H. Eichelmann - Academia.edu (original) (raw)
Papers by H. Eichelmann
This paper is available online free of all access charges (see
Soviet Plant Physiology, 1990
Journal of Experimental Botany, 2009
Site turnover rate (k cat) of Rubisco was measured in intact leaves of different plants. Potato (... more Site turnover rate (k cat) of Rubisco was measured in intact leaves of different plants. Potato (Solanum tuberosum L.) and birch (Betula pendula Roth.) leaves were taken from field-growing plants. Sunflower (Helianthus annuus L.), wild type (wt), Rubisco-deficient (-RBC), FNR-deficient (-FNR), and Cyt b 6 f deficient (-CBF) transgenic tobacco (Nicotiana tabacum L.) were grown in a growth chamber. Rubisco protein was measured with quantitative SDS-PAGE and FNR protein content with quantitative immunoblotting. The Cyt b 6 f level was measured in planta by maximum electron transport rate and the photosystem I (PSI) content was assessed by titration with far-red light. The CO 2 response of Rubisco was measured in planta with a fast-response gas exchange system at maximum ribulose 1,5-bisphosphate concentration. Reaction site k cat was calculated from V m and Rubisco content. Biological variation of k cat was significant, ranging from 1.5 to 4 s 21 in wt, but was >6 s 21 at 23°C in-RBC leaves. The lowest k cat of 0.5 s 21 was measured in-FNR and-CBF plants containing sufficient Rubisco but having slow electron transport rates. Plotting k cat against PSI per Rubisco site resulted in a hyperbolic relationship where wt plants are on the initial slope. A model is suggested in which Rubisco Activase is converted into an active ATP-form on thylakoid membranes with the help of a factor related to electron transport. The activation of Rubisco is accompanied by the conversion of the ATP-form into an inactive ADP-form. The ATP and ADP forms of Activase shuttle between thylakoid membranes and stromally-located Rubisco. In normal wt plants the electron transport-related activation of Activase is rate-limiting, maintaining 50-70% Rubisco sites in the inactive state.
Plant and Cell Physiology, 2007
Measurements of 810 nm transmittance changes in leaves, simultaneously with Chl fluorescence, CO ... more Measurements of 810 nm transmittance changes in leaves, simultaneously with Chl fluorescence, CO 2 uptake and O 2 evolution, were carried out on potato (Solanum tuberosum L.) leaves with altered expression of plastidic NADP-dependent malate dehydrogenase. Electron transport rates were calculated: J C from the CO 2 uptake rate considering ribulose-1,5-bisphosphate (RuBP) carboxylation and oxygenation, J O from the O 2 evolution rate, J F from Chl fluorescence parameters and J I from the post-illumination re-reduction speed of PSI donors. In the absence of external O 2 , J O equaled (1.005 AE 0.003) J C , independent of the transgenic treatment, light intensity and CO 2 concentration. This showed that nitrite and oxaloacetate reduction rates were very slow. The Mehler-type O 2 reduction was evaluated from the rate of electron accumulation at PSI after the O 2 concentration was decreased from 210 to 20 mmol mol À1 , and resulted in 51% of the linear flow. J F and J I did not differ from J C while photosynthesis was light-limited, but considerably exceeded J C at saturating light. Then, typically, J F ¼ 1.2 J C and J I ¼ 1.3 J C , and J F ÀJ C and J I ÀJ C depended little on CO 2 and O 2 concentrations. The results showed that the alternative and cyclic electron flow necessary to compensate variations in the ATP/NADPH ratio were only a few percent of the linear flow. The data do not support the requirement of 14H þ /3ATP by the chloroplast ATP synthase. We suggest that the fast PSI cyclic electron flow J I À J C , as well as the fast J F À J C are energy-dissipating cycles around PSI and PSII at light saturation.
Plant physiology
Sunflower (Helianthus annuus L.), cotton (Gossypium hirsutum L.), tobacco (Nicotiana tabacum L.),... more Sunflower (Helianthus annuus L.), cotton (Gossypium hirsutum L.), tobacco (Nicotiana tabacum L.), sorghum (Sorghum bicolor Moench.), amaranth (Amaranthus cruentus L.), and cytochrome b6f complex-deficient transgenic tobacco leaves were used to test the response of plants exposed to differnt light intensities and CO2 concentrations before and after photoinhibition at 4000 [mu]mol photons m-2 s-1 and to thermoinhibition up to 45[deg]C. Quantum yields of photochemical and nonphotochemical excitation quenching (YP and YN) and the corresponding relative rate constants for excitation capture from the antenna-primary radical pair equilibrium system (k[prime]P and k[prime]N) were calculated from measured fluorescence parameters. The above treatments resulted in decreases in YP and K[prime]P and in approximately complementary increases in YN and K[prime]N under normal and inhibitory conditions. The results were reproduced by a mathematical model of electron/proton transport and O2 evolution/...
