Oxygen-evolving activity of thylakoids from barley plants cultivated on different concentrations of jasmonic Acid.

The kinetics characteristics of oxygen evolution in thylakoids prepared from barley (Horeum vulgare) seedlings grown in the presence of different jasmonic acid (JA) concentrations were studied. In comparison to control preparations, 100 micromolar JA-treated samples show an inhibition of the Hill activity (46%) and of O(2)-flash yields to above 70%. A damping in the oscillations of O(2) yields, induced by a flash train, increases with increasing growth regulator concentration. After these treatments, the value of the total number of oxygen-evolving centers (S(0) + S(1)), estimated according to the Kok scheme, shows a considerable decrease. In 100 micromolar JA-treated preparations, the turnover half-time of S(1)-states increases and the stability of the S(2)- and S(3)-states decreases.