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Influence de l'oxygene sur les transferts d'electrons de la photosynthese. I. Influence de diverses concentrations d'oxygene sur quel ques reactions de Hill |
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| Authors: | Y Mathieu |
| Institution: | Laboratoire de Physiologie Cellulaire Végétale, associé au C.N.R.S., Faculté des Sciences, 91 -, Orsay, France |
| Abstract: | Influence of oxygen on the electron transfers of photosynthesis. I. Influence of some oxygen concentrations on some Hill reactions The influence of O2 concentrations on the Hill reactions in the presence of p-benzoquinone, ferricyanide, NADP+, NADP+ plus ferredoxin has been studied with isolated spinach chloroplasts. Because of the partial reoxidation of the hydroquinone, which is depending upon the O2 concentration, it does not seem possible to localize a site of action for O2. With ferricyanide the influence of O2 is weak. However, the rate of ferricyanide reduction is increased in the presence of O2. The observed stimulation is greater for 21% O2 than for 70% O2. Bicarbonate stimulates the ferricyanide reduction and decreases the stimulating effect of 21% O2. O2 decreases the rate of NADP+ reduction. Ferredoxin as well as bicarbonate stimulate the NADP+ reduction and reduce the O2 inhibition. These results seem to indicate that O2 may enter the electron transport chain at a site situated near Photosystem I and before the ferredoxin's site. The inhibitory effect of O2 on the Hill reactions with p-benzoquinone and NADP+ is depending upon the plants' growth conditions. It is greater with plants grown under weak light. |
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