▁in ▁the ▁development ▁of ▁emb ry os , ▁i . e . ▁ordinary ▁plant ▁t issue . ▁No ▁end os perm ▁or ▁seed ▁coat ▁is ▁formed ▁around ▁a ▁som atic ▁emb ry o . ▁▁ ▁C ells ▁derived ▁from ▁compet ent ▁source ▁t issue ▁are ▁cult ured ▁to ▁form ▁an ▁und iffer enti ated ▁mass ▁of ▁cells ▁called ▁a ▁call us . ▁Plant ▁growth ▁regul ators ▁in ▁the ▁t issue ▁culture ▁medium ▁can ▁be ▁manip ulated ▁to ▁indu ce ▁call us ▁formation ▁and ▁subsequently ▁changed ▁to ▁indu ce ▁emb ry os ▁to ▁form ▁the ▁call us . ▁The ▁ratio ▁of ▁different ▁plant ▁growth ▁regul ators ▁required ▁to ▁indu ce ▁call us ▁or ▁emb ry o ▁formation ▁var ies ▁with ▁the ▁type ▁of ▁plant . ▁Som atic ▁emb ry os ▁are ▁mainly ▁produced ▁in ▁vit ro ▁and ▁for ▁labor atory ▁purposes , ▁using ▁either ▁solid ▁or ▁liquid ▁nut ri ent ▁media ▁which ▁contain ▁plant ▁growth ▁regul ators ▁( P GR ’ s ). ▁The ▁main ▁P GR s ▁used ▁are ▁aux ins ▁but ▁can ▁contain ▁cy to kin in ▁in ▁a ▁smaller ▁amount . ▁Sho ots ▁and ▁roots ▁are ▁mon op olar ▁while ▁som atic ▁emb ry os ▁are ▁b ip olar , ▁allowing ▁them ▁to ▁form ▁a ▁whole ▁plant ▁without ▁cult uring ▁on ▁multiple ▁media ▁types . ▁Som atic ▁emb ry ogen esis ▁has ▁served ▁as ▁a ▁model ▁to ▁understand ▁the ▁phys i ological ▁and ▁bio chem ical ▁events ▁that ▁occur ▁during ▁plant ▁development al ▁processes ▁as ▁well ▁as ▁a ▁component ▁to ▁bi