An Amperometric Study on the Time Constants of Oxygen Release in Thylakoids of Nicotiana tabacum and Oscillatoria chalybea

1990 ◽  
Vol 45 (11-12) ◽  
pp. 1117-1126 ◽  
Author(s):  
R. Schulder ◽  
K. P. Bader ◽  
G. H. Schmid
Keyword(s):  
Electrode System ◽  
Diffusion Time ◽  
Release Time ◽  
Photosynthetic Oxygen Evolution ◽  
Filamentous Cyanobacterium ◽  
Oxygen Release ◽  
Full Agreement ◽  
Oscillatoria Chalybea ◽  
Photosynthetic Oxygen ◽  
Time Required

Abstract Measurement of photosynthetic oxygen evolution in tobacco chloroplasts and thylakoids of the filamentous cyanobacterium Oscillatoria chalybea by means of the “Three-Electrode-System”, described by Schmid and Thibault in 1979, yields half-rise times for the directly measured amperometric O2-signal of approximately 2 msec for tobacco chloroplasts and slightly more than 2 msec for thylakoids of Oscillatoria chalybea. An estimate of the possible contribution of the diffusion time required for oxygen to leave the thylakoid membrane (7.5 nm thickness) or the chloroplast (diameter 4 -5 μm) might bring the measured O2-release time below 1 msec in full agreement with measurements by Joliot et al. in 1966.

Study on the Parameters Affecting Oxygen Release Time Measurements by Amperometry

1992 ◽  
Vol 47 (5-6) ◽  
pp. 465-473 ◽  
Author(s):  
R. Schulder ◽  
K. Burda ◽  
K. Strzałka ◽  
K. P. Bader ◽  
G. H. Schmid
Keyword(s):  
Oxygen Evolution ◽  
Average Distance ◽  
Average Diameter ◽  
Release Time ◽  
Lag Phase ◽  
Minimal Distance ◽  
Photosynthetic Oxygen Evolution ◽  
Oxygen Release ◽  
Limit Value ◽  
A Value

The amperometric analysis of photosynthetic oxygen evolution in thylakoid membrane preparations of tobacco, sedimented on a large surface electrode, shows that the oxygen signal is preceded by a lag phase of 1.2 ms. As the used tobacco lamellar systems have an average diameter of 4 - 5 μm this lag phase is interpreted to be due to an average distance of 2.4 μm between oxygen emitting sources and the electrode surface. This interpretation of the lag phase is substantiated by the fact that photosystem I-mediated oxygen uptake in the same preparation measured with the same amperometric technique exhibits the same lag phase although the kinetic uptake parameters are considerably slower than those of oxygen evolution due to the water-splitting reaction. The analysis of the oxygen evolution signal shows that the sedimentation time i.e. the quality of the contact of the source with the electrode is decisive for the measured value for the oxygen release time, which with this method without much effort comes out to be certainly not longer than 1.5 ms. A computer simulation shows that the distance of the oxygen emitting layer from the electrode as well as its thickness and the actual release time are variables which influence practically all parameters (signal shape, amplitude etc.) of such amperometric signals. From this it appears that the determined apparent experimental parameters of oxygen evolution kinetics contain deformations due to the thickness of the sample and the diffusion distance from the electrode. An extrapolation calculated for a sample of infinite thinness separated from the electrode by a minimal distance of 0.001 μm with τ of 5.5 ms yields a lower limit value for the half-rise time of 0.5 ms, a value which has been experimentally determined by EPR oximetry (K. Strzalka, T. Walczak, T. Sarna, and H. M. Swartz, Arch. Biochem. Biophys. 281, 312 (1990)).

