The work was carried out on the pollen of Hippeastrum hibridum, whose size (ca 55 mcm) permits to follow both the pollen tube formation and development of the vegetative nucleus and generative cell within the first two hours before the growing point arising. Using fluorescent dye Hoechst 33342 chromatin state alterations accompanying changes in the pollen physiological state were investigated. The maximum fluorescent intensity was observed in 30 min of staining and reflected the maximum chromatin functional activity. Histograms of pollen distribution according to fluorescent intensity differ considerably with doses of irradiation (500, 1000, 2000, 3000 and 4000 Gy). Besides, a germinative index of fluorescence intensity was calculated. A comparative analysis of these data has shown that the lowest decrease in fluorescent intensity observed at 500, 3000 and 4000 Gy, was accompanied by different germinative indices. At 500 Gy, the index was 2.5 times lower than in the control, but at 4000 G no germination was not noted. The process of pollen grain development is supposed to be more intensive and faster at 500 Gy, than in the control. At 4000 Gy, a decrease in the functional pollen activity is accompanied by decrease or inhibition of chromatin functional activity.