| 1. |
- Dahlin, Clas
(författare)
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Surface charge densities and membrane fluidities in thylakoids with different degrees of thylakoid appression after Norflurazon treatment
- 2003
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Ingår i: Photosynthetica (Praha). - : Springer-Verlag. - 0300-3604 .- 1573-9058. ; 41:4, s. 635-639
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Tidskriftsartikel (refereegranskat)abstract
- Wheat seedlings (Triticum aestivum L.) develop plastids (etioplasts and chloroplasts) which exhibit alterations in inner membrane organisation after treatment with Norflurazon (NF), an inhibitor of carotenoid biosynthesis. In dark-grown plants, results in a decreased amount of partitions (contact zones) between prothylakoids. In weak red light, the results in plants containing chloroplasts devoid of grana. Assays have been performed to investigate the membrane surface charge density in these membranes, and relate possible differences to the absence of (pro-)thylakoid overlap after NF teatment. Using the fluorescent probe 9- amino acridine (9-AA), the average surface charge density of isolated PTs was -21.8±3.2 mC m-2 and - 27.4±2.6 mC m-2 in the control and after, respectively. Thylakoid membranes isolated from plants grown in weak red light exhibited slightly more negative values, -23.5±2.9 mC m-2 and -29.0±2.1 mC m-2, in control and after, respectively. The surface charge density of destacked thylakoids from greenhouse-grown untreated plants, containing extensive grana stacking, was -34.3±2.5 mC m-2. Assays using the fluorescent probe of DPH (1,6- diphenyl- 1,3,5- hexatriene) showed that this probe exhibits a higher polarisation value when incorporated into thylakoids from NF- treated plants compared to untreated plants grown in weak red light. The highest polarisation value was found in untreated plants grown in the greenhouse. This indicates a lower rotation transition of the probe in the lipid environment of thylakoids after NF treatment, which can be interpreted as more rigid membranes. These results suggest that the surface charge density and the mobility of membrane components may play a major role for the formation of partitions in dark-grown plants and in the formation of grana in plants grown in weak red light. 23 Additional key words: chloroplasts; etioplasts; (pro-)thylakoids; Triticum; stacking; wheat; 9- amino acridine.
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| 2. |
- Amirjani, M.R., et al.
(författare)
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Red region excitation spectra of protochlorophyllide in dark-grown leaves from plant species with different proportions of its spectral forms
- 2005
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Ingår i: Photosynthetica. - : Institute of Experimental Botany. - 0300-3604 .- 1573-9058. ; 44:1, s. 83-92
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Tidskriftsartikel (refereegranskat)abstract
- Etiolated leaves of three different species, maize, wheat, and pea, as well as a pea mutant (lip1) were used to compare the excitation spectra of protochlorophyllide (Pchlide) in the red region. The species used have different composition of short-wavelength and long-wavelength Pchlide forms. The relation between different forms was furthermore changed through incubating the leaves in 5-aminolevulinic acid (ALA), which caused an accumulation of short-wavelength Pchlide forms, as shown by changes in absorption and fluorescence spectra. This is the first time a comprehensive comparison is made between excitation spectra from different species covering an emission wavelength range of 675–750 nm using fluorescence equipment with electronic compensation for the variations in excitation irradiance. The different forms of Pchlide having excitations peaks at 628, 632, 637, 650, and 672 nm could be best measured at 675, 700, 710, 725, and 750 nm, respectively. Measuring emission at wavelengths between 675– 710 nm gave an exaggeration of the short-wavelength forms and measuring at longer wavelengths gave for the pea leaves an exaggeration of the 672 nm peak. In general, an energy transfer from short-wavelength Pchlide forms to long-wavelength Pchlide forms occurred, but such an energy transfer sometimes seemed to be limited as a result of a discrete location of the Pchlide spectral forms. The excitation spectra resembling the absorption spectrum most were measured at an emission wavelength of 740 nm. Measuring the excitation at 710 nm gave higher intensity of the spectra but the short-wavelength forms were accentuated.
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| 3. |
- Borisov, A. Y., et al.
(författare)
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On oxygen production by photosynthesis : A viewpoint
- 2018
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Ingår i: Photosynthetica. - : Institute of Experimental Botany. - 0300-3604 .- 1573-9058. ; 56:1, s. 44-47
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Tidskriftsartikel (refereegranskat)abstract
- In this brief communication we provide an estimate of the part of the incident solar energy used for oxygen evolution as well as the time, in years, needed for the generation of the present amount of molecular oxygen in the biosphere by photosynthesis on land and in the ocean. We find this to be ≈4,000 yr. We also find that the ocean produces 22% more oxygen than the land surface.
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| 4. |
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| 5. |
- Nonomura, Arthur M., et al.
(författare)
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The carbon reactions of photosynthesis : role of lectins and glycoregulation
- 2020
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Ingår i: Photosynthetica (Praha). - Prague : Institute of Experimental Botany of the Academy of Sciences of the Czech Republic. - 0300-3604 .- 1573-9058. ; 58:5, s. 1090-1097
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Forskningsöversikt (refereegranskat)abstract
- Modulation of glycoregulation in agriculture is reviewed here with emphasis on the elucidation of previously unknown pathways involving vacuolar lectins as well as a bypass of lectins that direct free sugars toward productivity. The reversible binding sequences of the endogenous lectin cycle are compared to an induced lectin bypass, as follows. (1) In the cycle, carbohydrate ligands, with similar binding specificities that compete for binding sites on lectins, are involved in the natural cycle of sugar exchanges. (2) For the bypass, tightly bound ligands that occupy lectins prevent free sugars from binding, making them available for productivity. This bypass is induced by methyl-α-D-mannopyranoside, a biochemical plant growth regulator for photosynthesis. Integration of this novel technology, with structural elements crucial for ligand binding by the lectins and with nitrogen assimilation, provides the basis for successful modulation of glycoregulation in crops for enhancement of quality and quantity.
