Photosynthetic Carbon Dioxide Uptake Research Articles

From grasses to succulents - development and function of distinct stomatal subsidiary cells.

Stomata are breathing pores on leaves that balance photosynthetic carbon dioxide uptake and water vapor loss. Stomatal morphology and complexity are rather diverse when considering stomatal subsidiary cells (SCs). Subsidiary cells are adjacent to the central guard cells (GCs) and are morphologically distinct from other epidermal cells. Yet, how various SCs develop and whether and how they support stomatal gas exchange physiology outside of the grass family is largely unknown. Here, we discuss the development, ontogeny, and putative function of paracytic vs anisocytic SCs, which can be found in grasses and Crassulaceae succulents, respectively. First, we highlight recent advances in understanding how grasses form stomatal SCs. We then summarize novel insights into stomatal development in SC-less Arabidopsis to speculate on how this stomatal program might be rewired to enable anisocytic SC formation. Finally, we discuss the functional relevance of paracytic SCs in grasses and the putative roles of anisocytic SCs in succulents.

Physiological and Transcriptomic Analyses Revealed the Implications of Abscisic Acid in Mediating the Rate-Limiting Step for Photosynthetic Carbon Dioxide Utilisation in Response to Vapour Pressure Deficit in Solanum Lycopersicum (Tomato).

The atmospheric vapour pressure deficit (VPD) has been demonstrated to be a significant environmental factor inducing plant water stress and affecting plant photosynthetic productivity. Despite this, the rate-limiting step for photosynthesis under varying VPD is still unclear. In the present study, tomato plants were cultivated under two contrasting VPD levels: high VPD (3–5 kPa) and low VPD (0.5–1.5 kPa). The effect of long-term acclimation on the short-term rapid VPD response was examined across VPD ranging from 0.5 to 4.5 kPa. Quantitative photosynthetic limitation analysis across the VPD range was performed by combining gas exchange and chlorophyll fluorescence. The potential role of abscisic acid (ABA) in mediating photosynthetic carbon dioxide (CO2) uptake across a series of VPD was evaluated by physiological and transcriptomic analyses. The rate-limiting step for photosynthetic CO2 utilisation varied with VPD elevation in tomato plants. Under low VPD conditions, stomatal and mesophyll conductance was sufficiently high for CO2 transport. With VPD elevation, plant water stress was gradually pronounced and triggered rapid ABA biosynthesis. The contribution of stomatal and mesophyll limitation to photosynthesis gradually increased with an increase in the VPD. Consequently, the low CO2 availability inside chloroplasts substantially constrained photosynthesis under high VPD conditions. The foliar ABA content was negatively correlated with stomatal and mesophyll conductance for CO2 diffusion. Transcriptomic and physiological analyses revealed that ABA was potentially involved in mediating water transport and photosynthetic CO2 uptake in response to VPD variation. The present study provided new insights into the underlying mechanism of photosynthetic depression under high VPD stress.

Snow melt stimulates ecosystem respiration in Arctic ecosystems.

Cold seasons in Arctic ecosystems are increasingly important to the annual carbon balance of these vulnerable ecosystems. Arctic winters are largely harsh and inaccessible leading historic data gaps during that time. Until recently, cold seasons have been assumed to have negligible impacts on the annual carbon balance but as data coverage increases and the Arctic warms, the cold season has been shown to account for over half of annual methane (CH4 ) emissions and can offset summer photosynthetic carbon dioxide (CO2 ) uptake. Freeze-thaw cycle dynamics play a critical role in controlling cold season CO2 and CH4 loss, but the relationship has not been extensively studied. Here, we analyze freeze-thaw processes through in situ CO2 and CH4 fluxes in conjunction with soil cores for physical structure and porewater samples for redox biogeochemistry. We find a movement of water toward freezing fronts in soil cores, leaving air spaces in soils, which allows for rapid infiltration of oxygen-rich snow melt in spring as shown by oxidized iron in porewater. The snow melt period coincides with rising ecosystem respiration and can offset up to 41% of the summer CO2 uptake. Our study highlights this important seasonal process and shows spring greenhouse gas emissions are largely due to production from respiration instead of only bursts of stored gases. Further warming is projected to result in increases of snowpack and deeper thaws, which could increase this ecosystem respiration dominate snow melt period causing larger greenhouse gas losses during spring.

