REPETITIVE DNA AS MARKER FOR THE STUDY OF MALE GAMETOGENESIS IN HIGHER-PLANTS .1. ANALYSIS IN SOME SPECIES OF TRADESCANTIA AND NARCISSUS

The use of heterochromatic regions, containing moderately repetitive D NA as markers, has allowed to follow the course of development of the generative and vegetative nuclei in the pollen grains of some species of Tradescantia and Narcissus. It has been found that the chromocentre s, relatives to the NOR-heterochromatin, are not randomly distributed. This implies the existence of a special mechanism governing the orien tation of the centromeres in the spindle-shaped generative nuclei: a p redisposition which may facilitate the mitotic process in the pollen t ube.