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  • Articles: DFG German National Licenses  (10)
  • C4 photosynthesis  (8)
  • C3  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Photosynthetic acclimation of maize to growth under elevated levels of carbon dioxide (1999)
    Springer
    Planta 210 (1999), S. 115-125 
    Details
    ISSN: 1432-2048
    Keywords: Key words: CO2 enrichment ; C4 photosynthesis ; Respiration ; Zea (CO2 enrichment)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. The effects of elevated CO2 concentrations on the photochemistry, biochemistry and physiology of C4 photosynthesis were studied in maize (Zea mays L.). Plants were grown at ambient (350 μL L−1) or ca. 3 times ambient (1100 μL L−1) CO2 levels under high light conditions in a greenhouse for 30 d. Relative to plants grown at ambient CO2 levels, plants grown under elevated CO2 accumulated ca. 20% more biomass and 23% more leaf area. When measured at the CO2 concentration of growth, mature leaves of high-CO2-grown plants had higher light-saturated rates of photosynthesis (ca. 15%), lower stomatal conductance (71%), higher water-use efficiency (225%) and higher dark respiration rates (100%). High-CO2-grown plants had lower carboxylation efficiencies (23%), measured under limiting CO2, and lower leaf protein contents (22%). Activities of a number of C3 and C4 cycle enzymes decreased on a leaf-area basis in the high-CO2-grown plants by 5–30%, with NADP-malate dehydrogenase exhibiting the greatest decrease. In contrast, activities of fructose 1,6-bisphosphatase and ADP-glucose pyrophosphorylase increased significantly under elevated CO2 condition (8% and 36%, respectively). These data show that the C4 plant maize may benefit from elevated CO2 through acclimation in the capacities of certain photosynthetic enzymes. The increased capacity to synthesize sucrose and starch, and to utilize these end-products of photosynthesis to produce extra energy by respiration, may contribute to the enhanced growth of maize under elevated CO2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004250050660
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  • 2
    Electronic Resource
    Electronic Resource
    Inhibition of C4 photosynthesis by (benzamidooxy)acetic acid (1982)
    Springer
    Photosynthesis research 3 (1982), S. 293-305 
    Details
    ISSN: 1573-5079
    Keywords: aspartate and alanine aminotransferases ; (benzamidooxy)acetic acid ; C4 photosynthesis ; herbicide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract (Benzamidooxy)acetic acid (common name benzadox) which has herbicidal properties was evaluated as a potential inhibitor of photosynthesis in C4 plants. Among enzymes of the C4 pathway, it was a relatively strong inhibitor of alanine aminotransferase in in vitro experiments at concentrations of 5mM. In benzadox treated leaves of Panicum miliaceum, a NAD-malic enzyme type C4 species, there was strong inhibition of both alanine and aspartate aminotransferase and of photosynthetic O2 evolution within one hour. Consistent with the inhibition of these enzymes of the C4 cycle, the pool sizes of metabolites of the cycle was altered: the aspartate level was increased two fold, while the levels of other metabolites such as pyruvate, alanine, oxalacetate and malate were decreased. Kinetic studies with partially purified alanine aminotransferase showed that benzadox is a competitive inhibitor with respect to alanine and a noncompetitive inhibitor with respect to 2-oxoglutarate. Comparisons between the structures and inhibitory actions of benzadox and (aminooxy)acetic acid, the latter a potent inhibitor of alanine and aspartate aminotransferases, suggest that in vivo, benzadox may exert its effect through metabolism to (aminooxy)acetic acid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00034110
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  • 3
    Electronic Resource
    Electronic Resource
    Can CO2 assimilation in maize leaves be predicted accurately from chlorophyll fluorescence analysis? (1993)
    Springer
    Photosynthesis research 37 (1993), S. 89-102 
    Details
    ISSN: 1573-5079
    Keywords: C4 photosynthesis ; chlorophyll fluorescence ; CO2 assimilation ; maize ; Photosystem II ; quantum yield
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Analysis is made of the energetics of CO2 fixation, the photochemical quantum requirement per CO2 fixed, and sinks for utilising reductive power in the C4 plant maize. CO2 assimilation is the primary sink for energy derived from photochemistry, whereas photorespiration and nitrogen assimilation are relatively small sinks, particularly in developed leaves. Measurement of O2 exchange by mass spectrometry and CO2 exchange by infrared gas analysis under varying levels of CO2 indicate that there is a very close relationship between the true rate of O2 evolution from PS II and the net rate of CO2 fixation. Consideration is given to measurements of the quantum yields of PS II (φ PS II) from fluorescence analysis and of CO2 assimilation ( $$\phi _{CO_2 } $$ ) in maize over a wide range of conditions. The $${{\phi _{PSII} } \mathord{\left/ {\vphantom {{\phi _{PSII} } {\phi _{CO_2 } }}} \right. \kern-\nulldelimiterspace} {\phi _{CO_2 } }}$$ ratio was found to remain reasonably constant (ca. 12) over a range of physiological conditions in developed leaves, with varying temperature, CO2 concentrations, light intensities (from 5% to 100% of full sunlight), and following photoinhibition under high light and low temperature. A simple model for predicting CO2 assimilation from fluorescence parameters is presented and evaluated. It is concluded that under a wide range of conditions fluorescence parameters can be used to predict accurately and rapidly CO2 assimilation rates in maize.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02187468