Impact Assessment of Ozone Absorbed through Stomata on Photosynthetic Carbon Dioxide Uptake by Japanese Deciduous Forest Trees: Implications for Ozone Mitigation Policies

Photosynthesis by trees is expected to contribute to preventing climate change including global warming. However, the current levels of tropospheric ozone (O3) reduce the uptake of photosynthetic carbon dioxide (CO2) by forest trees in Japan, which is a concern. Furthermore, it is unknown how much O3 should be reduced to prevent plants’ O3-induced damage. The objective of the present study was to assess the negative effects of the current levels of O3 absorbed via stomata and the impact of its mitigation on the CO2 uptake by trees in Japanese forests. Impact assessment, targeted in 2011–2015, was performed for four deciduous broad-leaved trees: Fagus crenata, Quercus serrata, Q. mongolica var. crispula, and Betula platyphylla var. japonica. The assessment was based on species-specific cumulative stomatal O3 uptake (COU) and species-specific responses of annual photosynthetic CO2 uptake to COU. Annual COU differed between the four trees; the average COU of F. crenata, Q. serrata, Q. mongolica var. crispula, and B. platyphylla var. japonica across Japan was 41.7, 26.5, 33.0, and 29.1 mmol m−2, respectively, and the reductions in CO2 uptake by the four trees were 14.0%, 10.6%, 8.6%, and 15.4%, respectively. Further analysis revealed that reducing the atmospheric O3 concentration by approximately 28%, 20%, 17%, and 49% decreased the O3-induced reductions in photosynthetic CO2 uptake to 5% in F. crenata, Q. serrata, Q. mongolica var. crispula, and B. platyphylla var. japonica, respectively. In the near future, implementing mitigation measures for the O3 damage in plants is expected to enhance the photosynthetic capacity of Japanese forest tree species.

The Receptor-like Pseudokinase GHR1 Is Required for Stomatal Closure.

Guard cells control the aperture of stomatal pores to balance photosynthetic carbon dioxide uptake with evaporative water loss. Stomatal closure is triggered by several stimuli that initiate complex signaling networks to govern the activity of ion channels. Activation of SLOW ANION CHANNEL1 (SLAC1) is central to the process of stomatal closure and requires the leucine-rich repeat receptor-like kinase (LRR-RLK) GUARD CELL HYDROGEN PEROXIDE-RESISTANT1 (GHR1), among other signaling components. Here, based on functional analysis of nine Arabidopsis thaliana ghr1 mutant alleles identified in two independent forward-genetic ozone-sensitivity screens, we found that GHR1 is required for stomatal responses to apoplastic reactive oxygen species, abscisic acid, high CO2 concentrations, and diurnal light/dark transitions. Furthermore, we show that the amino acid residues of GHR1 involved in ATP binding are not required for stomatal closure in Arabidopsis or the activation of SLAC1 anion currents in Xenopus laevis oocytes and present supporting in silico and in vitro evidence suggesting that GHR1 is an inactive pseudokinase. Biochemical analyses suggested that GHR1-mediated activation of SLAC1 occurs via interacting proteins and that CALCIUM-DEPENDENT PROTEIN KINASE3 interacts with GHR1. We propose that GHR1 acts in stomatal closure as a scaffolding component.

Reactive Oxygen Species in the Regulation of Stomatal Movements.

Guard cells form stomatal pores that optimize photosynthetic carbon dioxide uptake with minimal water loss. Stomatal movements are controlled by complex signaling networks that respond to environmental and endogenous signals. Regulation of stomatal aperture requires coordinated activity of reactive oxygen species (ROS)-generating enzymes, signaling proteins, and downstream executors such as ion pumps, transporters, and plasma membrane channels that control guard cell turgor pressure. Accumulation of ROS in the apoplast and chloroplasts is among the earliest hallmarks of stomatal closure. Subsequent increase in cytoplasmic Ca(2+) concentration governs the activity of multiple kinases that regulate the activity of ROS-producing enzymes and ion channels. In parallel, ROS directly regulate the activity of multiple proteins via oxidative posttranslational modifications to fine-tune guard cell signaling. In this review, we summarize recent advances in the role of ROS in stomatal closure and discuss the importance of ROS in regulation of signal amplification and specificity in guard cells.

