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At least 325 records · Page 18Linked to original sources
PubMed1992

CO(2) Enhancement of Growth and Photosynthesis in Rice (Oryza sativa) : Modification by Increased Ultraviolet-B Radiation.

Two cultivars of rice (Oryza sativa L.) IR-36 and Fujiyama-5 were grown at ambient (360 microbars) and elevated CO(2) (660 microbars) from germination through reproduction in unshaded greenhouses at the Duke University Phytotron. Growth at elevated CO(2) resulted in significant decreases in nighttime respiration and increases in photosynthesis, total biomass, and yield for both cultivars. However, in plants exposed to simultaneous increases in CO(2) and ultraviolet-B (UV-B) radiation, CO(2) enhancement effects on respiration, photosynthesis, and biomass were eliminated in IR-36 and significantly reduced in Fujiyama-5. UV-B radiation simulated a 25% depletion in stratospheric ozone at Durham, North Carolina. Analysis of the response of CO(2) uptake to internal CO(2) concentration at light saturation suggested that, for IR-36, the predominant limitation to photosynthesis with increased UV-B radiation was the capacity for regeneration of ribulose bisphosphate (RuBP), whereas for Fujiyama-5 the primary photosynthetic decrease appeared to be related to a decline in apparent carboxylation efficiency. Changes in the RuBP regeneration limitation in IR-36 were consistent with damage to the photochemical efficiency of photosystem II as estimated from the ratio of variable to maximum chlorophyll fluorescence. Little change in RuBP regeneration and photochemistry was evident in cultivar Fujiyama-5, however. The degree of sensitivity of photochemical reactions with increased UV-B radiation appeared to be related to leaf production of UV-B-absorbing compounds. Fujiyama-5 had a higher concentration of these compounds than IR-36 in all environments, and the production of these compounds in Fujiyama-5 was stimulated by UV-B fluence. Results from this study suggest that in rice alterations in growth or photosynthesis as a result of enhanced CO(2) may be eliminated or reduced if UV-B radiation continues to increase.

Journal Article↗
PubMed1999

Plastid translation is required for the expression of nuclear photosynthesis genes in the dark and in roots of the pea lip1 mutant

The expression of nuclear photosynthesis genes in pea seedlings requires both light and a postulated signal produced by developing plastids. The requirement for the plastid signal for the accumulation of transcripts of Lhcb1, RbcS, PetE, and AtpC genes was investigated in the pea mutant lip1, which shows light-independent photomorphogenic development. Lincomycin and erythromycin, inhibitors of plastid translation, decreased the accumulation of transcripts of nuclear photosynthesis genes in shoots of light-grown wild-type and lip1 seedlings, indicating that the plastid signal is required in the lip1 mutant. Treatment with lincomycin or erythromycin also reduced the accumulation of transcripts in shoots of dark-grown lip1 seedlings, indicating that light is not an obligate requirement for the synthesis or activity of the plastid signal. Lincomycin had a similar effect on the accumulation of Lhcb1 transcripts in dark-grown cop1-4 seedlings of Arabidopsis. Accumulation of transcripts of nuclear photosynthesis genes was also observed in roots of light-grown lip1 seedlings, and this accumulation, which was associated with the development of chloroplasts, was again dependent on plastid translation. The plastid signal therefore regulates the expression of nuclear photosynthesis genes in the dark and in roots of the lip1 mutant.

Journal Article↗
PubMed1954

Photosynthesis by protoplasm extruded from Chara and Nitella.

(a) Photosynthesis with protoplasm isolated from Chara or Nitella as measured by C(14) fixation has been obtained at a rate 12 to 15 per cent of that of the whole cells. (b) Photosynthesis by cut cells of Chara or Nitella with the vacuolar sap removed was at a rate comparable to that of the whole cells. (c) Both the protoplasm and the cut cells reduced CO(2) in the light to sucrose and hexose phosphates. Other products formed were also detected by paper chromatography. In contrast, dark controls fixed the C(14) into products associated with plant respiration. (d) An important difference in the products from the extruded protoplasm was the absence of C(14)-labelled pentoses or sedoheptulose which were formed, however, by the whole or cut cells. This suggests that the most sensitive site affected by disruption of the cells may be the steps involved in the regeneration of the "C-2 acceptor" for CO(2) fixation in photosynthesis.

