The study is devoted to the problem of the genetic basis of plant adaptation. The important adaptive traits of the model species of Arabidopsis thaliana were studied: vernalization requirement, flowering time and the time of seed germination in plants of northern natural populations (Karelia). Specific expression patterns of the gene FLC and VIN3, which control these traits, have been revealed. A low level of FLC mRNA transcripts in non-vernalized plants at the rosette stage was established, with followed by increased expression on the 10-30th day of vernalization, which differs from the data of other researchers. The initially low level of VIN3 mRNA transcripts in non-vernalized plants unexpectedly increases in some populations during vernalization on the 20th day, in contrast to literature data. It has been shown that a longer vernalization (9 week) is required for a mass transition to flowering of plants from populations of the northern periphery of the species range in the Onega Lake basin compared to vernalization (6 weeks) of plants from the milder climate of Lake Ladoga islands. A study of the degree of dormancy of seeds, which affects the time of germination, showed that in cold climates A. thaliana seeds have a stronger dormancy at a high summer temperature (22 ºС) compared to a cool autumn temperature (10 ºС). This ensures their germination in the autumn and flowering in the spring, after the end of vernalization. It is suggested that in Karelian Arabidopsis thaliana populations located on the northern periphery of the species range, one of the mechanisms of plant adaptation to a cold climate is adaptive pleiotropy, exhibited in the peculiarities of the expression of the FLC and VIN3 genes, which control the timing of seed germination in autumn and flowering plants in spring, after vernalization, which ensures both seedling survival and maximum reproductive success.