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  • 4
    Electronic Resource
    Electronic Resource
    Light/dark modulation of phosphoenolpyruvate carboxylase in C3 and C4 species (1994)
    Springer
    Photosynthesis research 42 (1994), S. 133-143 
    Details
    ISSN: 1573-5079
    Keywords: PEP carboxylase ; C3 ; C4
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In this report, the effects of light on the activity and allosteric properties of phosphoenolpyruvate (PEP) carboxylase were examined in newly matured leaves of several C3 and C4 species. Illumination of previously darkened leaves increased the enzyme activity 1.1 to 1.3 fold in C3 species and 1.4 to 2.3 fold in C4 species, when assayed under suboptimal conditions (pH 7) without allosteric effectors. The sensitivities of PEP carboxylase to the allosteric effectors malate and glucose-6-phosphate were markedly different between C3 and C4 species. In the presence of 5 mM malate, the activity of the enzyme extracted from illuminated leaves was 3 to 10 fold higher than that from darkened leaves in C4 species due to reduced malate inhibition of the enzyme from illuminated leaves, whereas it increased only slightly in C3 species. The Ki(malate) for the enzyme increased about 3 fold by illumination in C4 species, but increased only slightly in C3 species. Also, the addition of the positive effector glucose-6-phosphate provided much greater protection against malate inhibition of the enzyme from C4 species than C3 species. Feeding nitrate to excised leaves of nitrogen deficient plants enhanced the degree of light activation of PEP carboxylase in the C4 species maize, but had little or no effect in the C3 species wheat. These results suggest that post-translational modification by light affects the activity and allosteric properties of PEP carboxylase to a much greater extend in C4 than in C3 species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02187124
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  • 5
    Electronic Resource
    Electronic Resource
    CO2 and O2 dependence of PS II activity in C4 plants having genetically produced deficiencies in the C3 or C4 cycle (1998)
    Springer
    Photosynthesis research 58 (1998), S. 91-101 
    Details
    ISSN: 1573-5079
    Keywords: C4 photosynthesis ; PEP carboxylase mutants ; Photosystem II ; Rubisco transgenic plants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The CO2 dependence of rates of CO2 fixation (A) and photochemistry of PS II at 5, 15 and 30% O2 were analyzed in the C4 plant Amaranthus edulis having a C4 cycle deficiency [phosphoenolpyruvate carboxylase (PEPC) mutants], and in the C4 plant Flaveria bidentis having a C3 cycle deficiency [Rubisco small subunit antisense (αSSU)]. In the wild type (WT) A. edulis and its heterozygous mutant having less than 50% WT PEPC activity there was a similar dependence of A and PS II photochemistry on varying CO2, although the CO2 saturated rates were 25% lower in heterozygous plants. The homozygous plants having less than 2% PEPC of the WT had significant levels of photorespiration at ambient levels of CO2 and required about 30 times ambient levels for maximum rates of A. Despite variation in the capacity of the C4 cycle, more than 91% of PS II activity was linearly associated with A under varying CO2 at 5, 15 and 30% O2. However, the WT plant had a higher PS II activity per CO2 fixed under saturating CO2 than the homozygous mutant, which is suggested to be due to elimination of the C4 cycle and its associated requirement for ATP from a Mehler reaction. In the αSSU F. bidentis plants, a decreased rate of A (35%) and PS II activity (33%) accompanied a decrease in Rubisco capacity. There was some increase in alternative electron sinks at high CO2 when the C3 cycle was constrained, which may be due to increased flux through the C4 cycle via an ATP generating Mehler reaction. Nevertheless, even with constraints on the function of the C4 or C3 cycle by genetic modifications, analyses of CO2 response curves under varying levels of O2 indicate that CO2 assimilation is the main determinant of PS II activity in C4 plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006176713574
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  • 6
    Electronic Resource
    Electronic Resource
    A mathematical model of C4 photosynthesis: The mechanism of concentrating CO2 in NADP-malic enzyme type species (2000)
