“PLANT CELL DEDIFFERENTIATION has been mostly studied in protoplast systems. In such experimental systems dedifferentiation can be resolved into acquisition of competence for pluripotentiality and signal-dependent re-entry into S phase, each phase being accompanied by a broad chromatin decondensation. For reactivation of the cell cycle it is usually necessary that plant growth regulators are applied, but this occurs independently from the acquisition of competence for pluripotentiality.”
http://jxb.oxfordjournals.org/content/62/11/3713.full