In vitro culture and somatic embryogenesis of zygotic embryos of macaúba (Acrocomia aculeata (Jacq). Loddiges) / Cultivo in vitro e embriogênese somática de embriões zigóticos de macaúba (Acrocomia aculeata (Jacq). Loddiges)

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

The objectives of this work were to propose the proceeds regarding the culture of embryos and induction of somatic embryogenesis of the Acrocomia aculeata palm tree using as explants source the mature and immature zygotic embryos. In the in vitro embryo culture the following were studied: a) the effect of the incubation conditions and of the activated charcoal on the germination of the mature embryos; b) the effect of the medium composition, salt composition and of the activated charcoal on the germination of mature and immature zygotic embryos; and c) the effect of the storage temperature of the fruits and of the sucrose on the in vitro germination of mature and immature zygotic embryos. In relation to the induction of somatic embryogenesis, the effect of the auxin picloram in the induction of embryogenic calluses was evaluated on mature zygotic embryos. In the experiments on in vitro germination of zygotic embryos, the percentage of swelling, oxidation, germination, non reative explants, conversion to viable seedlings, plants with secondary roots, length of the aerial part and of the primary root and the average number of leaves per seedlings were evaluated. In the induction of somatic embryogenesis, the percentages of callus formation on the explants, the type of callus formed (primary or embryogenic), the percentage of nodular callus and the oxidation were evaluated. The culture of embryos under photoperiodic conditions resulted in a high index of oxidation of the explants, but this was favorable to the growth and development of the seedlings if compared to the starting darkness condition. The addition of activated charcoal to the medium showed to be essential to the complete development of the seedlings, mainly because it stimulates the development of an efficient root system, because in the absence of this component in the medium the conversion to the viable seedling was not observed, instead, the seedlings had a slow and unbalanced growth. In relation to the medium composition, in general, the MS medium promoted slightly better results than the Y3 medium, considering the seedling development in the absence of the activated charcoal. However, independent of the saline composition used, the absence of activated charcoal in the medium resulted in the unbalanced growth of the seedlings, which, in this condition, did not show the formation of primary or secondary roots. On the other hand, the addition of activated charcoal to the media promoted the conversion to viable seedlings, with well formed roots and in conditions to grow normally. The seedlings produced from immature embryos had the tendency to develop better in a medium with higher salt concentrations (75 to 100 % of the total power) of the Y3 medium. Moreover, it was observed that the primary roots had a greater length and developed more secondary roots as the concentration of activated charcoal was increased in the medium. In relation to the storage of the fruits, the environmental temperature caused the greatest percentage of germination of the embryos. The lower concentration of sucrose was the worst treatment, because, besides influencing negatively the germination of the embryos, specially those from fruits kept in low temperature, it resulted in the formation of abnormal seedlings, with symptoms of hyperhydricity. In the higher sucrose concentrations no difference was observed in the aspects of the seedlings, that showed great vigour, independently of the storage temperature of the fruits. The temperature of 35 oC stimulated the germination of immature embryos and the formation of viable seedlings, and, independent of the period of time that the fruits were kept in this condition, the physiologic quality and the viability of the explants were maintained. In addition, it rendered greater efficiency during the processing of the fruits and the extraction of the embryos. The frequency of the embryogenic calluses was greater in the medium containing 2,4 mg L-1 of picloram that also showed to be more effective in the formation of nodular structures. Hystologic sections of the nodular calluses showed the formation of pro-embryos and of somatic embryos in the globular phase, but the formation of these structures did not progress to more advanced phases when they were transferred to a maturation medium, and the calluses tended to darken completely after 30 days in this condition. The results obtained in this work allowed to conclude that it is possible to obtain seedlings of Acrocomia aculeata from the in vitro embryo culture in a relatively fast way (12 weeks). Nevertheless, complementary studies directed mainly to the curing of the seedlings should be done, because of the slow growth rate shown, which demonstrates the in vitro rooting difficulty of the species. More specific research in this direction will contribute to increase the survival rate of the seedlings in this phase and thus viabilize the application of this propagation technique to this palm species. The methodologies to improve the maturation phase and the regeneration of somatic embryos need to be adjusted, to allow the cloning in great numbers via somatic embryogenesis, because of the potential as oleaginous plant to produce biofuels.

ASSUNTO(S)

plant propagation cultivo de embriões germinação silvicultura germination in vitro propagation propagação de plantas propagação in vitro embryo culture

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