Plant physiology, 1994
CO2 uptake rate, chlorophyll fluorescence, and 830-nm absorbance were measured in wild-type (wt) ... more CO2 uptake rate, chlorophyll fluorescence, and 830-nm absorbance were measured in wild-type (wt) Nicotiana sylvestris (Speg. et Comes) and starchless mutant NS 458 leaves at different light intensities and CO2 concentrations. Initial slopes of the relationships between CO2 uptake and light and CO2 were similar, but the maximum rate at CO2 and light saturation was only 30% in the mutant compared with the wt. O2 enhancement of photosynthesis at CO2 and light saturation was relatively much greater in the mutant than in the wt. In 21% O2, the electron transport rate (ETR) calculated from fluorescence peaked near the beginning of the CO2 saturation of photosynthesis. With the further increase of CO2 concentration ETR remained nearly constant or declined a little in the wt but drastically declined in the mutant. Absorbance measurements at 830 nm indicated photosystem I acceptor side reduction in both plants at saturating CO2 and light. Assimilatory charge (postillumination CO2 uptake) mea...
Plant physiology, 1997
Sunflower (Helianthus annuus L.), cotton (Gossypium hirsutum L.), tobacco (Nicotiana tabacum L.),... more Sunflower (Helianthus annuus L.), cotton (Gossypium hirsutum L.), tobacco (Nicotiana tabacum L.), sorghum (Sorghum bicolor Moench.), amaranth (Amaranthus cruentus L.), and cytochrome b6f complex-deficient transgenic tobacco leaves were used to test the response of plants exposed to differnt light intensities and CO2 concentrations before and after photoinhibition at 4000 [mu]mol photons m-2 s-1 and to thermoinhibition up to 45[deg]C. Quantum yields of photochemical and nonphotochemical excitation quenching (YP and YN) and the corresponding relative rate constants for excitation capture from the antenna-primary radical pair equilibrium system (k[prime]P and k[prime]N) were calculated from measured fluorescence parameters. The above treatments resulted in decreases in YP and K[prime]P and in approximately complementary increases in YN and K[prime]N under normal and inhibitory conditions. The results were reproduced by a mathematical model of electron/proton transport and O2 evolution/...
Progress in Photosynthesis Research, 1987
Current Research in Photosynthesis, 1990
Photosynthesis research, 2003
By recording leaf transmittance at 820 nm and quantifying the photon flux density of far red ligh... more By recording leaf transmittance at 820 nm and quantifying the photon flux density of far red light (FRL) absorbed by long-wavelength chlorophylls of Photosystem I (PS I), the oxidation kinetics of electron carriers on the PS I donor side was mathematically analyzed in sunflower (Helianthus annuus L.), tobacco (Nicotiana tabacum L.) and birch (Betula pendula Roth.) leaves. PS I donor side carriers were first oxidized under FRL, electrons were then allowed to accumulate on the PS I donor side during dark intervals of increasing length. After each dark interval the electrons were removed (titrated) by FRL. The kinetics of the 820 nm signal during the oxidation of the PS I donor side was modeled assuming redox equilibrium among the PS I donor pigment (P700), plastocyanin (PC), and cytochrome f plus Rieske FeS (Cyt f + FeS) pools, considering that the 820 nm signal originates from P700(+) and PC(+). The analysis yielded the pool sizes of P700, PC and (Cyt f + FeS) and associated redox eq...
Proceedings of the Royal Society B: Biological Sciences, 1989
A mathematical model of the pentosephosphate carbon reduction (PCR) cycle is presented. The inter... more A mathematical model of the pentosephosphate carbon reduction (PCR) cycle is presented. The internal structure of the model is consistent with and complements the known biochemical pathways in the PCR cycle, together with starch and sucrose synthesis. Individual enzymes are described by maximum rate (V_m), standard free energy change (Delta G'_0) and Michaelis constant (K_m) values as parameters and rate-equations,
Planta, 1991
Oscillations in the rate of photosynthesis of sunflower (Helianthus annuus L.) leaves were induce... more Oscillations in the rate of photosynthesis of sunflower (Helianthus annuus L.) leaves were induced by subjecting leaves, whose photosynthetic apparatus had been activated, to a sudden transition from darkness or low light to high-intensity illumination, or by transfering them in the light from air to an atmosphere containing saturating CO2. It was found that at the first maximum, light-and CO2-saturated photosynthesis can be much faster than steady-state photosynthesis. Both QA in the reaction center of PS II and P700 in the reaction center of PS I of the chloroplast electron-transport chain were more oxidized during the maxima of photosynthesis than during the minima. Maxima of P700 oxidation slightly preceded maxima in photosynthesis. During a transition from low to high irradiance, the assimilatory force FA, which was calculated from ratios of dihydroxyacetone phosphate to phosphoglycerate under the assumption that the reactions catalyzed by NADP-dependent glyceraldehydephosphate dehydrogenase, phosphoglycerate kinase and triosephosphate isomerase are close to equilibrium, oscillated in parallel with photosynthesis. However, only one of its components, the calculated phosphorylation potential (ATP)/(ADP)(Pi), paralleled photosynthesis, whereas calculated NADPH/NADP ratios exhibited antiparallel behaviour. When photosynthetic oscillations were initiated by a transition from low to high CO2, the assimilatory force FA declined, was very low at the first minimum of photosynthesis and increased as photosynthesis rose to its second maximum. The observations indicate that the minima in photosynthesis are caused by lack of ATP. This leads to overreduction of the electron-transport chain which is indicated by the reduction of P700. During photosynthetic oscillations the chloroplast thylakoid system is unable to adjust the supply of ATP and NADPH rapidly to demand at the stoichiometric relationship required by the carbonreduction cycle.
