Photosynthesis, quenching of chlorophyll fluorescence and thermal energy dissipation in iron-deficient sugar beet leaves

1998 ◽  
Vol 25 (4) ◽  
pp. 403 ◽  
Author(s):  
Fermín Morales ◽  
Anunciación Abadía ◽  
Javier Abadía
Keyword(s):  
Energy Dissipation ◽  
Iron Deficiency ◽  
Photosystem Ii ◽  
Sugar Beet ◽  
Electron Flow ◽  
Reaction Centers ◽  
O2 Evolution ◽  
Photosystem Ii Efficiency ◽  
Iron Deficient ◽  
Additional Support

In sugar beet (Beta vulgaris L.) iron deficiency decreased not only the photosynthetic rate but also the actual photosystem II efficiency at steady-state photosynthesis. In moderate iron deficiency, the decrease in actual photosystem II efficiency under illumination was related to closure of photosystem II reaction centers, whereas in severe iron deficiency it was associated to decreases of intrinsic photosystem II efficiency. The O2 evolution, on an absorbed light basis, decreased more than the actual photosystem II efficiency, suggesting the presence of a significant fraction of electron transport to molecular oxygen or the existence of some form of cyclic electron flow. Iron-deficient leaves reduced the excess of light absorbed that cannot be used in photosynthesis not only by decreasing absorptance, but also by dissipating a large part of the light absorbed by the photosystem II antenna. This mechanism, that protects the photosystem II reaction centers through the enhancement of energy dissipation, was related to the de-epoxidation of violaxanthin (V) to antheraxanthin (A) and zeaxanthin (Z) in iron-deficient leaves. These data provide additional support for a role of Z+A in photoprotection under conditions of excess photosynthetic light absorption.

Mangrove Photosynthesis: Response to High-Irradiance Stress

1988 ◽  
Vol 15 (2) ◽  
pp. 43 ◽  
Author(s):  
O Bjorkman ◽  
B Demmig ◽  
TJ Andrews
Keyword(s):  
Energy Dissipation ◽  
Photosystem Ii ◽  
Energy Conversion ◽  
O2 Evolution ◽  
Photon Yield ◽  
Mangrove Species ◽  
Reaction Centres ◽  
Fluorescence Characteristics ◽  
Shade Leaves ◽  
Sun Leaves

Efficiencies of photosynthetic energy conversion were determined in sun and shade leaves of several mangrove species, growing in an open intertidal habitat in North Queensland, by measuring the maximum photon yield of O2 evolution and 77K chlorophyll fluorescence characteristics. Preliminary meas- urements confirmed that mangrove leaves have low water potentials, low stomatal conductances and low light-saturated CO2 exchange rates. Mangrove sun leaves therefore received a very large excess of excitation energy. Mangrove shade leaves had as high a photon yield of O2 evolution as non-mangrove leaves and their fluorescence characteristics were normal, showing that the energy conversion efficiency was unaffected by the high salinity. Mangrove sun leaves had markedly depressed photon yields and fluorescence was severely quenched showing that the efficiency of the photochemistry of photosystem II was reduced. The efficiency of energy conversion decreased with an increased radiation receipt. No such depression was detected in sun leaves of non-mangrove species growing in adjacent non-saline sites. Shading of man- grove sun leaves resulted in an increase in the efficiency of energy conversion but, in most species, more than 1 week was required for these leaves to reach the efficiency of shade leaves. Leaves exposed to direct sunlight had somewhat higher efficiencies in mangrove plants cultivated in 10% seawater as compared with full-strength seawater but the salinity of the culture solution had little effect on the increase in the efficiency upon shading. Field and laboratory fluorescence measurements indicated that the reduced efficiency of energy conversion in mangrove sun leaves resulted from a large increase in the rate constant for radiationless energy dissipation in the antenna chlorophyll rather than from damage to the photosystem II reaction centres. We propose that this increase in radiationless energy dissipation serves to protect the reaction centres against damage by excessive excitation.