Green nectaries: the role of photosynthesis in secretion

Green nectaries have been frequently mentioned in the literature, leading to the assumption that photosynthesis of nectaries can supply the carbohydrates secreted in the nectar, especially when storage of starch is seen in the plastids in nectaries and this starch disappears during secretion. Photosynthesis in nectaries can also provide reduction equivalents for the nectar–redox cycle and energy for secretion. However, quantitative data on the photosynthetic capacity of nectaries are largely missing. Therefore, in the present study, the photosynthetic capacity of green nectaries from a range of plants was screened; 20 floral nectaries (including six septal nectaries) and six extrafloral nectaries were studied. For the screening, chlorophyll fluorescence parameters were measured as depending on photosynthetic photon flux density (PPFD). Parameters measured were basic ground fluorescence (F) and quantum yield (Y0) of the dark adapted sample at 0 PPFD. From the light saturation curves saturating PPFD (PPFDsat), quantum yield at saturation (Ysat) and maximum apparent photosynthetic electron transport rates (ETRmax) were obtained. For comparison, leaves of the plants were also measured. In most cases, the performance of the nectaries was lower than that of the leaves. F was lower in 14 floral and four extrafloral nectaries (69% of total), ETRmax was lower in 18 floral and four extrafloral nectaries (85%), Ysat was lower in 15 floral and three extrafloral nectaries (69%). In 18 floral and two extrafloral nectaries (77%) Y0 was well below 0.8, indicating photoinhibition. In contrast, the range of ETRmax for green nectaries was 25–140 μmol m−2 s−1 and overlaps well with that of green tissues in general. The lower end of the range of rates of photosynthetic carbon dioxide (CO2) uptake of sun leaves in the literature is 10 μmol CO2 m−2 s−1. Taking this value for sun-adapted green nectaries, i.e. having a PPFDsat > 1000 μmol m−2 s−1, with an area of nectar tissue measured as 3–50 mm2 per flower, sugar secretion related to photosynthetic CO2 fixation in the green nectaries is estimated at approximately 0.2–3.0 μmol hexose units flower−1 day−1. This is compares well in order of magnitude with the range of secretion given in the literature and clearly suggests that photosynthetic activity of green nectaries can explain a significant part, if not all, of the sugar secreted. In some nectaries ETR did not saturate with PPFD. This could be attributable to spillover from photosystem II to photosystem I and cyclic photosynthetic electron transport. It is in agreement with observations in the literature and my preliminary findings that nectary plastids often lack grana thylakoids where photosytem II is located. Cyclic photophosphorylation could provide adenosine triphosphate (ATP) energy for the nectaries. This needs further investigation. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2013, 173, 1–11.

Ecosystem photosynthesis inferred from measurements of carbonyl sulphide flux

Carbonyl sulphide is taken up by plants, and could potentially serve as a powerful proxy for photosynthetic carbon dioxide uptake. Field measurements in Israel suggest that carbonyl sulphide fluxes provide an independent constraint on indirect estimates of ecosystem photosynthesis.

Calibration of Simultaneous Measurements of Photosynthetic Carbon Dioxide Uptake and Oxygen Evolution in Leaves