Plant, Cell & Environment, 2012
Finite mesophyll diffusion conductance (gm) significantly constrains net assimilation rate (An), ... more Finite mesophyll diffusion conductance (gm) significantly constrains net assimilation rate (An), but gm variations and variation sources in response to environmental stresses during leaf development are imperfectly known. The combined effects of light and water limitations on gm and diffusion limitations of photosynthesis were studied in saplings of Populus tremula L. An one-dimensional diffusion model was used to gain insight into the importance of key anatomical traits in determining gm. Leaf development was associated with increases in dry mass per unit area, thickness, density, exposed mesophyll (Smes/S) and chloroplast (Sc/S) to leaf area ratio, internal air space (fias), cell wall thickness and chloroplast dimensions. Development of Smes/S and Sc/S was delayed under low light. Reduction in light availability was associated with lower Sc/S, but with larger fias and chloroplast thickness. Water stress reduced Sc/S and increased cell wall thickness under high light. In all treatments, gm and An increased and CO2 drawdown because of gm, Ci-Cc, decreased with increasing leaf age. Low light and drought resulted in reduced gm and An and increased Ci-Cc. These results emphasize the importance of gm and its components in determining An variations during leaf development and in response to stress.
Plant, Cell and Environment, 2002
Photosynthesis is a complex process whose rate is affected by many biochemical and biophysical fa... more Photosynthesis is a complex process whose rate is affected by many biochemical and biophysical factors. Fortunately, it is possible to determine, or at least estimate, many of the most important parameters using a combination of optical methods and gas transient analyses. We describe here a computer-operated routine that has been developed to make detailed assessments of photosynthesis at a comprehensive level. The routine comprised the following measurements: steady-state light and CO 2 response curves of net CO 2 assimilation at 21 and 2 kPa O 2 ; transients from limiting to different saturating CO 2 concentrations at 2 kPa O 2 ; post-illumination CO 2 fixation transient; dark-light induction of O 2 evolution; O 2 yield from one saturating single-turnover flash; chlorophyll fluorescence F 0 , F s and F m during the light and CO 2 response curves; leaf transmission at 820 nm (P700 + ) during the light and CO 2 response curves; post-illumination re-reduction time of P700 + . The routine was executed on a two-channel fast-response gas exchange measurement system (A. Laisk and V. Oja: Dynamic Gas Exchange of Leaf Photosynthesis. CSIRO, Canberra, Australia). Thirty-six intrinsic characteristics of the photosynthetic machinery were derived, including quantum yield of CO 2 fixation ( Y CO2 ), time constant of P700 re-reduction ( τ τ τ τ ′ ′ ′ ′ ), relative optical cross-sections of PSII and PSI antennae ( a II , a I ), PSII and PSI density per leaf area unit, plastoquinone pool, total mesophyll resistance, mesophyll diffusion resistance, V m , K m (CO 2 ) and CO 2 /O 2 specificity of Rubisco, RuBP pool at CO 2 limitation (assimilatory charge). An example of the routine and calculations are shown for one leaf and data are presented for leaves of 8-year-old-trees of two birch clones growing in Suonenjoki Forest Research Station, Finland, during summer 2000. Parameters Y CO2 , basic τ τ τ τ ′ ′ ′ ′ , a II , a I , K m (CO 2 ) and K s varied little in different leaves [relative standard deviation (RSD) < 7%], other parameters scattered widely (RSD typically 10-40%). It is concluded that the little scattered parameters are determined by basic physico-chemical properties of the photosynthetic machinery whereas the widely scattered parameters are adjusting to growth condi-
Plant, Cell and Environment, 2004
were grown in open-top chambers over 3 years (age 7-9 years). The treatments were increased CO 2 ... more were grown in open-top chambers over 3 years (age 7-9 years). The treatments were increased CO 2 concentration (+CO 2 , 72 Pa), increased O 3 concentration (+O 3 , 2 ¥ ¥ ¥ ¥ ambient O 3 with seasonal AOT40 up to 28 p.p.m. h) and in combination (+CO 2 + O 3 ). Thirty-seven photosynthetic parameters were measured in the laboratory immediately after excising leaves using a computer-operated routine of gas exchange and optical measurements. In control leaves the photosynthetic parameters were close to the values widely used in a model (Farquhar, von Caemmerer and Berry, Planta 149, 78-90, 1980). The distribution of chlorophyll between photosystem II and photosystem I, intrinsic quantum yield of electron transport, uncoupled turnover rate of Cyt b 6 f, Rubisco specificity and K m (CO 2 ) were not influenced by treatments. Net photosynthetic rate responded to +CO 2 with a mean increase of 17% in both clones. Dry weight of leaves increased, whereas protein, especially Rubisco content and the related photosynthetic parameters decreased. Averaged over 3 years, eight and 17 mechanistically independent parameters were significantly influenced by the elevated CO 2 in clones K1659 and V5952, respectively. The elevated O 3 caused a significant decrease in the average photosynthetic rate of clone V5952, but not of clone K1659. The treatment caused changes in one parameter of clone K1659 and in 11 parameters of clone V5952. Results of the combined treatment indicated that +O 3 had less effect in the presence of +CO 2 than alone. Interestingly, changes in the same photosynthetic parameters were observed in chamberless grown trees of clone V5952 as under +O 3 treatment in chambers, but this was not observed for clone K1659. These results suggest that during chronic fumigation, at concentrations below the threshold of visible leaf injuries, ozone influenced the photosynthetic parameters as a general stress factor, in a similar manner to weather conditions that were more stressful outside the chambers. According to this hypothesis, the sensitivity of a species or a clone to ozone is expected to depend on the growth conditions: the plant is less sensitive to ozone if the conditions are close to optimal and it is more sensitive to ozone under conditions of stress.