Chara↗
PubMed1956

The effects of some inhibitors on the rates of photosynthesis and respiration by Chlorella.

The effects of several inhibitors on the rates of photosynthesis and of respiration by Chlorella pyrenoidosa have been studied. The inhibitors used in this study include potassium cyanide, hydroxylamine hydrogen chloride, dinitrophenol,and sodium azide. Each inhibitor seems to have its own characteristic action in photosynthesis and in respiration. With the exception of hydroxylamine, all the inhibitors show a stimulation of respiration at low concentrations of the inhibitors. Only dinitrophenol inhibits respiration to a marked extent. Potassium cyanide, hydroxylamine, and dinitrophenol are about equally effective in inhibiting photosynthesis, but sodium azide is nearly ten times as effective.

Cell Respiration↗
PubMed2005

The structure of photosystem I and evolution of photosynthesis.

Oxygenic photosynthesis is the principal producer of both oxygen and organic matter on earth. The primary step in this process--the conversion of sunlight into chemical energy--is driven by four multi-subunit membrane protein complexes named photosystem I, photosystem II, cytochrome b(6)f complex and F-ATPase. Photosystem I generates the most negative redox potential in nature and thus largely determines the global amount of enthalpy in living systems. The recent structural determination of PSI complexes from cyanobacteria and plants sheds light on the evolutionary forces that shaped oxygenic photosynthesis. The fortuitous formation of our solar system in a space plentiful of elements, our distance from the sun and the long time of uninterrupted evolution enabled the perfection of photosynthesis and the evolution of advanced organisms. The available structural information complements the knowledge gained from genomic and proteomic data to illustrate a more precise scenario for the evolution of life systems on earth.

Biological Evolution↗
PubMed1990

Expression of a yeast-derived invertase in the cell wall of tobacco and Arabidopsis plants leads to accumulation of carbohydrate and inhibition of photosynthesis and strongly influences growth and phenotype of transgenic tobacco plants.

Chimeric genes consisting of the coding sequence of the yeast invertase gene suc 2 and different N-terminal portions of the potato-derived vacuolar protein proteinase inhibitor II fused to the 35S CaMV promoter and the poly-A site of the octopine synthase gene were transferred into tobacco and Arabidopsis thaliana plants using Agrobacterium based systems. Regenerated transgenic plants display a 50- to 500-fold higher invertase activity compared to non-transformed control plants. This invertase is N-glycosylated and efficiently secreted from the plant cell leading to its apoplastic location. Whereas expression of the invertase does not lead to drastic changes in transgenic Arabidopsis thaliana plants, transgenic tobacco plants show dramatic changes with respect to development and phenotype. Expression of the invertase leads to stunted growth due to reduction of internodal distances, to development of bleached and/or necrotic regions in older leaves and to suppressed root formation. In mature leaves, high levels of soluble sugars and starch accumulate. These carbohydrates do not show a diurnal turnover. The accumulation of carbohydrate is accompanied by an inhibition of photosynthesis, and in tobacco, by an increase in the rate of respiration. Measurements in bleached versus green areas of the same leaf show that the bleached section contains high levels of carbohydrates and has lower photosynthesis and higher respiration than green sections. It is concluded that expression of invertase in the cell wall interrupts export and leads to an accumulation of carbohydrates and inhibition of photosynthesis.

Amino Acid Sequence↗
PubMed1990

Light-stimulated cell expansion in bean (Phaseolus vulgaris L.) leaves. I. Growth can occur without photosynthesis.