Alterations in cell pigmentation, protein expression, and photosynthetic capacity of the cyanobacterium Oscillatoria tenuis grown under low iron conditions

1995 ◽  
Vol 41 (12) ◽  
pp. 1117-1123 ◽  
Author(s):  
Charles G. Trick ◽  
Steven W. Wilhelm ◽  
Christopher M. Brown
Keyword(s):  
Growth Rates ◽  
Photosynthetic Capacity ◽  
Nutrient Status ◽  
Photosynthetic Oxygen Evolution ◽  
Filamentous Cyanobacterium ◽  
Periplasmic Proteins ◽  
Specific Proteins ◽  
Photosynthetic Oxygen ◽  
Photosynthetic Microorganisms ◽  
Additional Iron

To better describe the iron-limited nutrient status of aquatic photosynthetic microorganisms, we examined the effects of iron limitation on pigment content, maximum rates of photosynthetic oxygen evolution, and respiratory oxygen consumption in the filamentous cyanobacterium Oscillatoria tenuis Ag. Within the range of iron (4.2 × 10−5–5.1 × 10−9 M FeCl3), growth rates were not limited by photosynthetic capacity but rather by another, as of yet undetermined, iron-requiring cellular function. We have also investigated membrane proteins that are induced when the cells are grown in low iron medium. Using membrane fractionation techniques we were able to recognize specific proteins localized in the outer membrane and periplasmic space of O. tenuis. The recovery of growth rates at low iron levels occurred in parallel with the induction of these proteins and the production of extracellular siderophores. The additional iron acquired by this high affinity transport system did not reestablish photosynthesis in O. tenuis to the iron-satiated level but did reestablish growth to iron-replete levels. Oscillatoria tenuis appears to invoke an alternate physiology to compensate for iron deficiency.Key words: cyanobacteria, iron, Oscillatoria tenuis, periplasmic proteins, photosynthesis.

scholarly journals TIP family aquaporins play role in chloroplast osmoregulation and photosynthesis

2020 ◽  
Author(s):  
Azeez Beebo ◽  
Ahmad Zia ◽  
Christopher R. Kinzel ◽  
Andrei Herdean ◽  
Karim Bouhidel ◽  
...  
Keyword(s):  
Electron Transport ◽  
Oxygen Evolution ◽  
Photosynthetic Electron Transport ◽  
Chloroplast Envelope ◽  
Photosynthetic Oxygen Evolution ◽  
Wild Type ◽  
Thylakoid Lumen ◽  
Photosynthetic Oxygen ◽  
Osmotic Treatment ◽  
Envelope Membranes

SUMMARYPhotosynthetic oxygen evolution by photosystem II requires water supply into the chloroplast to reach the thylakoid lumen. A rapid water flow is also required into the chloroplast for optimal oxygen evolution and to overcome osmotic stress. The mechanisms governing water transport in chloroplasts are largely unexplored. Previous proteomics indicated the presence of three aquaporins from the tonoplast intrinsic protein (TIP) family, TIP1;1, TIP1;2 and TIP2;1, in chloroplast membranes of Arabidopsis thaliana. Here we revisited their location and studied their role in chloroplasts. Localization experiments indicated that TIP2;1 resides in the thylakoid, whereas TIP1;2 is present in both thylakoid and envelope membranes. Mutants lacking TIP1;2 and/or TIP2;1 did not display a macroscopic phenotype when grown under standard conditions. The mutant chloroplasts and thylakoids underwent less volume changes than the corresponding wild type preparations upon osmotic treatment and in the light. Significantly reduced rates of photosynthetic electron transport were obtained in the mutant leaves, with implications on the CO2 fixation rates. However, electron transport rates did not significantly differ between mutants and wild type when isolated thylakoids were examined. Less acidification of the thylakoid lumen was measured in mutants thylakoids, resulting in a slower induction of delta pH-dependent photoprotective mechanisms. These results identify TIP1;2 and TIP2;1 as chloroplast proteins and highlight their importance for osmoregulation and optimal photosynthesis. A third aquaporin, TIP1;1, is present in the chloroplast envelope, and may play role in photosynthesis under excessive light conditions, as based on the weak photosynthetic phenotype of its mutant.

Sign in / Sign up

Export Citation Format

Share Document