Plant, Cell and Environment, 2005
Plant Biology, 2004
The global modelling of photosynthesis is based on exact knowledge of the leaf photosynthetic mac... more The global modelling of photosynthesis is based on exact knowledge of the leaf photosynthetic machinery. The capacities of partial reactions of leaf photosynthesis develop at different rates, but it is not clear how the development of photoreactions and the Calvin cycle are co-ordinated. We investigated the development of foliar photosynthesis in the temperate deciduous tree Betula pendula Roth. using a unique integrated optical/gas exchange methodology that allows simultaneous estimation of photosystem I and II (PS I and PS II) densities per leaf area, interphotosystem electron transport activities, and ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) kinetic properties. We combined these measurements with in vitro determinations of Rubisco, soluble protein and chlorophyll contents. We observed a strong increase in leaf photosynthetic capacity in developing leaves per leaf area, as well as per dry mass, that was paralleled by accumulation of leaf Rubisco. Enhanced mesophyll conductance was the outcome of increased carboxylation capacity and increased CO 2 diffusion conductance. However, Rubisco was only partly activated in the leaves, according to in vivo measurements of Rubisco kinetics. The amount of active Rubisco increased in proportion with development of PS I, probably through a direct link between Rubisco activase and PS I electron transport. Since the kinetics for post-illumination P700 re-reduction did not change, the synthesis of cytochrome b 6 f complex was also proportional to PS I. The synthesis of PS II began later and continued for several days after reaching the full PS I activity, but leaf chlorophyll was shared equally between the photosystems. Due to this, the antenna of PS II was very large and not optimally organized, leading to greater losses of excitation and lower quantum yields in young leaves. We conclude that co-ordinated development of leaf photosynthesis is regulated at the level of PS I with subordinated changes in PS II content and Rubisco activation.
Plant and Cell Physiology, 2007
Measurements of 810 nm transmittance changes in leaves, simultaneously with Chl fluorescence, CO(... more Measurements of 810 nm transmittance changes in leaves, simultaneously with Chl fluorescence, CO(2) uptake and O(2) evolution, were carried out on potato (Solanum tuberosum L.) leaves with altered expression of plastidic NADP-dependent malate dehydrogenase. Electron transport rates were calculated: J(C) from the CO(2) uptake rate considering ribulose-1,5-bisphosphate (RuBP) carboxylation and oxygenation, J(O) from the O(2) evolution rate, J(F) from Chl fluorescence parameters and J(I) from the post-illumination re-reduction speed of PSI donors. In the absence of external O(2), J(O) equaled (1.005 +/- 0.003) J(C), independent of the transgenic treatment, light intensity and CO(2) concentration. This showed that nitrite and oxaloacetate reduction rates were very slow. The Mehler-type O(2) reduction was evaluated from the rate of electron accumulation at PSI after the O(2) concentration was decreased from 210 to 20 mmol mol(-1), and resulted in &amp;amp;amp;lt;1% of the linear flow. J(F) and J(I) did not differ from J(C) while photosynthesis was light-limited, but considerably exceeded J(C) at saturating light. Then, typically, J(F) = 1.2 J(C) and J(I) = 1.3 J(C), and J(F) -J(C) and J(I) -J(C) depended little on CO(2) and O(2) concentrations. The results showed that the alternative and cyclic electron flow necessary to compensate variations in the ATP/NADPH ratio were only a few percent of the linear flow. The data do not support the requirement of 14H(+)/3ATP by the chloroplast ATP synthase. We suggest that the fast PSI cyclic electron flow J(I) - J(C), as well as the fast J(F) - J(C) are energy-dissipating cycles around PSI and PSII at light saturation.
Plant and Cell Physiology, 2000
Parallel measurements of CO2 assimilation and 800 nm transmission were carried out on intact leav... more Parallel measurements of CO2 assimilation and 800 nm transmission were carried out on intact leaves of wild type and cytochrome b6/f deficient transgenic tobacco grown at different light intensities and temperatures, with the aim to diagnose rate-limiting processes in photosynthesis and investigate their adaptations to growth conditions. Maximum CO2- and light-saturated photosynthetic rate, mesophyll conductance, assimilatory charge and specific carboxylation efficiency were determined from CO2 fixation measurements and postillumination P700 rereduction time constant was measured from the transient of the 800 nm signal. Results show that growth conditions continue to modulate the expression of genes in transgenic plants, interfering with the antisense modulation, but under all environmental conditions the antisense treatment to decrease Cyt b6/f complexes ensured that the control of electron/proton transport rate by proton backpressure on the PSI donor side was stronger than the control by electron backpressure on the PSI acceptor side. Coordinated control of gene expression and enzyme activation ensures that different parts of the photosynthetic machinery--components of the electron transport chain, ribulose-1,5-bisphosphate carboxylase/oxygenase, enzymes of the sucrose and starch synthesis chains-are synthesized more or less proportionally under different environmental conditions and in case of mild genetic interference.
