ote chn ological ▁adv ancement . ▁The ▁first ▁documentation ▁of ▁som atic ▁emb ry ogen esis ▁was ▁by ▁Ste ward ▁et ▁al . ▁in ▁ 1 9 5 8 ▁and ▁Rein ert ▁in ▁ 1 9 5 9 ▁with ▁car rot ▁cell ▁susp ension ▁cult ures . ▁ ▁Direct ▁and ▁indirect ▁emb ry ogen esis ▁Som atic ▁emb ry ogen esis ▁has ▁been ▁described ▁to ▁occur ▁in ▁two ▁ways : ▁directly ▁or ▁indirect ly . ▁ ▁Direct ▁emb ry ogen esis ▁ ▁occurs ▁when ▁emb ry os ▁are ▁started ▁directly ▁from ▁expl ant ▁t issue ▁creating ▁an ▁identical ▁clone . ▁ ▁Ind irect ▁emb ry ogen esis ▁ ▁occurs ▁when ▁expl ants ▁produced ▁und iffer enti ated , ▁or ▁partially ▁differenti ated , ▁cells ▁( o ften ▁referred ▁to ▁as ▁call us ) ▁which ▁then ▁is ▁maintained ▁or ▁differenti ated ▁into ▁plant ▁t issues ▁such ▁as ▁leaf , ▁stem , ▁or ▁roots . ▁ 2 , 4 - D ich lor oph en ox y ac etic ▁acid ▁( 2 , 4 - D ), ▁ 6 - Ben zy lam in op ur ine ▁( B AP ) ▁and ▁Gib ber el lic ▁acid ▁( GA ) ▁has ▁been ▁used ▁for ▁development ▁of ▁indirect ▁som atic ▁emb ry os ▁in ▁st raw berry ▁( F rag aria ▁an an assa ) ▁ ▁Plant ▁reg ener ation ▁by ▁som atic ▁emb ry ogen esis ▁Plant ▁reg ener ation ▁via ▁som atic ▁emb ry ogen esis ▁occurs ▁in ▁five ▁steps : ▁init iation ▁of