Pulse Amplitude Modulated (PAM) fiuorometry is a sensitive and rapid method used to assess toxic effect of chemical components in plants. This study evaluates the difference in leaf sensitivity of two grapevine varieties, Pannon frankos and Narancsízű, to copper. The Photosynthetic efficiency of the varieties was measured as the ratio of variable to maximal chlorophyil fiuorescence (Fv/Fm). Young and older leaves of these varieties were exposed to four different pesticides with copper active ingredients in the recommended dosage: Bordói por (copper sulphate), Champion (copper hydroxide), Rézoxiklorid (copper-oxychloride) and Ridomil Gold Plus (mefenoxamcopper-oxychlorid) and their physiology were studied 4 times, on the 27, 4", 8" and 12" days after treatments. These pesticides caused proportional decrease in the photosynthetic efficiency