Isolation Of A Photosystem Ii Associated 36 Kda Polypeptide And An Iron-Stress 34 Kda Polypeptide From Thylakoid Membranes Of The Cyanobacterium Synechococcus Pcc 6301 Grown Under Mild Iron Deficiency

1992 ◽  
Vol 47 (11-12) ◽  
pp. 867-874 ◽  
Author(s):  
Klaus-Peter Michel ◽  
Elfriede K. Pistorius
Keyword(s):  
Amino Acid ◽  
Iron Deficiency ◽  
Photosystem Ii ◽  
Thylakoid Membrane ◽  
Thylakoid Membranes ◽  
Acid Oxidase ◽  
Amino Acid Oxidase ◽  
Iron Deficient ◽  
Membrane Bound ◽  
Synechococcus Pcc 6301

A 36 kDa polypeptide which previously was shown to be present in purified photosystem II complexes from Synechococcus PCC 6301 and which crossreacts with the antiserum raised against the soluble L-amino acid oxidase of 50 kDa from Synechococcus PCC 6301 (A. E. Gau, G. Wälzlein, S. Gärtner, M. Kuhlmann, and E. K. Pistorius, Z. Naturforsch. 44c, 971, 1989), was isolated from thylakoid membranes of the same cyanobacterium grown under mild iron deficiency. This peptide is present in about equal amounts in thylakoid membranes of Synechococcus PCC 6301 grown under regular or iron deficient conditions. The antiserum raised against this thylakoid membrane bound 36 kDa peptide crossreacts with the soluble L-amino acid oxidase of 50 kDa. These results further support our conclusion that the thylakoid membrane bound 36 kDa polypeptide is a modified form of the soluble 50 kDa L-amino acid oxidase. In addition, a 34 kD a polypeptide was isolated from iron stressed thylakoid membranes, and an antiserum was also raised against this protein. Immunoblot experiments with this antiserum show that the 34 kDa peptide is present in elevated amounts in thylakoid membranes from Synechococcus cells grown under iron deficiency and that it is alm ost absent in thylakoid membranes from cells grown under regular conditions

scholarly journals 588 Photosystem II Efficiency and CO2 Assimilation in Response to Light and CO2 in Leaves of Deciduous Tree Fruit

HortScience ◽  
1999 ◽  
Vol 34 (3) ◽  
pp. 548B-548
Author(s):  
Lailiang Cheng ◽  
Leslie H. Fuchigami ◽  
Patrick J. Breen
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Electron Flow ◽  
Nonphotochemical Quenching ◽  
Reaction Centers ◽  
Deciduous Tree ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Similar Response ◽  
Psii Efficiency

Photosystem II (PSII) efficiency and CO2 assimilation in response to photon flux density (PFD) and intercellular CO2 concentration (Ci) were monitored simultaneously in leaves of apple, pear, apricot, and cherry with a combined system for measuring chlorophyll fluorescence and gas exchange. When photorespiration was minimized by low O2 (2%) and saturated CO2 (1300 ppm), a linear relationship was found between PSII efficiency and the quantum yield for CO2 assimilation with altering PFD, indicating CO2 assimilation in this case is closely linked to PSII activity. As PFD increased from 80 to 1900 μmol·m–2·s–1 under ambient CO2 (350 ppm) and O2 (21%) conditions, PSII efficiency decreased by increased nonphotochemical quenching and decreased concentration of open PSII reaction centers. The rate of linear electron transport showed a similar response to PFD as CO2 assimilation. As Ci increased from 50 to 1000 ppm under saturating PFD (1000 μmol·m–2·s–1) and ambient O2, PSII efficiency was increased initially by decreased nonphotochemical quenching and increased concentration of open PSII reaction centers and then leveled off with further a rise in Ci. CO2 assimilation reached a plateau at a higher Ci than PSII efficiency because increasing Ci diverted electron flow from O2 reduction to CO2 assimilation by depressing photorespiration. It is concluded that PSII efficiency is regulated by both nonphotochemical quenching and concentration of open PSII reaction centers in response to light and CO2 to meet the requirement for photosynthetic electron transport.

