Pulsed fluorometry of primary photosynthesis processes in higher plants

The principles of pulsed fluorometry are presented and an experimental apparatus in which fluorescence is excited by single optical pulses of ~2 psec duration at λ = 530, 353, and 265 nm is described. Fluorescence is recorded using two image-converter cameras with a temporal resolution of 2 and 20 psec. Luminescence from the camera screen is detected by a vidicon and then processed in an analyzer-computer system. The results of experimental investigations of primary photosynthesis processes are presented. It is established that energy transfer within the light-gathering assembly is achieved by localized excitons having the following parameters: diffusion coefficient D~2×10^–2 cm²/sec, diffusion length L~90 nm, and transfer probability W~10¹² sec^–1. Evolution of excitation in focusing antennas of photosystems and long-wavelength pigment–protein complexes is studied. The fluorescence lifetime and quantum yield of photoactive chlorophyll are determined, these being ~60 psec and 3×10^–3 (P680) and 5–7 psec and 3×10^–4 (P700).