The stoichiometric ratio of O2 evolution to CO2 uptake during photosynthesis reveals information about reductive metabolism, including the reduction of alternative electron acceptors, such as nitrite and oxaloacetate. Recently we reported that in simultaneous measurements of CO2 uptake and O2 evolution in a sunflower leaf, O2 evolution changed by 7% more than CO2 uptake when light intensity was varied. Since the O2/CO2 exchange ratio is approximately 1, small differences are important. Thus, these gas exchange measurements need precise calibration. In this work, we describe a new calibration procedure for such simultaneous measurements, based on the changes of O2 concentration caused by the addition of pure CO2 or O2 into a flow of dry air (20.95% O2) through one and the same capillary. The relative decrease in O2 concentration during the addition of CO2 and the relative increase in O2 concentration during the addition of O2 allowed us to calibrate the CO2 and O2 scales of the measurement system with an error (relative standard deviation, RSD) of <1%. Measurements on a sunflower leaf resulted in an O2/CO2 ratio between 1.0 and 1.03 under different CO2 concentrations and light intensities, in the presence of an ambient O2 concentration of 20-50 micromol mol(-1). This shows that the percentage use of reductive power from photochemistry in synthesis of inorganic or organic matter other than CO2 assimilation in the C3 cycle is very low in mature leaves and, correspondingly, the reduction of alternative acceptors is a weak source of coupled ATP synthesis.

Response of CO2 uptake, chlorophyll content, and some productional features of forest herb Smyrnium perfoliatum L. (Apiaceae) to different light conditions

Smyrnium perfoliatum L. (Apiaceae), an endangered summer forest herb grown in the understory of dominant oak-hornbeam stands in Devinska Kobyla, Little Carpathians region in SW Slovakia, is considered to form at least five leaf types of different physiological and anatomical quality. These observation are based upon the estimated differences of photosynthetic carbon dioxide uptake, chlorophyll content, leaf anatomy, and several quantitative parameters of growth analysis. There is a further attempt to establish, to what extent the daily changing environment, especially the excess of light of fast-moving sun-flecks by the photosynthetic apparatus within any leaf type, according to its dominant shade adaptation could be effectively used.

Plant Production and Emission of Volatile Organic Compounds

\AI ways in which plant proV cesses influence the atmosphere, most biologists first think of photosynthetic oxygen production and carbon dioxide uptake. Given a few more minutes, many will also point out that plant transpiration of water plays a role in the chemistry of the troposphere (the lower 10 km of the atmosphere). Few, however, are aware that plant processes play key roles in ozone production, methane oxidation, and the global carbon monoxide budget. Several biologists and atmospheric chemists have recognized the effects of plants on the atmosphere (Rasmussen 1972, Tyson et al. 1974, Went 1960), but only recently has research into chemical emissions from plants advanced beyond a curiosity of interest to only a handful of environmental scientists. The topic of plant chemical emissions and their role in

Photosynthetic carbon dioxide uptake and oxygen accumulation during in vitro culture of Actinidia deliciosa cv tomuri

Proliferating cultures of Actinidia deliciosa cv Tomuri were grown in vitro under a photosynthetic photon flux density (PPFD) of 120 μmol m 2/s. Some jars were daily enriched with 2000 μl/l CO 2 administered at the end of the dark period. Head space analysis revealed that CO 2 accumulated up to 9500 μl/l during the dark period and was drastically reduced by photosynthetic activity to 150–200 μl/l during the photoperiod without any significant difference between CO 2-enriched and non-enriched cultures. Oxygen concentration assayed at the end of the photoperiod showed a steady increase during the 44 days of culture and was not reduced to atmospheric values by respiratory processes during the dark period. CO 2 enrichment enhanced O 2 production and accumulation to 32.5% at the end of the culture period. Oxygen photoreduction and its photo-oxidative damage to green tissue cells are discussed.

Abscisic acid mimics effects of dehydration on area expansion and photosynthetic partitioning in young soybean leaves

Abstract. Leaf area expansion, photosynthetic carbon dioxide uptake and leaf dry mass accumulation were compared for expanding leaves of well‐watered soybean (Glycine max [L.] Merr.) plants, mildly dehydrated plants and well‐watered plants treated with abscisic acid (ABA). Both ABA treatment and dehydration reduced area expansion in the light and over a 24 h period without decreasing the photosynthetic rates of expanding leaves. Dry mass accumulation during the light was less in ABA‐treated and water‐stressed leaves than in control leaves, with no differences among treatments in leaf mass per unit of area. ABA treatment and water stress both increased export of carbon from expanding leaves in the light. ABA applied near the end of the light period also increased export of carbon during the following dark period. However, it is unlikely that decreased availability of photosynthate caused slow expansion in the ABA and dehydration treatments, because expansion rates were not slowed in plants kept in dim light, even though photosynthetic rates and dry mass accumulation rates were greatly reduced. The data suggest that ABA may mediate the effects of mild dehydration on leaf area expansion and partitioning of photosynthate.

