Controlling vitrification of petunia in vitro

Summary Nodal segments from in vitro culturedPetunia hybrida were grown under varying cultural conditions. The origin of nodal explants influenced vitrification. Basal segments formed a higher percentage of vitreous shoots than did the upper nodes. A method was developed for including polyethylene glycol with Gelrite to obtain gelled media of varying water potentials. Media water potential from −0.31 to −1.2 MPa had no effect on controlling the level of vitrification. Gelrite promoted vitrification but GIBCO agar, alone or in combination with Gelrite, reduced its occurrence. Lowering media NH₄ content reduced vitrification, whereas sealing culture vessels with parafilm increased it. As it is now possible to control normal and vitreous plant development inPetunia, this can be used as a model system for studying the physiology and biochemistry of this developmental abnormality.