Browsing by Author "Valerie Hocher"

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    Developmental changes in carboxylase activities in in vitro cultured coconut zygotic embryos: comparison with corresponding activities in seedlings
    (1997) Karine Triques; Alain Rival; Thierry Beule; Stephane Dussert; Valerie Hocher; Jean Luc Verdeil; Serge Hamon
    Phosphoenolpyruvate Carboxylase (PEPC; EC: 4.1.1.31) and Ribulose 1,5-bisphosphate Carboxylase / Oxygenase (RubisCO; EC: 4.1.1.39) enzyme specific activities were measured during the in vitro development of coconut (Cocos nucifera L.) zygotic mature embryos into plantlets and compared with those of palms produced by conventional seed germination. At the time of initiation of germination, high PEPC and low RubisCO activities were measured in both cultured and conventionally germinated embryos, thus indicating an anaplerotic CO2 fixation. During both in vitro and in planta development, RubisCO progressively took over and became the main route for inorganic carbon fixation. The in vitro-grown coconut plantlets showed a faster decrease in their PEPC:RubisCO ratio than the seedlings, suggesting that an earlier transition from a heterotrophic to an autotrophic mode of carbon fixation takes place in the in vitro-derived material. Just before acclimatization, the RubisCO activity in in vitro-derived plantlets (2.83 mol CO2h-1mg-1 TSP) was lower than that in seedlings (6.98 mol CO2h-1mg-1 TSP) of the same age. Nevertheless, after acclimatization, RubisCO activities were comparable in both in vitro and in planta germinated material
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    Unfertilized Ovary: A Novel Explant for Coconut (cocos Nucifera L.) Somatic Embryogenesis
    (Springer-Verlag, 2007-01) Prasanthi I.P. Perera; Valerie Hocher; Jean Luc Verdeil; Sylvie Doulbeau; Deepthi M.D. Yakandawala; Kaushalya Weerakoon, L.
    Unfertilized ovaries isolated from immature female flowers of coconut (Cocos nucifera L.) were tested as a source of explants for callogenesis and somatic embryogenesis. The correct developmental stage of ovary explants and suitable in vitro culture conditions for consistent callus production were identified. The concentration of 2,4-dichlorophenoxyacetic acid (2,4-D) and activated charcoal was found to be critical for callogenesis. When cultured in a medium containing 100 µM 2,4-D and 0.1% activated charcoal, ovary explants gave rise to 41% callusing. Embryogenic calli were sub-cultured into somatic embryogenesis induction medium containing 5 µM abscisic acid, followed by plant regeneration medium (with 5 µM 6-benzylaminopurine). Many of the somatic embryos formed were complete with shoot and root poles and upon germination they gave rise to normal shoots. However, some abnormal developments were also observed. Flow cytometric analysis revealed that all the calli tested were diploid. Through histological studies, it was possible to study the sequence of the events that take place during somatic embryogenesis including orientation, polarization and elongation of the embryos.