В роботі представлені фенологічні спостереження, морфометричні дані та результати молекулярно-генетичного аналізу рослин A. thaliana, які попередньо були опромінені рентгенівським, гамма і ультрафіолетовим випромінюванням у гострому і хронічних режимах. Дані свідчать, що хронічне опромінення, у порівнянні з гострим режимом, на порядок ефективніше діє на експресію генів фотоперіодичного механізму CO, GI, FLC, FT, диференціації апікальної меристеми AP1, LFY, репарації RAD51 і проліферації PCNA2. Показано наявність нелінійної залежності в зміні експресії ключових генів цвітіння A. thaliana.Ключові слова: Ключові слова: гостре і хронічне опромінення, гамма-випромінювання, УФ-С, цвітіння, транскрипційні фактори, експресія генів, Arabidopsis thaliana.^UThe aim of the study was to investigate the different modes of ionizing and UV-C radiation effects on the A. thaliana plants flowering time and the expression of the photoperiodic pathways genes CO, GI, FLS, FT, the repair gene RAD51, proliferation gene PCNA2 and differentiation of meristem genes AP1, LFY. The doctoral thesis firstly was been shown the high suppression of flowering determination genes by chronic irradiation and presence of gene expression changes nonlinear dependence under the action of ionizing radiation sublethal doses. The influence of the light spectrum in which the experimental plants were grown on the activity of the photoperiodic genes after UV-C irradiation was firstly demonstrated.The object of study was A.thaliana (L.) Heynh (Brassicaceae) seedlings cultured in soil and in vitro in laboratory conditions. The following methods were used to perform the work: phenological analysis according to Boyes' (2001) classification for A.thaliana, acute exposure of plants with X-rays, chronic irradiation of seedlings from the 137CsCl radionuclide source, UV-C irradiation with a wavelength of 254 nm, molecular analysis using real-time PCR and mathematical analysis of relative gene expression was worked.According to the results of the research, the effect of ionizing radiation on the genetic mechanisms of flowering regulation is significantly dependent on the type of radiation, the mode of exposure: acute or prolonged chronic, total dose and previous conditions of plant cultivation. It is substantiated that the methodology and approach used in the our investigations are sensitive and informative for the study of the influence of rare ionizing radiation on the reproductive function of plants.The phenomenal observation shown that chronic irradiation delay flowering time for a dose of 17 cGy and more. At a dose of 3 cGy, on the contrary it demonstrated the early flowering. In interval of doses 3-6 Gy of acute X-ray exposure provides early flowering, but within acute doses 9-15 Gy delay the flowering time of the plants comparing the control group.Using the relative expression analyses we found that it is established chronic irradiation contributes to the efficiency of effects on the CO, GI, FT, FLS, AP1, LFY genes than acute exposure. It was proved that mutants jin1 Col-0 (insensitive to jasmonates partway) with defective (not sensitive) receptors to rod acid, the level of expression of genes of flowering CO, GI, AP1 destroyed, added with the content of wild type A. thialiana Col 0. The data indicates the involvement of jasmine acid in the circadian clock and the development of a floral meristem for such stressors. It is shown that acute radiation up to 10 Gy uses wild-type photoperiodic gene expedition, but the expression of the AP1 gene is placed in the mutant jin1, which requires indicating thesignal requiring the presence of an acid in the regulation for reproduction.According to comparisons of the responses of the general systems to the radiation exposure, it was shown that for the cultivation of results in optimal white light it is manifested by the accelerated flowering, the blue and red spectrum illumination, which leads to the delay of flowering time. UV-C irradiation has for the first time been found to stimulate the expression of CO and GI circadian clock genes, and apical meristems can be found at various positions for floral growth possibilities, which can be considered for a whole plant. Our study showed that results were achieved in response to UV-C irradiation and this was understandable. For the results obtained, it was found that the light spectrum in which the research plants were produced had an effect on the activity of flowering genes post UV-C irradiation.The results of researches were printed in 17 scientific papers, of which 9 peer reviewed articles and 7 abstracts in conference proceedings. Published papers fully reflect the main content of the dissertation.Keywords: ionizing radiation, ultraviolet radiation, Х-rays, gamma radiation, UV-C, photoperiodic pathway, flowering, Arabidopsis thaliana, transcription factors, acute irradiation, chronic irradiation.