    Springer
    Photosynthesis research 66 (2000), S. 199-224 
    Details
    ISSN: 1573-5079
    Keywords: C4 photosynthesis ; modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A computer model comprising light reactions in PS II and PS I, electron-proton transport reactions in mesophyll and bundle sheath chloroplasts, all enzymatic reactions and most of the known regulatory functions of NADP-ME type C4 photosynthesis has been developed as a system of differential budget equations for intermediate compounds. Rate-equations were designed on principles of multisubstrate-multiproduct enzyme kinetics. Some of the 275 constants needed (ΔG0′ and K m values) were available from literature and others (V m) were estimated from reported rates and pool sizes. The model provided good simulations for rates of photosynthesis and pool sizes of intermediates under varying light, CO2 and O2. A basic novelty of the model is coupling of NADPH production via NADP-ME with ATP production and regulation of the C3 cycle in bundle sheath chloroplasts. The functional range of the ATP/NADPH ratio in bundle sheath chloroplasts extends from 1.5 to 2.1, being energetically most efficient around 2. In the presence of such stoichiometry, the CO2 concentrating function can be explained on the basis of two processes: (a) extra ATP consumption for starch and protein synthesis in bundle sheath leads to a faster NADPH and CO2 import compared with CO2 fixation in bundle sheath, and (b) the residual photorespiratory activity consumes RuBP by oxygenation, NADPH and ATP and causes the imported CO2 to accumulate in bundle sheath cells. As a wider application, the model may be used for predicting results of genetic engineering of plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010695402963
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  • 7
    Electronic Resource
    Electronic Resource
    Light and temperature dependence of the rate and degree of activation of pyruvate, Pi dikinase in vivo in maize (1980)
    Springer
    Photosynthesis research 1 (1980), S. 199-207 
    Details
    ISSN: 1573-5079
    Keywords: C4 photosynthesis ; maize ; pyruvate ; Pi dikinase ; temperature and light
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Activation of pyruvate,Pi dikinase by light was studied in leaf discs of maize which were illuminated for 1 h at light intensities ranging from approximately 3% to 50% of full sunlight and at temperatures of 10, 22.5, and 35°C. At the highest light intensity the degree of activation was similar and relatively independent of temperature between 10 and 35°C. Under low light the degree of activation was high at 10°C but decreased rapidly with increasing temperature. There was a similar effect of light and temperature on the activation of NADP-malate dehydrogenase. At low temperature, the rate of activation of pyruvate,Pi dikinase was relatively low and independent of the light intensity used and the rate of inactivation in the dark was extremely low. At high temperature, the rate of activation was high and dependent on the light intensity used while the rate of dark inactivation was also relatively high. The degree of activation is discussed in relation to the possible influence of light and temperature on the turnover between the active and inactive forms of pyruvate,Pi dikinase during illumination.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00020599
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  • 8
    Electronic Resource
    Electronic Resource
    Reduction in chlorophyll content without a corresponding reduction in photosynthesis and carbon assimilation enzymes in yellow-green oil yellow mutants of maize (1989)
    Springer
    Photosynthesis research 20 (1989), S. 191-205 
    Details
    ISSN: 1573-5079
    Keywords: carbon assimilation ; maize ; mutants ; C4 photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The photosynthetic properties of a yellow lethal mutant, Oy/oy, and two yellow-green mutants of maize which are allelic (a homozygous recessive oy/oy and a heterozygous dominant Oy/+) were examined. Although Oy/oy had little or no chlorophyll or capacity for CO2 fixation compared to normal siblings, it had 28% as much ribulose-1,5-bisphosphate carboxylase oxygenase (Rubisco) activity, and from 40% to near normal activities of C4 cycle enzymes. Both yellow-green mutants had only half as much chlorophyll per leaf area as normal green seedlings in greenhouse-grown plants in winter and spring. However, the absorbance of light by the mutants was relatively high, as their transmittance was only 5 to 8% greater than normal leaves. In winter-grown greenhouse plants, the activities of Rubisco and several C4 cycle enzymes in the mutants were unaffected and similar to those of normal seedlings on a leaf area basis. After allowing for small differences in leaf absorbance, the light response curves for photosynthesis in the mutants were similar on a leaf area basis but much higher on a chlorophyll basis than those of the normal seedlings. In spring-grown greenhouse plants the enzyme activities and photosynthesis rates were about 30% lower per leaf area in the yellow-green mutant leaves compared to the wild type. The maximum carboxylation efficiency (measured under low CO2 and 1000 μmol quanta m-2 s-1) in the mutants and normal leaves was similar on a Rubisco protein basis. The results indicate that maize can undergo a 50% reduction in chlorophyll content without a corresponding reduction in enzymes of carbon assimilation, and still maintain a high capacity for photosynthesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00034126
