Immature inflorescences of coconut belonging to three different genotypes were cultured on a solid medium supplemented with activated charcoal (2%) and a range of 2,4-dichlorophenoxyacetic acid (2,4-D) concentrations (from 1.5 to 3.5 × 10(-4)M). Globular white callus formed from immature floral meristems, depending on inflorescence age and 2,4-D concentration. Acquisition of embryogenic competence is described histologically. Somatic embryos presented a functional bipolar organization with a completely differentiated shoot meristem which is reported here for the first time in coconut tissue culture. Embryo maturation allowed reliable plant regeneration of this in vitro recalcitrant species. Details are given of exogenous hormonal requirements for the acquisition of embryogenic competence and embryo maturation.
Requ le 28 janvier 1991 BUFFARD-MOREL, J., VERDEIL, J.-L., et PANNETIER, C. 1992. Embryogenbse somatique du cocotier (Cocos nucifera L.) a partir d'explants foliaires : Ctude histologique. Can. J. Bot. 70 : 735-741. Une Ctude histologique a Ct C rCaliste aux diffkrentes Ctapes de l'embryogenbse somatique du cocotier (Cocos nucifera L.) i partir d'explants foliaires. Elle a permis de localiser les premibres divisions cellulaires au niveau des cellules pCrivasculaires des explants. La croissance des cals nodulaires obtenus est assurCe par la mise en place d'une assise mCristCmatique a fonctionnement de type cambial. La nature racinaire de certaines formations a t t t observCe. Des structures embryogbnes peuvent apparaitre sur les cals nodulaires; entibrement mCristCmatiques au depart, elles ~'Cpidermisent et se multiplient pour la plupart. Leur Cvolution peut conduire i des structures de type embryon aprks fragmentation et contagion mitotique au niveau de l'assise de type cambial. Ce schema general d'obtention de structures embryonnaires peut cependant varier : (i) Soit il y a obtention rapide d'embryons a partir des cals nodulaires primaires. Cette voie a permis la rCgCntration, par embryogenbse secondaire, d'un massif d'embryons (bourgeonnement au p61e racinaire). L'un d'entre eux a dCveloppC une pousse feuillCe et des racines. La plante rCgCnCrCe a Ct C transfCrCe en champ. (i) Soit il y a formation de cals granuleux secondaires et production de f a~o n plus systtmatique de structures embryogbnes. Ces derniers devraient permettre une meilleure maitrise du dCveloppement des structures embryonnaires. Mots c l b : Cocos nucifera L., histologie, embryogenbse somatique, explants foliaires. BUFFARD-MOREL, J., VERDEIL, J.-L., and PANNETIER, C. 1992. Embryogenkse somatique du cocotier (Cocos rz~rcifera L.) a partir d'explants foliaires : Ctude histologique. Can. J. Bot. 70: 735 -74 1.Histological studies were carried out at different stages of somatic embryogenesis of coconut (Cocos nucifera L.) from leaf explants. The primary formations resulted from mitotic divisions of perivascular cells. Differentiation of a cambium-like layer insured the growth of nodular calluses. The root origin of some formations was observed. Embryogenic structures appeared on some nodular calluses maintained in culture; initially they were highly meristematic and often developed an epidermis and divided. Then embryo-like formations could be obtained after fragmentation of the cambium-like layer producing meristematic areas. However, modifications of this scheme could be observed: ( i ) Embryos rapidly developed from a primary callus, and from these embryos, a secondary embryogenesis was induced leading, at the root pole, to a clump of somatic embryos. One of the latter developed a shoot and roots; the regenerated plant was then transferred to the field. (ii) Secondary granulous calluses producing larger quantities of embryogenic structures were formed. This material should prove useful for mastering the technique of developing embryogenic stru...
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