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| 6. |
- Novriyanti, E., et al.
(författare)
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Photosynthetic nitrogen- and water-use efficiency of acacia and eucalypt seedlings as afforestation species
- 2012
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Ingår i: Photosynthetica (Praha). - : Institute of Experimental Botany. - 0300-3604 .- 1573-9058. ; 50:2, s. 273-281
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Tidskriftsartikel (refereegranskat)abstract
- The ecophysiological traits of acacia and eucalypt are important in assessing their suitability for afforestation. We measured the gas-exchange rate, the leaf dry mass per area (LMA) and the leaf nitrogen content of two acacia and four eucalypt species. Relative to the eucalypts, the acacias had lower leaf net photosynthetic rate (P-N), lower photosynthetic nitrogen-use efficiency (PNUE), higher water-use efficiency (WUE), higher LMA and higher leaf nitrogen per unit area (N-area). No clear differences were observed within or between genera in the maximum rate of carboxylation (V-cmax) or the maximum rate of electron transport (J(max)), although these parameters tended to be higher in eucalypts. PNUE and LMA were negatively correlated. We conclude that acacias with higher LMA do not allocate nitrogen efficiently to photosynthetic system, explaining why their P-N and PNUE were lower than in eucalypts.
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| 7. |
- Sundqvist, Christer, et al.
(författare)
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Obituary: Prof. Dr. Hemming Virgin
- 2008
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Ingår i: Photosynthetica. - : Institute of Experimental Botany. - 0300-3604 .- 1573-9058. ; 46:1, s. 1-2
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Hemming Ivar Virgin (1918-2005) was a pioneer in plant photobiology.The main topics of his research covered areas such as light effects on viscosity of protoplasm, determination of turgor and elasticity of plant organs, chlorophyll formation and accumulation, plastid development during greening, and phytochrome regulation of physiological processes.
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| 8. |
- Tikhonov, K., et al.
(författare)
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Quantification of bound bicarbonate in photosystem II
- 2018
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Ingår i: Photosynthetica (Praha). - : Institute of Experimental Botany. - 0300-3604 .- 1573-9058. ; 56:1, s. 210-216
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we presented a new approach for quantification of bicarbonate (HCO3-) molecules bound to PSII. Our method, which is based on a combination of membrane-inlet mass spectrometry (MIMS) and O-18-labelling, excludes the possibility of "non-accounted" HCO3- by avoiding (1) the employment of formate for removal of HCO3- from PSII, and (2) the extremely low concentrations of HCO3-/CO2 during online MIMS measurements. By equilibration of PSII sample to ambient CO2 concentration of dissolved CO2/HCO3-, the method ensures that all physiological binding sites are saturated before analysis. With this approach, we determined that in spinach PSII membrane fragments 1.1 +/- 0.1 HCO3- are bound per PSII reaction center, while none was bound to isolated PsbO protein. Our present results confirmed that PSII binds one HCO3- molecule as ligand to the non-heme iron of PSII, while unbound HCO3- optimizes the water-splitting reactions by acting as a mobile proton shuttle.
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| 9. |
- Tikhonov, K., et al.
(författare)
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Quantification of bound bicarbonate in photosystem II#
- 2018
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Ingår i: Photosynthetica (Praha). - : Springer. - 0300-3604 .- 1573-9058. ; 56:1, s. 210-216
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we presented a new approach for quantification of bicarbonate (HCO3-) molecules bound to PSII. Our method, which is based on a combination of membrane-inlet mass spectrometry (MIMS) and O-18-labelling, excludes the possibility of "non-accounted" HCO3- by avoiding (1) the employment of formate for removal of HCO3- from PSII, and (2) the extremely low concentrations of HCO3-/CO2 during online MIMS measurements. By equilibration of PSII sample to ambient CO2 concentration of dissolved CO2/HCO3-, the method ensures that all physiological binding sites are saturated before analysis. With this approach, we determined that in spinach PSII membrane fragments 1.1 +/- 0.1 HCO3- are bound per PSII reaction center, while none was bound to isolated PsbO protein. Our present results confirmed that PSII binds one HCO3- molecule as ligand to the non-heme iron of PSII, while unbound HCO3- optimizes the water-splitting reactions by acting as a mobile proton shuttle.
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| 10. |
- Voitsekhovskaja, O. V., et al.
(författare)
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Photosynthetic activity as assessed via chlorophyll a fluorescence suggests a role of potassium channels in root to shoot signaling
- 2020
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Ingår i: Photosynthetica (Praha). - : Institute of Experimental Botany. - 0300-3604 .- 1573-9058. ; 58:2, s. 608-621
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Tidskriftsartikel (refereegranskat)abstract
- Potassium is indispensable for plant growth. Recently, a role of K+ channels has emerged in sensing and transducing stress and nutrient status. Tetraethylammonium (TEA(+)) is a specific blocker of K+ transport and affects K+ channel gene expression. Two barley varieties with contrasting salinity tolerance, and a chlorophyll b-less mutant, were grown either in the presence of TEA(+) alone or combined with NaCl, at two different concentrations of external K+ and Ca2+, and were analyzed nine days after germination. Chlorophyll a transients monitored via JIP-tests were used to evaluate the state of the photosynthetic machinery. In contrast to reported responses to K+ deficiency, TEA(+) inhibited shoot growth while inducing root growth and increasing photosynthetic performance. Both TEA(+) and NaCl induced the appearance of negative K-bands in OJIP kinetics and an increase in PIABS, indicating a stimulation of photosynthesis by increased sink strength in the context of root to shoot signaling.
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