The isolation and cultivation of protoplasts from cell suspensions of a pantothenate-requiring auxotroph of Datura
Protoplasts isolated from Datura cells requiring pantothenate for growth (Pn1 cell line) failed to divide in a medium containing 0.5 M mannitol if the cells from which they were derived had been subcultured in liquid medium more than four times. Division could be reinduced either by increasing the concentration of 2,4-dichlorophenoxyacetic acid (2,4-D) in the growth medium from 1 to 2.5–5 mg/L, by adding low concentrations (0.01 – 1 mg/L) of benzyladenine to a growth medium containing 1 mg/L of 2,4-D, or by diluting the 0.5 M mannitol in the medium to 0.2 M immediately after isolation of the protoplasts. Thus, the physiological state of Pn1 cells seems to change significantly after only a few passages in liquid medium. These changes can be prevented or partially reversed by manipulating the medium in which the cells and protoplasts are cultured. Similar physiological changes did not occur in the case of cultured wild-type (Ph4), adenine-requiring (Ad1), or isoleucine–valine-requiring (I–VI) cells of Datura.