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L'embryogenèse somatique chez le chêne pédonculé : étude histocytologique des phases de multiplication et de conversion

Abstract : This work concem multiplication and conversion phases during somatic embryogenesis at oak (Quercus robur L.). Eight cultures initiated from immature zygotic embryos and multiplied then by secondary embryogenesis under standard conditions (macro and micro mineral solutions of Muraschige and Skoog added with hydrolysat of casein 0.1 %, glucose 0.12 M and NAA 10.74 [micro]M) were used. Three types of elements (friable callus, compact callus and embryonic structures) constitute these cultures which can be classified in three distinct categories according to their composition by these three types of elements. This heterogeneity is associated with differences in sensitivity to the auxin of the multiplication medium. A strong sensitivity to the auxin stimulates a friable callogenesis. Two pathways of secondary embryogenesis, direct and indirect initiated respectively from the epidermis or cortical tissue, were described. They produce secondary embryos with variable structural organisation and capacities of development. The balance between these two pathways is influenced by the composition of growth regulators of the multiplication medium. The frequency and the intensity of the secondary embryonic responses are influenced by the degree of development of the somatic embryos which were used for the preparation of explants. The maintenance of repeated secondary embryogenesis and lack of maturation opposed to spontaneous conversion of somatic embryos. The use of a maturation medium containing 6 % of sucrose permitted to the somatic embryos to acquire some characteristics of the mature zygotic embryos (starch reserves accumulation and histocytological organisation of the shoot meristem) and to thus reach up to 47 % of normal germination evolving in viable seedlings. Only young somatic embryos resulting from the multiplication on medium without growth regulators react favourably to the maturation treatment.
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Submitted on : Thursday, March 29, 2018 - 10:46:07 AM
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  • HAL Id : tel-01746851, version 1



Redouane Zegzouti. L'embryogenèse somatique chez le chêne pédonculé : étude histocytologique des phases de multiplication et de conversion. Sciences agricoles. Université Henri Poincaré - Nancy 1, 2000. Français. ⟨NNT : 2000NAN10235⟩. ⟨tel-01746851⟩



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