Teruaki Shimazu

Relationship between production of carrot somatic embryos and dissolved oxygen concentration in liquid culture

To evaluate the relationship between somatic embryogenesis and dissolved oxygen concentration, somatic embryo cultures of carrot (Daucus carota L.) were cultured under various dissolved oxygen concentration levels (bubble free aeration with 4%, 7%, 20%, 30%, and 40% oxygen in flasks). The system used allows dissolved oxygen concentration control without bubble aeration or mixing speed modification. The total number of somatic embryos was not affected by the dissolved oxygen (DO) concentration tested. Even if globular-stage embryos were induced at a low level of oxygen aeration, heart-stage embryo formation was still repressed. Oxygen enrichment (20%, 30% and 40% oxygen) enhanced torpedo and cotyledonary-stage embryo production. The oxygen-enriched aeration was effective in promoting the growth of the late developmental stages. Sugar consumption did not increase when the oxygen concentration was enriched above the ambient level. The number of heart-stage embryos increased as oxygen concentration increased up to the 7% level, while above the 20% level no change in production was observed. The production of cotyledonary-stage embryos was directly related to oxygen concentration. These results support that oxygen-enriched aeration provides oxygen to the low oxygen areas in somatic embryo. After the heat-stage embryos, which were grown at the 7% level were transferred to a flask with ambient, they developed an elongated root part and eventually grew to normal plantlets.