Starting in 2007, we have grown soybean (Glycine max [L.] Merr. variety Soniachna) and flax (Linum usitatissimum, L. variety Kyivskyi) in the radio-contaminated Chernobyl area and analyzed the seed proteomes. In the second-generation flax seeds, we detected a 12% increase in oil content. To characterize the bases for this increase, seed development has been studied. Flax seeds were harvested in biological triplicate at 2, 4, and 6 weeks after flowering and at maturity from plants grown in nonradioactive and radio-contaminated plots in the Chernobyl area for two generations. Quantitative proteomic analyses based on 2-D gel electrophoresis (2-DE) allowed us to establish developmental profiles for 199 2-DE spots in both plots, out of which 79 were reliably identified by tandem mass spectrometry. The data suggest a statistically significant increased abundance of proteins associated with pyruvate biosynthesis via cytoplasmic glycolysis, L-malate decarboxylation, isocitrate dehydrogenation, and ethanol oxidation to acetaldehyde in early stages of seed development. This was followed by statistically significant increased abundance of ketoacyl-[acylcarrier protein] synthase I related to condensation of malonyl-ACP with elongating fatty acid chains. On the basis of these and previous data, we propose a preliminary model for plant adaptation to growth in a radio-contaminated environment. One aspect of the model suggests that changes in carbon assimilation and fatty acid biosynthesis are an integral part of plant adaptation.