EN
Fluctuations of acidity were found in leaves, shoots and roots of two groups of Mesembryanthemum crystallinum plants: watered and salt-treated. This suggests that the functioning of CAM (related to malate accumulation) in the tested organs can differ in "early CAM" in watered plants versus "full CAM" in NaCl-irrigated plants. Among the different organs analyzed, shoots exhibited the highest acidity level at the beginning of the day in both groups of M. crystallinum plants. Superoxide dismutase forms (MnSOD, CuZnSOD and FeSOD) differed in activity depending not only on their localization in the plant tissue but also on the stage of CAM development. Plants exhibiting "full CAM" and showing clear diurnal ∆-acidity had much higher total SOD activity during evening hours than in plants following "early CAM" photosynthesis. Shoots showed the highest activity of SOD.