Salt Enhances Photosystem I Content and Cyclic Electron Flow via NAD(P)H Dehydrogenase in the Halotolerant Cyanobacterium Aphanothece halophytica

1996 ◽  
Vol 23 (3) ◽  
pp. 321 ◽  
Author(s):  
T Hibino ◽  
BH Lee ◽  
AK Rai ◽  
H Ishikawa ◽  
H Kojima ◽  
...  
Keyword(s):  
Photosystem Ii ◽  
Photosystem I ◽  
Electron Flow ◽  
Cyclic Electron Flow ◽  
O2 Evolution ◽  
Aphanothece Halophytica ◽  
Protein Levels ◽  
Photosynthetic O2 Evolution ◽  
Electron Donation ◽  
Halotolerant Cyanobacterium

To uncover the adaptation mechanisms of photosystems for halotolerance, changes in stoichiometry and activity of photosystems in response to changes of salinities were examined in a halotolerant cyanobacterium, Aphanothece halophytica. Photosynthetic O2 evolution was high even at high salinities. O2 evolution activity increased with increasing external concentration of NaCl, reached a maximum at 1.5 M NaCl, and then decreased. Similar salt dependence was observed for photosystem II activity. On the other hand, photosystem I activity increased concomitantly with increase in salinity. Photoacoustic measurements indicated that appreciable energy storage by photosystem I mediated cyclic electron flow at high salinities. Significant electron donation to photosystem I reaction centres through NAD(P)H-dehydrogenase complexes was observed in high salt media. The contents of cytochrome b6/f and photosystem II were almost constant under various salinity conditions, whereas the levels of chlorophyll α, photosystem I, soluble cytochrome c-553, and NAD(P)H-dehydrogenase increased in the cells grown with high salinities. These results indicate that salt specifically induces an increase of protein levels involving cyclic electron flow around photosystem I that may entail an important role for adaptation of Aphanothece halophytica cells to high salinities.

Thiazolylidene-Ketonitriles are Efficient Inhibitors of Electron Transport in Reaction Centers from Photosynthetic Bacteria

1991 ◽  
Vol 46 (11-12) ◽  
pp. 1059-1062 ◽  
Author(s):  
Walter Oettmeier ◽  
Silvana Preuße ◽  
Michael Haefs
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Reaction Center ◽  
Rhodobacter Sphaeroides ◽  
Photosynthetic Bacteria ◽  
Rhodobacter Capsulatus ◽  
Electron Flow ◽  
Reaction Centers ◽  
Inhibitory Potency ◽  
Photosynthetic Electron Flow

Thiazolylidene-ketonitriles are efficient inhibitors of photosynthetic electron flow in reaction centers from either Rhodobacter sphaeroides or Rhodobacter capsulatus. Some compounds of this class exhibit a higher inhibitory potency in the bacterial system as compared to photosystem II. Up to now, photosystem II inhibitors were generally less active in photosynthetic bacteria. An azido-thiazolylidene-ketonitrile upon illumination almost exclusively tags the L-subunit in the bacterial reaction center.

Interaction of Photosystem II Herbicides with Bicarbonate and Formate in Their Effects on Photosynthetic Electron Flow

1984 ◽  
Vol 39 (5) ◽  
pp. 374-377 ◽  
Author(s):  
J. J. S. van Rensen
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Electron Flow ◽  
Photosynthetic Electron Transport ◽  
Hill Reaction ◽  
Amaranthus Hybridus ◽  
Apparent Affinity ◽  
Photosynthetic Electron Flow ◽  
Different Characteristics ◽  
The Hill

The reactivation of the Hill reaction in CO2-depleted broken chloroplasts by various concentrations of bicarbonate was measured in the absence and in the presence of photosystem II herbicides. It appears that these herbicides decrease the apparent affinity of the thylakoid membrane for bicarbonate. Different characteristics of bicarbonate binding were observed in chloroplasts of triazine-resistant Amaranthus hybridus compared to the triazine-sensitive biotype. It is concluded that photosystem II herbicides, bicarbonate and formate interact with each other in their binding to the Qв-protein and their interference with photosynthetic electron transport.

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