The purpose of this study was to develop an appropriate physiological test for rapid and reliable diagnosis of plant resistance to water stress and subsequently to assess the tolerance of some tomato genotypes (Solanum lycopersicum). Experiments were carried out during the stress period and after its recovery. Valuation of the tolerance of plants was carried out by means of a physiological test. It was observed that the water stress has an inhibitory effect on the physiological state of tomato plants. Leaf gas exchange and chlorophyll fluorescence were identified as particularly suitable indicators for assessing the tolerance of tomato genotypes to water stress.