This paper is available online free of all access charges (see
Soviet Plant Physiology, 1990
Journal of Experimental Botany, 2009
Site turnover rate (k cat) of Rubisco was measured in intact leaves of different plants. Potato (... more Site turnover rate (k cat) of Rubisco was measured in intact leaves of different plants. Potato (Solanum tuberosum L.) and birch (Betula pendula Roth.) leaves were taken from field-growing plants. Sunflower (Helianthus annuus L.), wild type (wt), Rubisco-deficient (-RBC), FNR-deficient (-FNR), and Cyt b 6 f deficient (-CBF) transgenic tobacco (Nicotiana tabacum L.) were grown in a growth chamber. Rubisco protein was measured with quantitative SDS-PAGE and FNR protein content with quantitative immunoblotting. The Cyt b 6 f level was measured in planta by maximum electron transport rate and the photosystem I (PSI) content was assessed by titration with far-red light. The CO 2 response of Rubisco was measured in planta with a fast-response gas exchange system at maximum ribulose 1,5-bisphosphate concentration. Reaction site k cat was calculated from V m and Rubisco content. Biological variation of k cat was significant, ranging from 1.5 to 4 s 21 in wt, but was >6 s 21 at 23°C in-RBC leaves. The lowest k cat of 0.5 s 21 was measured in-FNR and-CBF plants containing sufficient Rubisco but having slow electron transport rates. Plotting k cat against PSI per Rubisco site resulted in a hyperbolic relationship where wt plants are on the initial slope. A model is suggested in which Rubisco Activase is converted into an active ATP-form on thylakoid membranes with the help of a factor related to electron transport. The activation of Rubisco is accompanied by the conversion of the ATP-form into an inactive ADP-form. The ATP and ADP forms of Activase shuttle between thylakoid membranes and stromally-located Rubisco. In normal wt plants the electron transport-related activation of Activase is rate-limiting, maintaining 50-70% Rubisco sites in the inactive state.
Plant and Cell Physiology, 2007
Measurements of 810 nm transmittance changes in leaves, simultaneously with Chl fluorescence, CO ... more Measurements of 810 nm transmittance changes in leaves, simultaneously with Chl fluorescence, CO 2 uptake and O 2 evolution, were carried out on potato (Solanum tuberosum L.) leaves with altered expression of plastidic NADP-dependent malate dehydrogenase. Electron transport rates were calculated: J C from the CO 2 uptake rate considering ribulose-1,5-bisphosphate (RuBP) carboxylation and oxygenation, J O from the O 2 evolution rate, J F from Chl fluorescence parameters and J I from the post-illumination re-reduction speed of PSI donors. In the absence of external O 2 , J O equaled (1.005 AE 0.003) J C , independent of the transgenic treatment, light intensity and CO 2 concentration. This showed that nitrite and oxaloacetate reduction rates were very slow. The Mehler-type O 2 reduction was evaluated from the rate of electron accumulation at PSI after the O 2 concentration was decreased from 210 to 20 mmol mol À1 , and resulted in 51% of the linear flow. J F and J I did not differ from J C while photosynthesis was light-limited, but considerably exceeded J C at saturating light. Then, typically, J F ¼ 1.2 J C and J I ¼ 1.3 J C , and J F ÀJ C and J I ÀJ C depended little on CO 2 and O 2 concentrations. The results showed that the alternative and cyclic electron flow necessary to compensate variations in the ATP/NADPH ratio were only a few percent of the linear flow. The data do not support the requirement of 14H þ /3ATP by the chloroplast ATP synthase. We suggest that the fast PSI cyclic electron flow J I À J C , as well as the fast J F À J C are energy-dissipating cycles around PSI and PSII at light saturation.
Plant physiology
Sunflower (Helianthus annuus L.), cotton (Gossypium hirsutum L.), tobacco (Nicotiana tabacum L.),... more Sunflower (Helianthus annuus L.), cotton (Gossypium hirsutum L.), tobacco (Nicotiana tabacum L.), sorghum (Sorghum bicolor Moench.), amaranth (Amaranthus cruentus L.), and cytochrome b6f complex-deficient transgenic tobacco leaves were used to test the response of plants exposed to differnt light intensities and CO2 concentrations before and after photoinhibition at 4000 [mu]mol photons m-2 s-1 and to thermoinhibition up to 45[deg]C. Quantum yields of photochemical and nonphotochemical excitation quenching (YP and YN) and the corresponding relative rate constants for excitation capture from the antenna-primary radical pair equilibrium system (k[prime]P and k[prime]N) were calculated from measured fluorescence parameters. The above treatments resulted in decreases in YP and K[prime]P and in approximately complementary increases in YN and K[prime]N under normal and inhibitory conditions. The results were reproduced by a mathematical model of electron/proton transport and O2 evolution/...
