Somatic Embryogenesis Of Coconut (Cocos Nucifera L.) From Leaf And Inflorescence Tissue Research Findings And Prospects
Tissue culture is the only channel open for extensive vegetative propagation of coconut. For more than a decade work on somatic embryogenesis of coconut has been conducted. Although 3 teams have obtained complete regeneration of plants from somatic tissue it appears that somatic embryogenesis of coconut is not yet properly mastered. The paper reported the work done by the ORSTOM - IRHO Team since 1981 using both leaf and in florescence explants. Initial research m de it possible to solve the problem of obtaining large numbers of calli in auxin- activated charcoal media: 30-40% from to 15 to 20 years old palms. Histological studies showed that callogenesis on leaf explants was initiated in the perivascular cells of the conducting bundles whereas an inflorescence explants 2 types of calli can be formed: calli of internal origin on vascular tissue of rachis and calli on the floral primordia. After isolation of calli, embryogenic - type structures have been obtained. All the trees have given this type of embryogenic formations though yields remained low, 10% of calli at most. The subsequent development of these embryogenic - type formations poses problems. Recently, however, an embryoid was obtained from a leaf explant which gave rise to somatic embryos of which one produced a shoot and a plantlet successfully acclimatized in a phytotron . On in florescence explants a proliferation has recently been obtained on the root poles of young embryoids on an auxin-free medium - somatic embryos have been obtained, some of which have em itted a leaf sheath. The importance of such a proliferation needs to be emphasized as embryoid multiplication should enable the mass production of ramets even if the production of embryogenic structures is initally limited. In view of these encouraging results trials are being stepped up. Histochemical studies and in vitro quantitative analysis of exogenic hormones are being developed.