Nuclear Transition Between the Conjunction Cells of Phaeodactylum tricornutum Bohlin (Bacillariophyta)

P732; Phaeodactylum tricornutum is one of the important marine diatoms for oceanic primary production.Its reproduction has profound significance in the life cycle;however,the nuclear behavior during its sexual reproduction was not clear.In this study,we observed the nuclear transition and determined its correlation with cell conjunction.It was found that two cells jointed at their apices first and swung and aligned each other immediately,and nucleus from one cell was able to transfer into another one during cell conjugation.The cell pairs conjugated for nuclear transition were different from those formed in mitosis in hypovalve thickness and cellular arrangement.Our findings proved the existence of sexual reproduction in P tricornutum.