This volume contains the papers, presented during a conference, organized jointly by the "Opzoekingsstation van Gorsem" and the "Limburgs Universitair Centrum," Belgium from 22 to 27 August 1982. For this third meeting, the chosen topic was the effect of different stresses on photosynthesis. Most of the research in this field is realized on water stress and temperature stress; this situation is refllected in the conference programme. However, the imp- tance of the other factors such as light, CO, salinity, anaerobiosis, was 2 also emphasized especially during the important discussion...