NUCLEAR AND ORGANELLE DNA-REPLICATION DURING SPORE GERMINATION IN BRYOPHYTES AND EQUISETUM

In contrast to ferns, the spore nuclei of the moss, Funaria hygrometri ca, are in the G(2) phase. They do not incorporate the thymidine analo gue BUdr before the first mitosis. When spores germinate in the presen ce of aphidicolin, an inhibitor of the (nuclear) DNA polymerase alpha, they give rise to two-celled, negatively phototropic protonemata, con sisting of relatively long and thin cells. Determinations of nuclear D NA content further confirm the presence of G(2)-nuclei in Funaria spor es. Spores of Pogonatum urnigerum and of Equisetum hyemale likewise co ntain G(2)-nuclei, as shown by BUdr incorporation or experiments with aphidicolin, respectively. In germinating Funaria spores, the organell e DNA is synthesized very early and independent of nuclear DNA. A grad ient in replication of organelle DNA is found only in the long tip cel ls which are formed in the presence of aphidicolin.