Growth, Cytology and Flow Cytometry of Embryogenic Cell Suspension Cultures of Panicum maximum Jacq. and Pennisetum purpureum Schum.

Embryogenic cell suspensions of Panicum maximum (4 year old)and Pennisetum purpureum (3 year old)continue rapid growth upon subculture without a marked lag phase. They have cell doubling times of 27 h and 32 h, respectively, during the exponential phase of growth. Maximum cell numbers of 2 × 10? cells · ml-1 are reached on about the eighth day of subculture in both species. Thereafter, cell lysis and death occur progressively. By day 16, 90 percent of P. purpureum cells appear non-viable. Flow cytometry of the cell suspensions showed that at any given time during the 8-9 day culture period, a majority of the cells are in G1 phase of the cell cycle, with substantial numbers cycling through the S and G2 phases. No marked change in this distribution pattern was seen in the first 8-9 days of growth during which the cultures did not reach stationary phase. Flow cytometry, microspectrophotometry and chromosome counts showed the cultures comprised predominantly ofnormal diploid cells.