EFFECTS OF HEAVY-METAL POLLUTED SOILS ON THE GENETIC-STRUCTURE OF NORWAY SPRUCE SEEDLING POPULATIONS

Young seedlings raised from six different Norway spruce seed provenanc es were grown in heavy-metal contaminated soils at two severely pollut ed areas. After ten months, the rate of survival ranged from 30% - 42% and from 45% - 52% at the two polluted areas, respectively. Compariso ns of the genetic structure analysed at eight polymorphic enzyme loci showed that the heterozygote frequencies at four of these loci have su bstantially increased in the surviving seedling collections across all provenances as compared to the initial embryo samples. These results were discussed in relation to the metabolic role of the respective enz ymes in response to environmental stress and the possibly greater reac tion efficiency of the heterozygous enzyme phenotypes in order to reco gnize a probable overdominant selection regime.