Separate action spectra for the two photochemical systems of photosynthesis.

Action spectra have been obtained which are believed to represent the 2 photochemical systems in the marine green alga, Ulva lobata. Measurement of transient rates of O(2) uptake in the presence of DCMU furnished the data for the spectrum representing system I. The action spectrum for system II refers to O(2) evolution rates after the Ulva was pretreated in an atmosphere of high O(2) concentration. Tissue responses after high O(2) exposure suggests an inhibition of the photosynthetic functioning of system I.