The far red induced slow component of delayed light from chloroplasts is emitted from Photosystem II : Evidence from emission spectroscopy.

In spinach chloroplasts illuminated with far red light, the relative intensity maximum during the decay of delayed light is emitted at 680-690 nm. This finding supports previous models predicting emission from Photosystem II, and contradicts earlier attributions to Photosystem I.Due to self absorption, the emission spectrum of the relative maximum is shifted to longer wavelengths and displays apparent Photosystem I characteristics in chloroplast samples of higher concentration or in leaves. This may have caused earlier investigators to ascribe the emission to Photosystem I.A differences between the spectral width of the emission spectra of delayed fluorescence and the relative maximum indicates that these two phenomena represent emission from different sub-populations of Photosystem II centers.