Determination is an event which programs the future developmental fate of a cell or a group of cells. It is often a stable state but not necessarily an irreversible condition. In general terms, a cell or group of cells is determined when it exhibits the same developmental fate whether grown in situ, in isolation, or at a new place in or on the organism. Determination has been extensively documented and studied primarily in animals. In plant development, determination is often an obscure component because many plant cells are totipotent and can express this totipotency as a result of manipulation. Dr. McDaniel has identified a situation in plant development, floral development in day- neutral and photoperiodic tobaccos, in which determination is stable enough to permit investigation. The proposed study has three major goals: 1. Establish when the meristem of the terminal bud in day-neutral and in short-day tobaccos become determined for floral development, 2. Establish the developmental fate of cells in the meristem of florally- determined terminal and axillary buds of day-neutral tobacco, and 3. Establish in day-neutral tobacco the source(s) of the signal(s) which induces floral determination. Whole plant manipulations, histological analysis, tissue culture, and clonal analysis will be employed. Understanding determination is critical for any in-depth, comprehensive understanding of development in multicellular organisms. Determination has been extensively studied in animals. In plants this problem has received only minimal attention. Dr. McDaniel is attempting to address this problem using floral determination in tobacco.
