אסיף מאגר המחקר החקלאי

Involvement of Photosystem Two in Non‐Oxygen Evolving Non‐Cyclic, and in Cyclic Electron Flow Processes in Chloroplasts

Year:

1970

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Volume :

15

Co-Authors:

Ben‐Hayyim, G., Biochemistry Department, Weizmann Institute of Science, P. O. Box 26, Rehovot, Israel
Avron, M., Biochemistry Department, Weizmann Institute of Science, P. O. Box 26, Rehovot, Israel

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Abstract:

Ascorbate is concluded to serve as an electron donor at a site which is prior to photosystem 2. This conclusion is supported by the following observations: Addition of ascorbate doubled the apparent rate of oxygen uptake in the presence of diquat. NADP+ photoreduction was not affected by addition of ascorbate, while the concomitant oxygen evolution was markedly inhibited. Both of these reactions were as sensitive to 3‐(3,4‐dichlorophenol)‐1,1‐dimethylurea in the presence of ascorbate as a normal Hill reaction. Both reactions shawed the red‐drop phenomenon in the presence of ascorbate. Ascorbate did not serve as an electron donor prior to photosystem two either in heat‐or in Tris‐treated chloroplast preparations. However, ascorbate and hydroquinone did. Tris‐treated chloroplast preparations catalyse a hydroquinone dependent cyclic photophosphorylation in which photosystem two is involved. Copyright © 1970, Wiley Blackwell. All rights reserved

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