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Embryogenesis is a critical stage of the sporophytic life cycle, during which the basic body plan of the plant is established. Although zygotic embryogenesis is induced by fusion of the sperm and egg nuclei, plant cells can initiate embryo development without fertilization. For example, cultured somatic and male gametic cells can be induced to undergo somatic and microspore embryogenesis, respectively. Embryogenesis in vitro represents a powerful tool to manipulate plant development. After characterizing in situ embryo development in flax, we followed the cytological, morphological and some biochemical features of zygotic embryo development in embryo cultures. We also induced direct and indirect somatic and gametic embryo formation in flax. There is a strong indication that somatic and gametic embryogenesis is a stress response and that it is a way the plant cell realizes its survival strategy under completely changed and unusual conditions.
The objectives of our studies were to investigate the effect of cold pre-treatment duration and the effect of two different culture media (YP and N6) on maize anther culture response in two maize genotypes (A 18 and A 19) and to identify the gametic origin of the maize regenerants. Androgenic induction and callus formation was compared in anther cultures following pre-treatment applied to both media tested and with both maize genotypes. Higher plant regeneration was observed in case of YP media independently of the genotype used. The best results were achieved when 12 days (genotype A 18) or 14 days (in case of genotype A 19) cold pre-treatment at 10C was applied. We have tested the possibility of using enzyme isoform analyses to identify the microspore origin of calli and plants derived from anther cultures. The 11 enzymes tested in our experiments were acid phosphatase, alcohol dehydrogenase, catalase, diaphorase, β-glucosidase, glutamate oxaloacetate transaminase, isocitrate dehydrogenase, malate dehydrogenase, 6-phosphogluconate dehydrogenase, phosphoglucomutase and phosphoglucoisomerase. Analysis of malate dehydrogenase proved the gametic origin of the calli initiated and of the DH plants regenerated from anther culture, when the coleoptile of the donor plant material showed two forms of enzyme 3/6 and the analysed calli showed only one of the two forms (3 or 6).
The article focuses on several aspects of flax embryo development in situ and in vitro. It describes the ultrastructural (plastid development), cytological and morphological events during zygotic embryo development and also some biochemical changes during the process, such as hormone level, accumulation of reserve materials, pigment quality and quantity, total protein analysis, and isozyme analysis. Next it characterizes the development of the zygotic embryo excised in different developmental stages and completing its development in vitro. Finally it follows the induction of direct and indirect somatic embryo formation in flax and the induction and formation of the androgenic embryo in anther cultures.
Anther culture is currently the most successful method for production of doubled haploid lines in flax. Recently, ovary culture was also described as a good source of doubled haploids. In this contribution we investigated the incorporation of enzyme polymorphism of acid phosphatase and peroxidase as molecular markers for the gametic origin of flax plants derived from anther and ovary cultures.
Artificial hybridization experiments revealed a relatively high degree of crossability between Pinus sylvestris and P. mugo, ranging between 0.15 and 0.98. Differences between P. sylvestris x P. mugo and reciprocal hybrids of the species were observed. Hybrid seeds of P. sylvestris x P. mugo shared higher germination potential than seeds from selling, controlled intraspecific crossing, and open pollination. The corresponding value in reciprocal combination was slightly lower. The hybrid nature of the seeds obtained was shown by restriction analysis of chloroplast DNA (cp DNA) using the trnV-trnH/Hinf I primer-enzyme combination.
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