THE EFFECTS OF MAGNESIUM OR POTASSIUM-DEFICIENCY EXPOSURE ON SPRUCE NEEDLE PHOTOSYNTHESIS WERE STUDIED BEFORE SYMPTOMS OF DAMAGE WERE VISIBLE. THEN, THE RECOVERY WAS FOLLOWEDD. WATER CONTENT, PIGMENT CONTENT AND O2 EVOLUTION RATE WERE CHOSEN AS PARAMETERS OF PHYSIOLOGICAL ACTIVITY IN ADDITION TO CHLOROPHYLL FLUORESCENCE.NA-NOT AVAILABL