Main content area

Stimulation of photophosphorylation by ascorbate as a function of light intensity

Forti, G., Elli, G.
Plant physiology 1996 v.112 no.4 pp. 1509-1511
free radicals, Spinacia oleracea, thylakoids, leaves, ascorbic acid, adenosine triphosphate, biosynthesis, light intensity, pH, adenosinetriphosphatase, oxidoreductases, dehydroascorbic acid, photophosphorylation, enzyme activity, photosystem I, light, electron transfer, ascorbate peroxidase
When isolated, stroma-free thylakoids are illuminated in the presence of ADP and orthophosphate in the absence of any electron acceptor except O2, the addition of ascorbate stimulates electron transport through the formation of the radical monodehydroascorbate and the coupled synthesis of ATP (G. Forti and G. Elli [1995] Plant Physiol 109: 1207-1211). The stimulation is shown here to be higher at low light intensity. These observations are explained in terms of the increase of the electron transport rate by ascorbate which established a higher value of the steady-state pH gradient, causing activation of ATP synthase, which is known to be dependent on the level of the H+-electrochemical potential difference, and a higher rate of proton flux across the membranes available for utilization by ATP synthesis.