Cell expansion in dicotyledonous leaves is strongly stimulated by bright white light (WL), at least in part as a result of light-induced acidification of the cell walls. It has been proposed that photosynthetic reactions are required for light-stimulated transport processes across plasma membranes of leaf cells, including proton excretion. The involvement of photosynthesis in growth and wall acidification of primary leaves of bean has been tested by inhibiting photosynthesis in two ways: by reducing chlorophyll content of intact plants with tentoxin (TX) and by treating leaf discs with 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU). Exposure to bright WL stimulated growth of intact leaves of TX-treated plants. Discs excised from green as well as from TX-or DCMU-treated leaves also responded by growing faster in WL, as long as exogenous sucrose was supplied to the photosynthetically inhibited tissues. The WL caused acidification of the epidermal surface of intact TX-leaves, but acidification of the incubation medium by mesophyll cells only occurred when photosynthesis was not inhibited. It is concluded that light-stimulated cell enlargement of bean leaves, and the necessary acidification of epidermal cell walls, are mediated by a pigment other than chlorophyll. Light-induced proton excretion by mesophyll cells, on the other hand, may require both a photosynthetic product (or exogenous sugars) and a non-photosynthetic light effect.

Cell Division↗
PubMed1975

Effects of diazepam on photosynthesis, respiration, rubidium uptake, and finestructure of Scenedesmus obliquus in synchronous cultures.

Effects of diazepam (Valium) on photosynthesis, chlorophyll/photosynthesis ratios, respiration, uptake of rubidium ions, and ultrastructure of Scenedesmus obliquus synchronized by a light-dark regimen of 14:10 hrs were determined. 80 and 160 muM diazepam, added to the nutrient medium at the start of the light-dark change (i.e., start of the cell cycle) gradually reduced rates of photosynthesis, below the initial rates from the beginning of the experiment. Contents of chlorophyll, however, remained nearly unaffected. Consequently, the diazepam-treated cells had a higher chlorophyll/photosynthesis ratio--also with regard to respiration in order to calculate the gross photosynthesis. The occurrence of photorespiration cannot be assumed. The net influx of rubidium was slightly reduced by 100 muM diazepam 0.5 and 2.0 hrs after the start of the cell cycle and was strongly inhibited after 5 to 14 hrs. 80 and 160 muM diazepam caused separation of thylakoids, formation of giant mitochondria and enlargement of vacuoles.

Adenosine Triphosphate↗
PubMed2001

Effects of pH on the growth rate, motility and photosynthesis in Euglena gracilis.

The influence of pH 3-10 on the growth, motility and photosynthesis in Euglena gracilis was demonstrated during a 7-d cultivation. The cells did not survive at pH < 4 and > 8, highest growth rate being detected at pH 7. Motility followed a similar pattern as growth rate. Photosynthetic response curves were shown to be of the same type over the whole pH range. High respiration was characteristic for cells grown at pH 5 and 6, the lowest one at 7. At high and also at low pH more active respiration was found which can be considered as a protective response on proton stress. Respiration was not completely inhibited with potassium cyanide. Photosynthesis was the most effective at pH 6; lower and higher pH decreased photosynthetic efficiency. pH affected more the growth rate than the photosynthesis.

Animals↗
PubMed2004

Characteristics of photosynthesis in rice plants transformed with an antisense Rubisco activase gene.

Transgenic rice plants with an antisense gene inserted via Agrobacterium tumefaciens were used to explore the impact of the reduction of Rubisco activase (RCA) on Rubisco and photosynthesis. In this study, transformants containing 15% to 35% wild type Rubisco activase were selected, which could survive in ambient CO2 concentration but grew slowly compared with wild type controls. Gas exchange measurements indicated that the rate of photosynthesis decreased significantly, while stomatal conductance and transpiration rate did not change; and that the intercellular CO2 concentration even increased. Rubisco determination showed that these plants had approximately twice as much Rubisco as the wild types, although they showed 70% lower rate of photosynthesis, which was likely an acclimation response to the reduction in Rubsico activase and/or the reduction in carbamylation.

Antisense Elements (Genetics)↗
PubMed2004

The effect of anthracene and phenanthrene on the growth, photosynthesis, and SOD activity of the green alga Scenedesmus armatus depends on the PAR irradiance and CO2 level.

