[Ontogenesis of saffron plants (Crocus sativus) and changes in their stem apices]

A study of the saffron ontogenesis has been carried out, with special reference to the morphophysiological state of cells and nuclei in the stem apices. 4 periods were established in the development of stem apices: (1) formation of apical meristem (November), (2) slow development coinciding with the intensive plant vegetation (December--February), (3) transition to generative development when the vegetative organs begin to dry off (March) and (4) differentiation of generative organs at the time when the corm is underground and vegetative organs almost fully absent (summer). The development of apex is accompanied by changes in the nuclear structure and fluctuations of mitotic activity. The critical period of transition to the phase of generative development takes place in March, long before the formation of visible generative organs and flowering.