Abstract

J. G. Ray and Jojo George

Roadside vegetations are open to contaminations of diverse heavy metals and other gaseous pollutants, and to physical disturbances of being trampled by pedestrians and crushed by vehicles continuously. Being a biodiversityrich region of the world, roadsides of Southwest India, are expected to be rich in unique pollution-tolerant species. Tolerant plants in heavy metal polluted roadsides may be excluders or accumulators or hyper-accumulators of the metals. Phytosociology of communities on roadsides is significant in the identification of the degree of tolerance of species, because the method in general, is considered efficient and appropriate to assess the ecological potentials of plants in natural communities. Floristic survey and phytosociological analysis of 110 km of busy roadsides of a biodiversity-rich tropical zone, Kottayam District of Kerala, South India, showed 85 species belonging to 27 families differently tolerant to the stressful environment, which included exotics as well as medicinal plants. Botanical details and ecological potentials of the tolerant species found on these roadsides are discussed. Phytosociological investigations on roadsides enable identification of the hyper-tolerant; also provide information regarding patterns of introduction of exotics into natural vegetations. Hyper- tolerance is useful clue to the preliminary screening of the hyper-accumulation potentials of plants.