Pollution of the atmosphere with various gases, dust, and aerosols, which are copiously discharged by industrial enterprises, creates extremely unfavorable conditions for planting greenery in their territory and for raising agricultural crops. Under these conditions, plants suffer a sharp loss in their productivity and often die. The harmful effect of gas in the same concentration varies, depending upon the species of plant, weather conditions, and the age of the leaf. There are species, as well as specific individuals within a single species, that are distinguished by increased gas resistance. Among the many problems related to the gas resistance of plants, attention is given to clarifying the causes of differing degrees of resistance of individual species and of individuals to the toxic gases, to their harmless concentrations, and to their effect on photosynthetic activity.