Short-term (24-h) experiments were performed to examine the effect of phenanthrene (PHE) and anthracene (ANT) on algae grown in a batch culture system at irradiances of 12, 33, 48, and 64 W m(-2) of the PAR range. Cultures were aerated (0.1 or 2% CO(2)) or nonaerated. As a result of aeration the concentration of ANT dropped from 0.45 mg L(-1) at the beginning of the experiment (t(0)) to an undetectable value after 10 h. The PHE concentration dropped from 9.36 mg L(-1) at t0 to 0.17 mg L(-1) after 24 h. ANT at nominal concentrations exceeding 0.05 mg L(-1) inhibited the growth of the algae in a concentration- and irradiance-dependent manner. The algistatic effect of ANT observed at 64 and 48 W m(-2) was independent of the CO(2) level, whereas the growth inhibition at 33 and 12 W m(-2) was much greater in cultures aerated with 2% than with 0.1% CO(2). PHE inhibited the growth only at a concentration of 10 mg L(-1) (about 50% of the control) regardless of the irradiance or the CO(2) concentration. The toxicity of both PHE and ANT was similar in aerated (0.1% CO(2)) and nonaerated cultures. ANT and PHE had a distinct effect on the photosynthesis. At 0.1% CO(2), the irradiance-dependent inhibition (ANT) and stimulation (PHE) of the photosynthesis was observed. The inhibitory effect of ANT was enhanced when algae were grown at 2% CO(2), but at the same CO(2) concentration PHE did not affect the photosynthesis. ANT stimulated the total superoxide dismutase (SOD) activity in the cells, this effect being generally more pronounced at elevated CO(2) levels and increasing with the irradiance. The total SOD activity was 250-300% higher in cells treated with PHE aerated with 0.1% CO(2). At 2% CO(2) no effect of PHE on the enzyme's activity was noted. The results obtained indicate that ANT acts as a photosensitizer causing an oxidative damage of cells, while PHE seems to affect the macromolecular synthesis.

Anthracenes↗
PubMed2002

Effect of oxygen concentration on photosynthesis and respiration in two hypersaline microbial mats.

The effects of oxygen concentration on photosynthesis and respiration in two hypersaline cyanobacterial mats were investigated. Experiments were carried out on mats from Eilat, Israel, with moderate photosynthetic activity, and mats from Mallorca, Spain, with high photosynthetic activity. The oxygen concentration in the overlying water above the mats was increased stepwise from 0% to 100% O2. Subsequent changes in oxygen concentration, gross photosynthetic rates, and pH values inside the mats were measured with microelectrodes. According to published reports on the regulation of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), the key enzyme in the CO2-fixation pathway of phototrophs, we expected photosynthetic activity to decrease with increasing oxygen concentration. Gross photosynthetic and total respiration rates in both mats were highest when the O2 concentration was at 0% in the overlying water. Net oxygen production rates under these conditions were the same as under air saturation (21% O2), while gross photosynthetic and respiration rates were lowest at air saturation. In both mats, gross photosynthetic and respiration rates increased upon gradually increasing the oxygen concentration in the overlying water from 21% to 100%. These results contradict the expectation that photosynthesis decreases with increasing oxygen concentration. Increased photosynthetic rates at oxygen concentrations above 21% were probably caused by enhanced oxidation of organic matter and concomitant CO2 production due to the increased oxygen availability. The cause of the high respiration rates at 0% O2 in the overlying water was presumably the enhanced excretion of photosynthetic products during increased photosynthesis. We conclude that the effect of the O2/CO2 concentration ratio on the activity of Rubisco as demonstrated in vitro on enzyme extracts cannot be extrapolated to the situation in intact microbial mats, because the close coupling of the activity of primary producers and heterotrophic bacteria plays a major role in this ecosystem.

Algorithms↗
PubMed2005

Irradiance regulation of photosynthesis and respiration in modern marine microbialites built by benthic cyanobacteria in a tropical lagoon (New Caledonia).

