Action Spectra for the Transient and the Normal Photosynthetic Oxygen Evolution in Wheat Leaves

An action spectrum within the wavelength region 430–700 nm has been determined for an oxygen Iransient isolated from the main photosynthetic oxygen evolution in wheat leaves. the spectrum follows the absorption spectrum of chlorophyll b. In order to compare this oxygen evolving process with the normal photosynthetic oxygen evolution, an action spectrum for this later process was also determined but only in the wavelength region 600–700 nm. This action spectrum closely corresponds to other action spectra for the photosynthetic oxygen evolution found in the literature. The behaviour of the oxygen transient after various treatments was also studied. It was found that the transient oxygen evolution was influenced by the dark period between irradiations, and by a previous irradiation with a wavelength longer than 695 nm, both conditions having a promoting effect on the oxygen evolution. The action spectra and the other findings are discussed on the basis of the two-pigment hypothesis.