scholarly journals Stabilization of Photosystem II (O2 Evolution) of Spinach Chloroplasts by Radiation-induced Immobilization

1981 ◽  
Vol 67 (2) ◽  
pp. 351-354 ◽  
Author(s):  
Takashi Fujimura ◽  
Fumio Yoshii ◽  
Isao Kaetsu
Keyword(s):  
Photosystem Ii ◽  
O2 Evolution ◽  
Spinach Chloroplasts ◽  
Radiation Induced

scholarly journals The photosystem II-associated Cah3 in Chlamydomonas enhances the O2 evolution rate by proton removal

2008 ◽  
Vol 27 (5) ◽  
pp. 782-791 ◽  
Author(s):  
Tatiana Shutova ◽  
Hella Kenneweg ◽  
Joachim Buchta ◽  
Julia Nikitina ◽  
Vasily Terentyev ◽  
...  
Keyword(s):  
Photosystem Ii ◽  
Evolution Rate ◽  
O2 Evolution

Ammonia Assimilation and Metabolite Transport in Isolated Chloroplasts. II. Malate Stimulates Ammonia Assimilation in Chloroplasts Isolated From Leaves of Dicotyledonous but Not Monocotyledonous Species

1992 ◽  
Vol 19 (6) ◽  
pp. 659 ◽  
Author(s):  
JW Yu ◽  
KC Woo
Keyword(s):  
Nutrient Solution ◽  
The Other ◽  
Ammonia Assimilation ◽  
O2 Evolution ◽  
Evolution System ◽  
Metabolite Transport ◽  
Spinach Chloroplasts ◽  
Counter Ion ◽  
High Nutrient ◽  
Isolated Chloroplasts

Malate stimulated NH3 assimilation, as determined by a (2-oxoglutarate, NH3)-dependent O2 evolution system, by up to 3-fold in chloroplasts isolated from leaves of dicot but not monocot species. This difference was apparently correlated with the endogenous metabolite pools present in these chloroplast preparations. During NH3 assimilation the glutamate and glutamine pools were large in spinach (dicot) but small in oat chloroplasts. The reverse was the case for the 2-oxoglutarate (2-OG) pool. The addition of malate substantially increased the glutamate, glutamine and 2-OG pools in spinach chloroplasts but had little effect in oat chloroplasts. This suggests that the supply of 2-OG was apparently limiting NH3 assimilation in spinach chloroplasts. Malate increased this supply and, consequently, stimulated NH3 assimilation. On the other hand, NH3 assimilation in oat chloroplasts seemed to be limited by the supply of glutamate and glutamine which could not be overcome by the addition of malate. Chloroplasts were also isolated from oat seedlings watered with high nutrient solution. The rates of NH3 assimilation in these organelles exceeded those obtained in spinach chloroplasts. But the addition of malate had little effect on (2-OG, NH3)-dependent O2 evolution in these oat chloroplasts. Since malate did not inhibit this activity it is conceivable that it still might play a role, albeit a 'passive' role, in serving as a counter-ion for 2-OG uptake via the 2-OG translocator and glutamate export via the Dct translocator during NH3 assimilation.

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.

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