In leaves of Sdndapsus aurea L. after a mild heat treatment (5 min 46-49 “C), the chlorophyll fluorescence yield, measured with a pulse amplitudě modulation (PAM) fluorometer and excited with short pulses of actínic radiation (50-500 ms), increased during excitation up to the maximum F,„. The fluorescence yield then decreased to the minimum (where Fn^„ may be lower than the initial fluorescence yield Fq) and rose again to the second maximum F„^, which occurred some seconds (2-20) after that pulse of the actínic radiation.