Plant physiology, 1994
CO2 uptake rate, chlorophyll fluorescence, and 830-nm absorbance were measured in wild-type (wt) ... more CO2 uptake rate, chlorophyll fluorescence, and 830-nm absorbance were measured in wild-type (wt) Nicotiana sylvestris (Speg. et Comes) and starchless mutant NS 458 leaves at different light intensities and CO2 concentrations. Initial slopes of the relationships between CO2 uptake and light and CO2 were similar, but the maximum rate at CO2 and light saturation was only 30% in the mutant compared with the wt. O2 enhancement of photosynthesis at CO2 and light saturation was relatively much greater in the mutant than in the wt. In 21% O2, the electron transport rate (ETR) calculated from fluorescence peaked near the beginning of the CO2 saturation of photosynthesis. With the further increase of CO2 concentration ETR remained nearly constant or declined a little in the wt but drastically declined in the mutant. Absorbance measurements at 830 nm indicated photosystem I acceptor side reduction in both plants at saturating CO2 and light. Assimilatory charge (postillumination CO2 uptake) mea...
Plant physiology, 1997
Sunflower (Helianthus annuus L.), cotton (Gossypium hirsutum L.), tobacco (Nicotiana tabacum L.),... more Sunflower (Helianthus annuus L.), cotton (Gossypium hirsutum L.), tobacco (Nicotiana tabacum L.), sorghum (Sorghum bicolor Moench.), amaranth (Amaranthus cruentus L.), and cytochrome b6f complex-deficient transgenic tobacco leaves were used to test the response of plants exposed to differnt light intensities and CO2 concentrations before and after photoinhibition at 4000 [mu]mol photons m-2 s-1 and to thermoinhibition up to 45[deg]C. Quantum yields of photochemical and nonphotochemical excitation quenching (YP and YN) and the corresponding relative rate constants for excitation capture from the antenna-primary radical pair equilibrium system (k[prime]P and k[prime]N) were calculated from measured fluorescence parameters. The above treatments resulted in decreases in YP and K[prime]P and in approximately complementary increases in YN and K[prime]N under normal and inhibitory conditions. The results were reproduced by a mathematical model of electron/proton transport and O2 evolution/...
Progress in Photosynthesis Research, 1987
Current Research in Photosynthesis, 1990
Photosynthesis research, 2003
By recording leaf transmittance at 820 nm and quantifying the photon flux density of far red ligh... more By recording leaf transmittance at 820 nm and quantifying the photon flux density of far red light (FRL) absorbed by long-wavelength chlorophylls of Photosystem I (PS I), the oxidation kinetics of electron carriers on the PS I donor side was mathematically analyzed in sunflower (Helianthus annuus L.), tobacco (Nicotiana tabacum L.) and birch (Betula pendula Roth.) leaves. PS I donor side carriers were first oxidized under FRL, electrons were then allowed to accumulate on the PS I donor side during dark intervals of increasing length. After each dark interval the electrons were removed (titrated) by FRL. The kinetics of the 820 nm signal during the oxidation of the PS I donor side was modeled assuming redox equilibrium among the PS I donor pigment (P700), plastocyanin (PC), and cytochrome f plus Rieske FeS (Cyt f + FeS) pools, considering that the 820 nm signal originates from P700(+) and PC(+). The analysis yielded the pool sizes of P700, PC and (Cyt f + FeS) and associated redox eq...
Proceedings of the Royal Society B: Biological Sciences, 1989
A mathematical model of the pentosephosphate carbon reduction (PCR) cycle is presented. The inter... more A mathematical model of the pentosephosphate carbon reduction (PCR) cycle is presented. The internal structure of the model is consistent with and complements the known biochemical pathways in the PCR cycle, together with starch and sucrose synthesis. Individual enzymes are described by maximum rate (V_m), standard free energy change (Delta G&amp;amp;amp;#39;_0) and Michaelis constant (K_m) values as parameters and rate-equations,
Planta, 1991
Oscillations in the rate of photosynthesis of sunflower (Helianthus annuus L.) leaves were induce... more Oscillations in the rate of photosynthesis of sunflower (Helianthus annuus L.) leaves were induced by subjecting leaves, whose photosynthetic apparatus had been activated, to a sudden transition from darkness or low light to high-intensity illumination, or by transfering them in the light from air to an atmosphere containing saturating CO2. It was found that at the first maximum, light-and CO2-saturated photosynthesis can be much faster than steady-state photosynthesis. Both QA in the reaction center of PS II and P700 in the reaction center of PS I of the chloroplast electron-transport chain were more oxidized during the maxima of photosynthesis than during the minima. Maxima of P700 oxidation slightly preceded maxima in photosynthesis. During a transition from low to high irradiance, the assimilatory force FA, which was calculated from ratios of dihydroxyacetone phosphate to phosphoglycerate under the assumption that the reactions catalyzed by NADP-dependent glyceraldehydephosphate dehydrogenase, phosphoglycerate kinase and triosephosphate isomerase are close to equilibrium, oscillated in parallel with photosynthesis. However, only one of its components, the calculated phosphorylation potential (ATP)/(ADP)(Pi), paralleled photosynthesis, whereas calculated NADPH/NADP ratios exhibited antiparallel behaviour. When photosynthetic oscillations were initiated by a transition from low to high CO2, the assimilatory force FA declined, was very low at the first minimum of photosynthesis and increased as photosynthesis rose to its second maximum. The observations indicate that the minima in photosynthesis are caused by lack of ATP. This leads to overreduction of the electron-transport chain which is indicated by the reduction of P700. During photosynthetic oscillations the chloroplast thylakoid system is unable to adjust the supply of ATP and NADPH rapidly to demand at the stoichiometric relationship required by the carbonreduction cycle.
