This paper seeks to clarify conflicting reports on the nitrogen requirements for in vitro embryogenesis in Dauciis carota.Tissue derived from petiole explants of the wild strain of this species were tested with a variety of sources of cellular nitrogen under conditions otherwise favorable for in vitro embryogenesis. The use of very small, sieved and well-washed inocula reduced the carry-over of soluble materials with the inoculum. Embryo yield was quantified by direct counting of samples.Nitrate at concentrations ranging from 5 to 95 mM KNO3 supports only weak growth and very low embryogenesis under the exacting conditions of these experiments. As little as 0.1 raM NH4CI added to a nitrate medium allows some embryogenesis and 10 mM NH4CI is near optimal when KNO3 is in the range of 12 to 40 mM concentration. Glutamine, glutamic acid, urea and alanine can individually partially replace NH4CI as a supplement to KNO3. Glutamine, alanine, and possibly glutamic acid can serve as sole sources of nitrogen supporting both good growth and embryogenesis. It was concluded that a reduced nitrogen source is required, at least as a supplement to nitrate, for rapid growth and for in vitro embryogenesis of cultured wild carrot tissue. The relationship of pH of the culture medium to growth and embryogenesis was explored and optima observed at approximately pH 5.4 for both processes.

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Adventive embryogenesis in vitro-grown somatic ceils ofDaucus carota L. was increased three-fold by a 45 rain plasmolysis pre-treatment using 1M sucrose solutions. A high degree of synchronous development also resulted from this treatment. The enhancement of embryogenesis is interpreted as an increase in the regeneration of cells which have become physiologically somewhat isolated from the tissue of their origin by the plasmolysis-caused rupture of plasmodesmata. Possible causes of the increased synchrony are discussed.