▁emb ry ogen ic ▁cult ures , ▁pro l ifer ation ▁of ▁emb ry ogen ic ▁cult ures , ▁prem atur ation ▁of ▁som atic ▁emb ry os , ▁m atur ation ▁of ▁som atic ▁emb ry os ▁and ▁plant ▁development ▁on ▁n ons pec ific ▁media . ▁ ▁In iti ation ▁and ▁pro l ifer ation ▁occur ▁on ▁a ▁medium ▁rich ▁in ▁aux in , ▁which ▁indu ces ▁different iation ▁of ▁local ized ▁mer ist ematic ▁cells . ▁The ▁aux in ▁typically ▁used ▁is ▁ 2 , 4 - D . ▁Once ▁transferred ▁to ▁a ▁medium ▁with ▁low ▁or ▁no ▁aux in , ▁these ▁cells ▁can ▁then ▁develop ▁into ▁m ature ▁emb ry os . ▁Germ ination ▁of ▁the ▁som atic ▁emb ry o ▁can ▁only ▁occur ▁when ▁it ▁is ▁m ature ▁enough ▁to ▁have ▁functional ▁root ▁and ▁shoot ▁ap ices ▁ ▁Fact ors ▁influen cing ▁Fact ors ▁and ▁mechan isms ▁cont rolling ▁cell ▁different iation ▁in ▁som atic ▁emb ry os ▁are ▁relatively ▁ambigu ous . ▁C ertain ▁comp ounds ▁ex cret ed ▁by ▁plant ▁t issue ▁cult ures ▁and ▁found ▁in ▁culture ▁media ▁have ▁been ▁shown ▁necessary ▁to ▁coordinate ▁cell ▁division ▁and ▁morph ological ▁changes . ▁These ▁comp ounds ▁have ▁been ▁identified ▁by ▁Ch ung ▁et ▁al . ▁as ▁various ▁pol ys ac char ides , ▁am ino ▁ac ids , ▁growth ▁regul ators , ▁vit am ins , ▁low ▁mole cular ▁weight ▁comp ounds ▁and ▁pol ype pt ides . ▁Several ▁signal ing ▁mole cules ▁known ▁to ▁influence ▁or