Plant, Cell & Environment, 2012
Finite mesophyll diffusion conductance (gm) significantly constrains net assimilation rate (An), ... more Finite mesophyll diffusion conductance (gm) significantly constrains net assimilation rate (An), but gm variations and variation sources in response to environmental stresses during leaf development are imperfectly known. The combined effects of light and water limitations on gm and diffusion limitations of photosynthesis were studied in saplings of Populus tremula L. An one-dimensional diffusion model was used to gain insight into the importance of key anatomical traits in determining gm. Leaf development was associated with increases in dry mass per unit area, thickness, density, exposed mesophyll (Smes/S) and chloroplast (Sc/S) to leaf area ratio, internal air space (fias), cell wall thickness and chloroplast dimensions. Development of Smes/S and Sc/S was delayed under low light. Reduction in light availability was associated with lower Sc/S, but with larger fias and chloroplast thickness. Water stress reduced Sc/S and increased cell wall thickness under high light. In all treatments, gm and An increased and CO2 drawdown because of gm, Ci-Cc, decreased with increasing leaf age. Low light and drought resulted in reduced gm and An and increased Ci-Cc. These results emphasize the importance of gm and its components in determining An variations during leaf development and in response to stress.
Plant, Cell and Environment, 2002
Photosynthesis is a complex process whose rate is affected by many biochemical and biophysical fa... more Photosynthesis is a complex process whose rate is affected by many biochemical and biophysical factors. Fortunately, it is possible to determine, or at least estimate, many of the most important parameters using a combination of optical methods and gas transient analyses. We describe here a computer-operated routine that has been developed to make detailed assessments of photosynthesis at a comprehensive level. The routine comprised the following measurements: steady-state light and CO 2 response curves of net CO 2 assimilation at 21 and 2 kPa O 2 ; transients from limiting to different saturating CO 2 concentrations at 2 kPa O 2 ; post-illumination CO 2 fixation transient; dark-light induction of O 2 evolution; O 2 yield from one saturating single-turnover flash; chlorophyll fluorescence F 0 , F s and F m during the light and CO 2 response curves; leaf transmission at 820 nm (P700 + ) during the light and CO 2 response curves; post-illumination re-reduction time of P700 + . The routine was executed on a two-channel fast-response gas exchange measurement system (A. Laisk and V. Oja: Dynamic Gas Exchange of Leaf Photosynthesis. CSIRO, Canberra, Australia). Thirty-six intrinsic characteristics of the photosynthetic machinery were derived, including quantum yield of CO 2 fixation ( Y CO2 ), time constant of P700 re-reduction ( τ τ τ τ ′ ′ ′ ′ ), relative optical cross-sections of PSII and PSI antennae ( a II , a I ), PSII and PSI density per leaf area unit, plastoquinone pool, total mesophyll resistance, mesophyll diffusion resistance, V m , K m (CO 2 ) and CO 2 /O 2 specificity of Rubisco, RuBP pool at CO 2 limitation (assimilatory charge). An example of the routine and calculations are shown for one leaf and data are presented for leaves of 8-year-old-trees of two birch clones growing in Suonenjoki Forest Research Station, Finland, during summer 2000. Parameters Y CO2 , basic τ τ τ τ ′ ′ ′ ′ , a II , a I , K m (CO 2 ) and K s varied little in different leaves [relative standard deviation (RSD) < 7%], other parameters scattered widely (RSD typically 10-40%). It is concluded that the little scattered parameters are determined by basic physico-chemical properties of the photosynthetic machinery whereas the widely scattered parameters are adjusting to growth condi-
Plant, Cell and Environment, 2004
were grown in open-top chambers over 3 years (age 7-9 years). The treatments were increased CO 2 ... more were grown in open-top chambers over 3 years (age 7-9 years). The treatments were increased CO 2 concentration (+CO 2 , 72 Pa), increased O 3 concentration (+O 3 , 2 ¥ ¥ ¥ ¥ ambient O 3 with seasonal AOT40 up to 28 p.p.m. h) and in combination (+CO 2 + O 3 ). Thirty-seven photosynthetic parameters were measured in the laboratory immediately after excising leaves using a computer-operated routine of gas exchange and optical measurements. In control leaves the photosynthetic parameters were close to the values widely used in a model (Farquhar, von Caemmerer and Berry, Planta 149, 78-90, 1980). The distribution of chlorophyll between photosystem II and photosystem I, intrinsic quantum yield of electron transport, uncoupled turnover rate of Cyt b 6 f, Rubisco specificity and K m (CO 2 ) were not influenced by treatments. Net photosynthetic rate responded to +CO 2 with a mean increase of 17% in both clones. Dry weight of leaves increased, whereas protein, especially Rubisco content and the related photosynthetic parameters decreased. Averaged over 3 years, eight and 17 mechanistically independent parameters were significantly influenced by the elevated CO 2 in clones K1659 and V5952, respectively. The elevated O 3 caused a significant decrease in the average photosynthetic rate of clone V5952, but not of clone K1659. The treatment caused changes in one parameter of clone K1659 and in 11 parameters of clone V5952. Results of the combined treatment indicated that +O 3 had less effect in the presence of +CO 2 than alone. Interestingly, changes in the same photosynthetic parameters were observed in chamberless grown trees of clone V5952 as under +O 3 treatment in chambers, but this was not observed for clone K1659. These results suggest that during chronic fumigation, at concentrations below the threshold of visible leaf injuries, ozone influenced the photosynthetic parameters as a general stress factor, in a similar manner to weather conditions that were more stressful outside the chambers. According to this hypothesis, the sensitivity of a species or a clone to ozone is expected to depend on the growth conditions: the plant is less sensitive to ozone if the conditions are close to optimal and it is more sensitive to ozone under conditions of stress.