Assimilation of Gaseous Ammonia by Sunflower Leaves during Photosynthesis

Illuminated (150 �mol m-2 s-1 PAR) sunflower (Helianthus annuus L.) leaves were exposed to 15N-labelled NH3 gas (30 or 300 �l NH3 l-1) or supplied with NH4Cl (2, 20 or 200 mM) through the cut leaf base for up to 1 h. The photosynthetic carbon dioxide uptake and the transpiration were continuously monitored. The leaves were extracted and the concentrations of ammonia, glutamine, glutamate, glycine, serine and alanine were determined as well as the patterns of 15N incorporation. Although the rates of CO2 uptake and transpiration were unchanged in intact leaves, the ammonia level increased from 3 to 42 �mol g fresh wt-1 during feedings of 300 �l NH3 l-1 for 25 min. In contrast, NH4Cl (20 and 200 mM) inhibited photosynthesis immediately and increased the evaporation rate while the total ammonia level was still less than 10 �mol g fresh wt-1. The 15N-labelling pattern suggested that the NH3 assimilation proceeded via glutamine synthetase and glutamate synthase. 15N was transferred into glycine and serine presumably by the activity of glycollate pathway enzymes. The experiments demonstrate that the photosynthetic CO2 uptake and ammonia assimilation by intact sunflower leaves were not inhibited by NH3 concentrations orders of magnitudes above typical concentrations of this compound in the atmosphere. NH3 feedings through the gas phase provide a tool for the examination of nitrogen metabolism in intact leaves.

Mesophyll resistance to photosynthetic carbon dioxide uptake in leaves: dependence upon stomatal aperture

A model for carbon dioxide uptake by plant leaves, based on the partial differential equation for diffusion with chemical reaction, is used to simulate photosynthesis for various stomatal openings. The results show that not only the "stomatal resistance" but also the commonly calculated "mesophyll resistance" varies when nothing but stomatal aperture is changed. Simplistic uses of the resistance concept (or related conductances) may be more misleading than useful for modelling photosynthesis, because the various resistance components are neither independent nor additive.

Chlorophyll formation and the development of photosynthesis in dark grown seedlings of Picea abies

Abstract Seeds of Picea abies were germinated and grown in either darkness or constant light. The chlorophyll content and photosynthetic carbon dioxide uptake of developing seedlings of different ages was determined. Ten‐day‐old dark grown seedlings showed an instant ability for photosynthetic carbon dioxide uptake and also formed further chlorophyll most rapidly upon subsequent illumination. These activities progressively diminished when the dark growth period was extended. Light grown seedlings reached a maximum chlorophyll level after 15 days growth, and this preceded maximal photosynthetic development.

Effects of α-Hydroxy-2-Pyridinemethanesulfonic Acid on Photosynthetic Carbon Dioxide Uptake and Stomatal Movements in Excised Tomato Leaves

The effects of 10(-2)m alpha-hydroxy-2-pyridinemethanesulfonic acid (alphaHPMS) on the CO(2) compensation point, photosynthetic CO(2) uptake, CO(2) evolution into CO(2)-free air in light, and stomatal movement, in excised tomato leaves (Lycopersicon esculentum Mill. Eurocross BB-F(1) Hybrid) were studied. It was found that alpha-HPMS had a transient lowering effect on the CO(2) compensation point of treated leaves within the first 5 minutes of application. The net photosynthetic CO(2) uptake was inhibited by alpha-HPMS treatment. The inhibition increased with time and was enhanced in an O(2)-free atmosphere. The CO(2) evolution into CO(2)-free air in light was inhibited by alpha-HPMS. The inhibition was O(2)-dependent because the effect was observed only in 21% O(2) but not in O(2)-free N(2). Stomatal apertures were affected by alpha-HPMS, but the effect was transient and was observed 15 to 30 minutes after the application. The time course of this closure did not account for the observed inhibition of net CO(2) uptake.

