The level of auxin - both natural and synthetic - in the medium has a strong effect on the level of 5-methyl-cytosine in the DNA of carrot cells in culture. This level may vary from approximately 15% to 70% of total cytosine without apparent effects on growth rate and cell morphology. No effect was seen with cytokinin. During somatic embryogenesis, in the absence of hormones, variations were seen in the level of methylation according to a characteristic pattern. If hypomethylation is induced with drugs such as azacytidine, ethionine or ethoxy-carbonyl-pyrimidine, embryogenesis is immediately blocked. A mutant was isolated which is resistant to the action of hypomethylating drugs. It shows variations in the methylation pattern and variations in indole-acetic acid metabolism. In addition its regeneration is often associated with the production of tumors.

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The process of carrot (Daucus carota L.) somatic embryogenesis is highly sensitive to exogenously added ethanol, since 5 mM ethanol inhibits this process by 50%, whereas the growth of proliferating carrot cells is inhibited to the same extent by 20 mM ethanol. This is consistent with the fact that proliferating cultures produce ethanol and release it into the medium at concentrations up to 20 mM, whereas embryogenic culture medium contains less than 1 mM ethanol. Data are presented showing the influence of cell density and 2,4-dichlorophenoxyacetic acid on ethanol production and on the presence of an alcohol-dehydrogenase (EC 1.1.1.1.) inactivator in carrot embryos.

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