Structural aspects of the zygotic embryogenesis of Acca sellowiana (O. Berg) Burret (Myrtaceae)

(Structural aspects of the zygotic embryogenesis of Acca sellowiana (O. Berg) Burret (Myrtaceae)). Acca sellowiana has anatropous, bitegmic and crassinucellate ovules. The outer and inner integuments are double-layered except in the micropyle, where they are composed of more layers; the micropyle is zig-zag shaped. The egg apparatus lies at the micropylar pole, and the zynergids present a conspicuous filiform apparatus. The antipodal cells are present in the chalazal region, persisting before the occurrence of double fertilization. The zygote is visible 21 days after pollination; nuclear endosperm is already present. The first mitotic division of the zygote occurs at 24(th) day. The globular, cordiform and torpedo embryo stages can be seen at 30, 45 and 60 days after pollination, respectively. The mature embryo characterized by the presence of a well-developed hypocotyl-radicular axis with two fleshy and folded cotyledons was observed 120 days after pollination. Endosperm is absent in the seeds, and the embryo has spiral form, characteristic of Myrtinae. The zygotic embryology studies of A. sellowiana indicate that this species has embryological characteristics which are in agreement with those reported for Myrtaceae (Myrteae, Myrtinae), and also broaden the knowledge about the sexual reproduction of this native species, whose commercial cultivation has been growing

Regulação da embriogênese semática in vitro com ênfase do papel de hormonios endógenos

Different aspects of the in vitro somatic embryogenesis regulation are reviewed in this paper.work. A description of g General aspects, such as terminology, uses, stages of development and factors associated with the somatic embryogenesis, are described. is carried out. Although a brief description ofn the effects of the addition of different plant growth regulators to the culture medium wasis given, the article is centereds itself on the effect that the endogenous hormone concentrations in the initial explants and in the tissue cultures derived from them could play oin the induction and expression of somatic embryogenesis. It is significant that few to emphasize the low amount of systematic studies have been conducted, in this subject, in which different species and hormone groups were compared in cultures with and without embryogenic capacity. Moreover, the lack of correlation between the results presented in different studies the distinct works indicates that the hormone content of the cultures is not the only factor involved.Neste trabalho se faz uma revisão de diversos aspectos da regulação da embriogêneses somático in vitro. Vários aspectos gerais a este fenômeno tem sido discutidos, tais como a definição de terminologia, descrição de eventuais aplicações, seus estados de desenvolvimento e outros fatores associados com sua indução e expressão. Embora se faça uma breve descrição do efeito da adição de diferentes reguladores de crescimento ao meio de cultivo, o artigo está centrado no efeito que as concentrações hormonais endogênas nos explantes iniciais e nos cultivos in vitro derivados deles podem ter na indução e expressão da embriogênese somática. Tem de se fazer ênfase na pouca quantidade de estudos sistemáticos realizados neste tema que comparem em várias espécies e diferentes grupos hormonais em cultivos com e sem competência embriogênica. Finalmente, indica-se que a falta de correlação entre os resultados destes poucos trabalhos parece indicar que os conteúdos hormonais endôgenos não são os únicos fatores envolvidos neste fenômeno.Grman Academic Exchange Service//DAAD/AlemaniaUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Agroalimentarias::Centro para Investigaciones en Granos y Semillas (CIGRAS

Involvement of Plant Hormones and Plant Growth Regulators on in vitro Somatic Embryogenesis

In spite of the importance attained by somatic embryogenesis and of the many studies that have been conducted on this developmental process, there are still many aspects that are not fully understood. Among those features, the involvement of plant hormones and plant growth regulators on deTermining the conversion of somatic onto embryogenic tissues, and on allowing progression and maturation of somatic embryos, are far away from being completely comprehended. Part of these difficulties relies on the frequent appearance of contradictory results when studying the effect of a particular stimulus over a specific stage in somatic embryogenesis. Recent progress achieved on understanding the interaction between exogenously added plant growth regulators over the concentration of endogenous hormones, together with the involvement of sensitivity of the tissues to particular hormone groups, might help clarifying the occurrence of divergent patterns in somatic embryogenesis, and in tissue culture in general. The aspects described above, emphasizing on the effect of the concentration of plant hormones and of the addition of plant growth regulators during the different phases of somatic embryogenesis, will be reviewed in this paper. Citations will be limited to review articles as much as possible and to individual articles only in those cases in which very specific or recent information is presented.UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Agroalimentarias::Centro para Investigaciones en Granos y Semillas (CIGRAS