrichment in an optimized photoautotrophic open system compared with the conventional closed system of culture. The optimization process for the open system involved the manipulation of external CO2 concentrations (0.03%, 1% and 10%), sucrose requirements, light intensities (80 and 200 µmol m–2 s–1) and the venting of headspace ethylene from the culture vessels. The physiological basis for increased growth in these CAM orchid plantlets after three months was attributed to the direct effects of elevated CO2 resulting in higher CAM activity for the plantlets and to the elevated CO2 present in the system which might interact with the ethylene present thereby reducing the inhibition of growth of plantlets due to ethylene.

Global vegetation gross primary production estimation using satellite-derived light-use efficiency and canopy conductance

Climate and physiological controls of vegetation gross primary production (GPP) vary in space and time. In many ecosystems, GPP is primary limited by absorbed photosynthetically-active radiation; in others by canopy conductance. These controls further vary in importance over daily to seasonal time scales. We propose a simple but effective conceptual model that estimates GPP as the lesser of a conductance-limited (Fc) and radiation-limited (Fr) assimilation rate. Fc is estimated from canopy conductance while Fr is estimated using a light use efficiency model. Both can be related to vegetation properties observed by optical remote sensing. The model has only two fitting parameters: maximum light use efficiency, and the minimum achieved ratio of internal to external CO2 concentration. The two parameters were estimated using data from 16 eddy covariance flux towers for six major biomes including both energy- and water-limited ecosystems. Evaluation of model estimates with flux tower-derived GPP compared favourably to that of more complex models, for fluxes averaged; per day (r2=0.72, root mean square error, RMSE=2.48μmolCm2s−1, relative percentage error, RPE=−11%), over 8-day periods (r2=0.78 RMSE=2.09μmolCm2s−1,RPE=−10%), over months (r2=0.79, RMSE=1.93μmolCm2s−1, RPE=−9%) and over years (r2=0.54, RMSE=1.62μmolCm2s−1, RPE=−9%). Using the model we estimated global GPP of 107PgCy−1 for 2000–2011. This value is within the range reported by other GPP models and the spatial and inter-annual patterns compared favourably. The main advantages of the proposed model are its simplicity, avoiding the use of uncertain biome- or land-cover class mapping, and inclusion of explicit coupling between GPP and plant transpiration.

Simulating the effects of light intensity and carbonate system composition on particulate organic and inorganic carbon production in Emiliania huxleyi.

Coccolithophores play an important role in the marine carbon cycle. Variations in light intensity and external carbonate system composition alter intracellular carbon fluxes and therewith the production rates of particulate organic and inorganic carbon. Aiming to find a mechanistic explanation for the interrelation between dissolved inorganic carbon fluxes and particulate carbon production rates, we develop a numerical cell model for Emiliania huxleyi, one of the most abundant coccolithophore species. The model consists of four cellular compartments, for each of which the carbonate system is resolved dynamically. The compartments are connected to each other and to the external medium via substrate fluxes across the compartment-confining membranes. By means of the model we are able to explain several pattern observed in particulate organic and inorganic carbon production rates for different strains and under different acclimation conditions. Particulate organic and inorganic carbon production rates for instance decrease at very low external CO2 concentrations. Our model suggests that this effect is caused mainly by reduced HCO3(-) uptake rates, not by CO2 limitation. The often observed decrease in particulate inorganic carbon production rates under Ocean Acidification is explained by a downregulation of cellular HCO3(-) uptake.