Microbialites are organosedimentary deposits that have built up as a result of the growth and binding of detrital sediment by a benthic microbial community. This study focuses on microbialites built by monospecific populations of cyanobacteria in the south-west lagoon of New Caledonia, where they have been observed down to 20-25 m depth. The aim was to study their photosynthetic and respiratory responses to various light intensities. The Phormidium sp. TK1 microbialite was collected at 19 m depth and the P. crosbyanum (Tilden) microbialite was collected at 0.5 and 13 m depth. Phormidium sp. TK1 showed all the characteristic features of a low-light adapted species. The initial slope of the Photosynthesis versus Irradiance curve for this microbialite was close to the maximum quantum yield indicating an efficient light absorption and utilization at low light. The photosynthesis maximum was located 0.2-0.4 mm below the surface and did not shift with changing light intensity. Respiration rates were low and not enhanced by light; photoinhibition was observed at higher light intensities. In Phormidium crosbyanum (Tilden) microbialites, the photosynthesis maximum shifted downward to lower depths with increasing light, probably as a result of phototactic migration of cyanobacterial filaments, and light-enhanced respiration was observed at light intensities above light saturation. The photosynthetic para- meters measured in P. crosbyanum indicate that P. crosbyanum is capable of photo-acclimation at high light intensities. The gross productivity of the different microbialites was comparable to values measured in cyanobacterial stromatolites observed in other shallow environments. However, the microbialites studied here were characterized by a lower respiration / production ratio which indicates a higher growth efficiency.

Chromatography, High Pressure Liquid↗
PubMed1997

Solute accumulation and decreased photosynthesis in leaves of potato plants expressing yeast-derived invertase either in the apoplast, vacuole or cytosol.

Potato (Solanum tuberosum cv. Désirée) plants expressing yeast invertase directed either to the apoplast, vacuole or cytosol were biochemically and physiologically characterised. All lines of transgenic plants showed similarities to plants growing under water stress. Transformants were retarded in growth, and accumulated hexoses and amino acids, especially proline, to levels up to 40-fold higher than those of the wild types. In all transformants rates of CO2 assimilation and leaf conductance were reduced. From the unchanged intercellular partial pressure of CO2 and apoplastic cis-abscisic acid (ABA) content of transformed leaves it was concluded that the reduced rate of CO2 assimilation was not caused by a limitation in the availability of CO2 for the ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco). In the transformants the amount of Rubisco protein was not reduced, but both activation state and carboxylation efficiency of photosynthesis were lowered. In vacuolar and cytosolic transformants this inhibition of Rubisco might be caused by a changed ratio of organic bound and inorganic phosphate, as indicated by a doubling of phosphorylated intermediates. But in apoplastic transformants the pattern of phosphorylated intermediates resembled that of leaves of water-stressed potato plants, although the cause of inhibition of photosynthesis was not identical. Whereas in water-stressed plants increased contents of the phytohormone ABA are supposed to mediate the adaptation to water stress, no contribution of ABA to reduction of photosynthesis could be detected in invertase transformants.

Abscisic Acid↗
PubMed2005

Photosynthesis in dynamic light: systems biology of unconventional chlorophyll fluorescence transients in Synechocystis sp. PCC 6803.

Photosynthetic organisms live in a dynamic environment where light typically fluctuates around a mean level that is slowly drifting during the solar day. We show that the far-from-equilibrium photosynthesis occurring in a rapidly fluctuating light differs vastly from the stationary-flux photosynthesis attained in a constant or slowly drifting light. Photosynthetic organisms in a static or slowly drifting light can be characterized by a steady-state quantum yield of chlorophyll fluorescence emission F' that is changing linearly with small and slow variations of the incident irradiance I+DeltaI(t): F'(I+DeltaI(t)) approximately Fmean '(dF)/(dI).DeltaI(t). In Synechocystis sp. PCC 6803, the linear approximation holds for an extended interval covering largely the static irradiance range experienced by the cyanobacteria in nature. The photosynthetic dynamism and, consequently, the dynamism of the chlorophyll fluorescence emission change dramatically when exposing the organism to a fluctuating irradiance. Harmonically-modulated irradiance I+DeltaI . sin(2pit/T), T approximately 1-25 s induces perpetual, far-from-equilibrium forced oscillations that are strongly non-linear, exhibiting significant hysteresis with multiple fluorescence levels corresponding to a single instantaneous level of the incident irradiance. We propose that, in nature, the far-from-equilibrium dynamic phenomena represent a significant correction to the steady-state photosynthetic activity that is typically investigated in laboratory. Analysis of the forced oscillations by the tools of systems biology suggests that the dynamism of photosynthesis observed in fluctuating light can be explained by a delayed action of regulatory agents.