Comparative studies on the activity of carboxylases and other enzymes in relation to the new pathway of photosynthetic carbon dioxide fixation in tropical grasses.

1. The activity per unit of chlorophyll of certain carboxylases, and of other enzymes involved in photosynthesis, was determined in leaf extracts of the tropical grasses, sugar-cane, maize and sorghum, and compared with the activities for wheat, oat and silver-beet. Maximum rates of photosynthetic carbon dioxide uptake were also measured for comparison with enzyme activities. 2. Phosphopyruvate carboxylase activity was about 60 times greater in the tropical grasses than in wheat, oat and silver-beet and was severalfold higher than the rates of photosynthetic carbon dioxide uptake. Most of the enzyme was located in the chloroplast fraction of cell extracts. 3. Phosphopyruvate carboxylase was apparently the major photosynthetic carbon dioxide-fixing enzyme in the tropical grasses, although malic enzyme may contribute to a lesser extent. 4. Tropical grasses contained less than one-tenth of the ribulose diphosphate carboxylase activity present in wheat, oat and silver-beet. For the tropical grasses this activity, determined with a saturating concentration of bicarbonate, was approx. 10% of the rate of photosynthesis. 5. The fraction-1 protein content of leaf extracts paralleled the ribulose diphosphate carboxylase activity. 6. In contrast, the activity of several other enzymes of the Calvin cycle was similar in the different species examined.

Increased Rate of Net Photosynthetic Carbon Dioxide Uptake Caused by the Inhibition of Glycolate Oxidase

There is considerable variation among species in their rate of photorespiration, and photorespiration increases greatly at higher temperatures. The addition of an inhibitor of glycolate oxidase, alpha-hydroxy-2-pyridinemethanesulfonic acid, to tobacco leaf disks at 35 degrees stimulated photosynthetic (14)CO(2) uptake at least 3-fold, but (14)CO(2) uptake was not changed by the inhibitor at 25 degrees . The inhibitor did not increase photosynthesis in maize leaf disks at either temperature.The evolution of CO(2) from glycolate was greatly enhanced in tobacco at 35 degrees compared with 25 degrees . Labeling of the glycolate of tobacco with glycolate-1-(14)C and -2-(14)C showed that the increased CO(2) evolved in the light (photorespiration) arose specifically from the carboxyl-carbon atom of glycolate. Maize, a species known to have a negligible photorespiration, produced (14)CO(2) poorly from glycolate-1-(14)C in comparison to tobacco.Acetate-1-(14)C, a substrate metabolized by dark respiration, produced similar amounts of (14)CO(2) in the light in both tobacco and maize. This respiration was changed little relative to photosynthesis by increasing temperature.Most plants, such as tobacco, have a high photorespiration. The loss of fixed carbon causes an increase in the internal concentration of CO(2) especially at higher temperatures, and results in a lower CO(2) concentration gradient and therefore a lower net photosynthetic CO(2) uptake. Some species, like maize, have a negligible photorespiration and are thus more efficient photosynthetically. The use of an inhibitor of the oxidation of glycolate, the substrate for photorespiration, changed tobacco so that it behaved photosynthetically like maize. Thus high rates of photorespiration may limit the net CO(2) uptake in many plant species.

Photosynthetic Adaptation to Light Intensity in Plants Native to Shaded and Exposed Habitats

AbstractPhotosynthetic adaptation to light intensity has been studied in clones of populations from shaded and exposed habitats of Rumex acetosa and Geum rivale. Clones of the shade species Lamium galeobdolon and the sun species Plantago lanceolata were also included for comparison. The plants were grown under controlled conditions at a high and a low light intensity. The capacity of photosynthetic carbon dioxide uptake at low as well as at saturating light intensities was determined on single attached leaves.As was previously demonstrated in Solidago virgaurea, clones of populations native to shaded and to exposed environments show differences in the photosynthetic response to light intensity during growth. The data provide evidence that populations of the same species native to habitats with contrasting light intensities differ in their photosynthetic properties in an adaptive manner Ln a similar mode as sun and shade species.