Plant, Cell and Environment, 2005
Plant Biology, 2004
The global modelling of photosynthesis is based on exact knowledge of the leaf photosynthetic mac... more The global modelling of photosynthesis is based on exact knowledge of the leaf photosynthetic machinery. The capacities of partial reactions of leaf photosynthesis develop at different rates, but it is not clear how the development of photoreactions and the Calvin cycle are co-ordinated. We investigated the development of foliar photosynthesis in the temperate deciduous tree Betula pendula Roth. using a unique integrated optical/gas exchange methodology that allows simultaneous estimation of photosystem I and II (PS I and PS II) densities per leaf area, interphotosystem electron transport activities, and ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) kinetic properties. We combined these measurements with in vitro determinations of Rubisco, soluble protein and chlorophyll contents. We observed a strong increase in leaf photosynthetic capacity in developing leaves per leaf area, as well as per dry mass, that was paralleled by accumulation of leaf Rubisco. Enhanced mesophyll conductance was the outcome of increased carboxylation capacity and increased CO 2 diffusion conductance. However, Rubisco was only partly activated in the leaves, according to in vivo measurements of Rubisco kinetics. The amount of active Rubisco increased in proportion with development of PS I, probably through a direct link between Rubisco activase and PS I electron transport. Since the kinetics for post-illumination P700 re-reduction did not change, the synthesis of cytochrome b 6 f complex was also proportional to PS I. The synthesis of PS II began later and continued for several days after reaching the full PS I activity, but leaf chlorophyll was shared equally between the photosystems. Due to this, the antenna of PS II was very large and not optimally organized, leading to greater losses of excitation and lower quantum yields in young leaves. We conclude that co-ordinated development of leaf photosynthesis is regulated at the level of PS I with subordinated changes in PS II content and Rubisco activation.
Plant and Cell Physiology, 2007
Measurements of 810 nm transmittance changes in leaves, simultaneously with Chl fluorescence, CO(... more Measurements of 810 nm transmittance changes in leaves, simultaneously with Chl fluorescence, CO(2) uptake and O(2) evolution, were carried out on potato (Solanum tuberosum L.) leaves with altered expression of plastidic NADP-dependent malate dehydrogenase. Electron transport rates were calculated: J(C) from the CO(2) uptake rate considering ribulose-1,5-bisphosphate (RuBP) carboxylation and oxygenation, J(O) from the O(2) evolution rate, J(F) from Chl fluorescence parameters and J(I) from the post-illumination re-reduction speed of PSI donors. In the absence of external O(2), J(O) equaled (1.005 +/- 0.003) J(C), independent of the transgenic treatment, light intensity and CO(2) concentration. This showed that nitrite and oxaloacetate reduction rates were very slow. The Mehler-type O(2) reduction was evaluated from the rate of electron accumulation at PSI after the O(2) concentration was decreased from 210 to 20 mmol mol(-1), and resulted in &amp;amp;amp;lt;1% of the linear flow. J(F) and J(I) did not differ from J(C) while photosynthesis was light-limited, but considerably exceeded J(C) at saturating light. Then, typically, J(F) = 1.2 J(C) and J(I) = 1.3 J(C), and J(F) -J(C) and J(I) -J(C) depended little on CO(2) and O(2) concentrations. The results showed that the alternative and cyclic electron flow necessary to compensate variations in the ATP/NADPH ratio were only a few percent of the linear flow. The data do not support the requirement of 14H(+)/3ATP by the chloroplast ATP synthase. We suggest that the fast PSI cyclic electron flow J(I) - J(C), as well as the fast J(F) - J(C) are energy-dissipating cycles around PSI and PSII at light saturation.
Plant and Cell Physiology, 2000
Parallel measurements of CO2 assimilation and 800 nm transmission were carried out on intact leav... more Parallel measurements of CO2 assimilation and 800 nm transmission were carried out on intact leaves of wild type and cytochrome b6/f deficient transgenic tobacco grown at different light intensities and temperatures, with the aim to diagnose rate-limiting processes in photosynthesis and investigate their adaptations to growth conditions. Maximum CO2- and light-saturated photosynthetic rate, mesophyll conductance, assimilatory charge and specific carboxylation efficiency were determined from CO2 fixation measurements and postillumination P700 rereduction time constant was measured from the transient of the 800 nm signal. Results show that growth conditions continue to modulate the expression of genes in transgenic plants, interfering with the antisense modulation, but under all environmental conditions the antisense treatment to decrease Cyt b6/f complexes ensured that the control of electron/proton transport rate by proton backpressure on the PSI donor side was stronger than the control by electron backpressure on the PSI acceptor side. Coordinated control of gene expression and enzyme activation ensures that different parts of the photosynthetic machinery--components of the electron transport chain, ribulose-1,5-bisphosphate carboxylase/oxygenase, enzymes of the sucrose and starch synthesis chains-are synthesized more or less proportionally under different environmental conditions and in case of mild genetic interference.