APPLICATION OF NONINVASIVE SPECTROSCOPIC AND PHOTOACOUSTIC TECHNIQUESIN RESEARCH ON PHOTOSYNTHETIC PERFORMANCE OF INTACT LEAVES

The principles and application prospects of a set-up for simultaneous measurements of oxygen evolution and fluorescence in intact leaves on a fast (10 ms) time scale are described. The oxygen evolution is measu red with a photoacoustic technique. The method shows among other thing s (a) a direct determination of the intrinsic yield of 'open' reaction centres (RCs) of photosystem 2 (PS 2), and (b) the involvement of a 2 0-30 % fraction of PS 2 RCs with an apparent low oxygen yield in the l ight-adapted leaves. Double-flash P515 measurements in the light- and dark-adapted leaves have substantiated the absence of inactive RCs in leaves that were kept in the dark for more than 12 h.