Chlorophyll↗
PubMed2006

Celebrating 20 years of historical papers in Photosynthesis Research.

This editorial has four goals: (1) to inform the readers of 'Photosynthesis Research' about the past of the 'Historical corner'; which began 20 years ago; (2) to encourage photosynthesis researchers and historians of science to contact me for publishing papers of historical interest; these include: (a) Obituaries and Tributes; (b) historical papers on current and past discoveries and controversies; (c) history of research in specific laboratories, or in specific countries, or at specific conferences; (d) Personal perspectives (not discussed any further); (3) to encourage researchers not to discard, but to save correspondence and data of their discoveries for the future historians by donating them to their Archives, when appropriate (not discussed any further); and (4) to reinforce to the readers that the concept of two-light reaction and two-pigment system was already there in 1959. I mention here three key papers presented at the IXth International Botanical Congress, held at Montreal Canada (in August, 1959) prior to the famous April 9, 1960 paper by Robert Hill and Fay Bendall on the 'Z-scheme' of photosynthesis, that was based on thermodynamic and energetic considerations.

History, 20th Century↗
PubMed2006

Expression of foreign type I ribulose-1,5-bisphosphate carboxylase/ oxygenase (EC 4.1.1.39) stimulates photosynthesis in cyanobacterium Synechococcus PCC7942 cells.

A reporter gene assay revealed that promoters derived from Synechococcus PCC7942 (S.7942) psbAI and Synechocystis PCC6803 (S.6803) psbAII were suitable for the expression of foreign ribulose-bisphosphate carboxylase (RuBisCO; EC 4.1.1.39) in S.7942 cells. Transformational vectors with a promoter and a foreign RuBisCO gene, cvrbc originated from Allochromatium vinosum, were constructed on a binary vector, pUC303, and introduced to S.7942 cells. When the cvrbc was expressed with the S.7942 psbAI promoter, the total RuBisCO activity increased 2.5- to 4-fold than that of the wild type cell. The S.6803 psbAII promoter increased the activity of the transformant 1.5-2 times of that of wild type cell. There was a significant increase in the rate of photosynthesis depending on the increase of RuBisCO activity. The maximum rate of photosynthesis of the transformant cell was 1.63 times higher than that of the wild type under the illumination of 400 micromol m(-2) s(-1), at 20 mM bicarbonate and at 30 degrees C. Although the photosynthesis of the higher plant is limited by the ability of photosystems under high irradiance and the high CO(2 )concentration, that of the S.7942 cell is limited by the RuBisCO activity, even at high CO(2) concentrations and under high irradiance.

Gene Expression↗
PubMed2006

Photosynthesis research in Italy: a review.

This historical review was compiled and edited by Giorgio Forti, whereas the other authors of the different sections are listed alphabetically after his name, below the title of the paper; they are also listed in the individual sections. This review deals with the research on photosynthesis performed in several Italian laboratories during the last 50 years; it includes research done, in collaboration, at several international laboratories, particularly USA, UK, Switzerland, Hungary, Germany, France, Finland, Denmark, and Austria. Wherever pertinent, references are provided, especially to other historical papers in Govindjee et al. [Govindjee, Beatty JT, Gest H, Allen JF (eds) (2005) Discoveries in Photosynthesis. Springer, Dordrecht]. This paper covers the physical and chemical events starting with the absorption of a quantum of light by a pigment molecule to the conversion of the radiation energy into the stable chemical forms of the reducing power and of ATP. It describes the work done on the structure, function and regulation of the photosynthetic apparatus in higher plants, unicellular algae and in photosynthetic bacteria. Phenomena such as photoinhibition and the protection from it are also included. Research in biophysics of photosynthesis in Padova (Italy) is discussed by G.M. Giacometti and G. Giacometti (2006).

Biochemistry↗