Mode of action of 2,4-D and zeatin on somatic embryogenesis in a carrot cell suspension culture

Abstract

Summary The effects of 2,4-D and zeatin added at different periods of culture on embryogenesis in a carrot (Daucus carota L. cv. «Kurodagosun») cell suspension culture were examined. Most of the single cells or cell clusters of sizes smaller than 31 μm seldom developed directly to embryos in an auxin-free medium. 2,4-D supplied prior to the embryo induction enhanced the embryo formation from the cell clusters of these sizes after transfer to the auxinfree medium. When cell clusters of size 31 to 47 μm were used as the initial material, embryogenesis was induced readily in the medium containing no growth regulators. Embryo-genesis was inhibited completely by 2,4-D added at the early period of culture, but 2,4-D was less inhibitory for embryogenesis when it was added in the late period of culture. Embryogenesis was promoted by zeatin added to the medium during days 3 and 4 of culture, while this effect was not notable when zeatin was added in the first 2 days or after 5 days of culture. The mode of action of the growth regulators on embryogenesis is discussed.