INITIATION SEQUENCE PATTERNS FOR SOMATIC EMBRYO ORIGINATING CELLS

A histological survey of the embryogenic process in Hevea brasiliensis and Coffea sp. has shown that somatic embryos may find their origin a ccording to two cell categories : embryogenic or embryonic cells. Thos e were initiated at a special time during the callus phase from merist ematic or parenchymatous cells. In friable calli of coffee capable to give numerous somatic embryos (high frequency calli), embryogenic cell s resulted from the dedifferentiation and then internal compartmentati on divisions of large highly vacuolated cells containing numerous star ch and protein reserves. When somatic embryos were of a unicellular or igin, they issued from the development of an isolated embryogenic cell . When they were of a multicellular origin, they formed either from as sociated embryogenic cells or from the evolution of a cluster of embry onic cells.