The applications, problems and limitations of fluorescence measurement
s in photophysiology are discussed. Great care is required in interpre
ting fluorescence measurements from algae, and in particular in compar
ing results from different taxa, The existing pulse amplitude modulate
d (PAM) instrumentation seems to be satisfactory as far as macroalgae
are concerned, and the way is open for novel work on photosystem physi
ology, regulation and ecological adaptation.