The aim of the diploma thesis was to find out the termination date of endogenous dormancy of bud flowers within the selected set of apricot varieties and simultaneously keep track of the development of various phases of microsporogenenesis. The last goal was to capture the phenological indicators of flowering and fruit development. The experimental part describes material and methodology tested on the peach varieties at Horticultural Faculty in Lednice in a two-year experiment during 2013-2014. The temperature curve was significantly different in both years. Year 2013 was characterized by gradual and lengthty progression of low temperatures, and by late termination of endogenous dormancy. Year 2014 was entirely unlike the previous one in its rapid progression of above-average temperatures and dynamic emersion of varieties from dormancy. After evaluating the results the varieties were divided into three groups with short, medium and long period preceding the termination of dormancy. The results of the observation of microsporogenesis phases shows that development of each phase is not uniform in all varieties of monitored peaches. The pollen grains development rate is greatly influenced by the temperature curve. Varieties with late termination of dormancy and slow development of microsporogenesis phases are less susceptible to impairment of the flower buds by late spring frosts.