28. Effects of Chronic Irradiation in Plant Populations

An assessment of the state of plant and animal populations inhabiting polluted territories and the analysis of mechanisms of their adaptation to adverse environmental conditions undoubtedly have general biological importance. Consequently, studies that examine biological effects on non-human biota in natural settings provide a unique opportunity for obtaining information about the potential biological hazard associated with radioactive contamination. The results of long-term field studies in the Bryansk region of Russia affected by the Chernobyl accident and in the Semipalatinsk Test Site, Kazakhstan are presented. Although radionuclides cause primary damage at the molecular level, there are emergent effects at the level of populations, non-predictable solely from knowledge of elementary mechanisms of the pollutants’ influence. Plant populations growing in areas with relatively low levels of pollution are characterized by the increased level of both cytogenetic disturbances and genetic diversity. Radioactive contamination of the plant environment activates biological mechanisms, changing a population’s resistance to exposure. However, there are radioecological situations where enhanced radioresistance has not evolved or has not persisted.