Induction of somatic embryos, adventitious shoots and roots in hypocotyltissue of Euphorbia pulcherrima willd, ex klotzsch: Comparative studies onembryogenic and organogenic competence

摘要

The embryogenic and organogenic competence of isolated hypocotyl tissues and entire hypocotyl discs of E. pulcherrima somatic embryos was investigated. Slowly growing, but highly regenerative callus from epidermis and outer cortex cells (O-callus) always produced somatic embryos when cultivated on auxin-containing media (induction phase) and on auxin-free media (realisation phase). In contrast, fast growing callus from pith tissue (P-callus) never regenerated any embryos, adventitious shoots or roots. Callus from entire hypocotyl discs (H-callus) gave rise to somatic embryos from epidermal and subepidermals cells only. Most of these embryos did not produce torpedo stage embryos due to recallusing of the root pole and excessive secondary callus growth. Interactions between P-callus and O-callus developing on the same explant obviously disturbed the embryogenic processes.