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  • Author or Editor: Ottó Toldi x
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The aim of this work was to examine the role of fructose 2,6-bisphosphate (fru 2,6P2) in the carbohydrate metabolism in carnation (Dianthus caryophyllus L.). For this purpose, transgenic plants harboring two modified bifunctional enzyme complementary DNAs of rat liver origin (6-phosphofructo-2-kinase/fructose 2,6-biphosphatase) were generated. Transformation with the kinase construct resulted in a 45% to 85% increase in fru 2,6P2 concentrations compared with the wild type. Transformation with the phosphatase construct reduced the fru 2,6P2 contents by 45% and 70%. These alterations in fru 2,6P2 amounts affected the key enzyme activities of sucrose and starch metabolism. Accordingly, plants with elevated fru 2,6P2 concentrations had high levels of starch, fructose, and triose phosphates, and low levels of sucrose, glucose, and hexose phosphates. In plants with reduced amounts of fru 2,6P2 different results could be observed in major carbohydrate compounds.

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Somatic embryos that are produced in cell and tissue culture conditions do not form endosperm and testa around the embryo. For many envisioned applications, delicate embryos need to be covered with an artificial endosperm-testa matrix that allows for respiration, contains nutrients and protectants, and is hard enough but allows the vague embryo to germinate and grow into a plant. A number of industrially produced and commonly available compounds were tested to determine their efficacy in supporting the germination of encapsulated somatic embryos of carrot (Daucus carota L.). Most of the combinations of galactomannans and polysaccharides were at least as effective as calcium alginate alone in germinating the embryos. The disappearance of blue color in Lugol staining around embryos indicates that starch might also provide nourishment to embryos, thus serving as an artificial endosperm and a supportive matrix.

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