Lawn grasses are the most convenient objects for study of patterns of gas resistance, since they permit the subjective visual estimation method of damage evaluation to be avoided. It can be proposed that differences in gas resistance of individual species are determined by the physiological and biochemical characteristics of the plants and that, in the populations of each species, by the anatomical and morphological characteristics of the leaf structure and amount of acid gas absorbed. It has been determined that the S35 activity of all species of plants is 3-25 times higher in the dead leaf tissues than in the living. It can be proposed that S35 transport through the vessels with the water flow to the leaf tips is accomplished to a greater extent in monocotyledenous plants than in dicotyledenous ones. Toxic compounds accumulated by the soil can cause death of seeds or decrease in germination, impairment of growth and development of the plants and change in resistance to SO2. Lethal concentrations of SO2 in plants of resistant species are higher than in nonresistant ones. Plants with larger leaf surface dimensions proved to be more resistant to SO2.