MAINTENANCE OF GAMETOPHYTIC DEVELOPMENT AFTER SYMMETRICAL DIVISION INTOBACCO MICROSPORE CULTURE

Isolated tobacco (Nicotiana tabacum L.) microspores maturing in vitro can be induced to undergo symmetrical divisions, instead of the normal asymmetrical first pollen mitosis, by addition of anther extracts to the culture medium. The two daughter cells in symmetrically divided po llen resemble vegetative pollen cells in cytological characteristics, nuclear size and chromatin condensation, are separated by a cell wall and remain viable during in vitro maturation. After transfer to a germ ination medium, only one of the two vegetative-like cells forms a poll en tube in vitro. Therefore, apparently normal gametophytic developmen t can be maintained after symmetrical microspore division. These resul ts are discussed in relation to current models for induction of micros pore embryogenesis.