Polyamines are widely involved in biological processes in plants including growth and development, as well as in the response to stress. However, the interpretation of polyamine participations in the induction of flowering of winter plants, and, hence, the possibility of their exogenous application to accelerate flowering, is ambiguous. Winter plants require prolonged exposure to low temperatures (vernalization) to induce the generative development, thus the changes in the levels of these substances may also result in low-temperature-stress symptoms. The aim of this work was to check, whether the increase of polyamines is actually connected with flowering of winter rape plants (cv. Górczański). To exclude the vernalization effect, vegetative apexes of winter rape were grafted onto generative plants. The content of polyamines: putrescine, spermidine and spermine was measured, using high- performance liquid chromatography, in the apical parts and the youngest leaves of grafted apexes during 1-4 weeks after grafting. For comparison of the changes in the levels of polyamines occurring during vernalization, apexes and the youngest leaves were collected from winter rape after 1-8 weeks of culture at 5°/2° C. In apexes, content of all polyamines increased at 2 week (putrescine) or 2-3 weeks (spermine and spermidine) and in the period of 5-8 weeks of vernalization. For putrescine, the maximum increase was detected during at the 6^th week and for spermidine and spermine during the 7^th week of cold treatment, i.e when approximately 60-90% of plants were in the generative phase. In leaves, the changes of polyamines composition occurred almost during the same periods as in the apexes. Confirmation of the involvement of polyamines to flowering induction was the increase of these substances observed during generative development of grafted non-vernalized apexes. The registered increase of polyamines concentrations in the first weeks after veranlization (2-3 weeks) was probably connected with the cold-stress response of rape plants.

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