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  • 9
    Electronic Resource
    Electronic Resource
    Electron flow accompanying the ascorbate peroxidase cycle in maize mesophyll chloroplasts and its cooperation with linear electron flow to NADP+ and cyclic electron flow in thylakoid membrane energization (1997)
    Springer
    Photosynthesis research 52 (1997), S. 187-198 
    Details
    ISSN: 1573-5079
    Keywords: ascorbate ; C4 photosynthesis ; electron transport ; maize mesophyll chloroplasts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Potential roles for cyclic and pseudocyclic electron flow in C4 plants are to provide ATP for the C4 cycle and, under excess light, to down-regulate PS II activity through membrane energization. Intact mesophyll chloroplasts of maize were used to evaluate forms of electron transport including the Mehler peroxidase reaction (linear electron flow to O2, formation of H2O2 which is reduced by ascorbate, and linear flow linked to reduction of oxidized ascorbate). Addition of H2O2 to isolated chloroplasts in the light in the presence of an uncoupler induced Photosystem (PS) II activity, as determined from increases in photochemical quenching of chlorophyll fluorescence (qp) and the quantum yield of PS II. H2O2 also induced dissipation of energy by thylakoid membrane energization and non-photochemical fluorescence quenching (qn), which was inhibited by addition of an uncoupler. These effects of H2O2 on qp and qn were inhibited by addition of KCN, an inhibitor of ascorbate peroxidase. The results suggest that H2O2 is reduced via ascorbate, and that the oxidized ascorbate is then reduced by linear electron flow contributing to photochemistry and thylakoid membrane energization. Evidence for function of pseudocyclic electron flow via the Mehler peroxidase reaction was obtained with only oxygen as an electron acceptor, as well as in the presence of oxaloacetate a natural electron acceptor in C4 photosynthesis. KCN decreased qp and PS II yield in the absence and presence of oxaloacetate and, in the former case, it severely reduced q_n. KCN also decreased ΔpH formation across the thylakoid membrane based on its decrease in the light-induced quenching of 9-aminoacridine fluorescence, particularly in the absence of oxaloacetate. Antimycin A, an inhibitor of cyclic electron flow, also diminished ΔpH formation. These results provide evidence for shared energization of thylakoid membranes by the Mehler peroxidase reaction, cyclic electron flow, and linear electron flow linked to the C4 pathway.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005850207799
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  • 10
    Electronic Resource
    Electronic Resource
    Malate metabolism by NADP-malic enzyme in plant defense (1999)
    Springer
    Photosynthesis research 61 (1999), S. 99-105 
    Details
    ISSN: 1573-5079
    Keywords: C3 ; C4 ; UV-B ; stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Malate is involved in various metabolic pathways, and there are several enzymes that metabolize it. One important malate metabolizing enzyme is NADP-malic enzyme (NADP-ME). NADP-ME functions in many different pathways in plants, having an important role in C4 photosynthesis where it releases the CO2 to be used in carbon fixation by Rubisco. Apart from this specialized role, NADP-ME is thought to fulfill diverse housekeeping functions because of its universal presence in different plant tissues. NADP-ME is induced after wounding or exposure to UV-B radiation. In this way, the enzyme is implicated in defense-related deposition of lignin by providing NADPH for the two NADPH-dependent reductive steps in monolignol biosynthesis. On the other hand, it can supply NADPH for flavonoid biosynthesis as many steps in the flavonoid biosynthesis pathway require reductive power. Pyruvate, another product of NADP-ME reaction, can be used for obtaining ATP through respiration in the mitochondria; and may serve as a precursor for synthesis of phosphoenolpyruvate (PEP). PEP is utilized in the shikimate pathway, leading to the synthesis of aromatic amino acids including phenylalanine, the common substrate for lignin and flavonoid synthesis. Moreover, NADP-ME can be involved in mechanisms producing NADPH for synthesis of activated oxygen species that are produced in order to kill or damage pathogens. In conclusion, an increase in the levels of NADP-ME could provide building blocks and energy for biosynthesis of defense compounds, suggesting a role of malate metabolism in plant defense.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006209003096
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