Absorption changes of Photosystem II donors and acceptors in algal cells

Flash‐induced absorption changes were measured in the 390–450 nm region, using whole cells of a double mutant strain of Chlorella sorokiniana , lacking PS I centers and part of the pigment antenna. Spectral changes associated with PS II acceptors (Q a and Q b ) and donors (p 680 , Z and L) are described. In this region, the spectrum obtained for Q b − /Q b differs markedly from that of Q a − /Q a . Different spectra were also obtained for the secondary donor (Z + /Z) when measured after one or three flashes.