The aim of this study was to investigate the physiological response of species of tree Tilia cordata Mill. From zones with different pollution in Balti ecosystem. The influence of car emissions on vegetation has been determined in function of the intensity of the auto traffic. As it has been demonstrated physiological and biochemical manifestations (the concentration of assimilating pigments and of the total water content) serve as an indicator of the state of plants exposed to stress factors and can be used as a methodology for estimation of the ecological impact of car emissions on vegetation. The impact of certain stress factors (auto emissions) on the bio productivity of vegetation was also estimated. In the municipality of Balti are registered 49453 transport units. The highest number was registered on Stefan cel Mare Street in the perimeter of Nicolae Iorga Street with the bypass of the town. Balti – 1806 units / hour. The ratio of assimilative pigments ―a‖ ―b‖, as in the case of the total water content in the tree leafs (Tilia cordata Mill.) from Balti urban ecosystem proved to be closely related to the number of transport units. Thus, the lowest concentration was established on Stefan cel Mare street, the sector near the bus station and Nicolae Iorga street, where is the largest number of transport units.